title: New appearance of extraischemic microbleeds on T2*-weighted magnetic resonance imaging 24 hours after tissue-type plasminogen activator administration.
abstract: OBJECTIVE
  It is unknown whether new-extraischemic microbleeds (new-EMBs) develop rapidly after tissue-type plasminogen activator (tPA) infusion. We hypothesized that new-EMBs may develop rapidly after tPA infusion using T2*-weighted MRI (T2*) and investigated the frequency and clinical factors associated with new-EMBs.
  
  
  METHODS
  Patients with acute stroke within 3 hours of onset who were treated with tissue-type plasminogen activator (tPA) were studied prospectively. T2* was performed before and 24 hours after tPA therapy. Independent clinical factors associated with new-EMBs development were examined using multivariate logistic regression analysis.
  
  
  RESULTS
  A total of 224 patients (121 men; mean age, 76.2±10.6 years) were enrolled in the present study. MBs before tPA infusion were observed in 72 (32.1%) patients. Within 24 hours after tPA infusion, 6 (2.7%) patients had symptomatic intracranial hemorrhage (extraischemic [n=4], and hemorrhagic transformation [n=2]). Follow-up T2* revealed asymptomatic new-EMBs in 11 (4.9%) patients and hemorrhagic transformation in the infarcted area in 65 (29.0%). The total and mean number of new-EMBs were 23 and 1.6±1.3, respectively. Patients with new-EMBs more frequently had symptomatic extraischemic hemorrhage than those without new-EMBs (27.3% [3/11] versus 0.5% [1/213]; P=0.0003). However, the frequency of hemorrhagic transformation was not different between patients with and without new-EMBs (27.3% versus 29.1%; P=0.9999). Multivariate logistic regression demonstrated that the presence of MBs before tPA infusion was the only independent factor associated with new-EMBs (odds ratio, 10.6; 95% confidence interval, 20.68-54.279; P=0.0046).
  
  
  CONCLUSIONS
  New-EMBs occurred rapidly after tPA infusion in 4.9% of patients. The presence of MBs before tPA therapy was associated with new-EMBs. Patients with new-EMBs are likely to have symptomatic extraischemic hemorrhage.
authors.affiliation: From the Department of Stroke Medicine, Kawasaki Medical School, Kurashiki City, Japan.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Kimura
authors.forename: Junya
authors.initials: J
authors.lastname: Aoki
authors.forename: Kensaku
authors.initials: K
authors.lastname: Shibazaki
authors.forename: Naoki
authors.initials: N
authors.lastname: Saji
authors.forename: Junichi
authors.initials: J
authors.lastname: Uemura
authors.forename: Yuki
authors.initials: Y
authors.lastname: Sakamoto
mesh_terms: D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D002543:Cerebral Hemorrhage / Q000139:chemically induced / Q000000981:diagnostic imaging; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005343:Fibrinolytic Agents / Q000008:administration & dosage / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D020521:Stroke / Q000000981:diagnostic imaging / Q000188:drug therapy; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D005343:Fibrinolytic Agents; D010959:Tissue Plasminogen Activator
keywords: hemorrhage; infarction; magnetic resonance imaging; thrombolytic therapy