Estrogen modulation of cortical spreading depression.

BACKGROUND AND AIMS: Cortical spreading depression (CSD), a transient neuronal and glial depolarization that propagates slowly across the cerebral cortex, is the putative electrophysiological event underlying migraine aura and a headache trigger. Migraine is three times more prevalent in women than men, linked to circulating female hormones. High estrogen levels or estrogen withdrawal may be a migraine trigger for many women. We, therefore, aimed to examine whether sex, gonadectomy, and female hormone supplementation and withdrawal affect the susceptibility to CSD. METHODS: To determine CSD susceptibility, we recorded the frequency of CSDs triggered during 2-h topical KCl application in intact or gonadectomized female and male rats, without or with estradiol or progesterone supplementation via daily intraperitoneal injections. Estrogen or progesterone treatment followed by withdrawal was studied in a separate cohort. To take the first step towards identifying potential mechanisms, we studied glutamate and GABAA receptor binding using autoradiography. RESULTS: The CSD frequency in intact female rats was higher than intact male and ovariectomized rats. We did not detect a change in CSD frequency during different stages of the estrous cycle in intact females. Daily estrogen injections for three weeks did not change CSD frequency. However, one-week estrogen withdrawal after two weeks of treatment significantly increased CSD frequency compared with the vehicle group in gonadectomized females. The same protocol of estrogen treatment and withdrawal was ineffective in gonadectomized males. In contrast to estrogen, daily progesterone injections for three weeks elevated CSD susceptibility, and one-week withdrawal after two weeks of treatment partially normalized this effect. Autoradiography did not reveal significant changes in glutamate or GABAA receptor binding density after estrogen treatment and withdrawal. CONCLUSIONS: These data suggest that females are more susceptible to CSD, and sexual dimorphism is abrogated by gonadectomy. Moreover, estrogen withdrawal after prolonged daily treatment enhances CSD susceptibility. These findings may have implications for estrogen-withdrawal migraine, although the latter tends to be without aura.

The effect of sex and estrus cycle stage on optogenetic spreading depression induced migraine-like pain phenotypes.

BACKGROUND: Migraine is more prevalent in females, raising the possibility that sex and gonadal hormones modulate migraine. We recently demonstrated that minimally invasive optogenetic spreading depolarization (opto-SD) elicits robust periorbital allodynia. The objective of this study was to test the hypothesis that opto-SD induced migraine-like pain behavior is worse in females and varies during the estrus cycle. METHODS: Single or repeated opto-SDs were induced in male and female adult Thy1-ChR2-YFP transgenic mice. Von Frey monofilaments were used to test periorbital mechanical allodynia. Mouse grimace was also examined under increasing light intensity to quantify spontaneous discomfort and light-aversive behavior. Vaginal smears were obtained for estrus cycle staging at the end of behavioral testing. RESULTS: A multi-variable regression analysis was performed using a male and female cohort to test the effect of independent variables on periorbital allodynia. Opto-SD predicted lower periorbital thresholds as compared with sham stimulation (p < 0.0001). Additionally, female sex predicted lower periorbital thresholds compared with males (p = 0.011). There were significant interactions between opto-SD and time (interaction p = 0.030) as animals tended to recover from opto-SD allodynia over time, and between sex and time (p = 0.020) as females tended to take longer to recover. Proestrus, estrus (PE) and metestrus, diestrus (MD) stages were combined to represent high versus low circulating estradiol relative to progesterone, respectively. Multi-variable regression revealed an effect of estrus cycle (p = 0.015) on periorbital thresholds. In the sham group, PE had lower thresholds than MD. However, there was no interaction between opto-SD and the estrus cycle (p = 0.364). Grimace scores were also examined at incremental light intensities. There was an effect of opto-SD (p < 0.0001), light intensity (p = 0.001) and estrus cycle (p = 0.024) on grimace without interaction among them (three-way ANOVA). CONCLUSIONS: Female sex and estrus stages with high circulating estradiol relative to progesterone lower trigeminal pain thresholds and augment photosensitivity. In females, opto-SD increased pain behavior and photosensitivity irrespective of the estrus stage.

Optogenetic Spreading Depression Elicits Trigeminal Pain and Anxiety Behavior.

OBJECTIVE: Cortical spreading depression (SD) is an intense depolarization underlying migraine aura. Despite the weight of evidence linking SD to the pain phase of migraine, controversy remains over a causal role of SD in cephalgia because of the invasive nature of previous SD induction methods. To overcome this problem, we used a novel minimally invasive optogenetic SD induction method and examined the effect of SD on behavior. METHODS: Optogenetic SD was induced as a single event or repeatedly every other day for 2 weeks. End points, including periorbital and hindpaw mechanical allodynia, mouse grimace, anxiety, and working memory, were examined in male and female mice. RESULTS: A single SD produced bilateral periorbital mechanical allodynia that developed within 1 hour and resolved within 2 days. Sumatriptan prevented periorbital allodynia when administered immediately after SD. Repeated SDs also produced bilateral periorbital allodynia that lasted 4 days and resolved within 2 weeks after the last SD. In contrast, the hindpaw withdrawal thresholds did not change after repeated SDs suggesting that SD-induced allodynia was limited to the trigeminal region. Moreover, repeated SDs increased mouse grimace scores 2 days after the last SD, whereas a single SD did not. Repeated SDs also increased thigmotaxis scores as a measure of anxiety. In contrast, neither single nor repeated SDs affected visuospatial working memory. We did not detect sexual dimorphism in any end point. INTERPRETATION: Altogether, these data show a clinically congruent causal relationship among SD, trigeminal pain, and anxiety behavior, possibly reflecting SD modulation of hypothalamic, thalamic, and limbic mechanisms. ANN NEUROL 2021;89:99-110.

Evaluation and treatment of headache associated with moyamoya disease - a narrative review.

BACKGROUND: Headache in patients with moyamoya disease is an under-addressed topic in the medical literature. Delay in the diagnosis of moyamoya disease or inappropriate treatment of headache could lead to devastating cerebrovascular outcome. With the evolving understanding of moyamoya disease, migraine pathophysiology, and various migraine-specific medications that have become available, it is crucial to provide an updated overview on this topic. METHODS: We searched PubMed for keywords including moyamoya disease, moyamoya syndrome, headache in moyamoya, surgical revascularization, surgical bypass, migraine and moyamoya, and calcitonin gene-related peptide (CGRP). We summarized the literature and provide a comprehensive review of the headache presentation, possible mechanisms, the impact of various surgical revascularizations on headache in patients with moyamoya disease, and the medical management of headache incorporating novel migraine-specific treatments.Results and conclusion: The most common headache phenotype is migraine; tension-type headache, hemiplegic migraine, and cluster headache have also been reported. Most patients experience improvement of headache after surgical revascularization, though some patients report worsening, or new-onset headache after surgery. Given the complexity of moyamoya disease, careful consideration of different types of medical therapy for headache is necessary to improve the quality of life while not increasing the risk of adverse cerebrovascular events. More prospective studies are warranted to better understand and manage headache in patients with moyamoya disease.

Anatomy and Physiology of Headache.

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

Long COVID headache.

Headache is among the most frequent symptoms persisting or newly developing after coronavirus disease 2019 (COVID-19) as part of the so-called long COVID syndrome. The knowledge on long COVID headache is still limited, however growing evidence is defining the features of this novel condition, in particular regarding clinical characteristics, some pathophysiological mechanisms and first treatment recommendations. Long COVID headache can present in the form of worsening of a preexisting primary headache, or, more specifically, in the form of a new (intermittent or daily) headache starting during the acute infection or after a delay. It often presents together with other long COVID symptoms, most frequently with hyposmia. It can manifest with a migrainous or, more frequently, with a tension-type-like phenotype. Persistent activation of the immune system and trigeminovascular activation are thought to play a role. As there are virtually no treatment studies, treatment currently is largely guided by the existing guidelines for primary headaches with the corresponding phenotype. The present report, a collaborative work of the international group of the Junior Editorial Board of The Journal of Headache and Pain aims to summarize the most recent evidence about long COVID headache and suggests approaches to the diagnosis and treatment of this disorder.

Spreading depression as a preclinical model of migraine.

Spreading depression (SD) is a slowly propagating wave of near-complete depolarization of neurons and glial cells across the cortex. SD is thought to contribute to the underlying pathophysiology of migraine aura, and possibly also an intrinsic brain activity causing migraine headache. Experimental models of SD have recapitulated multiple migraine-related phenomena and are considered highly translational. In this review, we summarize conventional and novel methods to trigger SD, with specific focus on optogenetic methods. We outline physiological triggers that might affect SD susceptibility, review a multitude of physiological, biochemical, and behavioral consequences of SD, and elaborate their relevance to migraine pathophysiology. The possibility of constructing a recurrent episodic or chronic migraine model using SD is also discussed.

Animal models of migraine and experimental techniques used to examine trigeminal sensory processing.

BACKGROUND: Migraine is a common debilitating condition whose main attributes are severe recurrent headaches with accompanying sensitivity to light and sound, nausea and vomiting. Migraine-related pain is a major cause of its accompanying disability and can encumber almost every aspect of daily life. MAIN BODY: Advancements in our understanding of the neurobiology of migraine headache have come in large from basic science research utilizing small animal models of migraine-related pain. In this current review, we aim to describe several commonly utilized preclinical models of migraine. We will discuss the diverse array of methodologies for triggering and measuring migraine-related pain phenotypes and highlight briefly specific advantages and limitations therein. Finally, we will address potential future challenges/opportunities to refine existing and develop novel preclinical models of migraine that move beyond migraine-related pain and expand into alternate migraine-related phenotypes. CONCLUSION: Several well validated animal models of pain relevant for headache exist, the researcher should consider the advantages and limitations of each model before selecting the most appropriate to answer the specific research question. Further, we should continually strive to refine existing and generate new animal and non-animal models that have the ability to advance our understanding of head pain as well as non-pain symptoms of primary headache disorders.

Granulomatous Angiitis of the Central Nervous System Associated with Hodgkin's Lymphoma: Case Report and Literature Review.

Granulomatous angiitis of the central nervous system (GACNS) is a rare cerebrovascular disorder. It usually presents with multifocal neurologic symptoms symptoms including stroke, encephalopathy, and headache. A limited number of case reports describe neurological deficits resulting from GACNS as the manifesting symptoms of Hodgkin's lymphoma (HL). We describe the case of a patient with neurological symptoms from GACNS that led to the diagnosis of HL, as well as a literature review focusing on the association between GACNS and HL.

Headache and Its Approach in Today's NeuroIntensive Care Unit.

Headache is a very common symptom in the neurointensive care unit (neuroICU). While headache in the neuroICU can be caused by worsening of a pre-existing primary headache disorder, most are secondary to another condition. Additionally, headache can be the presenting symptom of a number of conditions requiring prompt recognition and treatment including subarachnoid hemorrhage, ischemic and hemorrhagic stroke, central nervous system infection, pituitary apoplexy, and cerebral vasoconstriction. The neuroICU also has a unique postoperative population in which postcraniectomy and postcraniotomy headache, postintravascular intervention headache, hyperperfusion syndrome, ventriculitis, medication overuse or withdrawal headache, and hypercapnia may be encountered. Management varies dramatically depending on the etiology of the headache. Overreliance on opiate analgesics may produce significant adverse effects and lengthen ICU stays. However, nonnarcotic medications are increasingly being recognized as helpful in reducing the pain among various postsurgical and headache patients. Taken together, a multimodal approach targeting the underlying pathology and choosing appropriate systemic and local analgesic medications may be the best way to manage headache in critically ill patients.

Dissecting the association between migraine and stroke.

Migraine is a common disabling neurological disorder resulting from excessive cortical excitation and trigeminovascular afferent sensitization. In addition to aberrant neuronal processing, migraineurs are also at significant risk of vascular disease. Consequently, the impact of migraine extends well beyond the ictal headache and includes a well-documented association with acute ischemic stroke, particularly in young women with a history of migraine with aura. The association between migraine and stroke has been acknowledged for 40 years or more. However, examining the pathobiology of this association has become a more recent and critically important undertaking. The diversity of mechanisms underlying the association between migraine and stroke likely reflects the heterogenous nature of this disorder. Vasospasm, endothelial injury, platelet aggregation and prothrombotic states, cortical spreading depression, carotid dissection, genetic variants, and traditional vascular risk factors have been offered as putative mechanisms involved in migraine-related stroke risk. Assimilating these seemingly divergent pathomechanisms into a cogent understanding of migraine-related stroke will inform future studies and the development of new strategies for the prevention and treatment of migraine and stroke.

Migraine is associated with altered processing of sensory stimuli.

Migraine is associated with derangements in perception of multiple sensory modalities including vision, hearing, smell, and somatosensation. Compared to people without migraine, migraineurs have lower discomfort thresholds in response to special sensory stimuli as well as to mechanical and thermal noxious stimuli. Likewise, the environmental triggers of migraine attacks, such as odors and flashing lights, highlight basal abnormalities in sensory processing and integration. These alterations in sensory processing and perception in migraineurs have been investigated via physiological studies and functional brain imaging studies. Investigations have demonstrated that migraineurs during and between migraine attacks have atypical stimulus-induced activations of brainstem, subcortical, and cortical regions that participate in sensory processing. A lack of normal habituation to repetitive stimuli during the interictal state and a tendency towards development of sensitization likely contribute to migraine-related alterations in sensory processing.

Effect of Ubrogepant on Patient-Reported Outcomes When Administered During the Migraine Prodrome: Results From the Randomized PRODROME Trial.

BACKGROUND AND OBJECTIVES: Ubrogepant is a calcitonin gene-related peptide receptor antagonist approved for the acute treatment of migraine. The PRODROME trial previously demonstrated that ubrogepant treatment during prodrome prevents the onset of moderate or severe headache. In this analysis of the PRODROME trial, the benefits of ubrogepant treatment during the prodrome on patient-reported outcomes (PROs) are evaluated. METHODS: PRODROME was a multicenter, randomized, double-blind, placebo-controlled, crossover trial that enrolled adults who experienced 2-8 migraine attacks per month with moderate-severe headache pain. Eligible participants treated 2 qualifying prodrome events, defined as a migraine attack with prodromal symptoms when the participant was confident a headache would follow within 1-6 hours. Participants were randomized to treatment sequence A (placebo then ubrogepant 100 mg) or sequence B (ubrogepant 100 mg then placebo). This analysis evaluated the ability to function normally over 24 hours (secondary end point) and at specific time points after dose (additional end point). Other PRO end points included activity limitation over 24 hours and satisfaction with study medication at 8 and 24 hours. RESULTS: Of 518 randomized participants, 477 comprised the modified intent-to-treat population. After treatment of qualifying prodrome events, a significantly greater ability to function normally over 24 hours was observed for participants after treatment with ubrogepant 100 mg compared with placebo (odds ratio [OR] 1.66, 95% CI 1.40-1.96; p < 0.0001). As early as 2 hours after dose, a greater proportion of ubrogepant-treated participants reported "no disability, able to function normally" compared with placebo (OR 1.76, 95% CI 1.32-2.35; nominal p = 0.0001). Ubrogepant administered during the prodrome was also associated with a greater reduction in activity limitations over 24 hours after dose (OR 2.07, 95% CI 1.61-2.67; nominal p < 0.0001). At 8 and 24 hours after dose, rates of being "satisfied" or "extremely satisfied" were greater for ubrogepant than for placebo (8 hours: OR 2.37, 95% CI 1.78-3.15; nominal p < 0.0001; 24 hours: OR 2.32, 95% CI 1.78-3.02; nominal p < 0.0001). DISCUSSION: Ubrogepant 100 mg administered during the prodrome was associated with significantly greater ability to function normally, greater reduction in activity limitations over 24 hours, and greater satisfaction with study medication, compared with placebo. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov NCT04492020. Submitted: July 27, 2020; first patient enrolled: August 21, 2020. clinicaltrials.gov/ct2/show/NCT04492020. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that taking ubrogepant 100 mg during a migraine prodrome allows more patients to function normally over the next 24 hours.

Inhibition of persistent sodium current reduces spreading depression-evoked allodynia in a mouse model of migraine with aura.

ABSTRACT: We investigated the efficacy of inhibiting persistent Na + currents (I NaP ) in acute rodent models of migraine with aura. Cortical spreading depression (SD) is a slow wave of neuronal and glial depolarization that underlies the migraine aura. Minimally invasive optogenetic SD (opto-SD) causes periorbital mechanical allodynia in mice, suggesting SD activates trigeminal nociceptors. Persistent Na + currents contribute to neuronal intrinsic excitability and have been implicated in peripheral and cortical excitation. We examined a preferential inhibitor of I NaP, GS-458967, on SD-induced periorbital allodynia, SD susceptibility, and formalin-induced peripheral pain. Periorbital mechanical allodynia was tested in male and female Thy1-ChR2-YFP mice after a single opto-SD event using manual von Frey monofilaments. GS-458967 (1 mg/kg, s.c.) or vehicle was dosed immediately after opto-SD induction, and allodynia was tested 1 hour later. The electrical SD threshold and KCl-induced SD frequency were examined in the cortex in male Sprague-Dawley rats after 1 hour pretreatment with GS-458967 (3 mg/kg, s.c.) or vehicle. Effects of GS-458967 (0.5-5 mg/kg, p.o.) on spontaneous formalin hind paw behavior and locomotion were also examined in male CD-1 mice. GS-458967 suppressed opto-SD-induced periorbital allodynia and decreased susceptibility to SD. GS-458967 also diminished early and late phase formalin-induced paw-licking behavior with early phase paw licking responding to lower doses. GS-458967 up to 3 mg/kg had no impact on locomotor activity. These data provide evidence that I NaP inhibition can reduce opto-SD-induced trigeminal pain behavior and support I NaP inhibition as an antinociceptive strategy for both abortive and preventive treatment of migraine.

Prepregnancy Migraine, Migraine Phenotype, and Risk of Adverse Pregnancy Outcomes.

BACKGROUND AND OBJECTIVE: Migraine is a highly prevalent neurovascular disorder among reproductive-aged women. Whether migraine history and migraine phenotype might serve as clinically useful markers of obstetric risk is not clear. The primary objective of this study was to examine associations of prepregnancy migraine and migraine phenotype with risks of adverse pregnancy outcomes. METHODS: We estimated associations of self-reported physician-diagnosed migraine and migraine phenotype with adverse pregnancy outcomes in the prospective Nurses' Health Study II (1989-2009). Log-binomial and log-Poisson models with generalized estimating equations were used to estimate relative risks (RRs) and 95% CIs for gestational diabetes mellitus (GDM), preeclampsia, gestational hypertension, preterm delivery, and low birthweight. RESULTS: The analysis included 30,555 incident pregnancies after cohort enrollment among 19,694 participants without a history of cardiovascular disease, diabetes, or cancer. After adjusting for age, adiposity, and other health and behavioral factors, prepregnancy migraine (11%) was associated with higher risks of preterm delivery (RR = 1.17; 95% CI = 1.05-1.30), gestational hypertension (RR = 1.28; 95% CI = 1.11-1.48), and preeclampsia (RR = 1.40; 95% CI = 1.19-1.65) compared with no migraine. Migraine was not associated with low birthweight (RR = 0.99; 95% CI = 0.85-1.16) or GDM (RR = 1.05; 95% CI = 0.91-1.22). Risk of preeclampsia was somewhat higher among participants with migraine with aura (RR vs no migraine = 1.51; 95% CI = 1.22-1.88) than migraine without aura (RR vs no migraine = 1.30; 95% CI = 1.04-1.61; p-heterogeneity = 0.32), whereas other outcomes were similar by migraine phenotype. Participants with migraine who reported regular prepregnancy aspirin use had lower risks of preterm delivery (<2×/week RR = 1.24; 95% CI = 1.11-1.38; ≥2×/week RR = 0.55; 95% CI = 0.35-0.86; p-interaction < 0.01) and preeclampsia (<2×/week RR = 1.48; 95% CI = 1.25-1.75; ≥2×/week RR = 1.10; 95% CI = 0.62-1.96; p-interaction = 0.39); however, power for these stratified analyses was limited. DISCUSSION: Migraine history, and to a lesser extent migraine phenotype, appear to be important considerations in obstetric risk assessment and management. Future research should determine whether aspirin prophylaxis may be beneficial for preventing adverse pregnancy outcomes among pregnant individuals with a history of migraine.

Microembolism and Other Links Between Migraine and Stroke: Clinical and Pathophysiologic Update.

Migraine and stroke are highly prevalent diseases with a high effect on quality of life, with multiple epidemiologic, pathophysiologic, clinical, and prognostic areas of overlap. Migraine is a risk factor for stroke. This risk is explained by common risk factors, migraine-specific mechanisms, and non-migraine-specific mechanisms that have a relevant role in patients with migraine with aura (e.g., atrial fibrillation and paradoxical embolism through a patent foramen ovale). Another important link between migraine aura and ischemic stroke is cardiac embolism. Cardioembolism is the most frequent cause of ischemic stroke, and increasing evidence suggests that microembolism, predominantly but not exclusively originating in the heart, is a contributing mechanism to the development of migraine aura. In this review, we discuss epidemiologic aspects of the association between migraine and ischemic stroke, the clinical presentation of ischemic strokes in patients with migraine, and the differentiation between migrainous and nonmigrainous infarctions. After that, we review migraine-specific and non-migraine-specific stroke mechanisms. We then review updated preclinical and clinical data on microembolism as a cause of migraine aura. In the last section, we summarize knowledge gaps and important areas to explore in future research. The review includes a clinical vignette with a discussion of the most relevant topics addressed.

Temporal analysis of remote electric neuromodulation for the prevention of migraine.

Aim: To evaluate the onset, magnitude and persistence of efficacy of remote electrical neuromodulation (REN) compared with placebo for the preventive treatment of migraine. Materials & methods: Analysis was conducted on data from a prospective, double-blind, placebo-controlled clinical trial, which assessed the efficacy of REN for the prevention of migraine. The number of monthly migraine days (MMD) per group was calculated in 2-week intervals and compared between the groups. Results: Differences between the active (N = 95) and placebo (N = 84) groups reached significance at 2 weeks: therapeutic gain 0.84 MMD; p = 0.036. 4 weeks gain 1.59 MMD; p = 0.025, 6 weeks gain 2.27 MMD; p < 0.001, 8 weeks gain 2.68 MMD; p < 0.001. Conclusion: REN provides rapid and consistent efficacy in preventive treatment of migraine.

Safety and Feasibility of an Emergency Department-to-Outpatient Pathway for Patients With TIA and Nondisabling Stroke.

Background and Objectives: Evaluation of transient ischemic attack/nondisabling ischemic strokes (TIA/NDS) in the emergency department (ED) contributes to capacity issues and increasing health care expenditures, especially high-cost duplicative imaging. Methods: As an institutional quality improvement project, we developed a novel pathway to evaluate patients with TIA/NDS in the ED using a core set of laboratory tests and CT-based neuroimaging. Patients identified as 'low risk' through a safety checklist were discharged and scheduled for prompt outpatient tests and stroke clinic follow-up. In this prespecified analysis designed to assess feasibility and safety, we abstracted data from patients consecutively enrolled in the first 6 months. Results: We compared data from 106 patients with TIA/NDS enrolled in the new pathway from April through September 2020 (age 67.9 years, 45% female), against 55 unmatched historical controls with TIA encountered from April 2016 through March 2017 (age 68.3 years, 47% female). Both groups had similar median NIHSS scores (pathway and control 0) and ABCD2 scores (pathway and control 3). Pathway-enrolled patients had a 44% decrease in mean ED length of stay (pathway 13.7 hours, control 24.4 hours, p < 0.001) and decreased utilization of ED MRI-based imaging (pathway 63%, control 91%, p < 0.001) and duplicative ED CT plus MRI-based brain and/or vascular imaging (pathway 35%, control 53%, p = 0.04). Among pathway-enrolled patients, 89% were evaluated in our stroke clinic within a median of 5 business days; only 5.5% were lost to follow-up. Both groups had similar 90-day rates of ED revisits (pathway 21%, control 18%, p = 0.84) and recurrent TIA/ischemic stroke (pathway 1%, control 2%, p = 1.0). Recurrent ischemic events among pathway-enrolled patients were attributed to errors in following the safety checklist before discharge. Discussion: Our TIA/NDS pathway, implemented during the initial outbreak of COVID-19, seems feasible and safe, with significant positive impact on ED throughput and ED-based high-cost duplicative imaging. The safety checklist and option of virtual telehealth follow-up are novel features. Broader adoption of such pathways has important implications for value-based health care.

The complex actions of sumatriptan on rat dural afferents.

AIM: To test the hypothesis that the clinical efficacy of triptans reflects convergent modulation of ion channels also involved in inflammatory mediator (IM)-induced sensitization of dural afferents. METHODS: Acutely dissociated retrogradely labeled rat dural afferents were studied with whole cell and perforated patch techniques in the absence and presence of sumatriptan and/or IM (prostaglandin E2, bradykinin, and histamine). RESULTS: Sumatriptan dose-dependently suppressed voltage-gated Ca²âº currents. Acute (2 min) sumatriptan application increased dural afferent excitability and occluded further IM-induced sensitization. In contrast, pre-incubation (30 min) with sumatriptan had no influence on dural afferent excitability and partially prevented IM-induced sensitization of dural afferents. The sumatriptan-induced suppression of voltage-gated Ca²âº currents and acute sensitization and pre-incubation-induced block of IM-induced sensitization were blocked by the 5-HT(1D) antagonist BRL 15572. Pre-incubation with sumatriptan failed to suppress the IM-induced decrease in action potential threshold and overshoot (which results from modulation of voltage-gated Na⁺ currents) and activation of Cl⁻ current, and had no influence on the Cl⁻ reversal potential. However, pre-incubation with sumatriptan caused a dramatic hyperpolarizing shift in the voltage dependence of K⁺ current activation. DISCUSSION: These results indicate that although the actions of sumatriptan on dural afferents are complex, at least two distinct mechanisms underlie the antinociceptive actions of this compound. One of these mechanisms, the shift in the voltage dependence of K⁺ channel activation, may suggest a novel strategy for future development of anti-migraine agents.