Introduction The effectiveness of a scoring system based on the circle of Willis for evaluations of collateral circulation was studied in patients with intracranial atherosclerotic stenosis.

Methods Eighty-three patients who underwent medical or endovascular treatment for symptomatic and severe intracranial atherosclerotic stenosis were enrolled in the study. Clinical profiles, status of the circle of Willis (poor and good integrity group), and clinical outcomes were analyzed. Primary endpoints were: (1) symptomatic ischemic or hemorrhagic stroke within 30 days; and (2) recurrent transient ischemic attack or ischemic stroke beyond 30 days.

Results The estimated rates of the primary endpoint at 1 and 2 years after treatment were 8.5% and 11.4% in the medical group and 7.0% and 9.7% in the endovascular group, respectively. A primary endpoint event after medical treatment was only identified in patients with poor integrity of the circle of Willis (p=0.059). In patients with poor integrity of the circle of Willis, previous antiplatelet medication before initial presentation (p=0.026) and hypertension (p=0.006) were more prevalent. During the follow-up period, complete arterial occlusion was identified in 9 patients. The circle of Willis score of the patients with complete arterial occlusion was 1.33±1.52 in the fatal stroke group (n=3) and 3.20±1.64 in the asymptomatic group (n=6, p=0.099).

Conclusions If patients have poor integrity of the circle of Willis, the risk of recurrent stroke may be increased. Such patients appear to be good candidates for endovascular treatment.