Structural and diffusion MRI in dementia with Lewy bodies :a comparison with Alzheimer's disease and normal ageing

Abstract

Purpose: Dementia with Lewy bodies (DLB) is a common form of dementia, yet its clinical features remain poorly understood. We investigated in vivo structural and micro-structural changes in DLB compared to Alzheimer’s disease (AD) and normal ageing using magnetic resonance imaging (MRI) techniques and their relationship to clinical features. Methods: Study subjects (35 DLB, 36 AD, 35 Controls) completed clinical and cognitive assessments and structural and diffusion tensor MRI scans. Voxel based morphometry (VBM) techniques were used to investigate patterns of regional grey matter atrophy. To investigate white matter tract change, diffusion tensor imaging (DTI) indices, fractional anisotropy (FA) and mean diffusivity (MD) were measured across the entire white matter skeleton using the tract based spatial statistics (TBSS) analysis. Results: Groups were well matched for demographic and clinical factors, although, as expected, the DLB group also had more neuropsychiatric features, greater parkinsonism and more functional impairment than the AD group. VBM analysis indicated a less diffuse pattern of grey matter atrophy in DLB than observed in AD, with areas of loss including the posterior and subcortical regions without significant frontal atrophy. DLB had greater preservation of the medial temporal lobe structures when compared to AD, which was associated with less impaired memory function. The pattern of FA change in DLB compared to controls involved the parieto-occipital white matter tracts; in AD, the FA change was more diffuse. In DLB, an association was found between reduced FA and the phonemic fluency tasks in the white-matter tracts of the precentral gyrus, anterior cingulate and precuneus in DLB. Abstract ii Conclusions: Despite a similar level of dementia severity, the patterns of structural and diffusion tensor MRI changes in AD and DLB differ significantly. DLB was associated with less grey matter volume loss and less white matter tract change than AD along with differing regional patterns of change.