title: Altered microstructure in corticospinal tract in idiopathic normal pressure hydrocephalus: comparison with Alzheimer disease and Parkinson disease with dementia.
abstract: OBJECTIVE
  Previous neuropathologic studies in chronic hydrocephalus have suggested the presence of white matter damage, presumably from mechanical pressure due to ventricular enlargement and metabolic derangement. This study aimed to investigate the diffusional properties of the CST in patients with iNPH by using DTI and to determine whether this method could be used as a new diagnostic tool to differentiate patients with iNPH from those with AD and PDD and control  subjects.
  
  
  METHODS
  We enrolled 18 patients with iNPH, 11 patients with AD, 11 patients with PDD, and 19 healthy control subjects. Diffusion tensor metrics of the segmented CST, including FA values, axial eigenvalues, and radial eigenvalues, were evaluated by using tract-specific analysis. The anisotropy color-coding tractography of the CST was visually evaluated. The DTI findings were compared among  groups.
  
  
  RESULTS
  Tract-specific analysis of the CST showed that FA values and axial eigenvalues were significantly increased (P < .001), whereas radial eigenvalues were not significantly altered, in patients with iNPH compared with other subjects. The CST tractographic images in patients with iNPH was visually different from those in other subjects (P < .001). In discriminating patients with iNPH from other subjects, the CST FA values had a sensitivity of 94% and specificity of 80% at a cutoff value of  0.59.
  
  
  CONCLUSIONS
  Our results suggest that patients with iNPH have altered microstructures in the CST. Quantitative and visual CST evaluation by using DTI may be useful for differentiating patients with iNPH from patients with AD or PDD or healthy  subjects.
authors.affiliation: Department of Neurology and Neurological Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hattori
authors.forename: T
authors.initials: T
authors.lastname: Yuasa
authors.forename: S
authors.initials: S
authors.lastname: Aoki
authors.forename: R
authors.initials: R
authors.lastname: Sato
authors.forename: H
authors.initials: H
authors.lastname: Sawaura
authors.forename: T
authors.initials: T
authors.lastname: Mori
authors.forename: H
authors.initials: H
authors.lastname: Mizusawa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000473:pathology*; D016880:Anisotropy; D003704:Dementia / Q000473:pathology; D003937:Diagnosis, Differential; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000473:pathology*; D008297:Male; D010300:Parkinson Disease / Q000473:pathology*; D011446:Prospective Studies; D011712:Pyramidal Tracts / Q000473:pathology* / Q000648:ultrastructure; D012680:Sensitivity and Specificity