Increasing Occlusive Disease in the Circle of Willis Correlates with Worse Cognitive Function in Patients with High-grade Asymptomatic Carotid Stenosis

Our group has previously demonstrated that some patients with asymptomatic carotid artery stenosis (ACAS) demonstrate cognitive impairment, and that some patients with ACAS demonstrate cerebral hypoperfusion. Cerebral hypoperfusion from flow-limiting carotid stenosis in conjunction with inadequate cross-collateralization via the circle of Willis (CoW) may be the mechanism underlying these cognitive impairments. This study evaluates the relationship between abnormal (hypoplastic or absent) segments in the CoW and cognitive function in patients with high-grade (≥70%) ACAS. Twenty-three patients with high-grade ACAS were recruited and underwent carotid duplex ultrasound, cognitive function assessment, and magnetic resonance imaging, including three-dimensional time-of-flight magnetic resonance angiography of the intracranial circulation. The cognitive battery comprised nine neuropsychological tests assessing four cognitive domains: learning and memory, motor and processing speed, executive function, and attention and memory. Raw cognitive scores were converted into standardized t scores. The magnetic resonance angiography images were interpreted by a board-certified neuroradiologist. Imaging assessment included the vertebral and carotid circulation and each segment of the CoW, which was classified as normal, hypoplastic (stenosed), or absent (occluded). Linear regression was used to assess the association between abnormal (hypoplastic or absent) segments in the CoW and cognitive domain scores. Significance was set to a P value of <.05. The mean age of study patients was 66.4 ± 9.75 years and 78% were male. All 23 patients were found to have at least one CoW segment classified as abnormal. ACAS patients demonstrated a significant negative correlation between the number of abnormal segments in the CoW and cognitive performance in the domains of attention and memory (t = −2.4; P = .02), and learning and memory (t = −2.5; P = .02) (Figure). The cognitive scores for executive function and motor and processing speed also demonstrated a negative correlation but did not reach statistical significance (t = −1.9 [P = .07]; t = −0.9 [P = .36], respectively). Our data demonstrate that the presence of increasing occlusive disease in the COW correlates with worse cognitive function in patients with high-grade ACAS. This correlation was significant in the domains of attention/memory and learning/memory. These findings lend support to the hypothesis that cerebral hypoperfusion resulting from ACAS in the presence of a diseased CoW may underly cognitive impairments in patients with high-grade ACAS.