Objectives: The aim of this study was to investigate anatomic variants and anomalies of the circle of Willis using computed tomography angiography (CTA). Methods: CTA images of 770 patients obtained from Tepecik Training and Research Hospital between January 2012 to January 2017 were retrospectively reviewed to identify the anatomical vascular variations of the circle of Willis. Results: After exclusion, 751 patients (348 females, 403 males, mean age 54.6 years, range 18–90 years) were enrolled into the study. The anatomical variations related to the posterior communicating artery (PcoA) were the most common, whereas anatomical variations related to the middle cerebral artery (MCA) were the least common variations among arteries. Hypoplasia of the A1 segment was the most common (14.6%) variation of the anterior cerebral artery (ACA) and fenestration of this artery was the least common variation (1,06%) observed only in A1 segment. Bilateral absence of the PcoA was seen in 27.56% of the patients. Fenestration was more commonly detected in anterior communicating artery (AcoA) (10.12%), followed by MCA (1.06%), ACA (1,06%) and PCA (0.67%). Duplication was the least common variation which was detected in MCA, AcoA and PcoA. Conclusion: Arterial variations of the circle of Willis are not rare and can be non-invasively evaluated using CTA.
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