Variants of the circle of Willis in ischemic stroke patients.

PURPOSE We aim to provide prevalence and pattern of anatomical variants of circle of Willis in over one thousand ischemic stroke patients compared to an age- and sex-matched control group, and to determine their role in the severity and in-hospital prognosis. METHODS Two groups of neuroradiologists evaluated all vascular images of ischemic stroke patients and controls to identify anatomical variants using a preexisted classification. We collected data concerning patient characteristics, stroke severity on admission and discharge, in-hospital mortality, hemorrhagic transformation, acute treatment performed, and etiology. RESULTS We included 1131 patients with acute ischemic stroke and 562 controls. Among stroke patients, 702 (62.1%) had one or more vascular variants, compared to 308 (54.8%) of the control group (p < 0.01), 165/702 (23.5%) had an anterior circulation variant only, 384/702 (54.7%) had a posterior circulation variant only, and 153/702 (21.8%) patients had variants in both anterior and posterior circulation. Patients with variants were older (69.7 ± 13.9 years vs 72.0 ± 12.9 years; p = 0.039). The most prevalent variant was the agenesis/hypoplasia of the ACA (201/1131; 17.8%) followed by the unilateral fetal type of the PCA (137/1131; 12.11%). CONCLUSIONS We provided the prevalence and the pattern of the brain vascular variants of the circle of Willis in a cohort of patients with ischemic stroke. The prevalence of variants was higher in stroke patients compared to controls. Patients with variants were older but had no differences in sex, neurological admission severity, hemorrhagic transformation, etiology, and in-hospital outcome compared to patients with a typical circle of Willis.