title: Reversible posterior leukoencephalopathy syndrome: evaluation with diffusion-tensor MR imaging.
abstract: OBJECTIVE
  To characterize the changes in brain water diffusion caused by reversible posterior leukoencephalopathy syndrome (RPLS).
  
  
  METHODS
  Twelve patients with the clinical features and conventional magnetic resonance (MR) imaging findings of RPLS underwent diffusion-tensor echo-planar MR imaging. The isotropic diffusion coefficient (D) and diffusion anisotropy (A(sigma)) were measured in posterior regions of diffusion abnormality and in anterior areas of normal-appearing brain.
  
  
  RESULTS
  Across all 12 subjects, the mean D of (1.09 +/- 0.13 [SD]) x 10(-3) mm(2)/sec in affected posterior regions was 26% greater than its value of (0.87 +/- 0.07) x 10(-3) mm(2)/sec in normal-appearing anterior regions. The mean A(sigma) of 0.15 +/- 0.03 in posterior regions was 35% less than its value of 0.23 +/- 0.02 in anterior regions (t(11) = 9.58; P <.001). There was a significant inverse correlation between D and A(sigma) in posterior regions (r = -0.67; P <.018) but not in anterior regions (r = -0.12; P =.719). A follow-up study performed in one patient after resolution of symptoms documented reversal of elevated isotropic diffusion and at least partial recovery of anisotropy loss.
  
  
  CONCLUSIONS
  The increased magnitude of brain water diffusion characteristic of RPLS is accompanied by reduced A(sigma). The magnitudes of these two effects are correlated and may be reversible. These observations support the proposal that vasogenic edema due to cerebrovascular autoregulatory dysfunction is the underlying pathophysiologic mechanism in uncomplicated RPLS.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd, St Louis, MO 63110, USA. mukherjeep@mir.wustl.edu
authors.forename: P
authors.initials: P
authors.lastname: Mukherjee
authors.forename: R C
authors.initials: RC
authors.lastname: McKinstry
mesh_terms: D000328:Adult; D001921:Brain / Q000378:metabolism / Q000473:pathology*; D003711:Demyelinating Diseases / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D012189:Retrospective Studies