Zulu et al., 2016 Anatomical Variations of the Circle of Willis as seen at the University Teaching Hospital, Lusaka

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Keywords: Circle of Willis, Anatomical Variations, Hypoplasia, Post-mortem


Background: The ideal distribution of blood to the brain and the collateral potential of the Circle of Willis (CW) is believed to be dependent largely on the morphology and the presence of all the component vessels of the CW. Several studies have shown that variations in the CW play an important role in the development of cerebrovascular diseases (CVD) such as cerebrovascular accidents or stroke, aneurysms and infarctions. Despite these CVDs being on the increase, no study on anatomical patterns or variations has been conducted in the local and sub-regional population. The study aimed to determine the anatomical variations of the CW as seen at the University Teaching Hospital, Zambia.

Methods: The study was undertaken to observe the morphology of the CW using gross dissection in 185 post mortem non pathological brains. A data collection form was used to capture information such as age, sex, external diameter of the posterior communicating arteries (PcoA) and aneurysms. Univariate and multivariate analysis was used to determine factors associated with hypoplasia of both left and right PcoA. Statistical analysis was performed with STATA version 12.

Results: This study showed that 90.3% of the brain specimen had complete circles. Hypoplasia (< 1mm diameter) was 30.3% and 36.2% in the right and left PcoA respectively. The proportion of males 149 (80.5%) were significantly higher (p < 0.0001) than females 36 (19.5%). The median age for individuals with hypoplasia (<1.0mm) of the right and left PcoA was 48 and 46 years respectively; the medians were statistically different (p < 0.0001). A significant association between age and hypoplasia of the PcoA was observed (p < 0.001).

Conclusion: The study revealed significant variations in the CW in the brain specimens studied at the University Teaching Hospital, Zambia. Hypoplasia in the PcoA was the most common noted variation with CW incompleteness in a few cases. No aneurysm was observed.