title: Cerebral microembolism and the risk of ischemia in asymptomatic high-grade internal carotid artery stenosis.
abstract: OBJECTIVE
  Previous work has shown that cerebral microembolism 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.
  
  
  METHODS
  Sixty-four asymptomatic patients with unilateral 70% to 90% internal carotid artery stenosis were investigated prospectively (mean follow-up, 72 weeks). Five patients developed ischemic symptoms attributable to the stenosis (transient ischemic attack, 2 patients; stroke, 3 patients). A microembolic rate of > or = 2 per hour in the ipsilateral middle cerebral artery 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 transcranial Doppler sonography may define a high-risk subgroup among patients with asymptomatic high-grade internal carotid artery stenosis.
mesh_terms: D000368:Aged; D002545:Brain Ischemia / Q000209:etiology* / Q000503:physiopathology; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging / Q000473:pathology; D016893:Carotid Stenosis / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D006801:Humans; D002542:Intracranial Embolism and Thrombosis / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D018608:Ultrasonography, Doppler