Circle of Willis Variations Detected by Time of Flight Magnetic Resonance Imaging Angiography in Eastern Anatolia Region

Objective: The purpose of the study was to determine variations in the circle of Willis in the Eastern Anatolia Region with TOF magnetic resonance imaging angiography. Methods: Two hundred fifty cases between the ages of 18 and 50, who applied to the department for cranial magnetic resonance angiography (MRA) examination and had no specific symptoms, were included in the study. Study data were obtained with 1.5 T and 3T MR (Magnetom Skyra; Siemens Healthcare, Erlangen, Germany) devices. Results: Typical polygonal structure was seen in 80 cases (32%) and arteria communicans anterior (AComA) aplasia was seen in 4 cases (1.62%). The incidence of right and left anterior cerebral artery (ACA) A1 aplasia and hypoplasia were 11 (4.4%), 5 (2%), 14 (5.5%), and 6 (2.4%), respectively. ACA trifurcation was detected in 19 (7.6%), azygos ACA in 2 (0.8%), and bi-hemispheric ACA in 4 (1.6%). Right and left arteria communicans posterior (AComP) aplasia and hypoplasia were detected in 42 (16.8%), 32 (12.8%), 25 (10%), and 26 (10.4%), respectively. Right arteria cerebri posterior (ACP) fetal configuration was determined in 26 (10.4%), left in 15 (6%), and bilateral in 16 (6.4%). Basilar artery fenestration and persistent trigeminal artery were detected in 3 cases (1.2%). Right and left vertebral artery hypoplasia was determined in 20 (8%) and 14 (5.6%) cases, respectively. Conclusion: The anatomical determination of the normal structure and variations of the Willis polygon with TOF MRA, which is a non-invasive imaging method that does not require radiation exposure and contrast material, revealed that the typical polygonal structure where all the arteries are located was detected at a rate of 32%. The most frequently detected variations were aplasia/hypoplasia, and they were seen most frequently in AComP (between 10% and 16.8%). The most frequently detected variation in anterior circulation was ACA trifurcation (7.6%), and it was similar to the literature.