Effects of Topiramate on Migraine Frequency and Cortical Excitability in Patients with Frequent Migraine

EEG Changes in Migraine-Can EEG Help to Monitor Attack Susceptibility?

Migraine is a highly prevalent brain condition with paroxysmal changes in brain excitability believed to contribute to the initiation of an attack. The attacks and their unpredictability have a major impact on the lives of patients. Clinical management is hampered by a lack of reliable predictors for upcoming attacks, which may help in understanding pathophysiological mechanisms to identify new treatment targets that may be positioned between the acute and preventive possibilities that are currently available. So far, a large range of studies using conventional hospital-based EEG recordings have provided contradictory results, with indications of both cortical hyper- as well as hypo-excitability. These heterogeneous findings may largely be because most studies were cross-sectional in design, providing only a snapshot in time of a patient's brain state without capturing day-to-day fluctuations. The scope of this narrative review is to (i) reflect on current knowledge on EEG changes in the context of migraine, the attack cycle, and underlying pathophysiology; (ii) consider the effects of migraine treatment on EEG features; (iii) outline challenges and opportunities in using EEG for monitoring attack susceptibility; and (iv) discuss future applications of EEG in home-based settings.

Cortical excitability in human somatosensory and visual cortex: implications for plasticity and learning - a minireview

The balance of excitation and inhibition plays a key role in plasticity and learning. A frequently used, reliable approach to assess intracortical inhibition relies on measuring paired-pulse behavior. Moreover, recent developments of magnetic resonance spectroscopy allows measuring GABA and glutamate concentrations. We give an overview about approaches employed to obtain information about excitatory states in human participants and discuss their putative relation. We summarize paired-pulse techniques and basic findings characterizing paired-pulse suppression in somatosensory (SI) and (VI) visual areas. Paired-pulse suppression describes the effect of paired sensory stimulation at short interstimulus intervals where the cortical response to the second stimulus is significantly suppressed. Simultaneous assessments of paired-pulse suppression in SI and VI indicated that cortical excitability is not a global phenomenon, but instead reflects the properties of local sensory processing. We review studies using non-invasive brain stimulation and perceptual learning experiments that assessed both perceptual changes and accompanying changes of cortical excitability in parallel. Independent of the nature of the excitation/inhibition marker used these data imply a close relationship between altered excitability and altered performance. These results suggest a framework where increased or decreased excitability is linked with improved or impaired perceptual performance. Recent findings have expanded the potential role of cortical excitability by demonstrating that inhibition markers such as GABA concentrations, paired-pulse suppression or alpha power predict to a substantial degree subsequent perceptual learning outcome. This opens the door for a targeted intervention where subsequent plasticity and learning processes are enhanced by altering prior baseline states of excitability.

OnabotulinumtoxinA Modulates Visual Cortical Excitability in Chronic Migraine: Effects of 12-Week Treatment

Chronic migraine is a burdensome disease presenting with episodic pain and several symptoms that may persist even among headache attacks. Multisensory integration is modified in migraine, as assessed by the level of the perception of sound-induced flash illusions, a simple paradigm reflecting changes in cortical excitability which reveals to be altered in migraineurs. OnabotulinumtoxinA is an effective preventive therapy for chronic migraineurs, reducing peripheral and central sensitization, and may influence cortical excitability. Patients affected by chronic migraine who started onabotulinumtoxinA preventive therapy were included. Clinical effects (headache diaries and migraine related questionnaires) were assessed at the beginning of the therapy and after 12 weeks. Contextually, patients underwent the evaluation of multisensory perception by means of the sound-induced flash illusions. OnabotulinumtoxinA showed effectiveness both in migraine prevention and in reducing headache burden. Even one session of therapy was able to restore, at least partially, multisensory processing, as shown by patients' susceptibility to the sound-induced flash illusion. OnabotulinumtoxinA could influence migraineurs cortical excitability concurrently to the beneficial effects in headache prevention.

Pharmacological treatment of migraine: Drug classes, mechanisms of action, clinical trials and new treatments

Migraine is the sixth most prevalent disease globally, a major cause of disability, and it imposes an enormous personal and socioeconomic burden. Migraine treatment is often limited by insufficient therapy response, leading to the need for individually adjusted treatment approaches. In this review, we analyse historical and current pharmaceutical development approaches in acute and chronic migraine based on a comprehensive and systematic analysis of Food and Drug Administration (FDA)-approved drugs and those under investigation. The development of migraine therapeutics has significantly intensified during the last 3 years, as shown by our analysis of the trends of drug development between 1970 and 2020. The spectrum of drug targets has expanded considerably, which has been accompanied by an increase in the number of specialised clinical trials. This review highlights the mechanistic implications of FDA-approved and currently investigated drugs and discusses current and future therapeutic options based on identified drug classes of interest.

Relationships between migraine and epilepsy: Pathophysiological mechanisms and clinical implications

Migraine and epilepsy are distinct neurological diseases with specific clinical features and underlying pathophysiological mechanisms. However, numerous studies have highlighted the complex and multifaceted relationships between the two conditions. The relationships between headache and epilepsy manifest themselves in different ways. Firstly, the clinical diagnosis of these disorders may be challenging in view of possible overlapping. While post-ictal headache is a frequent condition, ictal epileptic headache is a rare but challenging diagnosis. Both situations raise the question of the pathophysiological mechanism of headache triggered by seizures. Migraine aura and epilepsy can also exhibit overlapping symptoms leading to their misdiagnosis, in particular in the case of visual aura. Secondly, migraine with aura and epilepsy can occur as a co-morbid condition, particularly in familial hemiplegic migraine (FHM). From a pathophysiological perspective, the identification of genetic mutations in FHM has brought significant advances in the understanding of dysfunctions of neuronal networks leading to hyperexcitability. The purpose of this review is to present clinical situations encompassing headache and epilepsy that can be challenging in neurological practice and to discuss the underlying pathophysiological mechanism of such interactions.

Cortical excitability controls the strength of mental imagery

Mental imagery provides an essential simulation tool for remembering the past and planning the future, with its strength affecting both cognition and mental health. Research suggests that neural activity spanning prefrontal, parietal, temporal, and visual areas supports the generation of mental images. Exactly how this network controls the strength of visual imagery remains unknown. Here, brain imaging and transcranial magnetic phosphene data show that lower resting activity and excitability levels in early visual cortex (V1-V3) predict stronger sensory imagery. Further, electrically decreasing visual cortex excitability using tDCS increases imagery strength, demonstrating a causative role of visual cortex excitability in controlling visual imagery. Together, these data suggest a neurophysiological mechanism of cortical excitability involved in controlling the strength of mental images.

Amelioration of Behavioral Impairments and Neuropathology by Antiepileptic Drug Topiramate in a Transgenic Alzheimer's Disease Model Mice, APP/PS1

Alzheimer's disease (AD) is a neurodegenerative disease that is the main cause of dementia in the elderly. The aggregation of β-amyloid peptides is one of the characterizing pathological changes of AD. Topiramate is an antiepileptic drug, which in addition, is used in the treatment of many neuropsychiatric disorders. In this study, the therapeutic effects of topiramate were investigated in a transgenic mouse model of cerebral amyloidosis (APP/PS1 mice). Before, during, and after topiramate treatment, behavioral tests were performed. Following a treatment period of 21 days, topiramate significantly ameliorated deficits in nest-constructing capability as well as in social interaction. Thereafter, brain sections of mice were analyzed, and a significant attenuation of microglial activation as well as β-amyloid deposition was observed in sections from topiramate-treated APP/PS1 mice. Therefore, topiramate could be considered as a promising drug in the treatment of human AD.

Contributions of Nociresponsive Area 3a to Normal and Abnormal Somatosensory Perception

Traditionally, cytoarchitectonic area 3a of primary somatosensory cortex (SI) has been regarded as a proprioceptive relay to motor cortex. However, neuronal spike-train recordings and optical intrinsic signal imaging, obtained from nonhuman sensorimotor cortex, show that neuronal activity in some of the cortical columns in area 3a can be readily triggered by a C-nociceptor afferent drive. These findings indicate that area 3a is a critical link in cerebral cortical encoding of secondary/slow pain. Also, area 3a contributes to abnormal pain processing in the presence of activity-dependent reversal of gamma-aminobutyric acid A receptor-mediated inhibition. Accordingly, abnormal processing within area 3a may contribute mechanistically to generation of clinical pain conditions. PERSPECTIVE: Optical imaging and neurophysiological mapping of area 3a of SI has revealed substantial driving from unmyelinated cutaneous nociceptors, complementing input to areas 3b and 1 of SI from myelinated nociceptors and non-nociceptors. These and related findings force a reconsideration of mechanisms for SI processing of pain.

Chronic Migraine: An Update on Physiology, Imaging, and the Mechanism of Action of Two Available Pharmacologic Therapies

Several lines of research support the hypothesis that migraine is a spectrum of illness, with clinical symptoms that vary along a continuum from episodic migraine to chronic migraine. Physiologic changes may result in episodic migraine evolving into chronic migraine over months to years in susceptible individuals. With chronification, headache frequency increases, becoming more disabling and less responsive to therapy. Neurophysiologic and functional imaging research has reported that chronic migraine may be associated with severity‐specific metabolic, functional, and structural abnormalities in the brainstem. Without longitudinal studies, it is unclear whether these changes may represent a continuum of individual progression and/or are reversible. Furthermore, chronic migraine is associated with larger impairments in cortical processing of sensory stimuli when compared with episodic migraine, possibly caused by more pronounced cortical hyperexcitability.

Progressive changes in nociceptive thresholds and subsequent central sensitization due to recurrent migraine attacks in vulnerable individuals contribute to the chronic migraine state. This may result in changes to baseline neurologic function between headache attacks, evident in both electrophysiological and functional imaging research. Patients experiencing migraine chronification may report increased non‐headache pain, fatigue, psychiatric disorders (eg, depression, anxiety), gastrointestinal complaints, and other somatic conditions associated with their long‐term experience with migraine pain.

Recent research provides a foundation for differentiating episodic and chronic migraine based on neurophysiologic and neuroimaging tools. In this literature review, we consider these findings in the context of models designed to explain the physiology and progression of episodic migraine into chronic migraine, and consider treatment of chronic migraine in susceptible individuals. Advances in pharmacotherapy provide treatment options for chronic migraine. Of the currently available treatment options, only onabotulinumtoxinA and topiramate have received regulatory approval and have demonstrated efficacy in patients with chronic migraine, although the exact mechanisms of action are not fully elucidated.

Brain stimulation in migraine

Migraine is a very prevalent disease with great individual disability and socioeconomic burden. Despite intensive research effort in recent years, the etiopathogenesis of the disease remains to be elucidated. Recently, much importance has been given to mechanisms underlying the cortical excitability that has been suggested to be dysfunctional in migraine. In recent years, noninvasive brain stimulation techniques based on magnetic fields (transcranial magnetic stimulation, TMS) and on direct electrical currents (transcranial direct current stimulation, tDCS) have been shown to be safe and effective tools to explore the issue of cortical excitability, activation, and plasticity in migraine. Moreover, TMS, repetitive TMS (rTMS), and tDCS, thanks to their ability to interfere with and/or modulate cortical activity inducing plastic, persistent effects, have been also explored as potential therapeutic approaches, opening an interesting perspective for noninvasive neurostimulation for both symptomatic and preventive treatment of migraine and other types of headache. In this chapter we critically review evidence regarding the role of noninvasive brain stimulation in the pathophysiology and treatment of migraine, delineating the advantages and limits of these techniques together with potential development and future application.

Visual cortex excitability and plasticity associated with remission from chronic to episodic migraine

OBJECTIVE

Previous magnetoencephalographic (MEG) studies showed different P100m (where 'm' denotes the magnetic counterpart of P100 in conventional visual evoked potentials) responses between episodic migraine (EM) and chronic migraine (CM) interictally. This study investigated the changes of visual P100m in CM patients who remitted to EM from CM after treatment.

METHODS

At baseline, 25 patients with CM were studied interictally. For each patient, 30 sequential blocks of 50 P100m responses were obtained by MEG. Sub-averaged amplitudes at blocks 2, 9, 16, 23 and 30 were further compared with that at block 1 to assess response habituation or potentiation (i.e. significant decrease or increase at either block vs block 1). The same study was repeated in those patients who remitted from CM to EM after topiramate treatment.

RESULTS

In total, 10 CM patients remitted to EM after treatment. In the follow-up study of these patients during the interictal stage, the P100m at block 1 decreased in amplitude from 53.6 ± 6.6 nAm before remission to 43.0 ± 5.1 nAm (p = 0.028), and the responses at subsequent blocks switched from habituation (amplitude block 30 < block 1 before remission, p = 0.011) to potentiation (block 2 > block 1, p = 0.028).

CONCLUSION

The pattern of P100m responses to consecutive stimulation changes with the transition from CM to EM. Visual cortex plasticity might be a potential biomarker reflecting clinical remission of CM.

The first phase of a migraine attack resides in the cortex

Migraine headache is generated by the complex interaction of various players such as genetic predisposition, environmental triggers and intrinsic factors. The initial mechanism of a migraine attack has long been a controversial topic and exploring its origin is a challenging task. The scientific evidences so far indicate neuronal dysfunction in the cerebral cortex and particularly cortical spreading depression waves, as upstream to cascade of events leading to a migraine attack. Neocortex, evolutionary valuable part of the brain, is surrounded by pain sensing system that is finely tuned for detecting noxious signals. Abnormal functioning of more than one cortical area in migraineurs may suggest that hyperexcitable neocortex could be more easily challenged, overreacts and depolarize to repetitive sensorial stimuli and could switch to extreme excitability state where spreading depression waves occur. In this paper, I will review the data supporting the notion that migraine is a neuronal disorder where cortex has prime importance. Despite clear demonstration of cortical participation in migraine, the contribution of brain structures other than cortex to the development of migraine remains unclear.

Beta-blocker migraine prophylaxis affects the excitability of the visual cortex as revealed by transcranial magnetic stimulation

The objective of this study is to assess effects of beta-blocker migraine prophylaxis on cortical excitability determined by transcranial magnetic stimulation (TMS). Phosphene and motor thresholds (PT, MT) were investigated in 29 patients with migraine, in 15 of them prior to and following preventive medication with metoprolol and in 14 patients without prophylaxis. Following prophylaxis headache frequency significantly decreased (p = 0.005) and mean PT were significantly increased (51.5 ± 7.5 vs. 63.6 ± 8.4%) compared to patients without preventive treatment (53.7 ± 5.3 vs. 52.3 ± 6.3%; p = 0.040). Mean MT did not significantly differ either between groups or due to treatment. In the group of all patients, a significant inverse correlation between headache frequency and the level of PT was found (R = -0.629; p < 0.01). There was, however, no significant correlation in the subgroups of patients. We conclude that (a) clinical efficacy of beta-blocker treatment in migraine could be (at least partly) linked to its ability to modulate the excitability of the visual cortex and (b) the PT determined by TMS appears suitable to assess the effects of prophylaxis on cortical excitability in the individual patient. This may be useful in clinical trials investigating migraine preventive drugs.

Efficacy and tolerability of pregabalin versus topiramate in the prophylaxis of chronic daily headache with analgesic overuse: an open-label prospective study

OBJECTIVES

Medication-overuse headache is one of the most disabling headaches. Antiepileptic drugs have been considered a promising strategy as prophylactic treatment in these patients, even if their use often has been limited by low tolerability or safety. The objective of this study was to evaluate the efficacy and safety of pregabalin compared with topiramate for the prophylaxis of chronic daily headache with medication overuse using an open-label prospective study.

METHODS

After a 2-month baseline period (T0), 100 consecutive patients with medication overuse headache were assigned to receive 150 mg/d pregabalin or 100 mg/d topiramate. After a titration period of 4 weeks, a follow-up visit was scheduled every 2 months (T1 and T2) to evaluate headache frequency, the amount of rescue medication intake, and disability.

RESULTS

Of the 46 pregabalin-treated patients, the mean monthly headache frequency significantly decreased from 21.8 ± 4.8 (T0) to 5.1 ± 3.8 (T2), and the monthly number of days with medication intake decreased from 15.1 ± 4.8 (T0) to 2.9 ± 1.9 (T2). Similarly, of the 42 topiramate-treated patients, the mean monthly headache frequency decreased from 21.8 ± 4.9 (T0) to 5.3 ± 3.5 (T2), and the mean monthly number of days with medication intake decreased from 15.1 ± 3.7 (T0) to 2.6 ± 1.5 (T2). A significant improvement of disability score was reported in both groups.

CONCLUSIONS

Similar to topiramate, pregabalin seems to be an effective and well-tolerated preventive therapy in chronic headache and a new option in the management of withdrawal from abused drugs in patients with analgesic overuse, a difficult-to-treat population.

New drugs in migraine treatment and prophylaxis: telcagepant and topiramate

Although the triptan drugs provide effective relief from migraine for many patients, a substantial number of affected individuals are unresponsive to these compounds, and such therapy can also lead to a range of adverse effects. Telcagepant represents a new class of antimigraine drug-the calcitonin gene-related peptide receptor blockers. This compound exerts its effects by blocking receptors for the calcitonin-gene-related peptide at several sites in the trigeminal and central nervous systems, resulting in pain relief. Telcagepant does not cause vasoconstriction, a major limitation in the use of triptans. Comparisons with triptans in clinical trials for acute treatment of migraine attacks revealed clinical effects similar to those of triptans but better than those of placebo. Telcagepant might provide hope for those who have a poor response to, or are unable to use, older drugs. In patients who need prophylaxis because of frequent attacks of migraine, topiramate is a first-line drug for migraine prevention in many countries; it is generally safe and reasonably well tolerated. Data suggest that topiramate could aid reversion of chronic migraine to episodic migraine.

New drugs for migraine

After the triptans, a calcitonin gene-related peptide blocker (telcagepant) is the first acute medicine that has been developed primarily for treatment of acute migraine. Otherwise, the new drugs have been developed first for other purposes, like anticonvulsants, antihypertensives and antidepressants used for migraine prophylaxis. For acute attacks, a new way to administer a traditional drug like dihydroergotamine is under way, and documentation of efficacy in migraine has been gained for some commonly used painkillers and anti-inflammatory drugs, and for some herbal extracts. Based on insights into the basic pathophysiological mechanisms of the disorder, some drugs have been developed which seem promising in early phase II studies (NOS inhibitors and 5HT1F-receptor agonists). In the future, development and enhancements of existing medicines must be accompanied by increased efforts to develop truly new migraine drugs based on knowledge of the pathophysiology if one wishes to reduce substantially the great burden migraine poses on patients and society.

Topiramate modulates excitability of the occipital cortex when measured by transcranial magnetic stimulation

Summary

The aim of this study was to measure differences in occipital cortex excitability in migraineurs before and after administration of topiramate. We have previously demonstrated occipital cortex hyperexcitability in migraine using an objective technique of magnetic suppression of perceptual accuracy (MSPA). We hypothesized that a neuromodulator such as topiramate would demonstrate differences in MSPA in migraine compared with baseline. Ten migraine patients were recruited. To assess inhibitory function MSPA was measured using the following protocol. Timed transcranial magnetic stimulation were delivered at interstimulus intervals (ISI) varying from 40 to 190 ms (eight stimulations at each ISI) at 60% stimulus intensity. Subjects were asked to report letters projected at a fixed luminance on the screen. Visual suppression was calculated based on the number of errors the subjects made using automated analysis. This procedure was repeated at a minimum of two different dosages of topiramate when it was titrated for optimal migraine control. The interim dose was that at which an improvement in headache frequency was first observed, and the optimal dose was that at which the patient had a ≥ 50% reduction in headache frequency, or had reached a 100-mg dose. The mean [standard error (s.e.)] level of letters reported correct at baseline at 100-ms ISI was 91.6 (3.4) compared with 48.5 (6.0) ( P = 0.001) at an optimal dose of topiramate. Dose ranged from 50 to 100 mg; the average dose was 75 mg. The interim dose for most patients was 50 mg; the mean (s.e.) percentage of letters reported correct at interim was 75.9 (6.2) compared with baseline ( P = 0.01). Mean number of headaches at baseline was 27 per month, compared with eight headaches per month at interim dose and four headaches per month at optimal dose. There was no significant correlation between mean change in frequency of headache and mean change in inhibition from baseline to optimal dose (0.04, P = 0.89). Topiramate modulates occipital cortex excitability in chronic migraine possibly via mechanisms of cortical inhibition. Since there was not a strong correlation between the degree of inhibition and reduction of migraine frequency, it would appear that topiramate did have an independent effect on cortical excitability that was not dependent on reduction in migraine frequency.

Oxcarbazepine for the treatment of binge eating disorder: a case series

We present a case series of nine obese outpatients with a diagnosis of binge eating disorder who were treated with a flexible dose of the anticonvulsant oxcarbazepine. The drug has not previously been used to treat this disorder. Five patients dropped out at various points of the study, giving only fragmented data. Where data were available, all patients reported side effects (n=7) and some showed a reduction (n=4) or no change (n=3) in binge episode frequency. Some patients lost weight over the study period (n=3; range, 3-5 kg); others showed no change (n=2) or an increase in weight (n=3; range, 1.8-2.9 kg). Our results were inconsistent, but the drug was effective for some patients who showed marked impulsivity in eating behaviours and depressive symptoms.