title: Does Alzheimer's disease affect hippocampal asymmetry? Evidence from a cross-sectional and longitudinal volumetric MRI study.
abstract: OBJECTIVE
  To determine whether Alzheimer's disease (AD) is associated with preferential atrophy of either the left or right hippocampus.
  
  
  METHODS
  We examined right-left asymmetry in hippocampal volume and atrophy rates in 32 subjects with probable AD and 50 age-matched controls. Hippocampi were measured on two serial volumetric MRI scans using a technique that minimizes laterality bias.
  
  
  RESULTS
  We found a non-significant trend for right > left (R > L) asymmetry in controls at both time points (R > L: 1.7%; CI: -0.3-3.7%; p = 0.1). AD subjects showed a similar non-significant trend for R > L asymmetry at baseline (R > L: 1.8%; CI: -1.9-5.5%; p = 0.32), but not at repeat (p = 0.739). Change in R/L ratio between visits in AD patients was significant (p = 0.02). The AD group had significantly higher variance in these ratios than the controls at baseline (p = 0.02), but not repeat (p = 0.06). AD patients had higher atrophy rates than controls (p < 0.001). Mean (CI) annualized atrophy rates for left and right hippocampi were 1.2% (0.5-1.8%) and 1.1% (0.5-1.8%) for the controls, and 4.6% (3.3-6.0%) and 6.3% (4.9-7.8%) for AD subjects. There was no significant asymmetry in atrophy rates in controls (p = 0.9), but borderline significantly higher atrophy rates in the right hippocampus of the AD group (p = 0.05) compared to the left. Presence of an APOEepsilon4 allele had no significant effect on the size, asymmetry or atrophy rates in AD (p > 0.20).
  
  
  CONCLUSIONS
  We report minor R > L asymmetry in hippocampal volumes in controls and present some evidence to suggest that there is a change in the natural R > L asymmetry during the progression of AD.
authors.affiliation: Dementia Research Centre, Department of Clinical Neurology, Institute of Neurology, University College London, London, UK. j.barnes@dementia.ion.ucl.ac.uk
authors.forename: Josephine
authors.initials: J
authors.lastname: Barnes
authors.forename: Rachael I
authors.initials: RI
authors.lastname: Scahill
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Schott
authors.forename: Chris
authors.initials: C
authors.lastname: Frost
authors.forename: Martin N
authors.initials: MN
authors.lastname: Rossor
authors.forename: Nick C
authors.initials: NC
authors.lastname: Fox
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000235:genetics / Q000473:pathology*; D053327:Apolipoprotein E4; D001057:Apolipoproteins E / Q000235:genetics; D001284:Atrophy; D003430:Cross-Sectional Studies; D005260:Female; D007839:Functional Laterality; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged
chemical_list: D053327:Apolipoprotein E4; D001057:Apolipoproteins E