Variability of the Circle of Willis in North American Caucasian and Middle East Arabic Cohorts

The cerebral arterial circle (circle of Willis) plays an important role in the redistribution of the blood flow between the anterior and posterior territories and maintains the plasticity of the cerebral blood circulation. The anatomical variability of the vascular circle often alters the cerebral hemodynamics and determines the outcomes of acute and chronic cerebrovascular disease. The heritability and prevalence of certain variants of the circle of Willis in different ethnic and racial groups are frequently disputed by authors. Our cross-sectional retrospective study aims to compare the patterns of the cerebral arterial circle in 64 Caucasian cadavers with 64 Arabic living individuals, by methods of anatomic dissection and magnetic resonance angiography, respectively. The typical structure of the circle of Willis was revealed in 8.3% of the Caucasian study group, and in 22.2% of the Arabic one. The anterior part of the circle of Willis was incomplete in 6 out of 64 of the Caucasian specimens, where the anterior communicating artery was hypoplastic (6.3%) or absent (3.1%). The posterior part of the circle of Willis had hypoplastic or absent posterior communicating artery on one side in 20, and on both sides in 12 out of 64 Caucasian specimens. In the Arabic cohort, the posterior part of the circle of Willis was incomplete in 17 out of 64 specimens, with absence of the posterior communicating artery unilaterally (in 11 cases) or bilaterally (in 6 cases). The present study reveals that the configuration of the cerebral arterial circle and distribution of the blood flow between the anterior and posterior territories have certain differences in the Caucasian study group versus the Arabic one.