FLAIR Hyperintensity in Acute Ischemic Strokes Beyond 3 Hours is Almost Universal and Does Not Predict Hemorrhagic Transformation

  • Dr Bruce Campbell, Department of Medicine and Neurology, Royal Melbourne Hospital, University of Melbourne, Australia
  • Dr Craig Costello, Department of Medicine and Neurology, Royal Melbourne Hospital, University of Melbourne, Australia
  • Dr Soren Christensen, Department of Radiology, Royal Melbourne Hospital, University of Melbourne, Australia
  • Dr Martin Ebinger, Center for Stroke Research , Charité - Universitätsmedizin Berlin, Germany
  • Dr Mark Parsons, Department of Neurology and Hunter Medical Research Institute, John Hunter Hospital, University of Newcastle, Australia
  • Prof Patricia Desmond, Department of Radiology, Royal Melbourne Hospital, Melbourne, Australia
  • Prof P Alan Barber, Department of Neurology, Auckland Hospital, Auckland, New Zealand
  • Dr Kenneth S. Butcher, Canada
  • A/Prof Christopher Levi, Hunter New England Area Health Service, Australia
  • Deidre A. De Silva, Singapore
  • Dr Maarten G. Lansberg, United States
  • Dr Michael Mlynash, United States
  • Dr Jean-Marc Olivot, United States
  • Dr Matus Straka, United States
  • Dr Roland Bammer, United States
  • Prof Gregory Albers, Stanford Stroke Center, Stanford University, California, United States
  • Prof Geoffrey Donnan, Florey Neuroscience Institutes, University of Melbourne, Australia
  • Prof Stephen Davis, Department of Medicine and Neurology, Royal Melbourne Hospital, University of Melbourne, Australia
  • Dr Neil Spratt, University of Newcastle, Australia

Objective: In ischemic stroke, FLAIR hyperintensity within the region of acute infarction may be a risk factor for post-thrombolysis hemorrhage. We aimed to determine the prevalence of FLAIR hyperintensity in acute stroke patients and whether it was associated with the development of hemorrhage.
Methods: MRI was obtained in patients 3-6 hours after stroke onset and repeated 3-5 days later to detect hemorrhage (ECASS classification). After independent review, 2 raters achieved consensus on the presence of FLAIR hyperintensity, rated as obvious or subtle (ie only visible after careful windowing).
Results: There were 49 patients with adequate pre-treatment FLAIR studies at 3-6 hours, 39 were thrombolysed with tPA and 5 developed parenchymal hematoma (PH). Visible FLAIR hyperintensity within the DWI lesion was almost universal (48/49, 98%) and was rated obvious in 18/49 (37%). Patients with obvious FLAIR hyperintensity had larger DWI lesions (median 34 vs 11mL, p=0.03). There was good inter-rater agreement for classifying subtle vs obvious FLAIR hyperintensity (92%, kappa=0.82). The prevalence of obvious FLAIR hyperintensity did not differ between patients imaged in the 3-4.5 hour and 4.5-6 hour time periods (40% vs 33%, p=0.77). Obvious FLAIR hyperintensity was a poor predictor of PH (sensitivity 40%, specificity 64%, positive predictive value 11%).
Conclusions: Visible FLAIR hyperintensity is almost universal 3-6 hours after stroke onset and obvious hyperintensity is not a useful predictor of hemorrhage risk. Patients with FLAIR hyperintensity should not be excluded from thrombolysis pending further studies to clarify what implications, if any, FLAIR positive lesions have for patient selection.