A longitudinal study of cognitive function in multiple sclerosis: is decline inevitable?

Background Numerous cross-sectional studies report cognitive impairment in multiple sclerosis (MS), but longitudinal studies with sufficiently long-term follow-up are scarce. Objective We aimed to investigate the cognitive 10-year course of a cohort of MS patients. Methods 59 patients with clinically isolated syndrome (CIS) or relapsing-remitting (RR) MS were evaluated with Rao's Brief Repeatable Battery of Neuropsychological Tests at baseline and follow-up (at least 10 years later). They constituted 47.2% of 124 consecutive CIS and RRMS patients originally evaluated at baseline. Patients assessed at follow-up were well matched for baseline clinical characteristics with dropouts. Results The proportion of MS patients with overall cognitive impairment was increased by 10% within the 10-year period. When grouped on the basis of impairment in specific cognitive domains at baseline, patients originally impaired showed improvement at follow-up, while the opposite trend was observed for patients non-impaired at first assessment. A detailed case-by-case investigation revealed mixed evolution patterns, several patients fail in fewer domains at follow-up compared to baseline or failing at different domains at follow-up compared to baseline. Conclusions This study suggests a more fluid picture for the evolution of cognitive function in a subgroup of MS patients and contradicts the concept of an inevitable, progressively evolving "dementia".