title: Existence of the diffusion-perfusion mismatch within 24 hours after onset of acute stroke: dependence on proximal arterial occlusion.
abstract: OBJECTIVE
  To assess the existence of a mismatch between lesions on diffusion-weighted (DW) and perfusion-weighted (PW) magnetic resonance (MR) images obtained within 24 hours after onset of acute stroke and to use mismatch data and angiographic evidence of proximal arterial occlusion (PAO) to investigate whether the existence of the mismatch depends on the existence of PAO.
  
  
  METHODS
  In this institutional review board-approved, HIPAA-compliant study, 109 retrospectively identified patients had undergone DW and PW imaging within 24 hours of stroke onset. Relative mismatch was computed as the difference between lesion volumes on mean transit time maps and DW images, divided by DW lesion volume. Computed tomographic (CT) angiography or MR angiography distinguished patients with PAO (n = 68) from those with no PAO (NPAO; n = 41). Eligibility for hypothetical thrombolysis was assessed with two different criteria: (a) one derived from the successful Desmoteplase in Acute Ischemic Stroke Trial (DIAS) and Dose Escalation of Desmoteplase for Acute Ischemic Stroke Trial (DEDAS), and (b) another requiring 160% mismatch.
  
  
  RESULTS
  Of the 109 patients, 77 (71%) satisfied the DIAS-DEDAS eligibility criteria, and 61 (56%) satisfied the 160% criterion. The NPAO patients demonstrated decreasing eligibility with increasing time after onset by using DIAS-DEDAS criteria (P = .015) and showed a similar trend with the 160% criterion (P = .078). The NPAO patients were less likely to be eligible after 9 hours than before 9 hours (17% for >9 hours vs 72% for <9 hours with DIAS-DEDAS criteria, P = .002; and 8% for >9 hours vs 45% for <9 hours with 160% criterion, P = .033). However, PAO patients demonstrated a trend toward increasing eligibility with the DIAS-DEDAS criteria (P = .099) and no significant difference for after 9 hours versus before 9 hours (84% for >9 hours vs 78% for <9 hours with DIAS-DEDAS criteria, P = .742; and 68% for >9 hours vs 69% for <9 hours with 160% criterion, P > .999).
  
  
  CONCLUSIONS
  Persistence of mismatch after 9 hours is common and occurs most often in patients with PAO.
authors.affiliation: Department of Radiology, Massachusetts General Hospital, GRB-273A, 55 Fruit St, Boston, MA 02114, USA. wcopen@partners.org
authors.forename: William A
authors.initials: WA
authors.lastname: Copen
authors.forename: Leila
authors.initials: L
authors.lastname: Rezai Gharai
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Barak
authors.forename: Lee H
authors.initials: LH
authors.lastname: Schwamm
authors.forename: Ona
authors.initials: O
authors.lastname: Wu
authors.forename: Shahmir
authors.initials: S
authors.lastname: Kamalian
authors.forename: R Gilberto
authors.initials: RG
authors.lastname: Gonzalez
authors.forename: Pamela W
authors.initials: PW
authors.lastname: Schaefer
mesh_terms: D000208:Acute Disease; D000368:Aged; D016893:Carotid Stenosis / Q000150:complications* / Q000175:diagnosis*; D002533:Cerebral Angiography / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020521:Stroke / Q000150:complications* / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed / Q000379:methods*