title: Detection of clinically silent intracranial emboli ipsilateral to internal carotid occlusions during cerebral angiography.
abstract: OBJECTIVE
  Embolic ischemic events have long been suspected to occur in the cerebral arteries distal to an ipsilateral occluded internal carotid artery (ICA). Documentation of microemboli by transcranial Doppler sonography during catheter angiography in patients with ICA occlusions provides objective evidence of such distal emboli.
  
  
  METHODS
  Seven patients undergoing carotid angiography were evaluated with transcranial Doppler sonography. Patients were also screened for ICA occlusions using carotid duplex sonography. In the seven patients, we saw five right ICA occlusions and two left ICA occlusions. Real-time visual and auditory confirmations of emboli were obtained by recognizing their specific spectral signatures and harmonic qualities. Routes of collateral flow were determined from angiography. Specific phases of the examination were correlated with embolic occurrences.
  
  
  RESULTS
  Overall, emboli were seen during all phases of arteriography. In the individual patients, emboli were identified in one to four of the eight angiographic phases we defined. Most emboli occurred during catheter flushing and contrast injection rather than during wire and catheter manipulation. The emboli were detected in the middle cerebral artery distribution ipsilateral to the occluded ICA in all seven patients. Collateral flow patterns included, in four patients, external carotid artery-to-ICA collateral flow; in all seven patients, patent anterior communicating arteries; and in three patients, patent posterior communicating arteries.
  
  
  CONCLUSIONS
  Emboli seen in middle cerebral arteries ipsilateral to occluded ICAs during cerebral angiography strongly indicate that emboli can occur distal to an occlusion. Our findings support the thought that emboli arising from sources proximal to an occluded ICA may reach the hemisphere distal to the occlusion, resulting in parenchymal ischemia or infarction.
authors.affiliation: Department of Radiology, The Cleveland Clinic Foundation, OH 44195, USA.
authors.forename: A
authors.initials: A
authors.lastname: Dagirmanjian
authors.forename: D A
authors.initials: DA
authors.lastname: Davis
authors.forename: W E
authors.initials: WE
authors.lastname: Rothfus
authors.forename: A L
authors.initials: AL
authors.lastname: Goldberg
authors.forename: Z L
authors.initials: ZL
authors.lastname: Deeb
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002341:Carotid Artery Thrombosis / Q000150:complications* / Q000000981:diagnostic imaging*; D002343:Carotid Artery, Internal; D002533:Cerebral Angiography; D006801:Humans; D020766:Intracranial Embolism / Q000000981:diagnostic imaging* / Q000209:etiology*; D008875:Middle Aged; D017585:Ultrasonography, Doppler, Transcranial