title: Early identification of brain tissue at risk for delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.
abstract: BACKGROUND
  Delayed cerebral ischemia (DCI) continues to be a major cause of morbidity and mortality in patients with aneurysmal subarachnoid hemorrhage (aSAH) because it can only be diagnosed after the onset of clinical symptoms, contributing to poor clinical outcomes and huge use of clinical resources. We hypothesized that early disturbances in cerebrovascular reactivity, noninvasively measured with functional MRI + CO₂, can be a sensitive marker of brain tissue at risk for DCI.
  
  
  METHODS
  Functional MRI exam as soon as possible after the initial bleed and after surgical treatment of the aneurysm was performed in five patients. The functional MRI exam consisted of spatial cerebrovascular reactivity measurements by the blood oxygenation level-dependent (BOLD) response to a standardized carbon dioxide challenge.
  
  
  RESULTS
  Of the three patients who later developed DCI, two had abnormal functional MRI study results. The two patients without DCI had normal MRI results. Brain areas with impaired cerebrovascular reactivity on the functional MRI examination demonstrated a spatial correspondence between impaired cerebrovascular reactivity and the onset of DCI.
  
  
  CONCLUSIONS
  In this feasibility study, functional MRI measurements of cerebrovascular reactivity showed a spatial correspondence between impaired cerebrovascular reactivity and the onset of DCI in patients with aSAH.
authors.affiliation: Division of Neurosurgery, Department of Surgery, Sunnybrook Hospital, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Room A1-37, Toronto, ON, Canada, leo.dacosta@sunnybrook.ca.
authors.forename: Leodante
authors.initials: L
authors.lastname: da Costa
authors.forename: Joseph
authors.initials: J
authors.lastname: Fisher
authors.forename: David J
authors.initials: DJ
authors.lastname: Mikulis
authors.forename: Michael
authors.initials: M
authors.lastname: Tymianski
authors.forename: Jorn
authors.initials: J
authors.lastname: Fierstra
mesh_terms: D000328:Adult; D002545:Brain Ischemia / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000097:blood; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011237:Predictive Value of Tests; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*
chemical_list: D002245:Carbon Dioxide