Evaluation of Anatomical Variants of the Circle of Willis in a Nigerian Population Using Contrast Enhanced Computed Tomography (CECT) Scan.

Abstract

Observations from different races have demonstrated the importance of variants of the major arterial supply to the brain, these are lacking in the Nigerian population. This anatomic-imaging study was carried out to identify, evaluate and document the distributions of variants of the Willis’ circle using Contrast Enhanced Computed Tomography (CECT) scan. A retrospective and prospective study was conducted on 512 apparently normal brain CT images consisting of 286 (55.86%) males and 226 (44.14%) females with a Bright speed 4-slice CT scanner in the Radiology Department of a Nigerian healthcare institution. The images were reviewed using proportionate random sampling probability technique. Data collected showed that 39.84% had complete circle of Willis while the rest (60.16%) had wide morphological variants. These include absence of bilateral Posterior Communicating Artery (PCoA) (39.26%), presence of double Anterior Communicating Artery (ACoA) (1.56%), absence of one A1 segment (1.37%), absence of ACoA (5.47%), absence of P1 segment and PCoA (5.08%) and the absence of unilateral PCoA (7.42%). The distribution of the variants was gender dependent at p<0.001 but age group dependent at p<0.05, as a significant correlation exist between gender and age groups at p<0.05 and p<0.01 in relation to the variants noted. The CECT scan method has established for the first time the occurrence and availability of morphological variants of the Willis’ circle in a Nigerian population with 39.84% complete circle and 39.26% bilateral absence of PCoA observed as the most common while 1.37% absence of one A1 segment was the least among other variants noted.