Colocalization of 5-HT1F receptor and calcitonin gene-related peptide in rat vestibular nuclei

Evaluation of Cochlear Symptoms in Migraine Patients without Vestibular Migraine and/or Ménière's Disease

Migraine pathogenic pathways may selectively target the cochlea. A qualitative and quantitative analysis of cochlear symptoms in migraine patients without vestibular migraine and/or Méniere's disease was conducted. We examined 60 consecutive patients with history of cochlear symptoms, including fullness, tinnitus, and hearing loss. Patients were divided into two groups based on migraine history: M (migraine) and nM (no migraine). The incidence of migraine was compared to a homogeneous control group with dysfunctional and inflammatory dysphonia without cochlear symptoms. The type, time of onset, recurrence, bilaterality of symptoms, and hearing threshold were analyzed. The incidence of migraine was significantly higher (p = 0.04) in patients with cochlear symptoms than in the control group. The onset of symptoms is significantly earlier (p < 0.05) in the presence of migraine. The fullness, recurrence, and bilaterality of symptoms are associated with migraine in a statistically significant way (p < 0.05). Pure tone audiometry shows a statistically significant increase in the hearing threshold (500-1000 Hz) in group M. Based on developing findings, cochlear migraine may be considered as a novel clinical entity, like vestibular migraine. It would be the expression, in the absence of vertiginous symptoms, of a selective suffering of the anterior labyrinth by known operating mechanisms of 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.

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.

Saccular functions differ for Meniere's disease with and without coexisting headaches

Objectives

To elucidate the differences between the cases of Meniere's disease (MD) with and without coexisting headaches, especially migraine. The clinical characteristics and vestibular functions are compared.

Subjects

Fifteen patients with definite unilateral MD without headaches (MD/H-; 10 males and 5 females; mean age of 55.8 years), and 20 patients with definite unilateral MD with headaches (MD/H+; 3 males and 17 females; mean age of 54.4 years; 15 cases of migraine without aura and 5 cases of suspected migraine or tension-type headache) were enrolled.

Methods

The medical records, caloric test results, and cervical vestibular evoked myogenic potential (cVEMP) of the patients were reviewed. A monothermal caloric test by injection of cold water was performed, and canal paresis was assessed. cVEMP was recorded using 500 Hz short tone bursts, and the asymmetry ratio using the corrected amplitude of p13-n23 was determined.

Results

The patients in the MD/H- group were predominantly male, whereas more female patients were seen in MD/H+ group (p = 0.004). In the MD/H+ group, the frequency of vertigo and the dizziness handicap inventory (DHI) values were significantly higher than those in the MD/H- group (p = 0.045, <0.001, respectively). There was no statistical difference in the ages, duration of illness, or the hearing levels between both groups. The caloric testing results were abnormal for 10 of the 13 MD/H- cases, and 14 of the 16 MD/H+ cases, which revealed no significant difference between both groups. The cVEMP results revealed positive saccular dysfunction based on the asymmetry ratio of 4 of the 15 MD/H- cases, and 14 of the 20 MD/H+ cases; it was significantly more prevalent in the MD/H+ group than in the MD/H- group (p = 0.018). Multivariate analysis of sex, frequency of vertigo, DHI, and cVEMP results showed significant differences only in the cVEMP results (p = 0.049).

Conclusion

The present study revealed differences in patients with MD depending on the presence or absence of headaches. MD without headaches showed a significant male preponderance. MD with coexisting headaches was more associated with severe saccular dysfunctions than MD without headaches. Concomitant headache may affect the manifestations of the vestibular function, especially in the sacculus, in MD cases.

The Relationship Between Patent Foramen Ovale and Unexplained Dizziness: A Prospective Analysis in China

Introduction

Patent foramen ovale (PFO) is potentially associated with abnormal embolisms, and it results in mixing of arteriovenous blood when its right-to-left shunt (RLS) emerges. Present studies have found that PFO is a risk factor that can lead to many diseases. However, few studies have examined the relationship between PFO and dizziness.

Methods

This study was a large single-center, prospective, controlled study. From March 2019 to March 2021, we recruited patients with dizziness were divided into two groups: "explained" and "unexplained". All patients were submitted to contrast-enhanced transcranial Doppler ultrasound and screened for PFO. Transesophageal heart ultrasound or right heart catheterization was used to confirm PFO. Additionally, multiple factors were collected and statistical analysis was performed between the two groups.

Results

Among the 244 patients included, 123 were in the "explained" group and 121 were in the "unexplained" group. The prevalence of PFO in the "explained" group was 34 (27.4%) compared to 79 (64.7%) in the "unexplained" group. In the "explained" group, 7 were RLS level IV, 6 were level III, 7 were level II, and 14 were level I. For the "unexplained" group, the numbers of patients with levels IV, III, II and I were 27, 26, 12 and 14, respectively. Univariate analysis revealed that PFO (χ2= 34.77, P < 0.001) and age (t = -3.49, P < 0.001) seemed to be potential risk factor candidates for "unexplained" dizziness. In multiple regression analysis, age (OR = 0.97; 95% CI 0.95-0.99) and the prevalence of PFO (OR = 4.37; 95% CI 2.50-7.63) were statistically significant. Massively shunted PFO showed more pronounced risk factors (OR = 8.76; 95% CI 4.04-19.03).

Conclusion

There was a high prevalence of PFO and a greater RLS level in unexplained dizziness. PFO and age were independent risk factors for unexplained dizziness. When treating with unexplained dizziness, especially among young people, we must pay attention to the presence of PFO.

Endolymphatic hydrops presumption tests for patients with vestibular migraine

BACKGROUND

The aetiology of vestibular migraine (VM) has not yet been defined; endolymphatic hydrops (EH) has been suggested as a candidate.

OBJECTIVES

This study aimed to clarify the relationship between VM and EH using neuro-otological tests, including the EH presumption test.

MATERIALS AND METHODS

Fourteen patients with VM underwent caloric testing, video head impulse test (vHIT), cervical and ocular vestibular evoked myogenic potential (cVEMP and oVEMP), and EH presumption tests such as the Futaki's test and furosemide loading VEMP.

RESULTS

Caloric testing was abnormal in two of the 14 cases (14.3%), and vHIT was abnormal in one of 12 cases (8.3%). Abnormal asymmetry ratios (ARs) of cVEMP and oVEMP were observed in two of 14 cases (14.3%) and six of 13 cases (46.2%), respectively. Futaki's test results were positive in five of 14 cases (35.7%). Furosemide loading VEMP was positive in seven of 14 cases (50.0%). Nine patients (64.3%) were positive for at least one EH presumption test.

CONCLUSIONS AND SIGNIFICANCE

EH is not a rare finding in VM; however, the ratio is less than that in Meniere's disease.

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.

Differences in the Structure and Function of the Vestibular Efferent System Among Vertebrates

The role of the mammalian vestibular efferent system in everyday life has been a long-standing mystery. In contrast to what has been reported in lower vertebrate classes, the mammalian vestibular efferent system does not appear to relay inputs from other sensory modalities to the vestibular periphery. Furthermore, to date, the available evidence indicates that the mammalian vestibular efferent system does not relay motor-related signals to the vestibular periphery to modulate sensory coding of the voluntary self-motion generated during natural behaviors. Indeed, our recent neurophysiological studies have provided insight into how the peripheral vestibular system transmits head movement-related information to the brain in a context independent manner. The integration of vestibular and extra-vestibular information instead only occurs at next stage of the mammalian vestibular system, at the level of the vestibular nuclei. The question thus arises: what is the physiological role of the vestibular efferent system in mammals? We suggest that the mammalian vestibular efferent system does not play a significant role in short-term modulation of afferent coding, but instead plays a vital role over a longer time course, for example in calibrating and protecting the functional efficacy of vestibular circuits during development and aging in a role analogous the auditory efferent system.

Therapeutic targeting of nitroglycerin-mediated trigeminovascular neuronal hypersensitivity predicts clinical outcomes of migraine abortives

ABSTRACT

Cranial hypersensitivity is a prominent symptom of migraine, exhibited as migraine headache exacerbated with physical activity, and cutaneous facial allodynia and hyperalgesia. The underlying mechanism is believed to be, in part, activation and sensitization of dural-responsive trigeminocervical neurons. Validated preclinical models that exhibit this phenotype have great utility for understanding putative mechanisms and as a tool to screen therapeutics. We have previously shown that nitroglycerin triggers cranial allodynia in association with migraine-like headache, and this translates to neuronal cranial hypersensitivity in rats. Furthermore, responses in both humans and rats are aborted by triptan administration, similar to responses in spontaneous migraine. Here, our objective was to study the nitroglycerin model examining the effects on therapeutic targets with newly approved treatments, specifically gepants and ditans, for the acute treatment of migraine. Using electrophysiological methods, we determined changes to ongoing firing and somatosensory-evoked cranial sensitivity, in response to nitroglycerin, followed by treatment with a calcitonin gene-related peptide receptor antagonist, gepant (olcegepant), a 5-HT1F receptor agonist, ditan (LY344864), and an NK1 receptor antagonist (GR205171). Nitroglycerin induced activation of migraine-like central trigeminocervical neurons, and intracranial and extracranial neuronal hypersensitivity. These responses were aborted by olcegepant and LY344864. However, GR205171, which failed in clinical trial for both abortive and preventive treatment of migraine, had no effect. These data support the nitroglycerin model as a valid approach to study cranial hypersensitivity and putative mechanisms involved in migraine and as a screen to dissect potentially efficacious migraine therapeutic targets.

Lasmiditan inhibits calcitonin gene-related peptide release in the rodent trigeminovascular system

Lasmiditan, an antimigraine drug with selective 5-HT_1F receptor affinity, prejunctionally inhibits calcitonin gene-related peptide release in peripheral and central trigeminal nerve terminals of rodents.

Migraine headache pathophysiology involves trigeminovascular system activation, calcitonin gene-related peptide (CGRP) release, and dysfunctional nociceptive transmission. Triptans are 5-HT_1B/1D/(1F) receptor agonists that prejunctionally inhibit trigeminal CGRP release, but their vasoconstrictor properties limit their use in migraine patients with cardiovascular disease. By contrast, lasmiditan is a novel antimigraine and selective 5-HT_1F receptor agonist devoid of vasoconstrictor properties. On this basis, this study has investigated the modulation of trigeminal CGRP release by lasmiditan. For this purpose, we have comparatively analysed the inhibition of several components of the trigeminovascular system induced by lasmiditan and sumatriptan through: ex vivo KCl-induced CGRP release from isolated dura mater, trigeminal ganglion, and trigeminal nucleus caudalis of mice; and in vivo dural vasodilation in the rat closed-cranial window model induced by endogenous (electrical stimulation and capsaicin) and exogenous CGRP. The ex vivo release of CGRP was similarly inhibited by sumatriptan and lasmiditan in all trigeminovascular system components. In vivo, intravenous (i.v.) lasmiditan or higher doses of sumatriptan significantly attenuated the vasodilatory responses to endogenous CGRP release, but not exogenous CGRP effects. These data suggest that lasmiditan prejunctionally inhibits CGRP release in peripheral and central trigeminal nerve terminals. Because lasmiditan is a lipophilic drug that crosses the blood–brain barrier, additional central sites of action remain to be determined.

Rational Use of Lasmiditan for Acute Migraine Treatment in Adults: A Narrative Review

PURPOSE

This narrative review provides an update on the research that led to the development of ditans and lasmiditan for the acute treatment of migraine in adults and discusses the potential advantages and disadvantages of lasmiditan in clinical use.

METHODS

The electronic databases PubMed, Scopus, and ClinicalTrials.gov were searched from database inception through January 9, 2021, to identify relevant studies. Search results were assessed for their overall relevance to this review.

FINDINGS

Because part of the effect of the triptans is mediated by the serotonin 1F receptors, which are not present in the smooth muscle, a pure agonist of these receptors, lasmiditan, was developed. Lasmiditan is hypothesized to act on antinociceptive pathways and inhibit the calcitonin gene-related peptide release. Lasmiditan was approved by the US Food and Drug Administration in 2019 based on the results of 2 pivotal trials that found a significant difference from placebo in the percentage of patients who achieved freedom from pain and most bothersome symptom at 2 h. The main concern of lasmiditan derives from its central nervous system-related adverse effects, mainly dizziness and paraesthesia, probably attributable to its high blood brain barrier penetration. These central nervous system adverse effects impair driving performance for hours and might be suboptimal for individuals with migraine who want to quickly stop the migraine attack to resume their activities as soon as possible.

IMPLICATIONS

Despite the advantage of being beneficial in the acute treatment of migraine without vasocostrictive action, lasmiditan also presents limitations, in particular the central nervous system adverse effects. Moreover, head-to-head trials against triptans and gepants are indispensable to determine the better option for patients.

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.

The potential of lasmiditan in migraine

Lasmiditan, a highly selective 5-hydroxytryptamine receptor 1F (5-HT_1F) agonist, is the first drug in its class and is lacking triptan-like vasoactive properties. The US Food and Drug Administration (FDA) has recently approved lasmiditan for the acute treatment of migraine in adults based on positive results of two pivotal phase III trials, which showed a significant difference to placebo in the proportion of patients achieving total migraine freedom within 2 h. More patients with lasmiditan achieved headache freedom and, in addition, freedom from the most bothersome symptom, that is, photophobia, than with placebo. Treatment-related side effects seem to be related to the rapid penetration of the drug into the brain and include dizziness, paresthesia and drowsiness, mostly of mild to moderate intensity. Interim results from an ongoing long-term phase III trial suggest a decrease in the frequency of adverse events after multiple lasmiditan use. Lasmiditan is a promising acute anti-migraine therapy, in particular for patients with cardiovascular risk factors, contraindications, or unwanted side effects to triptans.

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

Background

Vestibular migraine has recently been recognized as a novel subtype of migraine. However, the mechanism that relate vestibular symptoms to migraine had not been well elucidated. Thus, the present study investigated vestibular dysfunction in a rat model of chronic migraine (CM), and to dissect potential mechanisms between migraine and vertigo.

Methods

Rats subjected to recurrent intermittent administration of nitroglycerin (NTG) were used as the CM model. Migraine- and vestibular-related behaviors were analyzed. Immunofluorescent analyses and quantitative real-time polymerase chain reaction were employed to detect expressions of c-fos and calcitonin gene-related peptide (CGRP) in the trigeminal nucleus caudalis (TNC) and vestibular nucleus (VN). Morphological changes of vestibular afferent terminals was determined under transmission electron microscopy. FluoroGold (FG) and CTB-555 were selected as retrograde tracers and injected into the VN and TNC, respectively. Lentiviral vectors comprising CGRP short hairpin RNA (LV-CGRP) was injected into the trigeminal ganglion.

Results

CM led to persistent thermal hyperalgesia, spontaneous facial pain, and prominent vestibular dysfunction, accompanied by the upregulation of c-fos labeling neurons and CGRP immunoreactivity in the TNC (c-fos: vehicle vs. CM = 2.9 ± 0.6 vs. 45.5 ± 3.4; CGRP OD: vehicle vs. CM = 0.1 ± 0.0 vs. 0.2 ± 0.0) and VN (c-fos: vehicle vs. CM = 2.3 ± 0.8 vs. 54.0 ± 2.1; CGRP mRNA: vehicle vs. CM = 1.0 ± 0.1 vs. 2.4 ± 0.1). Furthermore, FG-positive neurons was accumulated in the superficial layer of the TNC, and the number of c-fos+/FG+ neurons were significantly increased in rats with CM compared to the vehicle group (vehicle vs. CM = 25.3 ± 2.2 vs. 83.9 ± 3.0). Meanwhile, CTB-555+ neurons dispersed throughout the VN. The structure of vestibular afferent terminals was less pronounced after CM compared with the peripheral vestibular dysfunction model. In vivo knockdown of CGRP in the trigeminal ganglion significantly reduced the number of c-fos labeling neurons (LV-CGRP vs. LV-NC = 9.9 ± 3.0 vs. 60.0 ± 4.5) and CGRP mRNA (LV-CGRP vs. LV-NC = 1.0 ± 0.1 vs. 2.1 ± 0.2) in the VN, further attenuating vestibular dysfunction after CM.

Conclusions

These data demonstrates the possibility of sensitization of vestibular nucleus neurons to impair vestibular function after CM, and anti-CGRP treatment to restore vestibular dysfunction in patients with CM.

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

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

Calcitonin Gene-Related Peptide Receptor Antagonists (Gepants) for the Acute Treatment of Nausea in Episodic Migraine: A Systematic Review and Meta-Analysis

OBJECTIVE

To synthesize the evidence on the efficacy of calcitonin gene-related peptide receptor antagonists (gepants) from all clinical trials addressing nausea treatment for episodic migraine.

INTRODUCTION

Nausea is one of the most bothersome symptoms in patients with migraine. The most bothersome symptom is part of the outcomes explored in clinical trials.

METHODS

Published clinical trials for this project were identified via searches of 4 bibliographic databases: PubMed (includes MEDLINE), Embase, Web of Science, and the Cochrane Library. Individual search strategies included terms related to calcitonin gene-related peptide, nausea, and vomiting. Random-effects meta-analysis was conducted to estimate the overall efficacy of gepants for nausea treatment. Heterogeneity, publication bias, small-study bias, and potential confounders were explored using Galbraith plot, sensitivity analysis, meta-regression, and Egger's regression tests. Cumulative meta-analysis was done to detect temporal trend from accumulating trials.

RESULTS

The meta-analysis involved 23,008 participants in 65 clinical trials from 14 published articles; 10,770 subjects participated in gepant treatment arms while 12,238 subjects participated in placebo or non-gepant arms (85% females, mean age 41 years in both arms). Nearly all studies used a 2-hour incidence of nausea as an outcome measure. An overall combined effect size with an odds ratio of 1.29 (95% CI 1.18, 1.40, P = .001; I²  = 42.8%) showed the efficacy of gepants for the treatment of nausea in episodic migraine. Galbraith plot demonstrated that 98.4% of studies were within 2 standard deviations from the regression line, indicating lack of significant heterogeneity and outliers. Meta-analysis results were robust to sensitivity analysis, small-study bias, and publication bias (Kendall's Tau -0.09, P = .29; Egger's regression P = .67). Meta-regression showed that both age and sex ratio were not confounding the meta-analysis (omnibus P = .69). Cumulative meta-analysis indicated that the effect size remained stable for studies conducted after 2011, with accumulating evidence continuing to favor efficacy of gepants for the treatment of nausea in episodic migraine.

CONCLUSION

There is sufficient evidence to support the efficacy of gepants for the treatment of nausea in episodic migraine. Future research may focus on examining this efficacy in under-represented patient populations (males, older age groups) and in chronic migraine.

Loss of α-Calcitonin Gene-Related Peptide (αCGRP) Reduces Otolith Activation Timing Dynamics and Impairs Balance

Calcitonin gene-related peptide (CGRP) is a neuroactive peptide that is thought to play a role at efferent synapses in hair cell organs including the cochlea, lateral line, and semicircular canal. The deletion of CGRP in transgenic mice is associated with a significant reduction in suprathreshold cochlear nerve activity and vestibulo–ocular reflex (VOR) gain efficacy when compared to littermate controls. Here we asked whether the loss of CGRP also influences otolithic end organ function and contributes to balance impairments. Immunostaining for CGRP was absent in the otolithic end organs of αCGRP null (-/-) mice while choline acetyltransferase (ChAT) immunolabeling appeared unchanged suggesting the overall gross development of efferent innervation in otolithic organs was unaltered. Otolithic function was assessed by quantifying the thresholds, suprathreshold amplitudes, and latencies of vestibular sensory-evoked potentials (VsEPs) while general balance function was assessed using a modified rotarod assay. The loss of αCGRP in null (-/-) mice was associated with: (1) shorter VsEP latencies without a concomitant change in amplitude or thresholds, and (2) deficits in the rotarod balance assay. Our findings show that CGRP loss results in faster otolith afferent activation timing, suggesting that the CGRP component of the efferent vestibular system (EVS) also plays a role in otolithic organ dynamics, which when coupled with reduced VOR gain efficacy, impairs balance.

Targeted 5-HT1F Therapies for Migraine

Migraine is a common neurological disease characterised by the presence of attacks of unilateral, severe head pain accompanied by other symptoms. Although it has been classified as the sixth most disabling disorder, the available therapeutic options to treat this condition have not progressed accordingly. The advance in the development of 5-HT1 receptor agonists for migraine, including 5-HT1B/D and 5-HT1F receptor agonists, has meant a major step forward towards the progression of a better treatment for migraine. Triptans have a limited efficacy, and their effect on vasoconstriction makes them unsafe for patients with cardiovascular and/or cerebrovascular diseases. Therefore, novel effective antimigraine treatments without cardiovascular effects are required, such as selective 5-HT1F receptor agonists (ditans). Lasmiditan has much higher affinity for the 5-HT1F receptor than for the vasoconstrictor 5-HT1B receptor. This has been confirmed in preclinical studies performed to date, where lasmiditan showed no effect on vasoconstriction, and in clinical trials, where healthy individuals and patients did not report cardiac events due to treatment with lasmiditan, although it should be confirmed in larger cohorts. Lasmiditan crosses the blood-brain barrier and may act both centrally and peripherally on 5-HT1F receptors expressed on trigeminal neurons. It is a well-tolerated compound that does not induce major adverse events. Although ongoing phase III clinical trials are needed to confirm its efficacy and safety, lasmiditan might offer an alternative to treat acute migraine with no associated cardiovascular risk. This review will focus on the characterisation of 5-HT1 receptor agonists and their effects as migraine therapies.

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

Background

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

Discussion

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

Conclusion

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

Cilostazol induced migraine does not respond to sumatriptan in a double blind trial

BACKGROUND

Cilostazol is an inhibitor of phosphodiesterase 3 and thus causes accumulation of cAMP. It induces migraine-like attacks in migraine patients. Whether the cilostazol model responds to sumatriptan in migraine patients and therefore is valid for testing of future anti-migraine medications has never been investigated.

METHODS

In a cross-over study, 30 patients received cilostazol (200 mg p.o.) on two separate days each day followed by oral self-administered placebo or sumatriptan 50 mg. We recorded headache characteristics and associated symptoms using a questionnaire. The 30 participants were asked to subsequently treat their spontaneous attacks with sumatriptan (50 mg) or placebo in a double-blind cross-over design and 15 participants did so.

RESULTS

Cilostazol induced headache with some migraine characteristics in all participants; 18 patients on the sumatriptan day and 19 patients on the placebo day fulfilled criteria for a migraine-like attack. The difference in median headache intensity between sumatriptan and placebo at 2 h was not significant (p = 0.09), but it was at 4 h (p = 0.017). During spontaneous attacks, the difference between placebo and sumatriptan was not significant at 2 h (p = 0.26), but it was highly significant at 4 h (p = 0.006).

CONCLUSION

The cilostazol model in migraine patients could not be validated by a sufficient sumatriptan response. The model may perhaps respond to new drugs that act intracellularly or directly on ion channels.

TRIAL REGISTRATION

The study is registered on clinicaltrials.gov ( NCT02486276 ).

Meniere's Disease and Vestibular Migraine: Updates and Review of the Literature

The diagnosis of Meniere's disease (MD) and vestibular migraine (VM) is primarily based on clinical criteria and their differentiation is often difficult. Currently, there are no known definitive diagnostic tests that can reliably distinguish the two conditions. Patients with MD and patients with VM are treated differently, therefore improving the diagnosis of these two pathologies should avoid errors in management. A systematic review was conducted according to PRISMA guidelines. Medline-Ovid and Embase databases were used to conduct a thorough search of English-language publications dating from 1948 to March 2016. The primary search objective was to identify all papers explicitly comparing MD and VM in order to clarify and validate the diagnosis of these two diseases. A total of 13 articles out of 831 were reviewed. Among other differences, MD showed later age of onset, more hearing loss, tinnitus, aural fullness, abnormal nystagmus, abnormal caloric testing results, abnormal vestibular evoked myogenic potential and endolymphatic hydrops. VM showed more headaches, photophobia, vomiting and aura. Even though differences were noted between the two diseases, only one study focused on assessing the differences between VM, MD and patients fulfilling both diagnostic criteria (MDVM). This study showed no difference between the three groups. Since the introduction of the new International Headache Society and Barany Society criteria for VM, no studies have focused on comparing these three groups. We strongly encourage authors to focus on comparing MD and VM from MDVM in future studies to help adequately distinguish the diagnosis of both diseases.

New insights into pathophysiology of vestibular migraine

Vestibular migraine (VM) is a common disorder in which genetic, epigenetic, and environmental factors probably contribute to its development. The pathophysiology of VM is unknown; nevertheless in the last few years, several studies are contributing to understand the neurophysiological pathways involved in VM. The current hypotheses are mostly based on the knowledge of migraine itself. The evidence of trigeminal innervation of the labyrinth vessels and the localization of vasoactive neuropeptides in the perivascular afferent terminals of these trigeminal fibers support the involvement of the trigemino-vascular system. The neurogenic inflammation triggered by activation of the trigeminal-vestibulocochlear reflex, with the subsequent inner ear plasma protein extravasation and the release of inflammatory mediators, can contribute to a sustained activation and sensitization of the trigeminal primary afferent neurons explaining VM symptoms. The reciprocal connections between brainstem vestibular nuclei and the structures that modulate trigeminal nociceptive inputs (rostral ventromedial medulla, ventrolateral periaqueductal gray, locus coeruleus, and nucleus raphe magnus) are critical to understand the pathophysiology of VM. Although cortical spreading depression can affect cortical areas involved in processing vestibular information, functional neuroimaging techniques suggest a dysmodulation in the multimodal sensory integration and processing of vestibular and nociceptive information, resulting from a vestibulo-thalamo-cortical dysfunction, as the pathogenic mechanism underlying VM. The elevated prevalence of VM suggests that multiple functional variants may confer a genetic susceptibility leading to a dysregulation of excitatory–inhibitory balance in brain structures involved in the processing of sensory information, vestibular inputs, and pain. The interactions among several functional and structural neural networks could explain the pathogenic mechanisms of VM.

Central Integration of Canal and Otolith Signals is Abnormal in Vestibular Migraine

Vestibular migraine (VM), a common cause of vestibular symptoms within the general population, is a disabling and poorly understood form of dizziness. We sought to examine the underlying pathophysiology of VM with three studies, which involved the central synthesis of canal and otolith cues, and present preliminary results from each of these studies: (1) VM patients appear to have reduced motion perception thresholds when canal and otolith signals are modulated in a co-planar manner during roll tilt; (2) percepts of roll tilt appear to develop more slowly in VM patients than in control groups during a centrifugation paradigm that presents conflicting, orthogonal canal and otolith cues; and (3) eye movement responses appear to be different in VM patients when studied with a post-rotational tilt paradigm, which also presents a canal–otolith conflict, as the shift of the eye’s rotational axis was larger in VM and the relationship between the axis shift and tilt suppression of the vestibulo-ocular reflex differed in VM patients relative to control groups. Based on these preliminary perceptual and eye movement results obtained with three different motion paradigms, we present a hypothesis that the integration of canal and otolith signals by the brain is abnormal in VM and that this abnormality could be cerebellar in origin. We provide potential mechanisms that could underlie these observations, and speculate that one of more of these mechanisms contributes to the vestibular symptoms and motion intolerance that are characteristic of the VM syndrome.

Loss of α-calcitonin gene-related peptide (αCGRP) reduces the efficacy of the Vestibulo-ocular Reflex (VOR)

The neuroactive peptide calcitonin-gene related peptide (CGRP) is known to act at efferent synapses and their targets in hair cell organs, including the cochlea and lateral line. CGRP is also expressed in vestibular efferent neurons as well as a number of central vestibular neurons. Although CGRP-null (-/-) mice demonstrate a significant reduction in cochlear nerve sound-evoked activity compared with wild-type mice, it is unknown whether and how the loss of CGRP influence vestibular system function. Vestibular function was assessed by quantifying the vestibulo-ocular reflex (VOR) in alert mice. The loss of CGRP in (-/-) mice was associated with a reduction of the VOR gain of ≈50% without a concomitant change in phase. Using immunohistochemistry, we confirmed that, although CGRP staining was absent in the vestibular end-organs of null (-/-) mice, cholinergic staining appeared normal, suggesting that the overall gross development of vestibular efferent innervation was unaltered. We further confirmed that the observed deficit in vestibular function of null (-/-) mice was not the result of nontargeted effects at the level of the extraocular motor neurons and/or their innervation of extraocular muscles. Analysis of the relationship between vestibular quick phase amplitude and peak velocity revealed that extraocular motor function was unchanged, and immunohistochemistry revealed no abnormalities in motor endplates. Together, our findings show that the neurotransmitter CGRP plays a key role in ensuring VOR efficacy.

Immunohistochemical and biomolecular identification of melatonin 1a and 1b receptors in rat vestibular nuclei

OBJECTIVE

The aim of this study was to examine the localizations and expressions of melatonin 1a (MT1a) and 1b (MT1b) receptors in rat vestibular nuclei by immunohistochemical staining and reverse transcriptase-polymerase chain reaction.

MATERIALS AND METHODS

Twenty male Sprague-Dawley rats were used in this study. Antibodies for the MT1a and MT1b receptors were used in 10 rats, respectively. A further 10 animals were sacrificed for RT-PCR. Tissues containing medial vestibular nuclei were selectively isolated from brain stem slices for RT-PCR.

RESULTS

MT1a and MT1b receptor immunopositive neurons were found to be distributed throughout the four major vestibular nuclei. Both receptors were primarily detected in neuronal somata and their proximal dendrites. The presences of the mRNAs of the MT1a and MT1b receptors were confirmed by RT-PCR in medial vestibular nuclei and trigeminal ganglia.

CONCLUSIONS

The present study demonstrates, for the first time, that MT1a and MT1b receptors are localized and expressed in rat vestibular nuclei. This study provides additional insight into the role of melatonin receptors during vestibular signal processing.

The point prevalence of dizziness or vertigo in migraine--and factors that influence presentation

OBJECTIVE

To ascertain and characterize the point prevalence of dizziness or vertigo in migraineurs presenting for routine appointments at a specialty headache clinic.

BACKGROUND

Migraine, dizziness, and vertigo are all common in the general population, affecting 13%, 20-30%, and 5-10% respectively. Thereby, chance concurrence of migraine with either dizziness or vertigo would be expected in roughly 4% of the general population. It is the authors' clinical impression that severe attacks of migraine are far more commonly associated with these complaints than chance would predict.

METHODS

This is a prospective, cross-sectional study of 462 consecutive patients who presented for consultation at a specialty headache clinic over a 4-month period of time. During routine check-in procedures, patients were asked to report their headache pain on a 1-10 Likert scale. Patients were also asked to report if they were currently experiencing dizziness or vertigo. Responses to these questions were recorded along with vital signs. Diagnosis of migraine with or without aura was made by headache medicine specialists in accordance with International Classification of Headache Disorders--second edition criteria. Chi-square analysis was used to examine the prevalence of vertigo or dizziness in subjects with varying intensity of headache, and by history of aura.

RESULTS

Of the 425 evaluable subjects, 28% experienced aura. Subjects' average age was 43.8 years (range 15 to 76 years); 89.5% were female. At the time of evaluation, 72.4% of subjects reported some degree of ongoing headache pain and 15.7% reported concurrent dizziness or vertigo. The prevalence of dizziness or vertigo was twice as high (24.5% vs 12.1%) in migraine with aura compared to migraine without aura (P < .01), and prevalence increased with age (P < .05). There was a strong correlation between migraine pain and subjective complaint of vertigo (P < .001). When migraine pain was present at an intensity of 7 or greater (on a scale of 1-10), almost half of the subjects (47.5%) reported concomitant dizziness or vertigo.

CONCLUSIONS

Subjective complaints of dizziness or vertigo appear to be relatively common accompaniments of migraine, particularly migraine with aura, and prevalence increases with age. Disequilibrium symptoms have a strong and positive association with the severity of migraine pain. With co-occurrence higher than expected by chance, the relationship either reflects comorbidity or these symptoms may be part of the migraine presentation. With a point prevalence of 15.7%, and factors that link expression both to the intensity of migraine pain and to migraine aura, the authors believe that the true relationship may prove to be the latter.