Longitudinal cortical thinning progression differs across multiple sclerosis phenotypes and is clinically relevant: A multicentre study.

Background: Longitudinal evolution of cortical thickness (CTh) in different MS phenotypes has been rarely studied.

Aim: To investigate the regional pattern and 1-year progression of cortical thinning in relapsing-remitting (RR) and progressive (P) MS.

Methods: 3T high-resolution T1-weighted magnetic resonance imaging (MRI) was obtained from 86 patients (75 RRMS, 11 PMS) and 34 healthy controls (HC) at three European sites at baseline and 1-year follow-up. Using FreeSurfer, baseline CTh between-group differences, longitudinal CTh changes and their correlations with clinical and MRI variables were assessed.

Results: Baseline frontal, parietal and sensorimotor atrophy was found in MS versus HC. Such pattern was driven by RRMS, while PMS showed additional parietal, insular and sensorimotor cortical atrophy versus RRMS. At 1-year versus baseline, additional frontal and temporal cortical thinning was detected in RRMS patients, while a widespread CTh reduction was found in PMS patients (significant at time-by-group interaction vs RRMS). In MS, baseline fronto-parietal atrophy correlated with more severe disability and higher lesion volume. Baseline inferior parietal CTh decrease and 1-year temporal cortical thinning correlated with more severe disability.

Conclusion: Parieto-temporal baseline CTh abnormalities and thinning pattern over time characterized the main MS clinical phenotypes and were associated with 1-year disability worsening.