Diffusivity Changes Are Predominantly Proportional Along All Axes with Early Neurodegeneration in Alzheimer's Disease

Julio Acosta-Cabronero¹, Guy B. Williams¹, George Pengas¹, Peter J. Nestor¹

Diffusion tensor imaging has become a major research focus in neurodegenerative diseases such as Alzheimers disease (AD). Most studies have concentrated on fractional anisotropy (FA) reductions. Using tract-based spatial statistics, we found that increases in axial, radial and mean diffusivity in AD were concordant and far more sensitive than FA reductions. The former three measures identified largely confluent white matter abnormalities in parahippocampal gyrus and posterior cingulum, extending laterally into adjacent temporoparietal regions as well as splenium and fornix. This study offers a very plausible and comprehensive view of the landscape of white-matter tract degeneration in early-stage AD.