Department of Anatomy, University of Sri Jayewardenepura, Nugegoda, Sri Lanka.
BMC Neurol. 2011 Jan 17;11:5. doi: 10.1186/1471-2377-11-5.
The 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.
The 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.
We 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.
The 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.
Willis 环（CW）的变异在临床上很重要，因为有效的侧支循环患者发生短暂性脑缺血发作和中风的风险低于无效侧支循环患者。本尸体研究的目的是研究 CW 的解剖变异，并比较不同变异的发生率与之前的尸检研究，因为整个 CW 的解剖变异在印度次大陆尚未得到研究。
使用校准网格测量形成 CW 的所有动脉的外径，以确定 CW 变异的流行程度。进行卡方检验和对应分析，以比较来自不同种族人群的 6 项研究中 CW 解剖变异的相对流行频率。
我们报告了 15 种 CW 变异类型，其中包括之前描述的 22 种类型和一种额外类型：前交通动脉（A1）和对侧后交通动脉（PcoA）发育不良的预交通部分 5（2%）。除了摩洛哥研究外，大多数研究之间都存在统计学显著差异（p < 0.0001）。观察到以下 4 种构型存在特别显著的差异：1）发育不良的后交通动脉（P1）和对侧 A1的预交通部分，2）发育不良的 PcoA 和对侧 P1，3）发育不良的 PcoA、前交通动脉（AcoA）和对侧 P1，4）双侧发育不良的 P1s 和 AcoA在以白种人为主的 Fisher 研究与其他研究之间。
本研究表明，CW 在种族内和种族间（白种人、非洲人和亚洲人：伊朗和斯里兰卡为主的人群）存在显著变异，需要进一步研究，同时保持测量方法、数据评估和发育不良的定义相同。
