Visual evoked potential in multiple sclerosis and neuromyelitis optica spectrum disorder: A comparative study

Abstract

Objectives The neuromyelitis optica spectrum disorder (NMOSD) was differentiated from relapsing-remitting multiple sclerosis (MS) by clinical, laboratory and physiopathological findings, including the presence of anti-aquaporin 4 (AQP4-Ab) antibody. Visual evoked potentials (VEP) are often used for the diagnosis of MS. However, the features of these VEP in the NMOSD have not been studied in detail. Our aim is to determine the epidemiological, clinical and especially neurophysiological (VEP) differences between MS and NMOSD. Methods Fourteen patients with NMOSD and 14 patients with RRMS were included in this study. The patients’ neurological symptoms and signs were examined and their VEP recorded. Results The mean age at onset of the patients with NMOSD was 43.21 years, which was older than that of the patients with RRMS (P = 0.017). The ratio of female patients with NMOSD was higher than that with RRMS (P = 0.012). The periods from onset to diagnosis were similar between the two groups. The prevalence of bilateral visual disturbance was higher in the NMOSD group (78.57%). Patients with RRMS presented a P100 latency and/or amplitude impairment in 6 asymptomatic eyes (21.42%). While in patients with NMOSD, there were 4 asymptomatic eyes that had all normal VEP. In VEP, 17.9% of NMOSD eyes presented no response and only 3.6% of MS eyes and the P100 amplitude impairment was predominant in NMOSD. Conclusion Sometimes, it remains critical to differentiate a MS from an NMOSD especially when the specific antibody is negative. VEP results can point to one of the two diseases even at an early stage.