Longitudinal diffusion tensor imaging correlates with amyloid burden in Down syndrome

Adults with Down syndrome (DS) accumulate amyloid beta (Aβ) plaques faster and earlier on average than neurotypical adults with sporadic Alzheimer's disease (AD). White matter (WM) microstructure characterized with diffusion tensor imaging (DTI) can indicate underlying architectural changes in longitudinal studies, suggestive of neurodegeneration. This study investigated relationships between DTI and Aβ in DS along the AD continuum.

Using longitudinal amyloid Pittsburgh compound B positron emission tomography, Centiloid (CL) and DTI parameters were examined in 35 adults with DS ages 25 to 57. DTI measures of anisotropy and diffusivity were analyzed using tract-based spatial statistics and permutation analysis of linear models, testing for significant correlation between the rates of change for CL and DTI.

All rates of DTI and Aβ changes were significantly related. Significant regions included the corpus callosum, corona radiata, and long-association fibers.

Aβ burden is associated with widespread longitudinal WM changes in DS. This suggests WM microstructure alterations accompany amyloid accumulation.

A Down syndrome-specific template was created. Longitudinal diffusion tensor imaging (DTI) and amyloid burden rates of change correlate. Longitudinal results show more significant regions than cross-sectional results. DTI and amyloid changes were found over two timepoints, 3.7 years apart on average. DTI and amyloid-PET offer greater sensitivity when tracking microstructural changes.