Early abnormalities of evoked potentials and future disability in patients with multiple sclerosis

Abstract

Evoked potentials (EP) have a role in making the diagnosis of multiple sclerosis (MS) but their implication for predicting the future disease course in MS is under debate. EP data of 94 MS patients examined at first presentation, and after five and ten years were retrospectively analysed. Patients were divided into two groups in relation to the prior duration of disease at the time point of first examination: group 1 patients (n=44) were first examined within two years after disease onset, and group 2 patients (n=50) at later time points. As primary measures sum scores were calculated for abnormalities of single and combined EP (visual (VEP), somatosensory (SEP), magnetic motor evoked potentials (MEP)). In patients examined early after disease onset (group 1), a significant predictive value for abnormal EP was found with MEP and SEP sum scores at first presentation correlating significantly with Expanded Disability Status Scale (EDSS) values after five years, while the VEP sum score was not. The cumulative number of abnormal MEP, SEP and VEP results also indicated higher degrees of disability (EDSS > or = 3.5) after five years. Combined pathological SEP and MEP findings at first presentation best predicted clinical disability (EDSS > or = 3.5) after five years (odds ratio 11.0). EP data and EDSS at first presentation were not significantly linked suggesting that EP abnormalities at least in part represented clinically silent lesions not mirrored by EDSS. For patients in later disease phases (group 2), no significant associations between EP data at first presentation and EDSS at five and ten years were detected. Together with clinical findings and MR imaging, combined EP data may help to identify patients at high risk of long-term clinical deterioration and guide decisions as to immunomodulatory treatment.