Spreading depression as a preclinical model of migraine

A comprehensive exploration of astrocytes in migraine: a bibliometric and visual analysis

BACKGROUND

Migraine, as a prevalent neurologic disorder, involves intricate and yet incompletely elucidated pathophysiological mechanisms. A plethora of research findings underscores the pivotal role played by astrocytes in the progression of migraines. In order to elucidate the current advances and directions in research pertaining to astrocytes in migraines, we conducted bibliometric analysis of relevant literature and visualized the results. Subsequently, we expound upon these findings to contribute to the evolving understanding of the role of astrocytes in migraine pathophysiology.

METHODS

On November 21, 2023, we conducted a search on Web of Science (WOS), restricting the document type to articles or reviews and language to English. Following a meticulous selection process involving three researchers, we identified the literature to be included in our analysis. Subsequently, we employed Microsoft Office Excel programs, R, VOSviewer, Scimago Graphica, and CiteSpace software to conduct visualization analysis of basic information and trends regarding journals, countries/regions, and influential authors, institutions, keywords, and papers.

RESULTS

As of November 21, 2023, relevant literature has been published in 71 journals across 27 countries/regions. This corpus comprises contributions from 576 authors affiliated with 220 institutions, encompassing 865 keywords and referencing 6065 scholarly articles. CEPHALALGIA stands out as the most influential journal in this field, while authors PIETROBON D and DALKARA T have significant impact. The United States is highly influential, with CNR and UNIV PADUA emerging as highly influential institutions. The predominant category is Neurosciences.

CONCLUSIONS

Future investigators may continue to focus on migraines with aura, familial hemiplegic migraine (FHM), and the crucial calcitonin gene-related peptide (CGRP) system. Employing advanced observational techniques, such as imaging, researchers should pay attention to cellular and tissue structures, such as microglia and the trigeminal ganglion, as well as mechanisms involving inflammation and central sensitization. Moreover, animal models are paramount in obtaining high-quality evidence.

A rare case of lupus cerebritis presenting as ictal epileptic headache: A case report

Ictal epileptic headache, characterized by headache as the sole symptom of a seizure attack, is a rare condition. In this case report, we present a 52-year-old female with a history of systemic lupus erythematosus who sought medical attention at the headache clinic due to a new type of headache. The headache was described as an intense painful wave followed by a dull headache, without autonomic symptoms or migrainous features. Magnetic resonance imaging revealed an enhancing lesion in the left hippocampus in addition to two other lesions in the corpus callosum and left parieto-occipital lobe. Electroencephalography during the headache episodes showed epileptic discharges originating from the left fronto-temporal region. The patient was initiated on levetiracetam, which resulted in the resolution of both the epileptic discharges and the headaches. This case underscores the significance of considering ictal epileptic headache as a potential secondary cause for headaches, particularly in patients with underlying conditions that may predispose them to epilepsy, such as systemic lupus erythematosus.

Ketamine-induced prevention of SD-associated late infarct progression in experimental ischemia

Spreading depolarizations (SDs) occur frequently in patients with malignant hemispheric stroke. In animal-based experiments, SDs have been shown to cause secondary neuronal damage and infarct expansion during the initial period of infarct progression. In contrast, the influence of SDs during the delayed period is not well characterized yet. Here, we analyzed the impact of SDs in the delayed phase after cerebral ischemia and the potential protective effect of ketamine. Focal ischemia was induced by distal occlusion of the left middle cerebral artery in C57BL6/J mice. 24 h after occlusion, SDs were measured using electrocorticography and laser-speckle imaging in three different study groups: control group without SD induction, SD induction with potassium chloride, and SD induction with potassium chloride and ketamine administration. Infarct progression was evaluated by sequential MRI scans. 24 h after occlusion, we observed spontaneous SDs with a rate of 0.33 SDs/hour which increased during potassium chloride application (3.37 SDs/hour). The analysis of the neurovascular coupling revealed prolonged hypoemic and hyperemic responses in this group. Stroke volume increased even 24 h after stroke onset in the SD-group. Ketamine treatment caused a lesser pronounced hypoemic response and prevented infarct growth in the delayed phase after experimental ischemia. Induction of SDs with potassium chloride was significantly associated with stroke progression even 24 h after stroke onset. Therefore, SD might be a significant contributor to delayed stroke progression. Ketamine might be a possible drug to prevent SD-induced delayed stroke progression.

Potential of focal cortical dysplasia in migraine pathogenesis

Focal cortical dysplasias are abnormalities of the cerebral cortex associated with an elevated risk of neurological disturbances. Cortical spreading depolarization/depression is a correlate of migraine aura/headache and a trigger of migraine pain mechanisms. However, cortical spreading depolarization/depression is associated with cortical structural changes, which can be classified as transient focal cortical dysplasias. Migraine is reported to be associated with changes in various brain structures, including malformations and lesions in the cortex. Such malformations may be related to focal cortical dysplasias, which may play a role in migraine pathogenesis. Results obtained so far suggest that focal cortical dysplasias may belong to the causes and consequences of migraine. Certain focal cortical dysplasias may lower the threshold of cortical excitability and facilitate the action of migraine triggers. Migraine prevalence in epileptic patients is higher than in the general population, and focal cortical dysplasias are an established element of epilepsy pathogenesis. In this narrative/hypothesis review, we present mainly information on cortical structural changes in migraine, but studies on structural alterations in deep white matter and other brain regions are also presented. We develop the hypothesis that focal cortical dysplasias may be causally associated with migraine and link pathogeneses of migraine and epilepsy.

Migraine and the microbiota. Can probiotics be beneficial in its prevention? - a narrative review

Migraine is a recurrent disease of the central nervous system that affects an increasing number of people worldwide causing a continuous increase in the costs of treatment. The mechanisms underlying migraine are still unclear but recent reports show that people with migraine may have an altered composition of the intestinal microbiota. It is well established that the gut-brain axis is involved in many neurological diseases, and probiotic supplementation may be an interesting treatment option for these conditions. This review collects data on the gastrointestinal and oral microbiota in people suffering from migraine and the use of probiotics as a novel therapeutic approach in its treatment.

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.

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.

Spatially resolved metabolomics and isotope tracing reveal dynamic metabolic responses of dentate granule neurons with acute stimulation

Neuronal activity creates an intense energy demand that must be met by rapid metabolic responses. To investigate metabolic adaptations in the neuron-enriched dentate granule cell (DGC) layer within its native tissue environment, we employed murine acute hippocampal brain slices, coupled with fast metabolite preservation and followed by mass spectrometry (MS) imaging, to generate spatially resolved metabolomics and isotope-tracing data. Here we show that membrane depolarization induces broad metabolic changes, including increased glycolytic activity in DGCs. Increased glucose metabolism in response to stimulation is accompanied by mobilization of endogenous inosine into pentose phosphates via the action of purine nucleotide phosphorylase (PNP). The PNP reaction is an integral part of the neuronal response to stimulation, because inhibition of PNP leaves DGCs energetically impaired during recovery from strong activation. Performing MS imaging on brain slices bridges the gap between live-cell physiology and the deep chemical analysis enabled by MS.

Molecular mechanisms of hormones implicated in migraine and the translational implication for transgender patients

Migraine is a primary headache disorder recognized by the World Health Organization as one of the most poorly understood and debilitating neurological conditions impacting global disability. Chronic pain disorders are more frequently diagnosed among cisgender women than men, suggesting that female sex hormones could be responsible for mediating chronic pain, including migraine and/or that androgens can be protective. This review discusses the major gonadal hormones, estrogens, progesterone, and testosterone in the context of molecular mechanisms by which they play a role in migraine pathophysiology. In addition, the literature to date describing roles of minor sex hormones including prolactin, luteinizing hormone, follicular stimulating hormone, and gonadotropin releasing hormone in migraine are presented. Because transgender and gender non-conforming (trans*) individuals are an underserved patient population in which gender-affirming sex hormone replacement therapy (HRT) is often medically necessary to align biological sex with gender identity, results from cisgender patient populations are discussed in the context of these major and minor sex hormones on migraine incidence and management in trans* patients.

Retinal microvasculature features in patients with migraine: a systematic review and meta-analysis

Background

Migraine is a central nervous system disorder involving neuronal and vascular factors. The brain has a close anatomical relationship with retinal vessels and similar regulatory processes, and the retinal vascular system is the only in vivo vessel that can be directly visualized, while optical coherence tomography angiography (OCTA) is an advanced retinal vascular imaging technique. In this study, OCTA was used to study the retinal vascular density (VD) and foveal avascular zone (FAZ) in migraine patients, which provided a theoretical basis for its use as a candidate for rapid and non-invasive diagnosis of migraine.

Methods

Published studies comparing retinal microvascular profiles between migraine patients and healthy controls were obtained by a comprehensive search of electronic databases. Nine studies were finally included, including 775 eyes (migraine group: 444 eyes, control group: 331 eyes). Pooled effect sizes were presented as standardized mean differences (SMDs) and 95% confidence intervals (CIs). Statistical analysis was performed using Review Manager software (version 5.30).

Results

The combined results revealed that the superficial and deep macular whole enface VD (MWEVD) (superficial VD: SMD = -0.30, P = 0.0001; deep VD: SMD = -0.61, P = 0.02), superficial foveal VD (FVD) (SMD = -0.42, P = 0.03), deep parafoveal VD (PFVD) (SMD = -0.31, P = 0.002), and peripapillary VD (PVD) (SMD = -0.49, P = 0.002) were significantly reduced in migraine patients compared with healthy people. However, there was a significant increase in the area of the FAZ in migraine patients (SMD = 0.56, P < 0.0001).

Conclusion

Migraine patients are prone to retinal microcirculation disorders, such as decreased blood vessel density and increased avascular area in the fovea. This provides a theoretical basis for OCTA as a candidate for rapid, non-invasive diagnosis of migraine.

Spatially resolved metabolomics and isotope tracing reveal dynamic metabolic responses of dentate granule neurons with acute stimulation

Neuronal activity creates an intense energy demand that must be met by rapid metabolic responses. To investigate metabolic adaptations in the neuron-enriched dentate granule cell (DGC) layer within its native tissue environment, we employed murine acute hippocampal brain slices coupled with fast metabolite preservation, followed by mass spectrometry imaging (MALDI-MSI) to generate spatially resolved metabolomics and isotope tracing data. Here we show that membrane depolarization induces broad metabolic changes, including increased glycolytic activity in DGCs. Increased glucose metabolism in response to stimulation is accompanied by mobilization of endogenous inosine into pentose phosphates, via the action of purine nucleotide phosphorylase (PNP). The PNP reaction is an integral part of the neuronal response to stimulation, as inhibiting PNP leaves DGCs energetically impaired during recovery from strong activation. Performing MSI on brain slices bridges the gap between live cell physiology and the deep chemical analysis enabled by mass spectrometry.

The Current of Consciousness: Neural Correlates and Clinical Aspects

PURPOSE OF REVIEW

In this review, we summarize the current understanding of consciousness including its neuroanatomic basis. We discuss major theories of consciousness, physical exam-based and electroencephalographic metrics used to stratify levels of consciousness, and tools used to shed light on the neural correlates of the conscious experience. Lastly, we review an expanded category of 'disorders of consciousness,' which includes disorders that impact either the level or experience of consciousness.

RECENT FINDINGS

Recent studies have revealed many of the requisite EEG, ERP, and fMRI signals to predict aspects of the conscious experience. Neurological disorders that disrupt the reticular activating system can affect the level of consciousness, whereas cortical disorders from seizures and migraines to strokes and dementia may disrupt phenomenal consciousness. The recently introduced memory theory of consciousness provides a new explanation of phenomenal consciousness that may explain better than prior theories both experimental studies and the neurologist's clinical experience. Although the complete neurobiological basis of consciousness remains a mystery, recent advances have improved our understanding of the physiology underlying level of consciousness and phenomenal consciousness.

A systematic literature review on the role of glial cells in the pathomechanisms of migraine

Background

The pathomechanisms underlying migraine are intricate and remain largely unclear. Initially regarded as a neuronal disorder, migraine research primarily concentrated on understanding the pathophysiological changes within neurons. However, recent advances have revealed the significant involvement of neuroinflammation and the neuro-glio-vascular interplay in migraine pathogenesis.

Methods

A systematic search was conducted in PubMed, Scopus, and Web of Science databases from their inception until November 2022. The retrieved results underwent a screening process based on title and abstract, and the full texts of the remaining papers were thoroughly assessed for eligibility. Only studies that met the predetermined inclusion criteria were included in the review.

Results

Fifty-nine studies, consisting of 6 human studies and 53 animal studies, met the inclusion criteria. Among the 6 human studies, 2 focused on genetic analyses, while the remaining studies employed functional imaging, serum analyses and clinical trials. Regarding the 53 animal studies investigating glial cells in migraine, 19 of them explored the role of satellite glial cells and/or Schwann cells in the trigeminal ganglion and/or trigeminal nerve. Additionally, 17 studies highlighted the significance of microglia and/or astrocytes in the trigeminal nucleus caudalis, particularly in relation to central sensitization during migraine chronification. Furthermore, 17 studies examined the involvement of astrocytes and/or microglia in the cortex.

Conclusion

Glial cells, including astrocytes, microglia, satellite glial cells and Schwann cells in the central and peripheral nervous system, participate both in the development as well as chronic progression of migraine in disease-associated regions such as the trigeminovascular system, trigeminal nucleus caudalis and cortex, among other brain regions.

The Epigenetics of Migraine

Migraine is a complex neurological disorder and a major cause of disability. A wide range of different drug classes such as triptans, antidepressants, anticonvulsants, analgesics, and beta-blockers are used in acute and preventive migraine therapy. Despite a considerable progress in the development of novel and targeted therapeutic interventions during recent years, e.g., drugs that inhibit the calcitonin gene-related peptide (CGRP) pathway, therapy success rates are still unsatisfactory. The diversity of drug classes used in migraine therapy partly reflects the limited perception of migraine pathophysiology. Genetics seems to explain only to a minor extent the susceptibility and pathophysiological aspects of migraine. While the role of genetics in migraine has been extensively studied in the past, the interest in studying the role of gene regulatory mechanisms in migraine pathophysiology is recently evolving. A better understanding of the causes and consequences of migraine-associated epigenetic changes could help to better understand migraine risk, pathogenesis, development, course, diagnosis, and prognosis. Additionally, it could be a promising avenue to discover new therapeutic targets for migraine treatment and monitoring. In this review, we summarize the state of the art regarding epigenetic findings in relation to migraine pathogenesis and potential therapeutic targets, with a focus on DNA methylation, histone acetylation, and microRNA-dependent regulation. Several genes and their methylation patterns such as CALCA (migraine symptoms and age of migraine onset), RAMP1, NPTX2, and SH2D5 (migraine chronification) and microRNA molecules such as miR-34a-5p and miR-382-5p (treatment response) seem especially worthy of further study regarding their role in migraine pathogenesis, course, and therapy. Additionally, changes in genes including COMT, GIT2, ZNF234, and SOCS1 have been linked to migraine progression to medication overuse headache (MOH), and several microRNA molecules such as let-7a-5p, let-7b-5p, let-7f-5p, miR-155, miR-126, let-7g, hsa-miR-34a-5p, hsa-miR-375, miR-181a, let-7b, miR-22, and miR-155-5p have been implicated with migraine pathophysiology. Epigenetic changes could be a potential tool for a better understanding of migraine pathophysiology and the identification of new therapeutic possibilities. However, further studies with larger sample sizes are needed to verify these early findings and to be able to establish epigenetic targets as disease predictors or therapeutic targets.

The NMDA receptor antagonists memantine and ketamine as anti-migraine agents

Migraine is a debilitating disorder affecting females more frequently than males. There is some evidence that drugs targeting glutamate receptors: memantine and ketamine might be beneficial in the therapy of this entity. Therefore, the purpose of this work is to present NMDA receptor antagonists, memantine and ketamine, as potential anti-migraine agents. We searched PubMed/MEDLINE, Embase, and clinical trials submitted to ClinicalTrials.gov to find publications describing eligible trials published between database inception and December 31, 2021. This comprehensive literature review summarizes data on the use of the NMDA receptor antagonists memantine and ketamine in the pharmacotherapy of migraine. Results from 20 previous and recent preclinical experiments are discussed and correlated with 19 clinical trials (including case series, open-label, and randomized placebo-controlled trials). For the purposes of this review, the authors hypothesized that the propagation of SD is a major mechanism in the pathophysiology of migraine. In several animal studies and in vitro studies, memantine and ketamine inhibited or reduced propagation of the SD. In addition, the results of clinical trials suggest that memantine or ketamine may be an effective treatment option for migraine. However, most studies on these agents lack control group. Although further clinical trials are needed, the results suggest that ketamine or memantine may be promising molecules for the treatment of severe migraine. Particular attention should be paid to people who have a treatment-resistant form of migraine with aura or have exhausted existing treatment options. For them, the drugs under discussion could represent an interesting alternative in the future.

Activity-Dependent Fluctuations in Interstitial [K+]: Investigations Using Ion-Sensitive Microelectrodes

In the course of action potential firing, all axons and neurons release K⁺ from the intra- cellular compartment into the interstitial space to counteract the depolarizing effect of Na⁺ influx, which restores the resting membrane potential. This efflux of K⁺ from axons results in K⁺ accumulation in the interstitial space, causing depolarization of the K⁺ reversal potential (E_K), which can prevent subsequent action potentials. To ensure optimal neuronal function, the K⁺ is buffered by astrocytes, an energy-dependent process, which acts as a sink for interstitial K⁺, absorbing it at regions of high concentration and distributing it through the syncytium for release in distant regions. Pathological processes in which energy production is compromised, such as anoxia, ischemia, epilepsy and spreading depression, can lead to excessive interstitial K⁺ accumulation, disrupting sensitive trans-membrane ion gradients and attenuating neuronal activity. The changes that occur in interstitial [K⁺] resulting from both physiological and pathological processes can be monitored accurately in real time using K⁺-sensitive microelectrodes, an invaluable tool in electrophysiological studies.

Migraine aura-like episodes following sclerotherapy for varicose veins of the lower extremities-A systematic review

OBJECTIVE

This systematic review provides a summary and evaluation of cases of migraine aura-like episodes elicited by sclerotherapy of veins of the lower extremities and discusses possible underlying mechanisms.

BACKGROUND

Sclerotherapy is a commonly used treatment for varicose veins. Symptoms resembling migraine aura have been reported during and following sclerotherapy of the lower extremities, suggesting that sclerotherapy may elicit migraine aura.

METHODS

We searched PubMed for articles reporting neurological complications that were transient and fully reversible following sclerotherapy treatment for varicose veins in the lower limbs. There were no restrictions regarding article language or publication date. Only original studies and case reports were included. Two authors independently reviewed included articles in detail. Data were extracted from each article, including details on symptoms, previous migraine history, sclerotherapy method, and the presence of a right-to-left cardiac shunt in patients. We evaluated whether episodes fulfilled modified International Classification of Headache Disorders, 3rd edition, criteria for 1.2 Migraine with aura or 1.5.2 Probable migraine with aura.

RESULTS

The search yielded 777 articles, 28 of which were included. Twenty-six articles reported 119 episodes of transient neurological symptoms in 34,500 sclerotherapy sessions. Two additional articles reported six episodes of transient neurological symptoms with no specification of the number of sessions. Of the 125 episodes, 119 involved transient visual disturbances, and eight met the modified criteria for Probable migraine with aura. In most episodes (98%), clinical information was insufficient to determine if the criteria were fulfilled.

CONCLUSIONS

Symptoms that are clinically indistinguishable from migraine with aura attacks may occur following sclerotherapy, although this likely is rare. Microembolization through a right-to-left shunt triggering cortical spreading depolarization is a possible mechanism. Our findings are limited by infrequent specific assessments for neurological complications and a low level of detail in the description of symptoms in the available literature. Future prospective studies are needed to determine this phenomenon's incidence and underlying mechanisms.

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.

ERP evidence of heightened attentional response to visual stimuli in migraine headache disorders

New findings from migraine studies have indicated that this common headache disorder is associated with anomalies in attentional processing. In tandem with the previous explorations, this study will provide evidence to show that visual attention is impacted by migraine headache disorders. 43 individuals were initially recruited in the migraine group and 33 people with non-migraine headache disorders were in the control group. The event-related potentials (ERP) of the participants were calculated using data from a visual oddball paradigm task. By analyzing the N200 and P300 ERP components, migraineurs, as compared to controls, had an exaggerated oddball response showing increased amplitude in N200 and P300 difference scores for the oddball vs. standard, while the latencies of the two components remained the same in the migraine and control groups. We then looked at two classifications of migraine with and without aura compared to non-migraine controls. One-Way ANOVA analysis of the two migraine groups and the non-migraine control group showed that the different level of N200 and P300 amplitude mean scores was greater between migraineurs without aura and the control group while these components’ latency remained the same relatively in the three groups. Our results give more neurophysiological support that people with migraine headaches have altered processing of visual attention.

Anatomy and Physiology of Headache

Headache disorders can produce recurrent, incapacitating pain. Migraine and cluster headache are notable for their ability to produce significant disability. The anatomy and physiology of headache disorders is fundamental to evolving treatment approaches and research priorities. Key concepts in headache mechanisms include activation and sensitization of trigeminovascular, brainstem, thalamic, and hypothalamic neurons; modulation of cortical brain regions; and activation of descending pain circuits. This review will examine the relevant anatomy of the trigeminal, brainstem, subcortical, and cortical brain regions and concepts related to the pathophysiology of migraine and cluster headache disorders.

Effectiveness of Transcranial Direct Current Stimulation and Monoclonal Antibodies Acting on the CGRP as a Combined Treatment for Migraine (TACTIC): Protocol for a Randomized, Double-Blind, Sham-Controlled Trial

Background

Migraine is a recurrent headache disorder that has a still unclear pathophysiology, involving several circuits of both the central and peripheral nervous system. Monoclonal antibodies acting on the calcitonin gene-related (CGRP) pathway (CGRP-MAbs) are the first drugs specifically designed for migraine; those drugs act peripherally on the trigeminal ganglion without entering the blood-brain barrier. Conversely, neuromodulation techniques such as transcranial direct current stimulation (tDCS) act centrally by increasing or decreasing the neuronal firing rate of brain cortical areas. The aim of the study will be to evaluate whether tDCS, in addition to CGRP-MAbs, is an effective add-on treatment in reducing headache frequency, intensity and acute medication use in patients with migraine. To demonstrate the biological effects of tDCS, the electroencephalographic (EEG) power changes after tDCS will be assessed.

Methods

We will include patients with migraine on treatment with CGRP-MAbs and reporting ≥8 monthly migraine days. During a prospective 28-day baseline period, patients will fill in a headache diary and questionnaires to evaluate migraine-related disability, anxiety and depressive symptoms, sleep quality, and health-related quality of life. Subjects will be randomly assigned in a 1:1 ratio to active or sham tDCS. The stimulation protocol will consist in five daily sessions, the cathodes will be applied bilaterally above the occipital areas, with the reference anode electrodes positioned above the primary motor areas. Before the first, and immediately after the last stimulation session, patients will perform a 10-min resting EEG recording. During a 28-day follow-up period following tDCS, patients will have to fill in a headache diary and questionnaires identical to those of the baseline period.

Discussion

This trial will evaluate the efficacy of an add-on treatment acting on the brain in patients with migraine, who are already treated with peripherally acting drugs, showing how tDCS acts in restoring the dysfunctional brain networks typical of the migraine patient.

Clinical Trial Registration

NCT05161871.

Hyperhomocysteinemia Increases Cortical Excitability and Aggravates Mechanical Hyperalgesia and Anxiety in a Nitroglycerine-Induced Migraine Model in Rats

Homocysteine is a sulfur-containing endogenous amino acid leading to neurotoxic effects at high concentrations. Population studies suggest an association between plasma homocysteine levels and the risk of migraine headaches. The aim of this study was to analyze the sensitivity of rats with prenatal hyperhomocysteinemia (hHCY) in respect of the development of behavioral correlates of headache and spreading cortical depolarization (CSD) in a migraine model induced by the administration of the nitric oxide (NO) donor nitroglycerin. Animals with hHCY were characterized by migraine-related symptoms such as mechanical hyperalgesia, high-level anxiety, photophobia, as well as an enhanced level of neuronal activity in the somatosensory cortex along with a lower threshold of CSD generation. Likewise, acute or chronic intermittent administration of nitroglycerin also induced the development of mechanical allodynia, photophobia and anxiety in control groups. However, these symptoms were more pronounced in rats with hHCY. Unlike hHCY, nitroglycerin administration did not affect the threshold of CSD generation, but like hHCY, increased the background neuronal activity in layers 2/3 and 4 of the cerebral cortex. The latter was more pronounced in animals with hHCY. Thus, the migraine profile associated with hHCY can be further exaggerated in conditions with enhanced levels of migraine triggering the gaseous transmitter NO. Our data are consistent with the view that high levels of plasma homocysteine can act as a risk factor for the development of migraine.

Genome-wide analysis identified novel susceptible genes of restless legs syndrome in migraineurs

Background

Restless legs syndrome is a highly prevalent comorbidity of migraine; however, its genetic contributions remain unclear.

Objectives

To identify the genetic variants of restless legs syndrome in migraineurs and to investigate their potential pathogenic roles.

Methods

We conducted a two-stage genome-wide association study (GWAS) to identify susceptible genes for restless legs syndrome in 1,647 patients with migraine, including 264 with and 1,383 without restless legs syndrome, and also validated the association of lead variants in normal controls unaffected with restless legs syndrome (n = 1,053). We used morpholino translational knockdown (morphants), CRISPR/dCas9 transcriptional knockdown, transient CRISPR/Cas9 knockout (crispants) and gene rescue in one-cell stage embryos of zebrafish to study the function of the identified genes.

Results

We identified two novel susceptibility loci rs6021854 (in VSTM2L) and rs79823654 (in CCDC141) to be associated with restless legs syndrome in migraineurs, which remained significant when compared to normal controls. Two different morpholinos targeting vstm2l and ccdc141 in zebrafish demonstrated behavioural and cytochemical phenotypes relevant to restless legs syndrome, including hyperkinetic movements of pectoral fins and decreased number in dopaminergic amacrine cells. These phenotypes could be partially reversed with gene rescue, suggesting the specificity of translational knockdown. Transcriptional CRISPR/dCas9 knockdown and transient CRISPR/Cas9 knockout of vstm2l and ccdc141 replicated the findings observed in translationally knocked-down morphants.

Conclusions

Our GWAS and functional analysis suggest VSTM2L and CCDC141 are highly relevant to the pathogenesis of restless legs syndrome in migraineurs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01409-9.

Full-bandwidth electrophysiology of seizures and epileptiform activity enabled by flexible graphene microtransistor depth neural probes

Mapping the entire frequency bandwidth of brain electrophysiological signals is of paramount importance for understanding physiological and pathological states. The ability to record simultaneously DC-shifts, infraslow oscillations (<0.1 Hz), typical local field potentials (0.1-80 Hz) and higher frequencies (80-600 Hz) using the same recording site would particularly benefit preclinical epilepsy research and could provide clinical biomarkers for improved seizure onset zone delineation. However, commonly used metal microelectrode technology suffers from instabilities that hamper the high fidelity of DC-coupled recordings, which are needed to access signals of very low frequency. In this study we used flexible graphene depth neural probes (gDNPs), consisting of a linear array of graphene microtransistors, to concurrently record DC-shifts and high-frequency neuronal activity in awake rodents. We show here that gDNPs can reliably record and map with high spatial resolution seizures, pre-ictal DC-shifts and seizure-associated spreading depolarizations together with higher frequencies through the cortical laminae to the hippocampus in a mouse model of chemically induced seizures. Moreover, we demonstrate the functionality of chronically implanted devices over 10 weeks by recording with high fidelity spontaneous spike-wave discharges and associated infraslow oscillations in a rat model of absence epilepsy. Altogether, our work highlights the suitability of this technology for in vivo electrophysiology research, and in particular epilepsy research, by allowing stable and chronic DC-coupled recordings.

Cortical Spreading Depolarizations in a Mouse Model of Subarachnoid Hemorrhage

BACKGROUND

Cortical spreading depolarizations (CSDs) are associated with worse outcomes in patients with aneurysmal subarachnoid hemorrhage (SAH). Animal models are required to assess whether CSDs can worsen outcomes or are an epiphenomenon; however, little is known about the presence of CSDs in existing animal models. Therefore, we designed a study to determine whether CSDs occur in a mouse model of SAH.

METHODS

A total of 36 mice were included in the study. We used the anterior prechiasmatic injection model of SAH under isoflurane anesthesia. A needle was inserted through the mouse olfactory bulb with the point terminating at the base of the skull, and arterial blood or saline (100 µl) was injected over 10 s. Changes in cerebral blood volume over the entire dorsal cortical surface were assessed with optical intrinsic signal imaging for 5 min following needle insertion.

RESULTS

CSDs occurred in 100% of mice in the hemisphere ipsilateral to olfactory bulb needle insertion (CSD1). Saline-injected mice had 100% survival (n = 10). Blood-injected mice had 88% survival (n = 23 of 26). A second, delayed, CSD ipsilateral to CSD1 occurred in 31% of blood-injected mice. An increase in the time interval between CSD1 and blood injection was associated with the occurrence of a second CSD in blood-injected mice (mean intervals 26.4 vs. 72.7 s, p < 0.0001, n = 18 and 8). We observed one blood-injected animal with a second CSD in the contralateral hemisphere and observed terminal CSDs in mice that died following SAH injection.

CONCLUSIONS

The prechiasmatic injection model of SAH includes CSDs that occur at the time of needle insertion. The occurrence of subsequent CSDs depends on the timing between CSD1 and blood injection. The mouse prechiasmatic injection model could be considered an SAH plus CSD model of the disease. Further work is needed to determine the effect of multiple CSDs on outcomes following SAH.

Calcitonin gene-related peptide-induced hemodynamic changes in migraine with and without aura

OBJECTIVES

Exogenous calcitonin gene-related peptide (eCGRP) can induce CGRP-induced headaches (CGRP-IH) and aura in migraine with aura (MA). This implies a common pathophysiological mechanism of trigeminovascular sensitization (TVS) in migraine headaches and aura. The aim was to assess hemodynamic changes in cerebral circulation induced by eCGRP. We predicted that cerebral hemodynamic changes may differ between migraine without aura (MO) and MA.

MATERIALS AND METHODS

We included twenty participants with migraine, of whom 15 (75%) had MO, and 5 (25%) had MA. An intravenous infusion of eCGRP was administered. Polymodal recording of mean arterial velocity in MCA (vm MCA) and PCA (vm PCA), end-tidal carbon dioxide partial pressure (Et-CO₂ ), mean arterial pressure (MAP), and heart rate (HR) was employed using transcranial Doppler sonography (TCD). The parameters were determined at different time points with single responses vm MCA_tot , vm PCA_tot , Et-CO_2tot , MAP_tot , and HR_tot .

RESULTS

The CGRP-IH appeared in five participants with MA (100%) and in 11 participants with MO (73.3%) (p = .530). The difference of changes in vm MCA_tot (p = .014) and vm PCA_tot (p = .004) was significant, whereas in Et-CO_2tot (p = .658), MAP_tot (p = .392), and HR_tot (p = .686), it appeared to be non-significant. We found significant associations between vm MCA_tot and MA (p = .023; OR = 0.88; 95%C.I. 0.78-0.98), and vm PCA_tot and MA (p = .018; OR = 0.85; 95%C.I. 0.74-0.97).

CONCLUSIONS

Cerebral hemodynamics differs between MO and MA, indicating a pronounced vasodilatation and TVS in MA, which could induce aura.

TRPA1-Mediated Src Family Kinases Activity Facilitates Cortical Spreading Depression Susceptibility and Trigeminovascular System Sensitization

Transient receptor potential ankyrin 1 (TRPA1) plays a role in migraine and is proposed as a promising target for migraine therapy. However, TRPA1-induced signaling in migraine pathogenesis is poorly understood. In this study, we explored the hypothesis that Src family kinases (SFKs) transmit TRPA1 signaling in regulating cortical spreading depression (CSD), calcitonin gene-related peptide (CGRP) release and neuroinflammation. CSD was monitored in mouse brain slices via intrinsic optical imaging, and in rats using electrophysiology. CGRP level and IL-1β gene expression in mouse trigeminal ganglia (TG) was detected using Enzyme-linked Immunosorbent Assay and Quantitative Polymerase Chain Reaction respectively. The results showed a SFKs activator, pYEEI (EPQY(PO3H2)EEEIPIYL), reversed the reduced cortical susceptibility to CSD by an anti-TRPA1 antibody in mouse brain slices. Additionally, the increased cytosolic phosphorylated SFKs at Y416 induced by CSD in rat ipsilateral cerebral cortices was attenuated by pretreatment of the anti-TRPA1 antibody perfused into contralateral ventricles. In mouse TG, a SFKs inhibitor, saracatinib, restored the CGRP release and IL-1β mRNA level increased by a TRPA1 activator, umbellulone. Moreover, umbellulone promoted SFKs phosphorylation, which was reduced by a PKA inhibitor, PKI (14-22) Amide. These data reveal a novel mechanism of migraine pathogenesis by which TRPA1 transmits signaling to SFKs via PKA facilitating CSD susceptibility and trigeminovascular system sensitization.

Tinnitus and Subjective Hearing Loss are More Common in Migraine: A Cross-Sectional NHANES Analysis

OBJECTIVES

To investigate whether migraine is independently associated with tinnitus and subjective hearing loss (HL) in a large national database.

METHODS

The de-identified 1999 to 2004 National Health and Nutrition Examination Survey database was retrospectively queried for subjects aged 18 to 65. HL and tinnitus were subjectively reported by subjects.

RESULTS

A total of 12,962 subjects (52.9% female) with a mean age of 38.1 ± 14.6 years were included. This consisted of 2,657 (20.5%), 2,344 (18.1%), and 2,582 (19.9%) subjects who had migraine, subjective-HL, and tinnitus, respectively. In patients with tinnitus or subjective-HL, migraine was reported in 35.6% and 24.5%, respectively. Migraineurs were more likely to have subjective-HL (25.0% vs. 16.6%, p < 0.001) and tinnitus (34.6% vs. 16.9%, p < 0.001) compared to the nonmigraineurs. This corresponded to migraine having an odds ratio of 1.5 (95% confidence interval [CI] 1.3-1.7, p < 0.001) and 2.2 (95% CI 2.0-2.4, p < 0.001) for subjective-HL and tinnitus, respectively. After adjusting for confounders, subjective-HL (odds ratio [OR] = 1.2, 95% CI 1.1-1.4, p = 0.003), tinnitus (OR = 2.1, 95% CI 1.9-2.3, p < 0.001), and neck pain (OR = 4.0, 95% CI 3.6-4.5, p < 0.001) were more common in migraineurs. Among migraineurs, a higher proportion of those with tinnitus also had subjective-HL compared to those without tinnitus (40.0% vs. 15.3%, p < 0.001), and a higher proportion of those with subjective-HL also had tinnitus compared to those without HL (58.1% vs. 27.3%, p < 0.001).

CONCLUSIONS

This study suggests an independent association between migraine with subjective-HL and tinnitus. Otologic migraine, which is the effects of migraine on the ear, may be partly responsible for the link between HL, tinnitus, neck pain, and migraine.

Kynurenine Pathway of Tryptophan Metabolism in Migraine and Functional Gastrointestinal Disorders

Migraine, the leading cause of disability in the population aged below 50, is associated with functional gastrointestinal (GI) disorders (FGIDs) such as functional nausea, cyclic vomiting syndrome, and irritable bowel syndrome (IBS). Conversely, changes in intestinal GI transit may cause diarrhea or constipation and are a component of the autonomic symptoms associated with pre- and post-dorsal phases of migraine attack. These mutual relationships provoke a question on a common trigger in migraine and FGIDs. The kynurenine (l-kyn) pathway (KP) is the major route for l-tryptophan (l-Trp) metabolism and transforms l-Trp into several neuroactive compounds. Changes in KP were reported in both migraine and FGIDs. Migraine was largely untreatable, but several drugs approved lately by the FDA, including monoclonal antibodies for calcitonin gene-related peptide (CGRP) and its receptor, create a hope for a breakthrough in migraine treatment. Derivatives of l-kyn were efficient in pain relief with a mechanism including CGRP inhibition. KP products are important ligands to the aryl hydrocarbon receptor (AhR), whose activation is implicated in the pathogenesis of GI and migraine. Toll-like receptors (TLRs) may play a role in migraine and IBS pathogeneses, and KP metabolites detected downstream of TLR activation may be an IBS marker. The TLR4 signaling was observed in initiating and maintaining migraine-like behavior through myeloid differentiation primary response gene 88 (MyD88) in the mouse. The aim of this review is to justify the view that KP modulation may provide common triggers for migraine and FGIDs with the involvement of TLR, AhR, and MyD88 activation.

The eye in migraine: a review of retinal imaging findings in migraine

Migraine is a common headache disorder with neurovascular involvement. Because eyecare practitioners are likely to encounter people with migraine in their everyday practice, it is important to understand how migraine might impact on ocular health. In this narrative review, we provide an update on the latest ophthalmic imaging evidence for retinal involvement in migraine, derived from studies of retinal structure and retinal vascular perfusion using spectral domain and swept source optical coherence tomography (OCT) and OCT angiography. Combined structural OCT evidence from a recent meta-analysis indicates subtle and non-specific thinning of the peripapillary retinal nerve fibre layer (RNFL) in people with migraine, whereas there is little consistent evidence for structural abnormalities of the macular region. Recent advances in OCT angiography technology have also provided an opportunity to visualise microstructural damage and vascular dysregulation in the eyes of people with migraine. However, given that OCT and OCT angiography studies have been exclusively cross-sectional, it is not possible to demonstrate the causal effect of migraine events. Furthermore, the lack of common methodology (different ophthalmic imaging devices and analysis algorithms), and very limited datasets (small samples, heterogenous migraine groups), lead to an inability to make strong conclusions regarding the nature of altered retinal structure and vascular perfusion in migraine. Nevertheless, we discuss the clinical implications of such observations for eyecare practitioners and provide practical advice for the monitoring and management of patients with a history of migraine.

Review and Hypothesis: A Potential Common Link Between Glial Cells, Calcium Changes, Modulation of Synaptic Transmission, Spreading Depression, Migraine, and Epilepsy-H. Front Cell Neurosci 2021;15:693095. [PMID: 34539347 PMCID: PMC8446203 DOI: 10.3389/fncel.2021.693095]

There is significant evidence to support the notion that glial cells can modulate the strength of synaptic connections between nerve cells, and it has further been suggested that alterations in intracellular calcium are likely to play a key role in this process. However, the molecular mechanism(s) by which glial cells modulate neuronal signaling remains contentiously debated. Recent experiments have suggested that alterations in extracellular H+ efflux initiated by extracellular ATP may play a key role in the modulation of synaptic strength by radial glial cells in the retina and astrocytes throughout the brain. ATP-elicited alterations in H+ flux from radial glial cells were first detected from Müller cells enzymatically dissociated from the retina of tiger salamander using self-referencing H+-selective microelectrodes. The ATP-elicited alteration in H+ efflux was further found to be highly evolutionarily conserved, extending to Müller cells isolated from species as diverse as lamprey, skate, rat, mouse, monkey and human. More recently, self-referencing H+-selective electrodes have been used to detect ATP-elicited alterations in H+ efflux around individual mammalian astrocytes from the cortex and hippocampus. Tied to increases in intracellular calcium, these ATP-induced extracellular acidifications are well-positioned to be key mediators of synaptic modulation. In this article, we examine the evidence supporting H+ as a key modulator of neurotransmission, review data showing that extracellular ATP elicits an increase in H+ efflux from glial cells, and describe the potential signal transduction pathways involved in glial cell-mediated H+ efflux. We then examine the potential role that extracellular H+ released by glia might play in regulating synaptic transmission within the vertebrate retina, and then expand the focus to discuss potential roles in spreading depression, migraine, epilepsy, and alterations in brain rhythms, and suggest that alterations in extracellular H+ may be a unifying feature linking these disparate phenomena.

Migraine with Visual aura and the Risk of Stroke- a Narrative Review

OBJECTIVES

Patients with migraine with visual aura (MwvA) often present to eye care providers for evaluation. A thorough ophthalmological history and examination is needed to exclude ophthalmologic disorders. Additionally, it has been increasingly recognized that MwvA is associated with ischemic stroke (IS). The aim of this narrative review is to provide a comprehensive overview of the differential diagnosis of MwvA and its association with IS.

MATERIALS AND METHODS

We conducted a PubMed search using key words including "migraine aura", "visual aura without headache", "late onset migraine accompaniment", "migraine and stroke", "migraine and atrial fibrillation", and "migraine and patent foramen ovale (PFO)". We narratively summarized the main findings of the identified studies in sections including age of onset and frequency of migraine with aura, stroke subtypes, and the role of cardioembolism in the migraine-stroke association.

RESULTS AND CONCLUSION

For women younger than 50 years, MwvA is associated with an increased risk of IS, and the risk further increases in patients who also smoke and use oral contraceptives. Age of onset of MwvA 50 years or greater is associated with IS that occurs in late life. Studies reported that increased frequency of aura is associated with an increased risk of IS in women. MwvA is associated with an increased risk of cardioembolic stroke and a higher incidence of atrial fibrillation compared to migraine without aura. Most studies that assessed the migraine-stroke association were based on patients with MwvA. The risks of stroke associated with other types of migraine aura or aura without headache, as well as such association in men require further investigation. More data is needed to determine the absolute risk of stroke when evaluating MwvA in situations including smoking and low dose estrogen use, new or late onset (>50 years) MwvA, to facilitate the development of practice guidelines for stroke prevention in specific clinical scenarios.

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.

Aura in trigeminal autonomic cephalalgia is probably mediated by comorbid migraine with aura

OBJECTIVE

The presence of aura is rare in cluster headache, and even rarer in other trigeminal autonomic cephalalgias. We hypothesized that the presence of aura in patients with trigeminal autonomic cephalalgias is frequently an epiphenomenon and mediated by comorbid migraine with aura.

METHODS

The study retrospectively reviewed 480 patients with trigeminal autonomic cephalalgia in a tertiary medical center for 10 years. Phenotypes and temporal correlation of aura with headache were analyzed. Trigeminal autonomic cephalalgia patients with aura were further followed up in a structured telephone interview.

RESULTS

Seventeen patients with aura (3.5%) were identified from 480 patients with trigeminal autonomic cephalalgia, including nine with cluster headache, one with paroxysmal hemicrania, three with hemicrania continua, and four with probable trigeminal autonomic cephalalgia. Compared to trigeminal autonomic cephalalgia patients without aura, trigeminal autonomic cephalalgia patients with aura were more likely to have a concomitant diagnosis of migraine with aura (odds ratio [OR] = 109.0, 95% CI 30.9-383.0, p < 0.001); whereas the risk of migraine without aura remains similar between both groups (OR = 1.10, 95% CI = 0.14-8.59, p = 0.931). Aura was more frequently accompanied with migraine-like attacks, but not trigeminal autonomic cephalalgia attacks.

INTERPRETATION

In most patients with trigeminal autonomic cephalalgia, the presence of aura is mediated by the comorbidity of migraine with aura. Aura directly related to trigeminal autonomic cephalalgia attack may exist but remains rare. Our results suggest that aura may not be involved in the pathophysiology of trigeminal autonomic cephalalgia.

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

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

Treatment of Long-term Sudden Sensorineural Hearing Loss as an Otologic Migraine Phenomenon

OBJECTIVES

To describe a cohort of patients presenting with long-term sudden sensorineural hearing loss (SSNHL) treated with prophylactic migraine and intratympanic steroid therapy.

METHODS

Patients presenting to a neurotology clinic at least 6 weeks from SSNHL onset were included. All patients received migraine prophylactic medication (nortriptyline, topiramate, and/or verapamil) and lifestyle changes for at least 6 weeks, as well as intratympanic steroid injections, if appropriate.

RESULTS

Twenty-one patients (43% female) with a mean age of 64 ± 11 years who presented 9 ± 8 months (median = 5) from symptom onset were included. Posttreatment hearing thresholds were significantly improved compared with pretreatment thresholds at 500 Hz (49 ± 19 dB versus 55 ± 20 dB, p = 0.01), 1000 Hz (52 ± 19 dB versus 57 ± 21 dB, p = 0.03), low-frequency pure-tone average (53 ± 15 dB versus 57 ± 17 dB, p = 0.01), and speech-frequency pure-tone average (57 ± 13 dB versus 60 ± 15 dB, p = 0.02). Posttreatment word-recognition-score (WRS) and speech-recognition-threshold (SRT) were also significantly improved (45 ± 28% versus 70 ± 28% and 57 ± 18 dB versus 50 ± 16 dB, respectively, both p < 0.01). Notably, ≥15% improvement in WRS and ≥10 dB improvement in SRT was observed in 13 (68%) and 8 (40%) patients, respectively. Of the 11 patients who presented with initial < 50% WRS, 8 (73%) had improved posttreatment >50% WRS with an average improvement of 39 ± 9%.

CONCLUSIONS

Migraine medications in addition to intratympanic steroid injections significantly improved SRT and hearing frequencies in 40% and 29% of SSNHL patients, respectively, while significant WRS recovery was observed in most (68%) patients. This suggests SSNHL may be an otologic migraine phenomenon, which may be at least partially reversible even after the traditional 30-day postonset window.

Migraine Visual Aura and Cortical Spreading Depression-Linking Mathematical Models to Empirical Evidence

This review describes the subjective experience of visual aura in migraine, outlines theoretical models of this phenomenon, and explores how these may be linked to neurochemical, electrophysiological, and psychophysical differences in sensory processing that have been reported in migraine with aura. Reaction-diffusion models have been used to model the hallucinations thought to arise from cortical spreading depolarisation and depression in migraine aura. One aim of this review is to make the underlying principles of these models accessible to a general readership. Cortical spreading depolarisation and depression in these models depends on the balance of the diffusion rate between excitation and inhibition and the occurrence of a large spike in activity to initiate spontaneous pattern formation. We review experimental evidence, including recordings of brain activity made during the aura and attack phase, self-reported triggers of migraine, and psychophysical studies of visual processing in migraine with aura, and how these might relate to mechanisms of excitability that make some people susceptible to aura. Increased cortical excitability, increased neural noise, and fluctuations in oscillatory activity across the migraine cycle are all factors that are likely to contribute to the occurrence of migraine aura. There remain many outstanding questions relating to the current limitations of both models and experimental evidence. Nevertheless, reaction-diffusion models, by providing an integrative theoretical framework, support the generation of testable experimental hypotheses to guide future research.

Comparative analysis of spreading depolarizations in brain slices exposed to osmotic or metabolic stress

BACKGROUND

Recurrent spreading depolarizations (SDs) occur in stroke and traumatic brain injury and are considered as a hallmark of injury progression. The complexity of conditions associated with SD in the living brain encouraged researchers to study SD in live brain slice preparations, yet methodological differences among laboratories complicate integrative data interpretation. Here we provide a comparative evaluation of SD evolution in live brain slices, in response to selected SD triggers and in various media, under otherwise standardized experimental conditions.

METHODS

Rat live coronal brain slices (350 μm) were prepared (n = 51). Hypo-osmotic medium (Na+ content reduced from 130 to 60 mM, HM) or oxygen-glucose deprivation (OGD) were applied to cause osmotic or ischemic challenge. Brain slices superfused with artificial cerebrospinal fluid (aCSF) served as control. SDs were evoked in the control condition with pressure injection of KCl or electric stimulation. Local field potential (LFP) was recorded via an intracortical glass capillary electrode, or intrinsic optical signal imaging was conducted at white light illumination to characterize SDs. TTC and hematoxylin-eosin staining were used to assess tissue damage.

RESULTS

Severe osmotic stress or OGD provoked a spontaneous SD. In contrast with SDs triggered in aCSF, these spontaneous depolarizations were characterized by incomplete repolarization and prolonged duration. Further, cortical SDs under HM or OGD propagated over the entire cortex and occassionally invaded the striatum, while SDs in aCSF covered a significantly smaller cortical area before coming to a halt, and never spread to the striatum. SDs in HM displayed the greatest amplitude and the most rapid propagation velocity. Finally, spontaneous SD in HM and especially under OGD was followed by tissue injury.

CONCLUSIONS

While the failure of Na+/K+ ATP-ase is thought to impair tissue recovery from OGD-related SD, the tissue swelling-related hyper excitability and the exhaustion of astrocyte buffering capacity are suggested to promote SD evolution under osmotic stress. In contrast with OGD, SD propagating under hypo-osmotic condition is not terminal, yet it is associated with irreversible tissue injury. Further investigation is required to understand the mechanistic similarities or differences between the evolution of SDs spontaneously occurring in HM and under OGD.

Brain Energy Deficit as a Source of Oxidative Stress in Migraine: A Molecular Basis for Migraine Susceptibility

People with migraine are prone to a brain energy deficit between attacks, through increased energy demand (hyperexcitable brain) or decreased supply (mitochondrial impairment). However, it is uncertain how this precipitates an acute attack. Here, the central role of oxidative stress is adduced. Specifically, neurons' antioxidant defenses rest ultimately on internally generated NADPH (reduced nicotinamide adenine dinucleotide phosphate), whose levels are tightly coupled to energy production. Mitochondrial NADPH is produced primarily by enzymes involved in energy generation, including isocitrate dehydrogenase of the Krebs (tricarboxylic acid) cycle; and an enzyme, nicotinamide nucleotide transhydrogenase (NNT), that depends on the Krebs cycle and oxidative phosphorylation to function, and that works in reverse, consuming antioxidants, when energy generation fails. In migraine aura, cortical spreading depression (CSD) causes an initial severe drop in level of NADH (reduced nicotinamide adenine dinucleotide), causing NNT to impair antioxidant defense. This is followed by functional hypoxia and a rebound in NADH, in which the electron transport chain overproduces oxidants. In migraine without aura, a similar biphasic fluctuation in NADH very likely generates oxidants in cortical regions farthest from capillaries and penetrating arterioles. Thus, the perturbations in brain energy demand and/or production seen in migraine are likely sufficient to cause oxidative stress, triggering an attack through oxidant-sensing nociceptive ion channels. Implications are discussed for the development of new classes of migraine preventives, for the current use of C57BL/6J mice (which lack NNT) in preclinical studies of migraine, for how a microembolism initiates CSD, and for how CSD can trigger a migraine.

Endolymphatic Hydrops in Patients With Vestibular Migraine and Concurrent Meniere's Disease

Objective: Intravenous contrast agent enhanced, high-resolution magnetic resonance imaging of the inner ear (iMRI) confirmed that patients with Menière's disease (MD) and vestibular migraine (VM) could present with endolymphatic hydrops (EH). The present study aimed to investigate EH characteristics and their interrelation to neurotologic testing in patients with VM, MD, or VM with concurrent MD (VM-MD).

Methods: Sixty–two patients (45 females, aged 23–81 years) with definite or probable VM (n = 25, 19 definite), MD (n = 29, 17 definite), or showing characteristics of both diseases (n = 8) were included in this study. Diagnostic workup included neurotologic assessments including video-oculography (VOG) during caloric stimulation and head-impulse test (HIT), ocular and cervical vestibular evoked myogenic potentials (o/cVEMP), pure tone audiometry (PTA), as well as iMRI. EH's degree was assessed visually and via volumetric quantification using a probabilistic atlas-based segmentation of the bony labyrinth and volumetric local thresholding (VOLT).

Results: Although a relevant number of VM patients reported varying auditory symptoms (13 of 25, 52.0%), EH in VM was only observed twice. In contrast, EH in VM-MD was prevalent (2/8, 25%) and in MD frequent [23/29, 79.3%; χ²(2) = 29.1, p < 0.001, φ = 0.7]. Location and laterality of EH and neurophysiological testing classifications were highly associated (Fisher exact test, p < 0.005). In MD, visual semi-quantitative grading and volumetric quantification correlated highly to each other (r_S = 0.8, p < 0.005, two-sided) and to side differences in VOG during caloric irrigation (vestibular EH ipsilateral: r_S = 0.6, p < 0.05, two-sided). In VM, correlations were less pronounced. VM-MD assumed an intermediate position between VM and MD.

Conclusion: Cochlear and vestibular hydrops can occur in MD and VM patients with auditory symptoms; this suggests inner ear damage irrespective of the diagnosis of MD or VM. The EH grades often correlated with auditory symptoms such as hearing impairment and tinnitus. Further research is required to uncover whether migraine is one causative factor of EH or whether EH in VM patients with auditory symptoms suggests an additional pathology due to MD.

Structural and Functional Brain Changes in Migraine

Migraine is a prevalent primary headache disorder and is usually considered as benign. However, structural and functional changes in the brain of individuals with migraine have been reported. High frequency of white matter abnormalities, silent infarct-like lesions, and volumetric changes in both gray and white matter in individuals with migraine compared to controls have been demonstrated. Functional magnetic resonance imaging (MRI) studies found altered connectivity in both the interictal and ictal phase of migraine. MR spectroscopy and positron emission tomography studies suggest abnormal energy metabolism and mitochondrial dysfunction, as well as other metabolic changes in individuals with migraine. In this review, we provide a brief overview of neuroimaging studies that have helped us to characterize some of these changes and discuss their limitations, including small sample sizes and poorly defined control groups. A better understanding of alterations in the brains of patients with migraine could help not only in the diagnosis but may potentially lead to the optimization of a targeted anti-migraine therapy.

Migraine and aura triggered by normobaric hypoxia

BACKGROUND

For future experimental studies or the development of targeted pharmaceutical agents, a deeper insight into the pathophysiology of migraine is of utmost interest. Reliable methods to trigger migraine attacks including aura are desirable to study this complex disease in vivo.

METHODS

To investigate hypoxia as a trigger for migraine and aura, we exposed volunteers diagnosed with migraine, with (n = 16) and without aura (n = 14), to hypoxia utilizing a hypoxic chamber adjusted to a FiO₂ of 12.6%. The occurrence of headache, migraine, aura, and accompanying symptoms were registered and vital signs were collected for 6 hours under hypoxia and 2 hours of follow-up. A binary logistic regression analysis examined the probability of triggering headaches, migraines, aura, photo- and phonophobia.

FINDINGS

Of 30 participants, 24 (80.0%) developed headaches and 19 (63.3%) migraine, five (16.7%) reported aura. Two patients that developed aura never experienced aura symptoms before in their life. The increase of mean heart frequency was higher in patients developing headaches or migraine. Mean SpO₂ during hypoxia was 83.39%.

CONCLUSION

Hypoxia was able to trigger migraine attacks and aura independently of any pharmacological agent.

Non-invasive vagus nerve stimulation for primary headache: A clinical update

Background

Non-invasive vagus nerve stimulation (nVNS) is a proven treatment for cluster headache and migraine. Several possible mechanisms of action by which nVNS mitigates headache have been identified.

Methods

We conducted a narrative review of recent scientific and clinical research into nVNS for headache, including findings from mechanistic studies and their possible relationships to the clinical effects of nVNS.

Results

Findings from animal and human studies have provided possible mechanistic explanations for nVNS efficacy in headache involving four core areas: Autonomic nervous system functions; cortical spreading depression inhibition; neurotransmitter regulation; and nociceptive modulation. We discuss how overlap and interplay among these areas may underlie the utility of nVNS in the context of clinical evidence supporting its safety and efficacy as acute and preventive therapy for both cluster headache and migraine. Possible future nVNS applications are also discussed.

Conclusion

Significant progress over the past several years has yielded valuable mechanistic and clinical evidence that, combined with the excellent safety and tolerability profile of nVNS, suggests that it should be considered a first-line treatment for both acute and preventive treatment of cluster headache, an effective option for acute treatment of migraine, and a highly relevant, practical option for migraine prevention.

Therapeutic implications of cortical spreading depression models in migraine

Migraine is among the most common and disabling neurological diseases in the world. Cortical spreading depression (CSD) is a wave of near-complete depolarization of neurons and glial cells that slowly propagates along the cortex creating the perception of aura. Evidence suggests that CSD can trigger migraine headache. Experimental models of CSD have been considered highly translational as they recapitulate migraine-related phenomena and have been validated for screening migraine therapeutics. Here we outline the essential components of validated experimental models of CSD and provide a comprehensive review of potential modulators and targets against CSD. We further focus on novel interventions that have been recently shown to suppress CSD susceptibility that may lead to therapeutic targets in migraine.

Migraine and Ischemic Stroke: Deciphering the Bidirectional Pathway

Migraine and stroke are common, disabling neurological conditions with several theories being proposed to explain this bidirectional relationship. Migraine is considered as a benign neurological disorder, but research has revealed a connection between migraine and stroke, predominantly those having migraine with aura (MA). Among migraineurs, females with MA are more susceptible to ischemic stroke and may have a migrainous infarction. Migrainous infarction mostly occurs in the posterior circulation of young women. Although there are several theories about the potential relationship between MA and stroke, the precise pathological process of migrainous infarction is not clear. It is assumed that cortical spreading depression (CSD) might be one of the essential factors for migrainous infarction. Other factors that may contribute to migrainous infarction may be genetic, hormonal fluctuation, hypercoagulation, and right to left cardiac shunts. Antimigraine drugs, such as ergot alkaloids and triptans, are widely used in migraine care. Still, they have been found to cause severe vasoconstriction, which may result in the development of ischemia. It is reported that patients with stroke develop migraines during the recovery phase. Both experimental and clinical data suggest that cerebral microembolism can act as a potential trigger for MA. Further studies are warranted for the treatment of migraine, which may lead to a decline in migraine-related stroke. In this present article, we have outlined various potential pathways that link migraine and stroke.