title: Diffusion- and perfusion-weighted MRI: influence of severe carotid artery stenosis on the DWI/PWI mismatch in acute stroke.
abstract: OBJECTIVE
  Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) have been used increasingly in recent years to evaluate acute stroke in the emergency setting. In the present study, we compared DWI and PWI findings in acute stroke patients with and without severe extracranial internal carotid artery (ICA) disease.
  
  
  METHODS
  Twenty-seven patients with nonlacunar ischemic stroke were selected for this analysis. DWI, PWI, and conventional MRI were performed in all patients within 24 hours of symptom onset and after 1 week. To exclude patients with partial or complete reperfusion, we included only patients with a PWI deficit larger than the DWI lesion. Severe ICA disease (>70% stenosis) was present unilaterally in 9 and bilaterally in 2 patients. Acute DWI lesion volume, the size of the acute PWI/DWI mismatch, and final infarct size (on T2-weighted images) were determined.
  
  
  RESULTS
  The PWI/DWI mismatch was significantly larger in patients with severe ICA disease than in patients without extracranial carotid stenosis, both when time-to-peak and mean transit time maps (P<0.01) were used to calculate the mismatch. Quantitative analysis of the time-to-peak delay in the mismatch indicated that a relatively smaller fraction of the total mismatch was critically ischemic in patients with carotid stenosis than in those without. Average lesion volume increased less in the stenosis group (P=0.14), despite the larger PWI/DWI mismatch, and final infarct size was smaller in the stenosis group (P<0.05). In the 2 patients with bilateral ICA disease, variable hemodynamic involvement of the contralateral hemisphere was found in addition to the ipsilateral PWI deficit.
  
  
  CONCLUSIONS
  In most acute stroke patients with severe ICA stenosis, a considerably smaller fraction of the total PWI/DWI mismatch is at risk than in patients without carotid disease.
authors.affiliation: Department of Neurology, Heinrich-Heine University, Düsseldorf, Germany. tnh@rz.uni-frankfurt.de
authors.forename: T
authors.initials: T
authors.lastname: Neumann-Haefelin
authors.forename: H J
authors.initials: HJ
authors.lastname: Wittsack
authors.forename: G R
authors.initials: GR
authors.lastname: Fink
authors.forename: F
authors.initials: F
authors.lastname: Wenserski
authors.forename: T Q
authors.initials: TQ
authors.lastname: Li
authors.forename: R J
authors.initials: RJ
authors.lastname: Seitz
authors.forename: M
authors.initials: M
authors.lastname: Siebler
authors.forename: U
authors.initials: U
authors.lastname: Mödder
authors.forename: H J
authors.initials: HJ
authors.lastname: Freund
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000209:etiology / Q000473:pathology; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging; D016893:Carotid Stenosis / Q000150:complications* / Q000000981:diagnostic imaging; D002544:Cerebral Infarction / Q000209:etiology / Q000473:pathology; D002560:Cerebrovascular Circulation; D004632:Emergency Medical Services; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000209:etiology / Q000473:pathology*; D014463:Ultrasonography