title: Diffusion-negative MRI in acute ischemic stroke: a case report.
abstract: BACKGROUND
  Diffusion-weighted magnetic resonance imaging is a very sensitive tool for the early diagnosis of acute ischemic stroke. This is employed in some stroke centers as the primary screening tool to select patients eligible for thrombolysis.
  
  
  METHODS
  We present the case of a 49-years old Chinese man whose diffusion-weighted magnetic resonance imaging performed 12 hours of symptom onset was negative.
  
  
  RESULTS
  Although the initial diffusion-weighted magnetic resonance imaging was negative, the imaging repeated after 4 days despite static neurological symptoms and signs, could demonstrate an acute medullary infarction.
  
  
  CONCLUSIONS
  Diffusion-weighted imaging may not be100% sensitive in very early stages, especially in posterior circulation strokes. Our case serves as a reminder that clinical assessment still retains priority until a diagnostic modality offering 100% sensitivity and specificity is discovered.
authors.affiliation: Division of Neurology, Department of Medicine, National University Hospital, Singapore. drvijay@singnet.com.sg.
authors.forename: Rahul
authors.initials: R
authors.lastname: Rathakrishnan
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Sharma
authors.forename: Bernard Pl
authors.initials: BP
authors.lastname: Chan