title: Cerebrovascular reserve in patients with carotid occlusive disease assessed by stable xenon-enhanced ct cerebral blood flow and transcranial Doppler.
abstract: OBJECTIVE
  Cerebrovascular reserve (CVR) by both transcranial Doppler ultrasonography (TCD) and quantitative cerebral blood flow (CBF) can identify subgroups of patients at increased risk for stroke. A direct comparison of CVR measurements obtained with both technologies in patients with cerebrovascular occlusive disease is lacking.
  
  
  METHODS
  CVRs before and after acetazolamide administration (1 g IV) were measured by TCD insonation of the middle cerebral artery (MCA) and CBF obtained with stable xenon CT (Xe/CT) in 38 patients with carotid occlusive disease. Sensitivity/specificity calculations were based on 2 Xe/CT MCA values: an average over 4 levels and the level with the lowest percent change in CBF. Compromised CVR was defined as no reactivity or a decrease in reactivity.
  
  
  RESULTS
  Using the analysis of the systolic TCD, we found that velocity changes compared with the average Xe/CT MCA CVR showed a sensitivity of 33%, specificity of 90.6%, positive predictive value of 54.5%, and negative predictive value of 80%. The sensitivity of TCD compared with the lowest Xe/CT CBF CVR was 35.5%, specificity and positive predictive values were 100%, and negative predictive value was 66.7%. The index of validity was between 72% and 76%.
  
  
  CONCLUSIONS
  TCD is much less sensitive than Xe/CT CBF in identifying patients with compromised CVR. This may be a result of the inability of TCD to identify patients with compromised reserves when their MCA blood flow comes from collateral sources. The lack of correlation between TCD and Xe/CT CBF for identifying patients with compromised CVR should be considered when stroke risk assessments are made by TCD.
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA. pindzola@neuronet.pitt.edu
authors.forename: R R
authors.initials: RR
authors.lastname: Pindzola
authors.forename: J R
authors.initials: JR
authors.lastname: Balzer
authors.forename: E M
authors.initials: EM
authors.lastname: Nemoto
authors.forename: S
authors.initials: S
authors.lastname: Goldstein
authors.forename: H
authors.initials: H
authors.lastname: Yonas
mesh_terms: D000086:Acetazolamide; D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging / Q000503:physiopathology; D002340:Carotid Artery Diseases / Q000175:diagnosis* / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods; D017585:Ultrasonography, Doppler, Transcranial; D014665:Vasodilator Agents; D014978:Xenon
chemical_list: D014665:Vasodilator Agents; D014978:Xenon; D000086:Acetazolamide