Effectiveness of intravenous dexamethasone, metoclopramide, ketorolac, and chlorpromazine for pain relief and prevention of recurrence in the migraine headache: a prospective double-blind randomized clinical trial

The effectiveness of parenteral agents to mitigate relapses after severe acute migraine headache presentations: A systematic review and network analysis

OBJECTIVES

To compare the effectiveness of parenteral agents to reduce relapse in patients with acute migraine and identify factors that predict relapse.

BACKGROUND

Following discharge from emergency settings, many patients with acute migraine will experience a relapse in pain; severe relapses may result in re-visits to emergency settings.

METHODS

A comprehensive literature search, updated to 2023, was conducted to identify randomized controlled trials assessing the effectiveness of parenteral agents on relapse outcomes in patients with acute migraine discharged from emergency settings. Two independent reviewers completed study selection, quality assessment, and data extraction. A traditional meta-analysis compared parenteral corticosteroids to placebo; a frequentist network analysis assessed direct and indirect comparisons. Results are reported as risk ratios (RRs) and 95% confidence intervals (CIs). The review protocol was registered with the International Prospective Register of Systematic Reviews (identifier: CRD42018099493).

RESULTS

From 8949 citations, a total of 53 unique studies were included involving 6167 patients. Most studies had a high or unclear risk of bias. Corticosteroids significantly reduced relapses compared to placebo (RR 0.67, 95% CI 0.52-0.88; I2 = 0%). Patients receiving lidocaine (RR 0.10, 95% CI 0.01-0.82), sedatives/hypnotics (RR 0.33, 95% CI 0.14-0.75), ergot agents (RR 0.44, 95% CI 0.25-0.75), neuroleptics (RR 0.47, 95% CI 0.31-0.71), opioids (RR 0.58; 95% CI 0.35-0.94), or corticosteroids (RR 0.64, 95% CI 0.47-0.86) were significantly less likely to relapse. Lidocaine (RR 0.09, 95% CI 0.01-0.71), combination therapy (RR 0.12, 95% CI 0.02-0.74), or adding corticosteroids (RR 0.61, 95% CI 0.44-0.84) were more likely to reduce severe relapses. Longer duration of headache and residual pain at discharge were significantly associated with higher relapses.

DISCUSSION

Corticosteroids remain the recommended first-line option to reduce relapse outcomes. Some parenteral agents typically provided for pain relief including ergot agents, neuroleptics, or combination therapy may effectively reduce relapse; however, opioids are not recommended due to safety concerns. Additional research is needed for some lesser studied, albeit promising, agents including lidocaine and propofol. Effective pain control in emergency settings prior to discharge and duration of headache may play a role in the success of such treatments and further investigations could provide further insight regarding how and why some parenteral agents are effective in mitigating relapse events.

The effectiveness of parenteral agents for pain reduction in patients with migraine presenting to emergency settings: A systematic review and network analysis

OBJECTIVES

To assess the comparative effectiveness and safety of parenteral agents for pain reduction in patients with acute migraine.

BACKGROUND

Parenteral agents have been shown to be effective in treating acute migraine pain; however, the comparative effectiveness of different approaches is unclear.

METHODS

Nine electronic databases and gray literature sources were searched to identify randomized clinical trials assessing parenteral agents to treat acute migraine pain in emergency settings. Two independent reviewers completed study screening, data extraction, and Cochrane risk-of-bias assessment, with differences being resolved by adjudication. The protocol of the review was registered with the International Prospective Register of Systematic Reviews (PROSPERO; CRD42018100096).

RESULTS

A total of 97 unique studies were included, with most studies reporting a high or unclear risk of bias. Monotherapy, as well as combination therapy, successfully reduced pain scores prior to discharge. They also increased the proportion of patients reporting pain relief and being pain free. Across the pain outcomes assessed, combination therapy was one of the higher ranked approaches and provided robust improvements in pain outcomes, including lowering pain scores (mean difference -3.36, 95% confidence interval [CI] -4.64 to -2.08) and increasing the proportion of patients reporting pain relief (risk ratio [RR] 2.83, 95% CI 1.74-4.61). Neuroleptics and metoclopramide also ranked high in terms of the proportion of patients reporting pain relief (neuroleptics RR 2.76, 95% CI 2.12-3.60; metoclopramide RR 2.58, 95% CI 1.90-3.49) and being pain free before emergency department discharge (neuroleptics RR 4.8, 95% CI 3.61-6.49; metoclopramide RR 4.1, 95% CI 3.02-5.44). Most parenteral agents were associated with increased adverse events, particularly combination therapy and neuroleptics.

CONCLUSIONS

Various parenteral agents were found to provide effective pain relief. Considering the consistent improvements across various outcomes, combination therapy, as well as monotherapy of either metoclopramide or neuroleptics are recommended as first-line options for managing acute migraine pain. There are risks of adverse events, especially akathisia, following treatment with these agents. We recommend that a shared decision-making model be considered to effectively identify the best treatment option based on the patient's needs.

Drug-related side effects and adverse reactions in the treatment of migraine: a bibliometric and visual analysis

BACKGROUND

Migraine imposes a substantial global burden, impacting patients and society. Pharmacotherapy, as a primary treatment, entails specific adverse reactions. Emphasizing these reactions is pivotal for improving treatment strategies and enhancing patients' well-being. Thus, we conducted a comprehensive bibliometric and visual analysis of relevant literature.

METHODOLOGY

We conducted a comprehensive search on the Science Citation Index Expanded within the Web of Science, restricting the literature for analysis based on criteria such as document type, publication date, and language. Subsequently, we utilized various analytical tools, including VOSviewer, Scimago Graphica, the R package 'bibliometrix', CiteSpace, and Excel programs, for a meticulous examination and systematic organization of data concerning journals, authors, countries/regions, institutions, keywords, and references.

RESULTS

By August 31, 2023, the literature was distributed across 379 journals worldwide, authored by 4,235 individuals from 1726 institutions. It featured 2,363 keywords and 38,412 references. 'HEADACHE' led in publication count, with 'SILBERSTEIN S' as the most prolific author. The United States ranked highest in publication volume, with 'UNIV COPENHAGEN' leading among institutions.

CONCLUSION

Our research findings indicate that researchers in the field continue to maintain a focus on the calcitonin gene-related peptide (CGRP) system and explore diverse mechanisms for drug development through the application of novel biotechnological approaches. Furthermore, it is imperative to enhance the assessment of clinical trial outcomes, consistently monitor the efficacy and safety of prominent drugs such as Erenumab and Fremanezumab. There is a need for further evaluation of acute and preventive treatments tailored to different populations and varying types of migraine.

Drug-related side effects and adverse reactions in the treatment of migraine: a bibliometric and visual analysis

BACKGROUND

Migraine imposes a substantial global burden, impacting patients and society. Pharmacotherapy, as a primary treatment, entails specific adverse reactions. Emphasizing these reactions is pivotal for improving treatment strategies and enhancing patients' well-being. Thus, we conducted a comprehensive bibliometric and visual analysis of relevant literature.

METHODOLOGY

We conducted a comprehensive search on the Science Citation Index Expanded within the Web of Science, restricting the literature for analysis based on criteria such as document type, publication date, and language. Subsequently, we utilized various analytical tools, including VOSviewer, Scimago Graphica, the R package 'bibliometrix', CiteSpace, and Excel programs, for a meticulous examination and systematic organization of data concerning journals, authors, countries/regions, institutions, keywords, and references.

RESULTS

By August 31, 2023, the literature was distributed across 379 journals worldwide, authored by 4,235 individuals from 1726 institutions. It featured 2,363 keywords and 38,412 references. 'HEADACHE' led in publication count, with 'SILBERSTEIN S' as the most prolific author. The United States ranked highest in publication volume, with 'UNIV COPENHAGEN' leading among institutions.

CONCLUSION

Our research findings indicate that researchers in the field continue to maintain a focus on the calcitonin gene-related peptide (CGRP) system and explore diverse mechanisms for drug development through the application of novel biotechnological approaches. Furthermore, it is imperative to enhance the assessment of clinical trial outcomes, consistently monitor the efficacy and safety of prominent drugs such as Erenumab and Fremanezumab. There is a need for further evaluation of acute and preventive treatments tailored to different populations and varying types of migraine.

Randomized Trial Comparing Low- vs High-Dose IV Dexamethasone for Patients With Moderate to Severe Migraine

BACKGROUND AND OBJECTIVES

Dexamethasone decreases the frequency of migraine recurrence after emergency department (ED) discharge. However, the optimal dose of dexamethasone is unknown. We hypothesized that dexamethasone 16 mg IV would allow greater rates of sustained headache relief than 4 mg when coadministered with metoclopramide 10 mg IV.

METHODS

This was a randomized double-blind study. Adults who presented with a headache meeting International Classification of Headache Disorders, 3rd edition, migraine criteria were eligible if they rated the headache as moderate or severe in intensity. Pain intensity was assessed for up to 2 hours in the ED and through telephone 48 hours and 7 days later. The primary outcome was sustained headache relief. Secondary outcomes included headache relief within 2 hours and the number of headache days during the subsequent week. Relying on a priori criteria, the data safety monitoring committee recommended halting the study early for futility.

RESULTS

A total of 1,823 patients were screened, and 209 patients were randomized. The mean age was 38 years (SD 11). One hundred seventy-nine of 209 (86%) identified as women. One hundred fifty-one of 209 (72%) of the population reported severe intensity; the rest reported moderate. Thirty-five of 102 (34%) participants in the metoclopramide +4 mg arm achieved sustained headache relief as did 42/102 (41%) participants in the metoclopramide +16 mg arm (absolute difference 7%, 95% CI -6% to 20%). Headache relief within 2 hours occurred in 77/104 (74%) low-dose and 82/105 (78%) high-dose participants (absolute difference 4%, 95% CI -8% to 16%). During the week after ED discharge, low-dose participants reported a median of 2 headache days (25th, 75th percentile 1, 5); in the high-dose arm, this was also 2 (25th, 75th percentile 0, 4) (mean difference 0.4, 95% CI -0.3 to 1.2).

DISCUSSION

When added to 10 mg IV metoclopramide, doses of dexamethasone greater than 4 mg are unlikely to benefit patients in the ED with migraine.

TRIAL REGISTRATION INFORMATION

This study was registered at ClinicalTrials.gov on October 2, 2019 (NCT04112823). The first patient was enrolled on December 22, 2019.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that 16 mg of IV dexamethasone is unlikely to provide greater rates of sustained headache relief than 4 mg of IV dexamethasone among patients in the ED with migraine treated concurrently with IV metoclopramide.

The efficacy and safety of metoclopramide in relieving acute migraine attacks compared with other anti-migraine drugs: a systematic review and network meta-analysis of randomized controlled trials

BACKGROUND

Many drugs are prescribed in relieving acute migraine attacks, we aim to compare metoclopramide with other antimigraine drugs.

METHODS

We searched online databases like PubMed, Cochrane Library, Scopus, and Web of Science till June 2022 for RCTs that compared metoclopramide alone with placebo or active drugs. The main outcomes were the mean change in headache score and complete headache relief. The secondary outcomes were the rescue medications need, side effects, nausea and recurrence rate. We qualitatively reviewed the outcomes. Then, we performed the network meta-analyses (NMAs) when it was possible. which were done by the Frequentist method using the MetaInsight online software.

RESULTS

Sixteen studies were included with a total of 1934 patients: 826 received metoclopramide, 302 received placebo, and 806 received other active drugs. Metoclopramide was effective in reducing headache outcomes even for 24 h. The intravenous route was the most chosen route in the included studies and showed significant positive results regarding headache outcomes; however, the best route whether intramuscular, intravenous, or suppository was not compared in the previous studies. Also, both 10 and 20 mg doses of metoclopramide were effective in improving headache outcomes; however, there was no direct comparison between both doses and the 10 mg dose was the most frequently used dosage. In NMA of headache change after 30 min or 1 h, metoclopramide effect came after granisetron, ketorolac, chlorpromazine, and Dexketoprofen trometamol. Only granisetron's effect was significantly higher than metoclopramide's effect which was only significantly higher than placebo and sumatriptan. In headache-free symptoms, only prochlorperazine was non-significantly higher than metoclopramide which was higher than other medications and showed significantly higher effects only with placebo. In rescue medication, metoclopramide's effect was only non-significantly lower than prochlorperazine and chlorpromazine while its effect was higher than other drugs and showed higher significant effects only than placebo and valproate. In the recurrence rate, studies showed no significant difference between metoclopramide and other drugs. Metoclopramide significantly decreased nausea more than the placebo. Regarding side effects, metoclopramide showed a lower incidence of mild side effects than pethidine and chlorpromazine and showed a higher incidence of mild side effects than placebo, dexamethasone, and ketorolac. The reported extrapyramidal symptoms with metoclopramide were dystonia or akathisia.

CONCLUSION

A dose of 10 mg IV Metoclopramide was effective in relieving migraine attacks with minimal side effects. Compared to other active drugs, it only showed a lower significant effect compared with granisetron regarding headache change while it showed significantly higher effects only with placebo in both rescue medication needs and headache-free symptoms and valproate in only rescue medication need. Also, it significantly decreased headache scores more than placebo and sumatriptan. However, more studies are needed to support our results.

Non-opioid Intravenous Drugs for Pain Management in Patients Presenting with Acute Migraine Pain in the Emergency Department: A Comprehensive Literature Review

Context

Migraine is one of the most common causes of disability worldwide and the sixth cause of loss of life years due to disability. Migraine is reported mainly in young and middle-aged people, so it can cause a person to face many problems in doing daily tasks. The emergency department annually accepts 1.2 million patients with migraine. Therefore, timely diagnosis of the disease, knowledge of valuable drugs in an emergency, knowing how to use them, and finally, early treatment can play an essential and decisive role in improving patients' symptoms and reducing the disability caused by the disease. An essential and valuable drug category in the emergency department to manage pain is non-opioid intravenous (IV) drugs. Therefore, this study aimed to evaluate non-opioid IV drugs to manage pain in patients with acute migraines in the emergency department.

Method

This study conducted a comprehensive literature review to access the latest scientific studies and documents using keywords (acute migraine, non-opioid IV drugs, pain management) in reliable databases such as PubMed, Scopus, Web of Science, Cochrane, and Google Scholar. We reviewed 87 articles, 53 of which were evaluated and compared.

Results

A review study considers intravenous acetaminophen as a suitable option for the first-line treatment of acute migraine in the emergency department if the patient does not tolerate aspirin and non-steroidal anti-inflammatory drugs (NSAIDs). Various studies have obtained positive effects of NSAIDs and dihydroergotamine (DHE) in treating acute migraine. Prescribing anti-dopaminergic drugs can effectively reduce associated symptoms such as nausea and vomiting. Dexamethasone and magnesium sulfate are effective in preventing migraine and severe attacks. Intravenous sodium valproate is effective in moderate to severe migraine attacks or treatment-resistant migraines. In the emergency department, prescribing intravenous haloperidol, lidocaine, and propofol can help manage migraine and improve other associated symptoms, such as nausea or vomiting.

Conclusions

Non-opioid IV drugs are essential to manage pain and improve other migraine symptoms in the emergency setting. Knowing the above drugs and their optimal use has a decisive role in managing patients with acute migraine in the emergency department.

Efficacy of ketorolac in the treatment of acute migraine attack: A systematic review and meta-analysis

OBJECTIVES

This review was designated to evaluate the efficacy of parenteral ketorolac in treating acute migraine headache.

METHODS

We searched databases Cochrane Central Register of Controlled Trials (CENTRAL), Medline, and Google Scholar up to January 2021 and identified randomized controlled trials comparing ketorolac to any other medications in treating patients presenting with migraine headache.

RESULTS

Thirteen trials were included in our review, comprising 944 participants. We derived seven comparisons: ketorolac versus phenothiazines, metoclopramide, sumatriptan, dexamethasone, sodium valproate, caffeine, and diclofenac. There were no significant differences in the reduction of pain intensity at 1 h under the comparisons between ketorolac and phenothiazines (standard mean difference [SMD] = 0.09, p = 0.74) or metoclopramide (SMD = 0.02, p = 0.95). We also found no difference in the outcome recurrence of headache (ketorolac vs. phenothiazines (risk ratio [RR] =0.98, p = 0.97)], ability to return to work or usual activity (ketorolac vs. metoclopramide [RR = 0.64, p = 0.13]), need for rescue medication (ketorolac vs. phenothiazines [RR = 1.72, p = 0.27], ketorolac vs. metoclopramide [RR 2.20, p = 0.18]), and frequency of adverse effects (ketorolac vs. metoclopramide [RR = 1.07, p = 0.82]). Limited trials suggested that ketorolac offered better pain relief at 1 h compared to sumatriptan and dexamethasone; had lesser frequency of adverse effects than phenothiazines; and was superior to sodium valproate in terms of reduction of pain intensity at 1 h, need for rescue medication, and sustained headache freedom within 24 h.

CONCLUSIONS

Ketorolac may have similar efficacy to phenothiazines and metoclopramide in treating acute migraine headache. Ketorolac may also offer better pain control than sumatriptan, dexamethasone, and sodium valproate. However, given the lack of evidence due to inadequate number of trials available, future studies are warranted.

Pain reduction and adverse effects of intravenous metoclopramide for acute migraine attack: A systematic review and meta-analysis of randomized-controlled trials

BACKGROUND

Metoclopramide may be used to treat people suffering from acute migraine. However, no comprehensive investigation on this issue has been recorded. This review will provide more solid evidence for the use of metoclopramide in treating acute migraine.

AIM

To compare the efficacy of intravenous metoclopramide with other therapies in migraine attack treatment in an emergency department (ED).

METHODS

We included randomized controlled trials of participants older than 18 years with acute migraine headaches, which included at least one arm that received intravenous (IV) metoclopramide at the ED. A literature search of PubMed, Web of Science, Cochrane Collaboration, and Reference Citation Analysis on December 31, 2021 retrieved other drugs or placebo-controlled studies without language limitation. The risk of bias was assessed using the Cochrane risk of bias tool. The primary endpoint was pain reduction at 60 min or closest to 1 h after treatment, as measured by the pain scale. Secondary endpoints included adverse effects or reactions resulting from metoclopramide or comparisons.

RESULTS

Fourteen trials with a total of 1661 individuals were eligible for review. The risk of bias ranged from low to intermediate. IV metoclopramide administration was not associated with higher pain reduction at 1 h (Standard mean difference [SMD] = -0.03, 95% confidence interval [CI]: -0.33-0.28, P = 0.87). However, metoclopramide was associated with better pain reduction than placebo (SMD = 1.04, 95%CI: 0.50-1.58, P = 0.0002). In addition, side effects were not significantly different between IV metoclopramide and other drugs or placebo (odds ratio [OR] = 0.76, 95%CI: 0.48-1.19, P = 0.09 and OR = 0.92, 95%CI: 0.31-2.74, P = 0.54, respectively).

CONCLUSION

Metoclopramide is more effective than placebo in treating migraine in the ED. Despite the observed tendency of decreased side effects, its effectiveness compared to other regimens is poorly understood. More research on this area is needed to treat migraine in acute care settings effectively.

Parenteral NSAIDs for acute treatment of migraine: Adherence to the IHS guidelines for controlled trials

Background:

Parenteral non-steroidal anti-inflammatory drugs (NSAIDs) are important alternatives to oral NSAIDs, especially in patients with severe migraine who have emesis or gastroparesis. With increasing research on using parenteral NSAIDs for acute migraine, it is critical to examine the quality of these studies. Our goal was to assess the adherence of these trials to the International Headache Society (IHS) controlled trial guidelines for acute treatment of migraine.

Methods:

We queried PubMed for clinical trials investigating parenteral NSAIDs for acute treatment of migraine in adult patients. We developed a 14-point scoring system based on the essential components of the IHS guidelines. To date, four versions of the IHS’s Guidelines for controlled trials of acute treatment of migraine attacks have been published. Each trial was evaluated with the appropriate edition of the guidelines.

Results:

We identified 216 studies and assessed 27 eligible clinical trials. The mean score was 6.7 ± 2.1 (2–11). Most trials followed the IHS migraine diagnosis criteria (85.2%), but only six (22.2%) selected patients based on the recommended headache frequency. Most trials were randomized (88.8%), but fewer were double-blinded (74.1%) or placebo-controlled (11.1%). Almost every trial clearly explained the pain scale (96.3%), and three-quarters (77.8%) assessed headache-associated symptoms. However, no trial utilized the recommended primary endpoint: pain-freedom at 2-hours.

Conclusions:

Most clinical trials on parenteral NSAIDs for acute migraine did not fully adhere to the IHS recommendations. Future studies should pay special attention to the IHS guideline to improve the quality of clinical trials for the acute treatment of migraine.

Second-line interventions for migraine in the emergency department: A narrative review

OBJECTIVE

Millions of patients present to US emergency departments (ED) annually for the treatment of migraine. First-line treatments, including metoclopramide, prochlorperazine, and sumatriptan, fail to provide sufficient relief in up to one-third of treated patients. In this narrative review, we discuss the evidence supporting the use of injectable (intravenous, intramuscular, or subcutaneous) medications for patients in the ED who fail to improve sufficiently after treatment with first-line medication.

METHODS

We used the American Headache Society's guideline, "Management of Adults with Acute Migraine in the Emergency Department: The American Headache Society Evidence Assessment of Parenteral Pharmacotherapies," published in 2016, to identify first-line medications for migraine. We then conducted a PubMed search to determine whether any evidence supported the use of these medications as second-line therapy and whether any evidence existed to support the use of injectable therapies not discussed in the guideline as second-line therapy.

RESULTS

We identified only scant high-quality randomized data of second-line therapy. Therefore, we based our recommendations on medications that have reliably demonstrated efficacy as first-line treatment of migraine. These medications include injectable non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen. Dihydroergotamine and valproic acid have some data supporting efficacy. More recently, greater occipital nerve blocks (GONBs) have been shown to be efficacious. With the exception of meperidine, opioids have been shown to be not efficacious. Most data published to date demonstrate no role for propofol and ketamine.

CONCLUSIONS

There are no evidence-based second-line treatments of migraine in the ED setting. For patients with migraine, who fail to improve after treatment with a first-line medication, it is reasonable to use an intravenous NSAID or intravenous acetaminophen. Alternatively, clinicians adept at performing a GONB may offer this treatment.

Pharmacological treatment of migraine: Drug classes, mechanisms of action, clinical trials and new treatments

Migraine is the sixth most prevalent disease globally, a major cause of disability, and it imposes an enormous personal and socioeconomic burden. Migraine treatment is often limited by insufficient therapy response, leading to the need for individually adjusted treatment approaches. In this review, we analyse historical and current pharmaceutical development approaches in acute and chronic migraine based on a comprehensive and systematic analysis of Food and Drug Administration (FDA)-approved drugs and those under investigation. The development of migraine therapeutics has significantly intensified during the last 3 years, as shown by our analysis of the trends of drug development between 1970 and 2020. The spectrum of drug targets has expanded considerably, which has been accompanied by an increase in the number of specialised clinical trials. This review highlights the mechanistic implications of FDA-approved and currently investigated drugs and discusses current and future therapeutic options based on identified drug classes of interest.

The Influence of Metoclopramide on Trigeminovascular Nociception: Possible Anti-migraine Mechanism of Action

Metoclopramide is widely used as an abortive migraine therapy due to the advantage of having not only antiemetic, but also analgesic properties. Despite the proven clinical efficacy of metoclopramide in acute migraine, the mechanism of its anti-cephalalgic action has not been entirely elucidated. Taking into account the key role of the trigeminovascular system activation in migraine pathophysiology, we aimed to investigate metoclopramide effects on the excitability of central trigeminovascular neurons and neurogenic dural vasodilation using valid electrophysiological and neurovascular models of trigeminovascular nociception. Extracellular recordings of the activity of second-order dura-sensitive neurons were made in the trigeminocervical complex (TCC) of 16 anaesthetised rats. Cumulative metoclopramide infusion (three steps in 30 min intervals, 5 mg/kg i.v. per step, n = 8) significantly and dose-dependently suppressed both ongoing firing of the TCC neurons and their responses to dural electrical stimulation, maximally to 30%[0-49%] (median[Q1-Q3]) and 4%[0-30%] of the initial level, respectively (both p = 0.001, compared to saline (n = 8)). By contrast, the neurogenic dural vasodilation studied in a separate group of 12 rats was not significantly affected by cumulative infusion of metoclopramide (5 mg/kg i.v. per step, n = 6) compared to both baseline values and the vehicle group (n = 6) (all p > 0.05). These results provide evidence that metoclopramide is unable to affect the peripheral response to trigeminovascular activation, but it does suppress the central response, which is highly predictive of anti-migraine action. Thus, here we show the neurophysiological mechanism underlying the therapeutic efficacy of metoclopramide in migraine.