Anatomical Variants of Circle of Willisin South Indian Population: A Study by Using Magnetic Resonance Angiography

OBJECTIVES To evaluate and to describe the prevalence and pattern of circle of Willis (CoW) arterial variants (aplasia, hypoplasia) and anomalies {arteriovenous malformations (AVMs), and aneurysms} in non-contrasted three-dimensional time-of-flight MR angiography (3D-TOF-MRA) in general population. METHODOLOGYA cross sectional study was undertaken in the Department of Radiology of NarayanaHrudayalaya Institute of Medical Sciences, Bangalore. About 300 healthy participants (198 men, 102 women) during the study period constituted the study sample. RESULTSThe prevalence of complete configuration of the circle is 16.6 % and is slightly higher in females than males and younger (below 50 yrs) than older subjects. In the present study the complete anterior circle of Willis is common with 77.3 % of all the subjects. The commonest anterior circle variant is type A (normal anterior configuration) with a prevalence of 66 %. The most common posterior circle variant is type E (Hypoplasia or absence of both PcomAs and isolation of the anterior and posterior parts of the circle at this level) with 32.6 %. CONCLUSIONOverall, circle of Willis variants are slightly more common among the women in comparison to men. Incidences of associated anomalies, like aneurysm or AVM are comparable to that described in literature.