Combined evoked potentials as markers and predictors of disability in early multiple sclerosis

Objective: To prospectively assess combined evoked potentials (EP) as markers and predictors of the disease course of early MS over 3 years.

Methods: Fifty patients in the early phase of relapsing remitting MS prospectively received visual, somatosensory and motor EP and EDSS assessments at baseline (T1) and at 6 months intervals during 3 years. Spearman rank correlation was used to determine the relationship between z-transformed EP-latencies (z-EPL) and EDSS. Multivariable linear regression was performed to predict EDSS at year 3 (T7) in function of z-EPL(T1). Validity of the models was assessed using group cross-validation.

Results: At each of the seven points in time, EDSS correlated with the sum of z-EPL (0.64 ≤ rho ≤ 0.79, p<0.001). The change of the sum of z-EPL(T7-T1) correlated with the change of EDSS(T7-T1) (rho=0.51, p=0.001). EDSS(T7) as predicted by the sum of z-scores of EP latencies or by the number of pathological EP results at baseline correlated with the observed clinical values after 3 years (rho>0.70, p<0.001, for both measures).

Conclusions: Multimodal EPs correlate well with clinical disability in cross-sectional and longitudinal comparison in early MS and allow prediction of disease evolution over 3 years.

Significance: EPs seem well suited as markers of the disease course in early MS in clinical trials and bear potential for supporting decision-finding in individual patients.