title: Persistent infarct hyperintensity on diffusion-weighted imaging late after stroke indicates heterogeneous, delayed, infarct evolution.
abstract: OBJECTIVE
  Some infarcts have persistently hyperintense areas on diffusion-weighted MRI (DWI) even at 1 month after stroke, whereas others have become isointense to normal brain. We hypothesized that late DWI hyperintensity reflected different infarct evolution compared with areas that were isointense by 1 month.
  
  
  METHODS
  We recruited patients prospectively with ischemic stroke, performed DWI and perfusion-weighted MRI (PWI) on admission, at 5 days, 14 days, and 1 month after stroke, and assessed functional outcome at 3 months (Rankin Scale). Patient characteristics and DWI/PWI values were compared for patients with or without "still hyperintense" infarct areas on 1-month DWI.
  
  
  RESULTS
  Among 42 patients, 27 (64%) had "still hyperintense" infarct regions at 1 month, mostly in white matter. Patients with "still hyperintense" regions at 1 month had lower baseline apparent diffusion coefficient ratio (ADCr; mean+/-SD 0.76+/-0.12 versus 0.85+/-0.12; hyperintense versus isointense; P<0.05), prolonged reduction of ADCr (repeated-measures ANOVA; P<0.01), no difference in baseline perfusion but delayed normalization of mean transit time (P<0.05) and cerebral blood flow ratios (repeated measures ANOVA; P<0.05), initially more severe stroke, and worse 3-month outcome than patients whose lesions were isointense by 1 month.
  
  
  CONCLUSIONS
  The late DWI lesion hyperintensity emphasizes the heterogeneity in temporal evolution of stroke injury and suggests ongoing "ischemia." Lower baseline ADCr precedes delayed perfusion normalization, suggesting that worse cell swelling impedes reperfusion. Further study is required to determine underlying mechanisms and any potential for subacute intervention to improve recovery.
authors.affiliation: Division of Clinical Neurosciences, Western General Hospital, Edinburgh, UK.
authors.forename: Carly S
authors.initials: CS
authors.lastname: Rivers
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Wardlaw
authors.forename: Paul A
authors.initials: PA
authors.lastname: Armitage
authors.forename: Mark E
authors.initials: ME
authors.lastname: Bastin
authors.forename: Trevor K
authors.initials: TK
authors.lastname: Carpenter
authors.forename: Vera
authors.initials: V
authors.lastname: Cvoro
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hand
authors.forename: Martin S
authors.initials: MS
authors.lastname: Dennis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D002544:Cerebral Infarction / Q000175:diagnosis*; D002560:Cerebrovascular Circulation; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020521:Stroke / Q000175:diagnosis* / Q000503:physiopathology; D013997:Time Factors