Longitudinal Tract-Based Spatial Statistics Analysis Reveals Left & Right Asymmetric DTI Alterations in Relapsing Remitting Multiple Sclerosis

Salem Hannoun¹, Francoise Durand-Dubief^1,2, Christian Confavreux², Francois Cotton¹, Dominique Sappey-Marinier^1,3

This study aims to characterize longitudinal alterations of white matter (WM) over a period of 2 years in different clinical forms of multiple sclerosis (MS) using tract-based spatial statistics (TBSS). Significant alterations of diffusivity including FA decrease, and λ1, λ2 and λ3 increases were mostly found in the right hemisphere of relapsing-remitting (RR) patients, particularly in the external capsule (EC). Region of interest (ROI) analysis of this region confirmed these results and allowed the quantification of these changes over time. The comparison between left and right EC of DTI metrics variations over time showed significant decreases of FA and increases of λ1, λ2 and λ3 in the right ROI. This finding probably reflects an evolving process spreading from the left to the right hemisphere that may result from demyelination and/or remyelination processes in the right and left hemispheres, respectively.