Migraine and cardiovascular disease in women and the role of aspirin: subgroup analyses in the Women's Health Study

Pain from Internal Organs and Headache: The Challenge of Comorbidity

Headache and visceral pain are common clinical painful conditions, which often co-exist in the same patients. Numbers relative to their co-occurrence suggest possible common pathophysiological mechanisms. The aim of the present narrative review is to describe the most frequent headache and visceral pain associations and to discuss the possible underlying mechanisms of the associations and their diagnostic and therapeutic implications based on the most recent evidence from the international literature. The conditions addressed are as follows: visceral pain from the cardiovascular, gastrointestinal, and urogenital areas and primary headache conditions such as migraine and tension-type headache. The most frequent comorbidities involve the following: cardiac ischemic pain and migraine (possible shared mechanism of endothelial dysfunction, oxidative stress, and genetic and hormonal factors), functional gastrointestinal disorders, particularly IBS and both migraine and tension-type headache, primary or secondary dysmenorrhea and migraine, and painful bladder syndrome and headache (possible shared mechanisms of peripheral and central sensitization processes). The data also show that the various visceral pain-headache associations are characterized by more than a simple sum of symptoms from each condition but often involve complex interactions with the frequent enhancement of symptoms from both, which is crucial for diagnostic and treatment purposes.

Comorbidities of primary headache disorders: a literature review with meta-analysis

Background

Primary headache disorders are common and burdensome conditions. They are associated to several comorbidities, such as cardiovascular or psychiatric ones, which, in turn, contribute to the global burden of headache. The aim of this study is to provide a comprehensive description of the pooled prevalence of comorbidities of primary headache disorders using a meta-analytical approach based on studies published between 2000 and 2020.

Methods

Scopus was searched for primary research (clinical and population studies) in which medical comorbidities were described in adults with primary headache disorders. Comorbidities were extracted using a taxonomy derived from the Global Burden of Disease (GBD) study. We compared prevalence of comorbidities among headache sufferers against general population using GBD-2019 estimates, and compared comorbidities’ proportions in clinical vs. population studies, and by age and gender.

Results

A total of 139 studies reporting information on 4.19 million subjects with primary headaches were included: in total 2.75 million comorbidities were reported (median per subject 0.64, interquartile range 0.32–1.07). The most frequently addressed comorbidities were: depressive disorders, addressed in 51 studies (pooled proportion 23 %, 95 % CI 20–26 %); hypertension, addressed in 48 studies (pooled proportion 24 %, 95 % CI 22–26 %); anxiety disorders addressed in 40 studies (pooled proportion 25 %, 95 % CI 22–28 %). For conditions such as anxiety, depression and back pain, prevalence among headache sufferers was higher than in GBD-2109 estimates. Associations with average age and female prevalence within studies showed that hypertension was more frequent in studies with higher age and less females, whereas fibromyalgia, restless leg syndrome, and depressive disorders were more frequent in studies with younger age and more female.

Conclusions

Some of the most relevant comorbidities of primary headache disorders – back pain, anxiety and depression, diabetes, ischemic heart disease and stroke – are among the most burdensome conditions, together with headache themselves, according to the GBD study. A joint treatment of headaches and of these comorbidities may positively impact on headache sufferers’ health status and contribute to reduce the impact of a group of highly burdensome diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-021-01281-z.

Pediatric Episodic Migraine with Aura: A Unique Entity?

Migraine headache is a common cause of pain and disability in children and adolescents and is a major contributor to frequently missed school days and limitations in activities. Of children and adolescents with migraine headache, approximately one-third have migraine with aura (MA). MA is often considered to be similar to migraine without aura (MO), and thus, many studies do not stratify patients based on the presence of aura. Because of this, treatment recommendations are often analogous between MA and MO, with a few notable exceptions. The purpose of this review is to highlight the current evidence demonstrating the unique pathophysiology, clinical characteristics, differential diagnosis, co-morbidities, and treatment recommendations and responses for pediatric MA.

The Potential Protective Role of Aspirin Against Migraine in Pregnant Women

Females are highly predisposed to the occurrence of migraine, a recurrent neurovascular headache disorder. Although migraine improves or disappears during pregnancy, a significant association between migraine and hypertension (i.e., pre-eclampsia) or vascular complications (i.e., stroke) during gestation has been determined. Low-dose aspirin exerts an antithrombotic effect and can improve vascular resistance by regulating endothelial function, which are implicated in the pathogenesis of migraine, pre-eclampsia, and other vascular complications during pregnancy. Low-dose aspirin is widely used prophylactically in the general population who are at higher risk of developing stroke or in pregnant women at higher risk of pre-eclampsia. In this paper we discuss the recent trends in research on the relationship between migraine and pre-eclampsia, an issue of paramount importance in obstetric care, and the potential relationship between migraine and vascular complications in pregnant women. In addition, the potential validity of low-dose aspirin prophylaxis in pregnant women with migraine is explored.

Prevalence of ischemic stroke and atrial fibrillation in young patients with migraine national inpatient sample analysis

OBJECTIVE

To estimate the prevalence of ischemic stroke (IS) and atrial fibrillation (AF) in young patients with migraine and to identify the independent predictors of IS in a large cohort of hospitalized patients.

METHODS

A cohort of patients with migraine with aura (MA) and migraine without aura (MO) was identified from the National Inpatient Sample database for the years 2012 to 2015. Ischemic stroke was identified by the International Classification of Diseases-9-CM codes. Binary logistic regression and Chi-square tests were utilized.

RESULTS

A total number of 834,875 young patients (18-44 years) were included in this study with a mean age of 33 years. The prevalence of IS was 1.3% and was significantly higher in patients with MA (3.7% versus 1.2%, P <0.001). The prevalence of AF was 0.9% and it was significantly higher in patients with MA (1.2% versus 0.8%, P <0.001). Migraine with aura was an independent predictor of IS (OR 3.23, 95% CI 3.05-3.42, P <0.001) and AF (OR 1.63, 95% CI 1.42-1.88, P <0.001). Other predictors of IS were hypertension (OR 2.2, 95% CI 2.12-2.3, P <0.001), diabetes mellitus (DM) (OR 1.37, 95% CI 1.31-1.42, P <0.001), peripheral vascular disease (PVD) (OR 12.08, 95% CI 11.23-12.98, P <0.001) and smoking (OR 1.37, 95% CI 1.31-1.42, P <0.001).

CONCLUSION

In this relatively large study, the overall prevalence of IS in young migraine patients was low at 1.3%. The prevalence of IS and AF was significantly higher in patients with MA. Presence of PVD confers a high risk of IS in young patients with migraine. Migraine aura was observed to be an independent predictor of IS and AF in patients with history of migraine. Optimal control of vascular risk factors in migraine patients appears to be indicated despite the overall low risk.

Association of Migraine and Ischemic Heart Disease: A Review

Many new studies have shown an association between migraine and ischemic heart disease, and the association seems to be multi-factorial. This article reviews what is already known about this linkage and further investigates if migraine is a risk factor for cardiovascular disease. The literature search for this article was performed primarily using PubMed as the search engine. Only those articles that assessed migraine as exposure and cardiovascular events as outcomes were included. Also, articles only from the last five years with full-text and human studies were reviewed. Based on our investigation and as indicated by previous studies, migraine headache is associated with different kinds of cardiovascular events. Healthcare providers need to be aware of this association so that they can assess and manage their migraine patients better.

The impact of self-administered acupressure on sleep quality and fatigue among patients with migraine: A randomized controlled trial

BACKGROUND AND AIM

Poor sleep and fatigue are among the most common complaints of patients with migraine. These problems can lead to different negative consequences such as headaches. This study aimed to examine the impacts of self-administered acupressure on sleep quality and fatigue among patients with migraine.

METHODS

This double-blind randomized controlled trial was conducted in 2016 on 76 patients who suffered from migraine without aura. Patients were conveniently selected from the neurology clinic of Valiasr (PBUH) teaching hospital and randomly allocated to either an acupressure (n = 38) or a sham acupressure group (n = 38) group. Data collection instruments were a demographic questionnaire, Pittsburg Sleep Quality Index, and Fatigue Severity Scale. Patients in the acupressure and the sham acupressure groups were trained to apply acupressure on respectively acupoints and sham points thrice weekly at bedtime for four consecutive weeks. The data were analyzed through the Chi-square, the independent-sample t, the paired-sample t, and the ANCOVA tests at the significance level of less than 0.05.

RESULTS

After controlling sleep quality mean scores at baseline, no significant difference was found between the sleep quality of the two groups after intervention (P > 0.05). The mean scores of fatigue significantly decreased in both acupressure and sham acupressure groups (P < 0.05). However, the decrease in the acupressure group was significantly greater than in the sham acupressure group (P < 0.05).

CONCLUSION

As a noninvasive non-pharmacological therapy, acupressure can significantly reduce fatigue among patients with migraine.

Episodic Migraine With and Without Aura: Key Differences and Implications for Pathophysiology, Management, and Assessing Risks

PURPOSE OF REVIEW

To review the pathophysiologic, epidemiologic, and clinical evidence for similarities and differences between migraine with and without aura.

RECENT FINDINGS

The ICHD-3 has recently refined the diagnostic criteria for aura to include positive symptomatology, which better differentiates aura from TIA. Although substantial evidence supports cortical spreading depression as the cause of visual aura, the role (if any) of CSD in headache pain is not well understood. Recent imaging evidence suggests a possible hypothalamic origin for a headache attack, but further research is needed. Migraine with aura is associated with a modest increase in the risk of ischemic stroke. The etiology for this association remains unclear. There is a paucity of evidence regarding treatments specifically aimed at the migraine with aura subtype, or whether migraine with vs without aura responds to treatment differently. Migraine with typical aura is therefore often treated similarly to migraine without aura. Lamotrigine, daily aspirin, and flunarizine have evidence for efficacy in prevention of migraine with aura, and magnesium, ketamine, furosemide, and single-pulse transcranial magnetic stimulation have evidence for use as acute treatments. Although triptans have traditionally been contraindicated in hemiplegic migraine and migraine with brainstem aura, this prohibition is being reconsidered in the face of evidence suggesting that use may be safe. The debate as to whether migraine with and without aura are different entities is ongoing. In an era of sophisticated imaging, genetic advancement, and ongoing clinical trials, efforts to answer this question are likely to yield important and clinically meaningful results.

Hypercoagulability and Migraine

BACKGROUND

A growing body of literature suggests that migraineurs, particularly those with aura, have an increased risk for ischemic stroke, but not via enhanced atherosclerosis. The theory that micro-emboli induced ischemia provokes cortical spreading depression (ie, symptomatic aura) in migraineurs but transient ischemic attacks in others highlights a potential role for hypercoagulability as a link between migraine (with aura) and stroke.

AIM

Our objective is to summarize the literature evaluating the association of migraine with various acquired or inheritable thrombophilic states, including those related to elevated estrogen levels, endothelial activation and dysfunction, antiphospholipid antibodies (aPL), deficiency of coagulation inhibitors, and presence of certain genetic polymorphisms.

FINDINGS

Although definitive studies are lacking, a preponderance of available evidence links migraine, and especially aura, to increased levels of estradiol (eg, oral contraceptive pill [OCP] use, pregnancy), thrombo- and erythrocytosis, von Willebrand factor (vWF) antigen, fibrinogen, tissue plasminogen activator (tPA) antigen, and endothelial microparticles. Studies of a link to migraine are conflicting for aPL, homocysteine, Protein S, and the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism. No association with migraine was found in meta-analyses of Factor V Leiden, and of prothrombin gene mutation. Within a large, young ischemic stroke sample, migraine with aura was associated with a thrombophilic state and with patent foramen ovale (PFO). In the non-stroke population, meta-analyses show an association of PFO and migraine with aura (MA), but two population-based studies do not support the link.

RECOMMENDATIONS

For persons with MA and (1) a personal history or family history of thrombosis, or (2) MRI evidence of micro-vascular ischemia or of stroke, an evaluation for hypercoagulability is warranted. In cases of MA alone, consider screening for markers of endothelial activation (eg, vWF, high sensitivity c-reactive protein [hs CRP], and fibrinogen). Rigorous management of other stroke risk factors is paramount, but efficacy of anti-thrombotic agents in the treatment of migraine is unproven. Closure of PFO is not routinely recommended based on negative randomized trials.

The Benefit and Safety of Aspirin for Primary Prevention of Ischemic Stroke: A Meta-Analysis of Randomized Trials

Background: Although aspirin is effective in the secondary prevention of stroke among men and women, its use in primary prevention remains controversial. We conducted a meta-analysis of randomized trials to evaluate the benefit and safety of aspirin for the primary prevention of ischemic stroke. Methods: We searched three electronic databases (Medline, the Cochrane Central Register of Controlled Trials, and Embase) for articles published before August 1st, 2016. Randomized trials reporting the effect of aspirin on the primary prevention of ischemic stroke and its side effects (hemorrhagic stroke and severe gastrointestinal bleeding) were included. We used a fixed-effect model to quantify the effect of aspirin on the primary prevention of stroke when the heterogeneity was low, or else applied the random-effect model. Results: Fourteen randomized trials were included. Overall, aspirin use was associated with a decreased risk of ischemic stroke compared with non-aspirin use (OR: 0.83, 95% CI: 0.74-0.93, P = 0.45). In subgroup analyses, the effect of aspirin on ischemic stroke in apparently healthy adults remained significant (OR: 0.83, 95% confidence interval: 0.74-0.94, I² = 22%, P = 0.28); while in patients with cardiovascular diseases there was no difference in the risk of ischemic stroke between aspirin and non-aspirin groups (OR: 0.75, 95% confidence interval: 0.44-1.29, P = 0.46). As for adverse effects, the prophylactic use of aspirin potentially increased the risk of serious bleeding events in a population of apparently healthy individuals and in patients with previous cardiovascular diseases. Conclusion: This meta-analysis of randomized trials indicated that both the apparently healthy adults and patients with cardiovascular diseases will derive little protective benefit from aspirin considering the increased risk of severe bleeding events.

Headache Rounds: Sudden, Transient Neurologic Symptoms in a Woman With Migraine

The following article is a Graham Headache Center headache rounds presentation at the Brigham and Women's Faulkner Hospital by fellows Roni Sharon and Melissa Rayhill with special guest Tobias Kurth. It summarizes the case of a 36-year-old female with no history of migraine in the past, presenting with several transient neurological episodes associated with headache. Her history, symptoms, imaging workup is reviewed. Following the case is a discussion of the differential diagnosis for the patient's symptoms along with a review of the association of migraine with and without aura with vascular neurological insult such as stroke. The article also discusses the clinical implications of migraine as a risk factor for stroke along with possible treatment recommendations.

A systematic review of aspirin in primary prevention: is it time for a new approach?

Background and Objectives

While evidence in support of aspirin use in secondary prevention is well documented, the role of aspirin in primary prevention remains unclear. We conducted a systematic literature review to evaluate aspirin use in cardiovascular disease (CVD) and cancer primary prevention, and consider whether aspirin’s role is set to become more clearly defined based on past and prospective studies.

Data Sources

Utilizing PubMed, the reviewers identified appropriate Medical Subject Headings (MeSH) terms to establish CVD-based studies, cancer-based studies, and studies on adherence.

Study Eligibility Criteria

Date restrictions of May 31, 2008 to May 31, 2013 were applied to capture the most robust meta-analyses and randomized controlled trials. Websites of relevant EU and US scientific societies were used to identify the key guidelines for aspirin use in primary prevention of CVD, and ClinicalTrials.gov was used to establish future or ongoing trials.

Results

Evidence in support of aspirin prophylaxis is conflicting, though some meta-analyses have underlined potential benefit in reducing cardiovascular events. Despite this apparent benefit, bleeding risk with aspirin is consistently higher versus control, and remains a concern. A reduction of cancer incidence and mortality after a least 3 and 5 years treatment, respectively, is also apparent with aspirin.

Conclusion

Available data on aspirin in primary prevention suggest a modest benefit for patients at high risk of CVD, and a promising benefit for those at risk of cancer. Future studies should help to elucidate whether the benefit of aspirin outweighs risk in appropriate patient groups.

Guidelines for the primary prevention of stroke: a statement for healthcare professionals from the American Heart Association/American Stroke Association

The aim of this updated statement is to provide comprehensive and timely evidence-based recommendations on the prevention of stroke among individuals who have not previously experienced a stroke or transient ischemic attack. Evidence-based recommendations are included for the control of risk factors, interventional approaches to atherosclerotic disease of the cervicocephalic circulation, and antithrombotic treatments for preventing thrombotic and thromboembolic stroke. Further recommendations are provided for genetic and pharmacogenetic testing and for the prevention of stroke in a variety of other specific circumstances, including sickle cell disease and patent foramen ovale.

Vascular biomarkers in migraine

AIM

Migraine has been associated with stroke as well as with several non-atherosclerotic vascular conditions leading to discussions about the potential role of endothelium in the etiopathogenesis of migraine and migraine-associated stroke. We present a systematic review of the literature on vascular biomarkers in migraine, including those suggesting endothelial activation and damage.

METHODS

We conducted a systematic literature search from 1990 to 2013 using multiple research databases with the keywords "migraine," "headache," "vascular," and "biomarkers." We used selected inclusion and exclusion criteria to create a final pool of studies for this review.

RESULTS

The literature search identified a total of 639 citations of which 129 were included in our review. The final pool of clinical- and population-based studies assessed the level of various biomarkers (e.g. inflammatory, prothrombotic, endothelial activation, endothelial repair) in migraineurs of varying ages, gender, and demographic characteristics. Although for each biomarker there is at least one study suggesting an association with migraine, in many cases the quality of evidence is poor and there are conflicting studies showing no relationship. The results were, therefore, in each case inconclusive.

CONCLUSION

This systematic review indicated that in migraine populations there are a number of positive vascular biomarker studies, including some involving novel biomarkers such as endothelial microparticles and endothelial precursor cells. These lend insight into possible pathophysiological mechanisms by which migraine may be associated with stroke. More high-quality studies are needed to establish whether a true association between promising vascular biomarkers and migraine exists.

The renin-angiotensin system: a possible contributor to migraine pathogenesis and prophylaxis

The presence of a tissue-based renin-angiotensin system, independent of the systemic one, has been identified in several organs including the brain. Experimental models have suggested the involvement of the renin-angiotensin system in neurogenic inflammation, susceptibility to oxidative stress, endothelial dysfunction, and neuromodulation of nociceptive transmission, thus potentially contributing to the pathogenesis of migraine. Genetic factors that increase susceptibility to migraine may include angiotensin-converting enzyme polymorphism, although available data are controversial. Clinical studies have suggested that angiotensin-converting enzyme inhibitors and angiotensin receptor blockers may be effective in migraine prophylaxis. However, further research should clarify whether the postulated preventive effect is attributable to a pharmacological action over and above the antihypertensive effect and should test their tolerability in subjects with normal blood pressure values. In patients with contraindications or not responding to conventional prophylactic drugs and in patients with comorbid arterial hypertension, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers may be used for migraine prophylaxis.

Guidelines for the prevention of stroke in women: a statement for healthcare professionals from the American Heart Association/American Stroke Association

PURPOSE

The aim of this statement is to summarize data on stroke risk factors that are unique to and more common in women than men and to expand on the data provided in prior stroke guidelines and cardiovascular prevention guidelines for women. This guideline focuses on the risk factors unique to women, such as reproductive factors, and those that are more common in women, including migraine with aura, obesity, metabolic syndrome, and atrial fibrillation.

METHODS

Writing group members were nominated by the committee chair on the basis of their previous work in relevant topic areas and were approved by the American Heart Association (AHA) Stroke Council's Scientific Statement Oversight Committee and the AHA's Manuscript Oversight Committee. The panel reviewed relevant articles on adults using computerized searches of the medical literature through May 15, 2013. The evidence is organized within the context of the AHA framework and is classified according to the joint AHA/American College of Cardiology and supplementary AHA Stroke Council methods of classifying the level of certainty and the class and level of evidence. The document underwent extensive AHA internal peer review, Stroke Council Leadership review, and Scientific Statements Oversight Committee review before consideration and approval by the AHA Science Advisory and Coordinating Committee.

RESULTS

We provide current evidence, research gaps, and recommendations on risk of stroke related to preeclampsia, oral contraceptives, menopause, and hormone replacement, as well as those risk factors more common in women, such as obesity/metabolic syndrome, atrial fibrillation, and migraine with aura.

CONCLUSIONS

To more accurately reflect the risk of stroke in women across the lifespan, as well as the clear gaps in current risk scores, we believe a female-specific stroke risk score is warranted.

Migraine patients should be cautiously followed for risk factors leading to cardiovascular disease

Migraine and ischemic strokes are two of the most prevalent diseases worldwide. Besides having a coincident symptomatology, for long researchers have been searching for a possible causal relation between these diseases. Current evidence based on data suggest that patients with aura migraine could have a doubled risk of developing an ischemic stroke, when compared to the rest of the population. At the same time, migraine sufferers apparently have higher incidences of risk factors for cardiovascular events. The aim of this review was not only to dissect some of the more compelling evidence based on data regarding this association, but also to discuss the possible clinical and therapeutic implications.

[Migraine and vascular risk]

Migraine with aura is well known to be associated with an increased risk of ischemic stroke. This risk dramatically increases in smokers and uses of oral contraceptives. Brain MRI studies suggest that migraine is associated with silent brain infarcts. Migraine is also established as a risk factor for significantly more cerebral white matter lesions. Recent data suggest that migraine is also associated with coronary artery disease. Data concerning an increase risk of mortality in migraine are controversial. The pathophysiology of the increased risk of ischemic events is unclear. Migrainous infarcts seem to be very rare. Migraine is associated with an increased risk of cervical artery dissection. Classical vascular risk factors are more common in migraineurs. Triptans are not associated with an increased risk of ischemic events. Another explanation is a probable endothelial dysfunction and a lower level of endothelial progenitor cells in migraine. A prothrombotic state in migraine is also another possible explanation due to genetic polymorphisms. Appropriate management for primary vascular prevention in migraineurs is not different from that proposed for the general population. Oral contraceptives should be avoided in migraineurs with aura, especially if they smoke.

New insights into the cardiovascular risk of migraine and the role of white matter hyperintensities: is gold all that glitters?

The role of migraine as an independent risk factor for cardiovascular events has been debated for several years, while it is more established for ischemic stroke. Recently, new studies have examined the likelihood of migraine to determine cardiovascular events, supporting the hypothesis of a predominant role in patients with migraine with aura, the risk including both sexes. In the literature, multiple pathophysiological mechanisms are described to explain this association, and are here discussed. Furthermore, the emerging evidence that a higher headache frequency and long-term migraine may worsen the cardio-metabolic profile in migraineurs (e.g. with a higher Framingham risk score and risk of developing atherosclerosis, insulin resistance and metabolic syndrome) makes it increasingly necessary to reduce the number and severity of attacks, not only to alleviate the painful symptoms, but also to improve the prognosis in these patients.

Aspirin's effect on platelet inhibition in migraineurs

OBJECTIVE

To assess the effect of aspirin on platelet reactivity in migraineurs.

BACKGROUND

Migraineurs, particularly women with aura and high monthly migraine frequency, are at risk for ischemic stroke and myocardial infarction (MI). High on-aspirin platelet reactivity (HAPR), or aspirin resistance, has been reported in females and patients with coronary artery disease, and is associated with adverse outcomes.

METHODS

Using a single group, pretest/posttest design, 50 migraineurs without prior history of stroke or MI were prospectively treated for 14 to 21 consecutive days with 325 mg generic enteric-coated aspirin, after undergoing a 14-day aspirin washout. Platelet reactivity was measured after aspirin washout and following aspirin treatment. Subjects were screened for HAPR using the VerifyNow™ Aspirin Assay (Accumetrics, San Diego, CA, USA). HAPR was defined as ≥ 460 Aspirin Reaction Units (ARU; primary endpoint).

RESULTS

Fifty subjects, 44 (88%) female, aged (mean ± standard deviation) 43 ± 12 years were enrolled. Twelve (24%; 95% CI 12-36%) subjects, all female, had HAPR and were classified as aspirin resistant. Subjects with HAPR had lower baseline hemoglobin levels than those without HAPR (P = .03). Baseline hemoglobin was significantly correlated with final ARU (r = -0.39, P = .005).

CONCLUSIONS

Findings of this exploratory study suggest that migraineurs have a higher prevalence of HAPR than healthy volunteers or patients with coronary artery disease taking aspirin 325 mg. The clinical implications of HAPR in migraine warrant further exploration due to the risk of stroke and MI and the potential need for antiplatelet therapy in this population.

Migraine and stroke: a complex association with clinical implications

Migraine and stroke are two common and heterogeneous neurovascular disorders with complex relations. Data show no firm association between stroke and migraine without aura--by far the most common type of migraine--but a doubling of the risk of ischaemic stroke in people who have migraine with aura. Migraine with aura is characterised by a low brain threshold for cortical spreading depression, the biological substrate of the aura, which can be triggered by many factors, including specific diseases that can by themselves increase the risk of ischaemic stroke. Whether the increased risk of ischaemic stroke applies to migraine with aura as a primary headache disorder or is partly due to migraine with aura secondary to other disorders remains to be elucidated.