title: White matter imaging changes in subjective and mild cognitive impairment.
abstract: BACKGROUND
  To determine whether white matter (WM) memory network changes accompany early cognitive impairment and whether these changes represent early, pathologically independent axonal affection, we combined WM diffusion tensor imaging and cortical morphometric measurements of normal control subjects, patients with only subjective cognitive impairment (SCI), or mild cognitive impairment (MCI).
  
  
  METHODS
  We included 66 patients with SCI or MCI and 21 control subjects from a university-hospital-based memory clinic in a cross-sectional study. Morphometric analysis was performed in FreeSurfer, and Tract-Based Spatial Statistics was used for analysis of diffusion tensor imaging-derived WM fractional anisotropy, radial diffusivity (DR), and mean diffusivity (MD). Relationships between WM measures and stage were assessed with whole-brain voxelwise statistics and on a region-of-interest basis, with subsequent correction for cortical atrophy.
  
  
  RESULTS
  In SCI patients, as compared with control subjects, there were widespread changes in DR and MD. No significant differences in thickness could be demonstrated. In MCI patients, as compared with control subjects, there were widespread changes in DR, MD, and fractional anisotropy; the precuneal and inferior parietal cortices were thinner; and the hippocampus was smaller. Multiple logistic regression analysis eliminated morphometry as an explanatory variable in favor of DR/MD for all regions of interest, except in the precuneus, where both thickness and DR/MD were significant explanatory variables.
  
  
  CONCLUSIONS
  WM tract degeneration is prominent in SCI and MCI patients, and is at least in part independent of overlying gray matter atrophy.
authors.affiliation: Department of Neurology, Faculty Division, Akershus University Hospital, University of Oslo, Lørenskog, Norway. per.selnes@medisin.uio.no
authors.forename: Per
authors.initials: P
authors.lastname: Selnes
authors.forename: Anders M
authors.initials: AM
authors.lastname: Fjell
authors.forename: Leif
authors.initials: L
authors.lastname: Gjerstad
authors.forename: Atle
authors.initials: A
authors.lastname: Bjørnerud
authors.forename: Anders
authors.initials: A
authors.lastname: Wallin
authors.forename: Paulina
authors.initials: P
authors.lastname: Due-Tønnessen
authors.forename: Ramune
authors.initials: R
authors.lastname: Grambaite
authors.forename: Vidar
authors.initials: V
authors.lastname: Stenset
authors.forename: Tormod
authors.initials: T
authors.lastname: Fladby
mesh_terms: D000368:Aged; D001921:Brain / Q000473:pathology*; D060825:Cognitive Dysfunction / Q000473:pathology*; D003430:Cross-Sectional Studies; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*