The Concept of Migraine as a State of Central Neuronal Hyperexcitability

Consecutive Transcranial Magnetic Stimulation: Phosphene Thresholds in Migraineurs and Controls

OBJECTIVE

To characterize the temporal course of transcranial magnetic stimulation-induced phosphene thresholds in subjects with migraine and in controls.

METHODS

Eleven subjects with migraine with aura, 10 subjects with migraine without aura, 9 subjects with menstrual migraine, and 15 controls (no history of migraine and without migraine during the study) were studied. Subjects were not on preventive medication. Transcranial magnetic stimulation was performed, and a phosphene threshold was measured 3 times a week over 3 weeks in a manner timed to incorporate the menstrual period in females. A headache calendar was kept during the study.

RESULTS

Mean transcranial magnetic stimulation thresholds were lower for each migraine group compared with controls (P <.001) for each comparison. There was a trend for lower thresholds among subjects with migraine with aura compared with subjects with migraine without aura (P <.10), but not subjects with menstrual migraine. There was consistent lowering of thresholds from the first to the last stimulation in all migraine groups and in the controls. Maximum and minimum thresholds did not predict headache occurrence, nor did the occurrence of headache predict an ensuing maximum or minimum phosphene threshold.

CONCLUSIONS

Transcranial magnetic stimulation thresholds are lower in subjects with migraine compared with controls. The reported phosphene threshold is lowered with repeated measurement. Neither high nor low phosphene thresholds predict a subsequent headache, nor do migraines predict a subsequent high or low threshold.

Migraine: an ophthalmologist's perspective

PURPOSE OF REVIEW

Migraine is a common disorder with visual and neurologic manifestations. Many patients present to ophthalmologists without a previous diagnosis of migraine. It is therefore essential for the ophthalmologist to have a good understanding of migraine to appropriately help these patients. Neurologic syndromes with migraine and retinopathy are well known. Here again, the ophthalmologist may play a role in establishing the correct diagnosis.

RECENT FINDINGS

For long the initial changes during a migraine attack have been shown to occur in the occipital cortex. In the recent years, the understanding of migraine has advanced with the availability of functional neuroimaging. A possible role of brainstem structures in the initiation of migraine attacks has been proposed based on functional magnetic resonance imaging blood oxygenation level-dependent signals. Activation of brainstem structures preceded activation of occipital cortex. Our understanding of cortical spreading depression is also advancing. Using multiwavelength optical intrinsic imaging, cortical spreading depression has been shown to have a triphasic response in rats. For the first time it has been shown that the cortical spreading depression activated the trigeminovascular system, which is followed by a series of cortical meningeal and brainstem events that cause the migraine headache. Sildenafil has been shown to induce migraine attack without dilation of cerebral blood vessels, further confirming that Wolf's vasogenic theory may not be true. Several loci for migraine have been identified in recent years. A new locus for migraine with and without aura has been identified on chromosome 6, a locus for migraine without aura to chromosome 14, and a locus for migraine with aura on chromosome 4.

SUMMARY

Our understanding of migraine is rapidly evolving with functional neuroimaging. There are several unanswered questions. In this article, we will review the epidemiology, genetics, and clinical features of various forms of migraine with emphasis on ocular migraine, pathogenesis, and briefly the management of migraine.

Epilepsy and migraine

Migraine and epilepsy are both chronic disorders characterized by recurrent neurologic attacks variously accompanied by headache as well as by gastrointestinal, autonomic, and psychologic features. Migraine and epilepsy are linked by their symptom profiles, comorbidity, and treatment. The presence of one disorder increases the likelihood that the other is also present. In addition, a number of migraine syndromes can be confused with epilepsy. The diagnosis and treatment of each disorder must take into account the potential presence of the other. Herein, we review the relationship between migraine and epilepsy. We discuss the diagnosis of migraine using the International Headache Society criteria, emphasizing the variants of migraine most frequently mistaken for epilepsy. We summarize the epidemiologic evidence that migraine and epilepsy are associated and discuss specific interrelationships between migraine and epilepsy.

Electrophysiological studies in migraine: a comprehensive review of their interest and limitations

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.

Visual distortion provoked by a stimulus in migraine associated with hyperneuronal activity

BACKGROUND

Migraineurs with visual aura are highly susceptible to illusions and visual distortion and are particularly sensitive to a pattern of regularly spaced parallel lines or stripes.

PURPOSE

To determine whether the high degree of susceptibility to illusions and visual distortion in migraineurs with aura is associated with hyperneurological activity of the occipital cortex.

METHODS

In order to investigate any relationships among neuronal activity, spatial frequency of square-wave gratings, and self-described visual distortion, we investigated the neuronal and psychophysical responses to square-wave gratings in migraineurs with visual aura and in nonheadache controls.

RESULTS

Square-wave gratings provoked various types of visual distortion and illusions and induced a hyperneuronal response in the visual cortex of migraineurs with visual aura, a response that strongly depended upon the stimulus spatial frequency.

CONCLUSION

The hyperneuronal activity of the occipital cortex is consistent with general cortical hyperexcitability in migraine.

Topiramate in the preventive treatment of episodic migraine: a combined analysis from pilot, double-blind, placebo-controlled trials

The safety and efficacy of medications for preventive treatment of migraine is the subject of current concern and investigation in health care. Two single-center, double-blind, placebo-controlled studies were conducted to evaluate the efficacy and safety of topiramate for migraine prophylaxis. Seventy patients with a diagnosis of migraine were randomly assigned to topiramate-treated and placebo groups. The studies consisted of a 4-week baseline phase, a 6-8 week titration, and 8-12 weeks of maintenance. Topiramate was titrated from an initial dose of 25 mg/day to a target dose of 100 mg BID. The primary efficacy measure, the mean 28-day migraine frequency, was lower in topiramate-treated patients than in the placebo group (3.2 versus 3.8, P=.001). Similarly, topiramate treatment resulted in a significantly greater mean reduction in migraine frequency than did placebo (1.55 versus 0.47, P=.001) and a significantly higher responder rate (35.3% versus 8.3%, P=.008). Paresthesia was the most common side effect reported with topiramate treatment. Other topiramate-associated adverse events included altered taste, memory impairment, diarrhea, and appetite suppression/weight loss. The rates of discontinuation were similar for the topiramate group (n=10) and the placebo group (n=8). These results suggest that topiramate is effective and well tolerated in the preventive treatment of migraine headaches.

Evoked potentials and transcranial magnetic stimulation in migraine: published data and viewpoint on their pathophysiologic significance

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.

Pathophysiology, epidemiology, and impact of migraine

Despite a decade of progress, migraine headache remains prevalent, disabling, underdiagnosed, and undertreated in the United States. Migraine affects approximately 12% of the population, and the economic burden in terms of annual cost of labor lost to migraine disability is between $5.6 and $17.2 billion. The threshold for migraine may be genetically determined, although recent genetic and neurophysiologic studies point to migraine as possibly a channelopathy. Cerebral cortical and brain stem changes occur in migraine. Head pain and associated symptoms of migraine can be explained by activation of the trigeminal vascular system. Evidence has also been accumulated that suggests the release of nitric oxide is an important trigger mechanism. Introduction of the triptans has dramatically advanced acute migraine pharmacotherapy, and preventive therapy has greatly improved; however, public health initiatives may be needed to further advance diagnosis and treatment of this common and disabling disorder.

The threshold for phosphenes is lower in migraine

We have reported a preliminary study confirming hyperexicitability of occipital cortex in migraine with aura (MwA) using transcranial magnetic stimulation (TMS). We have now completed a blinded study to investigate the occipital cortex in MwA and without aura (MwoA) compared with normal controls (NC) using TMS. TMS was performed using the Caldwell MES-10 stimulator. A circular coil 9.5 cm 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. Stimulation intensity was then fine tuned to determine the threshold at which phosphenes were seen. Fisher's exact t-test and logrank test were used for statistical comparisons. Ten subjects with MwA and MwoA were compared to 10 NC. The difference in the proportion of subjects with phosphene generation was statistically significant (MwA 100%, MwoA 60% and NC 30%) [P = 0.003]. The difference in threshold levels for phosphenes was also significant for MwA 42.8%, and controls 57.3% [P = 0.0001]. There is a difference in threshold for excitability of occipital cortex in MwA and MwoA compared to NC. This is a direct neurophysiological correlate for clinical observations, which have inferred hyperexicitability of the occipital cortex in migraineurs.

Drug therapy of neurovascular disease

Recent advances in the prevention and pharmacotherapy of cerebrovascular disease have provided more favorable clinical outcomes. For the treatment of an acute ischemic stroke, the early use of thrombolytic agents can reduce the degree of brain damage while improving functional outcomes. However, trials evaluating various classes of other neuroprotective agents have not shown benefit to date. For the prevention of second stroke, the use of antiplatelet drugs, HMG-CoA reductase inhibitors, and angiotensin-converting enzyme inhibitors with a diuretic have shown benefit in reducing new events. In patients with underlying heart disease or atrial fibrillation, warfarin appears to be the drug of choice in preventing stroke. Early treatment of hemorrhagic stroke with calcium channel blockers can improve the functional outcome. Innovative therapies are now available for the treatment of migraine and vascular dementia. Primary prevention of stroke remains the optimal therapeutic strategy and includes treatment of systemic hypertension and hypercholesterolemia.

Ergotamine and dihydroergotamine: a review

The ergot alkaloids were the first specific antimigraine therapy available. However, with the advent of the triptans, their use in the treatment of migraine has declined and their role has become less clear. This review discusses the pharmacology, efficacy, and safety of the ergots. In randomized clinical trials, oral ergotamine was found to be superior to placebo, but inferior to 100 mg of oral sumatriptan. In contrast, rectal ergotamine was found to have higher efficacy (73% headache relief) than rectal sumatriptan (63% headache relief). Intranasal dihydroergotamine was found to be superior to placebo, but less effective than subcutaneous and intranasal sumatriptan. Ergotamine is still widely used in some countries for the treatment of severe migraine attacks. It is generally regarded as a safe and useful drug if prescribed for infrequent use, in the correct dose, and in the absence of contraindications; however, safer and more effective options do exist in the triptans. In patients with status migrainous and patients with frequent headache recurrence, ergotamine is still probably useful.

Prolonged cortical electrical depression and diffuse vasospasm without ischemia in a case of severe hemiplegic migraine during pregnancy

The pathophysiology of the neurological deficits in hemiplegic migraine remains unclear. Both neurogenic and vascular etiologies have been proposed to explain this phenomenon. We present the case of a patient with hemiplegic migraine in whom there was no diffusion weighted magnetic resonance imaging evidence of cerebral ischemia, despite persistent left hemiplegia and diffuse vasospasm on cerebral angiography, there was no diffusion weighted magnetic resonance imaging evidence of cerebral ischemia. In addition, hypoperfusional changes were seen diffusely, more so on the less symptomatic hemisphere, whereas depression of cortical electrical activity was seen for several days on the right side. These findings support the notion that although both neurogenic and vascular changes occur in hemiplegic migraine, the former seems to be a more likely explanation for the neurological deficits.

EEG photic driving in workers exposed to mercury vapors

OBJECTIVE

To assess the potential of EEG photic driving (PD) as an indicator of an early neurotoxic effect of long-term, low-level exposure to mercury vapors.

SUBJECTS AND METHODS

Twenty-four chloralkali workers exposed to mercury vapors; twenty-four age- and gender-matched control subjects. Level of exposure was determined by urinary mercury excreted both spontaneously and after administration of a chelating agent, sodium 2,3-dimercapto-1-propane sulfonate. A computerized method for quantitative evaluation of PD was developed. Five parameters describing PD were compared.

RESULTS

The number of stimulation frequencies eliciting PD was higher in the exposed group, with a median of 17 frequencies, as compared to 10 frequencies in the control group (P < 0.001). The maximum value of PD was higher in the exposed group, with a median of 24.6 z-units as compared to 9.4 in the control group (P < 0.001). The median of the stimulation frequency with maximum PD was shifted from 15 Hz in the control group to 20 Hz in the exposed group (P < 0.01). The median of the sum of PD and the median of the index of PD were significantly higher in the exposed than in the control group (P < 0.001). The increased PD was particularly prominent at high stimulation frequencies in the beta range. There was no significant association between the measures of PD and the measures of exposure.

CONCLUSIONS

In comparison with a control group, significantly increased photic driving was observed in a group of workers exposed to mercury vapors. The issue of whether or nor the intergroup differences in PD are mercury related, could not be determined on the basis of our results. Should the enhanced PD be caused by mercury, then this electrophysiological phenomenon might be regarded as a marker of the CNS hyperexcitability due to an early neurotoxic effect of mercury, the clinical expression of which is erethism.

New migraine preventive options: an update with pathophysiological considerations

BACKGROUND

The pharmacological treatment of migraine may be acute or preventive. Frequent, severe and long-lasting migraine attacks require prophylaxis. Multiple threads of research over the last 15 years have led to the concept that migraine is generated from a hyperexcitable brain. A variety of causes for hyperexcitability of the brain in migraine have been suggested. These causes include low cerebral magnesium levels, mitochondrial abnormalities, dysfunctions related to increased nitric oxide or the existence of a P/Q type calcium channelopathy. The better knowledge about migraine pathophisiology led us to discuss new treatment options.

OBJECTIVES

The aim of the present study is to present an evidence-based review of some new drugs or some agents that even though available for a long time, are not frequently used.

METHODS/RESULTS

We present a review of anticonvulsants with various mechanisms of action such as lamotrigine, gabapentin, topiramate, tiagabine, levetiracetam and zonisamide. We also review natural products, like riboflavin and magnesium, botulinum toxin A, a specific CGRP antagonist and the anti-asthma medication montelukast, with pathophysiological discussion.

CONCLUSIONS

We aimed to present an update of newer or less frequently used preventive migraine therapies, drugs that might reduce the burden and the costs of a disease that should be considered as a public health problem all around the world.

New and emerging prophylactic agents for migraine

Frequent, severe and long-lasting migraine attacks require prophylaxis. Established drugs used for the prevention of migraine such as beta-adrenoceptor antagonists (beta-blockers), calcium channel antagonists, antidepressants and others have an unknown mode of action in migraine. Their prophylactic effect in migraine was discovered by chance in clinical practice when these drugs were used for other purposes. Recently, research into the mechanisms of migraine and the progressive recognition that cortical hyperexcitability and an imbalance between neuronal inhibition [mediated by gamma-aminobutyric acid (GABA)] and excitation (mediated by excitatory amino acids) may play an important role in migraine pathophysiology have lead to the identification of potential new agents for the prevention of migraine attacks. This paper reviews the recent literature on these new agents. A search was conducted using MEDLINE from 1998 to November 2001 with the following search terms: migraine, preventive, prophylactic and treatment. Headache textbooks edited in 2000 and 2001 were also used. After analysing the available controlled and uncontrolled clinical studies as well as abstracts, divalproex sodium (valproate semisodium) can be recommended for the prevention of migraine. Lamotrigine may be useful for preventing aura associated with migraine, and topiramate seems a promising option pending trials with more patients, which are currently underway. Riboflavin (which is possibly involved in improving neuronal energy production) appears to be a promising agent, although comparisons with established prophylactic medications are needed. Gabapentin, magnesium, lisinopril and botulinum toxin A have recently been suggested to be effective; however, at present, there are insufficient rigorous and reliable controlled data on these drugs for them to be indicated for such use. Emerging options such as tiagabine, levetiracetam, zonisamide and petasites may all be useful, but controlled data are required to confirm their efficacy. The anti-asthma medication montelukast was found to be effective in an open trial, but ineffective in a recently completed controlled trial. There is an expectation that modern neuroscience will soon provide more efficacious and better tolerated prophylactic medications for migraine.

Efficacy of topiramate in migraine prophylaxis: a retrospective chart analysis

OBJECTIVE

Topiramate, a broad-spectrum anticonvulsant with multiple mechanisms of action, may be effective in preventing migraine headaches. We report the results of a retrospective chart review of patients treated with topiramate for prophylaxis of migraine.

METHODS

Patients with a diagnosis of migraine who had at least one follow-up visit after > or =4 weeks on topiramate were eligible; 69 patients (56 women and 13 men) aged 18 to 68 years met these criteria. Charts were reviewed for frequency of mild or moderate/severe headaches at the start of topiramate (baseline) and at all subsequent visits up to 24 weeks.

RESULTS

The 28-day frequency of moderate/severe migraines declined significantly from baseline to end of treatment (10.6 +/- 8.4 to 7.4 +/- 7.7, respectively; P = 0.0004), whereas that of mild headaches did not demonstrate a significant change (from 11.8 +/- 8.9 to 11.0 +/- 10.0). Among the 38 patients who had not responded previously to >or =9 preventive medications, the monthly frequency of moderate/severe (but not mild) headaches decreased significantly from baseline to end of treatment. Patients who previously had not responded to <9 prior medications experienced significant declines in both mild and moderate/severe headaches. The most common adverse events were paresthesias, drowsiness, diarrhea, decreased appetite, and weight loss. Twenty-seven patients discontinued topiramate therapy, 20 as a result of adverse events and 7 due to lack of response.

CONCLUSION

Topiramate may be effective in reducing the frequency of both mild and moderate/severe migraine headaches. In particular, topiramate may offer relief to patients with moderate/severe migraines who do not respond to other treatments.

Intravenous magnesium sulphate in the acute treatment of migraine without aura and migraine with aura. A randomized, double-blind, placebo-controlled study

Magnesium sulphate has been used in the acute treatment of migraines; some studies found it to be a highly effective medication in the acute control of migraine pain and associated symptoms. This randomized, double-blind, placebo-controlled study assesses the effect of magnesium sulphate on the pain and associated symptoms in patients with migraine without aura and migraine with aura. Sixty patients in each group were assigned at random to receive magnesium sulphate, 1000 mg intravenously, or 0.9% physiological saline, 10 ml. We used seven parameters of analgesic evaluation and an analogue scale to assess nausea, photophobia and phonophobia. In the migraine without aura group there was no statistically significant difference in the patients who received magnesium sulphate vs. placebo in pain relief. The analgesic therapeutic gain was 17% and number needed to treat was 5.98 at 1 h. There was also no statistical difference in relief of nausea. We did observe a significant lower intensity of photophobia and phonophobia in patients who received magnesium sulphate. In the migraine with aura group patients receiving magnesium sulphate presented a statistically significant improvement of pain and of all associated symptoms compared with controls. The analgesic therapeutic gain was 36.7% at 1 h. A smaller number of patients continued to have aura in the magnesium sulphate group compared with placebo 1 h after the administration of medication. Our data support the idea that magnesium sulphate can be used for the treatment of all symptoms in migraine with aura, or as an adjuvant therapy for associated symptoms in patients with migraine without aura.

Eficácia de três drogas sobre a aura migranosa: um estudo randomizado placebo controlado

A despeito da enorme quantidade de pesquisas referentes à classificação, epidemiologia, diagnóstico, fisiopatologia e tratamento da migrânea, a aura migranosa permanece bem menos estudada. O objetivo do presente estudo é, portanto, verificar a evolução da aura em pacientes submetidos a placebo e a três diferentes drogas disponíveis em unidades públicas de saúde brasileiras. Foram estudados 86 pacientes em vigência de crise de migrânea com aura, apresentando aura no momento da randomização. Após a randomização os pacientes recebiam uma das seguintes substâncias, por via endovenosa: placebo, dipirona, clorpromazina, sulfato de magnésio. O sulfato de magnésio foi superior ao placebo (p < 0,05) 30 e 60 minutos após a administração. Dipirona e clorpromazina reduziram o número de pacientes com aura, em relação ao placebo, 60 minutos após a administração. Os achados acima possibilitam especulações sobre a fisiopatologia da migrânea e apresentam opções terapêuticas para o tratamento da aura.

Contrasts in cortical magnesium, phospholipid and energy metabolism between migraine syndromes

BACKGROUND

Previous single voxel (31)P MRS pilot studies of migraine patients have suggested that disordered energy metabolism or Mg(2+) deficiencies may be responsible for hyperexcitability of neuronal tissue in migraine patients. These studies were extended to include multiple brain regions and larger numbers of patients by multislice (31)P MR spectroscopic imaging.

METHODS

Migraine with aura (MWA), migraine without aura (MwoA), and hemiplegic migraine patients were studied between attacks by (31)P MRS imaging using a 3-T scanner.

RESULTS

Results were compared with those in healthy control subjects without headache. In MwoA, consistent increases in phosphodiester concentration [PDE] were measured in most brain regions, with a trend toward increase in [Mg(2+)] in posterior brain. In MWA, phosphocreatine concentration ([PCr]) was decreased to a minor degree in anterior brain regions and a trend toward decreased [Mg(2+)] was observed in posterior slice 1, but no consistent changes were found in phosphomonoester concentration [PME], [PDE], inorganic phosphate concentration ([Pi]), or pH. In hemiplegic migraine patients, [PCr] had a tendency to be lower, and [Mg(2+)] was significantly lower than in the posterior brain regions of control subjects. Trend analysis showed a significant decrease of brain [Mg(2+)] and [PDE] in posterior brain regions with increasing severity of neurologic symptoms.

CONCLUSIONS

Overall, the results support no substantial or consistent abnormalities of energy metabolism, but it is hypothesized that disturbances in magnesium ion homeostasis may contribute to brain cortex hyperexcitability and the pathogenesis of migraine syndromes associated with neurologic symptoms. In contrast, migraine patients without a neurologic aura may exhibit compensatory changes in [Mg(2+)] and membrane phospholipids that counteract cortical excitability.

Topiramate in migraine prevention: a double-blind, placebo-controlled study

OBJECTIVE

To evaluate the efficacy of topiramate in the preventative treatment of episodic migraine.

BACKGROUND

Topiramate is a broad-spectrum antiepileptic drug effective for treatment of multiple seizure types in adults and children. Antiepileptic agents have demonstrated efficacy in migraine prevention, and open-label experience from our clinic has suggested that topiramate might be effective for this use. We consequently conducted a single-center, double-blind, placebo-controlled trial to evaluate the efficacy and safety of topiramate for the preventative treatment of migraine.

METHODS

Forty patients, aged 19 to 62 years (mean, 38.2 years), were randomly assigned in a 1:1 ratio to receive topiramate (n = 19; all women) or placebo (n = 21; 20 women, 1 man). Following a prospective baseline phase of 4 weeks, the study drug dose was titrated weekly in 25-mg increments over 8 weeks to 200 mg per day or to the maximum tolerated dose. The titration phase was followed by an 8-week maintenance phase.

RESULTS

During the entire double-blind phase, topiramate-treated patients experienced a significantly lower 28-day migraine frequency (3.31 +/- 1.7 versus 3.83 +/- 2.1; P =.002) compared to placebo, irrespective of use of concomitant migraine prevention medications. The mean 28-day migraine frequency was reduced by 36% in patients receiving topiramate as compared with 14% in patients receiving placebo (P =.004). Twenty-six percent of the patients on topiramate and 9.5% of the patients on placebo achieved a 50% reduction in migraine frequency (P >.05). The mean dose of topiramate was 125 mg per day (range, 25 to 200 mg per day). Topiramate was well tolerated; 2 of 19 topiramate-treated patients discontinued treatment due to adverse events. Adverse effects that occurred more frequently in topiramate-treated patients included paresthesia, weight loss, altered taste, anorexia, and memory impairment.

CONCLUSIONS

Preventative therapy with topiramate significantly reduced migraine frequency. Larger multicenter clinical studies may further delineate the role of topiramate in migraine prevention.

Magnetoencephalographic fields from patients with spontaneous and induced migraine aura

We investigate and characterize the magnetoencephalographic waveforms from patients during spontaneous and visually induced migraine aura. Direct current neuromagnetic fields were measured during spontaneous onset of migraine auras in 4 migraine patients, and compared with recordings from 8 migraine-with-aura patients and 6 normal controls during visual stimulation of the occipital cortex. Complex direct current magnetoencephalographic shifts, similar in waveform, were observed in spontaneous and visually induced migraine patients, but not in controls. Two-dimensional inverse imaging showed multiple cortical areas activated in spontaneous and visually induced migraine aura patients. In normal subjects, activation was only observed in the primary visual cortex. Results support a spreading, depression-like neuroelectric event occurring during migraine aura that can arise spontaneously or be visually triggered in widespread regions of hyperexcitable occipital cortex.

Spectral analysis of visual potentials evoked by pattern-reversal checkerboard in juvenile patients with headache

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.

The pathophysiology of migraine

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.

Non-linear electroencephalogram dynamics in patients with spontaneous nocturnal migraine attacks

The present study was conducted to examine non-linear electroencephalogram (EEG) measures during the development of a spontaneous migraine attack. We investigated the sleep EEG of five patients with migraine without aura in the pain-free interval and at the onset of a nocturnal attack. Sleep EEG recordings were analysed using the method of global dimensional complexity compared to conventional sleep scoring techniques. We found no divergence between classical sleep architecture and the estimated dimensional course nor any relevant short-term changes related to the onset of headache. There was, however, a loss of dimensional complexity in the first two non-rapid eye movement sleep states in the migraine night, with statistical significance during the second sleep cycle. For the first time, these results provide evidence of a global dimension decrease that is related to cortical network changes during a migraine attack.

Safety and rational use of the triptans

The safety of the triptans has been established, with more than 8 million patients treating greater than 340 million attacks with sumatriptan alone. All triptans narrow coronary arteries by 10% to 20% at clinical doses and should not be administered to patients with coronary or cerebrovascular disease. Some triptans have the potential for significant drug-drug interactions (sumatriptan, rizatriptan, and zomitriptan and monoamine oxidase inhibitors; rizatriptan and propanolol; zolmitriptan and cimetidine; and eletriptan and CYP3A4 metabolized medications and p-glycoprotein pump inhibitors). Rational use of triptans should be governed by the use of these medications for patients with disability associated with migraine. Patients with greater than 10 days of at least 50% disability during 3 months have benefited from treating with triptans as their first-line treatment for acute attacks. When the decision has been made to treat with a triptan, the patient should be instructed to treat early in the attack, when the pain is at a mild phase. This approach increases the likelihood of achieving a pain-free response, with fewer adverse events and lower likelihood of the headache recurring.

Chronic daily headache in the posttrauma syndrome: relation to extent of head injury

OBJECTIVE

To evaluate the occurrence of continued intermittent headache and chronic daily headache in patients with head injury and the relationship between severity of the headache problem and intensity of the head injury.

BACKGROUND

In the majority of patients with posttraumatic headache, the condition is self-limited, but a minority of patients may develop persistent headaches. The features of posttraumatic headache may vary, but the most distressing type is the chronic daily headache. This study evaluates occurrence of chronic daily headache in relation to the intensity of head injury.

METHODS

All patients with head injury who were seen by the senior author (J.R.C.) in the Southern Illinois University Medical School (SIUMS) Neurology Clinic between 1980 and 1991 were identified from the SIUMS headache registry. Data on headache status before and after head injury was obtained, and patients with more than one headache per week before head injury were excluded. Each patient's headache status at the time of the clinic visit was classified as chronic daily headache (headache occurring at least 5 of 7 days for 6 months), intermittent migraine, or no headache. Head injury severity was graded by duration of loss of consciousness or amnesia as minimal (less than 5 minutes), mild (5 to 60 minutes), moderate (1 to 24 hours), or severe (more than 24 hours).

RESULTS

There was an inverse relation between extent of head injury and occurrence of chronic daily headache. For minimal head injury (n = 54), 80% had chronic daily headache, and 11% had no headache, while for moderate/severe head injury (n = 23), only 27% had chronic daily headache, and 68% had no headache (P<.001, chi2).

CONCLUSION

This study suggests that the risk of developing posttraumatic chronic daily headache is greater for less severe head injury compared with moderate/severe head injury. The reason for this relation is unclear.

Pathophysiology of migraine headache

The underlying mechanism of migraine and pain has been unraveled recently with the advent of neuroimaging. In this article mechanism of migraine aura and the pain of migraine are discussed. In addition, interictal studies demonstrating hyperexcitability in migraine are reviewed.

Quantitative EEG responses to ischaemic arm stress in migraine

Several studies suggest that patients with migraine respond physiologically to stress differently from controls, yet experimental data are scarce. In order to evaluate the reactivity to stress in migraine, we recorded the quantitative electroencephalogram (qEEG) during non-noxious and noxious ischaemic arm stress in two groups of healthy controls and compared the results with the effects of non-noxious ischaemic arm stress in a group of patients with migraine. In the controls, non-noxious mild stress did not produce any qEEG change but noxious stress induced a significant decrease of the alpha power. By contrast, in migraine patients the non-noxious mild stress was sufficient to induce a significant decrease of the alpha power in all brain regions. The results of our study show that migraine sufferers display a lower threshold to physical stress and confirm previous studies indicating that migraine is a disease characterized by a state of altered neuronal excitability.

Aminergic tone correlates of migraine and tension-type headache: a study using the tridimensional personality questionnaire

BACKGROUND

Aminergic neurotransmitter activity has been studied in many neuropsychiatric diseases by means of a self-administered questionnaire proposed by Cloninger. Given that central aminergic modulation plays a major role in the pathophysiology of primary headaches, we investigated the personality dimensions related to aminergic neurotransmitter activity in patients with migraine and tension-type headache.

METHODS

From a consecutive series of 230 patients, we selected those presenting with migraine and tension-type headache according to the International Headache Society criteria. All patients were assessed by means of the Cloninger 100-item self-report Tridimensional Personality Questionnaire and a depression scale. The four dimensions of personality are novelty seeking (dopaminergic), harm avoidance (serotonergic), reward dependence (noradrenergic), and persistence (glutaminergic).

RESULTS

One hundred twenty-one patients presenting with migraine and 42 with tension-type headache were recruited. The results indicate significantly higher harm avoidance scores (P<.001) in both patients with migraine and those with tension-type headache than in controls. Furthermore, patients with migraine had a significantly low score in the novelty seeking dimension (P<.001). When we compared only the two groups of patients with headache, we found that the persistence dimension alone was significantly higher in patients with migraine than in those with tension-type headache (P<.05). No differences were observed either in the overall scores of the other personality dimensions or in the depression scale scores.

CONCLUSIONS

The Tridimensional Personality Questionnaire results support a role of the serotonergic system in both migraine and tension-type headache pathophysiology. A dysfunction of dopaminergic and glutaminergic tone seems to be a specific feature of migraine.

Treatment of chronic daily posttraumatic headache with divalproex sodium

OBJECTIVE

To determine the effectiveness of divalproex sodium in the treatment of chronic daily posttraumatic headaches.

BACKGROUND

Divalproex sodium has been found to be useful for the treatment of migraine and chronic daily headache. No studies have been done to evaluate effectiveness in posttraumatic headache.

METHODS

A retrospective review was done of 100 patients treated with divalproex for chronic daily posttraumatic headache of 2 months or longer.

RESULTS

Sixty percent of patients with chronic posttraumatic headache had mild to moderate improvement in their headaches after at least 1 month of divalproex sodium. Forty percent either showed no response (26%) or discontinued treatment because of side effects (14%). Fifty-eight percent of patients showing improvement had a change in headache pattern from daily to episodic.

CONCLUSIONS

Divalproex sodium appears to be safe and effective for treatment of patients with persistent, chronic daily posttraumatic headaches.

NiCl2 and amiloride induce spreading depression in guinea pig hippocampal slices

Spreading depressions (SD) occur in association with ischaemia, epilepsy and migraine. Intracellular calcium oscillations have been suggested to be involved in the generation and propagation of SD. The present study was performed to study the mechanism of conditioning guinea pig hippocampal slices by the T-type calcium channel blockers NiCl2 and amiloride. SD-like fluctuations of DC potential were recorded by inserting microelectrodes into the CA1 and CA3 regions. The SD occurrence was significantly greater with 10 micromol/l NiCl2 as well as with 25 and 50 micromol/l amiloride than with other concentrations of these substances. The concentration response curve was inversely U-shaped with the maximum repetition rates of SDs being achieved at 10 micromol/l NiCl2 as well as at 25 and 50 micromol/l amiloride. SD occurrence could be completely blocked by the NMDA antagonist APV (10 micromol/l) in all cases. These data demonstrate that modulation of the Ca2+ dynamics conditioned guinea pig hippocampal slices and increased their susceptibility to generate SD.

Migraine: imaging the aura

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.

The wavelength of light causing photophobia in migraine and tension-type headache between attacks

OBJECTIVE

To ascertain the wavelength of light that patients with migraine and tension-type headache find uncomfortable between attacks.

BACKGROUND

Photophobia is an abnormal perceptual sensitivity to light experienced by most patients with headache during and, also, between attacks.

METHODS

We examined the discomfort threshold to light of low, medium, and high wavelengths in a group of patients with migraine (n=21), patients with tension-type headache (n=19), and healthy controls (n=21).

RESULTS

The results indicate that the migraine group had significantly lower discomfort thresholds at the low (P=.001) and high (P=.031) wavelengths compared with both the tension-type headache and control groups; the latter two groups had similar average discomfort levels at these two wavelengths. With the medium wavelength, the control group had significantly higher discomfort thresholds than the migraine (P=.002) and tension-type headache (P=.031) groups; the latter two groups had similar discomfort levels at this wavelength. With unfiltered (white) light, the migraine group had the lowest discomfort threshold and the control group the highest (P=.026), whereas the tension-type headache group had an intermediate discomfort threshold.

CONCLUSIONS

There were significant differences between migraineurs, patients with tension-type headache, and healthy controls in the wavelengths that are uncomfortable between attacks.

Motor cortex excitability in patients with migraine with aura and hemiplegic migraine

We studied the excitability of the motor cortex using transcranial magnetic stimulation (TMS) in 12 patients with migraine with aura (MA) and nine patients with familial hemiplegic migraine (FHM). Motor thresholds at rest, the duration of the cortical and peripheral silent period and intracortical inhibition and facilitation using paired-pulse TMS at intervals of 2 to 15 ms were measured with patients free of attacks for at least 48 h. In contrast to previous reports we could not find any significant differences between patient groups and compared to controls (n=17) in the parameters tested. The results suggest that there are no interictal changes of excitability of the motor cortex in migraine. This study does not support the concept of general cortical hyperexcitability in migraine secondary to a genetic predisposition or a structural alteration of inhibitory interneurones in the cortex due to repeated parenchymal insults during attacks.

Orientation discrimination thresholds in migraine: a measure of visual cortical inhibition

Orientation discrimination is a visual task dependent on inhibitory mechanisms in the visual cortex. In this study, orientation discrimination thresholds for bar and grating patterns were measured at two visual field locations in subjects with migraine with (n = 20) and without aura (n = 20) and in migraine-free control subjects (n = 20). No statistically significant differences were found between migraine groups and the control group on either task at foveal or peripheral visual field locations. No significant correlations were found between psychophysical thresholds and age, total lifetime auras or total lifetime migraine episodes. However, a trend was seen toward slightly impaired performance on the two foveal tasks in a subgroup of subjects with the highest total lifetime aura count. Thus we have found no convincing evidence that impaired cortical inhibitory mechanisms are a predisposing characteristic in migraine, but cannot rule out the possibility that cortical inhibitory mechanisms may be adversely affected by repeated visual auras.

Abnormal visual evoked potentials in children with "Alice in Wonderland" syndrome due to infectious mononucleosis

Visual illusions characterized by distortion of form, size, reciprocal position of objects, movement, or color, labeled as "Alice in Wonderland" syndrome, were discussed in children with infectious mononucleosis, as well as in other clinical conditions, such as migraine, epilepsy, use of certain hallucinogenic drugs, etc. The purpose of our study was to investigate for the first time visual evoked potential results in children with "Alice in Wonderland" syndrome associated with infectious mononucleosis. Five children with "Alice in Wonderland" syndrome associated with infectious mononucleosis underwent visual evoked potential studies during and after their clinical symptoms. Visual evoked potential results during the disease demonstrated statistically significant high amplitudes of P100-N145 in all children compared to the control group. A few weeks later, repeated studies after the resolution of the complaints were normal. Since the same findings can be observed in patients with migraine, we postulate that a common pathophysiologic underlying abnormality, which can cause transient focal decreased cerebral perfusion, could be involved in the disease process of these two conditions.

Evidence based migraine prophylactic drug therapy

Prophylactic drug therapy is a major component of overall migraine management. However, because we do not know how currently used prophylactic drugs exert their beneficial effects in migraine, their use is based primarily on clinical trials. In general, prophylactic drugs are indicated when patients have three or more attacks a month and symptomatic medication use alone is not satisfactory. The choice of drug must be individualized, and is influenced by contraindications, potential side effects, the need to treat associated symptoms like tension-type headache and insomnia, and drug cost. Whether an individual patient will respond to a given drug cannot be predicted, but there are varying degrees of scientific evidence supporting the use of each prophylactic drug in migraine. This evidence is best for metoprolol, divalproex, amitriptyline, atenolol, flunarizine and naproxen. Based on placebo-controlled crossover studies, it would appear that at least some prophylactic drugs exert the greater part of their prophylactic effects very quickly, and that these also disappear very quickly once the drug is stopped. This may not apply to all prophylactic drugs and more research is needed. More well designed clinical trials are needed to guide our use of migraine prophylactic drugs. Although clinical experience is useful, placebo responses and variations in the migraine tendency over time can make interpretation of this experience difficult. Major advances will likely only occur once the pathogenesis of migraine and the mode of action of the prophylactic drugs is better understood.

Analysis of MEG signals of spreading cortical depression with propagation constrained to a rectangular cortical strip. I. Lissencephalic rabbit model

Magnetic fields arising from the rabbit cortex during spreading cortical depression (SCD) were measured in order to study the currents in the neocortex during SCD. SCD was constrained to propagate in a rectangular cortical strip perpendicular to the midline. This simplified in vivo cortical preparation enabled us to correlate magnetoencephalographic (MEG) signals to their underlying currents within the cortical strip. The propagation of SCD was monitored with an array of electrodes placed along the strip. The propagation speed for SCD in the lissencephalic rabbit brain was 3. 5+/-0.3 mm/min (mean+/-S.E.M., n=14). Slow, quasi-dc, MEG signals were observed as the SCD entered into the longitudinal fissure. The currents giving rise to the MEG signals were perpendicular to the cortical surface and directed from the surface to deeper layers of the cortex. A distributed dipolar source model was used to relate the data to the underlying cortical current. The moment of the single equivalent current dipole source was 38+/-9 nA-m (n=17). This study clarified the nature of the cortical currents during SCD in a lissencephalic in vivo preparation.

The cortical silent period is shortened in migraine with aura

OBJECTIVES

Central neuronal hyperexcitability may be the physiological disturbance that predisposes subjects to migraine attacks. To test this hypothesis, we studied the cortical stimulation silent period (CSSP) elicited by transcranial magnetic stimulation (TMS), which is in part a measure of central inhibition of motor pathways in migraine with aura (MwA) patients and normal controls.

METHODS

In nine MwA patients (mean age 35.9 +/- 7) and 9 controls (mean age 37.6 +/- 7), we carried out transcranial stimulation using a 95 mm circular coil and Caldwell MES 10 stimulator to determine resting motor threshold (MT) for bilateral FDI muscles. All subjects performed isometric voluntary contraction of bilateral FDI maintained at 20% of maximal effort, during which we measured bilateral CSSP at (i) the stimulus intensity (SI) determined for the MT and (ii) an SI of 1.5 x MT.

RESULTS

Although the mean MT was higher in MwA compared with controls (63.1 +/- 14.4 vs 58.1 +/- 8.9), the difference was not significant. At an SI of 1.5 x MT the mean CSSP did not differ between the groups (MwA 141.7 +/- 31.9 vs controls 162.4 +/- 36.6). At the SI of the MT, however, the CSSP was shorter in MwA patients than in controls (62.9 +/- 27.3 vs 106.3 +/- 19.6, p = 0.001). There was an inverse correlation between the duration of CSSP and an increased frequency of headache (p = 0.02).

CONCLUSIONS

The shortened CSSP that we measured in MWA patients compared to normal with low intensity magnetic stimulation suggests reduced central inhibition resulting in increased excitability of cortical neurons in migraine subjects. The association of CSSP reduction with increased frequency of migraine is further suggestive that brain excitability is the basis of susceptibility to migraine attacks.

Ischemic stroke and migraine in childhood: coincidence or causal relation?

Although migraine is an accepted cause of cerebral infarction in adults, this association is less well recognized in children. We present two children with migraine and cerebral infarction, which we regard as migrainous stroke, though neither patient fulfills all criteria of the International Headache Society for the diagnosis of migrainous infarction. Review of the literature concerning examples of migraine-associated stroke in childhood suggests that these criteria are too restrictive to comprise the majority of migrainous strokes, especially in this age group.

Effectiveness of lamotrigine in the prophylaxis of migraine with aura: an open pilot study

We report a small open pilot study to evaluate the efficacy of lamotrigine (100 mg/day) in the prevention of migraine with aura attacks. We studied 24 patients affected by migraine with aura with a high frequency of attacks. Following a 1-month run-in period, the patients took lamotrigine for 3 months. Mean attack number per month was reduced from 6.1 +/- 4.1 during the run-in period to 0.7 +/- 1.3 at the 3rd month of treatment (p < 0.0001). In 13 out of 21 patients who completed the study, the attacks were completely abolished at the 3rd month of treatment, while only one patient was completely unresponsive to the drug. Lamotrigine seems worthy of a controlled trial as prophylaxis of a migraine with aura.

Interictal cortical excitability in migraine: a study using transcranial magnetic stimulation of motor and visual cortices

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.

EEG spectral analysis in migraine without aura attacks

In 16 patients suffering from migraine without aura, we examined quantitative EEG and steady-state visual evoked potentials (SSVEPs) at 27 Hz stimulation during the critical phase of migraine and in attack-free periods. The main spontaneous EEG abnormalities found during the critical phase were the slowing and asymmetry of the dominant frequency in the alpha range. The amplitude of the SSVEP F1 component was significantly reduced during the attack phase compared with the intercritical phase; in the latter condition the visual reactivity to 27 Hz stimulus was increased over almost the entire scalp compared with normal subjects. The EEG abnormalities confirm a fluctuating modification of alpha activity during the migraine attack, probably related to a functional disorder. The suppression of visual reactivity during the migraine attack could be related to a phenomenon of neuronal depolarization such as spreading depression, occurring in a situation of central neuronal increased excitability predisposing to migraine attacks.

Brain excitability in migraine: evidence from transcranial magnetic stimulation studies

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.

Migraine and ovarian steroid hormones

This chapter reviews clinical and epidemiological data that support a role for ovarian steroid hormones in the migraine syndrome. Changes in the clinical presentation of migraine are discussed on the basis of current knowledge of biochemistry and pharmacology of ovarian steroids. Finally, special treatment considerations of ovarian hormone-sensitive migraine are discussed.

Sumatriptan blocks spreading depression in isolated chick retina

Spreading depression is a neurohumoral phenomenon that has been related to the pathophysiology of migraine. The recently introduced 5HT1D agonist anti-migraine compound sumatriptan blocks neurogenic extravasation and induces cerebral vasoconstriction, but the actual mechanism of action against migraine remains obscure. Retinal spreading depression (RSD) velocity has been measured in isolated chick retinas in the presence of 0.05-2.00 mM sumatriptan. This drug reversibly blocks RSD in a concentration-dependent manner. Since the preparation is blood-vessel free, this effect must be related to the nervous tissue.