title: Quantitative measurement of cerebrovascular reactivity by blood oxygen level-dependent MR imaging in patients with intracranial stenosis: preoperative cerebrovascular reactivity predicts the effect of extracranial-intracranial bypass surgery.
abstract: OBJECTIVE
  CVR is a measure of cerebral hemodynamic impairment. A recently validated technique quantifies CVR by using a precise CO(2) vasodilatory stimulus and BOLD MR imaging. Our aim was to determine whether preoperative CO(2) BOLD CVR predicts the hemodynamic effect of ECIC bypass surgery in patients with intracranial steno-occlusive disease.
  
  
  METHODS
  Twenty-five patients undergoing ECIC bypass surgery for treatment of intracranial stenosis or occlusion were recruited. CVR was measured preoperatively and postoperatively and expressed as %ΔBOLD MR signal intensity per mm Hg ΔPetCO(2). Using normative data from healthy subjects, we stratified patients on the basis of preoperative CVR into 3 groups: normal CVR, reduced CVR, and negative (paradoxical) CVR. Wilcoxon 2-sample tests (2-sided, α = 0.05) were used to determine whether the 3 groups differed with respect to change in CVR following bypass surgery.
  
  
  RESULTS
  The group with normal preoperative CVR demonstrated no significant change in CVR following bypass surgery (mean, 0.22% ± 0.05% to 0.22% ± 0.01%; P = .881). The group with reduced preoperative CVR demonstrated a significant improvement following bypass surgery (mean, 0.08% ± 0.05% to 0.21 ± 0.08%; P < .001), and the group with paradoxical preoperative CVR demonstrated the greatest improvement (mean change, -0.04% ± 0.03% to 0.27% ± 0.03%; P = .028).
  
  
  CONCLUSIONS
  Preoperative measurement of CVR by using CO(2) BOLD MR imaging predicts the hemodynamic effect of ECIC bypass in patients with intracranial steno-occlusive disease. The technique is potentially useful for selecting patients for surgical revascularization.
authors: Division of Neuroradiology, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada.
authors: D M
authors: DM
authors: Mandell
authors: J S
authors: JS
authors: Han
authors: J
authors: J
authors: Poublanc
authors: A P
authors: AP
authors: Crawley
authors: J
authors: J
authors: Fierstra
authors: M
authors: M
authors: Tymianski
authors: J A
authors: JA
authors: Fisher
authors: D J
authors: DJ
authors: Mikulis
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000097:blood; D002548:Cerebral Revascularization; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002648:Child; D005260:Female; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D011237:Predictive Value of Tests; D011300:Preoperative Care / Q000379:methods; D016896:Treatment Outcome; D014664:Vasodilation / Q000502:physiology; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen