Measuring evoked responses in multiple sclerosis

Abstract

Evoked potentials (EPs) have been widely utilised in Multiple Sclerosis (MS) patients to demonstrate the involvement of sensory and motor pathways. Their diagnostic value is based on the ability to reveal clinically silent lesions and to objectivate the central nervous system damage in patients who complain frequently of vague and indefinite disturbances which frequently occurs in the early phases of the disease. The advent of magnetic resonance imaging (MRI) techniques has greatly reduced the clinical utilisation of EPs, which is not fully justifiable, as the information provided by EPs are quite different from those provided by MRI. The abnormalities of evoked responses reflect the global damage of the evoked nervous pathway and are significantly correlated with the clinical findings, while the vast majority of MRI lesions are not associated to symptoms and signs. Transversal and longitudinal studies have demonstrated that EP changes in MS are more strictly related to disability than MRI lesion burden. On the contrary, MRI is more sensitive than EPs in revealing the disease activity. Evoked responses modifications observed in MS are not disease-specific; moreover longitudinal studies showed latency and morphology changes of evoked responses not always related to clinical changes. Such a dissociation can be explained both by technical factors and by subclinical disease activity. To reduce the negative impact of technical aspects, only reproducible parameters of the evoked responses should be used to monitor disease evolution and therapeutic interventions.

Prediction of long-term disability in multiple sclerosis

“…By comparison, prospectively acquired follow-up of EP findings and clinical course in other MS cohorts has ranged from 2-3 years. 11,[17][18][19][20] The present results are in agreement with the study of Leocani et al 18 and Jung et al 19 in which however the EP results were transformed to ordinally scaled data and also included qualitative assessments of potentials in spite of their high inter-rater variability 21 and the problem of downgrading numerical information to an ordinal level. 22 The latter procedure might be the reason for the absence of predictive power of EPs in the study of O'Connor et al 17 A comparison with the study by Kallmann et al 23 is more difficult, due to its retrospective design.…”

Do evoked potentials contribute to the functional follow-up and clinical prognosis of multiple sclerosis?

“…Conduction time, a demyelination marker, is the main electrophysiological characteristic described so far in many EP studies on patients with clinically definite MS, due to its high sensitivity and good reproducibility [18,21,29]. Though sometimes included in ordinal scores [11,19], amplitude has rarely been used as an individual score because of its higher variability even in normal subjects.…”

Improved Characterization of Visual Evoked Potentials in Multiple Sclerosis by Topographic Analysis

“…For monitoring the disease course, the use of only the most robust EP components has been recommended (Comi et al 1999) and has been found useful (Fuhr et al 2001; Schlaeger et al 2012a, b, 2013). In the present study, the P100 latency shows highest test–retest reliability in the same range as reported previously (Meienberg et al 1979; Thomae et al 2010) and is the main factor in predicting diagnostic group and history of ON.…”