title: Symptomatic and asymptomatic retinal embolism have different mechanisms.
abstract: OBJECTIVE
  To investigate differences between symptomatic and asymptomatic retinal embolism regarding the frequency and source of cerebral microemboli.
  
  
  METHODS
  Thirty-seven patients with transient monocular blindness or retinal infarction and 27 patients (29 eyes) with asymptomatic retinal embolism were prospectively enrolled. Patients underwent a transcranial Doppler study and noninvasive imaging of the cervical internal carotid arteries (ICA). The middle cerebral artery (MCA) ipsilateral to the affected eye was monitored for 30 minutes for microembolic signals (MES), which were saved and analyzed offline. Age-matched controls (n=15) had no history of retinal or brain ischemia, <50% ICA stenosis, and normal ophthalmologic examinations.
  
  
  RESULTS
  MES were detected in 0/15 (0%) controls, 11/37 (30%) MCAs in the symptomatic group (P=0.02), and 3/29 (10%) MCAs in the asymptomatic group (P=0.54). Nine of 11 (82%) symptomatic eyes with MES had ipsilateral ICA stenosis of > or =50%, as compared with 0/3 (0%) eyes in the asymptomatic group with MES (P=0.03). Both MES and ICA stenosis of >50% were present in 9/37 (24%) cases in the symptomatic and in 0/29 (0%) cases of the asymptomatic group (P=0.0036).
  
  
  CONCLUSIONS
  The frequency and potential source of cerebral microemboli in symptomatic and asymptomatic retinal embolism are different. Cerebral microemboli are more frequent in symptomatic patients and are associated with ICA stenosis.
authors.affiliation: Department of Neurology, Stanford University Medical Center, Palo Alto, Calif 94304-1705, USA. cwijman@stanford.edu
authors.forename: Christine A C
authors.initials: CA
authors.lastname: Wijman
authors.forename: Joao A
authors.initials: JA
authors.lastname: Gomes
authors.forename: Michael R
authors.initials: MR
authors.lastname: Winter
authors.forename: Behrooz
authors.initials: B
authors.lastname: Koleini
authors.forename: Ippolit C A
authors.initials: IC
authors.lastname: Matjucha
authors.forename: Val E
authors.initials: VE
authors.lastname: Pochay
authors.forename: Viken L
authors.initials: VL
authors.lastname: Babikian
mesh_terms: D000368:Aged; D020757:Amaurosis Fugax / Q000000981:diagnostic imaging*; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging; D016893:Carotid Stenosis / Q000000981:diagnostic imaging; D015331:Cohort Studies; D005260:Female; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000000981:diagnostic imaging*; D020766:Intracranial Embolism / Q000175:diagnosis / Q000000981:diagnostic imaging*; D008297:Male; D015356:Retinal Artery Occlusion / Q000000981:diagnostic imaging*; D017585:Ultrasonography, Doppler, Transcranial