CEREBRAL MICROEMBOLISM AND THE RISK OF ISCHEMIA IN ASYMPTOMATIC HIGH-GRADE INTERNAL CAROTID-ARTERY STENOSIS

Background and Purpose Previous work has shown that cerebral microembo lism detected with transcranial Doppler sonography distal to internal carotid artery stenosis occurs more frequently in recently symptomatic compared with asymptomatic patients. It has remained unclear whether cerebral microembolism also indicates a higher risk of future cerebral or retinal ischemia. Summary of Report Sixty-four asymptomatic patien ts with unilateral 70% to 90% internal carotid artery stenosis were in vestigated prospectively (mean follow-up, 72 weeks). Five patients dev eloped ischemic symptoms attributable to the stenosis (transient ische mic attack, 2 patients; stroke, 3 patients). A microembolic rate of gr eater than or equal to 2 per hour in the ipsilateral middle cerebral a rtery was associated with a substantially increased risk of developing ischemia of the corresponding carotid territory (odds ratio, 31; 95% confidence interval, 3 to 302; P = .005). Conclusions This prospective pilot study suggests that cerebral microembolism detected with transc ranial Doppler sonography may define a high-risk subgroup among patien ts with asymptomatic high-grade internal carotid artery stenosis.