Brain activations in the premonitory phase of nitroglycerin-triggered migraine attacks

Pediatric vs. Adult Prodrome and Postdrome: A Window on Migraine Pathophysiology?

Few studies have been conducted on the prodromal and postdromal phases of the migraine attack in children and adolescents. Using a questionnaire, we found that 67% of 103 children and adolescents with migraine reported at least one prodromal symptom, with a mean number per subject of 1.8 (median 2.2). The most frequently reported prodromal symptoms were face changes, fatigue and irritability. In pediatric patients selected as having prodrome, fatigue, mood change and neck stiffness were the most frequently reported prodromal symptoms. Using a different design, Laurell et al. found that 71% of 137 pediatric patients reported at least one prodromal symptom with a mean number per subject of 1.9 ± 2.0. Studying postdrome was fraught with unexpected difficulties as our preliminary research showed. Patients reported 2 groups of symptoms occurring during the resolution phase of the headache: symptoms whose onset was before headache cessation and were persisting after it, and symptoms whose onset was after headache cessation. We referred to the former as persistent symptoms and to the latter as true postdromes. Ninety-one per cent of patients reported persistent symptoms, with a mean of 6.0 and a median of 2, asthenia, pallor, cognitive difficulties, anorexia, somnolence, and nausea being the more frequently reported. True postdromes were reported by 82% of patients, with a mean of 2.6 and a median of 2, thirst, somnolence, visual disturbances, food craving, paraesthesias, and ocular pain being the most frequent reported. Interestingly, several prodromal and postdromal symptoms are also encountered during the aura classic and/or accompany the headache phase. Functional imaging in migraine has showed that the activations in areas such as hypothalamus or brainstem may begin before headache onset and/or persist after headache relief. Thus, one may wonder whether prodromal and postdromal symptoms may indicate the involvement of the limbic system, dopaminergic pathways, the hypothalamus and the brainstem. Differences between children, adolescents and adults might contribute to the understanding of migraine neurobiology.

Functional connectivity of hypothalamus in chronic migraine with medication overuse

OBJECTIVE

To investigate the functional connectivity of the hypothalamus in chronic migraine compared to interictal episodic migraine in order to improve our understanding of migraine chronification.

METHODS

Using task-free fMRI and ROI-to-ROI analysis, we compared anterior hypothalamus intrinsic connectivity with the spinal trigeminal nucleus in patients with chronic migraine (n = 25) to age- and sex-matched patients with episodic migraine in the interictal phase (n = 22). We also conducted a seed-to-voxel analysis with anterior hypothalamus as a seed.

RESULTS

All patients with chronic migraine had medication overuse. We found a significant connectivity (T = 2.08, p = 0.024) between anterior hypothalamus and spinal trigeminal nucleus in the chronic group, whereas these two regions were not connected in the episodic group. The strength of connectivity was not correlated with pain intensity (rho: 0.09, p = 0.655). In the seed-to-voxel analysis, three regions were more connected with the anterior hypothalamus in the chronic group: The spinal trigeminal nuclei (MNI coordinate x = 2, y = -44, z = -62), the right dorsal anterior insula (MNI coordinate x = 10, y = 10, z = 18), and the right caudate (MNI coordinate x = 12, y = 28, z = 6). However, these correlations were no longer significant after whole brain FWE correction.

CONCLUSION

An increased functional connectivity between the anterior hypothalamus and the spinal trigeminal nucleus, as previously reported in preictal episodic migraine, was demonstrated in chronic migraine with medication overuse. This finding confirms a major role of the anterior hypothalamus in migraine and suggests that chronic migraineurs are locked in the preictal phase.

Age related metabolic modifications in the migraine brain

Purpose

The aim of this study was to evaluate the possibility that migraine patients exhibit specific age-related metabolic changes in the brain, which occur regardless of disease duration or the frequency of attacks.

Methods

We analysed the relation between brain glucose (18F-fluorodeoxyglucose) uptake and age in healthy volunteers (n = 20) and episodic migraine patients (n = 19). In the latter, we additionally compared the correlation between 18F-fluorodeoxyglucose uptake and disease duration and monthly migraine days.

Results

In contrast to controls, in migraine patients advancing age was positively correlated to increased metabolism in the brainstem (especially the posterior pons), hippocampus, fusiform gyrus and parahippocampus. Conversely, no significant correlations between cerebral metabolism and disease duration or migraine days were observed.

Conclusions

Findings of this cross-sectional study show that episodic migraine patients exhibit specific metabolic brain modifications while ageing. As such, age is correlated with metabolic changes in key regions of the brain previously associated with migraine's pathophysiology to a better extent than disease duration or the number of monthly migraine days. More than the repeated headache attacks, the continuous interaction with the environment seemingly models the brain of migraine sufferers in an adaptive manner. A positive control (e.g. chronic pain) is missing in this study and therefore findings cannot be proven to be migraine-specific.

Divergent influences of the locus coeruleus on migraine pathophysiology

Migraine is a common disabling neurological condition that is associated with several premonitory symptoms that can occur days before the headache onset. The most commonly reported premonitory symptom is marked fatigue that has been shown to be highly predictive of an ensuing migraine attack. The locus coeruleus (LC) is a key nucleus involved in arousal that has also been shown to impact pain processing. It provides one of the major sources of noradrenaline to the dorsal horn of the spinal cord and neocortex. Given the clinical association between migraine, sleep-wake regulation, and fatigue, we sought to determine whether LC modulation could impact migraine-related phenotypes in several validated preclinical models of migraine. To determine its role in migraine-related pain, we recorded dural nociceptive-evoked responses of neurons in the trigeminocervical complex, which receives trigeminal primary afferents from the durovascular complex. In addition, we explored the susceptibility to cortical spreading depression initiation, the presumed underlying phenomenon of migraine aura. Our experiments reveal a potent role for LC disruption in the differential modulation of migraine-related phenotypes, inhibiting dural-evoked activation of wide dynamic neurons in the trigeminocervical complex while increasing cortical spreading depression susceptibility. This highlights the potential divergent impact of LC disruption in migraine physiology, which may help explain the complex interactions between dysfunctional arousal mechanisms and migraine.

Nitroglycerine triggers triptan-responsive cranial allodynia and trigeminal neuronal hypersensitivity

Cranial allodynia associated with spontaneous migraine is reported as either responsive to triptan treatment or to be predictive of lack of triptan efficacy. These conflicting results suggest that a single mechanism mediating the underlying neurophysiology of migraine symptoms is unlikely. The lack of a translational approach to study cranial allodynia reported in migraine patients is a limitation in dissecting potential mechanisms. Our objective was to study triptan-responsive cranial allodynia in migraine patients, and to develop an approach to studying its neural basis in the laboratory. Using nitroglycerine to trigger migraine attacks, we investigated whether cranial allodynia could be triggered experimentally, observing its response to treatment. Preclinically, we examined the cephalic response properties of central trigeminocervical neurons using extracellular recording techniques, determining changes to ongoing firing and somatosensory cranial-evoked sensitivity, in response to nitroglycerine followed by triptan treatment. Cranial allodynia was triggered alongside migraine-like headache in nearly half of subjects. Those who reported cranial allodynia accompanying their spontaneous migraine attacks were significantly more likely to have symptoms triggered than those that did not. Patients responded to treatment with aspirin or sumatriptan. Preclinically, nitroglycerine caused an increase in ongoing firing and hypersensitivity to intracranial-dural and extracranial-cutaneous (noxious and innocuous) somatosensory stimulation, reflecting signatures of central sensitization potentially mediating throbbing headache and cranial allodynia. These responses were aborted by a triptan. These data suggest that nitroglycerine can be used as an effective and reliable method to trigger cranial allodynia in subjects during evoked migraine, and the symptom is responsive to abortive triptan treatments. Preclinically, nitroglycerine activates the underlying neural mechanism of cephalic migraine symptoms, central sensitization, also predicting the clinical outcome to triptans. This supports a biological rationale that several mechanisms can mediate the underlying neurophysiology of migraine symptoms, with nitrergic-induced changes reflecting one that is relevant to spontaneous migraine in many migraineurs, whose symptoms of cranial allodynia are responsive to triptan treatment. This approach translates directly to responses in animals and is therefore a relevant platform to study migraine pathophysiology, and for use in migraine drug discovery.

Emerging drugs for migraine treatment: an update

Introduction: Migraine is a very frequent and disabling neurological disorder. The current treatment options are old, generally poorly tolerated and not migraine-specific, reflecting the low priority of migraine research and highlighting the vast unmet need in its management. Areas covered: Advancement in the understanding of migraine pathophysiological mechanisms and identification of novel potentially meaningful targets have resulted in a multitude of emerging acute and preventive treatments. Here we review the known putative migraine pathophysiological mechanisms in order to understand the rationale of the most promising novel treatments targeting the Calcitonin-Gene-Related Peptide receptor and ligand and the 5 hydroxytryptamine (5-HT)1F receptor. Key findings on the phase II and phase III clinical trials on these treatments will be summarized. Furthermore, a critical analysis on failed trials of potentially meaningful targets such the nitric oxide and the orexinergic pathways will be conducted. Future perspective will be outlined. Expert opinion: The recent approval of Erenumab and Fremanezumab is a major milestone in the therapy of migraine since the approval of triptans. Several more studies are needed to fully understand the clinical potential, long-term safety and cost-effectiveness of these therapies. This paramount achievement should stimulate the development of further research in the migraine field.

To what extent are patients with migraine able to predict attacks?

Purpose

Premonitory symptoms (PSs) of migraine are those that precede pain in a migraine attack. Previous studies suggest that treatment during this phase may prevent the onset of pain; however, this approach requires that patients be able to recognize their PSs. Our objectives were to evaluate patients’ actual ability to predict migraine attacks based on their PSs and analyze whether good predictors meet any characteristic profile.

Patients and methods

This prospective, observational study included patients with migraine with and without aura. Patients’ baseline characteristics were recorded. During a 2-month follow-up period, patients used a mobile application to record what they believed to be PSs and later to record the onset of pain, if this occurred. When a migraine attack ended, patients had to complete a form on the characteristics of the episode (including the presence of PSs not identified prior to the attack).

Results

Fifty patients were initially selected. A final total of 34 patients were analyzed, recording 229 attacks. Of whom, 158 (69%) were accompanied by PSs and were recorded prior to the pain onset in 63 (27.5%) cases. A total of 67.6% of the patients were able to predict at least one attack, but only 35.3% were good predictors (>50% of attacks). There were only 11 cases in which a patient erroneously reported their PSs (positive predictive value: 85.1%). Good predictors were not differentiated by any specific clinical characteristic. However, a range of symptoms were particularly predictive; these included photophobia, drowsiness, yawning, increased thirst, and blurred vision.

Conclusion

A large majority of patients with migraine experienced a PS and were able to predict at least one attack. Besides, only a small percentage of patients were considered as good predictors; however, they could not be characterized by any specific profile. Nonetheless, when patients with migraine believed that they were experiencing PSs, they were frequently correct.

Fremanezumab for preventive treatment of migraine: Functional status on headache-free days

Objective

To evaluate the effect of fremanezumab on the functional status on headache-free days in phase 2 episodic migraine (EM) and chronic migraine (CM) studies.

Methods

Functional status data were collected prospectively via the electronic headache diary on all headache-free days by patients answering questions regarding work/school/household chore performance, speed of work completion, concentration, and feeling of fatigue. Individuals with EM receiving monthly doses of fremanezumab 225 mg (n = 96) or 675 mg (n = 97) or placebo (n = 104) were compared. Individuals with CM receiving fremanezumab 675 mg followed by monthly 225 mg (n = 88) and 900 mg (n = 86) were also independently compared to those receiving placebo (n = 89).

Results

In patients with EM, compared to patients receiving placebo, those receiving fremanezumab experienced an increased number of headache-free days with normal function in work/school/household chore performance and concentration/mental fatigue measures compared to their baseline over the entire treatment period (all p < 0.005). An increased number of headache-free days with normal functional performance for some measures was also found in the CM group in those treated with fremanezumab.

Conclusion

There was an increased number of headache-free days with normal functional performance on all measures for the patients with EM and some measures for patients with CM in the fremanezumab-treated groups. Further research is required to confirm these findings in a prospective study and to clarify the underlying mechanism(s).

ClinicalTrials.gov identifier:

NCT02025556 and NCT02021773.

Classification of evidence

This study provides Class II evidence that for patients with migraine, fremanezumab increases normal functional performance on headache-free days.

The Migraine Postdrome

PURPOSE OF REVIEW

The migraine postdrome is the least studied and least understood phase of migraine. This article covers the salient features of the migraine postdrome and provides insight into the history, clinical symptoms, and future implications of this phase of migraine.

RECENT FINDINGS

Prospective electronic diary studies have shown that patients are left disabled with various nonheadache symptoms in the migraine postdrome, and 81% of patients report at least one nonheadache symptom in the postdrome. Hence, it is important to understand this phase better and ensure that more effective treatments become available in the future to lessen the morbidity associated with this phase. Functional imaging shows widespread reduction in brain-blood flow in the postdrome, which explains the multitudes of symptoms experienced by patients.

SUMMARY

The disability related to migraine is not exclusive to the headache phase but extends into the postdrome phase and is associated with several nonheadache symptoms that prolong the symptoms experienced by patients with migraine. Further research into the postdrome is crucial to improve our overall understanding of migraine mechanisms. This knowledge may also help to treat the concurrent nonheadache symptoms better in the future. Novel neuroimaging techniques provide a valuable noninvasive tool to push the frontiers in the understanding of migraine pathophysiology. These methods may help shed further light onto the possible links between key brain structures and networks that could be implicated in the pathophysiology of the various migraine phases.

Advances in migraine neuroimaging and clinical utility: from the MRI to the bedside

INTRODUCTION

In current migraine clinical practice, no specific diagnostic investigations are available and therefore the diagnosis is an eminently clinical process where instrumental examinations may have a part to exclude possible causes of secondary headaches. While migraine clinical phenotype has been widely characterized, migraine pathophysiology has still a gap that might be partly bridged by structural and functional neuroimaging investigations. Areas covered: This article aims to review the recent advances in functional neuroimaging, the consequent progress in the knowledge of migraine pathophysiology and their putative application and impact in the clinical setting. A comprehensive review was conducted of PubMed citations by entering the key word 'MRI' combined with 'migraine' AND/OR 'headache.' Other key words included 'gray matter' OR 'white matter,' 'structural' OR 'functional.' The only restriction was English-language publication. The abstracts of all articles meeting these criteria were reviewed, and full texts were examined for relevant references. Expert commentary: Advanced magnetic resonance imaging (MRI) techniques are tremendously improving our knowledge about brain abnormalities in migraine patients. However, advanced MRI could nowadays overcome the limits linked to the clinicians' judgment through the identification of objectively measurable neuroimaging findings (quantitative biomarkers) concerning the diagnosis, the prognosis and 'tailored' therapeutic-care pathways.

Transport of the pituitary adenylate cyclase-activating polypeptide across the blood-brain barrier: implications for migraine

Background

Pituitary adenylate cyclase-activating polypeptide (PACAP) is widely distributed in the nervous system and is involved in migraine pathophysiology. Understanding the function of the blood-brain barrier (BBB) in relation to PACAP is important to the understand the mechanisms behind PACAP-induced migraine attacks, but also to develop antimigraine drugs targeting the PACAP receptors Here, we aim to review the transport ability of PACAP across the BBB.

Methods

We performed a systematic literature search on PubMed to identify studies reporting original data on PACAP and BBB. The search was finalized in July 2017.

Results

The literature search identified 96 papers of which 11 contained relevant data. In addition, two papers were known to be relevant and were included. A total of 13 papers studies were included in the final analysis. Preclinical studies (n = 10) suggest the existence of specific PACAP transport systems across the BBB, while human PACAP studies failed to show vasodilator effect of PACAP on the cerebral arteries from the lumen (n = 3).

Conclusion

PACAP38 is transported over the BBB actively, while PACAP27 cross the BBB by diffusion over the membrane, but after crossing the endothelial membrane both isoforms are either rapidly degraded or efflux back from brain to blood. Thus, a direct central action of the PACAPs is unlikely. This is supported by studies showing selective PACAP effect on extra-cerebral arteries.

Targeted Orexin and Hypothalamic Neuropeptides for Migraine

The hypothalamus is involved in the regulation of homeostatic mechanisms and migraine-related trigeminal nociception and as such has been hypothesized to play a central role in the migraine syndrome from the earliest stages of the attack. The hypothalamus hosts many key neuropeptide systems that have been postulated to play a role in this pathophysiology. Such neuropeptides include but are not exclusive too orexins, oxytocin, neuropeptide Y, and pituitary adenylate cyclase activating protein, which will be the focus of this review. Each of these peptides has its own unique physiological role and as such many preclinical studies have been conducted targeting these peptide systems with evidence supporting their role in migraine pathophysiology. Preclinical studies have also begun to explore potential therapeutic compounds targeting these systems with some success in all cases. Clinical efficacy of dual orexin receptor antagonists and intranasal oxytocin have been tested; however, both have yet to demonstrate clinical effect. Despite this, there were limitations in these cases and strong arguments can be made for the further development of intranasal oxytocin for migraine prophylaxis. Regarding neuropeptide Y, work has yet to begun in a clinical setting, and clinical trials for pituitary adenylate cyclase activating protein are just beginning to be established with much optimism. Regardless, it is becoming increasingly clear the prominent role that the hypothalamus and its peptide systems have in migraine pathophysiology. Much work is required to better understand this system and the early stages of the attack to develop more targeted and effective therapies aimed at reducing attack susceptibility with the potential to prevent the attack all together.

Targeted CGRP Small Molecule Antagonists for Acute Migraine Therapy

Migraine is a highly prevalent, severe, and disabling neurological condition with a significant unmet need for effective acute therapies. Patients (~50%) are dissatisfied with their currently available therapies. Calcitonin gene-related peptide (CGRP) has emerged as a key neuropeptide involved in the pathophysiology of migraines. As reviewed in this manuscript, a number of small molecule antagonists of the CGRP receptor have been developed for migraine therapy. Incredibly, the majority of the clinical trials conducted have proven positive, demonstrating the importance of this signalling pathway in migraine. Unfortunately, a number of these molecules raised liver toxicity concerns when used daily for as little as 7 days resulting in their discontinuation. Despite the clear safety concerns, clinical trial data suggests that their intermittent use remains a viable and safe alternative, with 2 molecules remaining in clinical development (ubrogepant and rimegepant). Further, these proofs of principle studies identifying CGRP as a viable clinical target have led to the development of several CGRP or CGRP receptor-targeted monoclonal antibodies that continue to show good clinical efficacy.

Targeted Acid-Sensing Ion Channel Therapies for Migraine

Acid-sensing ion channels (ASICs) are a family of ion channels, consisting of four members; ASIC1 to 4. These channels are sensitive to changes in pH and are expressed throughout the central and peripheral nervous systems-including brain, spinal cord, and sensory ganglia. They have been implicated in a number of neurological conditions such as stroke and cerebral ischemia, traumatic brain injury, and epilepsy, and more recently in migraine. Their expression within areas of interest in the brain in migraine, such as the hypothalamus and PAG, their demonstrated involvement in preclinical models of meningeal afferent signaling, and their role in cortical spreading depression (the electrophysiological correlate of migraine aura), has enhanced research interest into these channels as potential therapeutic targets in migraine. Migraine is a disorder with a paucity of both acute and preventive therapies available, in which at best 50% of patients respond to available medications, and these medications often have intolerable side effects. There is therefore a great need for therapeutic development for this disabling condition. This review will summarize the understanding of the structure and CNS expression of ASICs, the mechanisms for their potential role in nociception, recent work in migraine, and areas for future research and drug development.

Migraine

Migraine is a chronic paroxysmal neurological disorder characterised by multiphase attacks of head pain and a myriad of neurological symptoms. The underlying genetic and biological underpinnings and neural networks involved are coming sharply into focus. This progress in the fundamental understanding of migraine has led to novel, mechanism-based and disease-specific therapeutics. In this Seminar, the clinical features and neurobiology of migraine are reviewed, evidence to support available treatment options is provided, and emerging drug, device, and biological therapies are discussed.

PACAP and migraine headache: immunomodulation of neural circuits in autonomic ganglia and brain parenchyma

The discovery that intravenous (IV) infusions of the neuropeptide PACAP-38 (pituitary adenylyl cyclase activating peptide-38) induced delayed migraine-like headaches in a large majority of migraine patients has resulted in considerable excitement in headache research. In addition to suggesting potential therapeutic targets for migraine, the finding provides an opportunity to better understand the pathological events from early events (aura) to the headache itself. Although PACAP-38 and the closely related peptide VIP (vasoactive intestinal peptide) are well-known as vasoactive molecules, the dilation of cranial blood vessels per se is no longer felt to underlie migraine headaches. Thus, more recent research has focused on other possible PACAP-mediated mechanisms, and has raised some important questions. For example, (1) are endogenous sources of PACAP (or VIP) involved in the triggering and/or propagation of migraine headaches?; (2) which receptor subtypes are involved in migraine pathophysiology?; (3) can we identify specific anatomical circuit(s) where PACAP signaling is involved in the features of migraine? The purpose of this review is to discuss the possibility, and supportive evidence, that PACAP acts to induce migraine-like symptoms not only by directly modulating nociceptive neural circuits, but also by indirectly regulating the production of inflammatory mediators. We focus here primarily on postulated extra-dural sites because potential mechanisms of PACAP action in the dura are discussed in detail elsewhere (see X, this edition).

A Systems Neuroscience Approach to Migraine

Migraine is an extremely common but poorly understood nervous system disorder. We conceptualize migraine as a disorder of sensory network gain and plasticity, and we propose that this framing makes it amenable to the tools of current systems neuroscience.

PACAP in hypothalamic regulation of sleep and circadian rhythm: importance for headache

The interaction between sleep and primary headaches has gained considerable interest due to their strong, bidirectional, clinical relationship. Several primary headaches demonstrate either a circadian/circannual rhythmicity in attack onset or are directly associated with sleep itself. Migraine and cluster headache both show distinct attack patterns and while the underlying mechanisms of this circadian variation in attack onset remain to be fully explored, recent evidence points to clear physiological, anatomical and genetic points of convergence. The hypothalamus has emerged as a key brain area in several headache disorders including migraine and cluster headache. It is involved in homeostatic regulation, including pain processing and sleep regulation, enabling appropriate physiological responses to diverse stimuli. It is also a key integrator of circadian entrainment to light, in part regulated by pituitary adenylate cyclase-activating peptide (PACAP). With its established role in experimental headache research the peptide has been extensively studied in relation to headache in both humans and animals, however, there are only few studies investigating its effect on sleep in humans. Given its prominent role in circadian entrainment, established in preclinical research, and the ability of exogenous PACAP to trigger attacks experimentally, further research is very much warranted. The current review will focus on the role of the hypothalamus in the regulation of sleep-wake and circadian rhythms and provide suggestions for the future direction of such research, with a particular focus on PACAP.

Biology of Neuropeptides: Orexinergic Involvement in Primary Headache Disorders

Migraine is a very common, severe disabling condition that can last for days and strike multiple times per month. Attacks, often characterized by severe unilateral throbbing pain that is exacerbated by activity, are commonly preceded by several diverse symptoms including fatigue, irritability, and yawning. This premonitory (prodromal) phase represents the earliest identifiable feature of an attack that is a reliable predictor of ensuing headache. The diversity of these symptoms underlines the complex nature of migraine and focuses considerable attention on the hypothalamus due to its prominent role in homeostatic regulation allowing state dependent behavioral modifications. While multiple neurotransmitter and neuropeptide systems have been proposed to play a role in migraine, the current review will focus on the emerging role of the hypothalamic orexinergic system in primary headache disorders. Specifically the potential role of altered orexinergic signalling in premonitory symptomatology and the future potential of targeted orexinergic therapies that could with other approaches act during the premonitory phase to prevent the occurrence of the headache or reduce an individual's susceptibility to attacks by altering the brain's response to external and internal triggers.

The role of the brainstem in migraine: Potential brainstem effects of CGRP and CGRP receptor activation in animal models

Background

Migraine is a severe debilitating disorder of the brain that is ranked as the sixth most disabling disorder globally, with respect to disability adjusted life years, and there remains a significant unmet demand for an improved understanding of its underlying mechanisms. In conjunction with perturbed sensory processing, migraine sufferers often present with diverse neurological manifestations (premonitory symptoms) that highlight potential brainstem involvement. Thus, as the field moves away from the view of migraine as a consequence of purely vasodilation to a greater understanding of migraine as a complex brain disorder, it is critical to consider the underlying physiology and pharmacology of key neural networks likely involved.

Discussion

The current review will therefore focus on the available evidence for the brainstem as a key regulator of migraine biology and associated symptoms. We will further discuss the potential role of CGRP in the brainstem and its modulation for migraine therapy, given the emergence of targeted CGRP small molecule and monoclonal antibody therapies.

Conclusion

The brainstem forms a functional unit with several hypothalamic nuclei that are capable of modulating diverse functions including migraine-relevant trigeminal pain processing, appetite and arousal regulatory networks. As such, the brainstem has emerged as a key regulator of migraine and is appropriately considered as a potential therapeutic target. While currently available CGRP targeted therapies have limited blood brain barrier penetrability, the expression of CGRP and its receptors in several key brainstem nuclei and the demonstration of brainstem effects of CGRP modulation highlight the significant potential for the development of CNS penetrant molecules.

Premonitory Symptoms of Migraine in Childhood and Adolescence

Purpose of Review

Premonitory symptoms in migraine; symptoms occurring before the onset of migraine pain or aura, are an increasingly recognised area of interest within headache research. It has been recently documented in the literature that these symptoms also occur in children and adolescents, with a comparable phenotype to adults. This review discusses the wide presentation of premonitory symptoms in migraine in children and adolescents, and the importance of understanding how these early symptoms are mediated in order to ensure that targeted abortive therapies are developed in the future. Recognition of these symptoms by parents, guardians, teachers and carers is of importance in ensuring early and effective attack treatment.

Recent Findings

A previous clinic-based questionnaire study in 103 children found a prevalence of premonitory symptoms in paediatric migraine of 67%, with a mean number of reported symptoms of two. A recent study found that in a clinic population of 100 children or adolescents with a migraine diagnosis who were preselected as having at least one premonitory symptom associated with their attacks, two or more premonitory symptoms were reported by 85% of patients. The most common symptoms were fatigue, mood change and neck stiffness.

Summary

Although the population prevalence of premonitory symptoms in migraine within the paediatric population, or their ability to predict accurately the onset of an impending headache cannot be deduced from the retrospective studies performed to date, premonitory symptoms occur in children as young as 18 months old. Understanding the biological basis of these, and their heterogeneous phenotype may help future targeted therapeutic research, helping the development of drugs that act before the onset of pain, limiting the morbidity associated with the migraine attack.

The migraine postdrome

PURPOSE OF REVIEW

Migraine is a common, disabling neurological disorder that affects up to 12% of the world population. Its pathophysiology is incompletely described. Of the various phases of migraine, the migraine postdrome is the least studied and hence the least understood.

RECENT FINDINGS

Electronic diary studies show patients are left disabled with non-headache symptoms in the migraine postdrome. Hence, the importance of understanding the phase better and ensuring that more effective treatments become available in the future to cut down the morbidity associated with this phase.

SUMMARY

The disability related to migraine is not limited to the headache phase and pans out to include the postdrome phase. The migraine postdrome needs to be studied more as this may improve our overall understanding of migraine mechanisms and also treat the concurrent symptoms better.

The premonitory phase: A crucial stage in migraine

INTRODUCTION

The premonitory phase comprises a wide range of symptoms that precede the onset of pain in a migraine episode by up to 48hours. Premonitory symptoms are often not recognised by patients but do have a significant impact on their quality of life. As these symptoms represent the first stage of a migraine attack, they are crucial in improving our understanding of the key points of the origin of migraine.

DEVELOPMENT

This paper uses a question-answer format to review the main clinical studies analysing premonitory symptoms, their predictive capacity, the relationship between these symptoms and the biology of migraine, and the role of neuroimaging in the premonitory phase. Finally, we discuss the relevance of these symptoms as potential therapeutic targets in the future.

CONCLUSIONS

This study of the premonitory phase has demonstrated that the hypothalamus plays an essential role in the origin of migraine attacks. We should consider the search for new targets in acute migraine treatment in order to act before the onset of the pain. This would imply a radical change in the lives of patients with migraine.

Brodmann area 10: Collating, integrating and high level processing of nociception and pain

Multiple frontal cortical brain regions have emerged as being important in pain processing, whether it be integrative, sensory, cognitive, or emotional. One such region, Brodmann Area 10 (BA 10), is the largest frontal brain region that has been shown to be involved in a wide variety of functions including risk and decision making, odor evaluation, reward and conflict, pain, and working memory. BA 10, also known as the anterior prefrontal cortex, frontopolar prefrontal cortex or rostral prefrontal cortex, is comprised of at least two cytoarchitectonic sub-regions, medial and lateral. To date, the explicit role of BA 10 in the processing of pain hasn't been fully elucidated. In this paper, we first review the anatomical pathways and functional connectivity of BA 10. Numerous functional imaging studies of experimental or clinical pain have also reported brain activations and/or deactivations in BA 10 in response to painful events. The evidence suggests that BA 10 may play a critical role in the collation, integration and high-level processing of nociception and pain, but also reveals possible functional distinctions between the subregions of BA 10 in this process.

PACAP38 in human models of primary headaches

Background

To review the role of PACAP38 in human models of primary headaches, discuss possible mechanisms of PACAP38-induced migraine, and outline future directions.

Discussion

Experimental studies have established PACAP38 as a potent pharmacological “trigger” molecule of migraine-like attacks. These studies have also revealed a heterogeneous PACAP38 migraine response in migraine without aura patients. In addition, findings from brain imaging studies have demonstrated neuronal and vascular changes in migraine patients both ictally and interictally after PACAP38 infusion.

Conclusion

Human migraine models have shed light on the importance of PACAP38 in the pathophysiology of primary headaches. These studies have also pointed to the PAC₁ receptor and the PACAP38 molecule itself as target sites for drug testing. Future research should seek to understand the mechanisms underlying PACAP38-induced migraine. The results from an ongoing proof of concept randomized clinical trial may reveal the therapeutic potential of anti-PAC₁ receptor antibodies for migraine prevention.

Daily vision testing can expose the prodromal phase of migraine

Background

Several visual tasks have been proposed as indirect assays of the balance between cortical inhibition and excitation in migraine. This study aimed to determine whether daily measurement of performance on such tasks can reveal perceptual changes in the build up to migraine events.

Methods

Visual performance was measured daily at home in 16 non-headache controls and 18 individuals with migraine using a testing protocol on a portable tablet device. Observers performed two tasks: luminance increment detection in spatial luminance noise and centre surround contrast suppression.

Results

Luminance thresholds were reduced in migraine compared to control groups ( p < 0.05), but thresholds did not alter across the migraine cycle; while headache-free, centre-surround contrast suppression was stronger for the migraine group relative to controls ( p < 0.05). Surround suppression weakened at around 48 hours prior to a migraine attack and strengthened to approach their headache-free levels by 24 hours post-migraine (main effect of timing, p < 0.05).

Conclusions

Daily portable testing of vision enabled insight into perceptual performance in the lead up to migraine events, a time point that is typically difficult to capture experimentally. Perceptual surround suppression of contrast fluctuates during the migraine cycle, supporting the utility of this measure as an indirect, non-invasive assay of the balance between cortical inhibition and excitation.

Physiopathology of Migraine: What Have We Learned from Functional Imaging?

PURPOSE OF REVIEW

This review aims to provide an overview of the most recent and significant functional neuroimaging studies which have clarified the complex mechanisms underlying migraine pathophysiology.

RECENT FINDINGS

The recent data allow us to overcome the concept of a migraine generator suggesting that functional networks abnormalities may lead to changes in different brain area activities and consequent reduced migraine thresholds susceptibility, likely associated with higher migraine severity and burden. Although functional magnetic resonance imaging studies have allowed recognition of several migraine mechanisms, its pathophysiology is not completely understood and is still a matter of research. Nevertheless, in recent years, functional magnetic resonance imaging studies have allowed us to implement our knowledge of migraine pathophysiology. The pivotal role of both the brainstem and the hippocampus in the first phase of a migraine attack, the involvement of limbic pathway in the constitution of a migrainous pain network, the disrupted functional connectivity in cognitive brain networks, as well as the abnormal function of the visual network in patients with migraine with aura are the main milestones in migraine imaging achieved through functional imaging advances. We believe that further studies based on combined functional and structural techniques and the investigation of the different phases of migraine cycle may represent an efficient methodological approach for comprehensively looking into the migrainous brain secrets.

Recognizing the role of CGRP and CGRP receptors in migraine and its treatment

Premise

The brain and the sensory nervous system contain a rich supply of calcitonin gene-related peptide (CGRP) and CGRP receptor components. Clinical studies have demonstrated a correlation between CGRP release and acute migraine headache that led to the development of CGRP-specific drugs that either abort acute attacks of migraine (gepants) or are effective as prophylaxis (antibodies). However, there is still much discussion concerning the site of action of these drugs.

Problem

Here we describe the most recent data related to CGRP in the trigeminal ganglion and its connections to the CNS, putative key regions involved in migraine pathophysiology. Gepants are small molecules that have limited ability to cross the blood-brain barrier (BBB), whereas CGRP antibodies are 1500 times larger molecules, and are virtually excluded from the brain, with a BBB permeability of < 0.1%. Thus we propose that the primary site of action for the antimigraine drugs is outside the CNS in areas not limited by the BBB.

Potential solution

Therefore, it is reasonable to discuss the localization of CGRP and its receptor components in relation to the BBB. The trigeminovascular system, located outside the BBB, has a key role in migraine symptomatology, and it is likely targeted by the novel CGRP drugs that successfully terminate migraine headache.

Human models of migraine - short-term pain for long-term gain

Migraine is a complex disorder characterized by recurrent episodes of headache, and is one of the most prevalent and disabling neurological disorders. A key feature of migraine is that various factors can trigger an attack, and this phenomenon provides a unique opportunity to investigate disease mechanisms by experimentally inducing migraine attacks. In this Review, we summarize the existing experimental models of migraine in humans, including those that exploit nitric oxide, histamine, neuropeptide and prostaglandin signalling. We describe the development and use of these models in the discovery of molecular pathways that are responsible for initiation of migraine attacks. Combining experimental human models with advanced imaging techniques might help to identify biomarkers of migraine, and in the ongoing search for new and better migraine treatments, human models will have a key role in the discovery of future targets for more-specific and more-effective mechanism-based antimigraine drugs.

Exploring resting-state EEG complexity before migraine attacks

Objective

Entropy-based approaches to understanding the temporal dynamics of complexity have revealed novel insights into various brain activities. Herein, electroencephalogram complexity before migraine attacks was examined using an inherent fuzzy entropy approach, allowing the development of an electroencephalogram-based classification model to recognize the difference between interictal and preictal phases.

Methods

Forty patients with migraine without aura and 40 age-matched normal control subjects were recruited, and the resting-state electroencephalogram signals of their prefrontal and occipital areas were prospectively collected. The migraine phases were defined based on the headache diary, and the preictal phase was defined as within 72 hours before a migraine attack.

Results

The electroencephalogram complexity of patients in the preictal phase, which resembled that of normal control subjects, was significantly higher than that of patients in the interictal phase in the prefrontal area (FDR-adjusted p < 0.05) but not in the occipital area. The measurement of test-retest reliability (n = 8) using the intra-class correlation coefficient was good with r1 = 0.73 ( p = 0.01). Furthermore, the classification model, support vector machine, showed the highest accuracy (76 ± 4%) for classifying interictal and preictal phases using the prefrontal electroencephalogram complexity.

Conclusion

Entropy-based analytical methods identified enhancement or “normalization” of frontal electroencephalogram complexity during the preictal phase compared with the interictal phase. This classification model, using this complexity feature, may have the potential to provide a preictal alert to migraine without aura patients.

Clinical characteristics of menstrually related and non-menstrual migraine

Migraine attacks increase during the perimenstrual period in approximately half of female migraineurs. There are differences in the pathogenesis and clinical features of menstrually related and non-menstrual migraine attacks. The objective of this study was to compare the characteristics of migraine in patients with menstrually related and non-menstrual migraine, and to investigate the differences between premenstrual, menstrual, and late-menstrual migraine attacks. Three-hundred and thirty-two women with migraine without aura were evaluated using questionnaires and diaries to determine the characteristics of headache, preceding and accompanying symptoms, and the relation of migraine attacks and menstruation. One-hundred and sixty-three women had menstrually related migraine without aura (49.1%). Duration of disease and duration of headache were longer (p = 0.002 and p < 0.001, respectively), and nausea, vomiting, phonophobia, and aggravation of headache with physical activity were more frequent in patients with menstrually related migraine (p = 0.005, p = 0.006, p < 0.001 and p = 0.006, respectively). Premonitory symptoms and allodynia were observed more frequently in the menstrually related migraine group (p = 0.012 and p = 0.004, respectively). Perimenstrual migraine attacks occurred premenstrually (days -2 and -1) in 46 patients (25.3%), menstrually (days 1 to 3) in 90 patients (49.4%), and late menstrually (days 4 to 7) in 19 patients (10.4%). Our results showed that the duration of headache was longer and accompanying symptoms were more frequent and diverse in patients with menstrually related migraine without aura, suggesting that these findings may reflect the increase in excitability or susceptibility of the brain in these patients.

An update on migraine: current understanding and future directions

Migraine is a common brain disorder with high disability rates which involves a series of abnormal neuronal networks, interacting at different levels of the central and peripheral nervous system. An increase in the interest around migraine pathophysiology has allowed researchers to unravel certain neurophysiological mechanisms and neurotransmitter involvement culminating in the recent development of novel therapies, which might substantially change the clinical approach to migraine patients. The present review will highlight the current aspects of migraine pathophysiology, covering an understanding of the complex workings of the migraine state and the brain regions responsible for them. We will further discuss the therapeutic agents which have appeared in the most recent years for migraine care, from calcitonin gene-related peptide (CGRP) receptor antagonists, gepants; through serotonin 5-HT1F receptor agonists, ditans, and CGRP or CGRP receptor monoclonal antibodies to invasive and non-invasive neuromodulation techniques.

Distribution of CGRP and CGRP receptor components in the rat brain

BACKGROUND

Calcitonin gene-related peptide and its receptor, consisting of receptor activity-modifying protein 1 and calcitonin receptor-like receptor, are of considerable interest because of the role they play in migraine and recently developed migraine therapies.

METHODS

To better understand the function of this neuropeptide, we used immunohistochemistry to determine a detailed distribution of calcitonin gene-related peptide, receptor activity-modifying protein 1 and calcitonin receptor-like receptor in the rat brain in a region of 0.5-1.5 mm lateral to the midline. We found calcitonin gene-related peptide immunoreactivity in most of the neurons of the cerebral cortex, hippocampus, cerebellum, thalamic nuclei, hypothalamic nuclei and brainstem nuclei. In contrast, receptor activity-modifying protein 1 and calcitonin receptor-like receptor immunoreactivity were found almost exclusively in the neuronal processes in the investigated regions.

CONCLUSION

Overall, the degree of expression of calcitonin gene-related peptide and calcitonin gene-related peptide receptor components in the central nervous system is astonishingly complex and suggestive of many different brain functions, including a possible role in migraine. However, currently, the presence of calcitonin gene-related peptide and the nature of its receptors throughout the brain is an enigma yet to be solved.

Clinical description of attack-related cognitive symptoms in migraine: A systematic review

Introduction

Cognitive symptoms have been described during migraine attacks since the Roman era; while being neglected throughout the centuries, they are relevant contributors to migraine-related disability.

Objective

To determine whether cognitive symptoms are included in clinical series describing migraine attack phenomenology, and which symptoms occur in each attack phase.

Method

Systematic review of existing data on clinical descriptions of migraine attacks, focusing on cognitive symptomatology. Data were organized and analyzed qualitatively, due to methodological differences between studies.

Results

Twenty-four articles were reviewed, with a total sample of 7007 patients, including 82.9% females with an average age of 39.2 years. Twenty one (75%) studies analyzed one phase of the attack (eight prodromes, five auras, one between aura and pain, three headaches and three postdromes), the remaining studied more than one phase. Cognitive complaints were the most frequent symptom of the prodromic (30%) and headache (38%) phases, while fatigue (70%) dominated the resolution phase. Not enough data is available to estimate the frequency of cognitive symptoms during the aura.

Discussion

Cognitive symptoms are described in all phases of the migraine attack phenomenology in published clinical series of migraine. Their characteristics appear to be different in each attack phase, although methodological limitations prevent generalization of this finding.

Cerebral metabolism before and after external trigeminal nerve stimulation in episodic migraine

Background and aim A recent sham-controlled trial showed that external trigeminal nerve stimulation (eTNS) is effective in episodic migraine (MO) prevention. However, its mechanism of action remains unknown. We performed 18-fluorodeoxyglucose positron emission tomography (FDG-PET) to evaluate brain metabolic changes before and after eTNS in episodic migraineurs. Methods Twenty-eight individuals were recruited: 14 with MO and 20 healthy volunteers (HVs). HVs underwent a single FDG-PET, whereas patients were scanned at baseline, directly after a first prolonged session of eTNS (Cefaly®) and after three months of treatment (uncontrolled study). Results The frequency of migraine attacks significantly decreased in compliant patients ( N = 10). Baseline FDG-PET revealed a significant hypometabolism in fronto-temporal areas, especially in the orbitofrontal (OFC) and rostral anterior cingulate cortices (rACC) in MO patients. This hypometabolism was reduced after three months of eTNS treatment. Conclusion Our study shows that metabolic activity of OFC and rACC, which are pivotal areas in central pain and behaviour control, is decreased in migraine. This hypometabolism is reduced after three months of eTNS. eTNS might thus exert its beneficial effects via slow neuromodulation of central pain-controlling areas, a mechanism also previously reported in chronic migraine and cluster headache after percutaneous occipital nerve stimulation. However, this finding needs to be confirmed by further studies using a sham condition.

Migraine Subclassification via a Data-Driven Automated Approach Using Multimodality Factor Mixture Modeling of Brain Structure Measurements

BACKGROUND

The current subclassification of migraine is according to headache frequency and aura status. The variability in migraine symptoms, disease course, and response to treatment suggest the presence of additional heterogeneity or subclasses within migraine.

OBJECTIVE

The study objective was to subclassify migraine via a data-driven approach, identifying latent factors by jointly exploiting multiple sets of brain structural features obtained via magnetic resonance imaging (MRI).

METHODS

Migraineurs (n = 66) and healthy controls (n = 54) had brain MRI measurements of cortical thickness, cortical surface area, and volumes for 68 regions. A multimodality factor mixture model was used to subclassify MRIs and to determine the brain structural factors that most contributed to the subclassification. Clinical characteristics of subjects in each subgroup were compared.

RESULTS

Automated MRI classification divided the subjects into two subgroups. Migraineurs in subgroup #1 had more severe allodynia symptoms during migraines (6.1 ± 5.3 vs. 3.6 ± 3.2, P = .03), more years with migraine (19.2 ± 11.3 years vs 13 ± 8.3 years, P = .01), and higher Migraine Disability Assessment (MIDAS) scores (25 ± 22.9 vs 15.7 ± 12.2, P = .04). There were not differences in headache frequency or migraine aura status between the two subgroups.

CONCLUSIONS

Data-driven subclassification of brain MRIs based upon structural measurements identified two subgroups. Amongst migraineurs, the subgroups differed in allodynia symptom severity, years with migraine, and migraine-related disability. Since allodynia is associated with this imaging-based subclassification of migraine and prior publications suggest that allodynia impacts migraine treatment response and disease prognosis, future migraine diagnostic criteria could consider allodynia when defining migraine subgroups.

An Arterial Spin Labeling MRI Perfusion Study of Migraine without Aura Attacks

Background

Studies of brain perfusion during migraine without aura attacks have inconsistent results.

Methods

Arterial spin labeling MRI, a non-invasive quantitative perfusion technique, was used to prospectively study a spontaneous untreated migraine without aura attack and a headache-free period. Image analysis used FSL and MATLAB software; Group analysis used permutation methods for perfusion differences between sessions.

Results

Thirteen women (age 35.7) were scanned during an attack of an average intensity of 6.8 (on 0–10 Visual Analog Scale) and 16 h duration. No global or regional perfusion differences were identified when comparing migraine and migraine-free sessions.

Discussion

Our findings suggest that the painful phase of migraine without aura attacks is not associated with brain perfusion abnormalities.