Cerebrovascular Reserve may be a More Accurate Predictor of Stroke than Degree of ICA or MCA Stenosis

BACKGROUND: It is currently unclear whether the degree of stenosis or the cerebrovascular reserve (CVR) is a better predictor of ischemic stroke. MATERIAL/METHODS: In this study, CVR was measured by perfusion computed tomography with inhalation of 5% CO(2) in 37 symptomatic patients with internal carotid artery (ICA) or middle cerebral artery (MCA) stenosis or occlusion. Patients were divided into groups according to the degree of stenosis: ≥70% stenosis (stenosis group 1) or <70% stenosis (stenosis group 2); and according to CVR: ≥10% CVR (CVR group 1) or <10% CVR (CVR group 2). All patients were given medical treatment. RESULTS: During a mean follow-up period of 56.9 months (range 24–73 months), recurrent ipsilateral ischemic stroke occurred in 7 patients. Ischemic stroke occurred in 0 of 19 patients in CVR group 1 (annual risk 0%), 7 of 18 patients in CVR group 2 (annual risk 7.7%), 3 of 18 patients in stenosis group 1 (annual risk 3.3%), and 4 of 19 patients in stenosis group 2 (annual risk 4.7%). Comparisons using Pearson’s chi-square test showed a significant difference in the rate of ischemic stroke between CVR group 1 and CVR group 2 (odds ratio 1.700; 95% confidence interval 1.142–2.530; P=0.003), but no significant difference between stenosis group 1 and stenosis group 2 (P=0.691). CONCLUSIONS: Cerebrovascular reserve may be a more accurate predictor of stroke than degree of ICA or MCA stenosis.