title: Relationship between severity of MR perfusion deficit and DWI lesion evolution.
abstract: OBJECTIVE
  To assess whether a quantitative analysis of the severity of the early perfusion deficit on MRI in acute ischemic stroke predicts the evolution of the perfusion/diffusion mismatch and to determine thresholds of hypoperfusion that can distinguish between critical and noncritical hypoperfusion.
  
  
  METHODS
  Patients with acute ischemic stroke were studied in whom perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI MRI) were performed within 7 hours of symptom onset and again after 4 to 7 days. Patients with early important decreases in points on the NIH Stroke Scale were excluded. Maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were created. These hemodynamic parameters were correlated with the degree of recruitment of the baseline PWI lesion by the DWI lesion.
  
  
  RESULTS
  Twelve patients had an initial PWI > DWI mismatch of >20%. A linear relationship was observed between the initial MTT and the degree of recruitment of the baseline PWI lesion by the DWI lesion at follow-up (R(2) = 0.9, p < 0.001). Higher CBV values were associated with higher degrees of recruitment (rho = 0.732, p < 0.007). The volume of MTT of >4 (R(2) = 0.86, p < 0.001) or >6 seconds (R(2) = 0.85, p < 0.001) predicted final infarct size.
  
  
  CONCLUSIONS
  Among patients who have had an acute stroke with PWI > DWI, who do not have dramatic early clinical improvement, the degree of expansion of the initial DWI lesion correlates with the severity of the initial perfusion deficit as measured by the mean transit time and the cerebral blood volume.
authors.affiliation: Stanford Stroke Center, Department of Neurology and Neurological Sciences, Stanford University Medical Center, Palo Alto, CA, USA. vincent.thijs@uz.kuleuven.ac.be
authors.forename: V N
authors.initials: VN
authors.lastname: Thijs
authors.forename: A
authors.initials: A
authors.lastname: Adami
authors.forename: T
authors.initials: T
authors.lastname: Neumann-Haefelin
authors.forename: M E
authors.initials: ME
authors.lastname: Moseley
authors.forename: M P
authors.initials: MP
authors.lastname: Marks
authors.forename: G W
authors.initials: GW
authors.lastname: Albers
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000473:pathology* / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D020521:Stroke / Q000473:pathology* / Q000503:physiopathology