title: Detectability of ischemic lesions on diffusion-weighted imaging is biphasic after transient ischemic attack.
abstract: BACKGROUND
  Experimental studies of transient focal ischemia indicate biphasic detectability of lesions by diffusion-weighted imaging (DWI); poorly detectable phase exists at 1-12 hours after reperfusion. The present study aimed to clarify whether poorly detectable phase also exists in DWI of transient ischemic attack (TIA) patients.
  
  
  METHODS
  A retrospective study was conducted in 144 consecutive TIA patients who underwent magnetic resonance imaging (MRI) within 2 weeks after carotid TIA. Patients were classified into 9 groups according to time from disappearance of TIA symptoms to DWI: intraischemic period, 0-1 hour, 1-12 hours, 12-24 hours, 1-2 days, 2-3 days, 3-7 days, 7-10 days, and 10-14 days after the end of TIA.
  
  
  RESULTS
  Lesions were detected in 33 of 144 patients (22.9%). The frequency of positive lesions was 20% in the intraischemic period and 30.8% at 0-1 hour after the end of TIA; it markedly decreased to 8.7% at 1-12 hours after end of TIA. Thereafter, it increased to 21.7%, 30.8%, 36.4%, 37.0%, 38.5%, and 30% at 12-24 hours, 1-2 days, 2-3 days, 3-7 days, 7-10 days, and 10-14 days after the end of TIA, respectively. In 7 patients, MRI was repeated twice, at 1-12 hours and then at 5-13 days after the end of TIA. Lesions were never detected on the first MRI but were clearly demonstrated in 4 of 7 patients on the second MRI.
  
  
  CONCLUSIONS
  The detectability of ischemic lesions may be biphasic after TIA as indicated by experimental studies.
authors: Department of Neurology, National Cerebral and Cardiovascular Center, Suita, Japan; Department of Internal Medicine, Takarazuka Sanda Hospital, Sanda, Japan. Electronic address: hisaunotsh@leto.eonet.ne.jp.
authors: Hisakazu
authors: H
authors: Uno
authors: Department of Neurology, National Cerebral and Cardiovascular Center, Suita, Japan.
authors: Kazuyuki
authors: K
authors: Nagatsuka
authors: Department of Preventive Medicine and Epidemiologic Informatics, National Cerebral and Cardiovascular Center, Suita, Japan.
authors: Yoshihiro
authors: Y
authors: Kokubo
authors: Department of Radiology, National Cerebral and Cardiovascular Center, Suita, Japan.
authors: Masahiro
authors: M
authors: Higashi
authors: Department of Radiology, National Cerebral and Cardiovascular Center, Suita, Japan.
authors: Naoaki
authors: N
authors: Yamada
authors: Department of Neurology, National Cerebral and Cardiovascular Center, Suita, Japan.
authors: Arisa
authors: A
authors: Umesaki
authors: Department of Cerebrovascular Medicine, National Cerebral and Cardiovascular Center, Suita, Japan.
authors: Kazunori
authors: K
authors: Toyoda
authors: Department of Neurology, National Cerebral and Cardiovascular Center, Suita, Japan.
authors: Hiroaki
authors: H
authors: Naritomi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology*; D002339:Carotid Arteries / Q000473:pathology; D016009:Chi-Square Distribution; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D002546:Ischemic Attack, Transient / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013997:Time Factors
keywords: Diffusion-weighted imaging; detectability; refractory phase; transient ischemic attack