Prediction of MS disability by multimodal evoked potentials: investigation during relapse or in the relapse-free interval?

Objective: Little is known about optimal timing of multimodal evoked potential (EP)-investigations regarding prediction of MS disability. The aim of this study was to investigate whether timing of EP-investigations during a relapse or in the relapse-free interval influences prediction of MS disability.
Methods: Two groups of MS patients with similar age and gender distributions received visual, motor and somatosensory EPs either during a relapse (Group 1) or in the relapse-free interval (Group 2). Expanded Disability Status Score (EDSS) was obtained at baseline (T0) and year 3 (T2). Linear regression analysis was performed to examine the association between EDSS(T2) and a baseline EP compound measure (s-EP-Q(T0)) for each group.
Results: Median EDSS(T0) was 3.0 for Group 1 and 1.5 for Group 2. Mean disease durations were 2.0 and 2.8 years, respectively. Median EDSS(T2) was 2.0 for both groups. The s-EP-Q(T0) significantly predicted EDSS(T2) (R(2)=0.47) for patients in Group 2, but not for patients in Group 1 (R(2)=0.07).
Conclusion: In early MS the functional remnants of relapses are a better predictor for development of medium-term disability than is the extent of impulse propagation impairment measured during relapse.
Significance: This suggests a role of multimodal EPs in prediction of MS disability if performed in the relapse-free interval.
(Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)