Variations in the Anatomy of the Willis′ circle: A 3-year cross-sectional study from Iran (2006-2009). Are the distributions of variations of circle of Willis different in different populations? Result of an anatomical study and review of literature

Abstract

Background:It is not well known whether the distributions of variations of circle of Willis (CW) are different in different populations. Previous studies have indicated: (a) The variations of the structure of the CW in different populations and ethnic and (b) some correlation between those congenital anatomical variations and possible cerebrovascular diseases. The frequency of such anatomical variations has not been evaluated sufficiently in the Iranian population. The aim of this study is to find the variations of the anatomy of the vessels in the CW in sample population of Iranian people and compare it with other available studies in the literature, providing a new grouping for variations.Methods:Samples were obtained from 200 autopsies in different ages, all retrieved in the department of Forensic Medicine, Tehran university of Medical Sciences after achieving permission from the Department of Ethics and Medico-legal Sciences. The CW was examined directly, using magnification, at the base of the brain. The cerebral vessels were observed for their configuration and their calibers were measured directly. Variations were noted and grouped into different categories.Results:Out of the 200 specimens examined, 69 (34.5%) were compatible with the typical anatomy of the CW. In the remaining 65.5% of the specimens, there were variations in the CW. Hypoplasia of the posterior communicating arteries was the most common variation in our study. One of the autopsies showed the presence of an aneurysm (0.5%).Conclusion:The anatomical variations found in our study were not significantly different from those reported in the literature. Based on the available data; (a) there is no evidence that the distribution of the variations of the anatomy of the CW is different in various societies and (b) the prevalence of the congenital aneurysmal changes in this region is not low in the Iranian population.

Normal Variants of the Circle of Willis in patients undergoing CT Angiography

“…In the remaining 65.5%, there were variations in the Circle of Willis. 9 In contrast, in a study by Klimek-Piotrowska et al 10 in 250 subjects, the prevalence of a normal Circle of Willis constituted only a minority of cases in a healthy population (16.80%). In an autopsy study of the human brain by Sinha et al 11 in India, 62 out of total 80 specimens (77.5%), the classic form of Circle of Willis that was complete, symmetrical and…”

A review of the diagnosis and management of vertebral basilar (posterior) circulation disease

“…Sixty-five percent of the people have abnormalities or anomalies in their Circle of Willis and 18–32% have one hypoplastic and 24–49% have bilateral hypoplastic posterior communicating arteries. [ 71 ] The anatomy of the brainstem vessels has been reviewed by others. [ 80 ] Those authors describe the anatomical clinical correlation in the vascular anatomy of the brainstem and related perforating branches.…”

“…The sample of the universe of patients with PCD in their Registry, included 63% males, 37% females, with an average age of 60 years; 84% were white, 9.5% Asian, 4% Black, and 2% Hispanic. [ 30 ] Fifty-nine percent (240 patients) had stroke without TIAs, 1%[ 30 ] had strokes followed by TIAs, 16%[ 30 ] had only TIAs, and 24%[ 71 ] TIAs before stroke. “The most likely stroke mechanism was decided by consensus.”[ 34 ] This group of patients is obviously not a representative sample of the USA population.…”

“…Thus, the anatomical connection between the AC and PC is impaired in half of the patients presenting with PCD. [ 71 ]…”

Experimental Study of Hemodynamics in the Circle of Willis

“…Unfortunately, congenital incompleteness of CoW, such as the lack of anterior communicating artery, unilateral or bilateral PCoA, is found in 50%-60% of the population [5][6][7]. Other anatomical variations, including fused vessels, string-like vessels and the presence of extra vessels, are also not uncommon ( Figure 1) [8].…”