Anatomical Variants of the Circle of Willis and Brain Lesions in Migraineurs

Validation of an Oscillation Test for the Sonographic Assessment of Fetal-Type Posterior Cerebral Artery Variants in Migraine Patients with Visual Aura

Anatomic variants of the posterior circle of Willis, including the fetal-type posterior cerebral artery (FPCA), may contribute to the formation of visual aura in migraine. We sought to validate an oscillation test to investigate FPCA frequency in migraine using transcranial color-coded duplex ultrasonography (TCCS). First, the diagnostic accuracy of the oscillation test used to identify FPCA variants by TCCS was assessed in stroke patients with available computed tomography angiography (CTA) as the set gold standard. Second, in a cross-sectional study, patients with migraine with visual aura (MWVA) and migraine without aura (MWOA), as well as healthy controls, were prospectively recruited for sonographic assessment of FPCA variants. We compared FPCA frequency between migraine patients and controls using χ²-testing and performed logistic regression analysis to investigate a potential association between MWVA and the presence of FPCA variants. Specificity, sensitivity and positive and negative predictive values for sonographic identification of FPCA with CTA as the set gold standard were 93%, 77%, 63% and 96% (partial FPCA) and 99%, 78%, 88% and 98% (complete FPCA), respectively. One hundred forty-two migraine patients (39 ± 12 y, 90 MWVA and 52 MWOA) and 49 healthy controls (31 ± 12 y) were recruited. The χ² testing did not reveal significant differences in FPCA frequency as assessed by TCCS (unilateral or bilateral, partial and/or complete) between migraine patients and controls (MWVA: 40/90 or 44.4%, MWOA: 22/52 or 42.3%, controls: 24/49 or 49%, p = 0.79). Similarly, the frequencies of partial FPCA (p = 0.61) and complete FPCA (p = 0.27) did not vary significantly among groups. Logistic regression analysis revealed no interaction effect between migraine diagnosis and FPCA prevalence (any FPCA), when adjusted for age and sex. The sonographic oscillation test can be used as a non-invasive method to identify partial and complete FPCA variants with high specificity and reasonable sensitivity. Our findings suggest that FPCA variants do not contribute to the formation of visual migraine aura.

A critical review of the neurovascular nature of migraine and the main mechanisms of action of prophylactic antimigraine medications

INTRODUCTION

Migraine involves neurovascular, functional, and anatomical alterations. Migraineurs experience an intense unilateral and pulsatile headache frequently accompanied with vomiting, nausea, photophobia, etc. Although there is no ideal preventive medication, frequency in migraine days may be partially decreased by some prophylactics, including antihypertensives, antidepressants, antiepileptics, and CGRPergic inhibitors. However, the mechanisms of action involved in antimigraine prophylaxis remain elusive.

AREAS COVERED

This review recaps some of the main neurovascular phenomena related to migraine and currently available preventive medications. Moreover, it discusses the major mechanisms of action of the recommended prophylactic medications.

EXPERT OPINION

In the last three years, migraine prophylaxis has evolved from nonspecific to specific antimigraine treatments. Overall, nonspecific treatments  mainly involve neural actions, whereas specific pharmacotherapy (represented by CGRP receptor antagonists and CGRPergic monoclonal antibodies) is predominantly mediated by neurovascular mechanisms that may include, among others: (i) reduction in the cortical spreading depression (CSD)-associated events; (ii) inhibition of pain sensitization; (iii) blockade of neurogenic inflammation; and/or (iv) increase in cranial vascular tone. Accordingly, the novel antimigraine prophylaxis promises to be more effective, devoid of significant adverse effects (unlike nonspecific treatments), and more beneficial for the quality of life of migraineurs.

Migraine in Chiari 1 Malformation: a cross-sectional, single centre study

In Chiari 1 Malformation (CM1) the most frequent symptom is exertional headache, but other headache types have been reported, such as migraine. This cross-sectional study is aimed to examine the prevalence of migraine in a group of CM1 headache patients and to compare clinical-demographic characteristics between migraine and non-migraine patients. 427 adults were enrolled at the multidisciplinary Chiari Center in Torino. 230 headache patients were classified, based on radiological criteria. Frequencies (absolute/percentage values) were calculated in the whole sample for: migraine presence (with and without aura), gender, age, radiologic phenotypes and headache clinical characteristics. The association between CM1 diagnosis and headache characteristics (independent variables) and migraine diagnosis (dependent variable) was estimated by logistic regression models. Seventy-eight patients (67 females) out of 230 presenting headache had a migraine (34%), 44/78 (56%) with aura; in 58/78 (74%) migraine was comorbid with secondary headache attributable to CM1. Migraine prevalence in patients with isolated CM1 (52/120, 43.3%) was higher (p = 0.0016) than in all the other patients (26/110, 23.6%). Although migraine was prevalent in females (86%; 6:1 female:male ratio), age classes and gender were not risk factors for migraine at multivariate analysis, while migraine was associated with isolated CM1 phenotype (OR = 2.6). This study shows a high prevalence of migraine in CM1 patients and a significant association between migraine and isolated CM1. In patients with radiological evidence of CM1, particularly in the absence of neurological signs, a careful headache clinical characterization, according to the International Headache Society criteria, may be advised.

Advanced Imaging in the Evaluation of Migraine Headaches

The use of advanced imaging in routine diagnostic practice appears to provide only limited value in patients with migraine who have not experienced recent changes in headache characteristics or symptoms. However, advanced imaging may have potential for studying the biological manifestations and pathophysiology of migraine headaches. Migraine with aura appears to have characteristic spatiotemporal changes in structural anatomy, function, hemodynamics, metabolism, and biochemistry, whereas migraine without aura produces more subtle and complex changes. Large, controlled, multicenter imaging-based observational trials are needed to confirm the anecdotal evidence in the literature and test the scientific hypotheses thought to underscore migraine pathophysiology.

Circle of Willis variations in migraine patients with ischemic stroke

OBJECTIVES

Migraine is a risk factor for stroke, which might be explained by a higher prevalence in anatomical variants in the circle of Willis (CoW). Here, we compared the presence of CoW variants in patients with stroke with and without migraine.

MATERIALS AND METHODS

Participants were recruited from the prospective Dutch acute Stroke Study. All participants underwent CT angiography on admission. Lifetime migraine history was assessed with a screening questionnaire and confirmed by an interview based on International Classification of Headache Disorders criteria. The CoW was assessed for incompleteness/hypoplasia (any segment <1 mm), for anterior cerebral artery asymmetry (difference > 1/3), and for posterior communicating artery (Pcom) dominance (Pcom-P1 difference > 1/3). Odds ratios with adjustments for age and sex (aOR) were calculated with logistic regression.

RESULTS

We included 646 participants with stroke, of whom 52 had a history of migraine. Of these, 45 (87%) had an incomplete or hypoplastic CoW versus 506 (85%) of the 594 participants without migraine (aOR: 1.47; 95% CI: 0.63-3.44). There were no differences between participants with and without migraine in variations of the anterior or posterior CoW, anterior cerebral artery asymmetry (aOR: 0.86; 95% CI: 0.43-1.74), or Pcom dominance (aOR: 0.64; 95% CI: 0.32-1.30). There were no differences in CoW variations between migraine patients with or without aura.

CONCLUSION

We found no significant difference in the completeness of the CoW in acute stroke patients with migraine compared to those without.

Completion of the Circle of Willis Varies by Gender, Age, and Indication for Computed Tomography Angiography

OBJECTIVE

The circle of Willis (CoW) is the foremost anastomosis and blood distribution center of the brain. Its effectiveness depends on its completion and the size and patency of its vessels. Gender-related and age-related anatomic variations in the CoW may play an important role in the pathogenesis of cerebrovascular diseases. In this study, we analyzed computed tomography angiograms (CTAs) to assess for differences in CoW completion related to gender, age, and indication for CTA.

METHODS

A total of 834 CTAs were retrospectively analyzed for all CoW vessels to compare the incidence of complete CoW and variation frequency based on gender, age, and indication.

RESULTS

The incidence of complete CoW was 37.1% overall. CoW completion showed a statistically significant decrease with increasing age for all age groups in both men (47.0%, 29.4%, 18.8%) and women (59.1%, 44.2%, 30.9%). Completion was greater in women (43.8%) than in men (31.2%) overall and for all age groups. These gender differences were all statistically significant except for the 18-39 years age group. The most frequent of the 28 CoW variations were absent posterior communicating artery (PCOM) bilaterally (17.1%), right PCOM (15.3%), and left PCOM (10.9%). Ischemic stroke and the 18-39 years age group of hemorrhagic stroke showed a statistically significant reduction in completion relative to trauma.

CONCLUSIONS

The incidence of complete CoW is likely greater in women for all age groups and likely decreases with age in both genders. The most frequently absent vessel is likely the PCOM, either unilaterally or bilaterally. Completion may play a role in ischemic stroke and a subset of patients with hemorrhagic stroke.

White matter lesion burden in migraine with aura may be associated with reduced cerebral blood flow

Objective The objective of this study was to determine whether white matter hyperintensities (WMHs) in subjects with migraine are related to alterations in resting cerebral blood flow (CBF). Methods Migraine with aura (MWA), migraine without aura (MwoA), and control subjects were enrolled in a 1:1:1 ratio. WMH load was scored based on fluid-attenuated inversion recovery/T2-weighted magnetic resonance imaging (MRI) using a previously established semi-quantitative scale. Global and regional CBFs were quantified using arterial spin labelled perfusion MRI. Integrity of the circle of Willis was assessed with magnetic resonance angiography (MRA). Results A total of 170 subjects were enrolled (54 controls, 56 MWA, and 60 MwoA). There was no significant difference in subjects with ≥1 WMH across groups (22% controls, 29% MWA, 35% MwoA; p = NS). Similarly, high WMH load was not significantly different across groups (16.7% controls, 21.4% MWA, 25.0% MwoA; p = NS). High WMH load was strongly associated with increasing age (odds ratio: 1.08 per year, 95% confidence interval: 1.02-1.13, p = 0.01). Resting CBF was similar across groups, but was significantly higher in women. In MWA subjects with high WMH load, CBF was substantially lower ( p = 0.03). No association between WMH load and CBF was seen in control or MwoA subjects. Conclusions WHMs in MWA may be related to alterations in resting CBF.

Embolic Strokes of Unknown Source and Cryptogenic Stroke: Implications in Clinical Practice

Up to a third of strokes are rendered cryptogenic or of undetermined etiology. This number is specifically higher in younger patients. At times, inadequate diagnostic workups, multiple causes, or an under-recognized etiology contributes to this statistic. Embolic stroke of undetermined source, a new clinical entity particularly refers to patients with embolic stroke for whom the etiology of embolism remains unidentified despite through investigations ruling out established cardiac and vascular sources. In this article, we review current classification and discuss important clinical considerations in these patients; highlighting cardiac arrhythmias and structural abnormalities, patent foramen ovale, paradoxical sources, and potentially under-recognized, vascular, inflammatory, autoimmune, and hematologic sources in relation to clinical practice.

The Prevalence of Magnetic Resonance Imaging Hyperintensity in Migraine Patients and Its Association with Migraine Headache Characteristics and Cardiovascular Risk Factors

OBJECTIVES

To determine the frequency of hyperintense foci in migraine patients and the relationship with migraine headache characteristics and cardiovascular risk factors.

METHODS

Ninety patients with migraine headache (70 without aura and 20 with aura) were enrolled and interviewed. Information on their headache (severity, frequency, and mean disease duration) and other related data was obtained by completing a clinical checklist. Subsequently, brain magnetic resonance imaging (MRI) was performed and each patient was then evaluated for hyperintense lesions.

RESULTS

Of the 90 patients, 29 (32%) had silent hyperintense lesions on their MRI. The mean age of the patients with hyperintense foci was 41 years while those with no lesions was 33 years (p<0.010). Supratentorial hyperintense lesions represented the majority of lesions in the patients (n=46, 63%). Moreover, 56.3% of the lesions (n=41) were located within the right hemisphere. Cardiovascular risk factors such as smoking, serum cholesterol, oral contraceptive pills use, and body mass index (BMI) were not significantly different in these two groups (p>0.050). The lesions were found significantly more frequently in the patients who experienced chronic migraine (p=0.032).

CONCLUSION

Our study adds weight to the theory that disease duration has a key role in the formation of hyperintense brain lesions. Certain cardiovascular risk factors such as sex, smoking, serum cholesterol, and BMI, do not affect the presence or absence of such lesions, suggesting that the relationship between migraine and these lesions may be directly due to the effects of migraine itself.

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.

Migraine and stroke: "vascular" comorbidity

Several comorbidities are associated to migraine. Recent meta-analyses have consistently demonstrated a relationship between migraine and stroke, which is well-defined for ischemic stroke and migraine with aura (MA), even stronger in females on oral contraceptives or smokers. However, there seems to be no clear-cut association between stroke in migraineurs and the common vascular risk factors, at least in the young adult population. Migraineurs also run an increased risk of hemorrhagic stroke, while the association between migraine and cardiovascular disease remains poorly defined. Another aspect is the relationship between migraine and the presence of silent brain lesions. It has been demonstrated that there is an increased frequency of ischemic lesions in the white matter of migraineurs, especially silent infarcts in the posterior circulation territory in patients with at least 10 attacks per month. Although there is a higher prevalence of patent foramen ovale (PFO) in migraineurs, the relationship between migraine and PFO remains controversial and PFO closure is not a recommended procedure to prevent migraine. As an increased frequency of cervical artery dissections has been observed in migrainous patients, it has been hypothesized that migraine may represent a predisposing factor for cervical artery dissection. There still remains the question as to whether migraine should be considered a true “vascular disease” or if the comorbidity between migraine and cerebrovascular disease may have underlying shared risk factors or pathophysiological mechanisms. Although further studies are required to clarify this issue, current evidence supports a clinical management where MA patients should be screened for other concomitant vascular risk factors and treated accordingly.

Migraine and stroke: in search of shared mechanisms

BACKGROUND

Migraine, particularly with aura, increases the risk for ischemic stroke, at least in a subset of patients. The underlying mechanisms are poorly understood and probably multifactorial.

METHODS

We carried out an extended literature review of experimental and clinical evidence supporting the association between migraine and ischemic stroke to identify potential mechanisms that can explain the association.

RESULTS

Observational, imaging and genetic evidence support a link between migraine and ischemic stroke. Based on clinical and experimental data, we propose mechanistic hypotheses to explain the link, such as microembolic triggers of migraine and enhanced sensitivity to ischemic injury in migraineurs.

DISCUSSION

We discuss the possible practical implications of clinical and experimental data, such as aggressive risk factor screening and management, stroke prophylaxis and specific acute stroke management in migraineurs. However, evidence from prospective clinical trials is required before modifying the practice in this patient population.

Migraine without aura is not associated with incomplete circle of Willis: a case-control study using high-resolution magnetic resonance angiography

Background

The circle of Willis is an important source of collateral blood flow to maintain adequate cerebral perfusion, particularly in the posterior circulation. Some studies report a relationship between incomplete circle of Willis and migraine, whereas other studies show no difference between the prevalence of incomplete circle of Willis in migraineurs and controls. In the present study we compared the prevalence of incomplete circle of Willis in female migraine patients without aura to female healthy non-migraine controls.

Using 3-Tesla magnetic resonance angiography we recorded three-dimensional time-of-flight angiograms in 85 female participants (48 migraine patients without aura [median age 28 years] and 37 healthy controls [median age 25 years]). The images were subsequently analysed blindly by a neuroradiologist to detect incomplete circle of Willis.

Findings

We found no difference between the prevalence of incomplete circle of Willis in patients, 20/47 (43%), and controls, 15/37 (41%), p = 0.252. Post hoc analysis showed a significant relationship between age and prevalence of incomplete circle of Willis, p = 0.003.

Conclusion

We found no relationship between migraine without aura and incomplete circle of Willis.

Migraine with aura is associated with an incomplete circle of willis: results of a prospective observational study

Objective

To compare the prevalence of an incomplete circle of Willis in patients with migraine with aura, migraine without aura, and control subjects, and correlate circle of Willis variations with alterations in cerebral perfusion.

Methods

Migraine with aura, migraine without aura, and control subjects were prospectively enrolled in a 1∶1∶1 ratio. Magnetic resonance angiography was performed to examine circle of Willis anatomy and arterial spin labeled perfusion magnetic resonance imaging to measure cerebral blood flow. A standardized template rating system was used to categorize circle of Willis variants. The primary pre-specified outcome measure was the frequency of an incomplete circle of Willis. The association between circle of Willis variations and cerebral blood flow was also analyzed.

Results

170 subjects were enrolled (56 migraine with aura, 61 migraine without aura, 53 controls). An incomplete circle of Willis was significantly more common in the migraine with aura compared to control group (73% vs. 51%, p = 0.02), with a similar trend for the migraine without aura group (67% vs. 51%, p = 0.08). Using a quantitative score of the burden of circle of Willis variants, migraine with aura subjects had a higher burden of variants than controls (p = 0.02). Compared to those with a complete circle, subjects with an incomplete circle had greater asymmetry in hemispheric cerebral blood flow (p = 0.05). Specific posterior cerebral artery variants were associated with greater asymmetries of blood flow in the posterior cerebral artery territory.

Conclusions

An incomplete circle of Willis is more common in migraine with aura subjects than controls, and is associated with alterations in cerebral blood flow.