title: MR diffusion-weighted imaging and outcome prediction after ischemic stroke.
abstract: BACKGROUND
  MR diffusion-weighted imaging (DWI) shows acute ischemic lesions early after stroke so it might improve outcome prediction and reduce sample sizes in stroke treatment trials. Previous studies of DWI and outcome produced conflicting results.
  
  
  OBJECTIVE
  To determine whether DWI lesion characteristics independently predict outcome in a broad range of patients with acute stroke.
  
  
  METHODS
  The authors recruited hospital-admitted patients with all severities of suspected stroke, assessed stroke severity on the NIH Stroke Scale (NIHSS), performed early brain DWI, and assessed outcome at 3 months (modified Rankin Scale). Clinical data and DWI lesion parameters were evaluated in a logistic regression model to identify independent predictors of outcome at 3 months and a previously described "Three-Item Scale" (including DWI) was tested for outcome prediction.
  
  
  RESULTS
  Among 82 patients (mean NIHSS 7.1 [+/-6.3 SD]), the only independent outcome predictors were age and stroke severity. Neither DWI lesion volume nor apparent diffusion coefficient nor the previously described Three-Item Scale predicted outcome independently. Comparison with previous studies suggested that DWI may predict outcome only in patients with more severe cortical ischemic strokes.
  
  
  CONCLUSIONS
  Across a broad range of stroke severities, diffusion-weighted imaging (DWI) did not predict outcome beyond that of key clinical variables. Thus, DWI is unlikely to reduce sample sizes in acute stroke trials assessing functional outcome, especially where estimated treatment effects are modest.
authors.affiliation: Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Hand
authors.forename: J M
authors.initials: JM
authors.lastname: Wardlaw
authors.forename: C S
authors.initials: CS
authors.lastname: Rivers
authors.forename: P A
authors.initials: PA
authors.lastname: Armitage
authors.forename: M E
authors.initials: ME
authors.lastname: Bastin
authors.forename: R I
authors.initials: RI
authors.lastname: Lindley
authors.forename: M S
authors.initials: MS
authors.lastname: Dennis
mesh_terms: D000208:Acute Disease; D000368:Aged; D002545:Brain Ischemia / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology; D003955:Diagnostic Tests, Routine / Q000706:statistics & numerical data; D038524:Diffusion Magnetic Resonance Imaging / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D020521:Stroke / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology; D016896:Treatment Outcome