Types of the cerebral arterial circle (circle of Willis) in a Sri Lankan Population

Abstract

BackgroundThe variations of the circle of Willis (CW) are clinically important as patients with effective collateral circulations have a lower risk of transient ischemic attack and stroke than those with ineffective collaterals. The aim of the present cadaveric study was to investigate the anatomical variations of the CW and to compare the frequency of prevalence of the different variations with previous autopsy studies as variations in the anatomy of the CW as a whole have not been studied in the Indian subcontinent.MethodsThe external diameter of all the arteries forming the CW in 225 normal Sri Lankan adult cadaver brains was measured using a calibrated grid to determine the prevalence in the variation in CW. Chisquared tests and a correspondence analysis were performed to compare the relative frequencies of prevalence of anatomical variations in the CW across 6 studies of diverse ethnic populations.ResultsWe report 15 types of variations of CW out of 22 types previously described and one additional type: hypoplastic precommunicating part of the anterior cerebral arteries (A1) and contralateral posterior communicating arteries (PcoA) 5(2%). Statistically significant differences (p < 0.0001) were found between most of the studies except for the Moroccan study. An especially notable difference was observed in the following 4 configurations: 1) hypoplastic precommunicating part of the posterior cerebral arteries (P1), and contralateral A1, 2) hypoplastic PcoA and contralateral P1, 3) hypoplastic PcoA, anterior communicating artery (AcoA) and contralateral P1, 4) bilateral hypoplastic P1s and AcoA in a Caucasian dominant study by Fisher versus the rest of the studies.ConclusionThe present study reveals that there are significant variations in the CW among intra and inter ethnic groups (Caucasian, African and Asian: Iran and Sri Lanka dominant populations), and warrants further studies keeping the methods of measurements, data assessment, and the definitions of hypoplasia the same.

Configurations of the circle of Willis: a computed tomography angiography based study on a Polish population

“…The prevalence of the typical pattern of the CW has been reported to range from 14.00% to 45.20% in cadaveric examinations [4,11], in contrast to imaging studies where it has been observed in 22.29% to 45.76% [6,9] of the subjects. As shown in Table 5, the entire circle was reported to be open rather rarely -in 3.20% to 11.00% of the subjects [5,11].…”

“…Many authors have hypothesised that there are considerable differences in the prevalence of various configurations of the CW in various ethnic groups [4,11,13]. Conclusions based on the comparison of data acquired using different methods seem to be questionable.…”

“…Cadaveric examinations have yielded a range of inconsistent results [4,5,11] that do not correspond with imaging studies. The prevalence of the typical pattern of the CW has been reported to range from 14.00% to 45.20% in cadaveric examinations [4,11], in contrast to imaging studies where it has been observed in 22.29% to 45.76% [6,9] of the subjects.…”

“…Many factors play a role in the development of the structures of the CW, including one's genetic background, the haemodynamic and environmental conditions of prenatal and postnatal growth, the development of the brain, and contingent co-morbidities [1,11,17,18]. As such, it is rather unsurprising that there is a large variety of configurations of the CW among both healthy and unhealthy populations of different ethnic groups [4,11].…”

“…Cadaveric studies are still widely performed [4,5,11,15] and several imaging methods, including transcranial colour-coded duplex ultrasonography (TCCD) [9], 3-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) [2,3,14], and computed tomography angiography (CTA) [2,7,13,16] have been used to examine the circle. These imaging techniques have allowed for the precise depiction of the clinically relevant collaterals of the circle by assessing the patency of blood vessels that determine the circle's physiological completeness.…”