فهرست نشریات علمی دسترسی آزاد ایران

The Circle of Willis (CoW) is a key arterial ring at the brain’s base that provides collateral circulation during arterial occlusion. Despite its clinical importance, CoW anatomy shows notable variation across individuals, age groups, and populations. These differences can affect the risk and presentation of cerebrovascular diseases such as ischemic stroke and aneurysm; yet integrated data on prevalence, clinical relevance, and geographic distribution remain limited. The objective of this study is to systematically review and analyse the anatomical CoW variations, their clinical associations, and correlations with demographic (age and sex) and geographic factors. Following PRISMA 2020 guidelines, a systematic search was conducted in PubMed, Scopus, Web of Science, and Embase through May 2025. Included studies were cadaveric, radiological, or surgical and reported anatomical variants and/or related clinical outcomes. Data were pooled using random-effects models. Subgroup analyses, logistic regression, and Newcastle-Ottawa Scale (NOS) quality assessments were performed. Geographic trends were visualized via heatmaps. Only 21.2% of cases had a complete CoW. The most common anomaly was bilateral absence of the posterior communicating artery (PCoA) (25.1%), which significantly increased stroke risk (OR = 1.82). Complete ring anomalies carried an even higher risk (OR = 2.03). Variants were more frequent in older individuals and studies with NOS scores ≥8. African populations showed higher rates of stroke-related variants; European populations had more anatomical anomalies. CoW variations are clinically significant and influenced by age and geography. These findings support the integration of vascular imaging in stroke risk assessment and encourage standardized, multicentre research.