Correlation between the flow pattern of the circle of Willis and segmental perfusion asymmetry after carotid artery revascularization

Background: To correlate cerebral perfusion and flow patterns after carotid artery revascularization within the circle of Willis (CoW). Methods: Sixty-five patients (male/female ratio: 38/27; mean age: 63.2±8.4years; range: 44-82years) with symptomatic carotid artery stenosis underwent magnetic resonance (MR) angiography and perfusion imaging prior to and after carotid artery stenting (CAS). Regions of interest (ROIs) on the MR perfusion maps included the corona radiata (CR), centrum semiovale (CSO), occipital region (O), and basal ganglia region (BA) in both stented and non-stented hemispheres. The non-stented hemisphere was used as internal control. Results: Subjects were assigned to the altered CoW group (N=31) vs. the static CoW group (N=34). Thirty-one subjects (47.6%) had an altered flow pattern in the CoW after CAS, and thirty-four (52.4%) retained a static CoW configuration. Relative cerebral blood volume (rCBV) interhemispheric index correlated with CoW morphologic alterations after carotid stenting. Altered CoW group had a higher regional interhemispheric index of rCBV in the CR (1.23±0.15 vs. 0.87±0.13; P=0.03) and basal ganglia (1.25±0.12 vs. 0.91±0.11; P=0.03) compared to the static group. Conclusions: An association between the regional cerebral blood volume (rCBV) interhemispheric asymmetry and CoW collateralization was observed. In addition, the CR, rather than CSO, was found to have topographic significance.