Electrophysiological markers and predictors of the disease course in primary progressive multiple sclerosis

Abstract

Background:

Currently no valid surrogate marker exists for primary progressive multiple sclerosis (PPMS).

Objective:

Our aim was to prospectively investigate multimodal evoked potentials (EPs) as markers and predictors of the disease course in PPMS.

Methods:

Twenty-two PPMS patients were prospectively examined with visual, somatosensory and motor EPs and Expanded Disability Status Scale (EDSS) assessments at baseline (T0) and at six-month intervals over three years. Spearman rank correlation was used to determine the relationship between EP measures and EDSS. The relationship between disease evolution and a numerical score derived from z-transformed EP-latencies (s-EP-Q) and baseline characteristics was further assessed using multivariable linear regression analysis.

Results:

s-EP-Q correlated with EDSS score at all points in time in cross-sectional comparison (0.53≤rs ≤0.68; 0.0007≤p≤0.0232) and also longitudinally by trend (r_s=0.46, p=0.0740). The s-EP-Q_T0 correlated with the EDSS score at year 3 (T6) (r_s=0.77, p<0.0001). The s-EP-Q changes became statistically significant six months before corresponding changes were seen in the EDSS score. EDSS_T6 as predicted by EDSS_T6= −1.027+0.037* age+0.217* s-EP-Q_T0 + 0.695* EDSS_T0 correlated with the observed values (r_s=0.92, p<0.0001).

Conclusions:

Multimodal EPs correlate well with disability in PPMS, and allow some prediction of the disease course over three years. These findings support a role of EPs as surrogate markers in clinical trials in PPMS.