Evoked potential abnormalities in RRMS patients are improved under natalizumab therapy

Thus far, the direct impact of natalizumab (Tysabri ®) on functional parameters of nerve conduction assessed by evoked potentials (visual (VEP), somatosensory (SEP) and motor evoked potentials (MEP)) has not been investigated. VEP, MEP and SEP data were measured in a cohort of 44 relapsing-remitting multiple sclerosis (RRMS) patients and analyzed 12 months prior to initiation of natalizumab treatment, at the timepoint of treatment initiation and one year later. Sum scores (VEP, MEP, SEP) were evaluated and correlated with the expanded disability status scale (EDSS) and EDSS functional scores. Improvement of the VEP sum score was found in 33% of natalizumab treated patients but only in 9% of the same patients prior to treatment (p=0.041). A comparable situation was found for SEP (improvement: 32% versus 5%; worsening: 11% versus 37%; p=0.027). For MEP no significant differences were seen (improvement: 10% versus 18%; worsening: 5% versus 29%; p=0.60). The correlation between VEP/SEP and EDSS functional scores was even higher while the general tendency and statistical significance was comparable to the EDSS data. Natalizumab had a comparable effect on both amplitude and latency changes. In summary, EP recordings (VEP=SEp≥ MEP) have the capacity to demonstrate treatment effects of natalizumab on a functional level. Natalizumab therapy increases the percentage of patients showing stable or even ameliorated electrophysiological parameters in the investigated functional systems. Evoked potentials might therefore be considered a useful tool in order to evaluate drug effects in clinical practice.