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

•Combined evoked potentials allow prediction of the development of medium-term disability in small groups of patients with early multiple sclerosis with a R2 of 0.5.•Predictability of MS disability is influenced by the timing of the EP investigation and is best possible if the EP tests are performed in the relapse-free interval.•The results underscore the importance of mechanisms of recovery for prognosis.

ObjectiveLittle 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.MethodsTwo 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 EDSST2 and a baseline EP compound measure (s-EP-QT0) for each group.ResultsMedian EDSST0 was 3.0 for Group 1 and 1.5 for Group 2. Mean disease durations were 2.0 and 2.8 years, respectively. Median EDSST2 was 2.0 for both groups. The s-EP-QT0 significantly predicted EDSST2 (R2 = 0.47) for patients in Group 2, but not for patients in Group 1 (R2 = 0.07).ConclusionIn 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.SignificanceThis suggests a role of multimodal EPs in prediction of MS disability if performed in the relapse-free interval.