Early disability in ambulatory patients with multiple sclerosis: optical coherence tomography versus visual evoked potentials, a comparative study

Background Multiple sclerosis (MS) is a common cause of neurological disabilities in adults and commonly affects the visual pathway. The objective of this study is to assess and compare the sensitivity of visual evoked potentials (VEP) and optical coherence tomography (OCT) as measures of early disability inambulatorypatients with MS. Methods Forty-four patients with MS with Expanded Disability Status Scale (EDSS) of <= 4.5 (ambulatory patients) and 14 healthy controls participated in this study. Patients were classified into 3 groups according to EDSS. Patients with EDSS of 0-1.5 formed the "No disability," patients with EDSS of 2-3 formed the "Minimal to mild disability," and finally patients with EDSS of 3.5-4.5 formed the "Moderate to significant disability" groups. N75/P100 amplitude, P100 latency, retinal nerve fiber layer (RNFL) thickness, and ganglion cell layer complex (GCLC) thickness were measured. Results Patients showed significantly lower N75/P100 amplitude, higher P100 latency, lower RNFL, and GCLC thicknesses compared to controls. However, there were non-significant changes in P100 latency, N75/P100 amplitude, and GCLC thickness among the 3 groups for both patients with and without history of optic neuritis (ON). On contrary, RNFL thickness was significantly different between the three groups for both patients with and without history of ON. Factorial ANOVA revealed non-significant disability x History of ON interaction. Conclusion Compared to VEP parameters, RNFL thickness was a sensitive correlate with the various degrees of early disability in fully ambulatory patients with MS whatever the history of ON.