Improvement of the thalamocortical white matter network in people with stable treated relapsing–remitting multiple sclerosis over time

Abstract

AbstractAdvanced imaging techniques (tractography) enable the mapping of white matter (WM) pathways and the understanding of brain connectivity patterns. We combined tractography with a network‐based approach to examine WM microstructure on a network level in people with relapsing–remitting multiple sclerosis (pw‐RRMS) and healthy controls (HCs) over 2 years. Seventy‐six pw‐RRMS matched with 43 HCs underwent clinical assessments and 3T MRI scans at baseline (BL) and 2‐year follow‐up (2‐YFU). Probabilistic tractography was performed, accounting for the effect of lesions, producing connectomes of 25 million streamlines. Network differences in fibre density across pw‐RRMS and HCs at BL and 2‐YFU were quantified using network‐based statistics (NBS). Longitudinal network differences in fibre density were quantified using NBS in pw‐RRMS, and were tested for correlations with disability, cognition and fatigue scores. Widespread network reductions in fibre density were found in pw‐RRMS compared with HCs at BL in cortical regions, with more reductions detected at 2‐YFU. Pw‐RRMS had reduced fibre density at BL in the thalamocortical network compared to 2‐YFU. This effect appeared after correction for age, was robust across different thresholds, and did not correlate with lesion volume or disease duration. Pw‐RRMS demonstrated a robust and long‐distance improvement in the thalamocortical WM network, regardless of age, disease burden, duration or therapy, suggesting a potential locus of neuroplasticity in MS. This network's role over the disease's lifespan and its potential implications in prognosis and treatment warrants further investigation.