title: Magnetic resonance imaging detection of microbleeds before thrombolysis: an emerging application.
abstract: BACKGROUND
  Hemorrhagic transformation (HT) is a major complication of thrombolytic treatment for acute ischemic stroke. Although a history of prior intracerebral hemorrhage diagnosed by head CT is a contraindication to thrombolysis, there are no guidelines or data regarding evidence of prior asymptomatic microbleeds visualized with T2*-weighted magnetic resonance imaging (MRI).
  
  
  METHODS
  Pretreatment T2*-weighted MRI sequences were retrospectively analyzed in all patients receiving intra-arterial thrombolytic therapy and undergoing a pretreatment MRI at our institution. The frequency and location of prior microbleeds was determined and compared with the frequency and location of secondary HT after therapy.
  
  
  RESULTS
  Five of 41 patients undergoing MRI before receiving intra-arterial thrombolytic therapy demonstrated evidence of prior microbleeds on the pretreatment MRI studies. Major symptomatic hemorrhage occurred in 1 of 5 patients with microbleeds compared with 4 of 36 patients without. Only 1 patient in the entire 41-patient cohort experienced any HT outside the acute ischemic field. In this patient, the symptomatic hemorrhage occurred directly at the site of a prior microbleed, contralateral to the acute ischemic event.
  
  
  CONCLUSIONS
  Old silent microbleeds, visualized with T2*-weighted MRI sequences, may be a marker of increased risk of HT in patients receiving thrombolytic therapy for acute ischemic stroke. Pretreatment screening of thrombolytic candidates with these MRI sequences may be useful in the future to identify these patients.
authors.affiliation: UCLA Stroke Center, Department of Neurology, UCLA Medical Center, Los Angeles, CA 90095, USA. ckidwell@ucla.edu
authors.forename: Chelsea S
authors.initials: CS
authors.lastname: Kidwell
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Saver
authors.forename: J Pablo
authors.initials: JP
authors.lastname: Villablanca
authors.forename: Gary
authors.initials: G
authors.lastname: Duckwiler
authors.forename: Andre
authors.initials: A
authors.lastname: Fredieu
authors.forename: Kristi
authors.initials: K
authors.lastname: Gough
authors.forename: Megan C
authors.initials: MC
authors.lastname: Leary
authors.forename: Sidney
authors.initials: S
authors.lastname: Starkman
authors.forename: Y Pierre
authors.initials: YP
authors.lastname: Gobin
authors.forename: Reza
authors.initials: R
authors.lastname: Jahan
authors.forename: Paul
authors.initials: P
authors.lastname: Vespa
authors.forename: David S
authors.initials: DS
authors.lastname: Liebeskind
authors.forename: Jeffry R
authors.initials: JR
authors.lastname: Alger
authors.forename: Fernando
authors.initials: F
authors.lastname: Vinuela
mesh_terms: D000208:Acute Disease; D000368:Aged; D002545:Brain Ischemia / Q000188:drug therapy*; D002543:Cerebral Hemorrhage / Q000175:diagnosis* / Q000000981:diagnostic imaging; D000075202:Contraindications; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008833:Microcirculation; D012189:Retrospective Studies; D020521:Stroke / Q000188:drug therapy*; D015912:Thrombolytic Therapy; D014057:Tomography, X-Ray Computed