Magnetic Therapy and Migraine Headache; a pulsed
electromagnetic field (PEMF) therapy and repetitive transcranial
magnetic stimulation (rTMS/TMS)research bibliography.
Pulsed magnetic fields beneficially affect migraine's
abnormal brain electrophysiology, which is present to one extent or
another in headache syndromes of all types.
Extensive research suggests there are electrophysiological
abnormalities that coexist with
many different types of neurological disease states which can be
positively affected by pulsed magnetic therapy including;
Alzheimer's,
epilepsy, Parkinson's, cluster and other headache syndromes, severe PMS
and other exaggerated menstrual related symptoms, insomnia and other
sleeping disorders, attention deficit disorder ADD, attention deficit
hyperactivity disorder ADHD, depression, schizophrenia and other
psychological disorders.
Pulsed magnetic field research suggests that pulsed
electromagnetic field therapy can reduce migraine as well as promote
sleep and relaxation in insomniacs. Transcranial magnetic
stimulation (TMS/rTMS) research has proven for decades that pulsed
electromagnetic fields safely reduce anxiety and depression using
magnetic fields that are hundreds, even thousands of times the magnetic
field density used to produce deep, restful sleep and improved sense of
wellbeing induced through EarthPulse™ magnetic field supplementation.
Over 90% of EarthPulse™ clients report better
sleep and recovery (due in part to their better sleep) simply by
sleeping within our very subtle, proprietary and patented pulsed
magnetic field. Curious side effects are enhanced wellbeing,
substantially
enhanced recovery, strength, stamina, hand-eye, balance and motor
synchronization.
Published research suggests that human
disorders of many types are related by electromagnetic anomalies in the
brain and body. The application of pulsed electromagnetic fields of
particular frequency and field density seem to be able to safely
address the problem, at least in significant part.
Several hundred
pulsed electromagnetic field therapy citations contained in our
research bibliographies are linked directly to PubMed a
service of the U.S. National Library of Medicine and the U.S. National
Institutes of Health.
These studies are offered for
your education only and are not intended as
promotional material for EarthPulse™ Technologies, LLC.
See also; Sandyk
R, Anninos
PA , Jacobson JI;
three pioneers of electromagnetic field therapy to treat Parkinson's,
Alzheimer's and epilepsy.
PEMF Background:
Research
Bibliographies:
EarthPulse research:
-
1: Cereb Cortex.
2008 Mar 27. [Epub ahead of print]
Homeostatic Metaplasticity of the Motor Cortex
is Altered during Headache-Free Intervals in Migraine with Aura.
Antal
A, Lang
N, Boros
K, Nitsche
M, Siebner
HR, Paulus
W.
Department of Clinical Neurophysiology, Georg-August University, 37073
Göttingen, Germany.
Preconditioning
of the human primary motor cortex (M1) with transcranial direct current
stimulation (tDCS) can shape the magnitude and direction of
excitability changes induced by a subsequent session of repetitive
transcranial magnetic stimulation (rTMS). Here, we examined this form
of metaplasticity in migraine patients with visual aura and healthy
controls. In both groups, facilitatory preconditioning of left M1 with
anodal tDCS increased the mean amplitudes of motor-evoked potentials
(MEPs) elicited in the contralateral hand, whereas inhibitory
preconditioning with cathodal tDCS produced a decrease in amplitude.
Following cathodal tDCS, a short train of low-intensity 5-Hz rTMS
antagonized the suppression of the mean MEP amplitude in both groups.
In contrast, the homeostatic effects of 5-Hz rTMS differed between
groups when rTMS was given after anodal tDCS. In controls 5-Hz rTMS
induced a marked decrease in MEP amplitudes, whereas in migraineurs
rTMS induced only a modest decrease in MEP amplitudes, which were still
facilitated after rTMS when compared with baseline amplitudes. These
findings indicate that short-term homeostatic plasticity is altered in
patients with visual aura between the attacks.
PMID: 18372292 [PubMed - as supplied by publisher]
-
The clinical diagnostic utility of transcranial
magnetic stimulation: report of an IFCN committee.
Chen
R, Cros
D, Curra
A, Di
Lazzaro V, Lefaucheur
JP, Magistris
MR, Mills
K, Rösler
KM, Triggs
WJ, Ugawa
Y, Ziemann
U.
Division
of Neurology, Toronto Western Research Institute, University of
Toronto, 7MC411, Toronto Western Hospital, 399 Bathurst Street,
Toronto, Ont., Canada M5T 2S8. robert.chen@uhn.on.ca
The review
focuses on the clinical diagnostic utility of transcranial magnetic
stimulation (TMS). The central motor conduction time (CMCT) is a
sensitive method to detect myelopathy and abnormalities may be detected
in the absence of radiological changes. CMCT may also detect upper
motor neuron involvement in amyotrophic lateral sclerosis. The
diagnostic sensitivity may be increased by using the triple stimulation
technique (TST), by combining several parameters such as CMCT, motor
threshold and silent period, or by studying multiple muscles. In
peripheral facial nerve palsies, TMS may be used to localize the site
of nerve dysfunction and clarify the etiology. TMS measures also have
high sensitivity in detecting lesions in multiple sclerosis and
abnormalities in CMCT or TST may correlate with motor impairment and
disability. Cerebellar stimulation may detect lesions in the cerebellum
or the cerebellar output pathway. TMS may detect upper motor neuron
involvement in patients with atypical parkinsonism and equivocal signs.
The ipsilateral silent period that measures transcallosal inhibition is
a potential method to distinguish between different parkinsonian
syndromes. Short latency afferent inhibition (SAI), which is related to
central cholinergic transmission, is reduced in Alzheimer's disease.
Changes in SAI following administration of cholinesterase inhibitor may
be related to the long-term efficacy of this treatment. The results of
MEP measurement in the first week after stroke correlate with
functional outcome. We conclude that TMS measures have demonstrated
diagnostic utility in myelopathy, amyotrophic lateral sclerosis and
multiple sclerosis. TMS measures have potential clinical utility in
cerebellar disease, dementia, facial nerve disorders, movement
disorders, stroke, epilepsy, migraine and chronic pain.
Publication Types:
PMID: 18063409 [PubMed - indexed for MEDLINE]
-
[Cortical dysbalance in the brain in
migraineurs--hyperexcitability as the result of sensitisation?]
[Article in German]
Stankewitz
A, May
A.
Institut
für systemische Neurowissenschaften, Universitätsklinikum
Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
A
cortical dysbalance has a pivotal role in the pathophysiology of
migraine. Numerous electrophysiological and transcranial magnetic
stimulation (TMS) studies have investigated the interictal excitability
level in migraineurs and have shown a consistent lack of habituation
during repetitive stimulation. There is some controversy in the current
literature over whether this deficit is based on a lowered or an
elevated preactivation level. However, the current discussion may be
misguided. It seems that multiple external and intrinsic factors
influence the level of cortical excitability and the frequency and
intensity of attacks: Habituation is specific neither to migraine nor
even to pain; the same phenomenon is found in tinnitus patients, for
example. Cortical hyperexcitability is presumably the result of
chronicity and the concomitant central sensitisation process.
Publication Types:
PMID: 18228046 [PubMed - indexed for MEDLINE]
-
-
Clinical correlates of phosphene perception in
migraine without aura: an Asian study.
Lo
YL, Lum
SY, Fook-Chong
S, Cui
SL, Siow
HC.
Department
of Neurology, National Neuroscience Institute, Singapore General
Hospital, Outram Road, Singapore 169608, Singapore.
lo.yew.long@sgh.com.sg
INTRODUCTION: Although controversy exists
with regard to the presence of hypoexcitability versus
hyperexcitability of the visual cortex in migraine patients, there
remain a group who do not perceive phosphenes (P-). However, its
clinical implications have not been systematically addressed. In this
study, we hypothesize that P- patients classified as migraine without
aura (MO) have distinct clinical features. METHODS: Twenty-nine Asian
MO patients (7 men; mean age: 44; median: 45; range: 25 to 65) were
consecutively entered into the study. Visual cortex transcranial
magnetic stimulation (TMS) was performed in the migraine interictum.
RESULTS: Of the 19 patients, 19 (66%) were able to perceive phosphenes
(P+), while 10 (34%) were not able to after repeated TMS (P-). P-
patients had significantly higher headache frequency (p=0.008) and pain
score (p=0.002) compared with P+ patients. In addition, there was
significant positive correlation of phosphene threshold with pain score
(r=0.52, p=0.02) in P+ patients. There was no significant difference
between P+ and P- patients in terms of age (t-test, p=0.6).
CONCLUSIONS: Our study is inkeeping with the hypothesis that interictal
visual cortex excitability is reduced in relation to the severity of
migraine in Asian MO patients, and lack of phosphene perception may be
related to significantly elevated thresholds beyond the output of TMS
stimulators.
PMID: 17720202 [PubMed - indexed for MEDLINE]
-
Comment in:
Unexpected reduction in migraine and psychogenic
headaches following rTMS treatment for major depression: a report of
two cases.
O'Reardon
JP, Fontecha
JF, Cristancho
MA, Newman
S.
University of Pennsylvania, Transcranial Magnetic Stimulation
Laboratory, Philadelphia, PA, USA. oreardon@mail.med.upenn.edu
Our
objective is to report a coincident reduction in headache pain in
patients treated with repetitive transcranial magnetic stimulation
(rTMS) for major depressive disorder (MDD). Two patients with a
Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition
diagnosis of MDD, non-responsive to prior antidepressant treatment who
were enrolled in a sham-controlled, double-blind study of rTMS for MDD.
After the study, it was revealed that both were in the active-treatment
arm. Both patients suffered from near daily headaches and kept logs of
headache frequency and severity before, during, and after the study.
Headache pain was significantly reduced under double-blind conditions
with rTMS treatment, but returned to baseline following cessation of
rTMS treatment. Ultimately, when receiving rTMS post-study as a
maintenance intervention for MDD (approximately 2 rTMS sessions/week),
the positive effects on headache amelioration were sustained. Headache
pain is frequently comorbid with mood disorders and has been reported
as the most common side effect with rTMS. In these subjects, rTMS was,
in fact, associated with relief of depressive symptoms and preexisting
headache pain. This indicates that rTMS may be beneficial for both
disorders in some patients.
Publication Types:
PMID: 18163038 [PubMed - indexed for MEDLINE]
-
-
Comment in:
Shortened cortical silent period in facial
muscles of patients with migraine.
Curra
A, Pierelli
F, Coppola
G, Barbanti
P, Buzzi
MG, Galeotti
F, Serrao
M, Truini
A, Casali
C, Pauri
F, Cruccu
G.
Department of Neurological Sciences, La Sapienza University, Rome,
Italy. antonio.curra@uniroma1.it
Despite
intensive neurophysiological research, evidence is lacking to show
whether abnormal cortical excitability in migraine reflects a primary
cortical disturbance or reduced control by thalamo-cortical loops. One
way to contribute to the scientific discussion on this topic is to
deliver transcranial magnetic stimulation (TMS) and test the cortical
silent period (SP) recorded in facial muscles. The facial-muscle SP is
a purely cortical phenomenon that reflects the excitability of
inhibitory interneurons, and can disclose changes in cortical
inhibition even in patients without documented primary lesions of the
motor cortices. To test the interictal excitability of cortical motor
inhibitory interneurons in migraine, we investigated the facial-SP in
patients with migraine with and without aura between attacks. In 26
patients and 15 age-matched controls, high-intensity magnetic stimuli
were delivered with a round coil centered at the vertex during a
maximal muscle contraction. Electromyographic responses were recorded
from surface electrodes placed over the subjects' perioral muscles.
Facial SPs were significantly shorter in patients than in controls. The
SP shortening provides neurophysiological evidence showing
hypoexcitability of cortical inhibitory neurons in patients with
migraine between attacks. Despite a possible primary deficit of
cortical inhibitory interneurons in migraine, we favor the
interpretation of a secondary disfacilitation by hypoactive
thalamo-cortical loops. Based on this interpretation, the interictal
reduced cortical inhibition documented by the shortened SP could be
considered the motor counterpart of the reduced preactivation
excitability level in the sensory cortices purported to explain why
cortical evoked responses habituate poorly in patients with migraine.
PMID: 17574759 [PubMed - indexed for MEDLINE]
-
[Neurophysiology of visual aura in migraine]
[Article in Japanese]
Shibata
K.
Department of Medicine, Tokyo Women's Medical University, Medical
Center East, 2-10 Nishiogu, Arakawa-ku, Tokyo 116-8567, Japan.
Visual
processing in migraine has been targeted because the visual symptoms
that are commonly associated with attack, either in the form of aura or
other more subtle symptoms, indicate that the visual pathways are
involved in migrainous pathophysiology. The visual aura of the migraine
attack has been explained by the cortical spreading depression (CSD) of
Leão, neuroelectric event beginning in the occipital cortex and
propagating into contiguous brain region. Clinical observations suggest
that hyperexcitability occurs not only during the attack, typically in
the form of photophobia, but also between attacks. Numerous human
neuroimaging, neurophysiological and psychophysical studies have
identified differences in cortical visual processing in migraine. The
possibility of imaging the typical visual aura with BOLD functional MRI
has revealed multiple neurovascular events in the occipital cortex
within a single attack that closely resemble CSD. As transient
synchronized neuronal excitation precedes CSD, changes in cortical
excitability underlie the migraine attack. Independent evidence for
altered neuronal excitability in migraineurs between attacks emerges
from visual evoked potentials (VEPs) and transcranial magnetic
stimulation (TMS), recordings of cortical potentials and psychophysics.
Recently, both TMS and psycho-physical studies measuring visual
performance in migraineurs have used measures which presumably measure
primary visual (V1) and visual association cortex. Our VEP and blink
reflex study showed that migraine patients exhibiting allodynia might
show central sensitization of braistem trigeminal neuron and had
contrast modulation dysfunction during the cortical visual processing
of V1 and visual association cortex in-between attacks. In
pathophysiology of migraine, these neurophysiological and
psychophysical studies indicate that abnormal visual and trigeminal
hyperexcitability might persist between migraine attacks. The influence
of migraine on cortical neural processing is likely to extend beyond V1
and abnormal cortical activity might lead to CSD when enhanced
activation coincides with other factors.
Publication Types:
PMID: 17886478 [PubMed - indexed for MEDLINE]
-
Transcranial direct current stimulation reveals
inhibitory deficiency in migraine.
Chadaide
Z, Arlt
S, Antal
A, Nitsche
MA, Lang
N, Paulus
W.
Department of Clinical Neurophysiology, Georg-August University,
Göttingen, Germany.
The
issue of interictal excitability of cortical neurons in migraine
patients is controversial: some studies have reported hypo-, others
hyperexcitability. The aim of the present study was to observe the
dynamics of this basic interictal state by further modulating the
excitability level of the visual cortex using transcranial direct
current stimulation (tDCS) in migraineurs with and without aura. In
healthy subjects anodal tDCS decreases, cathodal stimulation increases
transcranial magnetic stimulation (TMS)-elicited phosphene thresholds
(PT), which is suggested as a representative value of visual cortex
excitability. Compared with healthy controls, migraine patients tended
to show lower baseline PT values, but this decrease failed to reach
statistical significance. Anodal stimulation decreased phosphene
threshold in migraineurs similarly to controls, having a larger effect
in migraineurs with aura. Cathodal stimulation had no significant
effect in the patient groups. This result strengthens the notion of
deficient inhibitory processes in the cortex of migraineurs, which is
selectively revealed by activity-modulating cortical input.
Publication Types:
PMID: 17498207 [PubMed - indexed for MEDLINE]
-
-
Brainstem dysfunction in chronic migraine as
evidenced by neurophysiological and positron emission tomography
studies.
Aurora
SK, Barrodale
PM, Tipton
RL, Khodavirdi
A.
Swedish Headache Center, 1101 Madison #200, Seattle, WA 98104, USA.
BACKGROUND:
The pathophysiology of chronic migraine (CM) is not fully understood.
We aimed to examine transcranial magnetic stimulation (TMS) indices of
cortical excitability in patients with CM and also performed PET
studies to ascertain if there were any areas of activation and
inhibition for possible correlation. METHODS: Excitability of the
cortex was assessed by a reliable parameter of magnetic suppression of
perceptual accuracy (MSPA) profiles using transcranial magnetic
stimulation in 25 patients with CM. Of these 10 patients were also
studied with ((18)F-FDG PET) scans. RESULTS: MSPA demonstrated
decreased inhibition in CM compared to normal controls and episodic
migraine. The percentage of letters reported correct at 100 ms was
84.37 for CM compared to 19.14 for normal controls and 57.41 for
episodic migraine. The PET evaluation in 10 subjects demonstrated
increased cerebral metabolism in areas of in the brainstem compared to
the global flow. There were also decreased areas of cerebral metabolism
in the medial frontal and parietal as well as the somatosensory cortex.
CONCLUSIONS: Patients with CM appear to be characterized by reduced
visual suppression correlating with high cortical excitability. In a
cohort of these subjects there was brainstem activation and inhibition
in certain areas of the cortex suggesting a potential dysfunction in
the inhibitory pathways.
PMID: 17635590 [PubMed - indexed for MEDLINE]
-
-
Safety aspects of transcranial direct current
stimulation concerning healthy subjects and patients.
Poreisz
C, Boros
K, Antal
A, Paulus
W.
Department
of Clinical Neurophysiology, Georg-August University, Robert Koch
Strasse 40, 37075 Göttingen, Germany.
csaba.poreisz@med.ni-goettingen.de
Cortical
excitability changes induced by tDCS and revealed by TMS, are
increasingly being used as an index of neuronal plasticity in the human
cortex. The aim of this paper is to summarize the partially adverse
effects of 567 tDCS sessions over motor and non-motor cortical areas
(occipital, temporal, parietal) from the last 2 years, on work
performed in our laboratories. One-hundred and two of our subjects who
participated in our tDCS studies completed a questionnaire. The
questionnaire contained rating scales regarding the presence and
severity of headache, difficulties in concentrating, acute mood
changes, visual perceptual changes and any discomforting sensation like
pain, tingling, itching or burning under the electrodes, during and
after tDCS. Participants were healthy subjects (75.5%), migraine
patients (8.8%), post-stroke patients (5.9%) and tinnitus patients
(9.8%). During tDCS a mild tingling sensation was the most common
reported adverse effect (70.6%), moderate fatigue was felt by 35.3% of
the subjects, whereas a light itching sensation under the stimulation
electrodes occurred in 30.4% of cases. After tDCS headache (11.8%),
nausea (2.9%) and insomnia (0.98%) were reported, but fairly
infrequently. In addition, the incidence of the itching sensation
(p=0.02) and the intensity of tingling sensation (p=0.02) were
significantly higher during tDCS in the group of the healthy subjects,
in comparison to patients; whereas the occurrence of headache was
significantly higher in the patient group (p=0.03) after the
stimulation. Our results suggest that tDCS applied to motor and
non-motor areas according to the present tDCS safety guidelines, is
associated with relatively minor adverse effects in healthy humans and
patients with varying neurological disorders.
Publication Types:
PMID: 17452283 [PubMed - indexed for MEDLINE]
-
-
Intracortical inhibition and facilitation in
migraine--a transcranial magnetic stimulation study.
Siniatchkin
M, Kröner-Herwig
B, Kocabiyik
E, Rothenberger
A.
Department of Child Neurology, University of Kiel, Kiel, Germany.
OBJECTIVE:
Migraine is a disease of altered cortical excitability between attacks.
However, the mechanisms of abnormal excitability in migraine are
insufficiently investigated. Hence, the aim of the study was to
investigate intracortical inhibition/facilitation of the motor circuit
in migraine. METHODS: Sixteen women suffering from migraine without
aura and 15 healthy women were investigated using a suprathreshold
transcranial magnetic stimulation (TMS) in the paired-pulse paradigm
with long interstimulus intervals (ISI = 20, 60, 120 ms) and
measurement of the cortical silent period. RESULTS: We found no
differences for the cortical silent period and for the long
intracortical inhibition between the groups. Concerning intracortical
facilitation, this ability was significantly more pronounced in
patients suffering from migraine compared with healthy controls.
CONCLUSION: Migraineurs produce an increased intracortical
facilitation. The results may be discussed in line of glutamatergic
mechanisms in migraine, which could be related to altered facilitation.
Publication Types:
PMID: 17371353 [PubMed - indexed for MEDLINE]
J
Headache Pain. 2006 Oct;7(5):341-6. Epub 2006 Oct 25. Links
Transcranial magnetic stimulation for
migraine: clinical effects.
Clarke
BM, Upton AR, Kamath MV, Al-Harbi T, Castellanos CM.
Division
of Neurology, McMaster University, Hamilton, Ontario, Canada.
Acta
Neurol Belg. 2003 Sep;103(3):144-54.Links
Transcranial
magnetic stimulation in migraine: a review of facts and controversies.
Fumal A, Bohotin V, Vandenheede M, Schoenen J.
Departments of Neurology and Neuroanatomy, University of Liège,
B-4000 Liège, Belgium.
Med Hypotheses. 2002 Dec;59(6):703-5.
Cellular
telephones and effects on the brain: the head as an antenna and brain
tissue as a radio receiver.
Weinberger Z, Richter ED.
Jerusalem College of Technology, Jerusalem, Israel.
Headache and other neuropsychological symptoms occur in users of
cellular telephones, and controversy exists concerning risks for brain
cancer. We hypothesize these effects result from the head serving as an
antenna and brain tissue as a radio receiver.
Adv Ther. 2001 May-Jun;18(3):101-9.
Impulse
magnetic-field therapy for migraine and other headaches: a
double-blind, placebo-controlled study.
Pelka RB, Jaenicke C, Gruenwald J.
Universitat der Bundeswehr Munchen Munich, Germany.
Headache. 1999 Sep;39(8):567-75.
Treatment
of migraine with pulsing electromagnetic fields: a double-blind,
placebo-controlled study.
Sherman RA, Acosta NM, Robson L.
Orthopedic Surgery Service, Madigan Army Medical Center, Tacoma, WA
98431, USA.
Headache. 1998 Mar;38(3):208-13.
Initial
exploration of pulsing electromagnetic fields for treatment of migraine.
Sherman RA, Robson L, Marden LA.
Service of Orthopedic Surgery, Madigan Army Medical Center, Tacoma,
Wash. 98431, USA.
Curr Opin Neurol. 2003 Jun;16(3):327-31.
The electrophysiology of migraine.
Ambrosini A, Schoenen J.
Headache Clinic, INM Neuromed, IRCCS, Pozzilli, Isernia, Italy.
PURPOSE OF REVIEW: The pathophysiology of migraine is far from being
understood. Electrophysiological methods are useful to investigate
peripheral and central mechanisms underlying this disorder. The purpose
of this review is to highlight the results of electrophysiological
studies published during the last year and to examine their added value
to our previous knowledge. RECENT FINDINGS: Studies by visual and
auditory evoked potentials and event-related responses suggested that
lack of habituation is the principal interictal abnormality of sensory
processing in migraineurs. Recently confirmed for somatosensory and
laser-evoked cortical potentials and for brainstem responses, it is
also responsible for the increased intensity dependence of auditory
evoked potentials. This abnormality is possibly caused by a reduced
cortical preactivation level due to hypofunctioning subcortico-cortical
aminergic pathways. Although studies of cortical excitability by
transcranial magnetic stimulation have yielded conflicting results,
results obtained using habituation of pattern-reversal visual evoked
potentials to explore cortical excitability changes induced by
repetitive transcranial magnetic stimulation strongly favour the
hypothesis that migraine is characterized by a decreased level of
preactivation excitability. With regard to pain mechanisms in migraine,
electrophysiological studies of trigeminal pathways using nociceptive
blink and corneal reflexes have confirmed that sensitization of central
trigeminal nociceptors occurs during the attack, and may even persist
interictally. SUMMARY: Scientific publications over the last year
confirmed that electrophysiological methods are particularly suited to
unravelling some of the pathophysiological mechanisms of migraine. To
improve their future contribution, they need to be better standardized
and to be correlated with behavioural, metabolic and genetic studies.
PMID: 12858069 [PubMed - in process]
------------------------------------------------------------------------
2: Cephalalgia. 2003;23 Suppl 1:13-31. Related
Articles, Links
Electrophysiological studies in migraine: a comprehensive
review of their interest and limitations.
Ambrosini A, de Noordhout AM, Sandor PS, Schoenen J.
Headache Clinic, INM Neuromed, IRCCS, Pozzilli (Isernia),Italy.
Electrophysiological methods may help to unravel some of the
pathophysiological mechanisms of migraine. Lack of habituation is the
principal and most reproducible interictal abnormality in sensory
processing in migraineurs. It is found in evoked potential (EP) studies
for every stimulation modality including nociceptive stimuli, and it is
likely to be responsible for the increased intensity dependence of EP.
We have hypothesized that deficient EP habituation in migraine could be
due to a reduced preactivation level of sensory cortices because of
hypofunctioning subcortico-cortical aminergic pathways. This is not in
keeping with simple hyperexcitability of the cortex, which has been
suggested by some, but not all, studies of transcranial magnetic
stimulation (TMS). A recent study of the effects of repetitive TMS on
visual EP strongly supports the hypothesis that migraine is
characterized by interictal cortical hypoexcitability. With regard to
pain mechanisms in migraine, electrophysiological studies of trigeminal
pathways using nociceptive blink and corneal reflexes have confirmed
that sensitization of central trigeminal nociceptors occurs during
migraine attacks.
Publication Types:
* Review
* Review, Tutorial
PMID: 12699456 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
3: Clin Neurophysiol. 2003 Jun;114(6):955-72. Related
Articles, Links
Evoked potentials and transcranial magnetic stimulation in
migraine: published data and viewpoint on their pathophysiologic
significance.
Schoenen J, Ambrosini A, Sandor PS, Maertens de Noordhout A.
University Department of Neurology, CHR Citadelle, Blvd du XIIemede
Ligne, 1-B-4000, Liege, Belgium. jean.schoenen@chrcitadelle.be
Migraine is a disorder in which central nervous sytem dysfunction might
play a pivotal role. Electroneurophysiology seems thus particularly
suited to study its pathophysiology. We have extensively reviewed
evoked potential and transcranial magnetic stimulation studies
performed in migraineurs in order to identify their pathophysiologic
significance. Publications available to us were completed by a Medline
search. Retrieved and personal data were compared with respect to
methodology and interpreted according to present knowledge on cortical
information processing. Results are in part contradictory which appears
to be method-, patient- and disease- related. Nonetheless, both evoked
potential and transcranial magnetic stimulation studies demonstrate
that the cerebral cortex, and possibly subcortical structures, are
dysfunctioning interictally in both migraine with and without aura.
These electrophysiologic abnormalities tend to normalise just before
and during an attack and some of them seem to have a clear familial and
predisposing character. Besides the studies of magnetophosphenes which
have yielded contrasting results, chiefly because the method is not
sufficiently reliable, most recent electrophysiologic investigations of
cortical activities in migraine favour deficient habituation and
decreased preactivation cortical excitability as the predominant
interictal dysfunctions. We propose that the former is a consequence of
the latter and that it could favour both interictal cognitive
disturbances as well as a cerebral metabolic disequilibrium that may
play a role in migraine pathogenesis. To summarize, electrophysiologic
studies demonstrate in migraine between attacks a cortical, and
possibly subcortical, dysfunction of which the hallmark is deficient
habituation.
PMID: 12804664 [PubMed - in process]
------------------------------------------------------------------------
4: Curr Opin Neurol. 2002 Jun;15(3):303-9. Related
Articles, Links
The electrophysiology of migraine.
Giffin NJ, Kaube H.
Headache Group, Institute of Neurology, Queen Square, London WC1N 3BG,
UK.
Migraine is currently regarded as a neurovascular disorder of
trigeminal sensory processing, generated centrally, probably at the
level of the brainstem. In the past, electrophysiological techniques
have drawn no definite conclusions on either interictal or ictal
changes in migraineurs compared with controls, largely because of
methodological differences. Recently, two findings have been shown
consistently: an interictal increasing lack of habituation of evoked
potentials with a normalization at the start of the attack and strong
intensity dependence of auditory evoked potentials. These findings
substantiate migraine sufferers as having an abnormal trait
interictally, with the attack characterized by a change in the state of
central processing. Exploitation of these differences may be a useful
tool to study the mechanism of action of drugs used for the treatment
of migraine.
Publication Types:
* Review
* Review, Tutorial
PMID: 12045729 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
5: Cephalalgia. 2000 Oct;20(8):714-9. Related Articles,
Links
Habituation of visual and intensity dependence of auditory
evoked cortical potentials tends to normalize just before and during
the migraine attack.
Judit A, Sandor PS, Schoenen J.
Department of Neurology, Semmelweis University of Medicine, Budapest,
Hungary.
Between attacks, migraine with (MO) or without aura (MA) patients show
deficient habituation of pattern-reversal visual evoked potentials
(PR-VEP) and a strong intensity dependence of auditory evoked cortical
potentials (IDAP). Clinical observations of migraine prodromes and
previously published electrophysiological studies suggest that cortical
information processing may vary in close temporal relationship to the
attack. We studied PR-VEP and IDAP just before (11 MO pts), during (23
MO, 3 MA), 1 day following (27 MO, 1 MA) and 2 days following (14 MO) a
migraine attack. The results were compared with a large group of MO
patients recorded at a distance of at least 3 days from an attack (n =
66 for IDAP; n = 39 for VEP). Patients recorded the day before the
attack had on average an habituation of -13.6+/-20.5% (mean +/- SD)
between the 5th and 1st block of 100 averaged VEP responses and a flat
(0.38+/-1.06 microV/10 dB) amplitude-stimulus intensity function (ASF)
slope of the auditory evoked cortical potential. Both values were
significantly different from those obtained in the attack interval
(P=0.003; P=0.020). During the attack, VEP habituation was less
pronounced (-0.17+/-26.2%) and ASF slopes remained flat (0.32+/-1.44
microV/10 dB; P=0.002 compared to interval). During the 2 days
following the attack, VEP habituation was replaced by potentiation
(+0.09+/-29.1% the 1st day; 19.5+/-45.7% the 2nd day) and ASF slopes
increased markedly (0.87+/-1.39 and 1.14+/-1.12 microV/10 dB). The
normalization of evoked cortical responses just before and during the
attack, might reflect an increase in the cortical preactivation level
due to enhanced activity in raphe-cortical serotonergic pathways.
PMID: 11167900 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
6: Clin Neurosci. 1998;5(1):10-7. Related Articles,
Links
Cortical electrophysiology in migraine and possible
pathogenetic implications.
Schoenen J.
Department of Neurology, University of Liege, CHR Citadelle, Liege,
Belgium. Schoenen.J@innet.be
According to recent evoked potential studies a fundamental, probably
protective, feature of cortical information processing, i.e., response
habituation during stimulus repetition, is abnormal in migraine between
attacks. The deficient habituation is found for different sensory
modalities and experimental paradigms: pattern-reversal visual evoked
potentials (same stimulus at a constant intensity), cortical auditory
evoked potentials (same stimulus at increasing intensities), and
auditory event-related potential obtained in a passive "oddball"
paradigm (novel stimulus). The abnormal information processing is an
interictal cortical dysfunction most likely due to inadequate control
by the so-called "state-setting, chemically-addressed pathways"
originating in the brain stem, in particular by the serotonergic
pathway, leading to a low preactivation level of sensory cortices. We
propose that it may play a pivotal role in migraine pathogenesis in
conjunction with the reported decrease of brain mitochondrial energy
reserve, by favouring a rupture of metabolic homeostasis and
biochemical shifts capable of activating the trigeminovascular system
and, thus, of producing a migraine attack. We postulate that both the
deficient habituation in information processing and the deranged oxygen
metabolism may have behavioral correlates. Which of these abnormalities
are inherited, acquired, or both remains to be determined.
Publication Types:
* Review
* Review, Academic
PMID: 9523052 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
7: Biomed Pharmacother. 1996;50(2):71-8. Related
Articles, Links
Deficient habituation of evoked cortical potentials in
migraine: a link between brain biology, behavior and trigeminovascular
activation?
Schoenen J.
Department of Neurology, University of Liege, Belgium.
According to recent evoked potential studies, a fundamental, probably
protective, feature of cortical information processing, ie, response
habituation during stimulus repetition, is abnormal in migraine between
attacks. The deficient habituation is found for different sensory
modalities and experimental paradigms: pattern-reversal visual evoked
potentials (same stimulus at a constant intensity), cortical auditory
evoked potentials (same stimulus at increasing intensities) and
auditory event-related potentials obtained in a passive "oddball"
paradigm (novel stimulus). The abnormal information processing is an
interictal cortical dysfunction most likely due to inadequate control
by the so-called "state-setting, chemically-addressed pathways"
originating in the brain stem, in particular by the serotonergic
pathway, leading to a low preactivation level of sensory cortices. We
suggest that it may play a pivotal role in migraine pathogenesis in
conjunction with the reported decrease of brain mitochondrial energy
reserve, by favouring a rupture of metabolic homeostasis and
biochemical shifts capable of activating the trigeminovascular system
and thus capable of producing a migraine attack. We postulate that both
the deficient habituation in information processing and the deranged
oxygen metabolism may have behavioral correlates. Which of these
abnormalities are inherited, acquired or both remains to be determined.
Publication Types:
* Review
* Review, Tutorial
PMID: 8761712 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
8: Clin Neurophysiol. 2000 Jun;111(6):1124-9. Related
Articles, Links
Comparison of visual and auditory evoked cortical potentials
in migraine patients between attacks.
Afra J, Proietti Cecchini A, Sandor PS, Schoenen J.
Department of Neurology Semmelweis University of Medicine, Budapest,
Hungary.
OBJECTIVE: As both habituation of pattern reversal visual evoked
potentials (PR-VEP) (Schoenen J, Wang W, Albert A, Delwaide PJ.
Potentiation instead of habituation characterizes visual evoked
potentials in migraine patients between attacks. Eur J Neurol
1995;2:115-122) and intensity dependence of auditory evoked cortical
potentials (IDAP) (Wang W, Timsit-Berthier M, Schoenen J. Intensity
dependence of auditory evoked potentials in migraine: an indication of
cortical potentiation and low serotonergic neurotransmission? Neurology
1996;46:1404-1409) were found abnormal in migraine between attacks, we
have searched for intraindividual correlations between both tests in 59
migraine patients (22 with aura [MA], 37 without aura [MO]) and in 23
healthy volunteers (HV). METHODS: Amplitude change of the PR-VEP N1-P1
was measured between the 1st and 5th block of 50 sequential averagings
during continuous stimulation at 3.1 Hz. IDAP was computed from N1-P2
amplitudes of 100 averagings during stimulations at 40, 50, 60 and 70
dB SL. Amplitude-stimulus intensity function (ASF) slopes and amplitude
changes between 40 and 70 dB were calculated. MO and MA differed from
HV in PR-VEP amplitude change (P=0.007) and IDAP slope (P = 0.0004).
RESULTS: There was no significant correlation between VEP amplitude
changes and IDAP slopes, nor between the latter two and attack
frequency or disease duration. A negative correlation was found between
the amplitude of the first block of averaged responses and potentiation
of VEP in all subject groups (P = 0.03) as well as between the
amplitude of the auditory evoked potential, at 40 dB, and the
percentage of amplitude increase between 40 and 70 dB in MO (P = 0.004)
and MA (P = 0.007). ASF slopes and 40 dB amplitudes were significantly
correlated only in the MA group (P = 0.002). These results confirm the
interictal deficit of habituation in cortical processing of repetitive
visual and auditory information in migraine. Since there is no
intraindividual correlation between the cortical responses to these
sensory modalities they are complementary tools for the study of
migraine and may help to identify subgroups of patients with distinct
pathophysiological mechanisms. CONCLUSIONS: The strong negative
correlation between the initial amplitude of evoked potentials and
their amplitude increase during subsequent averaging confirms that the
response potentiation in migraine is likely to be due to a reduced
preactivation level of sensory cortices.
PMID: 10825720 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
9: Brain. 2002 Apr;125(Pt 4):912-22. Related Articles,
Links
Effects of repetitive transcranial magnetic stimulation on
visual evoked potentials in migraine.
Bohotin V, Fumal A, Vandenheede M, Gerard P, Bohotin C, Maertens de
Noordhout A, Schoenen J.
Department of Neurology, University of Liege, Liege, Belgium.
Between attacks, migraine patients are characterized by potentiation
instead of habituation of stimulation-evoked cortical responses. It is
debated whether this is due to increased or decreased cortical
excitability. We have studied the changes in visual cortex excitability
by recording pattern-reversal visual evoked potentials (PR-VEP) after
low- and high-frequency repetitive transcranial magnetic stimulation
(rTMS), known respectively for their inhibitory and excitatory effect
on the cortex. In 30 patients (20 migraine without, 10 with aura) and
24 healthy volunteers, rTMS of the occipital cortex was performed with
a focal figure-of-eight magnetic coil (Magstim). Nine hundred pulses
were delivered randomly at 1 or 10 Hz in two separate sessions.
Stimulus intensity was set to the phosphene threshold or to 110% of the
motor threshold if no phosphenes were elicited. Before and after rTMS,
PR-VEP were averaged sequentially in six blocks of 100zztieresponses
during uninterrupted 3.1 Hz stimulation. In healthy volunteers, PR-VEP
amplitude was significantly decreased in the first block after 1 Hz
rTMS and the habituation normally found in successive blocks after
sustained stimulation was significantly attenuated. In migraine
patients, 10 Hz rTMS was followed by a significant increase of first
block PR-VEP amplitude and by a reversal to normal habituation of the
potentiation (or dishabituation) characteristic of the disorder. This
effect was similar in both forms of migraine and lasted for at least 9
min. There were no significant changes of PR-VEP amplitudes after 1 Hz
rTMS in migraineurs and after 10 Hz rTMS in healthy volunteers, nor
after sham stimulation. The recovery of a normal PR-VEP habituation
pattern after high-frequency rTMS is probably due to activation of the
visual cortex and the dishabituation in healthy volunteers to cortical
inhibition. We conclude, therefore, that the deficient interictal
PR-VEP habituation in migraine is due to a reduced, and not to an
increased, pre-activation excitability level of the visual cortex.
PMID: 11912123 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
10: Brain. 2003 Jun 23 [Epub ahead of print]. Related
Articles, Links
Lack of habituation causes high intensity dependence of
auditory evoked cortical potentials in migraine.
Ambrosini A, Rossi P, De Pasqua V, Pierelli F, Schoenen J.
Headache Clinic, INM Neuromed, Pozzilli (Isernia), Italy.
Migraineurs are characterized interictally by lack of habituation, or
even potentiation, of cortical evoked potentials during repetitive
stimulation and by a strong intensity dependence of auditory evoked
potentials (IDAP). To determine whether these two features of sensory
processing are interrelated, we have studied them simultaneously on the
same recordings of auditory evoked potentials (AEPs). AEPs were
obtained at four different stimulation intensities in 14 patients
suffering from migraine without aura (MO) and 14 healthy volunteers
(HV). For each intensity, 120 trials were averaged off-line globally
and over four sequential blocks of 30 trials. IDAP was expressed by the
amplitude/stimulus intensity function (ASF slope) for global and block
averages. Habituation was calculated as the percentage amplitude
variation between the first and fourth blocks for each stimulus
intensity. The IDAP slope for global averages was higher in MO (1.05
+/- 0.27 micro V/10 dB) than in HV (0.64 +/- 0.45 micro V/10 dB) (P =
0.008), but IDAP slopes for block averages were greater in MO only at
the fourth block (P = 0.048). First block amplitudes tended to be lower
in MO, except at 80 dB. There was a potentiation of AEP amplitudes at
every stimulus intensity in MO, contrasting with habituation in HV.
IDAP slopes were negatively correlated with mean habituation
percentages in pooled data from patients and controls (r = -0.610; P =
0.0006). This study confirms that IDAP is higher in migraineurs than in
healthy controls. It also shows that the AEP habituation is replaced by
potentiation at all stimulus intensities. The negative correlation
found between IDAP and habituation suggests that the latter is able to
have a strong influence on the former and perhaps even lead to it. In
migraine, the habituation deficit amplifies the IDAP and may thus be
the causal functional abnormality. We propose that it is due to a
decreased pre-activation level of sensory cortices, a hypothesis also
supported in this study by the lower amplitude of first AEP blocks in
patients.
PMID: 12821515 [PubMed - as supplied by publisher]
------------------------------------------------------------------------
11: Neurosci Lett. 2001 Jun 22;306(1-2):132-4. Related
Articles, Links
Reduced gating of middle-latency auditory evoked potentials
(P50) in migraine patients: another indication of abnormal sensory
processing?
Ambrosini A, De Pasqua V, Afra J, Sandor PS, Schoenen J.
Headache Clinics - IRCCS Neuromed via Atinense, 18, I-86077 , Pozzilli
(Isernia), Italy.
Habituation of cortical evoked responses to repetitive stimuli is
reduced in migraine between attacks. To explore another aspect of
information processing, we measured auditory sensory gating. The
amplitude of the P50 response to the second of two homologous stimuli
was significantly less reduced in migraineurs than in healthy
volunteers. This lack of auditory sensory gating may be due to a
hypofunction of monoaminergic subcortico-cortical pathways, which is
also supposed to cause the interictal deficit of cortical habituation
to repetitive stimuli.
PMID: 11403975 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
12: Neurology. 1996 May;46(5):1404-9. Related Articles,
Links
Intensity dependence of auditory evoked potentials is
pronounced in migraine: an indication of cortical potentiation and low
serotonergic neurotransmission?
Wang W, Timsit-Berthier M, Schoenen J.
Department of Neurology, University of Liege, Belgium.
Migraine is associated with stimulus hypersensitivity, increased evoked
cortical responses, and abnormal 5-HT levels in peripheral blood. We
studied cortical auditory evoked potentials (AEPs) between attacks in
35 patients suffering from migraine without aura (MO, n = 25) or with
aura (MA, n = 10) and in 25 healthy volunteers. Binaural tones were
delivered at 40, 50, 60, and 70 dB sensation level (SL) in a
pseudorandomized order. The intensity dependence of the auditory N1-P2
component was significantly greater in MO (p = 0.003) and MA (p = 0.02)
patients than in healthy controls, resulting in a much steeper
amplitude/stimulus intensity function slope. When three sequential
blocks of 40 averaged responses were analyzed at the 40- and 70-dB SL
intensities, N1-P2 amplitude decreased in second and third blocks at
both intensities in controls, but increased in migraineurs, a
difference that was significant in both blocks for the 70-dB SL
stimulus. The strong interictal dependence of AEPs on stimulus
intensity may thus be due to potentiation (instead of habituation) of
the response during repetition of the high-intensity stimulation. In
concordance with previous studies of visual evoked potentials, these
results confirm that migraine is characterized between attacks by an
abnormality of cortical information processing, which might be a
consequence of low 5-HT transmission and favor cortical energy demands.
PMID: 8628490 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
13: Cephalalgia. 2000 Nov;20(9):804-20. Related
Articles, Links
Visual, long-latency auditory and brainstem auditory evoked
potentials in migraine: relation to pattern size, stimulus intensity,
sound and light discomfort thresholds and pre-attack state.
Sand T, Vingen JV.
Department of Clinical Neurosciences, Trondheim University Hospital,
Norwegian University of Science and Technology.
trond.sand@medisin.ntnu.no
We aimed to estimate primary sensory evoked potential (EP) amplitude,
amplitude-intensity functions and habituation in migraine patients
compared with healthy control subjects and to investigate the possible
relation to check size, sound and light discomfort thresholds, and the
time to the next attack. Amplitudes of cortical visual evoked
potentials (VEP, check size 8' and 33'), cortical long latency auditory
evoked potential (AEP NIP1; 40, 55 and 70 dB SL tones) and brainstem
auditory evoked potential (BAEP wave IV-V; 40, 55 and 65 dB SL clicks)
were recorded and analysed in a blind and balanced design. The
difference between the response to the first and the second half of the
stimulus sequence was used as a measure of habituation. Twenty-one
migraine patients (16 women and five men, mean age 39.3 years, six with
aura, 15 without aura) and 22 sex- and age-matched healthy control
subjects were studied (18 women and four men, mean age 39.5 years). Low
sound discomfort threshold correlated significantly with low levels of
BAEP wave IV-V amplitude habituation (r = -0.30, P = 0.05). VEP an AEP
amplitudes, habituation, and amplitude-intensity function (ASF) slopes
did not differ between groups when ANOVA main factors were considered.
Control group VEP habituation was found for small check stimuli (P =
0.04), while potentiation was observed for medium sized checks (P =
0.02). The eight migraine patients who experienced headache within 24 h
after the test tended to have increased BAEP wave IV-V ASF slopes (P =
0.08). This subgroup did also have a significant VEP habituation to
small checks (P = 0.04). No correlation was found between different
modalities. These results suggest that: (i) VEP
habituation/potentiation state and brainstem activatio state may depend
on the attack-interval cycle in migraine; (ii) VEP habituation/
potentiation may depend on spatial stimulus frequency; (iii)
phonophobia (and possibly photophobia) may depend more on subcortical
(brainstem) function than on cortical mechanisms; (iv) low cortical
preactivation in migraine could not be confirmed; (v) EP habituation
and ASF analysis may reflect sensory modality-specific, not
generalized, central nervous system states in migraine and healthy
control subjects.
PMID: 11167910 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
14: Headache. 2000 Jan;40(1):30-5. Related Articles,
Links
Prophylactic treatment of migraine with beta-blockers and
riboflavin: differential effects on the intensity dependence of
auditory evoked cortical potentials.
Sandor PS, Afra J, Ambrosini A, Schoenen J.
Neurology Department, CHR Citadelle, University of Liege, Belgium.
OBJECTIVE: To investigate the influence of different pharmacological
treatments on the intensity dependence of auditory evoked cortical
potentials in migraineurs. BACKGROUND: Between attacks, patients with
migraine show abnormalities in cortical information processing and
decreased brain mitochondrial energy reserve. Both are most probably
relevant for migraine pathogenesis, and they could be differentially
modified by prophylactic drug therapy. Design.-The intensity dependence
of the auditory evoked cortical potentials is, on average, increased in
migraine. We have studied this intensity dependence in 26 patients
before and after a 4-month period of prophylaxis with beta-blockers (n
= 11, all migraine without aura; metoprolol or bisoprolol) or
riboflavin (n = 15, migraine without aura: 13, migraine with aura: 2).
Recordings were performed at least 3 days before or after an attack.
RESULTS: After the treatment with beta-blockers, the intensity
dependence of the auditory evoked cortical potentials was significantly
decreased (before: 1.66+/-1.02 microV/10 dB; after: 0.79+/-1.06
microV/10 dB, P=.02). The decrease in intensity dependence was
correlated significantly with clinical improvement (r = .69, P = .02).
There was no change in intensity dependence after riboflavin treatment
(before: 1.80+/-0.81 microV/10 dB; after: 1.56+/-0.83 microV/10 dB, P =
.39), although the majority of patients showed improvement.
CONCLUSIONS: These results confirm that beta-blockers and riboflavin
act on two distinct pathophysiological mechanisms. Combining both
treatments might enhance their efficacy without increasing central
nervous system side effects.
PMID: 10759900 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
15: Eur J Neurol. 2002 May;9(3):227-32. Related
Articles, Links
Median nerve somatosensory evoked potentials in migraine.
Ozkul Y, Uckardes A.
Department of Neurology, Faculty of Medicine, University of Harran,
Sanliurfa, Turkey. yasarozkul@yahoo.com
In visual evoked potential studies, habituation during stimulus
repetition with the same stimulus at a constant intensity has been
found to be abnormal in migraineurs between attacks. The purpose of
this study was to investigate habituation of somatosensory evoked
potentials (SEPs) and the effects of migraine on them. Eighty-five
subjects were included in the study: 30 healthy volunteers (HVs) and 55
migraineurs [30 with migraine without aura (MO), 25 with migraine with
aura (MA)]. During continuous stimulation at 3 Hz, four blocks of 100
responses were sequentially averaged of Erb's point (N9), cervical
(N13), and cortical (N20) median nerve SEPs. Mean amplitude changes in
the second, third and fourth blocks are expressed as percentages of the
first block. There was habituation to N13 and N20 in the second, third
and fourth blocks in HVs. In the migraine groups, there was no
habituation; on the contrary, potentiation was found. This potentiation
was statistically significant only in the second blocks for N13 (MO
P=0.007, MA P=0.01 versus HVs). However, in both migraineur groups, the
rate of N20 potentiations was statistically significant versus that in
HVs for all blocks (all P < 0.05). It is concluded that whilst
physiological habituation occurs in HVs for cervical and cortical SEPs,
in migraine patients there is an interictal deficit of habituation of
this sensory modality.
PMID: 11985630 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
16: Neuroreport. 1999 Apr 26;10(6):1235-8. Related
Articles, Links
Familial influences on cortical evoked potentials in
migraine.
Sandor PS, Afra J, Proietti-Cecchini A, Albert A, Schoenen J.
Neurology Department, University of Zurich, Switzerland.
Cortical information processing in migraine patients is impaired
between attacks, showing deficient habituation of pattern-reversal
visual evoked potentials (VEP), and strong intensity dependence of
auditory cortical evoked potentials (IDAP). This could be a genetic
trait as certain genetic patterns are known for evoked potentials in
healthy subjects. We investigated VEP habituation and IDAP in 20 pairs
of migraineurs made up of parents and their children. Using a
Monte-Carlo statistical method, we selectively assessed vertical
familial influences. VEP habituation and IDAP were abnormal in both
parents and children. However, similarity was far more pronounced
between related pairs than between unrelated pairs. Familial influences
are highly significant in determinants of cortical information
processing in migraineurs, hence supporting the important role of
genetic factors.
PMID: 10363931 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
17: Headache. 2000 Jan;40(1):36-40. Related Articles,
Links
Influence of colors on habituation of visual evoked
potentials in patients with migraine with aura and in healthy
volunteers.
Afra J, Ambrosini A, Genicot R, Albert A, Schoenen J.
Department of Neurology, Semmelweis University of Medicine, Budapest,
Hungary.
OBJECTIVE: To investigate whether colored glasses influence the
habituation of visual evoked potentials. BACKGROUND: We have previously
shown that during pattern-reversal stimulations lasting 2 minutes the
amplitude of the visual evoked potential increases in migraine with and
without aura between attacks, whereas it decreases in healthy
volunteers. Red light was found to increase visually evoked EEG fast
activity only in children with migraine with aura. Wearing rose-tinted
glasses for 4 months decreased attack frequency in parallel with a
reduction of the visually evoked EEG fast activity. METHODS: We
compared the change in amplitude of the visual evoked potential using
five different tinted glasses in 12 patients with migraine with aura
and in 10 healthy volunteers. During continuous stimulation at 3.1 Hz,
five blocks of 50 responses were sequentially averaged using red,
yellow, green, blue, and grey glasses and without glasses in a random
order and analyzed in terms of latencies and N1-P1 amplitudes.
Amplitude changes were calculated for each block by comparison with the
first block in every condition and analyzed statistically using Zerbe's
method. RESULTS: In healthy volunteers, the visual evoked potential
amplitude increased with red glasses compared to without glasses (P =
.05) or with green glasses (P = .03). In patients with migraine with
aura, no significant difference was detected using colored glasses. Our
findings in healthy volunteers are in line with earlier reports of
increased excitability of the human visual cortex when exposed to red
light. The lack of such a pattern in patients with migraine with aura
suggests that the visual cortex is interictally hypoexcitable rather
than hyperexcitable, which is consistent with studies of transcranial
magnetic stimulation.
PMID: 10759901 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
18: Headache. 2002 Jul-Aug;42(7):582-7. Related
Articles, Links
Effects of fluoxetine on habituation of pattern reversal
visually evoked potentials in migraine prophylaxis.
Ozkul Y, Bozlar S.
University of Harran, Faculty of Medicine, Department of Neurology,
Sanliurfa, Turkey.
OBJECTIVE: To investigate the effects of fluoxetine in migraine
prophylaxis on habituation of visually evoked potentials. BACKGROUND:
Habituation of pattern reversal visually evoked potentials was found to
be abnormal in migraine between attack, and this abnormality was most
likely due to serotonergic pathway dysfunction in the brain stem.
METHODS: One hundred nineteen subjects were included in the study: 40
healthy volunteers and 79 migraineurs not taking any prophylactic
migraine medication (44 without aura and 35 with aura). Visually evoked
potentials in migraineurs were recorded in the headache-free interval.
Amplitude change of the visually evoked potentials (N1-P1) was measured
between the first and fifth block of 50 sequential averagings during
continuous stimulation at 3.1 Hz. All migraineurs were placed on
fluoxetine 20 mg/day for prophylaxis of migraine. One month later,
visually evoked potentials were recorded again. RESULTS: Mean amplitude
changes in the fifth block expressed as percentages of the first block
were -13.4% +/- 19.2% in healthy volunteers, 9.8% +/- 23.3% in migraine
without aura, and 4.4% +/- 8.7% in migraine with aura during the
baseline period. The difference was significant between migraineurs and
healthy volunteers (both P= 0.0001), but not between migraineur groups.
After treatment, amplitude changes were -9.3% +/- 14.5% in migraine
without aura and -10.1% +/- 11.5% in migraine with aura. Habituation
pattern tended to normalize with prophylactic treatment, and mean
amplitude changes were not significant between migraineurs and healthy
volunteers (both P = 0.4). CONCLUSIONS: We concluded that the
fluoxetine prophylaxis corrects the interictal deficit of habituation
in migraineurs.
Publication Types:
* Clinical Trial
* Controlled Clinical Trial
PMID: 12482209 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
19: Brain. 1998 Feb;121 ( Pt 2):233-41. Related
Articles, Links
Visual evoked potentials during long periods of
pattern-reversal stimulation in migraine.
Afra J, Cecchini AP, De Pasqua V, Albert A, Schoenen J.
Department of Neurology, University of Liege, Belgium.
We have previously shown that during repetitive pattern-reversal
stimulation, lasting 2 min, the amplitude of the visual evoked
potential (PR-VEP) increases in migraineurs when tested interictally
whereas it decreases in healthy control subjects. According to
Sappey-Marinier et al. (J Cereb Blood Flow Metab 1992; 12: 584-92)
habituation of the PR-VEP in normal subjects is maxima after 12 min, at
a time when there is a decrease of stimulation-enhanced lactate levels
in the occipital cortex. We have therefore compared PR-VEP during long
periods of repetitive stimulation in healthy control subjects (n = 25)
and in patients suffering from migraine without (n = 25) and with aura
(n = 15) between attacks. During uninterrupted stimulation at 3.1 Hz
VEPs were sequentially averaged in blocks of 100 responses for a total
duration of 15 min and analysed in terms of latencies and peak-to-peak
amplitudes of N1-P1 and P1-N2 peaks. Amplitude changes from the
baseline were calculated for each block, by comparison with the first
block, and analysed statistically using Zerbe's method. The N1-P1 and
P1-N2 amplitudes in the first block tended to be lower in migraineurs
than in healthy control subjects. During the 15 min of stimulation,
amplitudes of both components progressively decreased in control
subjects, but remained stable in both groups of patients. The
difference between patients and control subjects proved to be
significant (P < 0.05). The neurophysiological data were not
correlated with clinical features such as attack frequency or duration
of illness. These results are yet another demonstration in migraine of
an interictal habituation deficit in cortical information processing,
which might favour lactate accumulation in sensory cortices during
sustained activation.
PMID: 9549502 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
20: Cephalalgia. 2002 Feb;22(1):48-53. Related
Articles, Links
A neural network model of sensitization of evoked cortical
responses in migraine.
Thomas E, Sandor PS, Ambrosini A, Schoenen J.
Research Center for Cellular and Molecular Neurobiology, University of
Liege, Belgium. ethomas@ulg.ac.be
Migraine patients show abnormalities of cerebral electrophysiology that
manifest themselves mainly during the attack interval. Cortical-evoked
potentials of migraineurs fail to habituate to repetitive presentations
of visual stimuli, and the amplitude of components of their auditory
cortical-evoked potentials have a higher dependence on the stimulus
intensities than in healthy subjects. A computer model of a neural
hetwork has been developed that is able to reproduce both these
neurophysiological dysfunctions. It predicts a positive correlation
between the magnitudes of both these dysfunctions. The model also
offers an explanation of why mutations in the same ion channel gene
with opposite consequences on channel function, e.g. P/Q Ca2+ channels
in migraine, may lead to similar electrophysiological abnormalities.
PMID: 11993613 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
21: Funct Neurol. 2000;15 Suppl 3:68-72. Related
Articles, Links
From neurophysiology to genetics: cortical information
processing in migraine underlies familial influences--a novel approach.
Sandor PS, Afra J, Proietti Cecchini AP, Albert A, Schoenen J.
Department of Neurology, CHR Citadelle, University of Liege, Belgium.
Migraine patients show impaired cortical information processing between
attacks with deficient habituation of pattern-reversal visual evoked
potentials (VEP), and strong intensity dependence of auditory cortical
evoked potentials (IDAP). This could be a genetic trait as certain
genetic patterns are known for evoked potentials in healthy subjects.
VEP-habituation and IDAP were studied in 40 migraine patients, i.e.
pairs of 20 parents and their children. We developed a novel approach
based on Monte Carlo statistics to selectively assess vertical familial
influences. Both groups, parents and children, were characterized by
abnormal VEP-habituation and IDAP. However, similarity between related
pairs was far more pronounced than similarity between unrelated pairs.
Assessed with a novel statistical approach, familial influences proved
to be highly significant in determining cortical information processing
in migraineurs, thus supporting the important role of genetic factors.
Publication Types:
* Clinical Trial
* Randomized Controlled Trial
PMID: 11200803 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
22: Cephalalgia. 1998 Jun;18(5):261-5; discussion 241.
Related Articles, Links
Interictal potentiation of passive "oddball" auditory
event-related potentials in migraine.
Wang W, Schoenen J.
Department of Neurology, University of Liege, Belgium.
We have studied habituation of the P3a component of the passive
"oddball" auditory event-related potential which reflects automatic
processing of a "novel" stimulus in 24 patients suffering from migraine
without aura and in 21 healthy volunteers. Three blocks of responses to
160 standard and to 40 novel tones were sequentially averaged at Cz and
analyzed for latencies and peak-to-peak amplitudes. Latencies of
components N1 and P2 elicited by standard tones and of components N1,
P2, N2, and P3a elicited by novel tones were not significantly
different between sequential blocks or between subject groups, nor were
mean N1-P2 amplitudes. The N2-P3a amplitude tended to be lower in
migraine, but not significantly so. The most striking result in
migraineurs was a significant potentiation of N2-P3a in successive
blocks, contrasting with an habituation in controls. Our previous
evoked- and event-related potential studies and the present one suggest
that deficient habituation, or even potentiation, represents
interictally a fundamental dysfunction of cortical information
processing in migraine, which might increase energy demands and play a
role in etiopathogenesis.
PMID: 9673805 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
23: Rev Neurol (Paris). 2001 Apr;157(4):365-75. Related
Articles, Links
[Clinical and pathophysiological contribution of
event-related potentials used to study migraine headache]
[Article in French]
Legrain V, Janne P, Laloux P, Ossemann M, Dupuis M, Reynaert C.
Departement de psychologie clinique, Faculte de Psychologie et des
Sciences de l'Education, Universite Catholique de Louvain,
Louvain-la-Neuve. legrain@clap.ucl.ac.be
Event-related potentials are electric brain manifestations evoked by
mental activities. This neurophysiological technique is able to
describe temporal succession of cognitive processing and allows to
measure the neurobiological correlates of each cognitive activity. The
evoked potentials of the oddball paradigm and the Contingent Negative
Variation (CNV) are also concerned by clinical applications in
neuropsychiatry, in neurology and in psychopharmacology. In the case of
migraine, the studies with CNV recorded between migraine attacks are
characterized by two major phenomena, cerebral hyperreactivity and lack
of habituation to repetitive stimuli. From cognitive point of view,
this can be interpreted as a difficulty from migraine sufferers to
adapt their information-processing to environmental constraints. From
neurological point of view, this trouble is related with dysregulation
of norepinephrin and serotonin ascending pathways. Studies with the
oddball paradigm potentials remain non consistent. The mismatch between
different methodologies could explain such a lack of consistency. The
neurophysiological studies have contributed to new physiopathological
hypothesis of migraine. Those hypothesis reveal that a shift in the
brain metabolic homeostasis could be the common factor of migraine
attacks. The clinical contribution of event-related potentials is of
little use in the diagnosis of migraine. But two purposes have been
suggested: the differential diagnosis between common migraine and
tension-type headaches and the monitoring of beta-blocking agents
prophylaxis.
Publication Types:
* Review
* Review, Academic
PMID: 11398007 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
24: Cephalalgia. 2000 Sep;20(7):621-31. Related
Articles, Links
Olfactory and trigeminal event-related potentials in
migraine.
Grosser K, Oelkers R, Hummel T, Geisslinger G, Brune K, Kobal G, Lotsch
J.
Department of Experimental and Clinical Pharmacology and Toxicology,
University of Erlangen Nurnberg, Erlangen, Germany.
BACKGROUND: Trigeminal/neuronal hyperexcitability and spreading
depression activating the trigemino-vascular system are discussed in
migraine-pathophysiology. This study investigated trigeminal and
olfactory event-related potentials in migraineurs. METHODS: Nasal
chemosensitivity was assessed in 19 female migraineurs with or without
aura > 72 h before or after an attack and in 19 healthy females
employing event-related cortical potentials (ERPs) after specific
trigeminal stimulation of nasal nociceptors with short pulses of CO2,
and specific olfactory stimulation with H2S. Odour thresholds and odour
identification performance were also tested. RESULTS: Migraineurs
exhibited greater responses to trigeminal stimulation, indicated by
significantly larger ERP amplitudes N1. In contrast, olfactory ERP
amplitudes P1N1 were significantly smaller in migraineurs. A
leave-one-out classification procedure on the basis of these two
parameters assigned 76.3% cases correctly. The olfactory ERP amplitude
discriminated better between groups than trigeminal ERPs (71.1 vs.
68.4% correct classification). CONCLUSIONS: Our data suggest trigeminal
hyperexcitability in migraineurs. A general increase of nasal
chemosensitivity is not supported because of smaller olfactory ERP
amplitudes in migraineurs. Olfactory ERPs discriminate better than
trigeminal ERPs between migraineurs and controls, emphasizing the
significance of the olfactory system in migraine.
PMID: 11128819 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
25: Brain. 1999 Jun;122 ( Pt 6):1147-55. Related
Articles, Links
Visual evoked potentials in migraine patients: alterations
depend on pattern spatial frequency.
Oelkers R, Grosser K, Lang E, Geisslinger G, Kobal G, Brune K, Lotsch
J.
Department of Experimental and Clinical Pharmacology, University of
Erlangen-Nurnberg, Germany. rieke_oelkers@med.uni-heidelberg.de
Visual information is conducted by two parallel pathways (luminance-
and contour-processing pathways) which are thought to be differentially
affected in migraine and can be investigated by means of
pattern-reversal visual evoked potentials (VEPs). Components and
habituation of VEPs at four spatial frequencies were compared between
26 migraineurs (13 without aura, MO; 13 with aura, MA) and 28 healthy
volunteers. Migraineurs were recorded in the headache-free interval (at
least 72 h before and after an attack). Five blocks of 50 responses to
chequerboards of 0.5, 1, 2 and 4 cycles per degree (c.p.d.) were
sequentially averaged and analysed for latency and amplitude.
Differences in VEPs were dependent on spatial frequency. Only when
small checks were presented, i.e. at high spatial frequency (2 and 4
c.p.d.), was the latency of N2 significantly prolonged in MA and did it
tend to be delayed in MO subjects. Habituation behaviour was not
significantly different between groups under the stimulating conditions
employed. Prolonged N2 latency might be explained by the lack or
attenuation of a contour-specific component N130 in migraineurs,
indicating an imbalance of the two visual pathways with relative
predominance of the luminance-processing Y system. These results
reflect an interictally persisting dysfunction of precortical visual
processing which might be relevant in the pathophysiology of migraine.
PMID: 10356066 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
26: Exp Brain Res. 2002 Jul;145(2):177-81. Epub 2002 May 09.
Related Articles, Links
Modulation of visual cortical excitability in migraine with
aura: effects of 1 Hz repetitive transcranial magnetic stimulation.
Brighina F, Piazza A, Daniele O, Fierro B.
Istituto di Neuropsichiatria, Universita di Palermo, via G. La Loggia
1, 90129 Palermo, Italy.
Recent studies showed hyperexcitability of the occipital cortex in
subjects affected by migraine with aura. It has been shown that 1 Hz
repetitive transcranial magnetic stimulation (rTMS) reduces
excitability of visual cortex in normal subjects. The aim of the study
was to investigate the effects of low frequency (1 Hz) rTMS on visual
cortical excitability by measuring changes in phosphene threshold (PT)
in subjects with migraine with aura. Thirteen patients with migraine
with aura and 15 healthy controls were examined. Using a standardized
transcranial magnetic stimulation protocol of the occipital cortex, we
assessed the PT (the lowest magnetic stimulation intensity at which
subjects just perceived phosphenes) before and after a 1-Hz rTMS train
delivered at PT intensity for 15 min. The difference in the proportion
of subjects reporting phosphenes in migrainer and control groups was
significant (migrainers: 100% vs controls 47%; P<0.05), and 1 Hz
rTMS over the occipital cortex led to a significantly increased visual
cortex excitability expressed as a decrease in PT in subjects affected
by migraine with aura. Conversely, after a 1-Hz TMS train normal
subjects showed increased PT values, which suggests a decreased visual
cortex excitability. Our findings confirm that the visual cortex is
hyperexcitable in migrainers and suggest a failure of inhibitory
circuits, which are unable to be upregulated by low frequency rTMS.
PMID: 12110957 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
27: Patol Fiziol Eksp Ter. 1996 Apr-Jun;(2):3-6.
Related Articles, Links
[Multimodal evoked potentials and central mechanisms of
afferentation in trigeminal neuralgia]
[Article in Russian]
Meizerov EE, Reshetniak VK, Koroleva MV, Grachev IuV.
Multimodal evoked potentials in patients with trigeminal neuralgia are
analyzed in the paper. The comprehensive studies of cortical trigeminal
somatosensory evoked potentials, visual evoked potentials, and
brainstem auditory evoked potentials have revealed their changes that
are indicative of the impaired central mechanisms of afferentation in
patients with trigeminal abnormality. The findings are discussed in the
light of the theory of generator mechanisms of neuropathological pain
syndromes.
PMID: 8754133 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
28: J Neurol Sci. 1996 Jul;139(1):106-10. Related
Articles, Links
Interictal cortical hyperexcitability in migraine patients
demonstrated with transcranial magnetic stimulation.
van der Kamp W, Maassen VanDenBrink A, Ferrari MD, van Dijk JG.
Department of Neurology and Clinical Neurophysiology, University
Hospital Leiden, Netherlands.
Cortical excitability to magnetic stimulation was investigated
interictally in 10 patients with migraine with aura, 10 with migraine
without aura and in 10 healthy volunteers. Thresholds, latencies and
amplitudes of the magnetic-evoked potentials (MEPs) were measured from
threshold to 100% stimulus intensity in 10% steps. Compound motor
action potentials (CMAPs) evoked with supramaximal electrical
stimulation of the ulnar nerve were used to calculate MEP/CMAP
amplitude ratios. Thresholds and latencies of MEPs did not differ
between patients and controls. MEP/CMAP amplitude ratios were
significantly increased at all intensities in patients with migraine
with aura (RM-ANOVA, p < 0.01) and without aura (p < 0.05)
compared with controls. In migraine patients, MEP amplitudes and
MEP/CMAP amplitude ratios were positively related to the frequency of
migraine attacks (Spearman's r = 0.47, p < 0.01 and r = 0.56, p <
0.002, respectively). MEP parameters were not related to the side of
the headache nor the aura, in either type of migraine, implying that
both hemispheres are equally involved in migraine. Migraine with aura
and, to a lesser extent, migraine without aura, are associated with
increased interictal cortical excitability.
PMID: 8836980 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
29: Cephalalgia. 1985 May;5 Suppl 2:53-8. Related
Articles, Links
Visual evoked potentials and brainstem auditory evoked
potentials in migraine and transient ischemic attacks.
Benna P, Bianco C, Costa P, Piazza D, Bergamasco B.
A study of brainstem auditory evoked potentials (BAEPs) and pattern
reversal visual evoked potentials (VEPs), recorded in intercritical
phase, was carried out in 20 subjects (10 suffering from common
migraine and 10 suffering from vertebrobasilar TIA) in order to obtain
a comparative evaluation of cortical-subcortical functions. The data we
obtained demonstrate the presence of BAEPs alterations in patients with
previous vertebrobasilar TIA: no abnormalities were found in the
migraine group. VEPs parameters are normal in both groups. Our data
show that the study of the so-called "stimulus-related" potentials,
such as BAEPs and pattern reversal VEPs, is useful in evaluating the
damage produced by any noxa, while it cannot clearly emphasize
individual factors predisposing to a specific pathology, as the absence
of specific alterations in migraine patients demonstrates.
PMID: 4016942 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
30: Ann Neurol. 1998 Aug;44(2):209-15. Related
Articles, Links
Comment in:
* Ann Neurol. 1999 Mar;45(3):415-6.
* Ann Neurol. 1999 Mar;45(3):416-7.
Interictal cortical excitability in migraine: a study using
transcranial magnetic stimulation of motor and visual cortices.
Afra J, Mascia A, Gerard P, Maertens de Noordhout A, Schoenen J.
Department of Neurology, CHR Citadelle, University of Liege, Belgium.
We performed transcranial magnetic stimulations of the motor and visual
cortices in healthy controls (n = 27) and in patients suffering from
migraine without (n = 33) or with (n = 25) aura between attacks. By
using a 13-cm circular coil placed over the vertex and recordings of
the first dorsal interosseus muscle, we measured thresholds (at rest
and during contraction), amplitudes of motor evoked potentials and
cortical silent periods. Paired stimulations with short (1-20 msec)
interstimulus intervals were performed to assess intracortical
inhibition. The visual cortex was stimulated with the same coil placed
over the occipital scalp (7 cm above the inion) and the prevalence and
threshold of phosphene production was determined. In patients with
migraine with aura, motor thresholds during isometric contraction were
significantly higher, whereas the prevalence of stimulation-induced
phosphene production was lower compared with healthy controls. These
changes were not correlated with attack frequency or disease duration.
No differences were found between subject groups in thresholds at rest,
motor evoked potential amplitudes, cortical silent periods, or response
curves after paired stimuli. These results are in favor of cortical
hypoexcitability rather than hyperexcitability in patients with
migraine with aura between attacks.
Publication Types:
* Clinical Trial
* Controlled Clinical Trial
PMID: 9708543 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
31: Neurology. 2002 Apr 9;58(7):1066-9. Related
Articles, Links
Transcranial magnetic stimulation of visual area V5 in
migraine.
Battelli L, Black KR, Wray SH.
Department of Psychology, Harvard University, Cambridge, MA 02138, USA.
Battelli@wjh.harvard.edu
OBJECTIVE: To examine visual cortical excitability in persons with
migraine using transcranial magnetic stimulation (TMS) over an
extrastriate area of the brain, area V5. BACKGROUND: Previous studies
found that persons with migraine have a lower phosphene threshold than
healthy control subjects with TMS delivered over the primary visual
cortical area V1. The result suggests that the occipital cortex in
migraineurs between migraine attacks is hyperexcitable. However, it is
not known whether interictal cortical hyperexcitability is also present
in areas of the association visual cortex. METHOD: To investigate this,
single-pulse TMS was delivered over visual area V5, the motion cortex,
to 16 persons with migraine and visual aura, nine migraineurs without
visual aura, and 16 healthy control subjects. TMS was delivered at
intensities ranging from 30 to 100% of maximum stimulator output or
until the participant reported seeing phosphenes (visual illusions
characterized by flashes of light). Thresholds to phosphenes were
obtained for each participant using a staircase procedure. RESULT:
Significantly lower phosphene thresholds for TMS delivered over V5 were
found in migraineurs as compared with control subjects. Qualitatively,
the migraineurs' experience of phosphenes were more vivid, florid, and
sustained compared with that of control subjects. CONCLUSION: Results
of this study indicate that hyperexcitability of the visual cortex in
migraine goes beyond visual area V1 and demonstrates for the first time
a significant difference in threshold for excitability of visual area
V5 in persons with migraine.
PMID: 11940694 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
32: Exp Brain Res. 2003 Jun;150(3):332-40. Epub 2003 Apr 16.
Related Articles, Links
Effects of repetitive transcranial magnetic stimulation on
visual evoked potentials: new insights in healthy subjects.
Fumal A, Bohotin V, Vandenheede M, Seidel L, de Pasqua V, de Noordhout
AM, Schoenen J.
University Department of Neurology, CHR Citadelle Hospital, 4000 Liege,
Belgium.
In a previous comparative study with migraineurs, we found in 24 normal
subjects that the amplitude of the pattern-reversal visual evoked
potential (PR-VEP) in the first block of 100 responses and its
habituation over 6 sequential blocks were significantly decreased after
1 Hz repetitive transcranial magnetic stimulation (rTMS), while 10 Hz
rTMS had no significant effect. We report here our results on the
reproducibility of the rTMS effect studied in ten of these subjects by
repeating the recordings for each frequency three times on different
days. We have also reanalysed the data obtained in 24 normal subjects,
looking separately at the results in those stimulated at an intensity
equal to phosphene threshold (group 1; n=14) and those stimulated at
110% of motor threshold because of unelicitable phosphenes (group 2;
n=10). We finally determined the precise duration of the rTMS effect.
Despite some interindividual variability, the effects of both rTMS
frequencies on first block amplitude, habituation between first and
sixth block and habituation slope over the six blocks were highly
reproducible. The only difference between the two groups of subjects
was the effect of 1 Hz rTMS on the second measured PR-VEP component.
Whereas first block amplitude of the first P1-N1 component and
habituation were decreased in both groups, such a decrease was found
for the second P1-N2 component only in group 1 stimulated at phosphene
threshold. The dishabituation of the N1-P1 component after 1 Hz rTMS
was maximal at 15 min, but lasted up to 33 min, while that of P1-N2
disappeared after 3 min. There was a non-significant trend ( p=0.06)
for a reduction of first block amplitude after 10 Hz rTMS in the total
group of subjects, but no effect on habituation. The inhibitory effect
of 1 Hz rTMS, which reduces in healthy controls both first block PR-VEP
amplitude and habituation, probably by decreasing the preactivation
excitability level of the underlying visual cortex, is thus
reproducible and long lasting. Long trains of 10 Hz rTMS tend to
attenuate reproducibly the cortical preactivation level in normal
subjects, but they do not affect habituation at all, which contrasts
with their effect in migraineurs, in whom, as previously reported, they
significantly correct the habituation deficit. The absence of an effect
of 1 Hz rTMS on PR-VEP P1-N2 in subjects stimulated at 110% of motor
threshold may be explained by the deeper anatomical location of the
cortical generators of this component and the lower stimulation
intensity used. Taken together our results confirm that the effect of
rTMS on the underlying cortex depends on several variables such as
frequency, intensity and level of cortical preactivation.
PMID: 12698314 [PubMed - in process]
------------------------------------------------------------------------
33: Cephalalgia. 2001 Jun;21(5):611-6. Related
Articles, Links
Altered cerebrovascular response pattern in interictal
migraine during visual stimulation.
Backer M, Sander D, Hammes MG, Funke D, Deppe M, Conrad B, Tolle TR.
Department of Neurology, Technical University of Munich, Munich,
Germany.
A dysbalance of the cerebrovascular response during functional
activation of the brain has been postulated as a factor in the
pathophysiology of migraine. To determine the dynamic pattern of the
cerebrovascular response in migraineurs compared with a control group,
changes of the cerebral perfusion during cerebral activation were
studied with high temporal resolution by functional transcranial
Doppler sonography (fTCD). The cerebral blood flow velocity (CBFV) in
the right posterior cerebral artery (PCA) and the left middle cerebral
artery (MCA) was measured simultaneously during visual stimulation in
19 interictal migraineurs and in 19 age- and sex-matched control
subjects. Data were analysed with a previously validated technique
based on automated stimulus-related averaging of the CBFV. The MCA
migraineurs exhibited a steady increase of CBFV during the stimulation,
while normal subjects showed a habituation of the CBFV response. The
lack of habituation in migraineurs was significantly (P < or = 0.05)
more pronounced across patients with a high attack frequency (> or =
4 per month) compared with migraineurs with a low attack frequency
(< 4 per month). In the PCA, compared with normal subjects,
migraineurs showed significantly (P < or = 0.05) stronger CBFV
changes at the beginning and after the end of stimulation, with a
slower decline to baseline. Data are in accordance with
electrophysiological findings in migraineurs. It is assumed that a lack
of habituation of the cerebrovascular response in migraineurs might
contribute to a disturbance of the metabolic homeostasis of the brain
that might induce migraine attacks.
PMID: 11472388 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
34: Headache. 2003 Mar;43(3):303. Related Articles,
Links
Modulation of trigeminal reflex excitability in migraine:
effects of attention and habituation on the blink reflex.
De Tommaso M, Murasecco D, Libro G, Guido M, Sciruicchio V, Specchio L,
Gallai V, Puca F.
Int J Psychophysiol. 2002 Jun;44(3):239-249 The modulation of
trigeminal reflex excitability in migraine patients was evaluated
during the asymptomatic phase by studying the effects of attention,
habituation and preconditioning stimulus on the R2 and R3 components of
the blink reflex (BR). Fifty patients suffering from migraine without
aura, 20 affected by migraine with aura and 35 sex- and age-matched
controls were selected. In subgroups of migraine with-aura and
without-aura patients, and normal controls, the blink reflex was
elicited during different cognitive situations: (a) spontaneous mental
activity; (b) stimulus anticipation; (c) recognition of target numbers.
In the remaining subjects, R2 and R3 habituation was evaluated by
repetitive stimulation at 1, 5, 10, 15, 20, 25 and 30 s intervals. The
R2 and R3 recovery curves were also computed. A reduced R3 threshold
with a normal pain threshold was found in migraine with-aura and
without-aura patients; the R3 component was not significantly
correlated with the pain thresholds in patients and controls. The R2
and R3 components were less influenced by the warning of the stimulus
in migraine without-aura and migraine with-aura patients, in comparison
with the control group. A slight increase of both R2 and R3 recovery
after preconditioning stimulus was also observed in migraine patients,
probably caused by a phenomenon of trigeminal hyperexcitability
persisting after the last attack. The abnormal BR modulation by
alerting expresses in migraine a dysfunction of adaptation capacity to
environmental conditions, probably predisposing to migraine. Comment:
Further physiologic and functional evidence for the interictal
hyperexcitability of neurons in patients with migraine, in this case
trigeminal neurons involved in the blink reflex. SJT
PMID: 12603665 [PubMed - as supplied by publisher]
------------------------------------------------------------------------
35: Curr Opin Neurol. 1998 Jun;11(3):205-9. Related
Articles, Links
Brain excitability in migraine: evidence from transcranial
magnetic stimulation studies.
Aurora SK, Welch KM.
Henry Ford Hospital and Health Sciences Center, Department of
Neurology, Detroit, Michigan, USA.
Central neuronal hyperexcitability is proposed to be the putative basis
for the physiologic disturbances in migraine. Because there are no
structural disturbances in migraine, only physiologic studies can
provide insight into the underlying mechanisms. Recently, transcranial
magnetic stimulation has been developed as a valuable research tool and
can be used to study brain function noninvasively. This article is a
review of the studies done in migraine using transcranial magnetic
stimulation.
Publication Types:
* Review
* Review, Tutorial
PMID: 9642537 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
36: No To Shinkei. 1998 Apr;50(4):361-5. Related
Articles, Links
[Superficial siderosis of the central nervous system: an
electrophysiological study]
[Article in Japanese]
Shimo Y, Nohara C, Hotta M, Miwa H, Mizuno Y.
Department of Neurology, Juntendo University School of Medicine, Tokyo,
Japan.
Superficial siderosis of the central nervous system (SS) is a rare
neurological disorder characterized by symptoms such as neurosensory
hearing loss, ataxic gait, and spastic paraparesis. Recently, magnetic
resonance imaging (MRI) enables us to make a clinical diagnosis.
However, the exact pathophysiological mechanism underlying this
disorder remains uncertain. Although iron chelation therapy has been
attempted experimentally, it has not been successful and there is no
effective medical treatment available. Towards the better understanding
of the pathophysiological mechanism underlying SS, we performed
electrophysiological studies, in which multiple evoked potential
studies were included, in 3 patients with SS. Somatosensory evoked
potentials (SEPs) evoked by median nerve stimulation were all normal,
but those evoked by the posterior tibial nerve stimulation showed a
significant delay of the latency of P40. In the auditory brainstem
response (ABR) studies, there were no reproducible responses of the
brainstem origin. In the blink reflex studies, R2 latency was delayed
in one patient. In visual evoked potential (VEP) studies, the latency
of P100 was delayed in two of three patients, unless all the patients
clinically showed no visual symptom. The nerve conduction velocity
studies performed in peripheral nerves of upper and lower extremities
were all normal. The abnormal findings of ABR and SEP may suggest that
the acoustic nerve and the posterior funiculus of the spinal cord are
involved, respectively. These findings are also in a good agreement
with pathological findings of SS reported in the literature. In SS, the
hemosiderine accumulation is usually less severe in the visual tract;
however, the delay of VEPs may suggest the latent dysfunctioning of the
visual system in SS. It is suggested that multiple evoked potential
study is useful for clinical evaluation of SS.
PMID: 9592826 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
37: Curr Opin Neurol. 2000 Jun;13(3):273-6. Related
Articles, Links
Migraine: imaging the aura.
Aurora SK, Welch KM.
Neurophysiology Laboratory, Henry Ford Hospital, Detroit, Michigan
48202, USA. sheaur@neuro.hfh.edu
We currently conceive of a migraine attack as originating in the brain.
Triggers of an attack initiate a depolarizing neuroelectric and
metabolic event likened to the spreading depression of Leao. This event
activates the headache and associated features of the attack by
mechanisms that remain to be determined, but appear to involve either
peripheral trigeminovascular or brainstem pathways, or both. The
excitability of cell membranes, perhaps partly genetically determined,
is the brain's susceptibility to attacks. Factors that increase or
decrease neuronal excitability constitute the threshold for triggering
attacks. Using a model of visual stress-induced migraine or by studying
spontaneous attacks and applying advanced imaging and
neurophysiological methods, results have been obtained that support
spreading neuronal inhibition as the basis of aura. This neuroelectric
event is accompanied by hyperoxia of the brain, possibly associated
with vasodilation. Evidence has also been obtained that the spreading
cortical event can activate the subcortical centers possibly involved
in nociception and associated symptoms of the migraine attack.
Susceptibility to migraine attacks appears to be related to brain
hyperexcitability. These newer techniques of functional neuroimaging
have confirmed the primary neural basis of the migraine attack with
secondary vascular changes, reconciling previous theories into a
neurovascular mechanism.
Publication Types:
* Review
* Review, Tutorial
PMID: 10871250 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
38: Curr Opin Neurol. 2003 Feb;16(1):5-13. Related
Articles, Links
Migrainous vertigo: development of a pathogenetic model and
structured diagnostic interview.
Furman JM, Marcus DA, Balaban CD.
Department of Otolaryngology, University of Pittsburgh School of
Medicine, Pittsburgh, Pennsylvania 15213, USA. furman@pitt.edu
PURPOSE OF REVIEW: Vestibular symptoms occur frequently in patients
with migraine. This review refines recently proposed diagnostic
criteria for migraine-related vestibular symptoms, and develops a
pathophysiological model for the interface between migraine and the
vestibular system. RECENT FINDINGS: The epidemiological link between
migraine and vestibular symptoms and signs suggests shared pathogenetic
mechanisms. Links between the vestibular nuclei, the trigeminal system,
and thalamocortical processing centers provide the basis for the
development of a pathophysiological model of migraine-related vertigo.
During the last year, several studies have increased understanding of
the relationship between migraine and vestibular symptoms. A study of
motion sickness and allodynia in migraine patients supports the
importance of central mechanisms of sensitization for migraine-related
vestibular symptoms. A study has demonstrated effective treatment of
vertigo with migraine therapy. The identification of migrainous
vertigo, however, is hampered by a lack of standardized assessment
criteria for both clinical and research practices. The application of
published criteria for the diagnosis of migrainous vertigo allows the
development of a standardized, structured assessment interview.
SUMMARY: An understanding of the relationship between migraine and the
vestibular system increases knowledge of the pathogenesis of both
migraine and vertigo. In addition, studies have identified successful
treatment, with standard migraine therapies, of vestibular symptoms in
patients with both migraine and vertigo. The use of a standardized
assessment tool to identify this unique population of patients will
help future studies to test both the pathological model and effective
treatment options.
Publication Types:
* Review
* Review, Tutorial
PMID: 12544852 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
39: Funct Neurol. 1986 Oct-Dec;1(4):357-61. Related
Articles, Links
Bulbo-cortical pathways and their possible relevance to
migraine and epilepsy.
Lance JW, Adams RW, Lambert GA.
Facilitation of the visual evoked response from the reticular formation
in the cat has been shown to depend on nicotinic cholinergic receptors
distinct from the muscarinic cholinergic receptors responsible for the
arousal reaction. An increase in the amplitude of visual evoked
responses in migraineurs does not therefore imply any change in
reticulocortical activity of relevance to epilepsy. Stimulation of
locus ceruleus and nucleus raphe dorsalis exerted comparatively minor
effects on the visual evoked response and did not alter the discharge
rate of cortical neurons in the resting state. It is concluded that the
changes in cerebral blood flow previously reported to result from
stimulation of these monoaminergic brainstem nuclei, which resemble
those observed in migraine, must be exerted directly on the cortical
microcirculation and not simply follow the metabolic demand of cortical
neurons. There is thus a place in the management of migraine for
pharmaceutical agents acting on cerebral vessels even if the neural
hypothesis for the mechanism of migraine proves to be correct.
PMID: 3609865 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
40: Electromyogr Clin Neurophysiol. 2002
Apr-May;42(3):175-9. Related Articles, Links
Visual evoked potential & brainstem auditory evoked
potentials in acute attack & after the attack of migraine.
Kochar K, Srivastava T, Maurya RK, Jain R, Aggarwal P.
Department of Medicine, S.P. Medical College, Bikaner-334003,
Rajasthan, India.
PURPOSE: To study the effect on visual evoked potential (VEP) and
brainstem auditory evoked potential (BAEP) at time of acute attack and
after 7 days of the attack of migraine. MATERIAL AND METHODS: We
studied BAEP and pattern reversal VEP in 25 patients during acute
attack and after 7 days of the attack. The diagnosis of migraine was
established according to criteria given by international headache
society (IHS). Peak and interpeak latencies (IPL's) of BAEP and P100
latency of VEP were the main criteria to judge abnormalities. RESULTS:
There were prolonged peak and interpeak latencies in BAEP and prolonged
peak latency (P100) in VEP at the time of acute attack of migraine. The
data of these abnormal recording were highly significant. After 7 days
when the attack was over, we recorded the BAEP and VEP again. The
observation obtained at this time was comparable to normal values.
CONCLUSIONS: From the observation of this study we can safely conclude
that in acute attacks of migraine there may be some pathological
changes in different areas of brain and brainstem, producing changes in
evoked potential which are statistically highly significant. However,
these changes are reversible, as the values of BAEP & VEP on 7th
day after the attack were comparable to those observed in normal
healthy control.
PMID: 11977431 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
41: Pain. 2000 Mar;85(1-2):247-54. Related Articles,
Links
Intensity dependence of auditory evoked cortical potentials
in migraine families.
Siniatchkin M, Kropp P, Neumann M, Gerber W, Stephani U.
Institute of Medical Psychology, University of Kiel, Niemannsweg 147,
D-24105, Kiel, Germany. siniatchkin@med.psych.uni-kiel.de
Intensity dependence of auditory evoked cortical potentials is abnormal
in migraine. This study investigated intensity dependence in migraine
and healthy families using group comparisons and analysis of individual
differences. Migraineurs were characterized by a steeper
amplitude/stimulus function slope and more pronounced difference
between the amplitudes of N1-P2 on the more and the less intensive
tones than healthy age matched subjects. Apart from migraine, the age
of the participants was an important predictive variable of intensity
dependence. Analysis of individual differences revealed low sensitivity
and moderate specificity of intensity dependence for migraine. Familial
prevalence of intensity dependence among first-degree relatives in
migraine families was equal to that in healthy families. These findings
support the assumption that high-intensity dependence reflects a
functional CNS trait which is more pronounced and prevalent in
migraine, but may also be found in healthy individuals and in other
neuropsychiatric disorders. Increased intensity dependence is only one
of several factors contributing to the risk for this form of headache.
Publication Types:
* Clinical Trial
PMID: 10692625 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
42: Cephalalgia. 1999 Apr;19(3):137-46. Related
Articles, Links
Clinical neurophysiology in childhood headache.
Puca F, de Tommaso M.
Clinica Neurologica I, Universita di Bari, Italy.
Electrophysiological studies in childhood headache are of interest
because of the need to make a clinical diagnosis and also because of
the efficacy of physiopathological studies in juvenile age attributable
to the recent outcome of the illness, with less clinical modification
by environmental factors or drug use. Electrophysiological studies in
childhood headache are concerned with migraine and
electroencephalographic (EEG) evaluations; evoked potentials,
event-related potentials and, less often, electromyographic studies are
also reported. Visual analysis of EEG suggests an association between
migraine and epilepsy; quantitative EEG, visual and event-related
evoked potentials show fluctuating abnormalities, depending on the
occurrence of the migraine attacks and permanent anomalous patterns
related to the basic mechanisms underlying the disease. Blink reflex
studies might suggest a primary dysfunction of the nociceptive control
central system in children affected by tension-type headache and
migraine. The use of neurophysiological procedures in juvenile migraine
is considered limited in clinical practice and of particular interest
in neurophysiological studies of headache.
Publication Types:
* Review
* Review, Tutorial
PMID: 10234460 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
43: J Neurol. 2002 Sep;249(9):1268-71. Related
Articles, Links
Comparison of cortical excitability in chronic migraine
(transformed migraine) and migraine without aura. A transcranial
magnetic stimulation study.
Ozturk V, Cakmur R, Donmez B, Yener GG, Kursad F, Idiman F.
Dokuz Eylul University, Medical School, Department of Neurology, 35340,
Izmir, Turkey. vesile.ozturk@deu.edu.tr
We studied the excitability of the motor cortex in patients with
migraine without aura (MWOA) (n = 20) and with chronic migraine (CM) (n
= 20) using transcranial magnetic stimulation (TMS). By using a 90-mm
circular coil placed over the vertex and recording of the first dorsal
interosseous muscle, we measured thresholds, latencies and amplitudes
of motor evoked potentials and duration of cortical silent periods in
patient groups and in controls (n = 20). No differences were found
between groups for threshold, latency and amplitude values. However,
the duration of the cortical silent period was longer in CM patients,
being significantly different from both controls and MWOA. We suggest
that either this difference in cortical excitability may develop during
transformation from MWOA to CM or different pathophysiological
mechanisms may play a role in these two headache syndromes.
PMID: 12242552 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
44: Rev Neurol. 1997 Oct;25(146):1611-6. Related
Articles, Links
[Neurophysiological studies of headaches]
[Article in Spanish]
Munoz-Farjas E.
Servicio de Neurologia, Hospital Clinico Universitario de Zaragoza,
Espana.
INTRODUCTION AND OBJECTIVE: The diagnosis of headache is based on the
clinical criteria suggested by the IHS in 1988. The neurophysiological
examinations often used in the study of headache may support the
clinical diagnosis and give information as to the prognosis. The
objective of this paper is to review the neurophysiological
examinations most often used in the clinical and pathological
investigation of headache. DEVELOPMENT: As shown by recent studies, the
EEG is of little value in the routine evaluation of a patient with
headache. However, it may be useful as an exploratory test for
underlying pathology in atypical headache or when intra-cranial
pathology is suspected. Evoked potentials, when used to study migraine,
show absence of Habituation (or Potentiation) in migraine patients.
This finding may represent abnormality in the processing of information
at a cortical level in these patients. There is a tendency to unify the
theory of neurone hypoxia and the absence of Habituation in Migraine as
a single hypothesis of pathogenesis. Negative Contingent Variation has
proved to be clinically useful to optimize treatment in Migraine. The
electromyogram and Muscle Reflexes have been used in the study of
Tension Type Headaches, ES2 changes, showing brainstem antinociceptive
reflexes support the participation of a central factor in the origin of
chronic Tension Headache. CONCLUSION: Neurophysiological tests may be
useful in investigation of the pathology of headache since they permit
a functional study of many neurone paths and the action of drugs on the
central nervous system.
Publication Types:
* Review
* Review, Tutorial
PMID: 9462993 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
45: Neurology. 1997 May;48(5):1462-4. Related Articles,
Links
Interictal cortical excitability to magnetic stimulation in
familial hemiplegic migraine.
van der Kamp W, MaassenVanDenBrink A, Ferrari MD, van Dijk JG.
Department of Neurology and Clinical Neurophysiology, Leiden University
Hospital, the Netherlands.
We studied interictal cortical excitability with magnetic stimulation
in controls, in patients with migraine with aura, and in patients with
familial hemiplegic migraine (FHM), in which ictal hemiparesis occurs.
Amplitudes (p < 0.05) and amplitude ratios (p < 0.01) revealed
heightened excitability in migraine with aura when compared to
controls. In patients with FHM, mean thresholds were higher (p <
0.001) and conduction times longer (p < 0.01) than in controls. In
FHM, amplitudes were lower on the ictally paretic side of the body than
on the other (p < 0.05). Patients with FHM may have increased
interictal cortical excitability, complicated by decreased excitability
of the affected side.
PMID: 9153495 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
46: Can J Neurol Sci. 1999 Nov;26 Suppl 3:S12-9.
Related Articles, Links
Pathophysiology of migraine--new insights.
Hargreaves RJ, Shepheard SL.
Merck Research Laboratories, West Point PA 9486, USA.
Current theories propose that the primary dysfunction in migraine
occurs within the CNS and that this evokes changes in blood vessels
within pain-producing intracranial meningeal structures that give rise
to headache pain. Migraine is now thought of as a neurovascular
disorder. It has been proposed that genetic abnormalities may be
responsible for altering the response threshold to migraine specific
trigger factors in the brain of a migraineur compared to a normal
individual. The exact nature of the central dysfunction that is
produced in migraineurs is still not clear and may involve spreading
depression-like phenomena and activation of brain stem monoaminergic
nuclei that are part of the central autonomic, vascular and pain
control centers. It is generally thought that local vasodilatation of
intracranial extracerebral blood vessels and a consequent stimulation
of surrounding trigeminal sensory nervous pain pathways is a key
mechanism underlying the generation of headache pain associated with
migraine. This activation of the 'trigeminovascular system' is thought
to cause the release of vasoactive sensory neuropeptides, especially
CGRP, that increase the pain response. The activated trigeminal nerves
convey nociceptive information to central neurons in the brain stem
trigeminal sensory nuclei that in turn relay the pain signals to higher
centers where headache pain is perceived. It has been hypothesized that
these central neurons may become sensitized as a migraine attack
progresses. The 'triptan' anti-migraine agents (e.g. sumatriptan,
rizatriptan, zolmitriptan naratriptan) are serotonergic agonists that
have been shown to act selectively by causing vasoconstriction through
5-HT1B receptors that are expressed in human intracranial arteries and
by inhibiting nociceptive transmission through an action at 5-HT1D
receptors on peripheral trigeminal sensory nerve terminals in the
meninges and central terminals in brain stem sensory nuclei. These
three complementary sites of action underlie the clinical effectiveness
of the 5-HT1B/1D agonists against migraine headache pain and its
associated symptoms.
Publication Types:
* Review
* Review, Tutorial
PMID: 10563228 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
47: Neurology. 2002 Apr 23;58(8):1234-8. Related
Articles, Links
Acute migraine headache: possible sensitization of neurons in
the spinal trigeminal nucleus?
Kaube H, Katsarava Z, Przywara S, Drepper J, Ellrich J, Diener HC.
Institute of Neurology, National Hospital for Neurology and
Neurosurgery, London, UK. holgerk@ion.ucl.ac.uk
OBJECTIVE: To investigate trigeminal sensory processing in patients
with migraine using a novel "nociception-specific" blink reflex.
METHODS: Seventeen patients with unilateral migraine headache were
studied within 6 hours of onset. Blink reflexes were elicited with a
standard stimulating electrode (standard blink reflex) and concentric
stimulating electrode (nociception-specific blink reflex) during the
acute migraine attack, after treatment with IV lysine acetylsalicylate
(1,000 mg) or oral zolmitriptan (5 mg) and interictally. RESULTS: After
standard stimulation, no differences were detected for the R1 and R2
onset latencies and areas under the curve (AUC) between the different
time points and the headache and nonheadache side. Nociception-specific
stimulation revealed a shortening of R2 onset latencies (44.3 +/- 5.4
ms for headache side vs 48.9 +/- 5.8 ms for nonheadache side) during
the acute migraine attack compared with the headache-free interval
(49.8 +/- 5.3 vs 49.8 +/- 4.5 ms). The AUC of the R2 increased on the
headache side by 680% and on the nonheadache side by 230% compared with
the headache-free interval. Drug treatment parallel to pain relief
increased the onset latencies (zolmitriptan: 48.0 +/- 8.2 ms for
headache side vs 52.3 +/- 7.6 ms for nonheadache side; lysine
acetylsalicylate: 48.0 +/- 5.0 ms for headache side vs 51.2 +/- 5.6 ms
for nonheadache side) and reduced the AUC of R2 (zolmitriptan by 45%
and lysine acetylsalicylate by 48%). CONCLUSION: The data suggest
temporary sensitization of central trigeminal neurons during acute
migraine attacks.
Publication Types:
* Clinical Trial
PMID: 11971092 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
48: Pain. 1999 Mar;80(1-2):191-200. Related Articles,
Links
Electrophysiological testing of the trigeminofacial system:
aid in the diagnosis of atypical facial pain.
Jaaskelainen SK, Forssell H, Tenovuo O.
Department of Clinical Neurophysiology, Turku University Central
Hospital, Finland. satu.jaaskelainen@tyks.fi
The aim of this study was to evaluate the yield of objective
electrophysiological testing of the trigeminofacial system in atypical
facial pain (AFP). In addition to the clinical neurological
examination, two brainstem reflexes covering both the peripheral parts
and the central connections of the trigeminal and the facial nerves,
the blink and jaw reflexes (BR and JR), were recorded in 17 AFP
patients. The control group consisted of 18 healthy volunteers with no
history of facial pain or chronic headache. The AFP patients could be
divided into three distinct groups on the basis of the clinical and
electrophysiological findings. (1) Major trigeminal neuropathy. Four
patients had clinical and electrophysiological signs of trigeminal
neuropathy (three patients with an afferent pattern of abnormal BR, and
one with absent JR on the clinically affected side) despite normal
findings in the MRI-scans of the brain. Thus, electrophysiological
testing may be more sensitive than MRI in demonstrating pathology in
some of the AFP patients. (2) Minor trigeminal neuropathy. Seven
patients had signs of increased excitability of the BR in the form of
uni- or bilaterally abnormal (diminished or absent) habituation of the
R2 component of the BR; two of these patients also showed clinical
signs of trigeminal dysfunction, but the MRI-scans were all normal.
This deficient habituation of the BR indicates increased excitability
of the BR at brainstem level in nearly 50% of our AFP patients. (3)
'Idiopathic', no signs of trigeminal neuropathy. Five patients had
normal findings both in the brainstem reflex recordings and in the
clinical examinations. Additionally, one patient had abnormal BAEP and
EEG recordings. On the group level, the AFP patients had significantly
higher thresholds of the tactile R1 component of the BR than the
control subjects. Electrophysiological testing may offer a valuable
tool for both the clinical evaluation, and the scientific study of AFP.
Publication Types:
* Clinical Trial
PMID: 10204731 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
49: Pain. 2003 Jan;101(1-2):25-32. Related Articles,
Links
Abnormal brain processing of cutaneous pain in patients with
chronic migraine.
de Tommaso M, Valeriani M, Guido M, Libro G, Specchio LM, Tonali P,
Puca F.
Department of Psychiatric and Neurological Sciences, University of
Bari, Bari, Italy. m.detommaso@neurol.uniba.it
Syndromes with chronic daily headache include chronic migraine (CM).
The reason for the transformation of migraine into chronic daily
headache is still unknown. In this study, we aimed to evaluate heat
pain thresholds and event-related potentials following CO(2)-laser
thermal stimulation (LEPS) in hand and facial regions in patients with
CM, to show changes in nociceptive brain responses related to
dysfunction of pain elaboration at the cortical level. The results were
compared with findings from normal control subjects and from subjects
who suffer from migraine without aura. The effects of stimulus
intensity, subjective pain perception and attention were monitored and
compared with features of the LEPS. Twenty-five CM patients, 15
subjects suffering from migraine without aura and 15 normal control
subjects were enrolled in the study. LEPS amplitude variation was
reduced in CM patients with respect to the perceived stimulus
intensity, in comparison with migraine without aura patients and
control subjects. In both headache groups, the distraction from the
painful laser stimulus induced by an arithmetic task failed to suppress
the LEPS amplitude, in comparison with control subjects. These results
suggest an abnormal cortical processing of nociceptive input in CM
patients, which could lead to the chronic state of pain. In both
headache groups, an inability to reduce pain elaboration during an
alternative cognitive task emerged as an abnormal behaviour probably
predisposing to migraine.
PMID: 12507697 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
50: Neurosci Lett. 2001 Sep 7;310(1):37-40. Related
Articles, Links
The blink reflex and the corneal reflex are followed by
cortical activity resembling the nociceptive potentials induced by
trigeminal laser stimulation in man.
de Tommaso M, Libro G, Guido M, Sciruicchio V, Puca F.
Interuniversity Center for the Study of Headache and Neurotransmitter
Disorders of the Central Nervous System, Perugia, Roma, Sassari, Bari,
Napoli, Firenze, Italy. m.detommaso@neurol.uniba.it
Laser stimulation of the supraorbital regions evokes brain potentials
(LEPs) related to trigeminal nociception. The aim of this study was to
record the R2 component of the blink reflex and the corneal reflex in
20 normal subjects, comparing the scalp activity following these
reflexes with the nociceptive potentials evoked by CO2 laser
stimulation of supraorbital regions. Cortical and muscular reflexes
evoked by stimulation of the first trigeminal branch were recorded
simultaneously. The R2 component of the blink reflex and the corneal
reflex were followed by two cortical peaks, which resembled
morphologically N-P waves of LEPs. The two peaks demonstrated a
difference in latency of approximately 40 ms, which is consistent with
activation time of nociception. This finding suggests that these
reflexes are induced by activation of small pain-related fibers.
Publication Types:
* Clinical Trial
PMID: 11524152 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
51: Electroencephalogr Clin Neurophysiol. 1989
Oct;73(4):285-94. Related Articles, Links
Difference of steady-state visual evoked potentials in
classic and common migraine.
Nyrke T, Kangasniemi P, Lang AH.
Department of Clinical Neurophysiology, University Central Hospital,
Turku, Finland.
The present study was designed to find evidence for the neural
hypothesis of migraine and to evaluate possible interictal differences
in the two varieties of migraine by electrophysiological means.
Steady-state visual evoked potentials (SVEPs) in response to
sinusoidally modulated light were measured in 20 patients with classic
migraine and compared with those of 30 common migraineurs and 49
reference subjects. SVEPs to stimuli at 10-24 Hz were recorded
occipitally from a pair of midline electrodes and, in classic
migraineurs and controls, additionally from left and right occipital
areas. The response was processed by the Fast Fourier Transform and
automatically analysed. The fundamental component of the midline
response to medium frequency stimuli (16-22 Hz) appeared normal in
patients with classic migraine, contrary to an augmented response in
common migraineurs (ANOVA between groups, P = 0.006). In classic
migraine the 2nd harmonic component was attenuated (P less than 0.01 at
18-20 Hz) and the amount of strong interhemispheric f1 asymmetries was
increased in about half of the patients. The groups also diverged
significantly in the SVEP dynamics during stimulation. The results
support the hypothesis of a primary neural disorder in both types of
migraine. Different sites and mechanisms of brain dysfunction in
classic and common migraine are suggested. Hypothetical neuroanatomical
correlates for the abnormalities are presented.
PMID: 2477215 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
52: Neurology. 2000;55(9 Suppl 2):S36-45. Related
Articles, Links
Functional neuroimaging: enhanced understanding of migraine
pathophysiology.
Cutrer FM, O'Donnell A, Sanchez del Rio M.
Partners Headache Center, Department of Neurology, Massachusetts
General Hospital, Boston, 02129, USA.
Research into migraine pathophysiology has been hampered by the
episodic nature and unpredictable onset of migraine attacks. Recently,
newer imaging techniques have been providing noninvasive methods of
studying metabolism and hemodynamics in the brains of migraineurs
during and between acute attacks. 133Xe blood flow techniques,
transcranial Doppler, and SPECT have all been employed to investigate
hemodynamic changes during migraine aura. PET has been useful in the
study of migraine without aura, with findings of increased blood flow
related to pain in cortical areas and in the medial brainstem.
Currently, three functional MRI imaging techniques are being used in
migraine research. Diffusion-weighted imaging has shown normal findings
in measures of the ability of neurons to maintain osmotic gradients.
Studies using perfusion-weighted imaging have shown alterations in
relative cerebral blood flow (CBF), relative cerebral blood volume, and
mean transit time during migraine visual aura. The blood oxygen
level-dependent technique can supply information related to neuronal
activation during acute migraine aura. MRS has been used with mixed
success to look for evidence of abnormal energy metabolism in the
brains of migraineurs. Magnetoencephalography studies support the
presence of a spreading depression-like phenomenon in migraine with
aura. Two groups have used transcranial magnetic stimulation to assess
whether neurons in the occipital cortex are hyperexcitable,
predisposing patients to develop aura symptoms. Despite conflicting
findings, migraine with visual aura appears to be generally associated
with transient decreases in regional CBF.
Publication Types:
* Review
* Review, Tutorial
PMID: 11089518 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
53: Indian J Physiol Pharmacol. 1998 Apr;42(2):172-88.
Related Articles, Links
Average evoked potentials--clinical applications of short
latency responses.
Tandon OP.
Department of Physiology, University College of Medical Sciences,
Shahdar, Delhi.
Many clinical neurophysiology laboratories have added average evoked
potential studies to their routine procedures as evoked potential
recording methods are non invasive, highly objective and informative.
Indeed, short latency brainstem auditory evoked potentials as well as
short and intermediate latency cortical evoked potentials, lately have
proved to be valuable clinical tools for objectively testing afferent
functions in patients with neurological and sensory disorders. The
averaged evoked potential responses (EPR) have been widely used in
clinical practice to record the changes in the electrical potentials
that occur within the central nervous system (CNS) of the patient in
response to an external stimulus. Two types of evoked potentials are
usually recorded. 1-Stimulus related, short latency evoked potentials,
which represent an obligate neuronal response to a given stimulus and
both the amplitudes and latencies of these depend on the physical
characteristics of the eliciting stimulus. In this category brainstem
auditory evoked potentials (BAEPs), visual evoked potentials (VEPs) and
somatosensory evoked potentials (SEPs), have normal values for
latencies, amplitudes of waves and characteristic wave form. Any
abnormality of these reflects excitation, conduction block in the
specific pathways in the CNS. Certain abnormalities in EPR reflect
subclinical involvement of CNS even before the disease clinically
manifests. Abnormality in BAEPs can in addition, depict the exact site
of lesion in the brainstem auditory pathways. Same is true for SEPs
where abnormalities in far-field or near-field components, reflect
lesions at the plexus, spinal cord, brainstem or thalamo-cortical
regions respectively. 2- The event related potentials (ERPs) can be
recorded in response to an external stimulus to which person is
attentive or an event requiring cognition, discrimination, or reaction
to the target stimulus. P300 is one such ERP, helpful in distinguishing
between disorders such as dementia and depression. This first review
gives a bird's eyeview of the essentials, methods, interpretation and
clinical applications of stimulus evoked short latency (brainstem
auditory, visual and somatosensory) responses in human beings.
Publication Types:
* Review
* Review, Tutorial
PMID: 10225045 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
54: Semin Neurol. 1997;17(4):335-41. Related Articles,
Links
Pathogenesis of migraine.
Welch KM.
Department of Neurology, Henry Ford Hospital and Health Sciences
Center, Detroit, Michigan 48202, USA.
Prevailing hypotheses for the mechanisms of migraine are reviewed.
Models of aura mechanisms include transient cerebral ischemia and
spreading depression. Models of headache involve trigeminovascular and
brainstem mechanisms. The ability to trigger an attack may depend on a
threshold of brain excitability. Mitochondrial disorder, magnesium
deficiency, and abnormality of presynaptic calcium channels may be
responsible for neuronal hyperexcitability between attacks. It remains
to be determined whether cortical or brainstem centers generate the
attack.
Publication Types:
* Review
* Review, Tutorial
PMID: 9474713 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
55: Acta Neurol Scand. 2001 Nov;104(5):301-7. Related
Articles, Links
Asymmetric scalp distribution of pattern visual evoked
potentials during interictal phases in migraine.
Logi F, Bonfiglio L, Orlandi G, Bonanni E, Iudice A, Sartucci F.
Department of Neuroscience, Institute of Neurology, University of Pisa,
Italy.
The N70 and P100 components of transient pattern visual evoked
potentials (P-VEPs) were measured in migraine patients, with and
without aura, and in normal subjects in order to evaluate their
latency, amplitude and occipital scalp distribution. The aim was to
find any typical electrophysiological abnormalities in migraine. P-VEP
N70 and P100 were analyzed in 59 patients without any known visual
field defect. Mean latency and amplitude values were within normal
ranges for either N70 and P100 all over the occipital scalp; the only
significant abnormality we found was related to the absolute right-left
amplitude ratio either for N70 and P100 waves, providing an asymmetry
in P-VEP scalp distribution; this finding was detected in 78.9% of
patients with aura and 72.5% without aura. Our results show that in
migraine patients, both P-VEP waves N70 and P100, have an asymmetric
topographic distribution, even during interictal phases, that can be
explained by a cortical disturbance in agreement with the neural
hypothesis of headache.
PMID: 11696025 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
56: Clin Neurophysiol. 2003 May;114(5):889-93. Related
Articles, Links
Decreased habituation of the R2 component of the blink reflex
in migraine patients.
De Marinis M, Pujia A, Natale L, D'arcangelo E, Accornero N.
Department of Neurological Sciences, La Sapienza University, Viale
dell' Universita 30, 00185 Rome, Italy. milena.demarinis@uniroma1.it
OBJECTIVE: Activation of the trigemino-vascular system as well as of
brainstem trigeminal nuclei are thought to play an important role in
migraine. The aim of this study was to investigate the habituation
phenomenon of the blink reflex in 30 headache-free migraine patients
and 30 control subjects. METHODS: An electromyographic device with a
specific habituation test program was used to elicit and record blink
reflex responses on both the right and left sides, and to randomly
repeat the stimulations at different time intervals in order to induce
habituation. RESULTS: Whereas the R1 and R2 latencies, amplitudes and
areas in the basal assessment were similar in patients and control
subjects, the blink reflex habituation responses were markedly reduced
in migraine patients who had a migraine attack within 72 h after
testing (group A). In these patients, the differences between the R2
areas, obtained when stimuli were delivered at subsequent time
intervals ranging between 10-5, 5-4, 4-3 and 3-2 s, were statistically
different (P<0.001) from those of the patients who had a migraine
attack after a longer time interval (group B) and control subjects.
CONCLUSIONS: Our data suggest that the brainstem pathways involved in
the blink reflex may be activated in the premonitory phase of migraine
attacks, probably through mechanisms that involve dopaminergic
function.
PMID: 12738435 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
57: J Neurol Sci. 2001 Mar 1;184(2):139-41. Related
Articles, Links
Visual evoked potential changes in migraine. Influence of
migraine attack and aura.
Yilmaz M, Bayazit YA, Erbagci I, Pence S.
Department of Neurology, Faculty of Medicine, Gaziantep University,
Kolejtepe, Gaziantep, Turkey.
OBJECTIVE: To assess the visual evoked potential (VEP) changes in
migraines with and without aura. STUDY DESIGN: A clinical study in
which the VEP results of 45 migraineurs (study group) and 22 healthy
volunteers (control group) were compared. Of 45 migraineurs, 29 had
migraine with aura (MA) and 16 had migraine without aura (MOA), and
they were examined both during and between the migraine attacks.
METHODS: The patients and healthy controls underwent VEP assessment. On
VEP recording, mono-ocular stimulation was performed by means of the
pattern reversal check board. The latencies of N1, P1 and N2, and the
N1--P1 amplitude were noted. The following comparisons were made
between NI, P1 and N2 latencies and N1--P1 amplitudes of the migraine
and control groups; during and between attack the VEP results of the
patients with MA and MOA. RESULTS: The VEP results of the migraineurs
and healthy controls were similar (P>0.05). The during attack
results of MA, during and between attack results of MOA, and the
results of the control group were also similar (P>0.05). N2 latency
significantly elongated in patients with MA in the attack free period
than it was during the attack (P=0.01), and was also longer than it was
in the control group (P=0.01). CONCLUSIONS: There is involvement of the
visual pathway in MA rather than MOA, and differentiation between these
subtypes of the migraine disease may be performed on the basis of VEP
findings manifesting by the prolongation of the N2 wave latency. This
contention should be confirmed by further studies.
Publication Types:
* Clinical Trial
PMID: 11239947 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
58: Int J Psychophysiol. 2002 Jun;44(3):239-49. Related
Articles, Links
Modulation of trigeminal reflex excitability in migraine:
effects of attention and habituation on the blink reflex.
de Tommaso M, Murasecco D, Libro G, Guido M, Sciruicchio V, Specchio
LM, Gallai V, Puca F.
Clinical Neurologica I Policlinico, Piazza G. Cesare II, 70124, Bari,
Italy. m.detommaso@neurol.uniba.it
The modulation of trigeminal reflex excitability in migraine patients
was evaluated during the asymptomatic phase by studying the effects of
attention, habituation and preconditioning stimulus on the R2 and R3
components of the blink reflex (BR). Fifty patients suffering from
migraine without aura, 20 affected by migraine with aura and 35 sex-
and age-matched controls were selected. In subgroups of migraine
with-aura and without-aura patients, and normal controls, the blink
reflex was elicited during different cognitive situations: (a)
spontaneous mental activity; (b) stimulus anticipation; (c) recognition
of target numbers. In the remaining subjects, R2 and R3 habituation was
evaluated by repetitive stimulation at 1, 5, 10, 15, 20, 25 and 30 s
intervals. The R2 and R3 recovery curves were also computed. A reduced
R3 threshold with a normal pain threshold was found in migraine
with-aura and without-aura patients; the R3 component was not
significantly correlated with the pain thresholds in patients and
controls. The R2 and R3 components were less influenced by the warning
of the stimulus in migraine without-aura and migraine with-aura
patients, in comparison with the control group. A slight increase of
both R2 and R3 recovery after preconditioning stimulus was also
observed in migraine patients, probably caused by a phenomenon of
trigeminal hyperexcitability persisting after the last attack. The
abnormal BR modulation by alerting expresses in migraine a dysfunction
of adaptation capacity to environmental conditions, probably
predisposing to migraine.
PMID: 12031298 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
59: J Neurol Neurosurg Psychiatry. 1988 Jan;51(1):43-9.
Related Articles, Links
Argon laser induced single cortical responses: a new method
to quantify pre-pain and pain perceptions.
Bjerring P, Arendt-Nielsen L.
Department of Dermatology, Marselisborg Hospital, Aarhus, Denmark.
The shape (amplitude and latency) of single cortical responses to argon
laser stimulation was found to match six perceptual classes: three
pre-pain and three pain. The amplitude of the pain related single
cortical responses correlated with the perceived feeling of pain. Easy
detectable responses were obtained because habituation to the stimuli
was reduced and a high degree of attention was given to each stimulus.
Single cortical responses to argon laser stimuli are suggested as a new
quantitative technique with application in the assessment of function
in the thermal and nociceptive pathways.
PMID: 3351530 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
60: Headache. 2001 Jun;41(6):565-72. Related Articles,
Links
Visual cortex excitability in migraine with and without aura.
Mulleners WM, Chronicle EP, Palmer JE, Koehler PJ, Vredeveld JW.
Departments of Neurology, Atrium Medical Center, Heerlen, The
Netherlands.
OBJECTIVES: Previous research using transcranial magnetic stimulation
has produced equivocal findings concerning thresholds for the
generation of visual phosphenes in migraine with aura. These studies
were methodologically varied and did not systematically address
cortical excitability in migraine without aura. We therefore studied
magnetophosphene thresholds in both migraine with aura and migraine
without aura compared with headache-free controls. METHODS: Sixteen
subjects with migraine with aura and 12 subjects with migraine without
aura were studied and compared with 16 sex- and age-matched controls.
Using a standardized transcranial magnetic stimulation protocol of the
occipital cortex, we assessed the threshold stimulation intensity at
which subjects just perceived phosphenes via a method of alternating
course and fine-tuning of stimulator output. RESULTS: There were no
significant differences across groups in the proportion of subjects
seeing phosphenes. However, the mean threshold at which phosphenes were
reported was significantly lower in both migraine groups (migraine with
aura=47%, migraine without aura=46%) than in controls (66%). Moreover,
there was no significant correlation between individual phosphene
threshold and the time interval to the closest migraine attack.
CONCLUSION: Our findings confirm that the occipital cortex is
hyperexcitable in the migraine interictum, both in migraine with and
without aura.
PMID: 11437892 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
61: Can J Neurol Sci. 1984 Feb;11(1):60-3. Related
Articles, Links
Electrophysiological studies in five cases of
abetalipoproteinemia.
Lowry NJ, Taylor MJ, Belknapp W, Logan WJ.
Auditory brainstem responses (ABRs), visual and somatosensory evoked
responses (VEPs and SEPs) and nerve conduction studies were conducted
in 5 patients with abetalipoproteinemia. The ABRs were normal in all
cases. The VEPs were of normal amplitude but of increased latencies in
two patients. The four eldest patients had delayed cortical SEPs but
normal peripheral sensory nerve conduction studies. The peripheral
motor conduction velocities were normal in all cases. The peripheral
sensory studies showed normal velocity when a response was seen;
however, the amplitude of the response was often reduced or it was
absent. The electrophysiological studies reported here support a model
of axonal loss of large myelinated fibres with secondary demyelination
in abetalipoproteinemia.
PMID: 6704795 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
62: Muscle Nerve. 1999 Apr;22(4):508-16. Related
Articles, Links
Assessment of trigeminal small-fiber function: brain and
reflex responses evoked by CO2-laser stimulation.
Cruccu G, Romaniello A, Amantini A, Lombardi M, Innocenti P, Manfredi
M.
Dipartimento Scienze Neurologiche, Viale Universita 30, Roma, Italy.
Laser pulses selectively excite mechano-thermal nociceptors and evoke
brain potentials that may reveal small-fiber dysfunction. We applied
CO2-laser pulses to the perioral and supraorbital regions and recorded
the scalp laser-evoked potentials (LEPs) and reflex responses in the
orbicularis oculi, masticatory, and neck muscles in 30 controls and 10
patients with facial sensory disturbances. Low-intensity pulses readily
evoked scalp potentials consisting of a negative component with a
latency of 165 ms followed by a positive component at 250 ms. In vertex
recordings, the amplitude of LEPs exceeded 30 microV. Although only
high-intensity pulses evoked reflex responses, some subjects
showed--even to low-intensity pulses--an orbicularis oculi (blink-like)
response that markedly contaminated the scalp recording. Scalp LEPs
were abnormal in patients with hypalgesia and normal trigeminal
reflexes and normal in patients with normal pain sensitivity and
abnormal trigeminal reflexes. Possibly because of the high receptor
density in this area and the short conduction distance, laser
stimulation of the trigeminal territory yields low-threshold and large
LEPs, which are useful for detecting dysfunction in peripheral and
central pain pathways.
PMID: 10204787 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
63: Headache. 1992 Jul;32(7):345-7. Related Articles,
Links
Menstrual migraine without aura: cortical excitability to
magnetic stimulation.
Bettucci D, Cantello R, Gianelli M, Naldi P, Mutani R.
Department of Neurology, University School of Medicine of Novara,
Italy.
The purpose of the present study was the evaluation of the excitability
threshold and the central motor conduction time (CCT) studied by means
of electromagnetic cortical stimulation in ten subjects affected by
menstrual migraine without aura, both in the ictal and the interictal
period. The patients were chosen from among a group of 254 outpatients
affected by migraine, diagnosed according to the International Headache
Society criteria. The control group consisted of ten healthy female
subjects. As far as CCTs were concerned no differences emerged between
patients and controls. However in the patient group we found a
significant increase in the excitability threshold values, both in the
ictal and the interictal period, and in both hemispheres. If confirmed,
the increased excitability threshold may be a useful neurophysiological
correlate of migraine without aura.
PMID: 1526765 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
64: Cephalalgia. 1999 Jun;19(5):485-91. Related
Articles, Links
Comment in:
* Cephalalgia. 1999 Jun;19(5):477.
Dynamic changes of cognitive habituation and serotonin
metabolism during the migraine interval.
Evers S, Quibeldey F, Grotemeyer KH, Suhr B, Husstedt IW.
Department of Neurology, University of Munster, Germany.
everss@uni-muenster.de
Migraine patients show a specific cognitive processing with a loss of
habituation in the interval and a normal habituation in the attack as
measured by event-related potentials (ERPs). It is unknown whether the
loss of habituation changes during the migraine interval or is a stable
state. Serotonin (5HT) metabolism is involved in the pathophysiology of
migraine and also in the generation of ERPs. We enrolled 14 patients
with regular migraine attacks in order to measure visually evoked ERPs
repetitively during the migraine interval and in the migraine attack.
Cognitive habituation was evaluated by analysis of P3 latency. Platelet
serotonin content and free serotonin plasma level were measured at the
same time points. The loss of habituation increased continuously during
the migraine interval and abruptly normalized in the migraine attack (p
< 0.05, time series analysis). The platelet 5HT content decreased
significantly in the migraine attack (p < 0.03) and was at its
maximum in the middle of the interval. The P3 latency was significantly
increased in the attack (p < 0.01) and was significantly inversely
correlated with the platelet 5HT content (r = -0.44, p < 0.001).
Free 5HT plasma levels did not show any significant change. Our
findings suggest that loss of cognitive habituation continuously
increases during the migraine interval until its normalization in the
migraine attack. This phenomenon cannot be attributed to serotonergic
transmission. In patients with regular changes of cognitive habituation
before the migraine attack, it might be possible to predict the attack
by analysing ERPs.
PMID: 10403063 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
65: Cephalalgia. 1990 Dec;10(6):317-29. Related
Articles, Links
Event-related slow potentials and associated catecholamine
function in migraine.
Nagel-Leiby S, Welch KM, D'Andrea G, Grunfeld S, Brown E.
Department of Neurology, Henry Ford Hospital, Detroit, MI 48202.
Plasma norepinephrine and dopamine and event-related slow potentials
were measured at menses and ovulation in migraine with and without aura
relative to normal subjects. The results indicated that at menses, but
not ovulation, plasma dopamine was increased and norepinephrine was
decreased relative to normal. This catecholamine imbalance was greater
in migraine without aura than in migraine with aura. Conversely,
event-related slow potentials measured over the posterior cortex at
ovulation but not at the menses was altered relative to normal. Early
epoch negativity was reduced in migraine with aura, whereas late epoch
negativity was reduced in migraine without aura. The results suggested
that (a) migraine without aura may involve dynamic shifts in the
function of both norepinephrine and dopamine responsive neurons; (b)
pathophysiology of migraine with aura is less dependent on
catecholamine imbalance (norepinephrine alone affected); (c) these
pathophysiological mechanisms are most prevalent in or restricted to
posterior cortical regions but may be modulated by brainstem
mechanisms.
PMID: 2289233 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
66: J Physiol. 2002 Apr 15;540(Pt 2):623-33. Related
Articles, Links
Modulation of human corticomotor excitability by
somatosensory input.
Kaelin-Lang A, Luft AR, Sawaki L, Burstein AH, Sohn YH, Cohen LG.
Human Cortical Physiology Section, NINDS, National Institutes of
Health, Bethesda, MD 20892, USA.
In humans, somatosensory stimulation results in increased
corticomotoneuronal excitability to the stimulated body parts. The
purpose of this study was to investigate the underlying mechanisms. We
recorded motor evoked potentials (MEPs) to transcranial magnetic
stimulation (TMS) from abductor pollicis brevis (APB), first dorsal
interosseous (FDI), and abductor digiti minimi (ADM) muscles. MEP
amplitudes, recruitment curves (RC), intracortical inhibition (ICI),
intracortical facilitation (ICF), resting (rMT) and active motor
thresholds (aMT) were recorded before and after a 2-h period of ulnar
nerve electrical stimulation at the wrist. Somatosensory input was
monitored by recording somatosensory evoked potentials. To
differentiate excitability changes at cortical vs. subcortical sites,
we recorded supramaximal peripheral M-responses and MEPs to brainstem
electrical stimulation (BES). In order to investigate the involvement
of GABAergic mechanisms, we studied the influence of lorazepam (LZ) (a
GABA(A) receptor agonist) relative to that of dextromethorphan (DM) (an
NMDA receptor antagonist) and placebo in a double-blind design. We
found that somatosensory stimulation increased MEP amplitudes to TMS
only in the ADM, confirming a previous report. This effect was blocked
by LZ but not by either DM or placebo and lasted between 8 and 20 min
in the absence of (i) changes in MEPs elicited by BES, (ii) amplitudes
of early somatosensory-evoked potentials or (iii) M-responses. We
conclude that somatosensory stimulation elicited a focal increase in
corticomotoneuronal excitability that outlasts the stimulation period
and probably occurs at cortical sites. The antagonistic effect of LZ
supports the hypothesis of GABAergic involvement as an operating
mechanism.
Publication Types:
* Clinical Trial
PMID: 11956348 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
67: Neurology. 1999 Mar 23;52(5):1044-9. Related
Articles, Links
Physiology of perception: cortical stimulation and recording
in humans.
Ray PG, Meador KJ, Smith JR, Wheless JW, Sittenfeld M, Clifton GL.
Department of Neurology, Medical College of Georgia, Augusta 30912,
USA.
OBJECTIVES: 1) To determine the effect of stimulus train duration (TD)
on sensory perception using direct stimulation of somatosensory and
visual cortices. 2) To investigate the occurrence of evoked potentials
in response to stimulation that is subthreshold for perception.
BACKGROUND: Studies of the mechanisms of conscious perception using
direct cortical stimulation and recording techniques are rare. The
clinical necessity to implant subdural electrode grids in epilepsy
patients undergoing evaluation for surgery offers an opportunity to
examine the role of stimulus parameters and evoked potentials in
conscious perception. METHODS: Subjects included epilepsy patients with
grids over somatosensory or occipital cortex. Single pulses (100
microseconds) and stimulus trains were applied to electrodes, and
thresholds for perception were found. Evoked potentials were recorded
in response to peripheral stimulation at intensities at, above, and
below sensory threshold. RESULTS: During cortical stimulation, sensory
threshold changed little for stimulus trains of 250 milliseconds and
longer, but increased sharply as TD decreased below this level. Primary
evoked activity was recorded in response to peripheral stimulations
that were subthreshold for conscious perception. CONCLUSIONS: The
results confirm a previous report of the effects of stimulus TD on
sensory threshold. However, no motor responses occurred following
somatosensory stimulation with short trains, as previously reported.
The TD threshold pattern was similar in visual cortex. In agreement
with the previous report, early components of the primary evoked
response were not correlated with conscious sensory awareness.
PMID: 10102426 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
68: J Clin Neurophysiol. 2002 Aug;19(4):294-306.
Related Articles, Links
Transcranial magnetic stimulation and epilepsy.
Macdonell RA, Curatolo JM, Berkovic SF.
Department of Neurology, Austin & Repatriation Medical Centre,
Heidelberg, Victoria, Australia. rmac@austin.unimelb.edu.au
Transcranial magnetic stimulation has been used to study generalized
and focal epilepsies for more than a decade. The technique appears safe
and has yielded important information about the mechanisms underlying
epilepsy. Transcranial magnetic stimulation findings differ depending
on the epilepsy syndrome, lending support to the concept that there are
distinct pathophysiologies underlying each condition. In most studies
of generalized epilepsies, transcranial magnetic stimulation has
indicated a state of relative hyperexcitability of excitatory cortical
interneurons and possibly inhibitory interneurons as well, which can be
reversed through the actions of anticonvulsant medications.
Transcranial magnetic stimulation studies in patients with a seizure
focus in the motor cortex indicate increased cortical excitability and
reduced inhibition, but in patients with seizure foci located elsewhere
the findings are similar to those in generalized epilepsies.
Transcranial magnetic stimulation has also been used to study the mode
of action of anticonvulsants and may prove to be a useful means of
testing the potential for new drugs to act as anticonvulsants.
Repetitive transcranial magnetic stimulation may prove to have a
therapeutic role by producing long-lasting cortical inhibition after a
train of impulses.
Publication Types:
* Review
* Review, Tutorial
PMID: 12436086 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
69: Appl Psychophysiol Biofeedback. 2002
Sep;27(3):203-13. Related Articles, Links
On the pathophysiology of migraine--links for "empirically
based treatment" with neurofeedback.
Kropp P, Siniatchkin M, Gerber WD.
Institute of Medical Psychology, University of Kiel, Niemannsweg 147,
D-24105 Kiel, Germany. kropp@med-psych.uni-kiel.de
Psychophysiological data support the concept that migraine is the
result of cortical hypersensitivity, hyperactivity, and a lack of
habituation. There is evidence that this is a brain-stem related
information processing dysfunction. This cortical activity reflects a
periodicity between 2 migraine attacks and it may be due to endogenous
or exogenous factors. In the few days preceding the next attack slow
cortical potentials are highest and habituation delay experimentally
recorded during contingent negative variation is at a maximum. These
striking features of slow cortical potentials are predictors of the
next attack. The pronounced negativity can be fed back to the patient.
The data support the hypothesis that a change in amplitudes of slow
cortical potentials is caused by altered habituation during the
recording session. This kind of neurofeedback can be characterized as
"empirically based" because it improves habituation and it proves to be
clinically efficient.
Publication Types:
* Review
* Review, Tutorial
PMID: 12206051 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
70: Cephalalgia. 1999 Oct;19(8):718-24; discussion
697-8. Related Articles, Links
Personality and response to repeated visual stimulation in
migraine and tension-type headaches.
Wang W, Wang GP, Ding XL, Wang YH.
Anhui Institute of Stereotactic Neurosurgery, Hefei, China.
wang_wei@mail.hf.ah.cn
Migraine sufferers potentiate their visual evoked potentials (VEPs)
from a short period of 2 min to a longer period of 15 min. As a lack of
habituation is linked to higher level arousal, we thus hypothesized
that short-term VEP potentiation might be correlated with an
arousal-related personality trait. We therefore carried out short-term
VEPs, Plutchik-van Praag's Depression Inventory, Zuckerman's
Sensation-Seeking Scales (Form V), and Zuckerman-Kuhlman's Personality
Questionnaire in 26 healthy subjects, 22 patients suffering from
migraine without aura between attacks, 13 episodic and 20 chronic
tension-type headaches. The chronic tension-type headache sufferers
showed increased depression compared with other groups, which might be
a consequence of the headache itself. Migraines, however, showed
steeper habituation slopes of N1-P1 and P1-N2, decreased thrill and
adventure-seeking, and general sensation-seeking than healthy controls;
in addition, the habituation slope of P1-N2 was positively correlated
with experience-seeking in migraine. The short-term VEP potentiation
and the decreased thrill and adventure-seeking and general
sensation-seeking in migraine might be related to a high level of
cortical arousal and a low 5HT neurotransmission. In compliance with
the long-term VEP study, the positive correlation between the P1-N2
habituation slope and experience-seeking in migraine suggests a
continuous metabolic overload for the brain interictally, which can
trigger the activation of a migraine attack.
Publication Types:
* Clinical Trial
* Controlled Clinical Trial
PMID: 10570726 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
71: J Neurol Neurosurg Psychiatry. 1987
Apr;50(4):416-22. Related Articles, Links
Laterality of pain in migraine distinguished by interictal
rates of habituation of electrodermal responses to visual and auditory
stimuli.
Gruzelier JH, Nicolaou T, Connolly JF, Peatfield RC, Davies PT,
Clifford-Rose F.
Support is provided for a primary neural factor in migraine by studies
in autonomic responsiveness to sensory stimuli in relation to the
laterality of pain. Migraineurs with consistently lateralised headaches
were found in two studies to exhibit extremes of autonomic
responsiveness to sensory stimuli during the interictal phase. The
direction of responsiveness was predictive of the laterality of pain;
left-sided pain was associated with under-responsiveness and fast
habituation, right-sided pain with over-responsiveness and slow
habituation. Bipolarity in rate of habituation is consistent with a
defect in a regulatory mechanism that controls regional cerebral
activation such as the diffuse thalamic projection system.
PMID: 3585352 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
72: Brain Res Cogn Brain Res. 2003 May;16(3):488-91.
Related Articles, Links
Reductions in CI amplitude after repetitive transcranial
magnetic stimulation (rTMS) over the striate cortex.
Schutter DJ, van Honk J.
Affective Neuroscience Section, Helmholtz Research Institute, Utrecht
University, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands.
d.schutter@fss.uu.nl
Slow repetitive transcranial magnetic stimulation (rTMS) is a method
capable of transiently inhibiting cortical excitability and disrupting
information processing in the visual system. This method can be used to
topographically map the functional contribution of different cortical
brain areas in visual processing. An early electrophysiological
component, the CI is argued to reflect early visual processing. In
addition, source-localization studies have provided evidence for the
assumption that the striate cortex is the underlying neural generator
of CI. In the present placebo-controlled, crossover study, slow rTMS
was applied in order to further investigate the relationship between
the striate cortex and the CI component. Based on the inhibitory
effects of slow rTMS, a reduction in CI amplitude and an increase in
latency were expected. Compared to placebo stimulation, slow rTMS over
the striate cortex resulted in significant decreases of the CI
amplitude, but did not affect latency. The present study provides
causal evidence for the involvement of the striate cortex in generating
the CI component.
Publication Types:
* Clinical Trial
PMID: 12706228 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
73: Electromyogr Clin Neurophysiol. 1995
Jun-Jul;35(4):251-6. Related Articles, Links
Effects of visual and auditory stimuli on median nerve
somatosensory evoked potentials in man.
Okajima Y, Chino N, Takahashi M, Kimura A.
Department of Rehabilitation Medicine, Keio University School of
Medicine, Tokyo, Japan.
To demonstrate electrophysiological evidence of neural connections of
somatosensory with visual and auditory pathways, interactions of median
nerve somatosensory evoked potentials (SEPs) with visual evoked
potentials (VEPs) and auditory evoked potentials (AEPs) were analyzed
in 12 healthy subjects. In Experiment I (SEP vs. VEP), three patterns
of stimulation, namely, electric stimulation of left median nerve,
binocular LED flash, and simultaneous electric and flash stimulation,
were applied with random interstimulus intervals of 2-4 sec until more
than 100 responses had been obtained and averaged for each pattern of
stimulation. Simultaneous electric and visual responses were subtracted
from arithmetical sums of SEPs and VEPs to show interactions between
somatosensory and visual responses. In Experiment II (SEP vs. AEP),
binaural short-duration tone bursis instead of LED flashes were used in
the same manner as in Experiment I, and interactions between
somatosensory and auditory responses were analyzed. Results indicated
that the effects of both visual and auditory interaction on SEPs were
significant around 120-130 msec of latency. In other words, cross-modal
sensory interaction occurred in the late phase of sensory processing.
PMID: 7555931 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
74: Neurosci Lett. 2000 Feb 4;279(3):153-6. Related
Articles, Links
Different generators in human temporal-parasylvian cortex
account for subdural laser-evoked potentials, auditory-evoked
potentials, and event-related potentials.
Lenz FA, Krauss G, Treede RD, Lee JL, Boatman D, Crone N, Minahan R,
Port J, Rios M.
Department of Neurosurgery, Johns Hopkins Hospital, Baltimore, MD
21287-7713, USA. fal@pallidum.med.jhu.edu
In order to localize cortical areas mediating pain we now report
subdural cortical potentials evoked by auditory stimulation
(auditory-evoked potentials - AEPs) and by cutaneous stimulation with a
laser (laser-evoked potentials - LEPs). Stimulation with the laser
evokes a pure pain sensation by selective activation of nociceptors.
LEPs were maximal over the inferior aspect of the central sulcus and
had the same polarity on either side of the sylvian fissure. AEPs were
maximal posterior to the LEP maximum and had opposite polarity on
opposite sides of the sylvian fissure, consistent with the location of
a known generator in the temporal operculum. Auditory P3
(event-related) potentials were maximal over the temporal base. These
findings demonstrate that the LEP generator is not in secondary
somatosensory cortex on the parietal operculum and is different from
the P3 generator.
PMID: 10688052 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
75: Rev Neurol. 1998 Dec;27(160):955-63. Related
Articles, Links
[Electrophysiological characteristics of asymptomatic
relatives of patients with type 2 spinocerebellar ataxia]
[Article in Spanish]
Velazquez L, Medina EE.
Laboratorio de Neurofisiologia Clinica, Hospital Docente Provincial
Vladimir Ilich Lenin, Holguin, Cuba.
INTRODUCTION: Electrophysiological studies have been shown to be useful
in hereditary ataxia, but only a small number of patients have been
studied, and the duration of the illness, serial studies and molecular
definition have not been taken into account. OBJECTIVE: We proposed, by
means of electrophysiological techniques, to characterize the
functional evolutionary state of the afferent and efferent systems in
asymptomatic relations of patients with type 2 spinocerebellar ataxia
(SCA2). Patients and methods. A 10 year longitudinal, prospective study
was made of 59 children of patients with SCA2. The sequence included
four studies: 1986, 1991, 1994 and 1996, all with informed consent for
the investigation. The control group consisted of 108 volunteers. The
electrophysiological studies recorded were: conduction studies in
peripheral nerves and multimodal evoked potentials. For statistical
analysis multivariate methods were used with a confidence interval of
95% (alpha = 0.05). RESULTS: Electrophysiological alterations were
observed even in the absence of clinical signs, such as reduced
amplitude of sensory potentials, morphological changes and prolonged
latency of the central components of somatosensory evoked potentials,
and of brain stem auditory evoked potentials, whilst the visual evoked
potentials remained normal. Of 79 relations studied during the 10 year
investigation, 17 had clinical signs and were considered to be patients
with SCA2. CONCLUSIONS: Four stages of the illness were defined:
'healthy', presymptomatic, and patients with and without nerve
conduction block. These characterized the degenerative mechanisms of
the afferent and efferent systems of the relations of patients with
SCA2 who became ill themselves.
PMID: 9951012 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
76: Headache. 2001 Sep;41(8):792-7. Related Articles,
Links
Spectral analysis of visual potentials evoked by
pattern-reversal checkerboard in juvenile patients with headache.
Marrelli A, Tozzi E, Porto C, Cimini N, Aloisi P, Valenti M.
Unita Operativa di Neurofisiopatologia, Ospedale S. Salvatore-Coppito;
Clinica Pediatrica, Universita di L'Aquila, L'Aquila, Italy.
Changes in visual evoked potentials, mainly affecting the amplitude of
the major positive wave, are referred to by many authors and are
related to the pathophysiological basis of primary headache. We
performed both transient pattern-reversal visual evoked potentials and
spectral analysis by means of fast Fourier transform of 8-Hz
steady-state pattern-reversal visual evoked potentials in 34 children
affected with migraine (14 with aura, 20 without aura), and compared
them with 14 patients with tension-type headache and 10 healthy
subjects. The amplitude of the response to the transient stimulation
(P100) was higher and the latency shorter in the patients with headache
compared with the controls, but the difference was not statistically
significant. The absolute power of the first harmonic (1F) obtained by
the spectral analysis of the steady-state stimulation was increased in
all the patients with headache compared with the controls, and the
increase was significant in patients with migraine. These data seem to
confirm the hypothesis of abnormal processing of visual input in
migraineurs and could be interpreted as neurophysiological support for
the theory that different headache types are related conditions.
Furthermore, the spectral analysis of steady-state pattern-reversal
visual evoked potentials could be proposed as a test to diagnose
migraine.
PMID: 11576204 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
77: Muscle Nerve. 2000 Mar;23(3):321-35. Related
Articles, Links
Electrophysiological studies of myoclonus.
Shibasaki H.
Departments of Neurology and Brain Pathophysiology, Kyoto University
School of Medicine, Shogoin, Sakyo, Kyoto, 606-8507 Japan.
As myoclonus is often associated with abnormally increased excitability
of cortical structures, electrophysiological studies provide useful
information for its diagnosis and classification and about its
generator mechanisms. The EEG-EMG polygraph provides the most essential
information about the myoclonus of interest. Jerk-locked back averaging
and evoked potential studies combined with recording of the long
latency, long loop reflexes are useful to further investigate the
pathophysiology of myoclonus, especially that of cortical myoclonus. A
recent advance in magnetoencephalographic techniques has contributed
significantly to the elucidation of some of the cortical mechanisms
underlying myoclonus. Elucidation of physiological mechanisms
underlying myoclonus in each individual patient is important for
selecting the most appropriate treatment of choice. Copyright 2000
American Association of Electrodiagnostic Medicine.
Publication Types:
* Review
* Review Literature
PMID: 10679708 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
78: Klin Wochenschr. 1988;66 Suppl 14:1-10. Related
Articles, Links
[Evoked potentials and intravenous anesthetics]
[Article in German]
Kochs E, Schulte am Esch J.
Abteilung fur Anasthesiologie, Universitatskrankenhaus Eppendorf,
Hamburg.
In contrast to the electroencephalogram, which is a collection of the
spontaneous brain electrical potentials generated by the cerebral
cortex, evoked potentials are the electrical signals generated by the
nervous system in response to brief extrinsic sensory stimuli. They can
be used to establish objective evidence of an abnormality when clinical
signs and symptoms are equivocal. Moreover they prove useful to define
the anatomical level of lesions in the afferent pathway tested. They
have been successfully applied during anesthesia and operations when
pathways amenable to evoked potential recording were at risk. The most
practical techniques in common intraoperative evoked response
monitoring involve stimulation of visual, auditory and somatosensory
pathways. As could be clearly demonstrated alterations of evoked
responses can not only be found with diminished regional blood flow but
in a graded manner depend on the used anesthetics as well. The
potential application of evoked responses to monitor depth of
anesthesia has been demonstrated by several groups. In contrast to
visual, auditory and somatosensory cortical evoked potentials which
show a large inter- and intraindividual variance acoustical evoked
brainstem and somatosensory evoked subcortical potentials are very
robust under general anesthesia. Drug-induced effects on shape,
amplitude and latencies of evoked responses during balanced anesthesia
must be well documented in order to establish evoked responses as
sensitive indicators of systemic problems that may threaten the
viability of the central nervous system. There is evidence that the
effects on evoked responses during deep anesthetic states can be
mimicked by several life-threatening conditions (e.g.: hypoxia,
ischemia). This review describes the effects of intravenously used
anesthetic drugs on visual, auditory and somatosensory evoked
potentials and the alterations in evoked responses by abnormal systemic
conditions as seen under hypotension, hypoxia, ischemia.
Publication Types:
* Review
* Review, Tutorial
PMID: 3292821 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
79: Brain. 2001 Nov;124(Pt 11):2310-8. Related
Articles, Links
Increased visual after-effects following pattern adaptation
in migraine: a lack of intracortical excitation?
Shepherd AJ.
School of Psychology, Birkbeck College, London, UK.
a.shepaerd@psychology.bbk.ac.uk
Much research on visual function in migraine has examined early aspects
of visual processing, often using detection or discrimination measures
and stimuli reported to trigger an attack, e.g. striped patterns or
flickering lights. Differences between people with and without migraine
have been attributed to abnormal cortical processing in migraine,
variously described by interictal hyperexcitability, heightened
responsiveness, a lack of habituation and/or a lack of intra-cortical
inhibition. Here, two experiments are presented that explore a uniquely
cortical phenomenon, pattern or contrast adaptation, one using the
motion after-effect, one the tilt after-effect. Pattern adaptation
reflects specific interactions between groups of neurones and is
therefore ideally suited to address proposed models of cortical
function in migraine. These models lead to specific predictions in an
adaptation study: there should be smaller effects in people with
migraine than in people without. The results from both adaptation
experiments, however, revealed larger effects in migraine sufferers
than in headache-free control subjects. There were no differences
between migraine subgroups classified according to the presence or
absence of aura. These results are discussed in terms of models of
cortical function in migraine.
Publication Types:
* Clinical Trial
* Randomized Controlled Trial
PMID: 11673331 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
80: Neurolog. 2001 Sep;7(5):279-86. Related Articles,
Links
The pathophysiology of migraine.
Tepper SJ, Rapoport A, Sheftell F.
New England Center for Headache, Stamford, Connecticut, Department of
Neurology, Yale University School of Medicine, New Haven, Connecticut,
and Department of Psychiatry, New York Medical College, New York, New
York E-mail: sjtepper@aol.com
BACKGROUND: Migraine results from episodic changes in central nervous
system physiologic function in hyperexcitable brain manifested by
abnormal energy metabolism, lowered threshold for phosphene generation,
and increased contingent negative variation. Human functional magnetic
resonance imaging and magnetoencepholography data strongly suggest that
aura is caused by cortical spreading depression. REVIEW SUMMARY: Brain
hyperexcitability may be caused by low magnesium levels, mitochondrial
abnormalities with abnormal phosphorylation of adenosine
5'-diphosphate, a dysfunction related to nitric oxide, or calcium
channelopathy. Low magnesium can result in opening of calcium channels,
increased intracellular calcium, glutamate release, and increased
extracellular potassium, which may in turn trigger cortical spreading
depression. Mitochondrial dysfunction has been suggested by a low
phosphocreatine:Pi ratio and a possible response by migraine patients
to riboflavin prophylaxis. Nitroglycerine administration results in a
delayed migraine-like headache in migraine patients but not in control
patients, and a nonspecific nitric oxide synthase inhibitor aborted
migraine at 2 hours in the majority of tested migraine patients
compared to controls. Many patients with familial hemiplegic migraine
have a missense mutation in the P/Q calcium channel, so that this form
of migraine, at least, is associated with a demonstrable calcium
channelopathy. CONCLUSIONS: The generation of migraine occurs centrally
in the brain stem, sometimes preceded by cortical spreading depression
and aura. Activation of the trigeminovascular system stimulates
perivascular trigeminal sensory afferent nerves with release of
vasoactive neuropeptides, resulting in vasodilation and transduction of
central nociceptive information. There is then a relay of pain impulses
to central second- and third-order neurons and activation of brain stem
autonomic nuclei to induce associated symptoms.
PMID: 12803669 [PubMed]
------------------------------------------------------------------------
81: Neuroscience. 2003;119(2):597-609. Related
Articles, Links
Electrophysiological evidence for the existence of a
posterior cortical-prefrontal-basal forebrain circuitry in modulating
sensory responses in visual and somatosensory rat cortical areas.
Golmayo L, Nunez A, Zaborszky L.
Department of Morphology, School of Medicine, Autonomous University of
Madrid, Madrid, Spain.
The prefrontal cortex (PFC) receives input from sensory neocortical
regions and sends projections to the basal forebrain (BF). The present
study tested the possibility that pathways from sensory cortical
regions via the PFC-BF and from the BF back to specific sensory
cortical areas could modulate sensory responses. Two prefrontal areas
that responded to stimulation of the primary somatosensory and visual
cortices were delineated: an area encompassing the rostral part of the
cingulate cortex that responded to visual cortex stimulation, and a
region dorso-lateral to the first in the precentral-motor association
area that reacted to somatosensory cortex stimulation. Moreover, BF
neurons responded to PFC electrical stimulation. They were located in
the ventral pallidum, substantia innominata and the horizontal limb of
the diagonal-band areas. Of the responsive BF neurons 42% reacted only
to stimulation of 'visually-responsive,' 33% responded only to the
'somatosensory-responsive' prefrontal sites and the remaining neurons
reacted to both prefrontal cortical areas. The effect of BF and PFC
stimulations on somatosensory and visual-evoked potentials was tested.
BF stimulation increased the amplitude of both sensory-evoked
potentials. However, stimulation of the 'somatosensory-responsive'
prefrontal area increased only somatosensory-evoked potentials while
'visually-responsive' prefrontal-area stimulation increased only
visual-evoked potentials. Atropine blocked both facilitatory
effects.The proposed cortico-prefronto-basalo-cortical circuitry may
have an important role in cortical plasticity and selective attention.
PMID: 12770572 [PubMed - in process]
------------------------------------------------------------------------
82: Crit Rev Oral Biol Med. 2000;11(1):57-91. Related
Articles, Links
Acute and chronic craniofacial pain: brainstem mechanisms of
nociceptive transmission and neuroplasticity, and their clinical
correlates.
Sessle BJ.
Faculty of Dentistry, University of Toronto, Ontario, Canada.
This paper reviews the recent advances in knowledge of brainstem
mechanisms related to craniofacial pain. It also draws attention to
their clinical implications, and concludes with a brief overview and
suggestions for future research directions. It first describes the
general organizational features of the trigeminal brainstem sensory
nuclear complex (VBSNC), including its input and output properties and
intrinsic characteristics that are commensurate with its strategic role
as the major brainstem relay of many types of somatosensory information
derived from the face and mouth. The VBSNC plays a crucial role in
craniofacial nociceptive transmission, as evidenced by clinical,
behavioral, morphological, and electrophysiological data that have been
especially derived from studies of the relay of cutaneous nociceptive
afferent inputs through the subnucleus caudalis of the VBSNC. The
recent literature, however, indicates that some fundamental differences
exist in the processing of cutaneous vs. other craniofacial nociceptive
inputs to the VBSNC, and that rostral components of the VBSNC may also
play important roles in some of these processes. Modulatory mechanisms
are also highlighted, including the neurochemical substrate by which
nociceptive transmission in the VBSNC can be modulated. In addition,
the long-term consequences of peripheral injury and inflammation and,
in particular, the neuroplastic changes that can be induced in the
VBSNC are emphasized in view of the likely role that central
sensitization, as well as peripheral sensitization, can play in acute
and chronic pain. The recent findings also provide new insights into
craniofacial pain behavior and are particularly relevant to many
approaches currently in use for the management of pain and to the
development of new diagnostic and therapeutic procedures aimed at
manipulating peripheral inputs and central processes underlying
nociceptive transmission and its control within the VBSNC.
Publication Types:
* Review
* Review, Academic
PMID: 10682901 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
83: Brain. 1998 Feb;121 ( Pt 2):281-91. Related
Articles, Links
Somatosensory-evoked blink response: investigation of the
physiological mechanisms.
Miwa H, Nohara C, Hotta M, Shimo Y, Amemiya K.
Department of Neurology, Juntendo University School of Medicine, Tokyo,
Japan.
The somatosensory-evoked blink response (SBR) is a newly identified
blink reflex elicited by electrical stimulation of peripheral nerves.
The present study was performed to investigate the physiological
mechanism underlying the SBR elicited by median nerve stimulation in
normal subjects. The peripheral afferents responsible for the SBR
included low-threshold cutaneous fibres. In the SBR-positive subjects,
the late (R2) component of the blink reflex elicited by supraorbital
nerve stimulation and the SBR facilitated each other when both
responses were induced at the same time, but they each caused
long-lasting inhibition in the other when one stimulus was given as a
conditioning stimulus. The extent of inhibition was correlated with the
size of the preceding SBR. In the SBR-negative subjects, simultaneous
inhibition of R2 was observed when median nerve stimulation was applied
as a conditioning stimulus. Brainstem excitability, as evaluated by
blink-reflex recovery studies, did not differ between SBR-positive and
SBR-negative subjects. Therefore, based on anatomical and physiological
findings, it appears that the reflex pathways of the SBR and R2
converge within the brainstem and compete with each other, presumably
by presynaptic inhibition at the premotor level, before entering the
common blink-reflex pathway. The influence of median nerve stimulation
upon tonic contraction of the orbicularis oculi muscle was studied to
detect the latent SBR. There was not only a facilitatory period
corresponding to the SBR but also an active inhibitory period
(exteroceptive suppression), suggesting that the mechanism generating
the SBR is not only influenced by blink-reflex volleys but also by
active exteroceptive suppression. Thus, the SBR may appear as a result
of integration of facilitatory and inhibitory mechanisms within the
brainstem.
PMID: 9549506 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
84: J Urol. 1991 Jul;146(1):118-23. Related Articles,
Links
Cortical evoked potentials by stimulation of the
vesicourethral junction: clinical value and neurophysiological
considerations.
Ganzer H, Madersbacher H, Rumpl E.
Division of Urology and Neurology, University Hospital, Innsbruck,
Austria.
In 21 healthy volunteers and 42 patients with either neurogenic bladder
dysfunction (24), partial peripheral denervation of the bladder (12) or
nonneurogenic bladder dysfunction (6) scalp-derived evoked potentials
after stimulation of the vesicourethral junction (cortical evoked
potentials) were recorded. In addition, evoked potentials from the
posterior tibial nerve (tibial somatosensory evoked potentials) and
from the pudendal nerve (pudendal somatosensory evoked potentials) were
evaluated. The results obtained in normal subjects were reproducible
and comparable to those reported in previous studies. Cortical evoked
potentials of vesicourethral junction consisted of a prominent
negativity with a mean latency of 95 msec. Tibial and pudendal
somatosensory evoked potentials were similar and showed a typical
W-shaped complex. In normal subjects stimulation of the vesicourethral
junction was described as a stimulus-synchronous pulsation combined
with a continuous burning feeling and sometimes with a desire to void.
In 4 normal subjects no cortical evoked potentials of the
vesicourethral junction could be obtained because of a decreased pain
threshold. In regard to clinical value, the results demonstrate that in
patients with lesions of the central nervous system (in the group with
cauda equina and conus medullaris lesions, and in the group with
suprasacral spinal cord lesions) the results of cortical evoked
potentials of the vesicourethral junction and pudendal somatosensory
evoked potentials widely correlate due to similar afferent nervous
pathways within the central nervous system. However, in patients with
partial peripheral denervation of the bladder with suspected additional
secondary local detrusor damage the results of cortical evoked
potentials obtained by stimulation of the vesicourethral junction
differ mostly from the results of somatosensory evoked potentials
obtained by stimulation of the pudendal nerve. The pattern obtained
(increased sensory and pain threshold, normal cortical evoked
potentials of the vesicourethral junction with normal latencies and
normal or increased amplitude) is indicative of local detrusor damage.
In 21 patients the ability to detect cortical evoked potentials of the
vesicourethral junction was combined with the sensation of
stimulus-synchronous pulsation, whereas in the other 21 patients the
absence of this sensation during stimulation was combined with the
absence of cortical evoked potentials. On the other hand, no
correlation was found between the ability of obtaining cortical evoked
potentials of the vesicourethral junction and the stimulus-induced
sensation of pain and/or desire to void.(ABSTRACT TRUNCATED AT 400
WORDS)
PMID: 2056569 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
85: J Neurol Sci. 1997 Feb 12;145(2):177-81. Related
Articles, Links
Pattern reversal visual evoked potentials in classic and
common migraine.
Shibata K, Osawa M, Iwata M.
Department of Neurology, Neurological Institute, Tokyo Women's Medical
College, Japan.
Pattern reversal visual evoked potentials (PVEPs) to transient
checkerboard were recorded in 19 patients with migraine with visual
aura (i.e., classic migraine), 14 patients with migraine without aura
(i.e., common migraine) in the interictal period and 43 normal
subjects. Latencies and amplitudes of PVEPs in each group were
analyzed. In classic migraine patients, P100 amplitude was
significantly higher than in normal subjects (p < 0.01), whereas
latencies of PVEPs did not significantly differ. There were no
significant differences between the common migraine and normal
subjects, nor within the classic and common migraine groups in
latencies and amplitudes of PVEP. Four patients with classic migraine
underwent PVEPs during or 1-2 h immediately after their migraine
attacks. Two of these patients who underwent PVEPs 1.5-2 h after their
attacks showed abnormally increased PVEP amplitudes. These results
suggest that there are different pathophysiologies in the visual
pathway between classic and common migraine and furthermore, classic
migraine patients in interictal periods may have hyperexcitability in
the visual pathway and that the increased amplitude of PVEPs after
attacks may be due to cortical spreading depression.
Publication Types:
* Clinical Trial
PMID: 9094046 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
86: J Neurol Neurosurg Psychiatry. 2000
Oct;69(4):507-11. Related Articles, Links
Long term decline of P100 amplitude in migraine with aura.
Khalil NM, Legg NJ, Anderson DJ.
Department of Neurology, Imperial College School of Medicine,
Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
OBJECTIVES: To investigate visual function in migraine using visual
evoked potentials. METHODS: Electroretinograms (ERGs) and visual evoked
potentials (VEPs) to single flash (SF) and pattern reversal (PR)
stimuli were studied in 92 migraine subjects and 62 controls. RESULTS:
In subjects with migraine, ERGs to single flash were normal. Mean
latencies of the P1 and P2 waves in the SFVEP were increased at the
occiput by 6% and 4% respectively, but normal at the vertex. Mean
latency of the P100 wave in the PRVEP was increased by 5%. These
increases were not related to the presence or absence of an aura or to
the duration of migraine. P100 amplitude showed a more complex
abnormality. It was increased in migraine without aura by 23% compared
with controls, regardless of duration of migraine. In migraine with
aura it was similarly increased, by 23%, in cases of short duration,
but in addition it showed a sharp decline with duration. In cases with
a duration of 30 or more years it was 36% less than in cases of short
duration, and 21% less than in controls. CONCLUSIONS: Subjects with
migraine have constitutionally prolonged VEP latencies and increased
P100 amplitude, but the latter declines to below normal in cases with a
long history of migraine with aura. This decline may reflect subtle
neuronal damage within the visual system from repeated transient
ischaemia experienced during the aura. Future electrophysiological and
other studies will need to be controlled for duration of migraine
history.
PMID: 10990512 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
87: Headache. 1997 Jun;37(6):383-5. Related Articles,
Links
Visual evoked potentials and serum magnesium levels in
juvenile migraine patients.
Aloisi P, Marrelli A, Porto C, Tozzi E, Cerone G.
Servizio di Neurofisiopatologia, University of L'Aquila, Italy.
Changes in visual evoked potentials and decreased intracellular
magnesium levels have been separately described in patients affected by
migraine both during the attacks and in the interictal periods. An
inverse correlation between increased P100 amplitude and lowered serum
magnesium levels was found in children suffering from migraine with and
without aura in a headache-free period. A 20-day treatment with oral
magnesium pidolate seemed to normalize the magnesium balance in 90% of
patients. After treatment, the reduced P100 amplitude confirmed the
inverse correlation with the serum magnesium level. These data seem to
suggest the hypothesis that higher visual evoked potential amplitude
and low brain magnesium level can both be an expression of neuronal
hyperexcitability of the visual pathways related to a lowered threshold
for migraine attacks.
PMID: 9237412 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
88: Arch Neurol. 1997 May;54(5):619-24. Related
Articles, Links
Influence of peripheral nerve stimulation on human motor
cortical excitability in patients with ventrolateral thalamic lesion.
Hirashima F, Yokota T.
Department of Neurology, Tokyo Medical and Dental University, Tokyo,
Japan.
OBJECTIVE: To determine the peripheral afferent pathways that influence
the activities of the motor cortex by examining the effects of
peripheral nerve stimulation on motor cortical excitability. PATIENTS
AND METHODS: We examined 12 healthy volunteers and 4 patients with
localized brain lesions caused by cerebrovascular attack. Of the 4
patients, 1 patient had pontine infarction, including medial lemniscus,
and severe sensory deficit and 3 had small localized lesions in the
lateral part of the thalamus and neither sensory impairment nor
abnormal N20 waves on somatosensory evoked potential recordings.
Central motor tract excitability was examined by measuring a change in
the motor evoked potential (MEP), using transcranial magnetic
stimulation of the motor cortex after peripheral nerve stimulation at
the wrist significantly increased MEP response in the controls at long
conditioning-test intervals of 28 to 60 milliseconds, as well as at
short intervals of 0 to 6 milliseconds. A late MEP potentiation was not
observed on the affected side in all patients. CONCLUSIONS: The loss of
late MEP potentiation in patients with pontine and thalamic lesions
indicates that this potentiation is caused by the alternation of the
motor cortical excitability. Furthermore, the results in the patients
with thalamic lesions suggest that the lateral nuclei of the thalamus,
other than the ventral posterolateral nucleus and probably including
the ventrolateral nucleus, have an important function in the processing
of peripheral sensory input for tuning motor cortical excitability.
PMID: 9152119 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
89: Rinsho Byori. 1995 Sep;43(9):965-70. Related
Articles, Links
[Excitability of motor cortex with transcranial magnetic
double stimulation in the intact man]
[Article in Japanese]
Yoshino A, Yokota T.
Department of Medical Technology, Tokyo Medical and Dental University.
To evaluate the excitability of central motor tract, we studied a
transcranial magnetic double stimulation with short conditioning-test
(C-T) interval of 1-10ms in eight normal volunteers. In addition,
H-reflex of the forearm muscle was used to study the effect of the
magnetic cortical conditioning stimulus on alpha-motoneuron, and the
test response evoked by electrical cortical stimulation was also used
to examine the effect of the magnetic cortical conditioning stimulus.
The subthreshold conditioning and suprathreshold test stimuli were
applied, and compound muscle responses were recorded in the relaxed
abductor pollicis brevis muscle. There was a decrease of the test
response size by the conditioning stimulus at C-T interval of 1-5ms.
This attenuation was probably caused by intracortical inhibition.
Because the identical magnetic cortical conditioning stimulus produced
increase in H-reflex size. Moreover, the test response evoked by
electrical cortical stimulus was not suppressed by the magnetic
cortical conditioning stimulus; whereas, response evoked by the
magnetic cortical test stimulus was suppressed at C-T intervals of 2ms.
With the technique of transcranial magnetic double stimulation,
therefore, it is possible to evaluate the inhibitory function in the
motor cortex. The technique may be of use for pathophysiology,
diagnosis and estimation of treatment in the diseases.
Publication Types:
* Clinical Trial
PMID: 7474462 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
90: J Neurol Neurosurg Psychiatry. 1986
Nov;49(11):1280-7. Related Articles, Links
Visual evoked cortical potentials and pattern
electroretinograms in Parkinson's disease and control subjects.
Nightingale S, Mitchell KW, Howe JW.
Parkinson's disease patients have been shown to have abnormal visually
evoked cortical potentials (VEPs) to pattern stimulation. Whereas
dopamine is not an important neurotransmitter in the central visual
pathways, the retina is rich in dopamine and, together with previous
animal and human studies, this suggests that the abnormal VEPs in
Parkinson's disease patients may be due to a biochemical and
electrophysiological disorder in the retina. This hypothesis has been
examined by studying the VEPs and pattern electroretinogram (PERG) of
Parkinson's disease patients and matched control subjects. The
amplitudes of the cortical and retinal evoked potentials were
significantly reduced in Parkinson's disease patients compared with the
control subjects and this could not be attributed to any particular
feature of the disease or its treatment. There was a significant
relationship between the VEP P100 latency and the PERG amplitude.
Moreover for those subjects in whom there was an interocular difference
in both cortical and retinal evoked potentials, the abnormality was
more commonly found in the potentials from the same eye. These findings
suggest that the abnormality of the VEP in Parkinson's disease patients
is, at least in part, secondary to an abnormality of the retina itself.
PMID: 3794734 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
91: Headache. 1999 Jul-Aug;39(7):469-76. Related
Articles, Links
The occipital cortex is hyperexcitable in migraine:
experimental evidence.
Aurora SK, Cao Y, Bowyer SM, Welch KM.
Department of Neurology, Henry Ford Health Sciences Center, 2799 West
Grand Boulevard, Detroit, MI 48202-2689, USA.
OBJECTIVES: Threshold for generation of magnetophosphenes has been
reported to be lower in migraine. We compared the threshold for
eliciting phosphenes by transcranial magnetic stimulation and the
ability to visually trigger headache in a select group of individuals
with migraine with and without aura to normal controls. METHODS:
Transcranial magnetic stimulation was performed using the Cadwell
MES-10 stimulator. A circular coil, 9.5 cm in diameter, was applied to
the occipital scalp (7 cm above the inion). Stimulator intensity was
increased in 10% increments until subjects reported visual phenomena or
100% intensity was reached. Stimulator intensity was then fine-tuned to
determine the threshold at which phosphenes were seen. In the same
subjects, visual stimulation was given in 3.0 T MRI and if a headache
occurred the response was recorded. RESULTS: Fifteen subjects with
migraine were compared to 8 controls. A significant proportion of the
migraineurs (86.7%) developed phosphenes compared to the controls (25%)
(P = .006). The probability of triggering a headache was also higher in
the migraineurs (53%); no headache was triggered in the controls (P =
.019). A significant correlation was found between the threshold for
phosphenes on transcranial magnetic stimulation and visually triggered
headache (P = .002). When only migraine was considered, there was again
a significant trend (P = .084). CONCLUSIONS: There is a difference in
threshold for excitability of occipital cortex in migraineurs and
controls. The hyperexcitable visual cortex in migraine is predisposed
to visually triggered headache.
PMID: 11279929 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
92: Nervenarzt. 2002 Apr;73(4):332-5. Related Articles,
Links
[Modulation of cortical excitability by transcranial direct
current stimulation]
[Article in German]
Nitsche MA, Liebetanz D, Tergau F, Paulus W.
Abteilung Klinische Neurophysiolgie, Georg-August-Universitat
Gottingen. mnitsch1@gwdg.de
Modulation of cerebral excitability is thought to be one mechanism
underlying the pharmacological treatment of neuropsychiatric diseases
such as epilepsy, depression, and dystonia. Repetitive transcranial
magnetic stimulation (rTMS) has been tested for several years as a
nonpharmacological, noninvasive method of directly influencing
patients' cortical functions. We present an overview of the more easily
performed transcranial direct current stimulation (tDCS) with weak
current, which produces distinctly more pronounced changes in
excitability than rTMS. The basic underlying mechanism is a shift in
the resting membrane potential towards either hyper- or depolarisation,
depending on stimulation polarity. This in turn leads to changes in the
excitability of cortical neurons. Anodic stimulation increases cortical
excitability, while cathodic stimulation decreases it. These changes
persist after the end of stimulation if the stimulation lasts long
enough, i.e., at least several minutes. The duration of this
aftereffect can be controlled through the duration and intensity of the
stimulation. Transcranial direct current stimulation essentially allows
a focal, selective, reversible, pain-free, and noninvasive induction of
changes in cortical excitability, the therapeutic potential of which
must be evaluated in clinical studies, once possible risk factors have
been assessed.
Publication Types:
* Review
* Review, Tutorial
PMID: 12040980 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
93: Acta Psiquiatr Psicol Am Lat. 1986 Mar;32(1):11-25.
Related Articles, Links
[Electrophysiological contributions to the study of
attention]
[Article in Spanish]
Lolas F.
A selective review of electrophysiological studies of attention and
attentional behavior is presented. The emphasis is placed on the
contribution of cerebral event-related potentials (ERP) (evoked
potentials) to the clarification of major issues, such as the role of
peripheral versus central mechanisms and testing of hypotheses
regarding selective attention. A number of clinical studies dealing
mostly with diagnostic applications and therapeutic trials is
discussed. The difficulties of interpretation and integration with
other sources of knowledge on behavioral physiology are briefly
discussed.
PMID: 3751641 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
94: Brain Dev. 1995 May-Jun;17(3):175-81. Related
Articles, Links
Neurophysiological study in Pelizaeus-Merzbacher disease.
Nezu A.
Department of Pediatrics, Yokohama City University, School of Medicine,
Japan.
The Neurophysiological characteristics of Pelizaeus-Marzbacher disease
(PMD) were studied in four Japanese patients aged between 5 and 13
years. Pendular spontaneous nystagmus was always recorded with a
frequency between 2.5 and 4 Hz, and abnormal saccades with an almost
twofold prolongation in onset time and 50% decrease in velocity were
noted. Brainstem auditory evoked potentials consistently demonstrated
severely altered waves II to V, following a normal wave I, despite
normal hearing acuity. Somatosensory evoked potentials (SEPs) were
always absent between brainstem components and early cortical
responses. Late cortical components of SEPs and visual evoked
potentials with significantly prolonged latencies were recorded in the
three younger cases having normal sensory and visual acuity (N35 of
SEP, 73.1 +/- 2.1 ms; N75 of VEP, 129.0 +/- 12.7 ms; mean +/- S.D.),
while these peaks were absent in the oldest case having the most severe
handicap. In motor evoked potentials (MEPs), R1 of blink reflex with
significantly prolonged latency (14.9 +/- 1.48ms) was always obtained,
and no subsequent R2 was elicited. Magnetic transcortical stimulation
elicited no MEPs of the thenar even in the facilitating condition on
voluntary contraction despite mild weakness of the thenar, while normal
MEPs were always elicited on cervical stimulation. These
electrophysiological findings were consistent with extensive conduction
slowing involving the brainstem to the cerebrum, which seemed to be
accompanied by conduction block in motor systems rather than sensory
systems. Although each of the results was not specific, in combination
they suggested the characteristics of diffuse brain dysmyelination in
PMD.
PMID: 7573756 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
95: J Clin Neurophysiol. 2000 Mar;17(2):201-11. Related
Articles, Links
Comment in:
* J Clin Neurophysiol. 2000 Mar;17(2):175-6.
Somatosensory, auditory, and visual evoked magnetic fields in
patients with brain diseases.
Nakasato N, Yoshimoto T.
Department of Neurosurgery, Tohoku University School of Medicine,
Sendai, Japan.
The features of somatosensory (SEFs), auditory (AEFs), and visual
evoked fields (VEFs) in healthy subjects and patients with brain
diseases provide the basis for clinical investigations using
magnetoencephalography (MEG). The SEFs provide clinically useful
information to identify the central sulcus and somatotopic organization
of the primary somatosensory cortex. Localization accuracy of the SEFs
can be tested by cortical stimulation during surgery. Functional
reorganization suggested by SEF studies must be verified by other
modalities. The AEFs can localize the auditory cortex in the bilateral
temporal lobes. Separation of bilateral activities is much clearer in
AEFs than in auditory evoked potentials. Modulation of the
interhemispheric differences of latency, amplitude, and source
localization of AEFs can be used to evaluate auditory function in
patients with intracranial lesions. Pattern reversal VEFs provide
stable localization of the primary visual function. Separation of
bihemispherical activities is the advantage of VEFs over visual evoked
potentials. Investigation of VEFs provides objective evaluation of
visual field deficits such as homonymous or bitemporal hemianopsia in
patients with intracranial lesions. Evoked magnetic fields can provide
useful diagnostic information. Such clinical findings, in turn,
provides the opportunity to test the source estimation accuracy of MEG.
PMID: 10831111 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
96: Muscle Nerve. 1996 Dec;19(12):1586-95. Related
Articles, Links
Reduced brain stem excitability in mitochondrial myopathy:
evidence for early detection with blink reflex habituation studies.
Koutroumanidis M, Papadimitriou A, Bouzas E, Avramidis T,
Papathanassopoulos P, Howard RS, Papapetropoulos T.
Department of Clinical Neurophysiology and Epilepsies, St Thomas'
Hospital, London, United Kingdom.
Blink reflex (BR) was studied in 17 patients with histochemically and
genetically confirmed mitochondrial myopathy (MM). Fourteen patients
had chronic progressive external ophthalmoplegia (CPEO) associated with
a mild to moderate craniosomatic myopathy without any symptoms or signs
of central nervous system (CNS) involvement, 2 myoclonic epilepsy with
ragged red fibers syndrome, and 1 Kearns-Sayre syndrome. The mean
latencies of the early (R1) and late (R2) responses were prolonged (P
< 0.01 and P < 0.001, respectively), and the corresponding
amplitudes decreased (P < 0.001). Increased habituation of the
reflex was clearly observed in 10 out of 14 patients tested (71.4%), 9
of whom presented CPEO. These findings suggest that the brain stem
reticular network is in a state of basal inhibition which is presumably
due to a subclinical impairment of the cerebral cellular metabolism.
Multimodal evoked potentials revealed abnormalities suggestive of CNS
involvement in 7 out of 17 patients (41.2%), 4 of whom had CPEO. These
observations document the validity of BR in detecting clinically silent
brain stem impairment in patients with apparently pure MM and provide
important clues for a further understanding of the underlying
pathophysiology.
PMID: 8941273 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
97: Neurosci Lett. 2002 Nov 15;333(1):29-32. Related
Articles, Links
Abnormal brain processing of cutaneous pain in migraine
patients during the attack.
de Tommaso M, Guido M, Libro G, Losito L, Sciruicchio V, Monetti C,
Puca F.
First Neurologic Clinic, University of Bari, Policlinico, Piazza G
Cesare 11, 70124 Bari, Italy. m.detommaso@neurol.uniba.it
We examined cutaneous pain thresholds using CO(2) laser stimuli during
migraine attacks, and defined the evoked cortical potential
characteristics. Ten patients without aura were studied during attacks
and for at least 72 h subsequently. Pain stimuli were generated on the
dorsum of both hands and the right and left supraorbital zones, using
pulses from a CO(2) laser. Absolute latencies of scalp potentials were
measured at the highest peak of each response component, and the
peak-to-peak amplitudes of N2a-P2 components were recorded. Cutaneous
pain thresholds were significantly reduced on both the symptomatic and
non-symptomatic sides during the attack, in comparison with the
headache-free phase. The N2a-P2 complexes also increased in amplitude
during attacks in comparison with the pain-free side. Thus, cutaneous
hyperalgesia occurs during migraine attack, and is subtended by central
sensitization phenomena, probably involving the cortex. Copyright 2002
Elsevier Science Ireland Ltd.
PMID: 12401553 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
98: Electroencephalogr Clin Neurophysiol. 1981
Oct;52(4):283-97. Related Articles, Links
Visual, auditory and somatosensory pathway involvement in
hereditary cerebellar ataxia, Friedreich's ataxia and familial spastic
paraplegia.
Pedersen L, Trojaborg W.
Pattern-reversal visual, auditory and somatosensory evoked potentials
were recorded from 11 patients with hereditary cerebellar ataxia, 13
with familial spastic paraplegia and 7 with Friedreich's ataxia. In all
the 31 patients the conduction velocity along the median and tibial
nerves to the level of the spinal cord was normal. Five of the 7
patients with Friedreich's ataxia had reduced sural nerve sensory
potentials. There was electrophysiological evidence of malfunction
along one or several pathways within the CNS in 8 of the 11 patients
with cerebellar ataxia, 4 of the 13 with familial spastic paraplegia,
and in all 7 cases of Friedreich's ataxia. The increase in latency of
visual, auditory and somatosensory evoked cortical potentials is
attributed to nerve fibre loss in the central pathways with associated
slowing of conduction.
PMID: 6169505 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
99: J Neurol Sci. 1996 Oct;142(1-2):45-53. Related
Articles, Links
Autosomal dominant cerebellar ataxia type I: multimodal
electrophysiological study and comparison between SCA1 and SCA2
patients.
Perretti A, Santoro L, Lanzillo B, Filla A, De Michele G, Barbieri F,
Martino G, Ragno M, Cocozza S, Caruso G.
Department of Clinical Neurophysiology, Universita degli studi di
Napoli "Federico II", Italy.
A multimodal electrophysiological study was performed on 41 patients
from 24 families with autosomal dominant cerebellar ataxia type I (ADCA
I). Upper- and lower-limb motor evoked potentials (MEPs) to
transcranial magnetic stimulation, median and tibial nerve
somatosensory evoked potentials (Mn and Tn-SSEPs), orthodromic sensory
(SCV) and motor conduction (MCV) velocity along median and tibial
nerve, brainstem auditory evoked potentials (BAEPs), and visual evoked
potentials (VEPs) were examined. Molecular analysis showed 2 SCA1
families and 2 families linked to the SCA2 locus. A sural nerve biopsy
was performed in 5 patients. Brainstem damage of the auditory pathway
was observed in 79% of patients examined. VEP abnormalities possibly of
central origin were found in 52% of patients. MEP and SSEP
abnormalities were differently distributed along the pathways examined:
the longer the pathway, the higher the occurrence and severity of
impairment. Peripheral dying-back neuropathy (confirmed by nerve
bioptic data) was a frequent finding (56%). A progressive degenerative
process involving first the longest tracts of the central motor and
central and peripheral branches of somatosensory pathways is
hypothesized in ADCA I. MEP abnormalities were more frequent in SCA1,
and the sensory-motor neuropathy was more severe in SCA2.
PMID: 8902719 [PubMed - indexed for MEDLINE]
------------------------------------------------------------------------
100: Headache. 1992 Jul;32(7):360-5. Related Articles,
Links
Bilateral occipital lobe infarction in acute migraine:
clinical, neurophysiological, and neuroradiological study.
Ganji S, Williams W, Furlow J.
EEG and Evoked Potential Labs, Terrebonne General Medical Center,
Houma, Louisiana 70361.
A woman having common migraine attacks coincident with an asymmetrical
bilateral occipital lobe infarction that spared the brainstem and
cerebellum underwent these studies: serial electroencephalography,
brainstem auditory, visual and somatosensory evoked potentials,
magnetic resonance imaging of the brain and cerebral arteriography. The
patient's vision improved greatly during a one-year follow-up. The
absence of risk factors for stroke suggested that migraine caused the
infarction in the posterior circulation network. The pathophysiological
mechanisms of stroke in migraine remains speculative.
PMID: 1526769 [PubMed - indexed for MEDLINE]
