title: Transhemispheric passage of microemboli in patients with unilateral internal carotid artery occlusion.
abstract: OBJECTIVE
  Ischemic episodes distal to an internal carotid artery occlusion are common. We undertook this study to look for evidence of transhemispheric passage of embolic material in this patient category as a mechanism for embolic events.
  
  
  METHODS
  Seven symptomatic patients with unilateral internal carotid artery occlusion and contralateral stenosis were examined by transcranial Doppler ultrasonography with 2-MHz probe (average monitoring time, 2.5 hours per patient). Both middle cerebral arteries and (if present) the reverse-flow anterior cerebral artery ipsilateral to the occluded internal carotid were monitored. Three patients were reexamined 1 month after carotid endarterectomy.
  
  
  RESULTS
  Embolic signals were detected in the middle cerebral artery ipsilateral to the stenosed internal carotid artery in all seven patients and in the opposite middle cerebral artery in four patients. In these four patients, a reverse-flow anterior cerebral artery was observed in which embolic signals were detected. No embolic signals were detected after surgery in any of the three patients who underwent carotid endarterectomy.
  
  
  CONCLUSIONS
  Transhemispheric passage of embolic material occurs in patients with unilateral internal carotid artery occlusion and contralateral stenosis. Endarterectomy of the stenosed internal carotid artery may eliminate the detected embolic signals in both hemispheres. Transcranial Doppler ultrasonography could be used as a diagnostic tool to identify the embolic source in patients with unilateral carotid occlusion.
authors.affiliation: University Department of Medicine and Therapeutics, Western Infirmary, Glasgow, UK.
authors.forename: D
authors.initials: D
authors.lastname: Georgiadis
authors.forename: D G
authors.initials: DG
authors.lastname: Grosset
authors.forename: K R
authors.initials: KR
authors.lastname: Lees
mesh_terms: D000368:Aged; D001157:Arterial Occlusive Diseases / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D002340:Carotid Artery Diseases / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D002343:Carotid Artery, Internal; D005260:Female; D006801:Humans; D002542:Intracranial Embolism and Thrombosis / Q000150:complications* / Q000000981:diagnostic imaging*; D002546:Ischemic Attack, Transient / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D014463:Ultrasonography