Does Alzheimer’s Disease Affect Hippocampal Asymmetry? Evidence from a Cross-Sectional and Longitudinal Volumetric MRI Study

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 0.20). 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.