Calcitonin gene-related peptide facilitates sensitization of the vestibular nucleus in a rat model of chronic migraine

Why is vestibular migraine associated with many comorbidities?

Vestibular migraine (VM) is a usual trigger of episodic vertigo. Patients with VM often experience spinning, shaking, or unsteady sensations, which are usually also accompanied by photophobia, phonophobia, motor intolerance, and more. VM is often associated with a number of comorbidities. Recurrent episodes of VM can affect the patient's emotions, sleep, and cognitive functioning to varying degrees. Patients with VM may be accompanied by adverse moods such as anxiety, fear, and depression, which can gradually develop into anxiety disorders or depressive disorders. Sleep disorders are also a common concomitant symptom of VM, which significantly lower patients' quality of life. The influence of anxiety disorders and sleep disorders may reduce cognitive functions of VM, such as visuospatial ability, attention, and memory decline. Clinically, it is also common to see VM comorbid with other vestibular disorders, making the diagnosis more difficult. VM episodes are relieved but lingering, in which case VM may coexist with persistent postural-perceptual dizziness (PPPD). Anxiety may be an important bridge between recurrent VM and PPPD. The clinical manifestations of VM and Meniere's disease (MD) overlap considerably, and those who meet the diagnostic criteria for both can be said to have VM/MD comorbidity. VM can also present with positional vertigo, and some patients with VM present with typical benign paroxysmal positional vertigo (BPPV) nystagmus on positional testing. In this paper, we synthesize and analyze the pathomechanisms of VM comorbidity by reviewing the literature. The results show that it may be related to the extensive connectivity of the vestibular system with different brain regions and the close connection of the trigeminovascular system with the periphery of the vestibule. Therefore, it is necessary to pay attention to the diagnosis of comorbidities in VM, synthesize its pathogenesis, and give comprehensive treatment to patients.

Monoclonal Antibodies Targeting CGRP to Treat Vestibular Migraine: A Rapid Systematic Review and Meta-Analysis

Vestibular migraine (VM), a subtype of migraine characterized by vestibular symptoms, poses a significant diagnostic and therapeutic challenge. This study aimed to evaluate the effectiveness of monoclonal antibodies targeting Calcitonin Gene Related Peptide (CGRP) in the treatment of VM. Therefore, we conducted a rapid systematic review and meta-analysis following PRISMA and Cochrane guidelines. A search of databases (PubMed, Scopus, Cochrane and Google Scholar) was performed in October 2023. Inclusion criteria required original research articles focusing on patients diagnosed with VM and utilizing CGRP-targeting monoclonal antibodies. We performed qualitative assessments of study design, patient characteristics, and outcomes and, for studies with comparable outcome measures, a meta-analysis was conducted. Our search yielded four relevant studies, including cohort studies and a case report, totaling 99 patients. Proper vestibular instrumental tests were employed in half of the studies. Overall, the included studies reported significant improvements in VM symptoms. Our quantitative analysis, focused on migraine symptoms, demonstrated a substantial reduction in Monthly Days with Migraine at 6 months following treatment. No severe adverse drug reactions were reported. In conclusion, this rapid systematic review and meta-analysis provide preliminary evidence for the efficacy of CGRP-targeting monoclonal antibodies in treating Vestibular Migraine. However, the absence of randomized controlled trials and variations in study designs and diagnostic criteria introduce some limitations. Further research is needed, including controlled trials, to establish a more robust evidence base. Nonetheless, this treatment approach offers hope for the effective management of VM, potentially enhancing the well-being of affected individuals and reducing their associated disability.

Effectiveness of Anti-Calcitonin Gene-Related Peptide Medication in Vestibular Migraine: A Retrospective Cohort Study in an Asian Population

BACKGROUND

Migraine and dizziness often coexist, with vestibular migraine (VM) presenting with vestibular symptoms and headaches. Calcitonin gene-related peptide (CGRP) may be involved in motion-induced symptoms; however, studies on the use of anti-CGRP monoclonal antibodies (mAbs) for the treatment of VM have yielded conflicting results. This study aimed to clarify the effectiveness of anti-CGRP mAbs in VM treatment.

METHODS

This retrospective observational cohort study, conducted between 1 January 2021 and 31 March 2023, assessed 12 Japanese patients with VM who were treated with anti-CGRP mAbs (CGRP group) for 6 months and 11 Japanese patients who received standard of care for VM and served as controls. Clinical questionnaires and equilibrium tests were administered, with primary outcomes including changes in Dizziness Handicap Inventory (DHI) scores compared with baseline values. Objective variables included the DHI score and explanatory variables included demographic data, balance test results, head-up tilt (HUT) test results, vestibular test results and questionnaire survey results. Analysis of variance was used to assess the treatment effects of anti-CGRP mAbs, and multivariate regression analysis was performed to identify mAb responders.

RESULTS

After 6 months, the CGRP group showed significant improvements in DHI scores [0 versus 6 months, odds ratio (95% confidence interval): 22.01 (0.13-43.88)] and number of vertigo/dizziness attacks per month [0 versus 6 months: 10.28 (2.80-17.76)]. No significant difference was observed in the control group [DHI scores, 0 versus 6 months: 0.65 (-26.84 to 28.14); number of vertigo/dizziness attacks per month, 0 versus 6 months: - 8.07 (- 23.77 to 7.62)]. Multivariate regression analysis showed that autonomic function at baseline was associated with mAb response in patients [β estimates (95% confidence interval): 3.63 (0.21-7.06)].

CONCLUSIONS

Treatment with anti-CGRP mAbs was more effective than conventional treatment in preventing migraine in patients with VM. While the identified factors associated with treatment responsiveness offer valuable insights into personalised treatment approaches, further prospective studies are warranted to validate the findings due to our study's retrospective design and limited sample size.

Focused Update on Migraine and Vertigo Comorbidity

PURPOSE OF REVIEW

To provide an update on comorbidity of vestibular symptoms and migraine.

RECENT FINDINGS

Multisensory processing and integration is a key concept for understanding mixed presentation of migraine and vestibular symptoms. Here, we discuss how vestibular migraine should be distinguished from a secondary migraine phenomenon in which migraine symptoms may coincide with or triggered by another vestibular disorder. We also have some updates on the diagnostic criteria of vestibular migraine, its pathophysiology, and common approaches used for its treatment. As a common clinical presentation of migraine and vestibular symptoms, vestibular migraine should be distinguished from a secondary migraine phenomenon, in which migraine symptoms may be triggered by or coincide with another vestibular disorder. Recent experimental evidence suggests vestibular symptoms in vestibular migraine are linked to multisensory mechanisms that control body motion and orientation in space.

A Vestibular Challenge Combined with Calcitonin Gene-Related Peptide (CGRP) Promotes Anxiety-Like Behaviors

Motion-induced anxiety and agoraphobia are more frequent symptoms in patients with vestibular migraine (VM) than migraine without vertigo. The neuropeptide calcitonin gene-related peptide (CGRP) is a therapeutic target for migraine and VM, but the link between motion hypersensitivity, anxiety, and CGRP is relatively unexplored, especially in preclinical mouse models. To further examine this link, we tested the effects of systemic CGRP and off-vertical axis rotation (OVAR) on elevated plus maze (EPM) and rotarod performance in male and female C57BL/6J mice. Rotarod ability was assessed using two different dowel diameters: mouse dowel (r = 1.5 cm) versus rat dowel (r = 3.5 cm). EPM results indicate that CGRP alone or OVAR alone did not increase anxiety indices. However, the combination of CGRP and OVAR did elicit anxiety-like behavior. On the rotarod, CGRP reduced performance in both sexes on a mouse dowel but had no effect on a rat dowel, whereas OVAR had a significant effect on the rat dowel. These results suggest that only the combination of CGRP with vestibular stimulation induces anxiety-like behavior and that CGRP affects the dynamic balance function in mice depending on the type of challenge presented. These findings suggest that anxiety-like behaviors can be teased out from imbalance behaviors in a mouse model of "migraine." Future studies are aimed to determine if CGRP receptor antagonists that have been effective treating migraineurs and mouse "migraine" models may also reduce the anxiety observed in migraine.

Loss of calcitonin gene-related peptide (αCGRP) and use of a vestibular challenge highlight balance deficiencies in aging mice

Aging impacts the vestibular system and contributes to imbalance. In fact, imbalance precedes changes in cognition in the elderly. However, research is limited in assessing aging mouse models that are deficient in crucial neuromodulators like Calcitonin Gene-Related Peptide (CGRP). We studied the loss of CGRP and its effects in the aging mouse, namely its effect on both static and dynamic imbalances. Postural sway and rotarod testing were performed before and after a vestibular challenge (VC) in the 129S wild type and the αCGRP (-/-) null mice. Four age groups were tested that correspond to young adulthood, late adulthood, middle age, and senescence in humans. Our results suggest wild type mice experience a decline in rotarod ability due to aging after they reach their prime performance at 6-10 months of age, while the αCGRP (-/-) null mice perform poorly on rotarod early in life but improve with age as they get older, potentially due to vestibular compensation. Our postural sway study suggests that a vestibular challenge can lead to significantly reduced CoP ellipse areas (freezing behaviors) in older mice, and this change occurs earlier in the αCGRP (-/-) null but requires future studies to evaluate anxiety effects. These results indicate that αCGRP is an important component of proper balance and that the loss of αCGRP can contribute to balance complications that may compound with aging.

Vestibular migraine: an update

PURPOSE OF REVIEW

We performed a narrative review of the recent findings in epidemiology, clinical presentation, mechanisms and treatment of vestibular migraine.

RECENT FINDINGS

Vestibular migraine is an underdiagnosed condition that has a high prevalence among general, headache and neuro-otology clinics. Vestibular migraine has a bimodal presentation probably associated with a hormonal component in women. These patients could have a complex clinical phenotype including concomitant autonomic, inflammatory or connective tissue conditions that have a higher prevalence of psychological symptoms, which may mistakenly lead to a diagnosis of a functional neurological disorder. A high proportion of patients with postural perceptual persistent dizziness have a migraine phenotype. Independently of the clinical presentation and past medical history, patients with the vestibular migraine phenotype can respond to regular migraine preventive treatments, including those targeting the calcitonin gene-related peptide pathways.

SUMMARY

Vestibular migraine is an underdiagnosed migraine phenotype that shares the pathophysiological mechanisms of migraine, with growing interest in recent years. A thorough anamnesis is essential to increase sensitivity in patients with unknown cause of dizziness and migraine treatment should be considered (see supplemental video-abstract).

Environmental enrichment alleviates hyperalgesia by modulating central sensitization in a nitroglycerin-induced chronic migraine model of mice

BACKGROUND

Chronic migraine (CM) is a debilitating neurofunctional disorder primarily affecting females, characterized by central sensitization. Central sensitization refers to the enhanced response to sensory stimulation, which involves changes in neuronal excitability, synaptic plasticity, and neurotransmitter release. Environmental enrichment (EE) can increase the movement, exploration, socialization and other behaviors of mice. EE has shown promising effects in various neurological disorders, but its impact on CM and the underlying mechanism remains poorly understood. Therefore, the purpose of this study was to determine whether EE has the potential to serve as a cost-effective intervention strategy for CM.

METHODS

A mouse CM model was successfully established by repeated administration of nitroglycerin (NTG). We selected adult female mice around 8 weeks old, exposed them to EE for 2 months, and then induced the CM model. Nociceptive threshold tests were measured using Von Frey filaments and a hot plate. The expression of c-Fos, calcitonin gene-related peptide (CGRP) and inflammatory response were measured using WB and immunofluorescence to evaluate central sensitization. RNA sequencing was used to find differentially expressed genes and signaling pathways. Finally, the expression of the target differential gene was investigated.

RESULTS

Repeated administration of NTG can induce hyperalgesia in female mice and increase the expression of c-Fos and CGRP in the trigeminal nucleus caudalis (TNC). Early exposure of mice to EE reduced NTG-induced hyperalgesia in CM mice. WB and immunofluorescence revealed that EE inhibited the overexpression of c-Fos and CGRP in the TNC of CM mice and alleviated the inflammatory response of microglia activation. RNA sequencing analysis identified that several central sensitization-related signaling pathways were altered by EE. VGluT1, a key gene involved in behavior, internal stimulus response, and ion channel activity, was found to be downregulated in mice exposed to EE.

CONCLUSION

EE can significantly ameliorate hyperalgesia in the NTG-induced CM model. The mechanisms may be to modulate central sensitization by reducing the expression of CGRP, attenuating the inflammatory response, and downregulating the expression of VGluT1, etc., suggesting that EE can serve as an effective preventive strategy for CM.

Phenotypes and clinical subgroups in vestibular migraine: a cross-sectional study with cluster analysis

OBJECTIVE

The aim of this multicentric cross-sectional study was to collect phenotypes and clinical variability on a large sample of 244 patients enrolled in different university centers in Italy, trying to differentiate subtypes of VM.

BACKGROUND

VM is one of the most frequent episodic vertigo characterized by a great clinical variability for duration of attacks and accompanying symptoms. Diagnosis is based only on clinical history of episodic vertigo in 50% of cases associated with migrainous headache or photo/phonophobia.

METHODS

We enrolled in different university centers 244 patients affected by definite VM according to the criteria of the Barany Society between January 2022 and December 2022. An audiometric examination and a CNS MRI were performed before inclusion. Patients with low-frequency sensorineural hearing loss were not included, as well as patients with an MRI positive otherwise that for microischemic lesions. Patients were asked to characterize vestibular symptoms choosing among (multiple answers were allowed): internal vertigo, dizziness, visuo-vestibular symptoms/external vertigo; onset of vertigo and duration, neurovegetative, and cochlear accompanying symptoms (hearing loss, tinnitus, and fullness during attacks) were collected as well as migrainous headache and/or photo/phonophobia during vertigo; autoimmune disorders were also analyzed. A bedside examination was performed including study of spontaneous-positional nystagmus with infrared video goggles, post head shaking ny, skull vibration test, and video head impulse test.

RESULTS

We included 244 subjects, 181 were females (74.2%). The age of onset of the first vertigo was 36.6 ± 14.5 while of the first headache was 23.2 ± 10.1. A positive correlation has been found between the first headache and the first vertigo. The mean duration of vertigo attacks was 11 ± 16 h. We carried on a cluster analysis to identify subgroups of patients with common clinical features. Four variables allowed to aggregate clusters: age of onset of vertigo, duration of vertigo attacks, presence of migrainous headache during vertigo, and presence of cochlear symptoms during vertigo. We identified 5 clusters: cluster 1/group 1 (23 subjects, 9.4%) characterized by longer duration of vertigo attacks; cluster 2/group 2 (52 subjects, 21.3%) characterized by absence of migrainous headache and cochlear symptoms during vertigo; cluster 3/group 3 (44 subjects, 18%) characterized by presence of cochlear symptoms during vertigo but not headache; cluster 4/group 4 (57 subjects, 23.4%) by the presence of both cochlear symptoms and migrainous headache during vertigo; cluster 5/group 5 (68 subjects, 27.9%) characterized by migrainous headache but no cochlear symptoms during vertigo.

CONCLUSION

VM is with any evidence a heterogeneous disorder and clinical presentations exhibit a great variability. In VM, both symptoms orienting toward a peripheral mechanism (cochlear symptoms) and central ones (long lasting positional non-paroxysmal vertigo) may coexist. Our study is the first published trying to characterize subgroups of VM subjects, thus orienting toward different pathophysiological mechanisms.

Vestibular Migraine Pathophysiology and Treatment: a Narrative Review

PURPOSE OF REVIEW

To review the diagnosis of vestibular migraine (VM) and update the clinician on the most recent developments in our understanding of its pathophysiology and treatment.

RECENT FINDINGS

Functional imaging studies have identified multiple regions of the brain with abnormal activity and connectivity in VM. There is evidence of abnormal sensory processing and integration in VM patients. Calcitonin gene-related peptide (CGRP) has also been found to play a role in trigeminal and vestibular nucleus pathways. Research into treatment modalities has identified several neuromodulation devices that may be effective in VM. There are a growing number of evidence-based preventive options for VM, including medications that target CGRP. VM is best understood as a sensory processing disorder. CGRP appears to play a role, and further research is needed to fully understand its effects. Treatment options are expanding, but there is still a need for more randomly controlled trials in this area.

Human RAMP1 overexpressing mice are resistant to migraine therapies for motion sensitivity: a mouse model of vestibular migraine

Both enhanced motion-induced nausea and increased static imbalance are \observed symptoms in migraine and especially vestibular migraine (VM). Motion-induced nausea and static imbalance were investigated in a mouse model, nestin/hRAMP1, expressing elevated levels of human RAMP1 in the CNS, which enhances CGRP signaling in the nervous system. Behavioral surrogates such as the motion-induced thermoregulation and postural sway center of pressure (CoP) assays were used to assess motion sensitivity. Tail vasodilation analysis revealed that this model exhibits an increased sensitivity to CGRP's effects at lower doses compared to control mice. In addition, the nestin/hRAMP1 mice exhibit a higher dynamic range in postural sway than their wildtype counterparts, along with increased sway observed in nestin/hRAMP1 male mice that was not present in male littermate controls. Results from migraine blocker experiments were challenging to interpret, but the data suggests that olcegepant is incapable of reversing CGRP-induced alterations in the nestin/hRAMP1 mice, while rizatriptan was ineffective in both the nestin/hRAMP1 and control mice. The results indicate that overexpression of hRAMP1 leads to heightened endogenous CGRP signaling. Results also suggest that both olcegepant and rizatriptan are ineffective in reducing CGRP-triggered nausea and sway in this hypersensitive CGRP mouse model. This study suggests that hypersensitivity to CGRP may be a mouse model for difficult to treat cases of vestibular migraine.

Evaluation of Vestibular Functions in a Case of Vestibular Migraine With Successful Treatment With Erenumab

This is the first report of vestibular examinations before and after the successful treatment of vestibular migraine (VM), a common cause of recurrent vertigo, with calcitonin gene-related peptide (CGRP) receptor inhibitor. We evaluated a 42-year-old female with VM and concomitant probable Meniere's disease, whose headache and dizziness have improved promptly with the administration of erenumab, a CGRP receptor inhibitor. The sensorineural hearing loss in pure-tone audiometry, dysfunctions shown in vestibular examinations (cervical and ocular vestibular evoked myogenic potentials), and mild endolymphatic hydrops shown in gadolinium-enhanced inner ear magnetic resonance imaging, all in the right ear, revealed no change compared with those observed before treatment. This case suggests that VM may be treated by blocking CGRP in the trigeminal ganglion, which suppresses the effects on the vestibular nucleus; herein, no effects were observed in the inner ear despite the clear amelioration of dizziness.

Monoclonal Antibodies Targeting CGRP: A Novel Treatment in Vestibular Migraine

Background. Monoclonal antibodies (mAbs) directed against the calcitonin gene-related peptide (CGRP) or its receptor represented the first targeted and specialized approach to migraine prophylaxis. Nevertheless, they have been rarely considered in the treatment of vestibular migraine (VM). Our aim was to evaluate the effectiveness of anti-CGRP mAbs in VM patients who did not respond to conventional migraine treatments. Methods. Consecutive VM patients treated with erenumab were considered. As a comparison, we considered the same VM patients during conventional migraine treatments (i.e., propranolol, flunarizine, or valproic acid), which were tried before mAbs therapy. Videonystagmography, the Italian version of the Dizziness Handicap Inventory (DHI) questionnaire, and migraine days over the last 3 months were evaluated in all patients before and after treatments. Results. In the present retrospective study, we included 21 female and 2 male VM patients, mean age 45.2 years. All patients underwent contrast-enhanced magnetic resonance imaging that ruled out other causes of vertigo. The DHI questionnaire significantly improved after mAb therapy (p < 0.0001). Mean migraine days over the last 3 months were significantly reduced after treatment (p = 0.001). Videonystagmography was altered in 11 (48%) patients prior to monoclonal antibodies. We found vertical positional nystagmus in 9 patients and horizontal positional nystagmus in 2 patients. After the treatment, we found vertical positional nystagmus only in 1 patient (p = 0.002). When patients were treated with conventional therapies, there was no significant reduction in DHI, and instrumental vestibular examinations remained altered. Conclusions. VM patients using anti-CGRP mAbs experienced a reduction in the dizziness-derived handicap, as reported in the DHI questionnaire. Furthermore, these treatments were significantly associated with a normalization of vestibular instrumental analysis. These findings were not seen with conventional treatments. Treatment with anti-CGRP mAbs may be effective in VM patients who did not respond to conventional migraine treatments. These findings should be tested in large, randomized clinical trials.

Both systemic Calcitonin Gene Related Peptide (CGRP) and a vestibular challenge promote anxiety-related behaviors and dynamic imbalance in mice

Motion-induced anxiety and agoraphobia are more frequent symptoms in patients with vestibular migraine than migraine without vertigo. The neuropeptide calcitonin gene-related peptide (CGRP) is a therapeutic target for migraine and vestibular migraine, but the link between motion hypersensitivity, anxiety, and CGRP is relatively unexplored, especially in preclinical mouse models. To further examine this link, we tested the effects of systemic CGRP and off-vertical axis rotation (OVAR) on elevated plus maze (EPM) and rotarod performance in male and female C57BL/6J mice. Rotarod ability was assessed using two different dowel diameters: mouse dowel (r = 1.5 cm) versus rat dowel (r = 3.5 cm). EPM results indicate CGRP increased anxiety indexes and time spent in the closed arms in females but not males, while OVAR increased anxiety indexes and time spent in the closed arms in both sexes. The combination of CGRP and OVAR elicited even greater anxiety-like behavior. On the rotarod, CGRP reduced performance in both sexes on a mouse dowel but had no effect on a rat dowel, whereas OVAR had a significant effect on the rat dowel. Rotarod performance is influenced by dowel diameter, with larger dowels presenting greater challenges on balance function. These results suggest that both CGRP and vestibular stimulation induce anxiety-like behavior and that CGRP affects dynamic balance function in mice depending on the type of challenge presented. Findings highlight the potential translation of anti-CGRP receptor signaling therapeutics for treating motion hypersensitivity and motion-induced anxiety that manifests in vestibular migraine.

Significance statement

Anxiety is very common in patients with dizziness and vestibular migraine (VM). Elevated CGRP levels have been linked to migraine symptoms of increased light and touch sensitivity in mice and humans and we wondered if a systemic injection of CGRP into mice would increase anxiety and imbalance; and if mice further exposed to a vestibular stimulus would have their anxiety measures sharpened. We observed a female preponderance in both CGRP and motion-induced anxiety-like behaviors, suggesting that the role of CGRP in migraine's anxiety symptoms can be recapitulated in the mouse. Our findings suggest that CGRP signaling has a pertinent role in motion-induced anxiety and dynamic imbalance, and warrants the potential use of anti-CGRP therapies for the treatment of these symptoms.

Impairments to the multisensory integration brain regions during migraine chronification: correlation with the vestibular dysfunction

Objectives

Migraine is often combined with vestibular dysfunction, particularly in patients with chronic migraine (CM). However, the pathogenesis of migraine chronification leading to vestibular dysfunction is not fully understood. The current study investigated whether structural or functional impairments to the brain during migraine chronification could be associated with vestibular dysfunction development.

Methods

The eligible participants underwent clinical assessment and magnetic resonance imaging (MRI) scans. Voxel-based morphometry (VBM) determined structural impairment by evaluating alterations in gray matter volume (GMV). Functional impairment was assessed by the mean amplitude of low-frequency fluctuation (mALFF). Furthermore, the resting-state functional connectivity (rsFC) of regions possessing impairment was examined with a seed-based approach. We also analyzed the correlations between altered neuroimaging features with clinical variables and performed multiple linear regression.

Results

Eighteen CM patients, 18 episodic migraine (EM) patients, and 18 healthy controls (HCs) were included in this study. A one-way ANOVA indicated the group differences in mALFF. These were located within right supramarginal gyrus (SMG), left angular gyrus (AG), middle frontal gyrus (MFG), left middle occipital gyrus (MOG), right rolandic operculum (Rol) and left superior parietal gyrus (SPG). During rsFC analysis, the CM group had more enhanced rsFC of left SPG with left MOG than the EM and HC groups. The EM group revealed enhanced rsFC of left SPG with left AG than the CM and HC groups. In multiple linear regression, after controlling for age, body mass index (BMI) and disease duration, the rsFC of left SPG with left MOG (β = 48.896, p = 0.021) was found to predict the total Dizziness Handicap Inventory (DHI) score with an explained variance of 25.1%. Moreover, the rsFC of left SPG with left MOG (β = 1.253, p = 0.003) and right SMG (β = -1.571, p = 0.049) were significant predictors of migraine frequency, accounting for a total explained variance of 73.8%.

Conclusion

The functional impairments due to migraine chronification are primarily concentrated in the multisensory integration-related brain regions. Additionally, the rsFC of SPG with MOG can predict the frequency of migraine and the degree of vestibular dysfunction. Therefore, these neuroimaging features could be potential mechanisms and therapeutic targets for developing vestibular dysfunction in migraine.

Inhibition of glutamatergic trigeminal nucleus caudalis- vestibular nucleus projection neurons attenuates vestibular dysfunction in the chronic-NTG model of migraine

BACKGROUND

Prior clinical studies suggest a shared mechanism between vestibular symptoms and migraine headache. However, the specific neuroanatomical substrate connecting vestibular symptoms with migraine remains to be largely unknown. Thus, the aim of this study was to further investigate the mechanisms that whether and how trigeminovestibular neurons produce effects on neuronal activation in vestibular nucleus (VN).

METHODS

A chronic-NTG rat model was established by recurrent intermittent administration of nitroglycerin (NTG). Pain- and vestibular-related behaviors were assessed. To selectively inhibit the glutamatergic neurons and trigeminal nucleus caudalis (TNC) to VN projection neurons, the AAVs encoding engineered Gi-coupled hM4D receptor were administered in the TNC or VN area.

RESULTS

We identify a glutamatergic projection from TNC to VN that mediates vestibular dysfunction in a chronic-NTG rat model. Inhibition of the Glutamate^TNC neurons alleviates vestibular dysfunction in the chronic-NTG rat. Calcitonin gene-related peptide (CGRP)-expressing neurons in the VN received glutamatergic projections from TNC neurons. Silencing the glutamatergic TNC-VN projection neurons attenuates vestibular dysfunction in the chronic-NTG rat.

CONCLUSIONS

Together, we reveal a modulatory role of glutamatergic TNC-VN projection neurons in vestibular dysfunction of migraine.

Activation of the microglial P2X7R/NLRP3 inflammasome mediates central sensitization in a mouse model of medication overuse headache

Background

Excessive use of headache treatments often leads to the development, progression and exacerbation of primary headache, which is defined as medication overuse headache (MOH). A significant pathophysiological mechanism of MOH is central sensitization. Recent evidence suggests that central sensitization in chronic headache is a result of inflammatory responses mediated by microglial activation in the trigeminal nucleus caudalis (TNC). However, it is unknown whether microglial activation has an impact on the central sensitization of MOH. Accordingly, the goal of this research was to determine how microglial activation and the P2X7R/NLRP3 inflammasome signaling pathway in the TNC contribute to the pathogenesis of MOH.

Methods

Repeated intraperitoneal injection of sumatriptan (SUMA) was used to establish a mouse model of MOH. Basal mechanical hyperalgesia was evaluated using von Frey filaments. As central sensitization biomarkers, the c-Fos and CGRP expression levels were measured by immunofluorescence analysis. We estimated the expression of microglial biomarkers (Iba1 and iNOS) within the TNC by qRT-PCR, western blotting and immunofluorescence analysis. To elucidate the effect of microglial activation and the P2X7/NLRP3 signaling pathway on central sensitization in MOH, we evaluated whether the microglia-specific inhibitor minocycline, the P2X7R-specific antagonist BBG and the NLRP3-specific inhibitor MCC950 altered SUMA-caused mechanical hyperalgesia. Furthermore, we examined c-Fos and CGRP expression within the TNC following individual injections of these inhibitors.

Results

Repeated SUMA injection induced basal mechanical hyperalgesia, increased c-Fos and CGRP levels, and activated microglia within the TNC. Inhibiting microglial activation with minocycline prevented the emergence of mechanical hyperalgesia and cut down c-Fos and CGRP expression. Immunofluorescence colocalization analysis revealed that P2X7R was predominantly co-localized with microglia. The levels of P2X7R and the NLRP3 inflammasome were elevated by repeated SUMA injection, and blocking P2X7R and NLRP3 inhibited mechanical hyperalgesia and cut down c-Fos and CGRP expression within the TNC.

Conclusion

Based on the current findings, inhibiting microglial activation could reduce central sensitization caused by chronic SUMA treatment via the P2X7R/NLRP3 signaling pathway. The clinical management of MOH may benefit from a novel strategy that inhibits microglial activation.

Phenotypes, bedside examination, and video head impulse test in vestibular migraine of childhood compared with probable vestibular migraine and recurrent vertigo in childhood

Introduction

Vestibular impairment and vertigo in the pediatric population have an estimated prevalence ranging between 0.4% and 5.6% and are a topic of interest in recent years. The Bárány Society has recently reclassified migraine-related vertigo syndromes as vestibular migraine of childhood (VMC), probable vestibular migraine of childhood (probable VMC), and recurrent vertigo of childhood (RVC).

Methods

Applying the criteria established by the Bárány Society, we retrospectively analyzed data on 95 pediatric patients suffering from episodic vertigo that were recruited from 2018 to 2022. In applying the revised criteria, 28 patients had VMC, 38 had probable VMC, and 29 had RVC.

Results

Visuo-vestibular symptoms (external vertigo) or internal vertigo were reported by 20 of 28 VMC patients (71.4%) compared to 8 of 38 probable VMC patients (21%) (P < .001). None of the RVC patients reported external vertigo. Duration of vertigo was demonstrably longer in the VMC patients than in the probable VMC (P < .001) and RVC (P < .001) patients. Cochlear symptoms were reported by 28.6% of VMC patients and by 13.1% of probable VMC patients. No cochlear symptoms were reported by any RVC patients. Familial cases for headache and episodic vertigo showed no significant difference between groups.

Discussion

The most frequent finding during bedside examination in all three groups was central positional nystagmus. Differences in the duration of attacks and in accompanying symptoms may underline different pathophysiological mechanisms.

The Importance of the Diaphragm in Neuromotor Function in the Patient with Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a constant and chronic narrowing of the respiratory airways, with numerous associated symptoms, not always related to the pathological adaptation of the lungs. Statistical projections show that COPD could become the third leading cause of death globally by 2030, with a significant increase in deaths by 2060. Skeletal muscle dysfunction, including the diaphragm, is one of the causes linked to the increase in mortality and hospitalization. Little emphasis is given by the scientific literature to the importance of the diaphragm towards functional neuromotor pathological expressions. The article reviews the adaptation of the skeletal muscles, with greater attention to the adaptations of the diaphragm, thereby highlighting the non-physiological variations that the main respiratory muscle undergoes and the neuromotor impairment found in COPD. The text could be an important reflection from a clinical and rehabilitation point of view, to direct greater attention to the function and adaptation of the diaphragm muscle.

The plasma fibrinogen levels in the nitroglycerin-induced chronic migraine rat model and its association between migraine-associated vestibular dysfunction

The purpose of this study was to measure the vestibular function and plasma fibrinogen level in the nitroglycerin (NTG)-induced chronic migraine rats, and explore the effect of defibrinogenation on migraine and associated vestibular dysfunction. The chronic migraine rat model was built by recurrent NTG injection. Batroxobin was administrated as a defibrinogenating drug. We measured the mechanical withdrawal threshold, vestibular function, and fibrinogen level of the rats 30 min before and 2 h following the model establishment, as well as 1 h after batroxobin administration. The results showed that vestibular function was impaired in NTG-induced chronic migraine rats. The fibrinogen levels were increased following repeated NTG injections. However, defibrinogenation did not affect either aggravating or alleviating mechanical hyperalgesia or vestibular dysfunction in the migraine model rats. These findings suggest that the NTG-induced chronic migraine rat model can be used for research on migraine-associated vestibular symptoms. Albeit the association between elevated fibrinogen levels and migraine attacks can be observed, the role of excessive fibrinogen in the pathogenesis of chronic migraine is yet to be determined.

Broadening vestibular migraine diagnostic criteria: A prospective cohort study on vestibular migraine subtypes

BACKGROUND

Current Bárány Society criteria for vestibular migraine (VM) include only episodic symptoms. Anecdotal observations suggest that some patients have episodic forms and others have chronic forms of VM, with interplay and evolution of both subtypes over time.

OBJECTIVE

To better understand VM subtypes and evaluate a more inclusive diagnostic schema.

METHODS

Four VM groups were studied: definite episodic (dVM), probable episodic (pVM), definite chronic (dCVM), and probable chronic (pCVM). Chronic VM was defined as having more than 15 dizzy days per month. Sociodemographic and clinical characteristics were analyzed, along with Dizziness Handicap Inventory (DHI) and Vestibular Migraine Patient Assessment Tool and Handicap Inventory (VM-PATHI) scores.

RESULTS

54 adults with a mean age of 47.0 years (SD 13.7) were enrolled. 10 met criteria for dVM, 11 pVM, 22 dCVM, and 11 pCVM. Overall, there were strong similarities in clinical characteristics between dVM, pVM, dCVM, and pCVM. Compared to subjects with episodic VM, those with chronic VM had a higher average number of VM triggers (8.7 vs. 6.4, P = 0.019), including motion (93.9% vs. 66.7%, P = 0.009), scrolling on a screen (78.8% vs. 47.6%, P = 0.018), skipped meal (57.6% vs. 23.8%, P = 0.015), and air travel (57.6% vs. 23.8%, P = 0.015). They also had higher symptom severity (DHI = 53.3, P = 0.194) and burden of disease (VM-PATHI = 48.2, P = 0.030) scores.

CONCLUSIONS

Many patients do not meet current Bárány Society criteria for VM based on their duration of vestibular symptoms. Yet, these patients with chronic VM endorse several indistinguishable symptoms from those who do meet criteria. A more inclusive diagnostic schema should be adopted where patients with vestibular symptoms shorter than 5 minutes or longer than 72 hours are also recognized as having VM.

Vestibular Migraine

PURPOSE OF REVIEW

To explore recent developments in vestibular migraine (VM).

RECENT FINDINGS

This review discusses the current diagnostic criteria for VM in the adult and pediatric populations, as proposed by the International Headache Society and Bárány Society. Recent VM studies confirm the prior findings and reveal new insights, including the wide range of vestibular symptoms, symptoms in the attack-free period, and triggers. Many patients experience persistent vestibular symptoms, even in the absence of acute attacks, which often significantly impact patients' quality of life. The syndrome of benign recurrent vertigo and its relationship to migraine, VM, and Meniere's disease is also discussed. There is a dearth of randomized controlled trials in VM treatment. Prospective and retrospective studies support the benefit of many migraine treatments are effective in VM, including neuromodulation, and calcitonin gene-related peptide monoclonal antibodies. VM affects almost 3% of the population, but remains under-diagnosed. Recent diagnostic criteria can help clinicians diagnose VM in adults and children.

A c-Fos activation map in nitroglycerin/levcromakalim-induced models of migraine

Background

Chronic migraine is a common and highly disabling disorder. Functional MRI has indicated that abnormal brain region activation is linked with chronic migraine. Drugs targeting the calcitonin gene-related peptide (CGRP) or its receptor have been reported to be efficient for treating chronic migraine. The CGRP signaling was also shared in two types of chronic migraine models (CMMs). However, it remains unclear whether the activation of specific brain regions could contribute to persistent behavioral sensitization, and CGRP receptor antagonists relieve migraine-like pain in CMMs by altering specific brain region activation. Therefore, it’s of great interest to investigate brain activation pattern and the effect of olcegepant (a CGRP receptor-specific antagonist) treatment on alleviating hyperalgesia by altering brain activation in two CMMs, and provide a reference for future research on neural circuits.

Methods

Repeated administration of nitroglycerin (NTG) or levcromakalim (LEV) was conducted to stimulate human migraine-like pain and establish two types of CMMs in mice. Mechanical hypersensitivity was evaluated by using the von Frey filament test. Then, we evaluated the activation of different brain regions with c-Fos and NeuN staining. Olcegepant was administered to explore its effect on mechanical hyperalgesia and brain region activation.

Results

In two CMMs, acute and basal mechanical hyperalgesia was observed, and olcegepant alleviated mechanical hyperalgesia. In the NTG-induced CMM, the medial prefrontal cortex (mPFC), anterior cingulate cortex (ACC), and the caudal part of the spinal trigeminal nucleus (Sp5c) showed a significant increase of c-Fos expression in the NTG group (p < 0.05), while pre-treatment with olcegepant reduced c-Fos expression compared with NTG group (p < 0.05). No significant difference of c-Fos expression was found in the paraventricular thalamic nucleus (PVT) and ventrolateral periaqueductal gray (vlPAG) between the vehicle control and NTG group (p > 0.05). In the LEV-induced CMM, mPFC, PVT, and Sp5c showed a significant increase of c-Fos expression between vehicle control and LEV group, and olcegepant reduced c-Fos expression (p < 0.05). No significant difference in c-Fos expression was found in vlPAG and ACC (p > 0.05).

Conclusions

Our study demonstrated the activation of mPFC and Sp5c in two CMMs. Olcegepant may alleviate hyperalgesia of the hind paw and periorbital area by attenuating brain activation in CMMs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01496-8.

Study of clinical correlation of motion sickness in patients with vestibular migraine

Objective

In this study, clinical data from vestibular migraine (VM) patients and healthy control populations were collected to analyze the clinical data of VM patients, especially the history of motion sickness, and to understand their clinical characteristics.

Methods

According to VM diagnostic criteria, 140 patients diagnosed with confirmed VM (cVM) and probable VM (pVM) who attended the outpatient and inpatient ward of Jiaxing First Hospital between August 2017 and June 2021, as well as 287 healthy check-ups in the health management center, were analyzed and compared in terms of age, gender, and previous history of motion sickness.

Results

A comparison of clinical data related to VM patients and the control population showed that there were more women in the VM group (P < 0.01) and that patients in the VM group were older (P < 0.05) and had a higher prevalence of history of motion sickness history (P < 0.01). Analysis after matching gender and age revealed that patients in the cVM group were older than those in the pVM group (P < 0.05), but the proportion of motion sickness was lower than in the pVM group (P < 0.05). The age of the patients in the cVM group was mainly distributed around 50 years of age, following a normal distribution, whereas the age distribution of the patients in the pVM group did not have a significant trend of age concentration and was distributed at all ages.

Conclusion

The history of motion sickness is significant in patients with VM and may be a potential suggestive factor for the diagnosis of VM.

Calcitonin gene-related peptide receptor antagonist BIBN4096BS regulates synaptic transmission in the vestibular nucleus and improves vestibular function via PKC/ERK/CREB pathway in an experimental chronic migraine rat model

Background

Vestibular symptoms are frequently reported in patients with chronic migraine (CM). However, whether vestibular symptoms arise through overlapping neurobiology of migraine remains to be elucidated. The neuropeptide calcitonin gene-related peptide (CGRP) and CGRP1 receptor play important pathological roles in facilitating central sensitization in CM. Therefore, we aimed to investigate whether CGRP1 receptor contributes to vestibular dysfunction after CM by improving synaptic transmission in the vestibular nucleus (VN).

Methods

A CM rat model was established by recurrent intermittent administration of nitroglycerin (NTG). Migraine- and vestibular-related behaviors were assessed. CGRP1 receptor specific antagonist, BIBN4096BS, and protein kinase C (PKC) inhibitor chelerythrine chloride (CHE) were administered intracerebroventricularly. The expressions of CGRP and CGRP1 receptor components, calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) were evaluated by western blot, immunofluorescent staining and quantitative real-time polymerase chain reaction in the vestibular nucleus (VN). Synaptic associated proteins and synaptic morphological characteristics were explored by western blot, transmission electron microscope, and Golgi-cox staining. The expressions of PKC, phosphorylated extracellular signal regulated kinase (p-ERK), phosphorylated cAMP response element-binding protein at serine 133 site (p-CREB-S133) and c-Fos were detected using western blot or immunofluorescent staining.

Results

The expressions of CGRP, CLR and RAMP1 were significantly upregulated in CM rats. CLR and RAMP1 were expressed mainly in neurons. BIBN4096BS treatment and PKC inhibition alleviated mechanical allodynia, thermal hyperalgesia and vestibular dysfunction in CM rats. Additionally, BIBN4096BS treatment and PKC inhibition markedly inhibited the overexpression of synaptic associated proteins and restored the abnormal synaptic structure in VN after CM. Furthermore, BIBN4096BS treatment dysregulated the expression levels of PKC, p-ERK and p-CREB-S133, and attenuated neuronal activation in VN after CM.

Conclusions

The present study demonstrated that CGRP1 receptor inhibition improved vestibular function after CM by reversing the aberrant synaptic transmission via downregulating PKC/ERK/CREB signaling pathway. Therapeutic interventions by inhibiting CGRP/CGRP1 signaling may be a new target for the treatment of vestibular symptoms in CM.

New Anti-CGRP Medications in the Treatment of Vestibular Migraine

Background

Vestibular migraine (VM) is a condition associated with migraine headache, vertigo, dizziness, and balance disturbances. Treatment options are limited. It is unknown if new calcitonin gene-related peptide (CGRP) migraine medications have efficacy in treating VM.

Methods

We retrospectively reviewed all patients with VM who were prescribed one of the new CGRP medications between January 2016 and July 2020. In total, 28 patients met the inclusion criteria. We specifically evaluated the “older” CGRP medications including erenumab, galcanezumab, fremanezumab, and ubrogepant. Medical records for subsequent visits were assessed to monitor improvement described by patients.

Results

Of the 28 patients identified, three were lost to follow up. For the remaining 25 patients, we divided the patients based on a scale of “significant improvement,” “moderate improvement,” “mild improvement,” or “no improvement.” In total 21 of 25 patients demonstrated some level of improvement in their VM symptoms with 15 having moderate to significant improvement.

Conclusion

Results demonstrated a trend toward improvement, suggesting that the CGRP medications appear to be a decent treatment option for VM. A prospective study evaluating CGRP medications in patients with VM would provide further information about this treatment option.

Care Gaps and Recommendations in Vestibular Migraine: An Expert Panel Summit

Vestibular migraine (VM) is an increasingly recognized pathology yet remains as an underdiagnosed cause of vestibular disorders. While current diagnostic criteria are codified in the 2012 Barany Society document and included in the third edition of the international classification of headache disorders, the pathophysiology of this disorder is still elusive. The Association for Migraine Disorders hosted a multidisciplinary, international expert workshop in October 2020 and identified seven current care gaps that the scientific community needs to resolve, including a better understanding of the range of symptoms and phenotypes of VM, the lack of a diagnostic marker, a better understanding of pathophysiologic mechanisms, as well as the lack of clear recommendations for interventions (nonpharmacologic and pharmacologic) and finally, the need for specific outcome measures that will guide clinicians as well as research into the efficacy of interventions. The expert group issued several recommendations to address those areas including establishing a global VM registry, creating an improved diagnostic algorithm using available vestibular tests as well as others that are in development, conducting appropriate trials of high quality to validate current clinically available treatment and fostering collaborative efforts to elucidate the pathophysiologic mechanisms underlying VM, specifically the role of the trigemino-vascular pathways.

Emodin Interferes With Nitroglycerin-Induced Migraine in Rats Through CGMP-PKG Pathway

The purpose of this research was to explore the effect and mechanism of emodin in interfering with nitroglycerin-induced migraine rats. We carried out behavioral research within 2 h post-nitroglycerin (NTG) injection, and blood samples were collected through the abdominal aorta for measurements of nitric oxide (NO), calcitonin gene-related peptide (CGRP), substance P (SP), tumor necrosis factor (TNF-α) and cyclic guanosine monophosphate (cGMP) levels. Immunohistochemistry was adopted to detect the activation of c-Fos immunoreactive neurons in brain tissues. The number and integrated optical density (IOD) of c-Fos positive cells were measured using Image-Pro Plus. Western blotting was applied to detect the levels of PKG protein in rat brain tissues. The results showed that emodin can alleviate the pain response of migraine rats and significantly reduce the levels of NO, CGRP, SP, TNF-α and cGMP in migraine rats. In addition, emodin can significantly reduce the number of c-Fos positive cells and the IOD value. Moreover, the expression of PKG protein was significantly inhibited by emodin. Therefore, it is inferred that emodin can relieve migraine induced by NTG through the cGMP-PKG pathway, and can be used as a potential botanical medicine for the treatment of migraine.

Biomimetic chitosan scaffolds with long-term controlled release of nerve growth factor repairs 20-mm-long sciatic nerve defects in rats

Although autogenous nerve transplantation is the gold standard for treating peripheral nerve defects of considerable length, it still has some shortcomings, such as insufficient donors and secondary injury. Composite chitosan scaffolds loaded with controlled release of nerve growth factor can promote neuronal survival and axonal regeneration after short-segment sciatic nerve defects. However, the effects on extended nerve defects remain poorly understood. In this study, we used chitosan scaffolds loaded with nerve growth factor for 8 weeks to repair long-segment (20 mm) sciatic nerve defects in adult rats. The results showed that treatment markedly promoted the recovery of motor and sensory functions. The regenerated sciatic nerve not only reconnected with neurons but neural circuits with the central nervous system were also reconstructed. In addition, the regenerated sciatic nerve reconnected the motor endplate with the target muscle. Therefore, this novel biomimetic scaffold can promote the regeneration of extended sciatic nerve defects and reconstruct functional circuits. This provides a promising method for the clinical treatment of extended peripheral nerve injury. This study was approved by the Animal Ethics Committee of Capital Medical University, China (approval No. AEEI-2017-033) on March 21, 2017.

Detecting Abnormal Neuronal Activity in a Chronic Migraine Model by Egr1-EGFP Transgenic Mice

Chronic migraine (CM) is a highly disabling neurological disorder characterized by recurrent headache accompanied by a variety of sensory and/or emotional symptoms. However, the mechanisms of migraine onset and its chronicity have not been elucidated. The present study was designed to search for brain regions and neurons that were abnormally activated by CM and might be related to its pathogenesis and different concomitant symptoms. CM models were established here by repeated intraperitoneal injection of nitroglycerin (NTG) every other day for 9 days to early growth response gene 1 (Egr1)-enhanced green fluorescent protein (EGFP) transgenic mice, which allowed monitoring of neuronal activities in the whole brain. CM-related behaviors were recorded through head grooming test and light aversion assay. Elevation of Egr1 expression signals was detected in trigeminal nucleus caudalis (TNC), primary somatosensory cortex (SSp), lateral amygdala nucleus (LA), primary visual area (VISp), and temporal association areas (TEa) 2 h after the last injection of NTG by immunofluorescence and digital slice scanning technology. Meanwhile, no change of Egr1 expression was found in auditory areas (AUD), CA1, ectorhinal area (ECT), piriform (PIR), and anterior cingulate area (ACC). Furthermore, with the strongest support by evidence-based medicine among the current limited oral treatments of CM, topiramate was administrated every day for 11 days from 2 days before the first NTG injection. The results showed that topiramate partially improved the photophobia behavior of CM models in the short-term with gradually weakened efficacy as the course of the disease prolonged. Meanwhile, NTG-induced increase in Egr1 expression was completely reversed in TNC, SSp, and VISp and partially reduced in LA and TEa by topiramate at the same time point mentioned above. In conclusion, the current results suggested that the abnormal hyperactivities in TNC, SSp and VISp were associated with the pathogenesis of CM.

Insulin-like growth factor-1 inhibits nitroglycerin-induced trigeminal activation of oxidative stress, calcitonin gene-related peptide and c-Fos expression

Migraineurs experience increased oxidative stress which drives the initiation and maintenance of migraine-related pain in animal models and, by extension, migraine in humans. Oxidative stress augments calcitonin gene-related peptide (CGRP) levels, a mediator of migraine pain. Insulin-like growth factor-1 (IGF-1), a neuroprotective growth factor, reduces susceptibility to spreading depression, a preclinical model of migraine, in cultured brain slices by blocking oxidative stress and neuroinflammation from microglia. Similarly, nasal delivery of IGF-1 inhibits spreading depression in vivo. After recurrent cortical spreading depression, nasal administration of IGF-1 also significantly reduces trigeminal ganglion oxidative stress and CGRP levels as well as trigeminocervical c-Fos activation. Here, we probed for the impact of nasal IGF-1 pretreatment on trigeminal system activation using a second well-established preclinical model of migraine, systemic nitroglycerin injection. Adult male rats were treated with one of three doses of IGF-1 (37.5, 75 or 150 μg) and the optimal dose found in males was subsequently used for treatment of female rats. One day later, animals received an intraperitoneal injection of nitroglycerin. Measurements taken two hours later after nitroglycerin alone showed increased surrogate markers of trigeminal activation - oxidative stress and CGRP in the trigeminal ganglion and c-Fos in the trigeminocervical complex compared to vehicle control. These effects were significantly reduced at all doses of IGF-1 for trigeminal ganglion metrics of oxidative stress and CGRP and only at the lowest dose in both males and females for c-Fos. The latter inverted U-shaped or hormetic response is seen in enzyme-targeting drugs. While the specific mechanisms remain to be explored, our data here supports the ability of IGF-1 to preserve mitochondrial and antioxidant pathway homeostasis as means to prevent nociceptive activation in the trigeminal system produced by an experimental migraine model.

Exploring the Link Between Dry Eye and Migraine: From Eye to Brain

Dry eye and migraine are common diseases with large societal and economic burdens that have recently been associated in the literature. This review outlines the link between dry eye and migraine, which may have implications for reducing their respective burdens. We highlight possible shared pathophysiology, including peripheral and central sensitization, as the potential link between dry eye and migraine. Finally, therapies targeting similar pathophysiological mechanisms between dry eye and migraine are discussed.