Cognitive impairment differs between primary progressive and relapsing-remitting MS

Abstract

To characterize the cognitive abilities of patients with primary progressive multiple sclerosis (PPMS) and relapsing-remitting multiple sclerosis (RRMS) compared with healthy controls (HCs) matched for age, sex, and education level while considering the different characteristics of PPMS and RRMS and to compare the cognitive patterns of these types of multiple sclerosis. Forty-one patients with PPMS, 60 patients with RRMS, and 415 HCs were recruited in a cross-sectional study. Controls were divided into 20 groups according to age, sex, and education level. Participants were assessed with a large battery of neuropsychological (NP) tests that included a modified version of the Brief Repeatable Battery, the Stroop test, computerized tests from the Test of Attentional Performance battery, the numerical span test, and the Rey Complex Figure. Patients with PPMS performed worse than their matched HCs on nearly all NP tests. Patients with RRMS performed worse than matched HCs on a computerized digit-symbol substitution task and the alertness test, reaction time for visual scanning, and Paced-Auditory Serial Addition Test-3 seconds. Patients with PPMS had worse NP scores and were more impaired in cognitive domains than patients with RRMS. After controlling for Expanded Disability Status Scale score, the results remained unchanged. The patients with PPMS presented with a wide range of cognitive deficits in information processing speed, attention, working memory, executive function, and verbal episodic memory, whereas the impairments in patients with RRMS were limited to information processing speed and working memory compared with their matched HCs. Cognitive deficits were more severe in patients with PPMS than in patients with RRMS.