Characterizing dementia with Lewy bodies by means of diffusion tensor imaging

To investigate patterns of in vivo white matter tract change using diffusion tensor imaging (DTI), we conducted a cross-sectional study of dementia with Lewy bodies (DLB) in comparison with Alzheimer disease (AD) and normal aging.

The study included 106 subjects (35 with DLB, 36 with AD, and 35 elderly controls) who underwent clinical and neuropsychological assessment and diffusion tensor MRI. We used tract-based spatial statistics to investigate patterns of reduced fractional anisotropy (FA) and increased mean diffusivity (MD) across the entire white matter tract skeleton and also investigated correlations with clinical features.

Areas of reduced FA in subjects with DLB vs controls were found primarily in parieto-occipital white matter tracts; in AD, the changes were much more diffuse. DLB was also associated with reduced FA in the pons and left thalamus, in comparison with AD. The pattern of MD increase was diffuse in AD and DLB. We found an association between DTI parameters and impaired episodic memory, letter fluency, and severity of motor parkinsonism in DLB.

Despite a similar level of dementia severity, patterns of DTI changes in AD and DLB differed significantly. The selective involvement of the visual association areas and subcortical structures and the significant clinical correlations highlight the potential importance of white matter tract change in the pathogenesis of DLB. DTI may be a useful technique to investigate early and possible preclinical changes in DLB and warrants further investigation.