Abstract
Background: Hippocampal grey matter (GM) atrophy predicts conversion from
mild cognitive impairment (MCI) to Alzheimer’s disease (AD). Pilot data suggests that mean
diffusivity (MD) in the hippocampus, as measured with diffusion tensor imaging (DTI), may
be a more accurate predictor of conversion than hippocampus volume. In addition, previous
studies suggest that volume of the cholinergic basal forebrain may reach a diagnostic
accuracy superior to hippocampal volume in MCI.
Objective: The present study investigated whether increased MD and decreased
volume of the hippocampus, the basal forebrain and other AD-typical regions predicted time
to conversion from MCI to AD dementia.
Methods: 79 MCI patients with DTI and T1-weighted magnetic
resonance imaging (MRI) were retrospectively included from the European DTI Study in
Dementia (EDSD) dataset. Of these participants, 35 converted to AD dementia after 6–46
months (mean: 21 months). We used Cox regression to estimate the relative conversion risk
predicted by MD values and GM volumes, controlling for age, gender, education and
center.
Results: Decreased GM volume in all investigated regions predicted an
increased risk for conversion. Additionally, increased MD in the right basal forebrain
predicted increased conversion risk. Reduced volume of the right hippocampus was the only
significant predictor in a stepwise model combining all predictor variables.
Conclusion: Volume reduction of the hippocampus, the basal forebrain and
other AD-related regions was predictive of increased risk for conversion from MCI to AD.
In this study, volume was superior to MD in predicting conversion.
