Is migraine associated with right-to-left shunt a separate disease? Results of the SAM study

Recent progress in patent foramen ovale and related neurological diseases: A narrative review

Patent foramen ovale (PFO) is a common congenital cardiac abnormality when the opening of the interatrial septum is not closed in adulthood. This abnormality affects 25% of the general population. With the development of precision medicine, an increasing number of clinical studies have reported that PFO is closely related to various neurological diseases such as stroke, migraine, obstructive sleep apnea, and decompression syndrome. It has also been suggested that PFO closure could be effective for preventing and treating these neurological diseases. Therefore, increasing attention has been given to the prevention, diagnosis, and treatment of PFO-related neurological diseases. By reviewing existing literature, this article focuses on the pathogenesis, epidemiology, and clinical characteristics of PFO-related neurological diseases, as well as the prevention and treatment of different neurological diseases to discuss, and aims to provide current progress for this field and decision-making evidence for clinical practice.

Can aura migraine be elicited by isolated pulmonary arteriovenous fistula?-A case report

A pulmonary arteriovenous fistula (PAVM) is an abnormal blood vessel that creates a direct connection between a pulmonary artery and its tributary vein bypassing capillary filter, establishing as a consequence of a low-resistance right-to-left shunting (RLS). The vast majority of PAVMs are congenital appearing more often in females than in males. A great number of patients with PAVMs is suffering concurrently from hereditary hemorrhagic telangiectasia (HHT) whose incidence is around 1 in 5,000. Very few cases of acquired PAVMs have been described in the literature. Paradoxical embolism through PAVMs can cause systemic desaturation, cyanosis, and serious cerebrovascular ischemic events (transient ischemic attacks, strokes, and intracranial abscess), even when the abnormal blood vessel is small (diameter <3 mm). Notably, it has been reported a high prevalence of aura migraine (MHA) symptoms in patients with PAVMs and concomitant HHT. We described in this study the case of a young aura migraineur female patient without HHT in whom isolated PAVM below the detection limit of pulmonary angiography and chest computed tomography angiography (CTA) has been documented by contrast Transthoracic and Transesophageal Echocardiography (cTTE/TEE) showing a delayed (>17 s) RLS coming from left pulmonary veins to left atrium while a patent foramen ovale (PFO), small atrial septal defects or septum primum fenestration could not be detected despite several attempts. Contrast Transcranial Doppler (cTCD) confirmed a delayed (>16 s) RLS with two short "shower" patterns corroborating the diagnosis of an extra-cardiac RLS. During the right heart catheterization and pulmonary angiography, it was impossible to cross the interatrial septum with a multipurpose catheter. The patient was finally discharged with off-label thienopyridine agents (clopidogrel 75 mg die) in terms of primary prophylaxis for paradoxical right-to-left embolization of thrombotic material ultimately. Aura migraine symptoms were nearly abolished by P2Y12 platelet inhibition, suggesting a platelet-based mechanism. During 2 years of clinical follow-up on thienopyridine therapy, the resolution of aura migraine episodes was definitively accomplished with significant improvement in her quality of life.

Shorter visual aura characterizes young and middle-aged stroke patients with migraine with aura

OBJECTIVE

To identify the clinical profile and aura characteristics of patients with Migraine with Aura (MwA) having acute cerebral ischemia, we compared stroke phenotype and risk factors in stroke patients with (S+MwA+) or without (S+MwA-) MwA and aura features in MwA patients with (S+MwA+) or without (S-MwA+) stroke.

METHODS

In this retrospective multicenter case-control study, we reviewed stroke phenotypes and vascular risk factors in S+MwA+ and S+MwA- patients younger than 60 years and risk factors and aura type, duration, onset age, and the frequency in the previous year in S+MwA+ patients and S-MwA+ subjects matched for age and disease history, investigated for patent foramen ovale (PFO).

RESULTS

539 stroke (7.7% S+MwA+) and 94 S-MwA + patients were enrolled. S+MwA+ patients were younger (p =.0.004) and more frequently presented PFO [OR 4.89 (95% CI 2.12-11.27)], septal interatrial aneurism [OR 2.69 (95% CI 1.15-6.27)] and cryptogenic ischemic stroke (CIS) [OR 6.80 (95% CI 3.26-14.18)] than S+MwA- subjects. Significant atherosclerosis was not detected in S+MwA+ patients. Compared to S-MwA+, S+MwA+ patients were characterized by visual [OR 3.82 (95% CI 1.36-10.66)] and shorter-lasting (20.0 min IQr 13.1 vs 30.0 min IQr 25.0; p < 0.001) aura, and PFO [OR 1.26 (95% CI 1.03-1.54)]. Regression analysis evidenced that only shorter aura duration associated with stroke (p = 0.001). High-risk PFO was equally represented in S+MwA-, S+MwA+, S-MwA+ groups.

CONCLUSIONS

Shorter visual aura and CIS characterize MwA patients with stroke. Although more prevalent, PFO can not be considered the main responsible for the increased stroke risk in MwA patients but as a part of a complex multifactorial condition.

The Role of Endothelial Dysfunction in the Pathophysiology and Cerebrovascular Effects of Migraine: A Narrative Review

Background and Purpose

Migraine is a complex neurovascular disorder whose triggers are not entirely understood. Endothelial dysfunction might play a role in migraine, and there have been numerous reports on endothelium dysfunction and migraine pathophysiology, but their reciprocal cause–effect relationship remains unclear. This review reports the current evidence on endothelium dysfunction, its link with migraine, and its possible consequences for cerebral hemodynamics.

Methods

We performed a systematic literature search of PubMed up to March 2020. We included 115 articles in a narrative review.

Results

Several studies have demonstrated that endothelium dysfunction may play an important role in migraine. Despite the lack of specific biomarkers, there is evidence of oxidative stress and inflammation—two of the primary causes of endothelial damage—in migraine. The main consequences of endothelial dysfunction are increased vascular tone, thrombosis, inflammation, and increased vascular permeability. As a consequence of oxidative stress, the activity of endothelin-1 is not counterbalanced by nitric oxide (NO), whose levels decrease to lead to vasoconstriction and a possible contribution to cortical spreading depression. NO is involved in pain perception via the cyclic guanosine monophosphate (cGMP) pathway and the induction of calcitonin gene-related peptide. Oxidative stress may induce a hypercoagulable state that mainly affects platelet function through different mechanisms. Endothelial dysfunction seems to be particularly pronounced in migraine with aura (MA). Endothelial dysfunction in migraine particularly involves intracranial vessels, since flow-mediated dilation cannot detect overt peripheral vascular dysfunction.

Conclusions

Endothelial dysfunction is a vascular risk marker. How it impacts migraine, and particularly MA, needs to be understood better by defining its possible role in increasing the stroke risk in migraine patients.

Relationship between non-headache symptoms and right to left shunt in episodic migraine. A single-center cross-sectional study

The relationship between right to left shunt (RLS) and non-headache symptoms (NHS) in episodic migraine is unknown. This study aimed to investigate the incidence and classification of RLS in episodic migraineurs, calculate the occurrence rate of NHS, and analyze the associations between RLS and NHS. We consecutively recruited 204 episodic migraine patients. Contrast-enhanced transcranial doppler was adopted to screen RLS. Structured questionnaire via face-to-face survey was conducted to collect clinical data. A total of 172 episodic migraineurs were included in the final analysis, of which 20 cases were migraine with aura. The positive rate of RLS was 47.1%, of which 50 cases (29.0%) had small shunt (Grade 1) and 31 cases (18.1%) had mid-large shunt (Grade 2-4). The most common NHS was nausea (115 (66.9%)), followed by headache aggravation with physical activity (96 (55.8%)), dizziness (93 (54.1%)), vomiting (77 (44.8%)) and phonophobia (74 (43.0%)). Yawning was more common in Grade 2-4 group than Grade 0 group (p = 0.012), while no statistical differences among other groups. Grade 2-4 group had a higher rate of headache aggravation with physical activity than grade 0 group (p = 0.008). Binary logistic regression analysis showed that yawning at premonitory phase, headache aggravation with physical activity and cranial autonomic symptoms during attack are independent predictors of RLS. In conclusion, yawning and headache aggravation with physical activity are more common in migraine patients with RLS. Besides aura, particular NHS may also serve as indicators for screening RLS in episodic migraineurs.

The Correlation Between Migraine and Patent Foramen Ovale

Background: Migraine is a widespread neurological disorder. The patent foramen ovale (PFO) is a remnant of the fetal circulation. Multiple studies suggest that migraine is more prevalent in subjects with PFO and vice versa. It is unclear if there is a causal relationship or simply a co-existence of these two conditions. Furthermore, the treatment of migraine with percutaneous closure PFO remains controversial.

Methods: We reviewed studies pertaining to the relationship between PFO and migraine as well as the effects of treatments on migraine attacks.

Results: We briefly summarized potential pathophysiological mechanisms of migraine, and elaborated on migraine type, frequency, and clinical symptoms of migraine with PFO and the clinical features of PFO with migraine. We also addressed the effects of PFO closure on migraine attacks.

Conclusion: The evidence supports a “dose-response” relationship between migraine and PFO although more work needs to be done in terms of patient selection as well as the inclusion of an antiplatelet control group for PFO closure interventions to uncover possible beneficial results in clinical trials.

Clinical features of right-to-left shunt in the different subgroups of migraine

OBJECTIVE

Several investigations have documented an association between migraine and right-to-left shunt (RLS). However, whether there are specific clinical features that can distinguish between migraine patients with and without RLS is unclear. This study aims to explore whether there are specific clinical features that can distinguish between migraine patients with and without RLS, and to investigate the relationship between the degree of shunt and clinical parameters of headache.

METHODS

In this study, we enrolled consecutive migraineurs who underwent a structured, standardized questionnaire for family and personal history and for detailed migraine features. RLS was diagnosed based on a contrast enhancement transcranial Doppler (c-TCD) examination.

RESULTS

Overall, 113 migraine with aura (MA) and 192 migraine without aura (MO) patients were included. Patients with MA and RLS (MARLS+) had a higher frequency for sensory aura symptoms than those with MA without RLS (MARLS-) (27.4% vs. 10.0%, p = .03). Patients with MO and RLS (MORLS+) presented with significantly younger initial age of migraine onset and experienced more severe pain intensity than those with MO without RLS (MORLS-) (mean ± SD, 25.6 ± 8.9 vs. 29.8 ± 12.7 years, p = .008 and 5.9 ± 1.4 vs. 5.3 ± 1.3, p = .006, respectively). There was no relationship between the degree of shunt and the clinical parameters of headache.

CONCLUSIONS

Our results indicate that MO patients presented with a younger initial age of migraine onset and that sensory aura symptoms in MA patients may predict the presence of RLS. However, we did not find support for relationship between the degree of shunt and clinical parameters of headache.

The frequency and importance of chest pain in midterm follow up of transcatheter closure of interatrial septal defect

Introduction: We evaluated chest pain alongside other midterm subjective and objective complications of the transcatheter closure of atrial septal defects (ASDs) and patent foramen ovales (PFOs) with various closure devices.

Methods: This cross-sectional study, performed from March 2010 to October 2015 in Rajaie Cardiovascular, Medical, and Research Center, evaluated 313 patients (mean age = 29.12 ± 10 years, 32.9% male) for probable complications associated with the transcatheter occlusion of secundum ASDs (n = 289, mean age = 30.5 ± 11.4 years, 28% male) or PFOs (n = 24, mean age = 42.8 ± 10.2 years). ASD closure was performed under sedation and transesophageal echocardiography (TEE) guidance. Duration of follow-up was 12 ± 3 months (mean follow-up = 11.52 months).

Results: Among the subjective complications, chest pain was the most frequent complaint during the follow-up period and although it was common (7.3%), a clear cardiac etiology was rare. Thirteen (4.2%) patients reported palpitation during the follow-up period, and 4 had documented arrhythmias—including atrial flutter, atrial fibrillation, and 2:1 atrioventricular block. Migraine with or without aura occurred in 1.6% of the patients. Objective complications comprising tamponade, device embolization, and thrombus formation occurred in 6 (1.9%) patients. There was no procedure-related mortality in our patients.

Conclusion: Transcatheter closure of PFOs and secundum-type ASDs in our adult patients using ASD septal occluders was associated with a high degree of success, minimal procedural subjective and objective complication rates, and excellent short- and midterm results. Although chest pain was common after the first month following ASD closure, there was no cardiac death or aortic erosion in 11.52 months follow up.

PFO and Migraine: Is There a Role for Closure?

Observational studies suggest that closure of a patent foramen ovale for other indications may reduce or even eliminate migraine attacks, particularly migraine with aura. The first randomized clinical trial of patent foramen ovale (PFO) closure for prevention of migraine, the MIST trial, showed negative results. The results of the other two completed studies in this area have recently been published in the last year. PRIMA and PREMIUM were also both negative for their primary endpoints. The PREMIUM trial did show a reduction in headache days in the migraine with aura subgroup but the final results of this subset analysis have not been published. There may be an as yet undetermined subgroup of patients with migraine who would benefit from closure, but slow recruitment has been a barrier to further study. Several potentially life-threatening procedure-related adverse events occurred in the clinical trials. At this time, we recommend against offering PFO closure as a preventive treatment for migraine. Based on available observational data, patients for whom PFO closure is indicated for other reasons may see some improvement in their migraines.

Long-term follow-up after percutaneous closure of patent foramen ovale with Amplatzer PFO Occluder: a single center experience

Introduction

Patent foramen ovale (PFO) is associated with the occurrence of cryptogenic strokes, transient neurological ischemic attacks (TIA) and migraine. Therefore despite the recent ambiguous results of prospective controlled trials, percutaneous closure of PFO is still performed in many centers.

Aim

To evaluate the safety and effectiveness of percutaneous PFO closure in the prevention of recurrence of neurologic events and migraine symptoms in long-term observation.

Material and methods

In 70 patients (31 male, age: 38 ±18 years) percutaneous PFO closure was successfully performed with the Amplatzer PFO Occluder. An interview in conjunction with neurological follow-up was performed in all patients to reveal recurrence of embolism such as TIA or stroke and the presence of migraine symptoms before and after the procedure.

Results

The mean follow-up period was 857 ±363 days (median: 571 days). No serious complications of the procedure and no death were observed. Neurological events recurred in 5 (7.1%) patients – stroke in 1 patient, TIA in 3 patients, ocular embolism in 1 patient. All of these patients were over 40 years old or had other cardiovascular risk factors. Migraine was observed in 21 (30%) patients before the procedure and in 11 (15.7%) after the procedure (p = 0.04).

Conclusions

The complication rate and recurrence of neurological events in young patients after PFO closure are low. However, careful qualification and postprocedural monitoring of the patients are necessary. Patent foramen ovale closure seems to result in attenuation of migraine symptoms.

Migraine with aura: a predictor of patent foramen ovale in children and adolescents

BACKGROUND

The prevalence of patent foramen ovale (PFO) is higher among adult migraine patients. The purpose of this study was to determine the frequency of PFO in children and adolescent migraine patients.

METHODS AND RESULTS

A total of 32 patients with migraine (divided into two subgroups, the migraine with aura subgroup and the migraine without aura subgroup) and 31 normal control subjects were enrolled in this study. All of the participants underwent transthoracic echocardiography with an agitated saline test. We compared the prevalence of PFO and the severity of right-to-left shunt (RLS) in each group. No statistical difference in age and sex ratio was observed in either group. The prevalence of PFO was higher in the migraine group than in the control group, but without statistical significance (46.9% vs. 25.8%, P = 0.084). The prevalence of PFO was significantly higher in the migraine with aura subgroup than in the migraine without aura subgroup ( P = 0.031) and the normal control group ( P = 0.0074). Migraine with aura was the only significant factor showing an association with PFO (<0.01). RLS size did not have an influence on migraine.

CONCLUSIONS

Considering the significantly high prevalence of PFO in pediatric migraine with aura patients, migraine with aura is a clear predictor of PFO among children and adolescents.

Cerebral distribution of white matter lesions in migraine with aura patients

OBJECTIVE

The objective of the study was to compare the cerebral distribution of white matter lesions (WMLs) between migraine patients with different aura symptoms.

METHODS

Migraine with aura (MA) patients were consecutively enrolled as part of the Shunt-Associated Migraine (SAM) study. According to clinical symptoms, aura was classified as motor, aphasic, sensory, visual or vertebrobasilar. Standard and FLAIR (fluid attenuated inversion recovery) T(2)-weighted MRI sequences were inspected for WMLs by three independent raters blinded to clinical data. WMLs were assessed in the periventricular areas (PV-WMLs) with the Fazekas scale and in the deep white matter (D-WMLs) with the Schelten's scale. Interobserver agreement was good to excellent (k = 0.64 to 0.96, p < .0001).

RESULTS

One hundred and eighty-five patients (77% women) were included. Aura symptoms were classified as visual in 172 (99%) patients, sensory in 76 (42%), aphasic in 54 (30%), motor in 39 (21%) and vertebrobasilar in 17 (9%) patients. One hundred and four patients (57%) exhibited more than one type of aura. D-WMLs were mainly detected in the frontal lobes (86%). There was no association between type of aura and the presence of WMLs in any cerebral location.

CONCLUSION

Aura symptoms do not influence the cerebral distribution of WMLs associated with migraine disease.

Migraine and patent foramen ovale: state of the science

Migraine is a prominent cause of recurrent pain, affecting 12% of the population. In several case series, approximately 50% of migraineurs with aura were found to have patent foramen ovale (PFO). The pathophysiological mechanism is speculated to be passage of microemboli and vasoactive chemicals through the PFO, thereby evading pulmonary filtration and triggering migraine symptoms. This article presents the results of retrospective and prospective research studies documenting the effects of PFO closure on migraine symptoms and presents emerging theories on possible pathologic mechanisms that may partially explain the increased risk of ischemic stroke in the migraine population. Finally, evidence-based recommendations are presented for health care providers for managing patients who have migraine and PFO.

Right-to-left shunt is common in chronic migraine

Our aim was to determine the prevalence of right-to-left shunt (RtLS) in patients with chronic migraine (CM), and to correlate the presence and grade of RtLS with aura and neurological symptoms, and duration and severity of disease. The prevalence of RtLS in migraine without aura is similar to that of the general population (between 20 and 35%). In migraine with aura, the prevalence is much higher (approximately 50%). The prevalence in CM, with or without aura, is unknown. Consecutive patients between the ages of 18 and 60 years with CM attending a tertiary care specialty headache clinic over an 8-week period were eligible. There were 131 patients in the study. A structured diagnostic interview was performed. Bubble transcranial Doppler with Valsalva manoeuvre determined RtLS presence and grade. Sixty-six percent (86/131) of patients had RtLS, a statistically significantly greater rate than those reported in the general population and in migraine with or without aura ( P < 0.001). There was no difference in RtLS rate or grade between those with and those without aura. Specific headache features and the presence of neurological symptoms were similar between those with and those without RtLS. Compared with both the general population and the episodic migraine population (with and without aura), patients with CM, with or without aura, are more likely to have RtLS. The clinical implications of our findings need to be determined.

Usefulness of transcatheter patent foramen ovale closure in migraineurs with moderate to large right-to-left shunt and instrumental evidence of cerebrovascular damage

Transcatheter patent foramen ovale (PFO) closure might be effective in improving migraines. To assess the efficacy of PFO closure in migraineurs with a moderate to large right-to-left shunt and instrumental evidence of embolic cerebral damage, 76 highly symptomatic migraineurs were prospectively investigated. The presenting clinical syndrome was stroke in 16 patients, repeated transient ischemic attack in 32 patients, and lone migraine associated with cerebral ischemic lesions on magnetic resonance imaging in 28 patients. Migraine severity was assessed before PFO closure and monthly for 6 months after discontinuation of antiplatelet therapy. At the end of 12 months of follow-up, the averaged postprocedural total score was compared with the baseline score. Transcatheter PFO closure was successful in all patients, and the 12-month PFO closure rate was 97%. The baseline total migraine score was similar in patients with stroke, transient ischemic attack, and lone migraine (6.8 +/- 1.6, 6.7 +/- 1.4, and 6.9 +/- 1.7 respectively, p = NS). After a mean follow-up of 13.7 +/- 2.4 months, no recurrent cerebrovascular episodes had occurred. At the end of the follow-up period, a significant reduction in the total migraine score was observed in all groups, regardless of the initial clinical presentation. Migraine was completely abolished in 35 patients (46%), improved in 27 (36%), and unchanged in 14 (18%). The proportion of patients with migraine suppression and improvement was similar in the 3 groups. In conclusion, in highly symptomatic migraineurs with previous ischemic cerebral events and instrumental evidence of cerebral embolism, transcatheter PFO closure can result in improvement of migraine severity in a high percentage of patients.

A case of atypical sporadic hemiplegic migraine associated with PFO and hypoplasia of vertebro-basilar system

We describe the case of a patient with atypical hemiplegic migraine and associated basilar symptoms, where a large patent foramen ovale (PFO) and hypoplasia of basilar artery were found. The longer period of 4-year remission of the headache attacks was coincident with the percutaneous PFO closure. When 5 years after, hemiplegic migraine attacks relapsed, with more relevant basilar symptoms, a mild re-opening of PFO was found. The atypical presentation of attacks with basilar symptoms and prolonged hemiplegia does not strictly fit the diagnostic criteria of ICHD-II.

Migraine and patent foramen ovale: connecting flight or one-way ticket?

CONTEXT

The genesis of migraine in patients with patent foramen ovale (PFO) and its relationship with paradoxical stroke is still debated. Some authors agree that migraine with aura and PFO have higher coincidences than would be expected by chance and that it is possible that both conditions are inherited together.

OBJECTIVE

The present review aims to make a comprehensive attempt at clarifying the PFO-migraine connection in light of recent evidence from literature.

EVIDENCE ACQUISITION

A Medline search using both OVID and PubMed was performed by searching for literature in English regarding randomized trials, prospective cohort studies, meta-analyses, reviews and editorials about PFO and migraine between 1998 and 2008. Search key words were 'migraine' and 'patent foramen ovale' matched with 'prevalence', 'echocardiography', 'transcranial Doppler ultrasound', 'magnetic resonance imaging', 'coagulation abnormalities' and 'transcatheter closure treatment'. Additional reference material was obtained from the proceedings of relevant conferences on PFO and migraine, and the author's personal experience.

EVIDENCE SYNTHESIS

Echocardiographic, transcranial Doppler and MRI studies suggest that migraine patients are at higher risk of stroke compared with the normal population and often have white matter brain lesions on MRI. A large proportion of PFO patients have migraine, in particular migraine with aura, and migraine with aura patients plus PFO have larger shunts compared with migraine-free patients. It has been suggested that patients with migraine and large PFO have an increased risk of paradoxical embolism. Most patients with PFO and migraine respond well to transcatheter closure and this fact is unlikely to be caused just by a placebo effect.

CONCLUSIONS

Although many gray areas are still present, migraine with aura and large PFO seem to be strictly related to both anatomic and functional states at least in a proportion of patients.

Migraine and stroke: the role of oral contraceptives

The use of oral contraceptives (OCs) confers an increased risk for ischaemic stroke (IS). This risk slightly decreases, but remains significant, if low-dose formulations are used, particularly if other risk factors, such as hypertension or smoking, are associated. Some inherited prothrombotic conditions (e.g., Factor V Leiden, G20210A prothrombin or methylenetetrahydrofolate reductase C677T polymorphism) could also greatly increase the IS risk if present in OC users. Migraine, particularly with aura, is an independent risk factor for IS, and the patient's IS risk is probably affected by other individual risk factors (e.g., age, genetic predisposition to thrombosis, presence of patent foramen ovale or enhanced platelet aggregation) which seem to be over-represented in migraine patients. IS risk among migraineurs is further increased when OCs are currently used and can become very high if associated with smoking. Consequently, in 2004 the WHO stated in its 'Medical Eligibility Criteria for Contraceptive Use' that women suffering from migraine with aura at any age should never use OCs. Moreover, since the exposure to the effects of OCs may greatly increase the IS risk in some migraine subpopulations with specific personal characteristic, testing for these risk factors may allow for more accurate stratification of the population at risk before long-term use of OCs is prescribed.

Comorbid neuropathologies in migraine: an update on cerebrovascular and cardiovascular aspects

Several conditions are comorbid with migraine; our review is focused on the relation between migraine, and cerebrovascular and cardiovascular diseases. Despite many studies showed an association between migraine and patent foramen ovale, it is still not known whether its presence might be causal for the migraine pathogenesis and currently its closure cannot be recommended for migraine prevention. On the contrary, conflicting epidemiological data link migraine to arterial hypertension and the use of antihypertensive agents acting on the renin-angiotensin system sounds promising in migraine prevention. A complex bidirectional relation exists between migraine and stroke, and new evidences show a clear association between migraine and coronary heart disease. In both conditions, migraine represents a defined risk factor although the magnitude of the risk varies across the different studies. However, since the risk is low in the general population, it is not possible to identify which migraineurs will develop a cardiovascular or a cerebrovascular event making difficult to apply preventive measures.