Cognitive progression independent of relapse activity in different multiple sclerosis phenotypes

Introduction: It is unclear whether patients with the progressive form of the disease present a distinct pattern of cognitive impairment (CI); whether the progression independent of relapse activity (PIRA) impacts CI; and how different is PIRA across relapsing-remitting (RRMS) and progressive MS (PMS). 

Objectives: To assess the trajectories of cognitive/clinical decline in RRMS/PMS patients, also evaluating the association of neuroimaging parameters and reserve, and also characterizing according to PIRA.

Methods: Longitudinal four-year follow-up that was conducted in the MS center of a tertiary hospital. Fifty-four patients were enrolled (30 PMS, 24 RRMS) who underwent brain MRI, clinical and neuropsychological evaluation (BRB-N, Tower of London Test and Boston Naming Test) at baseline (time 1) and after 4 years (time 2). Cortical thickness and subcortical volumes evaluation were performed using Freesurfer. Spinal Cord Toolbox was used to evaluate the area of spinal cord (SC) section at the C2 level.  

Results: At time 1, 37.2% of the individuals presented CI and 52.4% at time 2. There were no major differences between the RMS/PMS groups in the evolution of clinical, cognitive and radiological variables after 4 years of follow-up. For the worsening of clinical disability, the best predictive factors were the SC area  and the striatum volume. For cognitive deterioration, striatum volume and cortical thickness were the best predictors. We observed PIRA in 65.11% of the patients: CI was observed in 46.5% at time 1 and 59.2% at time 2 and there was no major differences between MS groups in the clinical, cognitive or neuroimaging variations.

Conclusions and Relevance: There were no major differences between MS groups in the trajectories of clinical, cognitive and neuroimaging variables, pointing to a uniformity in the clinical courses of the disease. The similar trajectories across RRMS/ PMS groups with PIRA may suggest a common mechanism driving progression.