Soma and neurite density imaging in multiple sclerosis reveals cortical cell body signal fraction loss associated with thalamic atrophy

Multiple sclerosis (MS) features complex microstructural changes in gray matter (GM) ranging from demyelinating lesions to neuronal loss. We hypothesize that GM microstructural metrics obtained from diffusion MRI can predict cortical and deep GM atrophy in MS. In this cross-sectional study of 41 people with MS, the soma and neurite density imaging (SANDI) compartment-based model was fitted to high-gradient diffusion MRI data acquired on the Connectome scanner. SANDI metrics were used to characterize MS-related microstructural pathology in cortical and deep GM. Cortical fsoma decreased with declining thalamic volume, suggesting a microstructural correlate of thalamic atrophy in MS.