Association of migraine headaches with anatomical variations of the Circle of Willis: Evidence from a meta-analysis

BACKGROUND: Several studies have attempted to investigate whether variations in the Circle of Willis (COW) are more common in migraine patients and whether the subsequent changes in perfusion may contribute to the pathomechanism of migraine. However, studies are not in agreement as to whether or not there is an increased prevalence of COW variations in migraineurs. OBJECTIVE: To determine if migraine headaches are associated with variations in morphology of the COW. METHODS: A systemic search of the major electronic databases was performed for articles studying the association of variations in the COW and migraine. Data on the prevalence of variations in patients with migraine were extracted and pooled into the meta-analysis. RESULTS: A total of four articles (n=807 patients) were deemed eligible for the meta-analysis. Migraine, regardless of subtype, was found to be associated with variations in the COW (OR=2.27, 95%CI 1.53-3.38, p<0.0001). An incomplete posterior circle (OR=2.60, 95%CI 1.79-3.76, p<0.00001) was found to be more strongly associated with migraine than an incomplete anterior circle (OR=2.01, 95%CI 1.15-3.53, p=0.01). In sub-group analysis, migraine with aura was found to be associated with both an incomplete posterior (OR=3.55, 95%CI 2.25-5.59, p<0.00001) and an incomplete anterior circle (OR=2.35, 95%CI 1.20-4.62, p=0.01). Migraine without aura was found only to be associated with an incomplete posterior circle (OR=2.10, 95%CI 1.39-3.17, p=0.0004). CONCLUSIONS: Migraine is associated with anatomical variations in both the anterior and posterior portions of the COW. However, larger prospective trials are needed to determine the true prevalence of variations and their pathological significance.