Prevalence of Anatomical Variants of the Circle of Willis

Abstract

The Circle of Willis is an anastomotic structure that connects the anterior and posterior arterial networks that supply blood to the brain. It functions to maintain adequate blood supply to the brain in the event of obstruction due to injury or disease. Although it is well‐known that variants in the “textbook” structure of the Circle of Willis are common, previous studies characterizing the CoW have been limited by small sample sizes and, in some cases, reliance on cadaveric tissue in which preservation of delicate CoW structures is challenging. These shortfalls have made investigating the relationships between variants and neurological pathology difficult. Therefore, the purpose of the present study was to characterize the CoW in a large sample of living subjects to determine the prevalence of CoW variants and to identify relationships between variants and pathology. After approval for this study was obtained from the AdventHealth IRB, computed tomography angiography (CTA) scans of 1,494 cases were assessed for CoW variants and all CoW vessels measured. Inclusion criteria included patients aged 18–89 that received CTA imaging through AdventHealth Radiology between 11/15/12 and 11/14/17. One examiner assessed all CTA images via imaging software (Impax) for variants. Six other investigators measured each of the CoW vessels on the selected cases. Patient demographic information was collected via AdventHealth's medical record system. Our results indicate that CoW variants were present in 47.99% of the subjects. Of the cases with variants, 8.93% possessed symmetrical bilateral variations and 39.05% possessed multiple variants. The most commonly occurring variant was a non‐dominant vertebral artery at 17.27%. Of the non‐diminutive variants, meaning there were additions to or subtractions from the standard CoW architecture, the most commonly occurring variant was fetal origin posterior cerebral artery at 12.38%. Our results suggest that anatomical variants found in the Circle of Willis occur in just over under half of the population. Future analyses will characterize vessel diameters for the cases under study and relationships of each of the variants to neurological pathology. This study demonstrates the need for further investigation into the nature of altered CoW circulation patterns, how CoW variants may relate to brain function and pathology, and whether diminutive variants can be altered by non‐invasive interventions.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.