Evoked potentials and other guiding factors of conversion from radiologically isolated syndrome to definite multiple sclerosis

Abstract

Objective: Radiologically Isolated Syndrome (RIS) has become a popular subject recently with quite a number of follow-up and other clinical studies being done. A consensus on the approach to the patient with RIS is being tried to be established. The aim of our study was to assess the role of visual evoked potential (VEP) and somatosensory evoked potential (SEP) as a guiding factor for the conversion from Radiologically Isolated Syndrome (RIS) to definite Multiple Sclerosis (MS). Material and methods: 49 RIS patients who were referred to GATA Haydarpasa Training Hospital Neurology Department between 2011-2015. All of the patients fullfillied the 2009 Okuda criteria for RIS and other differential diagnosis were excluded accordingly. VEP and SEP examinations made during the pre-MS RIS period were scanned retrospectively. For the VEP examination, the P100 latency and amplitudes, for the SEP examination, the P40 latency and amplitude was analysed. Results: 49 patients were included in this study, the mean time of follow-up was 21,8 months. 63% of patients were female, while 37% were male. The mean age was 31,2 years. Among the four patients with abnormal SEPs, MS developed in three of them (75%) over time. This is statistically significant (p = 0.011). VEP and/or SEP was abnormal in 8 patients and MS developed in 4 (50%) of those (p=0.017). The following factors have a positive statistically significant correlation with conversion to MS: Presence of active plaques (r=0.461, p<0.001), presence of more than 9 plaques (r=0.287, p=0.046), VEP and/or SEP pathologies (r=0.402, p=0.004) and number of plaques (r=0.309, p=0.031). The most important factor for the transformation is the presence of active plaque which increases the risk 8.1-fold. The second important factor seems to be the presence of VEP and/or SEP abnormality, but this factor does not reach statistical significance. Conclusion: In the conversion to MS risk from RIS, VEP- SEP examinations are important and should take its place in the follow-up of these patients.