Migraine Pathophysiology Research Articles

Sensitization of meningeal afferents to locomotion-related meningeal deformations in a migraine model

Migraine headache is hypothesized to involve the activation and sensitization of trigeminal sensory afferents that innervate the cranial meninges. To better understand migraine pathophysiology and improve clinical translation, we used two-photon calcium imaging via a closed cranial window in awake mice to investigate changes in the responses of meningeal afferent fibers using a preclinical model of migraine involving cortical spreading depolarization (CSD). A single CSD episode caused a seconds-long wave of calcium activation that propagated across afferents and along the length of individual afferents. Surprisingly, unlike previous studies in anesthetized animals with exposed meninges, only a very small afferent population was persistently activated in our awake mouse preparation, questioning the relevance of this neuronal response to the onset of migraine pain. In contrast, we identified a larger subset of meningeal afferents that developed augmented responses to acute three-dimensional meningeal deformations that occur in response to locomotion bouts. We observed increased responsiveness in a subset of afferents that were already somewhat sensitive to meningeal deformation before CSD. Furthermore, another subset of previously insensitive afferents also became sensitive to meningeal deformation following CSD. Our data provides new insights into the mechanisms underlying migraine, including the emergence of enhanced meningeal afferent responses to movement-related meningeal deformations as a potential neural substrate underlying the worsening of migraine headache during physical activity.

Sensitization of meningeal afferents to locomotion-related meningeal deformations in a migraine model.

Migraine headache is hypothesized to involve the activation and sensitization of trigeminal sensory afferents that innervate the cranial meninges. To better understand migraine pathophysiology and improve clinical translation, we used two-photon calcium imaging via a closed cranial window in awake mice to investigate changes in the responses of meningeal afferent fibers using a preclinical model of migraine involving cortical spreading depolarization (CSD). A single CSD episode caused a seconds-long wave of calcium activation that propagated across afferents and along the length of individual afferents. Surprisingly, unlike previous studies in anesthetized animals with exposed meninges, only a very small afferent population was persistently activated in our awake mouse preparation, questioning the relevance of this neuronal response to the onset of migraine pain. In contrast, we identified a larger subset of meningeal afferents that developed augmented responses to acute three-dimensional meningeal deformations that occur in response to locomotion bouts. We observed increased responsiveness in a subset of afferents that were already somewhat sensitive to meningeal deformation before CSD. Furthermore, another subset of previously insensitive afferents also became sensitive to meningeal deformation following CSD. Our data provides new insights into the mechanisms underlying migraine, including the emergence of enhanced meningeal afferent responses to movement-related meningeal deformations as a potential neural substrate underlying the worsening of migraine headache during physical activity.

Novel FDA-approved zavegepant drug for treating migraine

Migraine is a complex neurological disorder characterized by recurring episodes of severe headaches. The pathophysiology of migraine involves abnormalities in neuronal networks, cortical spreading depression, and sensitization of trigeminovascular pathways. The global prevalence of migraine has increased substantially, warranting advancements in treatment strategies. A significant trigger in migraine pathophysiology is calcitonin gene-related peptide (CGRP). Several drugs, such as gepants and monoclonal antibodies (MABs) targeting CGRP or its receptor, have been developed to antagonize CGRP signaling. Zavegepant (Zavzpret), a novel CGRP receptor antagonist, has recently been approved by the FDA for the acute treatment of migraine. Clinical trials have demonstrated its efficacy in providing headache and symptom relief, with a statistically significant percentage of patients achieving freedom from headaches and most bothersome symptoms. Despite mild adverse effects, such as taste disorders and nausea, Zavzpret’s overall safety profile remains acceptable.

Gut microbiota and metabolite variations in a migraine mouse model.

Migraine is a prevalent clinical disorder characterized by recurrent unilateral throbbing headache episodes accompanied by symptoms such as nausea, vomiting, photophobia, and phonophobia. Despite its common occurrence, the diagnosis, pathophysiology, and treatment of migraine remain controversial. Extensive research has implicated the gut microbiota in various central nervous system disorders, including anxiety disorders, depression, and Parkinson's disease. Some studies have also suggested that migraine may stem from disruptions to neurohormones and metabolism. This study aimed to investigate the disparities in gut microbiota and metabolites between migraine mice model and normal mice to shed light on the underlying mechanisms and potential therapeutic approaches. Distinct differences in gut microbial composition were observed between the migraine mouse model and normal mouse, indicating a potential correlation between these variations and the pathogenesis of migraine. This study provides evidence of differences in gut microbiota composition and metabolites between a migraine mouse model and normal mice, which showed that Akkermansiaceae constituted the most abundant taxon in the sham injection mouse group, while Lachnospiraceae constituted the most prevalent group in the migraine mouse model group. The associations between the abundances of Akkermansia muciniphila and Lachnospiraceae bacteria and metabolites suggested their potential roles in the pathogenesis of migraine. The altered abundance of Lachnospiraceae observed in migraine-afflicted mice and its correlations with changes in metabolites suggest that it may affect the host's health. Thus, probiotic therapy emerges as a possible treatment for migraine. Moreover, significant disparities in gut metabolites were observed between the migraine mouse model and normal mice. These alterations encompass multiple metabolic pathways, suggesting that metabolic disturbances may also contribute to the development of migraines.

Migraine and endovascular closure of patent foramen ovale as a method of its treatment: a literature review

The literature review is devoted to the pathophysiology and clinical picture of migraine, targets of therapy and drugs used, and the connection between the pathogenesis of migraine with aura and patent foramen ovale is discussed. The results of clinical studies show a positive effect of endovascular patent foramen ovale closure on the course of migraine in the form of a decrease in the intensity, frequency of attacks and the number of headache-free days, as well as in some cases complete relief of the disease. Further study of the topic is promising, but requires careful study design and long-term follow-up of patients.

Serum calcitonin gene-related peptide in patients with persistent post-concussion symptoms, including headache: a cohort study.

Calcitonin gene-related peptide (CGRP) plays an important role in migraine pathophysiology, and post-traumatic headache (PTH) frequently presents with migraine-like features. Despite several clinical similarities, few studies have explored CGRP in PTH and concussion. This study investigates serum CGRP levels in patients with persistent post-concussion symptoms (PPCS), including PTH. This cohort study was based on serum samples from individuals aged 18-30years with PPCS who participated in a previously published randomized controlled trial of a non-pharmacological intervention. The primary outcome was serum CGRP concentrations, determined at baseline before randomization and at follow-up 7months later, using an enzyme-linked immunosorbent assay (ELISA). CGRP levels at baseline were compared with healthy anonymous blood donors in the same age group. Baseline serum samples were collected from 86 participants with PPCS. The participants were most often female (78%) and migraine-like headache was the most frequent headache phenotype (74%). Serum CGRP levels were higher in participants with PPCS than in 120 healthy individuals (median: 158.5pg/mL vs. 76.3pg/mL, p = 0.050). A stratified analysis revealed that females with PPCS had a fivefold higher median than healthy females (166.3pg/mL vs. 32.1pg/mL, p = 0.0006), while no differences were observed in males (p = 0.83). At follow-up, CGRP levels decreased with a median change of - 1.3pg/mL (95% confidence interval: - 17.6-0, p = 0.024). Elevated serum levels of CGRP in patients with PPCS and a decrease over time suggest an involvement of CGRP in PTH/PPCS. If confirmed in other studies, it could pave the way for CGRP-targeted therapies, which could have clinical significance.

The Role of Biomarkers Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and Vasoactive Intestinal Peptide (VIP) in Chronic and Episodic Migraines: A Meta-Analysis

Background. Migraine is a neurological disorder that results in disability accumulation, and there are no blood-based markers for indicating migraine susceptibility. Here, we aimed to evaluate the possible biomarker role of neuropeptides, vasoactive intestinal peptide (VIP), and pituitary adenylate cyclase-activating polypeptide (PACAP) in chronic (CM) and episodic migraine (EM). Method. PubMed, medRxiv, and Google Scholar databases were searched up to the 7th of September 2022 using the search syntax to define all relevant articles addressing the plasma and serum levels of VIP and PACAP in migraineurs and controls. Concerning bias assessment, the risk of bias in nonrandomized studies-I (ROBINS-I) was assessed. Also, the standardized mean difference (SMD) was measured with a random effects model. Results. Five case-control studies with 503 migraine cases were included. CM patients had elevated VIP levels compared to controls (SMD=0.44, 95% CI 0.25-0.62, p<0.00001). In contrast, PACAP levels were lower in EM patients (SMD=−0.30, 95% CI -0.48 to -0.11, p=0.002). Overall, migraine cases had higher VIP levels (SMD=0.25, 95% CI 0.11-0.39, p=0.0006) but lower PACAP levels (SMD=−0.16, 95% CI -0.30 to -0.03, p=0.020) than controls. Conclusion. The results support the role of VIP and PACAP neuropeptides in migraine pathophysiology. CM patients have significantly higher serum VIP levels, while EM patients have lower serum PACAP levels compared to controls. Further studies should confirm these findings.

Atogepant: Mechanism of action, clinical and translational science.

Since the discovery of calcitonin gene-related peptide (CGRP) in 1982, its integral role in migraine pathophysiology, specifically migraine pain, has been demonstrated through cumulative scientific discoveries that have led to the development and approval of migraine-specific therapeutics. Today, eight drugs, including monoclonal antibodies and small molecule CGRP receptor antagonists, known as gepants, have received approval for acute or preventive treatment of migraine. The primary mechanism of these drugs is to block CGRP signaling, thus preventing CGRP-mediated nociception and neurogenic inflammation. Here, we focus on atogepant, a highly potent and selective gepant and the first and only oral medication approved for the preventive treatment of both episodic and chronic migraine in adults. In this article, we summarize the role of CGRP in migraine pathophysiology and the mechanism of action of atogepant. In addition, we provide an overview of atogepant's pharmacology and the key clinical trials and outcomes that have demonstrated the safety and efficacy of atogepant.

Calcitonin gene-related peptide in pathophysiology of migraine

Calcitonin gene-related peptide in pathophysiology of migraine

Acute medications' intake for migraine: a one-year report in patients undergoing first evaluation at a third level Italian headache center.

Headache disorders, particularly primary headaches like migraine and tension-type headache, still remain underdiagnosed and undertreated despite their high prevalence and significant impact on quality of life. In recent years, several specific medications targeting key pathways in the pathophysiology of migraine have been developed. Despite this advancement, numerous studies indicate that non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics remain the most commonly used drugs. This study focused on the use of NSAIDs and simple analgesics as acute treatments for migraine among patients at a tertiary headache center. A retrospective observational study was conducted at the Fondazione Policlinico Universitario Campus Bio-Medico throughout 2022. Data were collected on the type and frequency of headaches, the usage and dosage of NSAIDs and other medications, and changes in their use at follow-up visits. Statistical analyses were performed to evaluate the efficacy and determinants of NSAID consumption and headache frequency changes. Two hundred and eightythree patients diagnosed with migraine undergoing their first examination at our center were enrolled. Initially, 58.7% of patients used NSAIDs or simple analgesics, which decreased to 46.6% 3 months after, while triptan use increased from 65.1 to 72.8%. Changes in prophylactic therapies were significantly associated with a decrease in NSAID intake (W = 834.000, p = 0.004) and in headache frequency (W = 5960.5, p = 0.003). Specifically, the addition of topiramate or amitriptyline was associated with a reduction in NSAID use and headache frequency. Even pain freedom after the intake of NSAIDs improved from 55.2 to 79.4% of cases at follow-up. The study highlights the importance of appropriate diagnosis and tailored treatment strategies in the management of primary headaches. It underscores the need for specialized care to enhance treatment efficacy and patient outcomes, demonstrating that adjustments in prophylactic therapy can significantly reduce NSAID intake and improve headache care. This reinforces the role of tertiary headache centers in providing specialized care that can adapt treatments to individual patient needs and improve overall headache management.

Epileptic seizure and migraine attack: A revisit from the "Borderland of Epilepsy" to clinical implementation of infraslow activity/DC shifts in scalp EEG

Migraine attacks, especially ones with aura, have symptoms similar to epileptic seizures, and the two may sometimes be difficult to differentiate clinically. However, the characteristic minute-by-minute symptom development and progress within 60 ‍min is useful for diagnosis. Although the details of its pathophysiology remain unsolved, cortical spreading depolarization (CSD) is one of the main pathogenetic factors. In epilepsy, clinical data have shown that ictal DC shifts could reflect impaired homeostasis of extracellular potassium by astrocyte dysfunction. Ictal DC shifts were found to be difficult to detect by scalp EEG, but can be clinically recorded from the seizure focus using wide-band EEG method. The similarity between DC shifts and CSD has been gaining attention from the neurophysiology point of view. The clinical implementation of infraslow activity/DC shifts analysis of scalp EEG is expected to elucidate further the pathophysiology of migraine, which may lie in the borderland of epilepsy.

Ubrogepant: Mechanism of action, clinical and translational science.

In recent years, the treatment of migraine has experienced a breakthrough in the development of drugs that target the calcitonin gene-related peptide (CGRP) signaling pathway. Monoclonal antibodies against the receptor or ligand have been developed for the preventive treatment of migraine; whereas, orally administered small molecule CGRP receptor antagonists, called gepants, have been developed for both acute and/or preventive treatment. Both modalities have demonstrated safe and effective treatment of migraine, reducing the number of migraine days for patients as well as reducing symptoms and improving patient function and overall quality of life. Here, we provide an abridged review of ubrogepant, an oral CGRP receptor antagonist, approved for the acute treatment of migraine. We briefly summarize the role of CGRP in migraine pathophysiology, describing the mechanism of action of ubrogepant in the context of this pathway, the clinical pharmacology properties and the clinical development and outcomes, including safety, efficacy, pharmacokinetics, and pharmacodynamics, that supported ubrogepant's approval.

Impulsivity in migraine and in medication overuse headache: A literature review

IntroductionPsychiatric symptoms and analgesic overuse may contribute to migraine chronification. Impulsivity is a common symptom in several psychiatric disorders that can potentiate substance overuse, including analgesics. Dopamine has been associated with migraine pathophysiology and impulsivity.ObjectiveThis review aims to assess the current knowledge about the potential association between migraine and impulsivity.MethodsPubMed and LILACS were queried using relevant descriptors related to migraine and impulsivity.ResultsFive articles were selected; however, none revealed a significant correlation between migraine and impulsivity. This lack of correlation was verified in different migraine subtypes (with or without aura, chronic, or episodic).ConclusionThe heterogeneity in patient grouping and diverse impulsivity assessment tools of the studies precluded definitive conclusions. The Barratt Impulsivity Scale (BIS-11) was the most frequently used tool. Given the paucity of data and the potential impact on migraine management, further studies are crucial to elucidate the potential association between migraine and impulsivity.

Association between vertebral artery dominance and basilar artery curvature in migraineurs: an anatomical magnetic resonance imaging study.

Numerous studies demonstrate a link between cerebrovascular alterations and migraine pathogenesis. We investigated the association between migraine and vertebral artery dominance (VAD), basilar artery (BA) curvature, and elongation. This cross-sectional MRI study included 74 migraine patients and 74 control subjects aged between 18 and 55 years. Diameters of the intracranial part of the vertebral artery (VA) and BA, height of the BA bifurcation, and total lateral displacement of the BA were measured. In addition, we investigated the directional relationship between VAD and BA curvature. There were no statistically significant differences between the groups regarding VA and BA diameters and total lateral displacement of the BA. The height of the BA bifurcation was found to be significantly higher in migraine patients compared to controls (p = 0.002). The left-side VAD was more frequent in migraine patients compared to control subjects (60.8% (45/74) vs 41.9% (31/74), p = 0.001). In migraine patients, particularly those with aura (MwA) patients, with left-side VAD, the rate of BA displacement to the right side is significantly higher than those with right-side VAD or non-VAD (p = 0.022). Also, we found that total lateral displacement of the BA is correlated with VA asymmetry in patients with MwA (r = 0.538, p = 0.007). VAD and its opposite-directional relationship with the lateral displacement of the BA may be associated with migraine pathophysiology. Together with aging, this association may contribute to changes in the vertebrobasilar system (VBS) geometry which may result in increased risk for posterior circulation infarction (PCI) in migraineurs.

Relationship of Plasma Pituitary Adenylate Cyclase-Activating Polypeptide-38 (PACAP-38) Levels with Cerebrovascular Vasomotor Reactivity in Chronic Migraine Sufferers

Introduction: Migraine is a complex health problem and causes disability, especially in women. The current pathophysiology of migraine is a combination of vascular, neurogenic, and neuroinflammatory theories. PACAP-38 is a vasoactive neuropeptide that increases during migraine attacks. Endothelial dysfunction results in impaired vasomotor reactivity. Analysis of vasomotor reactivity is determined by measuring the breath-holding index (BHI) and migraine vascular index (MVI), where there is a decrease in vasomotor reactivity values ??in migraine sufferers. This study aims to determine PACAP-38 levels in chronic migraine sufferers and their relationship to cerebrovascular vasomotor reactivity.
 Methods: This research is a comparative study (cross-sectional) that is carried out in hospitals and health centers spread across the city of Padang from May 2022 to June 2023. The research sample consisted of 30 chronic migraine sufferers and 30 healthy controls. Vasomotor reactivity was assessed by determining BHI and MVI values ??using transcranial Doppler. Plasma PACAP-38 levels were measured using the ELISA method. Data analysis was carried out using SPSS.
 Results: The mean value of vasomotor reactivity in chronic migraine sufferers is 0.355. There is a negative correlation between the frequency and duration of migraine attacks and vasomotor reactivity (frequency p=0.032; duration p=0.022). The mean value of PACAP-38 levels in chronic migraine sufferers was 6.15 pg/ml, and in healthy controls, 4.85 pg/ml; there was a significant difference between plasma PACAP-38 levels in chronic migraine sufferers compared to healthy controls. However, there was no significant difference between plasma PACAP-38 levels and vasomotor reactivity in chronic migraine sufferers.
 Conclusion: There is an increase in plasma PACAP-38 levels in chronic migraine sufferers, but there is no significant relationship between plasma PACAP-38 levels and vasomotor reactivity values.

Alterations in DNA methylation associate with reduced migraine and headache days after medication withdrawal treatment in chronic migraine patients: a longitudinal study

BackgroundChronic migraine, a highly disabling migraine subtype, affects nearly 2% of the general population. Understanding migraine chronification is vital for developing better treatment and prevention strategies. An important factor in the chronification of migraine is the overuse of acute headache medication. However, the mechanisms behind the transformation of episodic migraine to chronic migraine and vice versa have not yet been elucidated. We performed a longitudinal epigenome-wide association study to identify DNA methylation (DNAm) changes associated with treatment response in patients with chronic migraine and medication overuse as part of the Chronification and Reversibility of Migraine clinical trial. Blood was taken from patients with chronic migraine (n = 98) at baseline and after a 12-week medication withdrawal period. Treatment responders, patients with ≥ 50% reduction in monthly headache days (MHD), were compared with non-responders to identify DNAm changes associated with treatment response. Similarly, patients with ≥ 50% versus < 50% reduction in monthly migraine days (MMD) were compared.ResultsAt the epigenome-wide significant level (p < 9.42 × 10–8), a longitudinal reduction in DNAm at an intronic CpG site (cg14377273) within the HDAC4 gene was associated with MHD response following the withdrawal of acute medication. HDAC4 is highly expressed in the brain, plays a major role in synaptic plasticity, and modulates the expression and release of several neuroinflammation markers which have been implicated in migraine pathophysiology. Investigating whether baseline DNAm associated with treatment response, we identified lower baseline DNAm at a CpG site (cg15205829) within MARK3 that was significantly associated with MMD response at 12 weeks.ConclusionsOur findings of a longitudinal reduction in HDAC4 DNAm status associated with treatment response and baseline MARK3 DNAm status as an early biomarker for treatment response, provide support for a role of pathways related to chromatin structure and synaptic plasticity in headache chronification and introduce HDAC4 and MARK3 as novel therapeutic targets.

Unraveling the MSG-Headache Controversy: an Updated Literature Review.

To review the evidence and role of monosodium glutamate (MSG) as a headache and migraine trigger. MSG is a common food additive, has widely been linked as a trigger of headache, as well as other symptoms. However, the evidence for MSG as a causative agent for headache is debated. Various clinical trials over the past several decades have reported conflicting results, with studies suggesting that MSG does and does not increase the incidence of headache. However, the dosages of MSG exposure are often inconsistent across studies, with many studies administering a dose significantly higher than the average consumption.. Additionally, there are misconceptions about which foods and cuisines have MSG in them. MSG could be a potential trigger for migraine and headaches. It is unclear exactly how MSG plays into the migraine pathophysiology. It's crucial to accurately determine if MSG is present in one's diet to evaluate its potential impact on headaches.

Gastrodin alleviates NTG-induced migraine-like pain via inhibiting succinate/HIF-1α/TRPM2 signaling pathway in trigeminal ganglion

BackgroundIncreasing evidence highlights the involvement of metabolic disorder and calcium influx mediated by transient receptor potential channels in migraine; however, the relationship between these factors in the pathophysiology of migraine remains unknown. Gastrodin is the major component of the traditional Chinese medicine Tianma, which is extensively used in migraine therapy. PurposeOur work aimed to explore the analgesic action of gastrodin and its regulatory mechanisms from a metabolic perspective. Methods/resultsAfter being treated with gastrodin, the mice were given nitroglycerin (NTG) to induce migraine. Gastrodin treatment significantly raised the threshold of sensitivity in response to both mechanical and thermal stimulus evidenced by von Frey and hot plate tests, respectively, and decreased total contact numbers in orofacial operant behavioral assessment. We found that the expression of transient receptor potential melastatin 2 (TRPM2) channel was increased in the trigeminal ganglion (TG) of NTG-induced mice, resulting in a sustained Ca2+ influx to trigger migraine pain. The content of succinate, a metabolic biomarker, was elevated in blood samples of migraineurs, as well as in the serum and TG tissue from NTG-induced migraine mice. Calcium imaging assay indicated that succinate insult elevated TRPM2-mediated calcium flux signal in TG neurons. Mechanistically, accumulated succinate upregulated hypoxia inducible factor-1α (HIF-1α) expression and promoted its translocation into nucleus, where HIF-1α enhanced TRPM2 expression through transcriptional induction in TG neurons, evidenced by luciferase reporter measurement. Gastrodin treatment inhibited TRPM2 expression and TRPM2-dependent Ca2+ influx by attenuating succinate accumulation and downstream HIF-1α signaling, and thereby exhibited analgesic effect. ConclusionThis work revealed that succinate was a critical metabolic signaling molecule and the key mediator of migraine pain through triggering TRPM2-mediated calcium overload. Gastrodin alleviated NTG-induced migraine-like pain via inhibiting succinate/HIF-1α/TRPM2 signaling pathway in TG neurons. These findings uncovered the anti-migraine effect of gastrodin and its regulatory mechanisms from a metabolic perspective and provided a novel theoretical basis for the analgesic action of gastrodin.

Reduction in retinal microvascular perfusion during migraine attacks.

To determine if there are changes in structure and function of the retinal vasculature during and between migraine attacks using optical coherence tomography angiography (OCTA). Migraine attacks commonly include visual symptoms, but the potential role of the retina in these symptoms is not well understood. OCTA is a rapid, non-invasive imaging technique that is used to visualize the retinal microvasculature with high spatial resolution in a clinical setting. In this study we used OCTA to quantify different features of the retinal vasculature in patients with migraine during and between attacks, as well as in healthy controls (HCs). We performed a prospective cohort study of 37 patients with migraine with aura (MA) (median [interquartile range, IQR] age of 37 [14] years, 86% female) and 30with migraine without aura (MO) (median [IQR] age of 37 [17] years, 77% female) and 20 HCs (median [IQR] age of 35 [7] years, 50% female). Macular OCTA scans were obtained for all participants for the interictal analysis. In 12 MA and eight MO, scans were captured both during and outside of migraine attacks and five HCs had initial and repeat scans. In addition to analyzing the morphology of the foveal avascular zone, we calculated the vessel flux index (VFI), which is an indicator of retinal perfusion and conventional metrics (such as vessel area density) in the foveal and parafoveal regions. There was a significant difference in the parafoveal VFI in the ictal state between the groups (p = 0.009). During migraine attacks there was a significant reduction in the parafoveal region VFI in MA (-7%, 95% confidence interval [CI] -10% to -4%; p = 0.006) and MO (-7%, 95% CI -10% to -3%; p = 0.016) from their interictal baseline as compared to the change between repeat scans in HCs (2%, 95% CI -3% to 7%). Interictally, there was a mean (standard deviation [SD]) 13% (10%) (p = 0.003) lower blood perfusion in the MA group as compared to the MO group in the foveal region (mean [SD] 0.093 [0.023] vs. 0.107 [0.021], p = 0.003). Interictal analysis also revealed higher circularity in the superficial foveal avascular zone in the MA group compared with the MO group (mean [SD] 0.686 [0.088] vs. 0.629 [0.120], p = 0.004). In addition, interictal analysis of the patients with MA or MO and unilateral headache showed increased retinal vascular parameters consistent with greater perfusion in the eye ipsilateral to the side of the pain as compared with the contralateral eye. These results indicate that perfusion is reduced in MA and MO in the parafoveal retina during the ictal period. Interictally, the foveal retina in MA has reduced perfusion when compared to the foveal retina in MO. Patients with unilateral headache showed interictal asymmetry of retinal perfusion between eyes. These results indicate that changes in retinal perfusion could be a part of migraine pathophysiology, and that distinct retinal vascular signatures identified with OCTA could represent biomarkers for migraine.

Ion Channel Disturbances in Migraine Headache: Exploring the Potential Role of the Kynurenine System in the Context of the Trigeminovascular System

Migraine is a primary headache disorder, which is an enormous burden to the healthcare system. While some aspects of the pathomechanism of migraines remain unknown, the most accepted theory is that activation and sensitization of the trigeminovascular system are essential during migraine attacks. In recent decades, it has been suggested that ion channels may be important participants in the pathogenesis of migraine. Numerous ion channels are expressed in the peripheral and central nervous systems, including the trigeminovascular system, affecting neuron excitability, synaptic energy homeostasis, inflammatory signaling, and pain sensation. Dysfunction of ion channels could result in neuronal excitability and peripheral or central sensitization. This narrative review covers the current understanding of the biological mechanisms leading to activation and sensitization of the trigeminovascular pain pathway, with a focus on recent findings on ion channel activation and modulation. Furthermore, we focus on the kynurenine pathway since this system contains kynurenic acid, which is an endogenous glutamate receptor antagonist substance, and it has a role in migraine pathophysiology.