title: When to expect negative diffusion-weighted images in stroke and transient ischemic attack.
abstract: OBJECTIVE
  The frequency of DWI negative cerebral ischemia and clinical factors associated with such a circumstance is not well understood.
  
  
  METHODS
  We performed MRI including diffusion-weighted imaging (DWI) in patients with stroke and transient ischemic attack (TIA) within 24 hours of symptom onset and again at 30 days.
  
  
  RESULTS
  Of 401 patients, 103 (25.6%) had an initial negative DWI study. In the DWI negative group, among the stroke patients, 6/26 (23.1%) had infarcts on follow-up MRI (4 lacunar and 2 posterior circulation syndromes) and 1 had a rMTT deficit. Among the TIA patients, 4/63 (6.3%) showed rMTT deficits and 2/63 (3.2%) had infarcts on follow-up MRI.
  
  
  CONCLUSIONS
  Baseline perfusion weighted imaging sequences may detect ischemia in a small proportion of DWI negative cases. Only those with brain stem location or lacunar syndrome were DWI negative initially and yet had a follow-up imaging confirmation of infarct or a final clinical diagnosis of stroke.
authors.affiliation: Calgary Stroke Program, Department of Clinical Neurosciences, Foothills Medical Centre, Room 1162, University of Calgary, Alberta, Canada.
authors.forename: P N
authors.initials: PN
authors.lastname: Sylaja
authors.forename: Shelagh B
authors.initials: SB
authors.lastname: Coutts
authors.forename: Andrea
authors.initials: A
authors.lastname: Krol
authors.forename: Michael D
authors.initials: MD
authors.lastname: Hill
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Demchuk
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D001921:Brain / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology; D020520:Brain Infarction / Q000473:pathology / Q000503:physiopathology; D020526:Brain Stem Infarctions / Q000473:pathology / Q000503:physiopathology; D002536:Cerebral Arteries / Q000473:pathology* / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards*; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D020521:Stroke / Q000473:pathology* / Q000503:physiopathology
chemical_list: D015415:Biomarkers