CLASSIFICATION OF ANATOMIC VARIATIONS OF THE CIRCLE OF WILLIS IN THE PEDIATRIC AGE GROUP

Objective: The Circle of Willis (CoW) is a vascular ring formed by the anastomosis of branches from the internal carotid and vertebral arteries at the base of the brain. Anatomic variations of the CoW are common and may influence cerebrovascular dynamics. This study aims to provide reference data on the diameters, morphology, and anatomic variations of the arteries forming the CoW in pediatric patients.Materials and Methods: In this retrospective study, contrast-enhanced cranial magnetic resonance imaging scans of 110 pediatric patients were analyzed. The study population was divided into three age groups (0–3, 3–12, and 12–18 years). The diameters of the arterial components of the CoW were measured; arteries with a diameter of < 1 mm were defined as hypoplastic, and complete absence was considered as aplasia. Structure was classified as complete or incomplete, while additional anatomic variants were recorded separately. The anterior communicating artery (AComA) was evaluated only as present or absent (aplastic) due to its small size in pediatric populations.Results: A complete CoW configuration was observed in 48.2% of cases, with the highest prevalence (52.8%) in the 12-18 year group. AComA aplasia and left posterior communicating arteries (PComA) aplasia were the most common variations. Other variations included duplicated right and left posterior communicating arteries, a fenestrated right posterior cerebral artery, and a common trunk giving rise to both right and left anterior cerebral arteries.Conclusion: This study provides valuable reference data on the CoW variations in pediatric patients, which are essential for safer cerebrovascular operations and informed clinical decision-making.