title: Paradoxically Decreased Mean Transit Time in Patients Presenting With Acute Stroke.
abstract: OBJECTIVE
  Computed tomography perfusion (CTP) has become a mainstay in acute stroke management. The aim of this study was to investigate the occurrence of an unreported phenomenon of a paradoxically decreased mean transit time (MTT) in the cerebral area of ischemia.
  
  
  METHODS
  In this retrospective study, patients with an acute anterior circulation ischemic stroke were selected. Computed tomography perfusion diffusion maps of all patients were reviewed by 2 blinded and experienced neuroradiologists.
  
  
  RESULTS
  A total of 31 patients were included in the study. Eighteen subjects (58%) had a paradoxical MTT perfusion map, whereas only 13 (42%) had an expected CTP profile. No significant associations between the paradoxical MTT perfusion and the size of the infarct, the side of the occlusion, or the age of the patients were observed. However, a trend in collateral circulation status and paradoxical MTT was noted.
  
  
  CONCLUSIONS
  A paradoxical MTT response is a frequent finding in CTP analysis of patients with acute stroke. Its presence is not associated to the location or size of the affected cerebral territory and could be related to the presence of collateral circulation.
authors.affiliation: From the *Faculty of Medicine, McGill University, Montreal; †Institut de recherche en santé publique de l'université de Montréal, Montreal; and ‡Montreal Neurological Hospital and Institute, Montreal, Quebec, Canada.
authors.forename: Cédric
authors.initials: C
authors.lastname: Doucet
authors.forename: Federico
authors.initials: F
authors.lastname: Roncarolo
authors.forename: Donatella
authors.initials: D
authors.lastname: Tampieri
authors.forename: Maria
authors.initials: M
authors.lastname: Del Pilar Cortes
mesh_terms: D000368:Aged; D002533:Cerebral Angiography; D002560:Cerebrovascular Circulation; D000072226:Computed Tomography Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D063177:Pulse Wave Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D020521:Stroke / Q000000981:diagnostic imaging* / Q000503:physiopathology*