Increased brainstem perfusion, but no blood-brain barrier disruption, during attacks of migraine with aura

Gadolinium-based contrast agents aggravate mechanical and thermal hyperalgesia in a nitroglycerine-induced migraine model in male mice

In the diagnosis of migraine, which is a neurovascular disease, gadolinium-based contrast agents (GBCAs) are used to rule out more serious conditions. On the other hand, it remains unclear as a scientific gap whether GBCAs may trigger migraine-related pain. The aim of this study was to investigate the effect of GBCAs on mechanical and thermal pain behaviour in a nitroglycerin (NTG)-induced migraine model in mice. NTG (10 mg/kg) was administered intraperitoneally to adult (6-8weeks old) BALB/c mice 2 h before behavioral tests 5 times every other day on days 1st, 3rd, 5th and 9th to induce migraine model (N = 50). As GBCAs, gadobenate dimeglumine (linear-ionic), Gadodiamide (linear-nonionic), and gadobutrol (macrocyclic-nonionic) were delivered intravenously through the tail vein of mice for 5 days on test days. Mechanical pain threshold (plantar and facial withdrawal threshold) was evaluated by plantar von Frey and periorbital von Frey tests on days 1st, 5th, and 9th, and thermal pain threshold (latency) was evaluated by hot plate and cold plate tests on days 3rd and 7th. There was a statistically significant increase in mechanical and thermal hyperalgesia in NTG administered groups compared to the control group. Gadodiamide, gadobutrol and gadobenate dimeglumine administration significantly decreased latency, paw and facial withdrawal threshold (0.18 ± 0.05, 0.17 ± 0.07, 0.16 ± 0.09; 9th day values respectively) compared to NTG group (0.27 ± 0.05). The results of this in vivo study show that GBCAs produce effects that may trigger migraine attacks in migraine. It is recommended that these effects be further investigated and supported by further clinical studies.

Impaired Glymphatic and Meningeal Lymphatic Functions in Patients with Chronic Migraine

OBJECTIVE

This study was undertaken to investigate migraine glymphatic and meningeal lymphatic vessel (mLV) functions.

METHODS

Migraine patients and healthy controls (HCs) were prospectively recruited between 2020 and 2023. Diffusion tensor image analysis along the perivascular space (DTI-ALPS) index for glymphatics and dynamic contrast-enhanced magnetic resonance imaging parameters (time to peak [TTP]/enhancement integral [EI]/mean time to enhance [MTE]) for para-superior sagittal (paraSSS)-mLV or paratransverse sinus (paraTS)-mLV in episodic migraine (EM), chronic migraine (CM), and CM with and without medication-overuse headache (MOH) were analyzed. DTI-ALPS correlations with clinical parameters (migraine severity [numeric rating scale]/disability [Migraine Disability Assessment (MIDAS)]/bodily pain [Widespread Pain Index]/sleep quality [Pittsburgh Sleep Quality Index (PSQI)]) were examined.

RESULTS

In total, 175 subjects (112 migraine + 63 HCs) were investigated. DTI-ALPS values were lower in CM (median [interquartile range] = 0.64 [0.12]) than in EM (0.71 [0.13], p = 0.005) and HCs (0.71 [0.09], p = 0.004). CM with MOH (0.63 [0.07]) had lower DTI-ALPS values than CM without MOH (0.73 [0.12], p < 0.001). Furthermore, CM had longer TTP (paraSSS-mLV: 55.8 [12.9] vs 40.0 [7.6], p < 0.001; paraTS-mLV: 51.2 [8.1] vs 44.0 [3.3], p = 0.002), EI (paraSSS-mLV: 45.5 [42.0] vs 16.1 [9.2], p < 0.001), and MTE (paraSSS-mLV: 253.7 [6.7] vs 248.4 [13.8], p < 0.001; paraTS-mLV: 252.0 [6.2] vs 249.7 [1.2], p < 0.001) than EM patients. The MIDAS (p = 0.002) and PSQI (p = 0.002) were negatively correlated with DTI-ALPS index after Bonferroni corrections (p < q = 0.01).

INTERPRETATION

CM patients, particularly those with MOH, have glymphatic and meningeal lymphatic dysfunctions, which are highly clinically relevant and may implicate pathogenesis for migraine chronification. ANN NEUROL 2024;95:583-595.

Vulnerability of the Hippocampus to Insults: Links to Blood-Brain Barrier Dysfunction

The hippocampus is a critical brain substrate for learning and memory; events that harm the hippocampus can seriously impair mental and behavioral functioning. Hippocampal pathophysiologies have been identified as potential causes and effects of a remarkably diverse array of medical diseases, psychological disorders, and environmental sources of damage. It may be that the hippocampus is more vulnerable than other brain areas to insults that are related to these conditions. One purpose of this review is to assess the vulnerability of the hippocampus to the most prevalent types of insults in multiple biomedical domains (i.e., neuroactive pathogens, neurotoxins, neurological conditions, trauma, aging, neurodegenerative disease, acquired brain injury, mental health conditions, endocrine disorders, developmental disabilities, nutrition) and to evaluate whether these insults affect the hippocampus first and more prominently compared to other brain loci. A second purpose is to consider the role of hippocampal blood-brain barrier (BBB) breakdown in either causing or worsening the harmful effects of each insult. Recent research suggests that the hippocampal BBB is more fragile compared to other brain areas and may also be more prone to the disruption of the transport mechanisms that act to maintain the internal milieu. Moreover, a compromised BBB could be a factor that is common to many different types of insults. Our analysis indicates that the hippocampus is more vulnerable to insults compared to other parts of the brain, and that developing interventions that protect the hippocampal BBB may help to prevent or ameliorate the harmful effects of many insults on memory and cognition.

Effect of anti-CGRP-targeted therapy on migraine aura: Results of an observational case series study

INTRODUCTION

Limited clinical evidence is available regarding the potential effectiveness of anti-CGRP monoclonal antibodies for the preventive treatment of migraine with aura.

AIM OF THE STUDY

This observational study involved a series of migraine patients affected by either migraine with or without aura, who were investigated for any changes in their frequencies and their migraine aura attack characteristics observed during treatment with anti-CGRP Mabs over a 1-year period.

PATIENTS AND METHODS

Twelve migraine patients were included, seven of whom were treated with erenumab, 2 with fremanezumab, and 3 with galcanezumab. Clinical data were collected at baseline, which were defined as 3 months prior to the initiation of treatment, and thereafter at each trimester, over the 1-year treatment period. The parameters included the number of headache and migraine days/month, the frequency of aura episodes, the number of days with acute drug intakes/month, and the scores from the migraine disability status scale (MIDAS), and the Headache Impact Test 6 (HIT-6).

RESULTS

Anti-CGRP Mbs antibodies induced significant decreases in mean headache and migraine without aura days per month, the number of days with medication intake, as well as MIDAS and HIT-6 scores (p < 0.0001). In contrast, the anti-CGRP Mab treatment did not appear to impact the frequency of migraine with aura attacks but seemed to reduce both the intensity and the duration of headache phases of migraine aura. Furthermore, some migraine patients referred to having aura attacks without headache over the course of the treatment period.

CONCLUSIONS

Based on the above findings, we hypothesize that anti-CGRP Mabs did not influence neuronal and vascular events related to cortical spreading depression (CSD) which is considered the pathophysiological substrate of aura. Conversely, these antibodies are able to counteract, via their peripheral mechanisms of action, the sensitization of the trigemino-vascular pathway which is triggered by CSD. This aforementioned might explain why in our patients, migraine aura attacks remained unchanged in their frequencies, but the headache phases were either reduced or absent.

Cellular and Molecular Roles of Immune Cells in the Gut-Brain Axis in Migraine

Migraine is a complex and multi-system dysfunction. The realization of its pathophysiology and diagnosis is developing rapidly. Migraine has been linked to gastrointestinal disorders such as irritable bowel syndrome and celiac disease. There is also direct and indirect evidence for a relationship between migraine and the gut-brain axis, but the exact mechanism is not yet explained. Studies have shown that this interaction appears to be influenced by a variety of factors, such as inflammatory mediators, gut microbiota, neuropeptides, and serotonin pathways. Recent studies suggest that immune cells can be the potential tertiary structure between migraine and gut-brain axis. As the hot interdisciplinary subject, the relationship between immunology and gastrointestinal tract is now gradually clear. Inflammatory signals are involved in cellular and molecular responses that link central and peripheral systems. The gastrointestinal symptoms associated with migraine and experiments associated with antibiotics have shown that the intestinal microbiota is abnormal during the attacks. In this review, we focus on the mechanism of migraine and gut-brain axis, and summarize the tertiary structure between immune cells, neural network, and gastrointestinal tract.

Targeting CGRP pathways and aura: A peripheral site with a central effect

Targeting CGRP-pathways has substantially expanded our options for treating individuals with migraine. Although the efficacy of these drugs on migraine aura is yet to be fully revealed, it seems from existing studies that CGRP antagonism reduces the number of migraine auras. The present perspective summarizes the evidence linking CGRP to the migraine aura and proposes a model by which targeting the CGRP-pathways and, thus, inhibition the interaction between C- and Aδ-trigeminal fibers might reverse a possible high cortical glutamate level leading to a reduced number of migraine auras.

Migraine Aura-Catch Me If You Can with EEG and MRI-A Narrative Review

Roughly one-third of migraine patients suffer from migraine with aura, characterized by transient focal neurological symptoms or signs such as visual disturbance, sensory abnormalities, speech problems, or paresis in association with the headache attack. Migraine with aura is associated with an increased risk for stroke, epilepsy, and with anxiety disorder. Diagnosis of migraine with aura sometimes requires exclusion of secondary causes if neurological deficits present for the first time or are atypical. It was the aim of this review to summarize EEG an MRI findings during migraine aura in the context of pathophysiological concepts. This is a narrative review based on a systematic literature search. During visual auras, EEG showed no consistent abnormalities related to aura, although transient focal slowing in occipital regions has been observed in quantitative studies. In contrast, in familial hemiplegic migraine (FHM) and migraine with brain stem aura, significant EEG abnormalities have been described consistently, including slowing over the affected hemisphere or bilaterally or suppression of EEG activity. Epileptiform potentials in FHM are most likely attributable to associated epilepsy. The initial perfusion change during migraine aura is probably a short lasting hyperperfusion. Subsequently, perfusion MRI has consistently demonstrated cerebral hypoperfusion usually not restricted to one vascular territory, sometimes associated with vasoconstriction of peripheral arteries, particularly in pediatric patients, and rebound hyperperfusion in later phases. An emerging potential MRI signature of migraine aura is the appearance of dilated veins in susceptibility-weighted imaging, which may point towards the cortical regions related to aura symptoms ("index vein"). Conclusions: Cortical spreading depression (CSD) cannot be directly visualized but there are probable consequences thereof that can be captured Non-invasive detection of CSD is probably very challenging in migraine. Future perspectives will be elaborated based on the studies summarized.

Altered resting-state effective connectivity of trigeminal vascular system in migraine without aura: A spectral dynamic causal modeling study

BACKGROUND

The trigeminal vascular system is an important part of the anatomical and physiological basis of migraine. The effective connectivity (EC) among the regions of interest (ROIs) in the trigeminal vascular system involved in migraine without aura (MWoA) remains unclear.

METHODS

In this cross-sectional study, 48 patients (mean [SD] age 38.06 [10.35] years; male, 14/48 [29%]) with MWoA during the interictal phase and 48 healthy controls of similar age and sex (mean [SD] age 38.96 [10.96] years; male, 14/48 [29%]) underwent resting-state functional magnetic resonance imaging (fMRI). Dynamic causal modeling analysis was conducted to investigate directional EC among ROIs in the trigeminal vascular system including the bilateral brainstem, the primary somatosensory cortex (S1), the thalamus, and the insula.

RESULTS

Compared with the healthy control group, MWoA represented significantly reduced EC from the left brainstem (Brainstem.L) to the left insula (MWoA: mean [SD] -0.16 [0.36]; healthy controls: mean [SD] 0.11 [0.41]; Pcorrected  = 0.021), reduced EC from the Brainstem.L to the right insula (MWoA: mean [SD] -0.15 [0.39]; healthy controls: mean [SD] 0.03 [0.35]; Pcorrected  = 0.021), and decreased EC from the left thalamus (Thalamus.L) to the Brainstem.L (MWoA: mean [SD] -0.13 [0.56]; healthy controls: mean [SD] 0.10 [0.45]; Pcorrected  = 0.021). Altered EC parameters were not significantly correlated with MWoA clinical data.

CONCLUSION

These results further provide increasing evidence that disturbed homeostasis of the trigeminovascular nociceptive pathway is involved in the pathophysiological mechanisms of migraine. Patients with MWoA exhibited a regional interaction distinct from healthy controls in the neural pathway of the Bilateral Insula-Brainstem.L-Thalamus.L, which may shed light on the future understanding of brain mechanisms for MWoA. Future brain-based interventions are suggested to consider the dysregulation in the Bilateral Insula-Brainstem.L-Thalamus.L circuits.

Neuroimaging in the pre-ictal or premonitory phase of migraine: a narrative review

BACKGROUND

The premonitory phase, or prodrome, of migraine, provides valuable opportunities to study attack initiation and for treating the attack before headache starts. Much that has been learned about this phase in recent times has come from the outcomes of functional imaging studies. This review will summarise these studies to date and use their results to provide some feasible insights into migraine neurobiology.

MAIN BODY

The ability to scan repeatedly a patient without radiation and with non-invasive imaging modalities, as well as the recognition that human experimental migraine provocation compounds, such as nitroglycerin (NTG) and pituitary adenylate cyclase activating polypeptide (PACAP), can trigger typical premonitory symptoms (PS) and migraine-like headache in patients with migraine, have allowed feasible and reproducible imaging of the premonitory phase using NTG. Some studies have used serial scanning of patients with migraine to image the migraine cycle, including the 'pre-ictal' phase, defined by timing to headache onset rather than symptom phenotype. Direct observation and functional neuroimaging of triggered PS have also revealed compatible neural substrates for PS in the absence of headache. Various imaging methods including resting state functional MRI (rsfMRI), arterial spin labelling (ASL), positron emission tomography (PET) and diffusion tensor imaging (DTI) have been used. The results of imaging the spontaneous and triggered premonitory phase have been largely consistent and support a theory of central migraine attack initiation involving brain areas such as the hypothalamus, midbrain and limbic system. Early dysfunctional pain, sensory, limbic and homeostatic processing via monoaminergic and peptidergic neurotransmission likely manifests in the heterogeneous PS phenotype.

CONCLUSION

Advances in human migraine research, including the use of functional imaging techniques lacking radiation or radio-isotope exposure, have led to an exciting opportunity to study the premonitory phase using repeated measures imaging designs. These studies have provided novel insights into attack initiation, migraine neurochemistry and therapeutic targets. Emerging migraine-specific therapies, such as those targeting calcitonin gene-related peptide (CGRP), are showing promise acutely when taken during premonitory phase to reduce symptoms and prevent subsequent headache. Therapeutic research in this area using PS for headache onset prediction and early treatment is likely to grow in the future.

Molecular Mechanisms of Migraine: Nitric Oxide Synthase and Neuropeptides

Migraine is a common condition with disabling attacks that burdens people in the prime of their working lives. Despite years of research into migraine pathophysiology and therapeutics, much remains to be learned about the mechanisms at play in this complex neurovascular condition. Additionally, there remains a relative paucity of specific and targeted therapies available. Many sufferers remain underserved by currently available broad action preventive strategies, which are also complicated by poor tolerance and adverse effects. The development of preclinical migraine models in the laboratory, and the advances in human experimental migraine provocation, have led to the identification of key molecules likely involved in the molecular circuity of migraine, and have provided novel therapeutic targets. Importantly, the identification that vasoconstriction is neither necessary nor required for headache abortion has changed the landscape of migraine treatment and has broadened the therapy targets for patients with vascular risk factors or vascular disease. These targets include nitric oxide synthase (NOS) and several neuropeptides that are involved in migraine. The ability of NO donors and infusion of some of these peptides into humans to trigger typical migraine-like attacks has supported the development of targeted therapies against these molecules. Some of these, such as those targeting calcitonin gene-related peptide (CGRP), have already reached clinical practice and are displaying a positive outcome in migraineurs for the better by offering targeted efficacy without significant adverse effects. Others, such as those targeting pituitary adenylate cyclase activating polypeptide (PACAP), are showing promise and are likely to enter phase 3 clinical trials in the near future. Understanding these nitrergic and peptidergic mechanisms in migraine and their interactions is likely to lead to further therapeutic strategies for migraine in the future.

Levcromakalim provokes an acute rapid-onset migraine-like phenotype without inducing cortical spreading depolarization

BACKGROUND

Migraine headache attacks and accompanying sensory augmentation can be induced by several agents including levcromakalim (LVC), that is also capable of provoking aura-like symptoms in migraineurs. We investigated whether single LVC injection causes acute migraine-like phenotype in rats and induces/modulates cortical spreading depolarization (CSD), a rodent model of migraine aura.

METHODS

Wistar rats were administered LVC (1 mg/kg, i.p.) and compared to control (CTRL, vehicle, i.p.) and nitroglycerin (NTG, 10 mg/kg, i.p.) groups. Von Frey filaments were used to examine the periorbital and hind paw mechanical allodynia. Dark-light box (DLB), elevated plus maze (EPM), and open field arena (OFA) were used to evaluate light sensitivity and anxiety-related behaviors. The effects of LVC on CSD parameters, somatosensory evoked potentials, and baseline dural EEG (electroencephalography) were investigated. Possible CSD-induced c-fos expression was studied with Western Blot. Blood-brain barrier integrity in cortex was examined with Evans blue assay.

RESULTS

LVC and NTG administration robustly reduced periorbital mechanical thresholds in rats and induced anxiety-like behaviors and photophobia within 30 and 120 min, respectively. LVC induced migraine-like phenotype recovered in 2 h while NTG group did not fully recover before 4 h. Both LVC and NTG did not provoke DC (direct current) shift, EEG alterations or cortical c-fos expression characteristic to CSD. LVC did not induce de novo CSD and affect KCl (potassium chloride)-induced CSD parameters except for an increase in propagation failure. However, NTG significantly increased both CSD susceptibility and propagation failure. Somatosensory evoked potential (SSEP) configurations were not altered in both LVC and NTG groups, but SSEP latencies were prolonged after CSD. Acute LVC or NTG injection did not increase cortical BBB permeability.

CONCLUSIONS

Single LVC administration induced the fastest manifestation and recovery of acute migraine-like phenotype which was not mediated by CSD waves in the cerebral cortex. We suppose LVC triggered rapid-onset migraine-like symptoms are probably related to functional alterations in the trigeminal nociceptive system and K⁺ channel opening properties of LVC. Understanding the neurobiological mechanisms of this nociceptive window, may provide a novel target in migraine treatment.

Experimental and Clinical Investigation of Cytokines in Migraine: A Narrative Review

The role of neuroinflammation in the pathophysiology of migraines is increasingly being recognized, and cytokines, which are important endogenous substances involved in immune and inflammatory responses, have also received attention. This review examines the current literature on neuroinflammation in the pathogenesis of migraine. Elevated TNF-α, IL-1β, and IL-6 levels have been identified in non-invasive mouse models with cortical spreading depolarization (CSD). Various mouse models to induce migraine attack-like symptoms also demonstrated elevated inflammatory cytokines and findings suggesting differences between episodic and chronic migraines and between males and females. While studies on human blood during migraine attacks have reported no change in TNF-α levels and often inconsistent results for IL-1β and IL-6 levels, serial analysis of cytokines in jugular venous blood during migraine attacks revealed consistently increased IL-1β, IL-6, and TNF-α. In a study on the interictal period, researchers reported higher levels of TNF-α and IL-6 compared to controls and no change regarding IL-1β levels. Saliva-based tests suggest that IL-1β might be useful in discriminating against migraine. Patients with migraine may benefit from a cytokine perspective on the pathogenesis of migraine, as there have been several encouraging reports suggesting new therapeutic avenues.

The putative role of neuroinflammation in the complex pathophysiology of migraine: From bench to bedside

The implications of neurogenic inflammation and neuroinflammation in the pathophysiology of migraine have been clearly demonstrated in preclinical migraine models involving several sites relevant in the trigemino-vascular system, including dural vessels and trigeminal endings, the trigeminal ganglion, the trigeminal nucleus caudalis as well as central trigeminal pain processing structures. In this context, a relevant role has been attributed over the years to some sensory and parasympathetic neuropeptides, in particular calcitonin gene neuropeptide, vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide. Several preclinical and clinical lines of evidence also support the implication of the potent vasodilator and messenger molecule nitric oxide in migraine pathophysiology. All these molecules are involved in vasodilation of the intracranial vasculature, as well as in the peripheral and central sensitization of the trigeminal system. At meningeal level, the engagement of some immune cells of innate immunity, including mast-cells and dendritic cells, and their mediators, has been observed in preclinical migraine models of neurogenic inflammation in response to sensory neuropeptides release due to trigemino-vascular system activation. In the context of neuroinflammatory events implicated in migraine pathogenesis, also activated glial cells in the peripheral and central structures processing trigeminal nociceptive signals seem to play a relevant role. Finally, cortical spreading depression, the pathophysiological substrate of migraine aura, has been reported to be associated with inflammatory mechanisms such as pro-inflammatory cytokine upregulation and intracellular signalling. Reactive astrocytosis consequent to cortical spreading depression is linked to an upregulation of these inflammatory markers. The present review summarizes current findings on the roles of immune cells and inflammatory responses in the pathophysiology of migraine and their possible exploitation in the view of innovative disease-modifying strategies.

DNA-methylation and immunological response in medication overuse headache

OBJECTIVE

To investigate whether medication-overuse headache patients have differential DNA-methylation pattern.

METHODS

We collected blood samples from 120 medication-overuse headache-patients, 57 controls (29 episodic migraine patients and 28 healthy controls) in a hypothesis-generating cross-sectional case-control pilot study; 100 of the medication-overuse headache-patients were followed for six months and samples were collected at two and six months for the longitudinal methylation analyses. Blood cell proportions of leucocytes (neutrophils, NK-cells, monocytes, CD8+ and CD4+ T-cells, and B-cells) and the neutrophile-lymphocyte ratio were estimated using methylation data as a measure for immunological analysis and a cell type-specific epigenome wide association study was conducted between medication-overuse headache-patients and controls, and longitudinally for reduction in headache days/month among medication-overuse headache-patients.

RESULTS

We found a higher neutrophile-lymphocyte ratio in medication-overuse headache-patients compared to controls, indicating a higher immunological response in medication-overuse headache-patients (false discovery rate (adjusted p-value)<0.001). Reduction in headache days/month (9.8; 95% CI 8.1-11.5) was associated with lower neutrophile-lymphocyte ratio (false discovery rate adjusted p-value = 0.041).Three genes (CORIN, CCKBR and CLDN9) were hypermethylated in specific cell types in medication-overuse headache-patients compared to controls. No methylation differences were associated with reduction in headache days in medication-overuse headache-patients after six months.

CONCLUSION

This pilot study was consistent with higher immunological response in medication-overuse headache-patients which decreased with a reduction in headache days in longitudinal analysis. medication-overuse headache-patients exhibited differential methylation in innate immune cells but did not exhibit longitudinal differences with alterations in headache days. Our study creates hypotheses for further biomarker searches.ClinicalTrials.gov Identifier: NCT02993289.

Migraine attacks are of peripheral origin: the debate goes on

BACKGROUND

Despite the pervasiveness of migraine, the underlying pathophysiological mechanisms initiating migraine attacks are far from well understood and are matter of scientific debate.

OBJECTIVE

In this narrative review, we discuss key evidence for that suggest a peripheral origin or central origin and provide directions for future studies that may provide further clarification.

DISCUSSION

Migraine pathogenesis is considered to involve the trigeminovascular system, a term that encompasses the trigeminal nerve and its axonal projections to the intracranial blood vessels. Beyond any doubt both peripheral and central mechanisms are involved in migraine pathogenesis, but an unresolved question is the how the initial activation occurs in a migraine attack. Evidence favoring a peripheral origin of migraine attacks, i.e., initial events occur outside of the blood-brain barrier, include the importance of sensitization of perivascular sensory afferents early on in a migraine attack. Evidence favoring a central origin include the occurrence of prodromal symptoms, migraine aura, and activation of structures within the central nervous system early in and during a migraine attack.

CONCLUSIONS

Both peripheral and central mechanisms are likely involved in a migraine attack, e.g., peripheral nociceptive input is necessary for pain transmission and cortical activity is necessary for pain perception. Yet, the debate of whether migraine attacks are initiated a peripheral or central site remains unresolved. The increased focus on prodromal symptoms and on the development of a human model of migraine aura will possibly provide key arguments needed to answer this question in the near future. Until then, we cannot draw firm conclusions and the debate goes on.

VIDEO LINK

Video recording of the debate held at the 1st International Conference on Advances in Migraine Sciences (ICAMS 2022, Copenhagen, Denmark) is available at: https://www.youtube.com/watch?v=NC0nlcKohz0 .

Pathophysiology of migraine aura

Migraine aura occurs in about a third of patients with migraine and consists of a group of transient focal neurological symptoms that appear from 5 to 60min and then resolve prior to or in the early phase of a migraine headache attack. Migraine auras may consist of visual, language, unilateral sensory, or motor symptoms. There has been considerable debate as to the origins of the migrainous aura. Investigations during physiologically induced visual auras suggest that the phenomenon of cortical spreading depression or its human equivalent underpins the migraine aura. Single gene defects have been linked to relatively rare forms of the motor subtypes of aura known as familial hemiplegic migraine (FHM). These include CACNA1A (FHM1), ATP1A2 (FHM2), and SCN1A (FHM3). In the familial hemiplegic forms of migraine, the more typical forms of aura are almost always also present. Despite ample epidemiological evidence of increased heritability of migraine with aura compared to migraine without aura, identification of the specific variants driving susceptibility to the more common forms of aura has been problematic thus far. In the first genome-wide association study (GWAS) that focused migraine with aura, a single SNP rs835740 reached genome-wide significance. Unfortunately, the SNP did show statistical significance in a later meta-analysis which included GWAS data from subsequent studies. Here, we review the clinical features, pathophysiological theories, and currently available potential evidence for the genetic basis of migraine aura.

What imaging has revealed about migraine and chronic migraine

Although migraine pathophysiology is not yet entirely understood, it is now established that migraine should be viewed as a complex neurological disease, which involves the interplay of different brain networks and the release of signaling molecules, instead of a pure vascular disorder. The field of migraine research has also progressed significantly due to the advancement of brain imaging techniques. Numerous studies have investigated the relation between migraine pathophysiology and cerebral hemodynamic changes, showing that vascular changes are neither necessary nor sufficient to cause the migraine pain. Abnormal function and structure of key cortical, subcortical, and brainstem regions involved in multisensory, including pain, processing have been shown to occur in migraine patients during both an acute attack and the interictal phase. Whether brain imaging alterations represent a predisposing trait or are the consequence of the recurrence of headache attacks is still a matter of debate. It is highly likely that brain functional and structural alterations observed in migraine patients derive from the interaction between predisposing brain traits and experience-dependent responses. Neuroimaging studies have also enriched our knowledge of the mechanisms responsible for migraine chronification and have shed light on the mechanisms of actions of acute and preventive migraine treatments.

Evaluating migraine with typical aura with neuroimaging

Objective

To provide an up-to-date narrative literature review of imaging in migraine with typical aura, as a means to understand better migraine subtypes and aura biology.

Background

Characterizing subtypes of migraine with typical aura and appreciating possible biological differences between migraine with and without aura, are important to understanding the neurobiology of aura and trying to advance personalized therapeutics in this area through imaging biomarkers. One means of doing this over recent years has been the use of increasingly advanced neuroimaging techniques.

Methods

We conducted a literature review of neuroimaging studies in migraine with aura, using a PubMed search for terms 'imaging migraine', 'aura imaging', 'migraine with aura imaging', 'migraine functional imaging' and 'migraine structural imaging'. We collated the findings of the main studies, excluding small case reports and series with n < 6, and have summarized these and their implications for better understanding of aura mechanisms.

Results

Aura is likely mediated by widespread brain dysfunction in areas involving, but not limited to, visual cortex, somatosensory and insular cortex, and thalamus. Higher brain excitability in response to sensory stimulation and altered resting-state functional connectivity in migraine sufferers with aura could have a genetic component. Pure visual aura compared to visual aura with other sensory or speech symptoms as well, may involve different functional reorganization of brain networks and additional mitochondrial dysfunction mediating more aura symptoms.

Conclusion

There is a suggestion of at least some distinct neurobiological differences between migraine with and without aura, despite the shared phenotypic similarity in headache and other migraine-associated symptoms. It is clear from the vast majority of aura phenotypes being visual that there is a particular predisposition of the occipital cortex to aura mechanisms. Why this is the case, along with the relationships between cortical spreading depression and headache, and the reasons why aura does not consistently present in affected individuals, are all important research questions for the future.

Prevalence and clinical characteristics of white matter hyperintensities in Migraine: A meta-analysis

BACKGROUND

Current evidences show an increased risk of white matter hyperintensities (WMHs) in migraineurs compared to age-matched controls. However, WMHs prevalence and the associations between WMHs and clinical characteristics in migraineurs have not been systematically evaluated using a meta-analytical approach. This study explored the pooled prevalence of WMHs and the associations of WMHs with the clinical characteristics in patients with migraine.

METHODS

A systematic review and meta-analysis of observational studies reporting the occurrence and clinical characteristics of patients with WMHs attributed to migraine was performed. We searched the PubMed, Web of Science, and Embase databases. Random-effects models were used to calculate the pooled prevalence rate, odds ratio (OR), or mean difference (MD) with corresponding 95% confidence intervals (CIs).

RESULTS

Thirty eligible studies were identified including 3,502 migraineurs aged 37.2 (mean) years. The pooled WMHs prevalence was 44 %, 45 %, and 38 % in migraine, migraine with aura, and migraine without aura groups, respectively. In migraineurs with WMHs, the frontal lobe and subcortical white matter were the most susceptible area. Compared with non-migraine controls, patients with migraine had increased odds for WMHs (OR 4.32, 95 % CI = 2.56-7.28, I² = 67 %). According to reported univariable results from included studies, pooled analysis showed that clinical characteristics including age, presence of aura, disease duration, hypertension, diabetes mellitus and right-to-left shunt were associated with the presence of WMHs. Migraine pain and aura characteristics were not related to WMHs.

CONCLUSIONS

These data suggest that WMHs are common in migraine, especially in those who are older or have aura, hypertension, diabetes mellitus, or right-to-left shunt. A better understanding of the WMHs attributed to migraine is needed in future studies.

Calcitonin gene-related peptide (CGRP) is a key molecule released in acute migraine attacks-Successful translation of basic science to clinical practice

Migraine is a highly prevalent neurovascular disorder afflicting more than 15% of the global population. Nearly three times more females are afflicted by migraine in the 18-50 years age group, compared to males. Migraine attacks are most often sporadic, but a subgroup of individuals experience a gradual increase in frequency over time; among these, up to 1%-2% of the global population develop chronic migraine. Although migraine symptoms have been known for centuries, the underlying mechanisms remain largely unknown. Two theories have dominated the current thinking-a neurovascular theory and a central neuronal theory with the origin of the attacks in the hypothalamus. During the last decades, the understanding of migraine has markedly advanced. This is supported by the early seminal demonstration of the trigeminovascular reflex 35 years ago and the insight that calcitonin gene-related peptide (CGRP) is a key molecule released in acute migraine attacks. The more recent findings that gepants, small molecule CGRP receptor blockers, and monoclonal antibodies generated against CGRP, or its canonical receptor are useful for the treatment of migraine, are other important issues. CGRP has been established as a key molecule in the neurobiology of migraine. Moreover, monoclonal antibodies to CGRP or the CGRP receptor represent a breakthrough in the understanding of migraine pathophysiology and have emerged as an efficacious prophylactic treatment for patients with severe migraine with excellent tolerability. This review describes the progression of research to reach the clinical usefulness of a large group of molecules that have in common the interaction with CGRP mechanisms in the trigeminal system to alleviate the burden for individuals afflicted by migraine.

Immunologic aspects of migraine: A review of literature

Migraine headaches are highly prevalent, affecting 15% of the population. However, despite many studies to determine this disease's mechanism and efficient management, its pathophysiology has not been fully elucidated. There are suggested hypotheses about the possible mediating role of mast cells, immunoglobulin E, histamine, and cytokines in this disease. A higher incidence of this disease in allergic and asthma patients, reported by several studies, indicates the possible role of brain mast cells located around the brain vessels in this disease. The mast cells are more specifically within the dura and can affect the trigeminal nerve and cervical or sphenopalatine ganglion, triggering the secretion of substances that cause migraine. Neuropeptides such as calcitonin gene-related peptide (CGRP), neurokinin-A, neurotensin (NT), pituitary adenylate-cyclase-activating peptide (PACAP), and substance P (SP) trigger mast cells, and in response, they secrete pro-inflammatory and vasodilatory molecules such as interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) as a selective result of corticotropin-releasing hormone (CRH) secretion. This stress hormone contributes to migraine or intensifies it. Blocking these pathways using immunologic agents such as CGRP antibody, anti-CGRP receptor antibody, and interleukin-1 beta (IL-1β)/interleukin 1 receptor type 1 (IL-1R1) axis-related agents may be promising as potential prophylactic migraine treatments. This review is going to summarize the immunological aspects of migraine.

Calcitonin Gene-Related Peptide (CGRP) and Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) in Migraine Pathogenesis

Migraine is a prevalent and debilitating neurologic disorder. Advancements in understanding the underlying pathophysiological mechanisms are spearheading the effort to introduce disease-specific treatment options. In recent years this effort has largely focused on alteration of endogenous neuropeptide signaling, namely the peptides calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP). Human studies into the pathophysiological underpinnings of CGRP and PACAP in migraine are manifold and here we review the works investigating these neuropeptides in patients suffering from migraine in order to elucidate the background for developing new treatment options for this vastly disabling disorder.

Magnetic resonance spectroscopy studies in migraine

This review summarizes major findings and recent advances in magnetic resonance spectroscopy (MRS) of migraine. A multi database search of PubMed, EMBASE, and Web of Science was performed with variations of magnetic resonance spectroscopy and headache until 20th September 2021. The search generated 2897 studies, 676 which were duplicates and 1836 were not related to headache. Of the remaining 385 studies examined, further exclusions for not migraine (n = 114), and not MRS of human brain (n = 128), and non-original contributions (n = 51) or conferences (n = 24) or case studies (n = 11) or non-English (n = 3), were applied. The manuscripts of all resulting reports were reviewed for their possible inclusion in this manuscript (n = 54). The reference lists of all included reports were carefully reviewed and articles relevant to this review were added (n = 2).Included are 56 studies of migraine with and without aura that involve magnetic resonance spectroscopy of the human brain. The topics are presented in the form of a narrative review. This review aims to provide a summary of the metabolic changes measured by MRS in patients with migraine. Despite the variability reported between studies, common findings focused on regions functionally relevant to migraine such as occipital cortices, thalamic nuclei, cerebellum and cingulate. The most reproducible results were decreased N-acetyl-aspartate (NAA) in cerebellum in patients with hemiplegic migraine and in the thalamus of chronic migraine patients. Increased lactate (Lac) in the occipital cortex was found for migraine with aura but not in subjects without aura. MRS studies support the hypothesis of impaired energetics and mitochondrial dysfunction in migraine. Although results regarding GABA and Glu were less consistent, studies suggest there might be an imbalance of these important inhibitory and excitatory neurotransmitters in the migraine brain. Multinuclear imaging studies in migraine with and without aura, predominantly investigating phosphorous, report alterations of PCr in occipital, parietal, and posterior brain regions. There have been too few studies to assess the diagnostic relevance of sodium imaging in migraine.

Cerebro-Cerebellar Networks in Migraine Symptoms and Headache

The cerebellum is associated with the biology of migraine in a variety of ways. Clinically, symptoms such as fatigue, motor weakness, vertigo, dizziness, difficulty concentrating and finding words, nausea, and visual disturbances are common in different types of migraine. The neural basis of these symptoms is complex, not completely known, and likely involve activation of both specific and shared circuits throughout the brain. Posterior circulation stroke, or neurosurgical removal of posterior fossa tumors, as well as anatomical tract tracing in animals, provided the first insights to theorize about cerebellar functions. Nowadays, with the addition of functional imaging, much progress has been done on cerebellar structure and function in health and disease, and, as a consequence, the theories refined. Accordingly, the cerebellum may be useful but not necessary for the execution of motor, sensory or cognitive tasks, but, rather, would participate as an efficiency facilitator of neurologic functions by improving speed and skill in performance of tasks produced by the cerebral area to which it is reciprocally connected. At the subcortical level, critical regions in these processes are the basal ganglia and thalamic nuclei. Altogether, a modulatory role of the cerebellum over multiple brain regions appears compelling, mainly by considering the complexity of its reciprocal connections to common neural networks involved in motor, vestibular, cognitive, affective, sensory, and autonomic processing—all functions affected at different phases and degrees across the migraine spectrum. Despite the many associations between cerebellum and migraine, it is not known whether this structure contributes to migraine initiation, symptoms generation or headache. Specific cerebellar dysfunction via genetically driven excitatory/inhibitory imbalances, oligemia and/or increased risk to white matter lesions has been proposed as a critical contributor to migraine pathogenesis. Therefore, given that neural projections and functions of many brainstem, midbrain and forebrain areas are shared between the cerebellum and migraine trigeminovascular pathways, this review will provide a synopsis on cerebellar structure and function, its role in trigeminal pain, and an updated overview of relevant clinical and preclinical literature on the potential role of cerebellar networks in migraine pathophysiology.

Imaging the inflammatory phenotype in migraine

Several preclinical and clinical lines of evidence suggest a role of neuroinflammation in migraine. Neuroimaging offers the possibility to investigate and localize neuroinflammation in vivo in patients with migraine, and to characterize specific inflammatory constituents, such as vascular permeability, and macrophage or microglia activity. Despite all imaging data accumulated on neuroinflammation across the past three decades, an overview of the imaging evidence of neuroinflammation in migraine is still missing.We conducted a systematic review in the Pubmed and Embase databases to evaluate existing imaging data on inflammation in migraine, and to identify gaps in the literature. We included 20 studies investigating migraine without aura (N = 4), migraine with aura (N = 8), both migraine with and without aura (N = 3), or hemiplegic migraine (N = 5).In migraine without aura, macrophage activation was not evident. In migraine with aura, imaging evidence suggested microglial and parameningeal inflammatory activity. Increased vascular permeability was mostly found in hemiplegic migraine, and was atypical in migraine with and without aura. Based on the weight of existing and emerging data, we show that most studies have concentrated on demonstrating increased vascular permeability as a marker of neuroinflammation, with tools that may not have been optimal. In the future, novel, more sensitive techniques, as well as imaging tracers delineating specific inflammatory pathways may further bridge the gap between preclinical and clinical findings.

Effectiveness and Safety of Memantine for Headache: A Meta-analysis of Randomized Controlled Studies

OBJECTIVE

The effectiveness and safety of memantine for headache are elusive, and this meta-analysis aimed to explore the influence of memantine versus placebo for headache.

METHODS

We have searched PubMed, Embase, Web of science, EBSCO, and Cochrane library databases through May 2021 and included randomized controlled trials reporting memantine versus placebo for headache patients. This meta-analysis is performed using the random-effects model.

RESULTS

Our meta-analysis included 4 randomized controlled trials and 229 patients. Compared with control group for headache, memantine treatment could substantially reduce headache days (mean difference [MD] = -3.10; 95% confidence interval [CI] = -5.46 to -0.75; P = 0.01), pain intensity (MD, -0.43; 95% CI, -0.85 to -0.01; P = 0.04), monthly attack frequency (MD, -2.14; 95% CI, -2.83 to -1.46; P < 0.00001), and Migraine Disability Assessment Test (MD, -5.63; 95% CI, -6.46 to -4.79; P < 0.00001) but revealed no significant influence on days for acute pain medications, adverse events, or nausea/vomiting.

CONCLUSIONS

Memantine treatment is effective and safe to treat headache.

Brain barriers and their potential role in migraine pathophysiology

Migraine is a ubiquitous neurologic disease that afflicts people of all ages. Its molecular pathogenesis involves peptides that promote intracranial vasodilation and modulate nociceptive transmission upon release from sensory afferents of cells in the trigeminal ganglion and parasympathetic efferents of cells in the sphenopalatine ganglion. Experimental data have confirmed that intravenous infusion of these vasoactive peptides induce migraine attacks in people with migraine, but it remains a point of scientific contention whether their site of action lies outside or within the central nervous system. In this context, it has been hypothesized that transient dysfunction of brain barriers before or during migraine attacks might facilitate the passage of migraine-inducing peptides into the central nervous system. Here, we review evidence suggestive of brain barrier dysfunction in migraine pathogenesis and conclude with lessons learned in order to provide directions for future research efforts.

A critical review of the neurovascular nature of migraine and the main mechanisms of action of prophylactic antimigraine medications

INTRODUCTION

Migraine involves neurovascular, functional, and anatomical alterations. Migraineurs experience an intense unilateral and pulsatile headache frequently accompanied with vomiting, nausea, photophobia, etc. Although there is no ideal preventive medication, frequency in migraine days may be partially decreased by some prophylactics, including antihypertensives, antidepressants, antiepileptics, and CGRPergic inhibitors. However, the mechanisms of action involved in antimigraine prophylaxis remain elusive.

AREAS COVERED

This review recaps some of the main neurovascular phenomena related to migraine and currently available preventive medications. Moreover, it discusses the major mechanisms of action of the recommended prophylactic medications.

EXPERT OPINION

In the last three years, migraine prophylaxis has evolved from nonspecific to specific antimigraine treatments. Overall, nonspecific treatments  mainly involve neural actions, whereas specific pharmacotherapy (represented by CGRP receptor antagonists and CGRPergic monoclonal antibodies) is predominantly mediated by neurovascular mechanisms that may include, among others: (i) reduction in the cortical spreading depression (CSD)-associated events; (ii) inhibition of pain sensitization; (iii) blockade of neurogenic inflammation; and/or (iv) increase in cranial vascular tone. Accordingly, the novel antimigraine prophylaxis promises to be more effective, devoid of significant adverse effects (unlike nonspecific treatments), and more beneficial for the quality of life of migraineurs.

The locus of Action of CGRPergic Monoclonal Antibodies Against Migraine: Peripheral Over Central Mechanisms

Migraine is a complex neurovascular disorder characterized by attacks of moderate to severe unilateral headache, accompanied by photophobia among other neurological signs. Although an arsenal of antimigraine agents is currently available in the market, not all patients respond to them. As Calcitonin Gene-Related Peptide (CGRP) plays a key role in the pathophysiology of migraine, CGRP receptor antagonists (gepants) have been developed. Unfortunately, further pharmaceutical development (for olcegepant and telcagepant) was interrupted due to pharmacokinetic issues observed during the Randomized Clinical Trials (RCT). On this basis, the use of monoclonal antibodies (mAbs; immunoglobulins) against CGRP or its receptor has recently emerged as a novel pharmacotherapy to treat migraines. RCT showed that these mAbs are effective against migraines producing fewer adverse events. Presently, the U.S. Food and Drug Administration approved four mAbs, namely: (i) erenumab; (ii) fremanezumab; (iii) galcanezumab; and (iv) eptinezumab. In general, specific antimigraine compounds exert their action in the trigeminovascular system, but the locus of action (peripheral vs. central) of the mAbs remains elusive. Since these mAbs have a molecular weight of ∼150 kDa, some studies rule out the relevance of their central actions as they seem unlikely to cross the Blood-Brain Barrier (BBB). Considering the therapeutic relevance of this new class of antimigraine compounds, the present review has attempted to summarize and discuss the current evidence on the probable sites of action of these mAbs.

Role of Neuroinflammation and Blood-Brain Barrier Permutability on Migraine

Currently, migraine is treated mainly by targeting calcitonin gene-related peptides, although the efficacy of this method is limited and new treatment strategies are desired. Neuroinflammation has been implicated in the pathogenesis of migraine. In patients with migraine, peripheral levels of pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-α, are known to be increased. Additionally, animal models of headache have demonstrated that immunological responses associated with cytokines are involved in the pathogenesis of migraine. Furthermore, these inflammatory mediators might alter the function of tight junctions in brain vascular endothelial cells in animal models, but not in human patients. Based on clinical findings showing elevated IL-1β, and experimental findings involving IL-1β and both the peripheral trigeminal ganglion and central trigeminal vascular pathways, regulation of the Il-1β/IL-1 receptor type 1 axis might lead to new treatments for migraine. However, the integrity of the blood-brain barrier is not expected to be affected during attacks in patients with migraine.

Cortical excitability in migraine: Contributions of magnetic resonance imaging

Migraine is characterized by symptoms related to cortical hyperexcitability such as photophobia, phonophobia, osmophobia and allodynia. One-third of migraineurs experience aura, whose neurophysiological substrate is thought to be cortical spreading depression (CSD). Functional magnetic resonance imaging (MRI) has shown the migraine aura to be characterized by cerebral hyperactivity/hyperperfusion followed by hypometabolism/hypoperfusion spreading along the occipital cortex with the same spatiotemporal organization as the experimentally triggered CSD. The link between migraine aura and headache remains undetermined. Neuroimaging studies have failed to show a leakage of the blood-brain barrier, which was suspected to occur during CSD and to cause the stimulation of trigeminal nociceptive receptors. However, recent studies have highlighted the involvement of neuroglial inflammation and other studies have suggested that a common central network plays a role in the link between CSD and migraine pain. Finally, MRI has made it possible to study the contribution of metabolites such as glutamic acid, γ-amino-butyric acid and sodium in the pathophysiology of hyperexcitability in migraine.

Narrative review of neuroimaging in migraine with aura

OBJECTIVE

To improve the understanding of the role and utility of various neuroimaging modalities (clinical and research) for the evaluation of migraine aura (MA) and hemiplegic migraine during the ictal and interictal phases.

BACKGROUND

MA is defined by reversible neurologic symptoms and is considered a manifestation of a primary condition. As such, most patients with MA do not require imaging. However, if there are atypical features, change in symptom pattern, or it is a first-time presentation, neuroimaging may be used to evaluate for secondary conditions. Neuroimaging includes many modalities, and it is important to consider what information is being captured by these modalities (i.e., structural vs. functional). Imaging abnormalities may be noted both during (ictal) and between (interictal) MA attacks, and it is important for clinicians to be familiar with neuroimaging findings reported in migraine with aura (MWA) compared with other conditions.

METHODS

With the assistance of a medical librarian, we performed a review of the literature pertaining to MWA and neuroimaging in PubMed. Search terms included were magnetic resonance imaging, positron-emission tomography, single photon-emission computed tomography, functional magnetic resonance imaging, and migraine with aura. We hand-searched these references to inform our subsequent literature review.

RESULTS

Acute MA can be associated with several unique neuroimaging findings-reversible cortical diffusion restriction, cortical venous engorgement, and a "biphasic" transition from hypoperfusion to hyperperfusion. Imaging findings during MA tend to span more than one vascular territory. Between acute attacks, neuroimaging in people with MWA can resemble migraine without aura in terms of white matter abnormalities and "infarct-like lesions." Research imaging modalities such as volumetric analysis and functional imaging have demonstrated unique findings in migraine with aura.

CONCLUSION

Although migraine is a clinical diagnosis, understanding of neuroimaging findings in MWA can help clinicians interpret imaging findings and improve patient care.

Migraine and neuroinflammation: the inflammasome perspective

BACKGROUND

Neuroinflammation has an important role in the pathophysiology of migraine, which is a complex neuro-glio-vascular disorder. The main aim of this review is to highlight findings of cortical spreading depolarization (CSD)-induced neuroinflammatory signaling in brain parenchyma from the inflammasome perspective. In addition, we discuss the limited data of the contribution of inflammasomes to other aspects of migraine pathophysiology, foremost the activation of the trigeminovascular system and thereby the generation of migraine pain.

MAIN BODY

Inflammasomes are signaling multiprotein complexes and key components of the innate immune system. Their activation causes the production of inflammatory cytokines that can stimulate trigeminal neurons and are thus relevant to the generation of migraine pain. The contribution of inflammasome activation to pain signaling has attracted considerable attention in recent years. Nucleotide-binding domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) is the best characterized inflammasome and there is emerging evidence of its role in a variety of inflammatory pain conditions, including migraine. In this review, we discuss, from an inflammasome point of view, cortical spreading depolarization (CSD)-induced neuroinflammatory signaling in brain parenchyma, the connection with genetic factors that make the brain vulnerable to CSD, and the relation of the inflammasome with diseases that are co-morbid with migraine, including stroke, epilepsy, and the possible links with COVID-19 infection.

CONCLUSION

Neuroinflammatory pathways, specifically those involving inflammasome proteins, seem promising candidates as treatment targets, and perhaps even biomarkers, in migraine.

Migraine Is More Than Just Headache: Is the Link to Chronic Fatigue and Mood Disorders Simply Due to Shared Biological Systems?

Migraine is a symptomatically heterogeneous condition, of which headache is just one manifestation. Migraine is a disorder of altered sensory thresholding, with hypersensitivity among sufferers to sensory input. Advances in functional neuroimaging have highlighted that several brain areas are involved even prior to pain onset. Clinically, patients can experience symptoms hours to days prior to migraine pain, which can warn of impending headache. These symptoms can include mood and cognitive change, fatigue, and neck discomfort. Some epidemiological studies have suggested that migraine is associated in a bidirectional fashion with other disorders, such as mood disorders and chronic fatigue, as well as with other pain conditions such as fibromyalgia. This review will focus on the literature surrounding alterations in fatigue, mood, and cognition in particular, in association with migraine, and the suggested links to disorders such as chronic fatigue syndrome and depression. We hypothesize that migraine should be considered a neural disorder of brain function, in which alterations in aminergic networks integrating the limbic system with the sensory and homeostatic systems occur early and persist after headache resolution and perhaps interictally. The associations with some of these other disorders may allude to the inherent sensory sensitivity of the migraine brain and shared neurobiology and neurotransmitter systems rather than true co-morbidity.

The Efficacy of Memantine for the Treatment of Migraine: A Meta-Analysis of Randomized Controlled Studies

INTRODUCTION

The efficacy of memantine for migraine remains controversial. We conduct a systematic review and meta-analysis to explore the influence of memantine versus placebo on treatment in migraine patients.

METHODS

We search PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through February 2020 for randomized controlled trials assessing the effect of memantine versus placebo on treatment efficacy in migraine patients. This meta-analysis is performed using the random-effect model.

RESULTS

Three randomized controlled trials are included in the meta-analysis. Overall, compared with control group in migraine patients, memantine treatment is associated with substantially reduced monthly attack frequency (mean difference [MD], -2.14; 95% confidence interval [CI], -2.83 to -1.46; P < 0.00001), number of migraine days (MD, -4.17; 95% CI, -6.40 to -1.93; P = 0.0003) and Migraine Disability Assessment (MD, -5.63; 95% CI, -6.46 to -4.79; P < 0.00001), but demonstrates no obvious influence on acute pain medications (MD, -1.23; 95% CI, -4.63 to 2.17; P = 0.48).

CONCLUSIONS

Memantine treatment may benefit to the control of migraine.

Evidence that blood-CSF barrier transport, but not inflammatory biomarkers, change in migraine, while CSF sVCAM1 associates with migraine frequency and CSF fibrinogen

Objective

Our objective is to explore whether blood–cerebrospinal fluid (CSF) barrier biomarkers differ in episodic migraine (EM) or chronic migraine (CM) from controls.

Background

Reports of blood–brain barrier and blood–cerebrospinal fluid barrier (BCSFB) disruption in migraine vary. Our hypothesis is that investigation of biomarkers associated with blood, CSF, brain, cell adhesion, and inflammation will help elucidate migraine pathophysiology.

Methods

We recruited 14 control volunteers without headache disorders and 42 individuals with EM or CM as classified using the International Classification of Headache Disorders, 3rd edition, criteria in a cross‐sectional study located at our Pasadena and Stanford headache research centers in California. Blood and lumbar CSF samples were collected once from those diagnosed with CM or those with EM during two states: during a typical migraine, before rescue therapy, with at least 6/10 level of pain (ictal); and when migraine free for at least 48 h (interictal). The average number of headaches per month over the previous year was estimated by those with EM; this enabled comparison of biomarker changes between controls and three headache frequency groups: <2 per month, 2–14 per month, and CM. Blood and CSF biomarkers were determined using antibody‐based methods.

Results

Antimigraine medication was only taken by the EM and CM groups. Compared to controls, the migraine group had significantly higher mean CSF–blood quotients of albumin (Q_alb: mean ± standard deviation (SD): 5.6 ± 2.3 vs. 4.1 ± 1.9) and fibrinogen (Q_fib mean ± SD: 1615 ± 99.0 vs. 86.1 ± 55.0). Mean CSF but not plasma soluble vascular cell adhesion molecule‐1 (sVCAM‐1) levels were significantly higher in those with more frequent migraine: (4.5 ng/mL ± 1.1 in those with <2 headache days a month; 5.5 ± 1.9 with 2–14 days a month; and 7.1 ± 2.9 in CM), while the Q_fib ratio was inversely related to headache frequency. We did not find any difference in individuals with EM or CM from controls for CSF cell count, total protein, matrix metalloproteinase‐9, soluble platelet‐derived growth factor receptor β, tumor necrosis factor‐alpha, interferon‐gamma, interleukin (IL)‐6, IL‐8, IL‐10, or C‐reactive protein.

Conclusions

The higher Q_alb and Q_fib ratios may indicate that the transport of these blood‐derived proteins is disturbed at the BCSFB in persons with migraine. These changes most likely occur at the choroid plexus epithelium, as there are no signs of typical endothelial barrier disruption. The most striking finding in this hypothesis‐generating study of migraine pathophysiology is that sVCAM‐1 levels in CSF may be a biomarker of higher frequency of migraine and CM. An effect from migraine medications cannot be excluded, but there is no known mechanism to suggest they have a role in altering the CSF biomarkers.

Glutamate levels and perfusion in pons during migraine attacks: A 3T MRI study using proton spectroscopy and arterial spin labeling

Migraine is a complex disorder, involving peripheral and central brain structures, where mechanisms and site of attack initiation are an unresolved puzzle. While abnormal pontine neuronal activation during migraine attacks has been reported, exact implication of this finding is unknown. Evidence suggests an important role of glutamate in migraine, implying a possible association of pontine hyperactivity to increased glutamate levels. Migraine without aura patients were scanned during attacks after calcitonin gene-related peptide and sildenafil in a double-blind, randomized, double-dummy, cross-over design, on two separate study days, by proton magnetic resonance spectroscopy and pseudo-continuous arterial spin labeling at 3T. Headache characteristics were recorded until 24 h after drug administrations. Twenty-six patients were scanned during migraine, yielding a total of 41 attacks. Cerebral blood flow increased in dorsolateral pons, ipsilateral to pain side during attacks, compared to outside attacks (13.6%, p = 0.009). Glutamate levels in the same area remained unchanged during attacks (p = 0.873), while total creatine levels increased (3.5%, p = 0.041). In conclusion, dorsolateral pontine activation during migraine was not associated with higher glutamate levels. However, the concurrently increased total creatine levels may suggest an altered energy metabolism, which should be investigated in future studies to elucidate the role of pons in acute migraine.

Early treatment with sumatriptan prevents PACAP38-induced migraine: A randomised clinical trial

OBJECTIVE

To determine whether early treatment with sumatriptan can prevent PACAP38-induced migraine attacks.

METHODS

A total of 37 patients with migraine without aura were enrolled between July 2018 to December 2019. All patients received an intravenous infusion of 10 picomole/kg/min of PACAP38 over 20 min followed by an intravenous infusion of 4 mg sumatriptan or placebo over 10 min on two study days in a randomised, double-blind, placebo-controlled, crossover study.

RESULTS

Of 37 patients enrolled, 26 (70.3%) completed the study and were included in analyses. Of the 26 patients, four (15%) developed a PACAP38-induced migraine attack on sumatriptan and 11 patients (42%) on placebo (p = 0.016). There were no differences in area under the curve for headache intensity between sumatriptan (mean AUC 532) and placebo (mean AUC 779) (p = 0.35). Sumatriptan significantly constricted the PACAP38-dilated superficial temporal artery immediately after infusion (T30) compared with infusion of placebo (p < 0.001).Conclusions and relevance: Early treatment with intravenously administered sumatriptan prevented PACAP38-induced migraine. Prevention of migraine attacks was associated with vasoconstriction by sumatriptan in the earliest phases of PACAP provocation. These results suggest that sumatriptan prevents PACAP38-induced migraine by modulation of nociceptive transmission within the trigeminovascular system.Trial Registration: ClinicalTrials.gov (NCT03881644).

Pharmacological treatment of migraine: CGRP and 5-HT beyond the triptans

Migraine is a highly disabling neurovascular disorder characterized by a severe headache (associated with nausea, photophobia and/or phonophobia), and trigeminovascular system activation involving the release of calcitonin-gene related peptide (CGRP). Novel anti-migraine drugs target CGRP signaling through either stimulation of 5-HT1F receptors on trigeminovascular nerves (resulting in inhibition of CGRP release) or direct blockade of CGRP or its receptor. Lasmiditan is a highly selective 5-HT1F receptor agonist and, unlike the triptans, is devoid of vasoconstrictive properties, allowing its use in patients with cardiovascular risk. Since lasmiditan can actively penetrate the blood-brain barrier, central therapeutic as well as side effects mediated by 5-HT1F receptor activation should be further investigated. Other novel anti-migraine drugs target CGRP signaling directly. This neuropeptide can be targeted by the monoclonal antibodies eptinezumab, fremanezumab and galcanezumab, or by CGRP-neutralizing L-aptamers called Spiegelmers. The CGRP receptor can be targeted by the monoclonal antibody erenumab, or by small-molecule antagonists called gepants. Currently, rimegepant and ubrogepant have been developed for acute migraine treatment, while atogepant is studied for migraine prophylaxis. Of these drugs targeting CGRP signaling directly, eptinezumab, erenumab, fremanezumab, galcanezumab, rimegepant and ubrogepant have been approved for clinical use, while atogepant is in the last stage before approval. Although all of these drugs seem highly promising for migraine treatment, their safety should be investigated in the long-term. Moreover, the exact mechanism(s) of action of these drugs need to be elucidated further, to increase both safety and efficacy and to increase the number of responders to the different treatments, so that all migraine patients can satisfactorily be treated.

Lasmiditan mechanism of action - review of a selective 5-HT1F agonist

Migraine is a leading cause of disability worldwide, but it is still underdiagnosed and undertreated. Research on the pathophysiology of this neurological disease led to the discovery that calcitonin gene-related peptide (CGRP) is a key neuropeptide involved in pain signaling during a migraine attack. CGRP-mediated neuronal sensitization and glutamate-based second- and third-order neuronal signaling may be an important component involved in migraine pain. The activation of several serotonergic receptor subtypes can block the release of CGRP, other neuropeptides, and neurotransmitters, and can relieve the symptoms of migraine. Triptans were the first therapeutics developed for the treatment of migraine, working through serotonin 5-HT1B/1D receptors. The discovery that the serotonin 1F (5-HT1F) receptor was expressed in the human trigeminal ganglion suggested that this receptor subtype may have a role in the treatment of migraine. The 5-HT1F receptor is found on terminals and cell bodies of trigeminal ganglion neurons and can modulate the release of CGRP from these nerves. Unlike 5-HT1B receptors, the activation of 5-HT1F receptors does not cause vasoconstriction.The potency of different serotonergic agonists towards 5-HT1F was correlated in an animal model of migraine (dural plasma protein extravasation model) leading to the development of lasmiditan. Lasmiditan is a newly approved acute treatment for migraine in the United States and is a lipophilic, highly selective 5-HT1F agonist that can cross the blood-brain barrier and act at peripheral nervous system (PNS) and central nervous system (CNS) sites.Lasmiditan activation of CNS-located 5-HT1F receptors (e.g., in the trigeminal nucleus caudalis) could potentially block the release of CGRP and the neurotransmitter glutamate, thus preventing and possibly reversing the development of central sensitization. Activation of 5-HT1F receptors in the thalamus can block secondary central sensitization of this region, which is associated with progression of migraine and extracephalic cutaneous allodynia. The 5-HT1F receptors are also elements of descending pain modulation, presenting another site where lasmiditan may alleviate migraine. There is emerging evidence that mitochondrial dysfunction might be implicated in the pathophysiology of migraine, and that 5-HT1F receptors can promote mitochondrial biogenesis. While the exact mechanism is unknown, evidence suggests that lasmiditan can alleviate migraine through 5-HT1F agonist activity that leads to inhibition of neuropeptide and neurotransmitter release and inhibition of PNS trigeminovascular and CNS pain signaling pathways.

Volume of the rectus capitis posterior minor muscle in migraine patients: a cross-sectional structural MRI study

Background

Neck pain in migraine patients is very prevalent between and during migraine attacks, but the underlying mechanism behind neck pain in migraine is unknown. The neck muscle rectus capitis posterior minor muscle (RCPmi) may be important since it is connected to the occipital dura mater. In this study, we examined the RCPmi volume in migraine patients and compared with controls.

Methods

We conducted a cross-sectional MRI study examining muscle volume in 40 episodic migraine patients and 40 controls in preexisting images from prior studies. Three-dimensional T1 weighted sequences were collected with a 3.0 T MRI Scanner. The volume of RCPmi was examined by manually tracing the muscle circumference with Horos medical image viewer. The observer was blinded to participant information. No information regarding neck pain status during or between migraine attacks were available.

Results

The mean RCPmi volume was 1.22cm³ in migraine patients and 1.17cm³ in controls (p = 0.549). We found no differences in RCPmi volume on the pain side vs. the non-pain side (p = 0.237) in patients with unilateral migraine. There were no association between the muscle volume and years with migraine, headache or migraine frequency, age or BMI.

Conclusions

We found no difference in RCPmi volume between migraine patients and controls, suggesting no structural RCPmi pathology in migraine.

From transformation to chronification of migraine: pathophysiological and clinical aspects

Chronic migraine is a neurological disorder characterized by 15 or more headache days per month of which at least 8 days show typical migraine features. The process that describes the development from episodic migraine into chronic migraine is commonly referred to as migraine transformation or chronification. Ample studies have attempted to identify factors associated with migraine transformation from different perspectives. Understanding CM as a pathological brain state with trigeminovascular participation where biological changes occur, we have completed a comprehensive review on the clinical, epidemiological, genetic, molecular, structural, functional, physiological and preclinical evidence available.

Plasma Glucose Levels Increase During Spontaneous Attacks of Migraine With and Without Aura

OBJECTIVE

To investigate plasma glucose changes during the ictal state of migraine compared to the interictal state.

BACKGROUND

Previous studies suggest abnormal glucose metabolism in migraine patients during and outside of attacks. It is not known if plasma glucose levels change during spontaneous migraine attacks.

METHODS

Plasma glucose levels were measured during and outside of spontaneous migraine attacks with and without aura. Plasma glucose values were corrected for diurnal variation of plasma glucose by subtracting the difference between the moving average (intervals of 2 hours) and overall mean from the plasma glucose values.

RESULTS

This was a sub-study of a larger study conducted at Rigshospitalet Glostrup in the Capital Region of Denmark. Thirty-one patients (24 F, 7 M, 13 with aura, 18 without aura) were included in the study. Mean time from attack onset to blood sampling was 7.6 hours. Mean pain at the time of investigation was 6 on a 0-10 verbal rating scale. Plasma glucose was higher ictally compared to the interictal phase (interictal mean: 88.63 mg/dL, SD 11.70 mg/dL; ictal mean: 98.83 mg/dL, SD 13.16 mg/dL, difference 10.20 mg/dL, 95% CI = [4.30; 16.10]), P = .0014). The ictal increase was highest in patients investigated early during attacks and decreased linearly with time from onset of migraine (-1.57 mg/dL/hour from onset of attack, P = .020). The attack-related increase in blood glucose was not affected by pain intensity or presence of aura symptoms.

CONCLUSIONS

We demonstrated higher plasma glucose values during spontaneous migraine attacks, independent of the presence of aura symptoms and not related to pain intensity, peaking in the early phase of attacks. Additional studies are necessary to confirm our findings and explore the possible underlying mechanisms.

Mechanisms of migraine as a chronic evolutive condition

Understanding the mechanisms of migraine remains challenging as migraine is not a static disorder, and even in its episodic form migraine remains an "evolutive" chronic condition. Considerable progress has been made in elucidating the pathophysiological mechanisms of migraine, associated genetic factors that may influence susceptibility to the disease, and functional and anatomical changes during the progression of a migraine attack or the transformation of episodic to chronic migraine. Migraine is a life span neurological disorder that follows an evolutive age-dependent change in its prevalence and even clinical presentations. As a disorder, migraine involves recurrent intense head pain and associated unpleasant symptoms. Migraine attacks evolve over different phases with specific neural mechanisms and symptoms being involved during each phase. In some patients, migraine can be transformed into a chronic form with daily or almost daily headaches. The mechanisms behind this evolutive process remain unknown, but genetic and epigenetic factors, inflammatory processes and central sensitization may play an important role.