Early cognitive dysfunction as a marker for the poor course of multiple sclerosis: a prospective 12-year follow-up

Abstract

Owing to the advent of current methods for the prevention of exacerbations of multiple sclerosis (MS), it has become possible to increase the period to the development of obvious persistent cerebellar and motor disorders that mainly lead to disability. This makes it possible to focus on less evident and latent symptoms, in particular on cognitive impairment (CI) that are recorded since the diagnosis of MS and slowly progress over time.Objective: to assess the prognostic capabilities of the Paced Auditory Serial Addition Test (PASAT) to identify a group of patients with early disability (10-year risk of reaching 6.5 Expanded Disability Status Scale (EDSS) scores.Patients and methods. The paper presents the data of a 12-year (2005–2018) follow-up of 36 patients having MS with and without mild CI. The patients' mean age at the time of study inclusion was 31.7 years (confidence interval (CI) 29.2–34.1; α<0.05); the disease duration was 4.69 months (CI 3.31–6.08; α<0.05); the EDSS scores averaged 2.51 (CI 2.23–2.82; α<0.05). Severe disability (6.5 EDSS scores) was observed in 75% of cases in the presence of mild CI and in 25% of cases in the absence of mild CI; it occurred an average of 118.3 (CI 93.1–143.4; α<0.05) and 141.2 (CI 126.0–156.5; α<0.05) months later, respectively.Results and discussion. The findings suggest that the patients with MS in the presence of impaired information processing speed and decreased attentional function (failure to complete more than 25% of the PASAT tasks) had a significantly greater risk for persistent disability than the patients without CI or with its minimal manifestations. Limitation in walking function (4.5 EDSS scores) occurred an average of 3.5 years earlier, and its significant limitation (6.5 EDSS scores) did 2 years earlier in the severe CI group, which may be important in planning therapy.Conclusion. The presence of CI in early MS is likely to have a prognostic value in relation to the course of the disease.