Age-Related Variations in the Circle of Willis Among North Indian Adults: A Magnetic Resonance Angiographic Study

Background: The Circle of Willis (CoW) is the principal collateral arterial network of the brain. Variations in its configuration may influence cerebral blood flow, susceptibility to ischemic stroke, and outcomes of neurovascular interventions. The present study aimed to evaluate age-related variations of the Circle of Willis among North Indian adults using Magnetic Resonance Angiography (MRA). Material and Methods: This hospital-based observational cross-sectional study included 169 adult subjects undergoing brain MRA. Three-dimensional Time-of-Flight (3D TOF) MRA was performed using a 1.5 Tesla MRI system. Participants were categorized into four age groups (17–30, 31–50, 51–70, and 71–85 years). Images were assessed for basilar artery lateralization, hypoplasia, and absence of arterial segments of the Circle of Willis. Statistical analysis was performed using SPSS version 30.0. Results: The largest proportion of subjects belonged to the 51–70 years age group (43.2%). Basilar artery lateralization was observed in 30 cases, with the highest frequency in the 51–70 years age group (53.3%). Hypoplasia was the most common variation (120 cases), while arterial absence was identified in 23 cases. Posterior circulation involvement (75.8%) was more frequent than anterior circulation involvement (24.2%). A complete Circle of Willis was present in only 15.4% of subjects, whereas 84.6% demonstrated an incomplete configuration. Left-sided hypoplastic variations predominated and were statistically significant (p = 0.003). Conclusion: Anatomical variations of the Circle of Willis are highly prevalent among North Indian adults and occur predominantly in the posterior circulation. The high frequency of variations in older age groups highlights the influence of age-related vascular remodeling. Recognition of these variants is important for anatomical understanding, neurovascular imaging, cerebrovascular risk assessment, and surgical planning.

Keywords: Circle of Willis; Magnetic Resonance Angiography; Age-related variations; Hypoplasia; Posterior circulation; Cerebral collateral circulation.