Configuration of the circle of Willis and its two parts among Egyptian: a magnetic resonance angiographic study

Abstract

Background: We hypothesized that the collateral circulation differs in different ethnic groups. So, the aim of our work was to study variations of the circle of Willis (COW) among Egyptian and to compare our findings with the findings of other nationalities. Materials and methods: One hundred patients were studied using magnetic resonance angiography (3D-TOF-MRA). Frequency and morphologic variations in COW were studied. The diameters of the arteries of the anterior and posterior circle were verified. Finally, the differences among the mean diameters of these arteries regarding age and sex were also studied. Results: Complete, partially complete and incomplete COW were encountered in 28%, 38% and 34% in the studied cases. The incomplete anterior circle was found in 34% (10% isolated incomplete anterior circle and 24% combined incomplete anterior and posterior circles) and the incomplete posterior circle came across in 62% (38% isolated incomplete posterior circle and 24% combined incomplete anterior and posterior circles). Seven anterior circle variations were found. The commonest type was the classical type "a" with a prevalence of 56%, being higher in male (57.1%). The 2 nd common type was type "g" (hypoplasia or aplasia of the anterior communicating artery) with a prevalence of 24%, being higher in male (66.7%). Six posterior circle variations were found. The commonest variation was the classic type "a" with a prevalence of 26%, being higher in male (61.5%). Posterior circles types "d, e, h" (18%, 24%, 20%) constituted 62% and were characterised by hypoplasia/absent of the posterior communicating arteries. Conclusions: The prevalence of complete COW (classic or textbook type) was encountered only 28% of the studied cases. Variations of COW were found to be more common in the posterior circulation (62%). The incomplete anterior circle was found in 34% and it is mostly caused by hypoplasia or aplasia of the anterior communicating artery which was found to be more common compared to the literature.

Circle of Willis: anatomical variations of configuration. A magnetic resonance angiography study

“…A "classical" configuration with a complete entire circle and "standard" configuration of distribution and size of the arteries contributing to the CoW was found in 30.9% of cases, which is within the range of most similar studies [23,25]. The most common variation from the classical aspect was identified as the unilateral absence of one of the posterior communicating arteries (22.2%) in the posterior CoW, while in the anterior circle, the second most common configuration after the classical pattern was the unilateral absence of the precommunicating segment of an anterior cerebral artery (13.5%).…”

“…Out of the 20 total possible configurations of the CoW, we identified only the first 8 for the anterior, and first 6 for the posterior circle, respectively. A scarcity of these unidentified variants was cited in other similar studies with comparable study lot size [25].…”

“…Studies on various world populations cite an incidence between 16.6 and 85.4% for the "classical" configuration of the CoW [12,21,[23][24][25]. Significant differences between populations of various races were noted, and genetic and environmental factors were considered as elements that may influence the development of the CoW [10,16,21,23,24].…”

Proportion of Variant Anatomy of the Circle of Willis and Association with Vascular Anomalies on Cerebral CT Angiography

“…A complete anterior CW was significantly higher in female than male patients (92.7% vs. 77.4%, p=0.04). The prevalence of complete anterior CW in this study was higher than an MRA-TOF study by Sherif Mohamed Zaki et al on 100 patents with no evidence of cerebrovascular disease which showed a prevalence of 66% [25]. The finding in our study was also higher than an MRA-TOF study by Shartri J et al on 513 adults without cerebrovascular disease which demonstrated a complete anterior CW in 64.3% [26].…”

Morphological aspects of the vasculogenesis and angiogenesis during prenatal edification of the circle of Willis: a review

“…Anatomical variants of CoW are more common in its posterior part [34,35], some authors reporting that almost two thirds of the brain they analyzed presented anatomical variations of the posterior circulation [36]. These anatomical variants can appear either in the form of unilateral or bilateral hypoplasia/atresia of the PComAs (Figures 4-9), and as unilateral or bilateral absence of the PComAs (Figure 8) or of the PCA, or as the fetal variant of the PComA (Figures 7, 8, and 10).…”