title: Low-signal-intensity rim on susceptibility-weighted imaging is not a specific finding to progressive multifocal leukoencephalopathy.
abstract: BACKGROUND
  Low-signal-intensity (LSI) rim along deep layers of the cerebral cortex is reportedly a susceptibility-weighted imaging (SWI) finding in progressive multifocal leukoencephalopathy (PML). We aimed to evaluate whether this finding can be identified in diseases other than PML.
  
  
  METHODS
  We retrospectively reviewed brain MR images from 5605 patients who underwent SWI at 3T; 370 patients with various diseases, who showed cortical and subcortical FLAIR high-signal lesions including U-fiber, were enrolled. The presence or absence of LSI rim on thin-slice SWI and hyperintense cortical signal (HCS) on T1-weighted images adjacent to LSI rim was analyzed. Signal changes of the LSI rim were assessed on serial SWI, if available.
  
  
  RESULTS
  Twenty-five of the 370 patients (6.8%) showed SWI LSI rim, in infarct (n=22) and encephalitis (n=3). HCS was apparent adjacent to SWI LSI rim in 17 patients (15 infarct, 2 encephalitis). Serial SWI was available for 17 patients, of whom 10 patients (8 infarct, 2 encephalitis) presented LSI rim later than 45days after onset.
  
  
  CONCLUSIONS
  LSI rim can be observed in infarct and encephalitis. Therefore, this finding is not specific to PML. LSI rim appears to be associated with HCS.
authors.affiliation: Department of Radiology, Mie University School of Medicine, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Umino
authors.affiliation: Department of Advanced Diagnostic Imaging, Mie University School of Medicine, Japan. Electronic address: mmaeda@clin.medic.mie-u.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Maeda
authors.affiliation: Department of Neurology, Mie University School of Medicine, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Ii
authors.affiliation: Department of Neurology, Mie University School of Medicine, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Tomimoto
authors.affiliation: Department of Radiology, Mie University School of Medicine, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Sakuma
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007968:Leukoencephalopathy, Progressive Multifocal / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D015898:Tomography Scanners, X-Ray Computed
keywords: Hyperintense cortical signal; Low-signal-intensity rim; Susceptibility-weighted imaging