Triptan-induced latent sensitization: a possible basis for medication overuse headache

Triptan treatment is associated with a higher number of red wine-induced migraine episodes: An exploratory questionnaire-based survey

AIM

Diet, including foods and beverages, affects migraine. Conversely, the influence of migraine therapies on dietary habits is largely unknown. This study aimed at investigating the effects of triptan intake on foods and drinks consumed by adults with migraine with and/or without aura.

METHODS

An exploratory questionnaire-based survey took place online between November 2022 and June 2023. Participants were recruited through advertisements shared on social media accounts (e.g., Facebook and Instagram) and seasonal newsletters of three Danish patient associations. In addition, posters and flyers in headache and pain centers at Danish hospitals and private neurological, pain, and physiotherapeutic clinics were utilized.

RESULTS

A total of 314 adults with migraine with and/or without aura completed the survey. Among the respondents, 236 individuals (75.2%) regularly used triptans to treat their migraines. Compared with non-triptan users, individuals using triptans were characterized by significantly more foods and/or drinks triggering migraine (74.2% vs. 56.4%, p = 0.005). Alcoholic beverages and most specifically red wine were overreported as migraine triggers by triptan users (48.3% vs. 21.8%, p < 0.001). In the week preceding the survey, red wine was significantly less consumed by triptan users than non-triptan users (92.4% vs. 76.9%, p < 0.001).

CONCLUSIONS

Patients who regularly consume triptans report red wine most frequently as a migraine trigger. Triptan users are characterized by a lower consumption of red wine than non-triptan users, suggesting that a regular triptan intake may promote an increased sensitivity to red wine-induced migraine.

Headache Attributed to a Substance or Its Withdrawal

Identification of substances that may cause or trigger headache is important to start effective treatment early to prevent unnecessary suffering, deterioration in quality of life, and the development of chronic pain. Treatment in case of medication overuse and other chronic headache should be decisive and effective. Drug withdrawal and introduction of effective prophylactic medication for the underlying headache disorder should be the primary treatment strategy. Typical headache-inducing substances are nitric oxide, phosphodiesterase, cocaine, alcohol, histamine, carbon oxide, and calcitonin gene-related peptide. The withdrawal of caffeine, estrogen, and opioids is most often associated with the development of headache.

Unsatisfactory response to acute medications does not affect the medication overuse headache development in pediatric chronic migraine

BACKGROUND

Chronic migraine (CM) negatively impacts the quality of life of 2 to 4% of pediatric patients. In adults, CM is frequently linked to medication overuse headache (MOH), but there is a much lower prevalence of MOH in children. A suboptimal response to acute therapies may lead to their reduced use, thus preventing MOH development in children and adolescents. The frequency of patients with CM who do not respond to acute therapies was examined in the present study. We investigated whether the prevalence of MOH was different between responders and non-responders. We also examined whether patients receiving prophylactic therapy had an improved response to acute therapy. Finally, we investigated if there was a difference in the frequency of psychiatric comorbidities between responders and non-responders.

METHODS

We retrospectively analysed clinical data of all chronic pediatric migraineurs under the age of 18 referred to the Headache Centre at Bambino Gesù Children Hospital in June 2021 and February 2023. ICHD3 criteria were used to diagnose CM and MOH. We collected demographic data, including the age at onset of migraine and the age of the CM course. At baseline and after 3 months of preventive treatment, we evaluated the response to acute medications. Neuropsychiatric comorbidities were referred by the children's parents during the first attendance evaluation.

RESULTS

Seventy patients with CM were assessed during the chosen period. Paracetamol was tried by 41 patients (58.5%), NSAIDs by 56 patients (80.0%), and triptans by 1 patient (1.4%). Fifty-one participants (73%) were non-responder to the abortive treatment. The presence of MOH was detected in 27.1% of the whole populations. Regarding our primary aim, MOH was diagnosed in 29% of non-responder patients and 22% of responders (p > 0.05). All patients received preventative treatment. After 3 months of preventive pharmacological therapy, 65.4% of patients who did not respond to acute medications achieved a response, while 34.6% of patients who were non-responder remain non-responder (p < 0.05). Prophylactic therapy was also effective in 69% of patients who responded to acute medication (p < 0.05). Psychiatric comorbidities were detected in 68.6% of patients, with no difference between responders and non-responders (72.2% vs. 67.3%; p = 0.05).

CONCLUSIONS

Despite the high prevalence of unresponsiveness to acute therapies in pediatric CM, it does not act as a protective factor for MOH. Moreover, responsiveness to acute drugs is improved by pharmacological preventive treatment and it is not affected by concomitant psychiatric comorbidities.

Medication "underuse" headache

BACKGROUND

Many risk factors have been associated with migraine progression, including insufficient and ineffective utilization of migraine medications; however, they have been inadequately explored. This has resulted in suboptimal usage of medications without effective altering of prescribing recommendations for patients, posing a risk for migraine chronification.

METHODS

Our aim is to conduct a comprehensive review of the available evidence regarding the underuse of migraine medications, both acute and preventive. The term "underuse" includes, but is not limited to: (1) ineffective use of appropriate and inappropriate medication; (2) underutilization; (3) inappropriate timing of usage; and (4) patient dissatisfaction with medication.

RESULTS

The underuse of both acute and preventive medications has been shown to contribute to the progression of migraine. In terms of acute medication, chronification occurs as a result of insufficient drug use, including failure of the prescriber to select the appropriate type based on pain intensity and disability, patients taking medication too late (more than 60 minutes after the onset or after central sensitization has occurred as evidenced by allodynia), and discontinuation because of lack of effect or intolerable side effects. The underlying cause of inadequate effectiveness of acute medication lies in its inability to halt the propagation of peripheral activation to central sensitization in a timely manner. For oral and injectable preventive migraine medications, insufficient efficacy and intolerable side effects have led to poor adherence and discontinuation with subsequent progression of migraine. The underlying pathophysiology here is rooted in the repetitive stimulation of afferent sensory pain fibers, followed by ascending brainstem pain pathways plus dysfunction of the endogenous descending brainstem pain inhibitory pathway. Although anti-calcitonin gene-related peptide (CGRP) medications partially address pain caused by the above factors, including decreased efficacy and tolerability from conventional therapy, some patients do not respond well to this treatment. Research suggests that initiating preventive anti-CGRP treatment at an early stage (during low frequency episodic migraine attacks) is more beneficial than commencing it during high frequency episodic attacks or when chronic migraine has begun.

CONCLUSIONS

The term "medication underuse" is underrecognized, but it holds significant importance. Optimal usage of acute care and preventive migraine medications could potentially prevent migraine chronification and improve the treatment of migraine attacks.

Evaluation of outcomes of calcitonin gene-related peptide (CGRP)-targeting therapies for acute and preventive migraine treatment based on patient sex

BACKGROUND

Women show increased prevalence and severity of migraine compared to men. Whether small molecule calcitonin gene-related peptide receptor (CGRP-R) antagonists (i.e., gepants) and monoclonal antibodies targeting either the CGRP-R or the CGRP peptide might show sexually dimorphic outcomes for acute and preventive therapy has not been established.

METHODS

We conducted a subpopulation analysis of available published data from FDA reviews to evaluate potential sex differences in the response rates of ubrogepant, rimegepant and zavegepant for acute migraine therapy. Available data from FDA reviews of erenumab, fremanezumab, galcanezumab and eptinezumab, approved CGRP-R and CGRP monoclonal antibodies and of atogepant were examined for prevention outcomes based on patient sex. Preventive outcomes were analyzed separately for patients with episodic migraine and chronic migraine.

RESULTS

In women, the three approved gepants produced statistically significant drug effects regardless of dose tested on the FDA mandated co-primary endpoints, the proportion of patients achieving two-hour pain-freedom and the proportion of patients free of their most bothersome symptom at two hours post-dose. In women, the average placebo-subtracted two-hour pain-freedom proportion was 9.5% (CI: 7.4 to 11.6) and the average numbers needed to treat was 11. The free from most bothersome symptom at two hours outcomes were also significant in women. The gepant drugs did not reach statistically significant effects on the two-hour pain-freedom endpoint in the men, with an average drug effect of 2.8% (CI: -2.5 to 8.2) and an average number needed to treat of 36. For freedom from most bothersome symptom at two hours post-dose endpoint, differences were not significant in male patients. The treatment effect in each of the gepant studies was always numerically greater in women than in men. In evaluation of prevention outcomes with the antibodies or atogepant using the change from the specified primary endpoint (e.g., monthly migraine days), the observed treatment effect for episodic migraine patients almost always favored drug over placebo in both women and men. For chronic migraine patients the treatment effects of antibodies were similar in men and women and always favored the drug treated group.Conclusion/Interpretation: Small molecule CGRP-R antagonists are effective in acute migraine therapy in women but available data do not demonstrate effectiveness in men. CGRP-targeting therapies are effective for migraine prevention in both male and female episodic migraine patients but possible sex differences remain uncertain. In male and female chronic migraine patients, CGRP/CGRP-R antibodies were similarly effective. The data highlight possible differential effects of CGRP targeted therapies in different patient populations and the need for increased understanding of CGRP neurobiology in men and women.

Potential mechanisms for osteopathic manipulative treatment to alleviate migraine-like pain in female rats

Introduction

Migraines are the leading cause of disability in the United States, and the use of non-pharmaceutical treatments like osteopathic manipulative treatment (OMT) has shown promise. Despite its potential, the lack of mechanistic understanding has hindered widespread adoption. This study aims to investigate the efficacy of OMT in treating acute migraines and unravel its underlying mechanisms of action.

Methods

Female rats were subjected to a "two-hit" approach to induce migraine-like pain. This involved bilateral injections of Complete Freund's Adjuvant (CFA) into the trapezius muscle (1st hit) followed by exposure to Umbellulone, a human migraine trigger, on Day 6 post-CFA (2nd hit). Soft tissue and articulatory techniques were applied to the cervical region for acute abortive or repeated prophylactic treatment. Cutaneous allodynia and trigeminal system activation were assessed through behavioral tests and immunohistochemical staining.

Results

Following Umbellulone inhalation, CFA-primed rats exhibited periorbital and hind paw allodynia. Immediate application of OMT after Umbellulone inhalation as an abortive treatment partially alleviated cutaneous allodynia. With OMT applied thrice as a prophylactic measure, complete suppression of tactile hypersensitivity was observed. Prophylactic OMT also prevented the increase of c-fos signals in the trigeminal nucleus caudalis and the elevation of calcitonin gene-related peptide expression in trigeminal ganglia induced by CFA and Umbellulone exposure at 2 h post-inhalation.

Discussion

These findings provide mechanistic insights into OMT's migraine-relief potential and underscore its viability as a non-pharmacological avenue for managing migraines.

Problems in management of medication overuse headache in transgender and gender non-conforming populations

Primary headache disorders, such as migraine, account for a significant portion of disability rates worldwide, yet patients still struggle to receive the adequate medical and emotional support necessary to improve health outcomes. Insufficient pain management through either impractical pharmaceutical treatments or absent emotional support networks can worsen physical and mental health outcomes since comorbidities commonly associated with headache include hypertension, diabetes, depression, and anxiety. A lack of awareness on headache pathology and its observable severity can lead to pain-related prejudice that destroys beneficial aspects of patient self-advocacy and self-efficacy, thus potentially discouraging the use of healthcare services in favor of maladaptive coping skills. Acute treatments for primary headache disorders include non-steroidal anti-inflammatory drugs (i.e., aspirin, ibuprofen), triptans (i.e., sumatriptan), and opioids; however, continuous use of these pain-relieving agents can generate a secondary headache known as medication overuse headache (MOH). Recent work highlighting the overlap of morphological and functional brain changes in MOH and substance use disorder (SUD) suggests that insufficient pain management encourages analgesic misuse. The LGBTQ+ community-specifically transgender and gender non-conforming persons-struggles with high rates of mental illness and substance abuse. Since gender-affirming sex hormone therapy influences migraine progression, transgender and gender non-conforming (trans*) patients on hormone therapy have a higher risk for worsening migraine symptoms. However, trans* patients are less likely to have access to appropriate pain management techniques, thus preventing positive health outcomes for this vulnerable population.

Risk factors for migraine disease progression: a narrative review for a patient-centered approach

BACKGROUND

In individuals with migraine, attacks may increase in frequency, severity, or both. Preventing migraine progression has emerged as a treatment goal in headache subspecialty practice, but there may be less awareness in general neurology or primary care settings where most people with migraine who seek treatment consult. Herein, we review the definition of and risk factors for migraine progression and consider strategies that could reduce its risk.

METHODS

A group of headache expert healthcare professionals, clinicians, and researchers reviewed published evidence documenting factors associated with increased or decreased rates of migraine progression and established expert opinions for disease management recommendations. Strength of evidence was rated as good, moderate, or based solely on expert opinion, using modified criteria for causation developed by AB Hill.

RESULTS

Migraine progression is commonly operationally defined as the transition from ≤ 15 to ≥ 15 monthly headache days among people with migraine; however, this does not necessarily constitute a fundamental change in migraine biology and other definitions should be considered. Established and theoretical key risk factors for migraine progression were categorized into five domains: migraine disease characteristics, treatment-related factors, comorbidities, lifestyle/exogenous factors, and demographic factors. Within these domains, good evidence supports the following risk factors: poorly optimized acute headache treatment, cutaneous allodynia, acute medication overuse, selected psychiatric symptoms, extra-cephalic chronic pain conditions, metabolism-related comorbidities, sleep disturbances, respiratory conditions, former/current high caffeine intake, physical inactivity, financial constraints, tobacco use, and personal triggers as risk factors. Protective actions that may mitigate migraine progression are sparsely investigated in published literature; our discussion of these factors is primarily based on expert opinion.

CONCLUSIONS

Recognizing risk factors for migraine progression will allow healthcare providers to suggest protective actions against migraine progression (Supplementary Fig. 1). Intervention studies are needed to weight the risk factors and test the clinical benefit of hypothesized mitigation strategies that emerge from epidemiological evidence.

Annexin A1 exerts analgesic effect in a mouse model of medication overuse headache

Medication overuse headache (MOH) is a serious global condition. The interaction between headache attacks and medication overuse complicates the understanding of its pathophysiology. In this study, we developed a preclinical MOH model that incorporates these two key factors by overusing rizatriptan benzoate (RIZ, 4 mg/kg, i.g.) in a glyceryl trinitrate (GTN, 10 mg/kg, i.p.) induced chronic migraine mouse model. We observed that RIZ overuse aggravated GTN-induced cutaneous allodynia and caused a prolonged state of latent sensitization. We also detected a significant upregulation of Annexin-A1 (ANXA1), a protein mainly expressed in the microglia of the spinal trigeminal nucleus caudalis (SPVC), in GTN+RIZ mice. Intracerebroventricular injection of ANXA1-derived peptide Ac2-26 trifluoroacetic acid (TFA) (5 μg/mouse) inhibited bright light stress (BLS) induced acute allodynia via the formyl peptide receptor (FPR) in GTN+RIZ mice. These results suggest that ANXA1 may have an analgesic effect in triptan-associated MOH and could potentially serve as a therapeutic target.

Cutaneous allodynia as predictor for treatment response in chronic migraine: a cohort study

BACKGROUND

Central sensitisation is an important mechanism in migraine chronification. It is presumed to occur in second and third order neurons sequentially, resulting in an analogous spatial distribution of cutaneous allodynia with cephalic and extracephalic symptoms. We investigated whether allodynia, and its subtypes based on spatial distribution and type of stimulus, predict response to treatment in chronic migraine patients.

METHODS

This study was conducted as part of the CHARM study (NTR3440), a randomized, double-blind, placebo-controlled trial in chronic migraine patients with medication overuse. We included 173 patients. The presence of cutaneous allodynia at baseline was established with the Allodynia Symptom Checklist. Primary endpoint was reversion from chronic to episodic migraine.

RESULTS

Of all patients, 74.6% reported cutaneous allodynia. Absence of allodynia compared to presence of allodynia was predictive for reversion from chronic to episodic migraine, odds ratio (OR): 2.45 (95% CI: 1.03-5.84), p = 0.042. The predictive value was more pronounced when subdivided for spatial distribution, for participants without allodynia versus cephalic (OR: 4.16 (95% CI: 1.21-14.30), p = 0.024) and extracephalic (OR: 7.32 (95% CI: 1.98- 27.11), p = 0.003) allodynia. Mechanical, but not thermal, allodynia, was associated with outcome.

CONCLUSIONS

Cutaneous allodynia, an important marker for central sensitization, likely has predictive value for treatment response in chronic 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.

Long-term efficacy and safety of erenumab in patients with chronic migraine and acute medication overuse: A subgroup analysis

OBJECTIVE

Assess the long-term efficacy and safety of erenumab in patients with chronic migraine with acute medication overuse.

BACKGROUND

Overuse of acute medication in patients with chronic migraine has been linked to greater pain intensity and disability and may diminish the effectiveness of preventive therapies.

METHODS

This 52-week open-label extension study followed a 12-week double-blind placebo-controlled study in which patients with chronic migraine were randomized 3:2:2 to placebo or once-monthly erenumab 70 mg or 140 mg. Patients were stratified by region and medication overuse status. Patients received erenumab 70 mg or 140 mg throughout or switched from erenumab 70 to 140 mg (based on protocol amendment to augment safety data at higher dose). Efficacy was assessed in patients with and without medication overuse at parent study baseline.

RESULTS

Of 609 patients enrolled in the extension study, 252/609 (41.4%) met the criteria for medication overuse at parent study baseline. At Week 52, the mean change in monthly migraine days from parent study baseline was -9.3 (95% confidence interval: -10.4, -8.1 days) in the medication overuse subgroup versus -9.3 (-10.1, -8.5 days) in the non-medication overuse subgroup (combined erenumab doses); proportion of patients achieving ≥50% reduction in monthly migraine days at Week 52 was 55.9% (90/161; 48.2%, 63.3%) versus 61.3% (136/222; 54.7%, 67.4%), respectively. Among baseline users of acute migraine-specific medication, the mean change in monthly migraine-specific medication days at Week 52 was -7.4 (-8.3, -6.4 days) in the medication overuse subgroup versus -5.4 (-6.1, -4.7 days) in the non-medication overuse subgroup. Most patients (197/298; 66.1%) in the medication overuse subgroup transitioned to non-overuse status by Week 52. Erenumab 140 mg was associated with numerically greater efficacy than erenumab 70 mg across all endpoints. No new safety signals were identified.

CONCLUSION

Long-term erenumab treatment demonstrated sustained efficacy and safety in patients with chronic migraine with and without acute medication overuse.

Expert consensus established around flexible, individualized migraine treatment utilizing a modified Delphi panel

OBJECTIVE

To characterize treatment decision-making processes and formalize consensus regarding key factors headache specialists consider in treatment decisions for patients with migraine, considering novel therapies.

BACKGROUND

Migraine therapies have long been subject to binary classification, acute versus preventive, due to limitations of available drugs. The emergence of novel therapies that can be used more flexibly creates an opportunity to rethink this binary classification. To determine the role of these novel therapies in treatment, it is critical to understand whether existing guidelines reflect clinical practice and to establish consensus around factors driving management.

METHODS

A three-round modified Delphi process was conducted with migraine clinical experts. Round 1 consisted of an online questionnaire; Round 2 involved an online discussion of aggregated Round 1 results; and Round 3 allowed participants to revise Round 1 responses, incorporating Round 2 insights. Questions elicited likelihood ratings (0 = highly unlikely to 100 = highly likely), rankings, and estimates on treatment decision-making.

RESULTS

Nineteen experts completed three Delphi rounds. Experts strongly agreed on definitions for "acute" (median = 100, inter-quartile range [IQR] = 5) and "preventive" treatment (median = 90, IQR = 15), but noted a need for treatment customization for patients (median = 100, IQR = 6). Experts noted certain aspects of guidelines may no longer apply based on established tolerability and efficacy of newer acute and preventive agents (median = 91, IQR = 17). Further, experts agreed on a treatment category referred to as "situational prevention" (or "short-term prevention") for patients with reliable and predictable migraine triggers (median = 100, IQR = 10) or time-limited periods when headache avoidance is important (median = 100, IQR = 12).

CONCLUSIONS

Using the modified Delphi method, a panel of migraine experts identified the importance of customizing treatment for people with migraine and the utility of "situational prevention," given the ability of new treatment options to meet this need and the potential to clinically identify patients and time periods when this approach would add value.

Autonomic symptoms in migraine: Results of a prospective longitudinal study

Objective

To assess the prevalence and burden of autonomic symptoms in migraine, and determine the relationship with migraine frequency.

Background

Autonomic symptoms in migraine have been theorized to occur in the setting of inter-ictal sympathetic hypoactivity and hyper-sensitivity. There is limited data prospectively assessing cranial and extra-cranial autonomic symptoms with a validated instrument, or longitudinal data on the relationship between migraine disease activity and autonomic symptoms.

Methods

Patients attending a single tertiary academic center were recruited into a prospective cohort study between September 2020 and June 2022. In addition to standard clinical care, they completed several surveys including the Composite Autonomic Symptom Scale (COMPASS-31) questionnaire, a validated survey of autonomic symptoms.

Results

A total of 43 patients (66.7% female, median age 42, IQR 17) were included in the final analysis. There was a baseline 20 monthly headache days (MHD) (IQR 21.7), and 65.1% of the population had chronic migraine by ICHD-3 criteria. A significantly elevated weighted COMPASS-31 score was reported in 60.5% of respondents (mean 30.3, SD 13.3) at baseline. After 12 months treatment, significant improvements were reported in migraine frequency (median MHD 20-8.7) and disability (median Migraine Disability Assessment Score 67-48), but not in autonomic symptoms (mean score 30.3, SD 11.2).

Conclusion

Autonomic symptoms were frequently reported in patients with migraine. However, they did not correlate with headache frequency or reversion to episodic frequency. Further study is required to elucidate specific approaches and treatments for autonomic symptoms, and further evaluate the underlying pathophysiological mechanisms.

Efficacy of Ubrogepant in the Acute Treatment of Migraine With Mild Pain vs Moderate or Severe Pain

BACKGROUND AND OBJECTIVES

To examine the efficacy of ubrogepant in the treatment of migraine with mild vs moderate or severe pain.

METHODS

This was a phase 3, open-label, dose-blinded, 52-week extension trial. Adults with migraine were randomized 1:1:1 (usual care, ubrogepant 50 mg, or ubrogepant 100 mg). Participants treated up to 8 migraine attacks of any pain intensity every 4 weeks. Efficacy outcomes (only collected for ubrogepant) included 2-hour pain freedom (2hPF), freedom from associated symptoms, and from disability. A generalized linear mixed model with binomial distribution and logit link function was used to assess the influence of baseline pain intensity on treatment outcomes in this post hoc analysis.

RESULTS

Data for 19,291 attacks from 808 participants were included. 2hPF rates were higher for attacks treated when pain was mild vs moderate or severe: ubrogepant 50 mg (47.1% vs 23.6%; odds ratio [95% CI] 2.89 [2.57-3.24]) and ubrogepant 100 mg (55.2% vs 26.1%; 3.50 [3.12-3.92]; p < 0.0001 both doses). Rates of freedom from photophobia, phonophobia, and nausea 2 hours after treatment were also significantly higher following the treatment of mild vs moderate or severe pain (p < 0.001 all symptoms, both doses). At 2 hours, the proportion of attacks with normal function was more than double for both doses of ubrogepant (p < 0.001). The most common adverse event was upper respiratory tract infection (∼11% both doses). Serious adverse events were reported by 2% in ubrogepant 50 mg and 3% in ubrogepant 100 mg.

DISCUSSION

Relative to treatment of attacks with moderate or severe pain, treatment with ubrogepant during mild pain resulted in significantly higher rates of freedom from pain, freedom from associated symptoms, and achieving normal function 2 hours after administration.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov, NCT02873221.

CLASSIFICATION OF EVIDENCE

This trial provides Class III evidence that treatment of migraine with ubrogepant when pain is mild vs moderate or severe increases the likelihood of achieving pain freedom, absence of symptoms, and normal function within 2 hours postdose.

Pathophysiology of Chronic Migraine: Insights from Recent Neuroimaging Research

PURPOSE OF REVIEW

Chronic migraine (CM) is a highly disabling primary headache disorder with a substantial impact on patients' quality of life. Episodic migraine (EM) and CM are dynamic states; CM usually evolves from EM alongside increased headache frequency, comorbidities, and medication overuse, supporting the notion that migraine is a spectrum disorder. This narrative review aims to summarize neuroimaging studies to better understand the pathophysiology of CM.

RECENT FINDINGS

Positron emission tomography studies have revealed abnormal energy metabolism and metabolic changes in the dorsal rostral pons in individuals with CM, suggesting that this structure has a key role in the pathophysiology of migraine generation and chronification. Magnetic resonance spectroscopy studies have suggested that thalamocortical pathway dysfunction may contribute to migraine chronification, while functional magnetic resonance imaging studies have highlighted that hypothalamic activity may be involved. Recent evidence highlights functional and structural alterations in cortical and subcortical pain-related brain regions in patients with CM. Whether these functional and structural abnormalities of the brain cause migraine chronification or are a consequence of repeated attacks is still debated. In the future, imaging patterns that predict the transformation from EM to CM should be identified.

HCN2 Ion Channels Drive Pain in Rodent Models of Migraine

Migraine is believed to be initiated by neuronal activity in the CNS, that triggers excitation of nociceptive trigeminal ganglion (TG) nerve fibers innervating the meninges and thus causes a unilateral throbbing headache. Drugs that precipitate or potentiate migraine are known to elevate intracellular levels of the cyclic nucleotides cAMP or cGMP, while anti-migraine treatments couple to signaling pathways that reduce cAMP or cGMP, suggesting an involvement of these cyclic nucleotides in migraine. Members of the HCN ion channel family are activated by direct binding of cAMP or cGMP, suggesting in turn that a member of this family may be a critical trigger of migraine. Here, we show that pharmacological block or targeted genetic deletion of HCN2 abolishes migraine-like pain in three rodent migraine models (in both sexes). Induction of migraine-like pain in these models triggered expression of the protein C-FOS, a marker of neuronal activity, in neurons of the trigeminocervical complex (TCC), where TG neurons terminate, and C-FOS expression was reversed by peripheral HCN2 inhibition. HCN2 block in vivo inhibited both evoked and spontaneous neuronal activity in nociceptive TG neurons. The NO donor glyceryl trinitrate (GTN) caused an increase in cGMP in the TG in vivo Exposing isolated TG neurons to GTN caused a rightward shift in the voltage dependence of HCN currents and thus increased neuronal excitability. This work identifies HCN2 as a novel target for the development of migraine treatments.SIGNIFICANCE STATEMENT Migraine is believed to be initiated by localized excitability of neurons within the CNS, but the most disturbing symptom, the characteristic throbbing migraine headache pain, is widely agreed to be caused by activity in afferent pain-sensitive (nociceptive) nerve fibers of the trigeminal nerve. Using a variety of preclinical models of migraine, we identify the HCN2 ion channel as the molecular source of trigeminal hyperexcitability in migraine and we show that pharmacological or genetic inhibition of HCN2 can relieve migraine-like pain symptoms. The work highlights the HCN2 ion channel as a potential pharmacological target for the development of novel analgesics effective in migraine.

Neurobiology of migraine progression

Chronic migraine is one of the most devastating headache disorders. The estimated prevalence is 1.4-2.2% in the population. The factors which may predispose to the process of migraine progression include high frequency of migraine attacks, medication overuse, comorbid pain syndromes, and obesity. Several studies showed that chronic migraine results in the substantial anatomical and physiological changes in the brain. Despite no clear explanation regarding the pathophysiologic process leading to the progression, certain features such as increased sensory sensitivity, cutaneous allodynia, impaired habituation, identify the neuronal hyperexcitability as the plausible mechanism. In this review, we describe two main mechanisms which can lead to this hyperexcitability. The first is persistent sensitization caused by repetitive and prolonged trigeminal nociceptive activation. This process results in changes in several brain networks related to both pain and non-pain behaviours. The second mechanism is the decrease in endogenous brainstem inhibitory control, hence increasing the excitability of neurons in the trigeminal noceptive system and cerebral cortex. The combination of increased pain matrix connectivity, including hypothalamic hyperactivity and a weak serotonergic system, may contribute to migraine chronification.

Migraine susceptibility is modulated by food triggers and analgesic overuse via sulfotransferase inhibition

Background/aim

Certain constituents in migraine food triggers and non-steroidal anti-inflammatory drugs (NSAIDs) inhibit sulfotransferases (SULTs) that detoxify drugs/chemicals and play role in the metabolism of neurotransmitters. We aimed to dissect SULT1A1 modulation of CSD susceptibility and behavior in an in vivo experimental model using hesperidin, a SULT1A1 inhibitor found in citrus fruits (known migraine triggers) and mefenamic acid (SULT1A1 inhibitor), an NSAID to simulate medication overuse.

Methods

Hesperidin was used as SULT1A1 inhibitor found in citrus fruits, known migraine triggers and mefenamic acid (NSAID), another SULT1A1 inhibitor, was used to induce MO in rats. The groups were; 1) Hesperidin (ip) or its vehicle-DMSO (ip) 2) Chronic (4 weeks) mefenamic acid (ip) or its vehicle (ip) 3) Chronic mefenamic acid+hesperidin (ip) or DMSO (ip). CSD susceptibility was evaluated and behavioral testing was performed. SULT1A1 enzyme activity was measured in brain samples.

Results

Single-dose of hesperidin neither changed CSD susceptibility nor resulted in any behavioral change. Chronic mefenamic acid exposure resulted in increased CSD susceptibility, mechanical-thermal hypersensitivity, increased head shake, grooming and freezing and decreased locomotion. Single dose hesperidin administration after chronic mefenamic acid exposure resulted in increased CSD susceptibility and mechanical-thermal hypersensitivity, increased freezing and decreased locomotion. SULT1A1 enzyme activity was lower in mefenamic acid and mefenamic acid+hesperidin groups compared to their vehicles.

Conclusion

Mefenamic acid and hesperidin have synergistic effect in modulating CSD susceptibility and pain behavior. Sulfotransferase inhibition may be the common mechanism by which food triggers and NSAIDs modulate migraine susceptibility. Further investigations regarding human provocation studies using hesperidin in migraine patients with medication overuse are needed.

Gray matter alteration in medication overuse headache: a coordinates-based activation likelihood estimation meta-analysis

Medication overuse headache (MOH) is a prevalent secondary headache, bringing heavy economic burden and neuropsychological damage. Neuroimaging studies on the disease reported divergent results. To merge the reported neuroimaging alterations in MOH patients and explore a pathophysiological mechanism of this disorder. A meta-analytic activation likelihood estimation (ALE) analysis method was used. We systematically searched English and Chinese databases for both morphological and functional neuroimaging studies published before Nov 18, 2021. Reported altered brain regions and the stereotactic coordinates of their peaks were extracted and pooled by GingerALE using Gaussian probability distribution into brain maps, illustrating converged regions of alteration among studies. We identified 927 articles, of which five studies on gray matter changes, using voxel-based morphometry (VBM) were eventually included for ALE analysis, with 344 subjects and 54 coordinates put into GingerALE. No functional magnetic resonance imaging (fMRI) or positron emission topography (PET) studies were included for pooling. Compared with healthy controls (HCs), MOH featured increased gray matter density in midbrain, striatum, cingulate, inferior parietal cortex and cerebellum (P < 0.001 uncorrected), whereas decreased gray matter density in orbitofrontal cortex (P < 0.05, family-wise error), frontal, insular and parietal cortices (P < 0.001 uncorrected). Withdrawal of analgesics led to decreased gray matter density in superior temporal gyrus, cuneus, midbrain and cerebellum (P < 0.001 uncorrected). This meta-analysis confirmed that medication overuse headache is associated with morphologic alteration in the reward system, the prefrontal cortex and a reversible modification in the pain network. Further functional imaging paradigms and longitudinal studies are required for a more definite conclusion and a causal mechanism.

Innovations and advances in modelling and measuring pain in animals

Best practices in preclinical algesiometry (pain behaviour testing) have shifted over the past decade as a result of technological advancements, the continued dearth of translational progress and the emphasis that funding institutions and journals have placed on rigour and reproducibility. Here we describe the changing trends in research methods by analysing the methods reported in preclinical pain publications from the past 40 years, with a focus on the last 5 years. We also discuss how the status quo may be hampering translational success. This discussion is centred on four fundamental decisions that apply to every pain behaviour experiment: choice of subject (model organism), choice of assay (pain-inducing injury), laboratory environment and choice of outcome measures. Finally, we discuss how human tissues, which are increasingly accessible, can be used to validate the translatability of targets and mechanisms identified in animal pain models.

New Oral Drugs for Migraine

Migraine is a common and disabling neurological disorder, with several manifestations, of which pain is just one. Despite its worldwide prevalence, there remains a paucity of targeted and effective treatments for the condition, leaving many of those affected underserved by available treatments. Work over the last 30+ years has recently led to the emergence of the first targeted acute and preventive treatments in our practice since the triptan era in the early 1990s, which are changing the landscape of migraine treatment. These include the monoclonal antibodies targeting calcitonin gene-related peptide or its receptor. Evolving work on novel therapeutic targets, as well as continuing to exploit drugs used in other disorders that may also have a therapeutic effect in migraine, is likely to lead to more and more treatments being able to be offered to migraineurs. Future work involves the development of agents that lack vasoconstrictive effects, such as lasmiditan, do not contribute to medication overuse, such as the gepants, and do not interact with other drugs that may be used for the disorder, as well as agents that can act both acutely and preventively, thereby utilising the quantum between acute and preventive drug effects which has been demonstrated with different migraine drugs before. Here we discuss the evolution of oral migraine treatments over the last 5 years, including those that have gained regulatory approval and reached clinical practice, those in development and potential other targets for the future.

Safety and Risk of Medication Overuse Headache in Lasmiditan and Second-Generation Gepants: A Rapid Review

The treatment of migraine is often complicated by insufficient headache relief, a miscellany of side effects and the risk of developing Medication Overuse Headache (MOH). Novel acute therapies have been recently developed and are now in the early post-marketing phase. Lasmiditan is a highly selective serotonin receptor agonist that binds to the 5-HT_1F receptor, while ubrogepant and rimegepant antagonize the calcitonin gene-related peptide receptor. All three medications are now prescribed in a real-world setting, and an adequate level of knowledge is the starting point for rational use. In this rapid systematic review, we have established what is known about lasmiditan, ubrogepant and rimegepant, highlighting the most relevant safety aspects available from published studies and speculating about their risk of MOH.

Protein kinase Cδ as a neuronal mechanism for headache in a chronic intermittent nitroglycerin model of migraine in mice

ABSTRACT

Migraine is one of the most common neurological disorders characterized by recurrent attacks of typically throbbing and unilateral headaches, affecting up to 20% of the population worldwide. Despite the high prevalence and severity of this primary headache disorder, it remains to be a challenge to fully understand and treat migraine headaches. By characterizing and validating a mouse migraine model, this study aimed to investigate the functional contribution of protein kinase C (PKC) isoforms in migraine. In this study, we identified the presence of migraine-like ongoing pain in mice after chronic intermittent treatment with nitroglycerin (NTG). The peptide antagonist of calcitonin gene-related peptide α-CGRP (8-37), but not topiramate nor sumatriptan, effectively blocked ongoing pain and elicited pain relief-induced conditioned place preference in NTG-treated mice. Prominent activation of PKCδ was observed in chronic NTG-treated mice. Functional inhibition of PKCδ significantly attenuated ongoing spontaneous pain in chronic NTG-treated mice. Furthermore, we recapitulated the NTG-triggered migraine behavior in wild-type mice, but not in PKCδ-null mice. In response to repeated administration of NTG, ongoing spontaneous pain was not developed in mice lacking the specific PKC isoform. This study identified the presence of ongoing pain in mice treated with NTG, a known human migraine trigger that closely resembles the common manifestation of spontaneous migraine attacks in humans. These findings demonstrated a critical regulatory role of PKCδ in migraine pathophysiology, which may offer new pharmacological targets for antimigraine treatment.

Chronic Migraine Pathophysiology and Treatment: A Review of Current Perspectives

Chronic migraine is a disabling neurological disorder that imposes a considerable burden on individual and socioeconomic outcomes. Chronic migraine is defined as headaches occurring on at least 15 days per month with at least eight of these fulfilling the criteria for migraine. Chronic migraine typically evolves from episodic migraine as a result of increasing attack frequency and/or several other risk factors that have been implicated with migraine chronification. Despite this evolution, chronic migraine likely develops into its own distinct clinical entity, with unique features and pathophysiology separating it from episodic migraine. Furthermore, chronic migraine is characterized with higher disability and incidence of comorbidities in comparison to episodic migraine. While existing migraine studies primarily focus on episodic migraine, less is known about chronic migraine pathophysiology. Mounting evidence on aberrant alterations suggest that pronounced functional and structural brain changes, central sensitization and neuroinflammation may underlie chronic migraine mechanisms. Current treatment options for chronic migraine include risk factor modification, acute and prophylactic therapies, evidence-based treatments such as onabotulinumtoxinA, topiramate and newly approved calcitonin gene-related peptide or receptor targeted monoclonal antibodies. Unfortunately, treatments are still predominantly ineffective in aborting migraine attacks and decreasing intensity and frequency, and poor adherence and compliance with preventative medications remains a significant challenge. Novel emerging chronic migraine treatments such as neuromodulation offer promising therapeutic approaches that warrant further investigation. The aim of this narrative review is to provide an update of current knowledge and perspectives regarding chronic migraine background, pathophysiology, current and emerging treatment options with the intention of facilitating future research into this debilitating and largely indeterminant disorder.

Candidate Genes and Proteomic Biomarkers of Serum and Urine in Medication-Overuse Headache

Chronic headache is a topical problem of neurology, psychiatry and general practice. The medication-overuse headache (MOH) is one of the leading pathologies in the structure of chronic headache. However, early diagnosis of the MOH is challenging. We analyzed potential proteomic biomarkers of serum and urine in patients with MOH.

METHODS

We searched PubMed, Springer, Scopus, Web of Science, ClinicalKey, and Google Scholar databases for English publications over the past 10 years using keywords and their combinations.

RESULTS

We found and analyzed seven studies that met the search criteria for the purpose of the review, including 24 serum proteomic biomarkers and 25 urine proteomic biomarkers of MOH. Moreover, the candidate genes and locus of the studied serum (vitamin D-binding protein, lipocalin-type prostaglandin D2 synthase, apolipoprotein E, etc.) and urine proteomic biomarkers (uromodulin, alpha-1-microglobulin, zinc-alpha-2-glycoprotein, etc.) of MOH are presented in this review.

CONCLUSIONS

The serum and urine proteomic biomarkers of MOH can potentially help with the identification of patients with MOH development. Due to the relevance of the problem, the authors believe that further investigation of the MOH proteomic biomarkers in different ethnic and racial groups of patients with primary headache is necessary. In addition, it is important to investigate whether medications of different drug classes influence the levels of serum and urine proteomic biomarkers.

Selective targeting of peripheral cannabinoid receptors prevents behavioral symptoms and sensitization of trigeminal neurons in mouse models of migraine and medication overuse headache

ABSTRACT

Migraine affects ∼15% of the world's population greatly diminishing their quality of life. Current preventative treatments are effective in only a subset of migraine patients, and although cannabinoids seem beneficial in alleviating migraine symptoms, central nervous system side effects limit their widespread use. We developed peripherally restricted cannabinoids (PRCBs) that relieve chronic pain symptoms of cancer and neuropathies, without appreciable central nervous system side effects or tolerance development. Here, we determined PRCB effectiveness in alleviating hypersensitivity symptoms in mouse models of migraine and medication overuse headache. Long-term glyceryl trinitrate (GTN, 10 mg/kg) administration led to increased sensitivity to mechanical stimuli and increased expression of phosphorylated protein kinase A, neuronal nitric oxide synthase, and transient receptor potential ankyrin 1 proteins in trigeminal ganglia. Peripherally restricted cannabinoid pretreatment, but not posttreatment, prevented behavioral and biochemical correlates of GTN-induced sensitization. Low pH-activated and allyl isothiocyanate-activated currents in acutely isolated trigeminal neurons were reversibly attenuated by PRCB application. Long-term GTN treatment significantly enhanced these currents. Long-term sumatriptan treatment also led to the development of allodynia to mechanical and cold stimuli that was slowly reversible after sumatriptan discontinuation. Subsequent challenge with a previously ineffective low-dose GTN (0.1-0.3 mg/kg) revealed latent behavioral sensitization and increased expression of phosphorylated protein kinase A, neuronal nitric oxide synthase, and transient receptor potential ankyrin 1 proteins in trigeminal ganglia. Peripherally restricted cannabinoid pretreatment prevented all behavioral and biochemical correlates of allodynia and latent sensitization. Importantly, long-term PRCB treatment alone did not produce any behavioral or biochemical signs of sensitization. These data validate peripheral cannabinoid receptors as potential therapeutic targets in migraine and medication overuse headache.

The Evolution of Medication Overuse Headache: History, Pathophysiology and Clinical Update

Medication overuse headache (MOH), the development or worsening of chronic headache resulting from frequent and excessive intake of medications used for acute treatment of headache, is a common secondary headache disorder and is associated with significant personal and societal burdens. The plausible physiologic mechanism is that chronic exposure to acute care migraine treatment leads to suppression of endogenous antinociceptive systems, consequently facilitating the trigeminal nociceptive process via up-regulation of the calcitonin gene-related peptide (CGRP) system. Recognizing and preventing its development is an integral aspect of migraine management, as medication overuse is a modifiable risk factor in the progression from episodic to chronic migraine. Over the years, MOH has been difficult to treat and has generated much controversy. Ongoing debates exist over the diagnostic criteria and treatment strategies, particularly regarding the roles of formal detoxification and preventive treatment. The arrival of the anti-CGRP monoclonal antibodies has also challenged our views of MOH and its treatment. This review outlines the evolution of MOH diagnostic criteria, presents the current understanding of MOH pathogenesis and discusses the debates over its development and treatment. Data on the efficacy of anti-CGRP monoclonal antibodies in the setting of medication overuse is also presented. These results indicate that patients with medication overuse, who are treated with these new medications, may not need to be detoxified in order to treat MOH. In light of these developments, it is likely that in the future MOH will be more readily diagnosed and treatment will result in better outcomes.

Chronic migraine: Genetics or environment?

BACKGROUND

The transition from episodic migraine to chronic migraine, migraine chronification, is usually a gradual process, which involves multiple risk factors. To date, studies of the genetic risk factors for chronic migraine have focused primarily on candidate-gene approaches using healthy individuals as controls.

AIMS AND METHODS

In this study, we used a large cohort of migraine families and unrelated migraine patients (n > 2200) with supporting genotype and whole-genome sequencing data. We evaluated whether there are any genetic variants, common or rare, with a specific association to chronic migraine compared with episodic migraine.

RESULTS

We found no aggregation of chronic migraine in families with a clustering of migraine. No specific rare variants gave rise to migraine chronification, and migraine chronification was not associated with a higher polygenic risk score. Migraine chronification was not associated with allelic associations with an odds ratio above 2.65. Assessment of effect sizes with genome-wide significance below an odds ratio of 2.65 requires a genome-wide association study of at least 7500 chronic migraine patients.

CONCLUSION

Our results suggest that migraine chronification is caused by environmental factors rather than genetic factors.

Medication overuse and drug addiction: a narrative review from addiction perspective

Chronic headache is particularly prevalent in migraineurs and it can progress to a condition known as medication overuse headache (MOH). MOH is a secondary headache caused by overuse of analgesics or other medications such as triptans to abort acute migraine attacks. The worsening of headache symptoms associated with medication overuse (MO) generally ameliorates following interruption of regular medication use, although the primary headache symptoms remain unaffected. MO patients may also develop certain behaviors such as ritualized drug administration, psychological drug attachment, and withdrawal symptoms that have been suggested to correlate with drug addiction. Although several reviews have been performed on this topic, to the authors best knowledge none of them have examined this topic from the addiction point of view. Therefore, we aimed to identify features in MO and drug addiction that may correlate. We initiate the review by introducing the classes of analgesics and medications that can cause MOH and those with high risk to produce MO. We further compare differences between sensitization resulting from MO and from drug addiction, the neuronal pathways that may be involved, and the genetic susceptibility that may overlap between the two conditions. Finally, ICHD recommendations to treat MOH will be provided herein.

Chronic Migraine and Medication Overuse Headache Worsening After OnabotulinumtoxinA Withdrawn Due to the Severe Acute Respiratory Syndrome-Coronavirus-2 Pandemic

Introduction: OnabotulinumtoxinA (BT-A) is a preventive treatment for chronic migraine (CM), which needs to be administered regularly by a trained clinician every 3 months. The spread of the severe acute respiratory syndrome coronavirus-2 pandemic has forced many patients to momentarily stop the scheduled BT-A injections. The goal of this study was to explore whether those patients experienced a worsening of their CM and, if any, the clinical predictors of migraine worsening after BT-A withdrawal.

Methods: This was a retrospective, multicenter study. Patients' clinical data were obtained from their clinical documentation stored at each center. In particular, the following variables were collected: the mean number of headache days in the last month (NHD), the average number of painkillers taken in the last month (AC), the average number of days in which patients took, at least, one painkiller in the last month (NDM), the average intensity of migraine using the numeric rating scale (NRS) score in the last month, and the average score obtained at the six-item Headache Impact Test. The variables mentioned earlier were compared before and after BT-A withdrawal.

Results: After BT-A suspension, there was a significant increase in the NHD (P = 0.0313, Kruskal–Wallis rank test), AC (P = 0.0421, Kruskal–Wallis rank test), NDM (P = 0.0394, paired t-test), NRS score (P = 0.0069, Kruskal–Wallis rank test), and six-item Headache Impact Test score (P = 0.0372, Kruskal–Wallis rank test). Patients who were not assuming other preventive treatments other than BT-A displayed similar results. Patients who experienced a >30% worsening in NHD after BT-A was withdrawn displayed a longer CM history (P = 0.001, Kruskal–Wallis rank test), a longer MOH duration (P = 0.0017, Kruskal–Wallis rank test), a higher AC value at the baseline (P = 0.0149, Kruskal–Wallis rank test), a higher NDM (P = 0.0024, t-test), and a higher average value of the NRS score (P = 0.0073, Kruskal–Wallis rank test).

Conclusion: BT-A withdrawn during severe acute respiratory syndrome coronavirus-2 pandemic was associated with a general worsening in patients suffering from CM, hence the need to continue BT-A injection to avoid patients' worsening.

Involvement of 5-Hydroxytryptamine Receptor 2A in the Pathophysiology of Medication-Overuse Headache

Background

Recent studies indicated that analgesic overuse upregulated 5-hydroxytryptamine receptor 2A (5-HT_2AR) and subsequently activated nitric oxide synthase (NOS) and thus induced latent sensitization, which provided a mechanistic basis for medication-overuse headache (MOH). Moreover, glycogen synthase kinase-3β (GSK-3β) was regulated by serotonin receptors and the phosphorylation of GSK-3β affected NOS activity, indicating that GSK-3β could be involved in the regulation of NOS activity by 5-HT_2AR in MOH pathophysiology. Herein, we performed this study to investigate the role of 5-HT_2AR in MOH pathophysiology and the role of GSK-3β in the regulation of NOS activity by 5-HT_2AR.

Materials and Methods

Wistar rats were daily administered with paracetamol (200 mg/kg) for 30 days to set animal models for pre-clinical MOH research. After the rat MOH models were successfully established, the expression of 5-HT_2AR and NOS, GSK-3β activity in trigeminal nucleus caudalis (TNC) were assayed. Then, 5-HT_2AR antagonist ketanserin and agonist DOI were applied to investigate the effect of 5-HT_2AR on NOS activity in TNC of MOH rats, and GSK-3β antagonist LiCl and agonist perifosine were applied to explore the role of GSK-3β in the activation of NOS by 5-HT_2AR.

Results

We found that the expression of 5-HT_2AR and NOS, GSK-3β activity were enhanced in TNC of MOH rats. 5-HT_2AR modulator regulated the activity of NOS and GSK-3β in TNC of MOH rats, and drugs acting on GSK-3β affected NOS activity.

Conclusion

These data suggest that GSK-3β may mediate the activation of NOS by 5-HT_2AR and underline the role of 5-HT_2AR in MOH pathophysiology.

Plasma levels of CGRP and expression of specific microRNAs in blood cells of episodic and chronic migraine subjects: towards the identification of a panel of peripheral biomarkers of migraine?

Background

Migraine can manifest with an episodic or a chronic pattern in a continuum of disease severity. Multiple factors are associated with the progression of the pattern from episodic to chronic. One of the most consistently reported factors is the overuse of medications (MO) for the acute treatment of migraine attacks. The mechanisms through which MO facilitates the transformation of episodic migraine (EM) into chronic migraine (CM) are elusive. In order to provide insights into these mechanisms, the present study aims to identify possible peripheral biomarkers associated with the two forms of migraine, and with the presence of MO.

Methods

We evaluated the plasma levels of calcitonin gene-related peptide (CGRP) and the expression of miR-34a-5p and miR-382-5p in peripheral blood mononuclear cells of subjects with EM (n = 27) or CM-MO (n = 28). Subjects in the CM-MO group were also tested 2 months after an in-hospital detoxification protocol.

Results

CGRP, miR-382-5p, and miR-34a-5p levels were significantly higher in CM-MO subjects when compared to EM patients (p = 0.003 for all comparisons). After correcting for age, sex, and disease duration, miRNAs expression was still significantly associated with migraine phenotype (EM vs. CM-MO: p = 0.014 for miR-382-5p, p = 0.038 for miR-34a-5p), while CGRP levels were not (p = 0.115). CGRP plasma levels significantly and positively correlated with miR-382-5p (Spearman’s rho: 0.491, p = 0.001) and miR-34a-5p (Spearman’s rho: 0.303, p =0.025) in the overall population. In the CM-MO group, detoxification significantly decreased CGRP levels and miRNAs expression (p = 0.001). When comparing responders and non-responders to the detoxification, the former group (n = 23) showed significantly higher levels of CGRP at baseline, and significantly lower expression of miR-382-5p after the detoxification.

Conclusions

Our findings identify a potential panel of peripheral markers associated with migraine subtypes and disease severity. CGRP levels as well as miRNAs expression were influenced by MO, and modulated by detoxification in subjects with CM-MO.

Trial registration

The study protocol was registered at www.clinicaltrials.gov (NCT04473976).

Differential medication overuse risk of novel anti-migraine therapeutics

Medication overuse headache is estimated to affect 2% of the population, and is ranked in the top 20 most disabling disorders due to its high level of disability. Several therapies used in the treatment of acute migraine are thought to be associated with medication overuse headache, including opioids and triptans. With limited treatment options, it is critical to determine the risk profile of novel therapies prior to their widespread use. The current study explores the potential medication overuse risk of two novel therapeutic drug classes, namely the ditans: 5-HT1F receptor agonists, and the gepants: calcitonin gene-related peptide receptor antagonists, in a preclinical model of medication overuse. Persistent exposure of mice to the 5-HT1F agonist LY344864, but not olcegepant produced a significant reduction in hind paw and orofacial mechanical withdrawal thresholds as a surrogate readout of allodynia. In agreement, only LY344864 induced neuroplastic changes in trigeminal sensory afferents, increasing calcitonin gene-related peptide expression and basal trigeminal nociception. Our data highlight a differential medication overuse headache risk profile for the ditan and gepant classes of drugs that has important implications for their clinical use and patient education to help reduce the burden of medication overuse headache.

Role of CGRP in Neuroimmune Interaction via NF-κB Signaling Genes in Glial Cells of Trigeminal Ganglia

Activation of the trigeminal system causes the release of various neuropeptides, cytokines, and other immune mediators. Calcitonin gene-related peptide (CGRP), which is a potent algogenic mediator, is expressed in the peripheral sensory neurons of trigeminal ganglion (TG). It affects the inflammatory responses and pain sensitivity by modulating the activity of glial cells. The primary aim of this study was to use array analysis to investigate the effect of CGRP on the glial cells of TG in regulating nuclear factor kappa B (NF-κB) signaling genes and to further check if CGRP in the TG can affect neuron-glia activation in the spinal trigeminal nucleus caudalis. The glial cells of TG were stimulated with CGRP or Minocycline (Min) + CGRP. The effect on various genes involved in NF-κB signaling pathway was analyzed compared to no treatment control condition using a PCR array analysis. CGRP, Min + CGRP or saline was directly injected inside the TG and the effect on gene expression of Egr1, Myd88 and Akt1 and protein expression of cleaved Caspase3 (cleav Casp3) in the TG, and c-Fos and glial fibrillary acidic protein (GFAP) in the spinal section containing trigeminal nucleus caudalis was analyzed. Results showed that CGRP stimulation resulted in the modulation of several genes involved in the interleukin 1 signaling pathway and some genes of the tumor necrosis factor pathway. Minocycline pre-treatment resulted in the modulation of several genes in the glial cells, including anti-inflammatory genes, and neuronal activation markers. A mild increase in cleav Casp3 expression in TG and c-Fos and GFAP in the spinal trigeminal nucleus of CGRP injected animals was observed. These data provide evidence that glial cells can participate in neuroimmune interaction due to CGRP in the TG via NF-κB signaling pathway.

Ubrogepant does not induce latent sensitization in a preclinical model of medication overuse headache

BACKGROUND

Ubrogepant, a small-molecule calcitonin gene-related peptide receptor antagonist, was recently approved as an oral medication for the acute treatment of migraine. This study aimed to determine whether ubrogepant shows efficacy in a preclinical model of migraine-like pain and whether repeated oral administration of ubrogepant induces latent sensitization relevant to medication overuse headache in rats.

METHODS

A "two-hit" priming model of medication overuse headache was used. Female Sprague-Dawley rats received six oral doses of sumatriptan 10 mg/kg over 2 weeks to induce latent sensitization (i.e. "priming"). Cutaneous allodynia was measured periodically over 20 days in the periorbital and hindpaw regions using von Frey filaments. The rats were then subjected to a 1-hour bright light stress challenge on two consecutive days. At the start of the second bright light stress exposure, oral sumatriptan 10 mg/kg, oral ubrogepant 25, 50, or 100 mg/kg, or vehicle was administered; thereafter, cephalic and hindpaw sensory thresholds were monitored hourly over 5 hours to determine the efficacy of ubrogepant in reversing bright light stress-induced cutaneous allodynia. A dose of ubrogepant effective in the medication overuse headache model (100 mg/kg) was then selected to determine if repeated administration would produce latent sensitization. Rats were administered six oral doses of ubrogepant 100 mg/kg, sumatriptan 10 mg/kg (positive control), or vehicle over 2 weeks, and cutaneous allodynia was evaluated regularly. Testing continued until mechanosensitivity returned to baseline levels. Rats were then challenged with bright light stress on days 20 and 21, and periorbital and hindpaw cutaneous allodynia was measured. On days 28 to 32, the same groups received a nitric oxide donor (sodium nitroprusside 3 mg/kg, i.p.), and cutaneous allodynia was assessed hourly over 5 hours.

RESULTS

Sumatriptan elicited cutaneous allodynia in both cephalic and hindpaw regions; cutaneous allodynia resolved to baseline levels after cessation of drug administration (14 days). Sumatriptan priming resulted in generalized and delayed cutaneous allodynia, evoked by either bright light stress (day 21) or nitric oxide donor (day 28). Ubrogepant dose-dependently blocked both stress- and nitric oxide donor-induced cephalic and hindpaw allodynia in the sumatriptan-induced medication overuse headache model with a 50% effective dose of ∼50 mg/kg. Unlike sumatriptan, ubrogepant 100 mg/kg in repeated effective doses did not produce cutaneous allodynia or latent sensitization.

CONCLUSIONS

Both ubrogepant and sumatriptan demonstrated efficacy as acute medications for stress- and nitric oxide donor-evoked cephalic allodynia in a preclinical model of medication overuse headache, consistent with their clinical efficacy in the acute treatment of migraine. However, in contrast to sumatriptan, repeated treatment with ubrogepant did not induce cutaneous allodynia or latent sensitization. These studies suggest ubrogepant may offer an effective acute treatment of migraine without risk of medication overuse headache.Trial Registration Number: Not applicable.

Evaluation of LY573144 (lasmiditan) in a preclinical model of medication overuse headache

BACKGROUND

Medication overuse is a significant issue that complicates the treatment of headache disorders. The most effective medications for the acute treatment of migraine all have the capacity to induce medication overuse headache (MOH). Novel acute migraine-specific treatments are being developed. However, because the mechanism(s) underlying medication overuse headache are not well understood, it is difficult to predict whether any particular acute medication will induce MOH in susceptible individuals. LY573144 (lasmiditan), a 5-HT_1F receptor agonist, has recently been shown to be effective in the acute treatment of migraine in phase 3 trials. The aim of this study is to determine whether frequent administration of lasmiditan induces behaviors consistent with MOH in a pre-clinical rat model.

METHODS

Sprague Dawley rats were administered six doses of lasmiditan (10 mg/kg), sumatriptan (10 mg/kg), or sterile water orally over 2 weeks and cutaneous allodynia was evaluated regularly in the periorbital and hindpaw regions using von Frey filaments. Testing continued until mechanosensitivity returned to baseline levels. Rats were then submitted to bright light stress (BLS) or nitric oxide (NO) donor administration and were again evaluated for cutaneous allodynia in the periorbital and hindpaw regions hourly for 5 hours.

RESULTS

Both lasmiditan and sumatriptan exhibited comparable levels of drug-induced cutaneous allodynia in both the periorbital and hindpaw regions, which resolved after cessation of drug administration. Both lasmiditan and sumatriptan pre-treatment resulted in cutaneous allodynia that was evoked by either BLS or NO donor.

CONCLUSIONS

In a pre-clinical rat model of MOH, oral lasmiditan, like sumatriptan, induced acute transient cutaneous allodynia in the periorbital and hindpaw regions that after resolution could be re-evoked by putative migraine triggers. These results suggest that lasmiditan has the capacity to induce MOH through persistent latent peripheral and central sensitization mechanisms.

Persistent Post-Traumatic Headache and Migraine: Pre-Clinical Comparisons

Background: Oftentimes, persistent post traumatic headache (PPTH) and migraine are phenotypically similar and the only clinical feature that differentiate them is the presence of a mild or moderate traumatic brain injury (mTBI). The aim of this study is to describe the differences in brain area and in biochemical cascade after concussion and to define the efficacy and safety of treatments in use. Methods: Sources were chosen in according to the International Classification of Headache Disorder (ICHD) criteria. Results: The articles demonstrated a significant difference between PPTH and migraine regarding static functional connectivity (sFC) and dynamic functional connectivity (dFC) in brain structure that could be used for exploring the pathophysiological mechanisms in PPTH. Many studies described a cascade of neuro-metabolic changes that occur after traumatic brain injury. These variations are associated to the mechanism occurring when developing a PPTH. Conclusions: The state of art of this important topic show how although the mechanisms underlying the development of the two different diseases are different, the treatment of common migraine is efficacious in patients that have developed a post traumatic form.

Efficacy, Tolerability, and Safety of DFN-15 (Celecoxib Oral Solution, 25 mg/mL) in the Acute Treatment of Episodic Migraine: A Randomized, Double-Blind, Placebo-Controlled Study

OBJECTIVE

The objective of this study was to evaluate the efficacy, tolerability, and safety of 120 mg DFN-15 vs placebo for the acute treatment of migraine.

BACKGROUND

Certain nonsteroidal anti-inflammatory drugs (NSAIDs) are guideline-recommended therapies for the acute treatment of migraine, but patients who use them may have issues with gastrointestinal tolerability. Celecoxib, a selective inhibitor of cyclooxygenase-2, produces analgesia similar to nonselective NSAIDs. DFN-15 is an oral, ready-made liquid solution of celecoxib being investigated for the acute treatment of migraine.

METHODS

A randomized, double-blind, placebo-controlled, efficacy, tolerability, and safety study in adults with migraine was conducted. Subjects treated a single migraine attack with 120 mg DFN-15 or placebo as soon as possible after the onset of pain of moderate to severe intensity. The 2 independent coprimary efficacy endpoints were the proportion of subjects with freedom from pain and the absence of the most bothersome symptom (MBS) at 2 hours postdose. A second double-blind treatment period followed the first, but did not contribute to the primary outcomes and will be reported elsewhere.

RESULTS

There were 622 subjects randomized (1:1) to double-blind treatment with either 120 mg DFN-15 or placebo, and 567 (91.2%) treated a migraine with study drug (n = 285 DFN-15; n = 282 placebo). Groups were balanced in demographic characteristics; the mean age was 40, and most subjects were female (87% [494/567]). At 2 hours postdose, DFN-15 was significantly superior to placebo for pain freedom (35.6% [98/275] vs 21.7% [57/263], P < .001), with an odds ratio (95% CI) of 2.00 (1.36, 2.94) and for freedom from the MBS (57.8% [134/232] vs 44.8% [104/232], P = .007), with an odds ratio (95% CI) of 1.68 (1.17, 2.43). A total of 13.3% (38/285) of DFN-15-treated subjects and 8.9% (25/282) of placebo-treated subjects reported a treatment-emergent adverse event (TEAE). Study drug-related TEAEs were reported by 9.1% (26/285) of DFN-15 subjects and 6.0% (17/282) of placebo subjects, the most common of which were dysgeusia (4.2% [12/285] vs 1.4% [4/282]) and nausea (3.2% [9/285] vs 1.8% [5/282]). No subjects treated with DFN-15 reported TEAEs that were severe or led to withdrawal, and no serious TEAEs or deaths were reported in the study.

CONCLUSIONS

DFN-15 was significantly more effective than placebo for the acute treatment of migraine, with a generally favorable tolerability and safety profile.

Mechanisms of migraine as a chronic evolutive condition

Understanding the mechanisms of migraine remains challenging as migraine is not a static disorder, and even in its episodic form migraine remains an "evolutive" chronic condition. Considerable progress has been made in elucidating the pathophysiological mechanisms of migraine, associated genetic factors that may influence susceptibility to the disease, and functional and anatomical changes during the progression of a migraine attack or the transformation of episodic to chronic migraine. Migraine is a life span neurological disorder that follows an evolutive age-dependent change in its prevalence and even clinical presentations. As a disorder, migraine involves recurrent intense head pain and associated unpleasant symptoms. Migraine attacks evolve over different phases with specific neural mechanisms and symptoms being involved during each phase. In some patients, migraine can be transformed into a chronic form with daily or almost daily headaches. The mechanisms behind this evolutive process remain unknown, but genetic and epigenetic factors, inflammatory processes and central sensitization may play an important role.

Altered activity in the nucleus raphe magnus underlies cortical hyperexcitability and facilitates trigeminal nociception in a rat model of medication overuse headache

BACKGROUND

The pathogenesis of medication overuse headache (MOH) involves hyperexcitability of cortical and trigeminal neurons. Derangement of the brainstem modulating system, especially raphe nuclei may contribute to this hyperexcitability. The present study aimed to investigate the involvement of the nucleus raphe magnus (NRM) in the development of cortical and trigeminal hyperexcitability in a rat model of MOH.

RESULTS

Chronic treatment with acetaminophen increased the frequency of cortical spreading depression (CSD) and the number of c-Fos-immunoreactive (Fos-IR) neurons in the trigeminal nucleus caudalis (TNC). In the control group, muscimol microinjected into the NRM increased significantly the frequency of CSD-evoked direct current shift and Fos-IR neurons in the TNC. This facilitating effect was not found in rats with chronic acetaminophen exposure. In a model of migraine induced by intravenous systemic infusion of nitroglycerin (NTG), rats with chronic exposure to acetaminophen exhibited significantly more frequent neuronal firing in the TNC and greater Fos-IR than those without the acetaminophen treatment. Muscimol microinjection increased neuronal firing in the TNC in control rats, but not in acetaminophen-treated rats. The number of Fos-IR cells in TNC was not changed significantly.

CONCLUSION

Chronic exposure to acetaminophen alters the function of the NRM contributing to cortical hyperexcitability and facilitating trigeminal nociception.

Maladaptive activation of Nav1.9 channels by nitric oxide causes triptan-induced medication overuse headache

Medication-overuse headaches (MOH) occur with both over-the-counter and pain-relief medicines, including paracetamol, opioids and combination analgesics. The mechanisms that lead to MOH are still uncertain. Here, we show that abnormal activation of Nav1.9 channels by Nitric Oxide (NO) is responsible for MOH induced by triptan migraine medicine. Deletion of the Scn11a gene in MOH mice abrogates NO-mediated symptoms, including cephalic and extracephalic allodynia, photophobia and phonophobia. NO strongly activates Nav1.9 in dural afferent neurons from MOH but not normal mice. Abnormal activation of Nav1.9 triggers CGRP secretion, causing artery dilatation and degranulation of mast cells. In turn, released mast cell mediators potentiates Nav1.9 in meningeal nociceptors, exacerbating inflammation and pain signal. Analysis of signaling networks indicates that PKA is downregulated in trigeminal neurons from MOH mice, relieving its inhibitory action on NO-Nav1.9 coupling. Thus, anomalous activation of Nav1.9 channels by NO, as a result of chronic medication, promotes MOH.

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.

TRPA1/NOX in the soma of trigeminal ganglion neurons mediates migraine-related pain of glyceryl trinitrate in mice

Glyceryl trinitrate is administered as a provocative test for migraine pain. Glyceryl trinitrate causes prolonged mechanical allodynia in rodents, which temporally correlates with delayed glyceryl trinitrate-evoked migraine attacks in patients. However, the underlying mechanism of the allodynia evoked by glyceryl trinitrate is unknown. The proalgesic transient receptor potential ankyrin 1 (TRPA1) channel, expressed by trigeminal nociceptors, is sensitive to oxidative stress and is targeted by nitric oxide or its by-products. Herein, we explored the role of TRPA1 in glyceryl trinitrate-evoked allodynia. Systemic administration of glyceryl trinitrate elicited in the mouse periorbital area an early and transient vasodilatation and a delayed and prolonged mechanical allodynia. The systemic, intrathecal or local administration of selective enzyme inhibitors revealed that nitric oxide, liberated from the parent drug by aldehyde dehydrogenase 2 (ALDH2), initiates but does not maintain allodynia. The central and the final phases of allodynia were respectively associated with generation of reactive oxygen and carbonyl species within the trigeminal ganglion. Allodynia was absent in TRPA1-deficient mice and was reversed by TRPA1 antagonists. Knockdown of neuronal TRPA1 by intrathecally administered antisense oligonucleotide and selective deletion of TRPA1 from sensory neurons in Advillin-Cre; Trpa1^fl/fl mice revealed that nitric oxide-dependent oxidative and carbonylic stress generation is due to TRPA1 stimulation, and resultant NADPH oxidase 1 (NOX1) and NOX2 activation in the soma of trigeminal ganglion neurons. Early periorbital vasodilatation evoked by glyceryl trinitrate was attenuated by ALDH2 inhibition but was unaffected by TRPA1 blockade. Antagonists of the calcitonin gene-related peptide receptor did not affect the vasodilatation but partially inhibited allodynia. Thus, although both periorbital allodynia and vasodilatation evoked by glyceryl trinitrate are initiated by nitric oxide, they are temporally and mechanistically distinct. While vasodilatation is due to a direct nitric oxide action in the vascular smooth muscle, allodynia is a neuronal phenomenon mediated by TRPA1 activation and ensuing oxidative stress. The autocrine pathway, sustained by TRPA1 and NOX1/2 within neuronal cell bodies of trigeminal ganglia, may sensitize meningeal nociceptors and second order trigeminal neurons to elicit periorbital allodynia, and could be of relevance for migraine-like headaches evoked by glyceryl trinitrate in humans.

Impact of Medical Care on Symptomatic Drug Consumption and Quality of Life in Headache: A One-Year Population Study

Background: Chronic headache is one of the most common pain conditions, often leading to symptomatic drug overuse. The aim of this study was to provide data on symptomatic drug consumption in an Italian outpatient population and to describe how the clinical picture of headache may change after headache experts take charge of the care of affected individuals.

Methods: A total of 199 adults complaining of chronic headache were recruited through 32 pharmacies in the Pavia health district. Participants underwent four evaluations: a baseline assessment (T0) and three follow-up evaluations performed by a neurologist at 3, 6, and 12 months (T3, T6, and T12, respectively). On each occasion, they underwent a complete neurological assessment and received therapeutic adjustments to achieve better management of their headache.

Results: On the basis of a preliminary telephone interview, the prevalence rates of chronic headache and medication overuse headache (MOH) were 16 and 12%, respectively. At 12 months of follow-up, we observed a significant decrease in the frequency of attacks (T0: 9 ± 9/month vs. T12: 2 ± 2/month; p < 0.001), in the number of days/month with headache (T0: 11 ± 9 vs. T12: 4 ± 4; p < 0.001) and in single attack duration (T0: 34 ± 30 h vs. T12: 10 ± 19 h; p < 0.001). Careful headache management resulted in a significant decrease in analgesic consumption (T0: 12 ± 16 vs. T12: 4 ± 6 doses/month; p = 0.014) and a significant increase in quality of life, measured using the Migraine Disability Assessment Scale (MIDAS) and Headache Under-Response to Treatment (HURT) scales (p < 0.001).

Conclusions: Headache management by a specialist is more effective than self-treatment, resulting in an overall benefit for headache patients.

Migraine: Experimental Models and Novel Therapeutic Approaches

Migraine is a disorder affecting an increasing number of subjects. Currently, this disorder is not entirely understood, and limited therapeutic solutions are available. Migraine manifests as a debilitating headache associated with an altered sensory perception that may compromise the quality of life. Animal models have been developed using chemical, physical or genetic modifications, to evoke migraine-like hallmarks for the identification of novel molecules for the treatment of migraine. In this context, experimental models based on the use of chemicals as nitroglycerin or inflammatory soup were extensively used to mimic the acute state and the chronicity of the disorder. This manuscript is aimed to provide an overview of murine models used to investigate migraine pathophysiology. Pharmacological targets as 5-HT and calcitonin gene-related peptide (CGRP) receptors were evaluated for their relevance in the development of migraine therapeutics. Drug delivery systems using nanoparticles may be helpful for the enhancement of the brain targeting and bioavailability of anti-migraine drugs as triptans. In conclusion, the progresses in migraine management have been reached with the development of emerging agonists of 5-HT receptors and novel antagonists of CGRP receptors. The nanoformulations may represent a future perspective in which already known anti-migraine drugs showed to better exert their therapeutic effects.

The need for new acutely acting antimigraine drugs: moving safely outside acute medication overuse

Background

The treatment of migraine is impeded by several difficulties, among which insufficient headache relief, side effects, and risk for developing medication overuse headache (MOH). Thus, new acutely acting antimigraine drugs are currently being developed, among which the small molecule CGRP receptor antagonists, gepants, and the 5-HT_1F receptor agonist lasmiditan. Whether treatment with these drugs carries the same risk for developing MOH is currently unknown.

Main body

Pathophysiological studies on MOH in animal models have suggested that decreased 5-hydroxytryptamine (5-HT, serotonin) levels, increased calcitonin-gene related peptide (CGRP) expression and changes in 5-HT receptor expression (lower 5-HT_1B/D and higher 5-HT_2A expression) may be involved in MOH. The decreased 5-HT may increase cortical spreading depression frequency and induce central sensitization in the cerebral cortex and caudal nucleus of the trigeminal tract. Additionally, low concentrations of 5-HT, a feature often observed in MOH patients, could increase CGRP expression. This provides a possible link between the pathways of 5-HT and CGRP, targets of lasmiditan and gepants, respectively. Since lasmiditan is a 5-HT_1F receptor agonist and gepants are CGRP receptor antagonists, they could have different risks for developing MOH because of the different (over) compensation mechanisms following prolonged agonist versus antagonist treatment.

Conclusion

The acute treatment of migraine will certainly improve with the advent of two novel classes of drugs, i.e., the 5-HT_1F receptor agonists (lasmiditan) and the small molecule CGRP receptor antagonists (gepants). Data on the effects of 5-HT_1F receptor agonism in relation to MOH, as well as the effects of chronic CGRP receptor blockade, are awaited with interest.

Development and Characterization of An Injury-free Model of Functional Pain in Rats by Exposure to Red Light

We report the development and characterization of a novel, injury-free rat model in which nociceptive sensitization after red light is observed in multiple body areas reminiscent of widespread pain in functional pain syndromes. Rats were exposed to red light-emitting diodes (RLED) (LEDs, 660 nm) at an intensity of 50 Lux for 8 hours daily for 5 days resulting in time- and dose-dependent thermal hyperalgesia and mechanical allodynia in both male and female rats. Females showed an earlier onset of mechanical allodynia than males. The pronociceptive effects of RLED were mediated through the visual system. RLED-induced thermal hyperalgesia and mechanical allodynia were reversed with medications commonly used for widespread pain, including gabapentin, tricyclic antidepressants, serotonin/norepinephrine reuptake inhibitors, and nonsteroidal anti-inflammatory drugs. Acetaminophen failed to reverse the RLED induced hypersensitivity. The hyperalgesic effects of RLED were blocked when bicuculline, a gamma-aminobutyric acid-A receptor antagonist, was administered into the rostral ventromedial medulla, suggesting a role for increased descending facilitation in the pain pathway. Key experiments were subjected to a replication study with randomization, investigator blinding, inclusion of all data, and high levels of statistical rigor. RLED-induced thermal hyperalgesia and mechanical allodynia without injury offers a novel injury-free rodent model useful for the study of functional pain syndromes with widespread pain. RLED exposure also emphasizes the different biological effects of different colors of light exposure. PERSPECTIVE: This study demonstrates the effect of light exposure on nociceptive thresholds. These biological effects of red LED add evidence to the emerging understanding of the biological effects of light of different colors in animals and humans. Understanding the underlying biology of red light-induced widespread pain may offer insights into functional pain states.

CGRP and the Trigeminal System in Migraine

OBJECTIVE

The goal of this narrative review is to provide an overview of migraine pathophysiology, with an emphasis on the role of calcitonin gene-related peptide (CGRP) within the context of the trigeminovascular system.

BACKGROUND

Migraine is a prevalent and disabling neurological disease that is characterized in part by intense, throbbing, and unilateral headaches. Despite recent advances in understanding its pathophysiology, migraine still represents an unmet medical need, as it is often underrecognized and undertreated. Although CGRP has been known to play a pivotal role in migraine for the last 2 decades, this has now received more interest spurred by the early clinical successes of drugs that block CGRP signaling in the trigeminovascular system.

DESIGN

This narrative review presents an update on the role of CGRP within the trigeminovascular system. PubMed searches were used to find recent (ie, 2016 to November 2018) published articles presenting new study results. Review articles are also included not as primary references but to bring these to the attention of the reader. Original research is referenced in describing the core of the narrative, and review articles are used to support ancillary points.

RESULTS

The trigeminal ganglion neurons provide the connection between the periphery, stemming from the interface between the primary afferent fibers of the trigeminal ganglion and the meningeal vasculature and the central terminals in the trigeminal nucleus caudalis. The neuropeptide CGRP is abundant in trigeminal ganglion neurons, and is released from the peripheral nerve and central nerve terminals as well as being secreted within the trigeminal ganglion. Release of CGRP from the peripheral terminals initiates a cascade of events that include increased synthesis of nitric oxide and sensitization of the trigeminal nerves. Secreted CGRP in the trigeminal ganglion interacts with adjacent neurons and satellite glial cells to perpetuate peripheral sensitization, and can drive central sensitization of the second-order neurons. A shift in central sensitization from activity-dependent to activity-independent central sensitization may indicate a mechanism driving the progression of episodic migraine to chronic migraine. The pathophysiology of cluster headache is much more obscure than that of migraine, but emerging evidence suggests that it may also involve hypersensitivity of the trigeminovascular system. Ongoing clinical studies with therapies targeted at CGRP will provide additional, valuable insights into the pathophysiology of this disorder.

CONCLUSIONS

CGRP plays an essential role in the pathophysiology of migraine. Treatments that interfere with the functioning of CGRP in the peripheral trigeminal system are effective against migraine. Blocking sensitization of the trigeminal nerve by attenuating CGRP activity in the periphery may be sufficient to block a migraine attack. Additionally, the potential exists that this therapeutic strategy may also alleviate cluster headache as well.