Magnetic Resonance Angiographic Study of Anatomic Variations of the Circle of Willis in a Population in Tehran

The circle of Willis, an anastomotic polygon at the base of the brain, forms an important collateral network to maintain cerebral blood perfusion. The aim of this study was to investigate different anatomic variations of the circle of Willis and their prevalence.
This cross-sectional study was conducted on 525 healthy participants including 205 men and 320 women. The mean age of the patients was 51.5 years. Three-dimensional time-of-flight magnetic resonance angiography (3D-TOF MRA) technique was used. Vascular variations in the anterior and posterior parts of the circle were evaluated.
The findings show that the complete circle of Willis was visible in a small number of patients. The circle of Willis had a complete vascular structure in 20.9% of the patients. The anterior part of the circle of Willis had a complete structure in 80.95% of the cases, while the posterior part had a complete structure in 20.95% of the cases.
We observed wide variations in the circle of Willis configuration in our study. Similar to other studies, most variations are related to the posterior part of the circle of Willis. Absence of bilateral posterior communicating artery variation is more common than other types of variations in this population.