Angiographic Analysis of the Circle of Willis: Comparison between Atherosclerosis and Normal Groups

ABSTRACT

PURPOSE: To determine differences in angiographic variations of the circle of Willis between atherosclerosis and normal groups. MATERIALS AND METHODS: In 289 patients we reviewed complete cerebral angiograms obtained using biplane digital subtraction angiography. Atherosclerosis was diagnosed in 189 patients, while 100 were normal. Patients were divided into four subgroups according to the relative size of each segment and the presence of cross-filling of opposite-sided vessels. When the circle was completely present, we determined whether or not it was balanced, and statistically compared variation patterns between the two groups. RESULTS: In the atherosclerosis group, the anterior half of the circle was complete in 74% of cases(139/189), and the posterior half in 38% (72/189). In the normal group, the anterior half was complete in 90% of cases, and the posterior half in 63%. An incomplete circle was more common in the atherosclerosis group than among normal subjects (26% vs 10%, p.05) and agenesis of the P1 segment (7% vs 3%, p>.05). CONCLUSION: An incomplete and unbalanced circle of Willis was more common in the atherosclerosis group than in the normal group. Agenesis of the anterior communicating artery, the A1 segment, or the posterior communicating artery was common in the atherosclerosis group, as was size discrepancy between A1 segments.