Effects of acute relapses on neuropsychological status in multiple sclerosis patients

Little is known about neuropsychological status changes in multiple sclerosis (MS) patients experiencing a relapse. The Symbol Digit Modalities Test (SDMT) and MS Neuropsychological Screening Questionnaire (MSNQ) are brief measures of cognitive performance and self-reported status, respectively. We retrospectively identified relapses in subjects participating in the 48-week open-label, safety-extension study of natalizumab (STRATA) to determine if changes in cognitive ability occurred during acute relapses. SDMT and MSNQ were administered prior to infusions. We analyzed SDMT and MSNQ scores pre- and post-relapse in 53 MS patients with relapses (cases) and 115 MS patients without relapses (controls) matched on age, gender, baseline SDMT and time from study initiation. ANOVA and GLM were used to compare cases versus controls overall, and stratified by EDSS cerebral functional status (cFS) scores. SDMT change pre- to post-relapse in cases was significantly lower than difference between similar time points in controls (p = 0.003). When comparing visit 2 (two visits pre-relapse) to visit 1 (first visit post-relapse), MSNQ change was significantly different between cases and controls (p = 0.012). For cFS ≤ 1, the change in SDMT was significantly different between cases and controls but not for cFS ≥ 2. These results confirm the involvement of cognitive function during some MS relapses suggesting the SDMT or MSNQ can be used to identify transitory neuropsychological status changes and cognitive relapses.