Detecting isolated cognitive relapses in persons with MS.

Abstract

The existence of isolated cognitive relapses (ICRs) in persons with MS (PwMS) has been debated. To examine relapses with decline on Symbol Digit Modalities Test (SDMT) but no change on Expanded Disability Status Scale (EDSS). This 3-year prospective cohort study identified PwMS experiencing a relapse with decrease on SDMT. Participants with SDMT decline/stable EDSS were labeled "ICR," while those with a corresponding decrease on EDSS were classified "Relapse with Cognitive Decline (RCD)." Two definitions of SDMT decline were explored: (1) ⩾ 8 points, and (2) ⩾ 4 points. Logistic regression was used to analyze the relationship between ICR and RCD. The full cohort had 592 participants: 83 experienced relapses; 22 (26.5%) had an SDMT decrease of ⩾ 8 points; 14 (63.6%) met ICR criteria. Logistic regression (X2(1) = 5.112, p = 0.024) using demographics and disease characteristics explained 28.4% of the variance in ICR versus RCD. Only the MS Neuropsychological Questionnaire was associated with ICR (odds ratio (OR): 8.6; 95% confidence interval (CI): 1.1-16.4) 40 relapsing participants with SDMT decrease of ⩾ 4 points were identified: 26 (65%) had a stable EDSS (ICR). Logistic regression did not find any variable predictive of ICR. This prospective study demonstrates evidence of ICR in PwMS.