Functional-structural assessment of the optic pathways in patients with optic neuritis.

Abstract

The pattern-reversal visual evoked potential (pVEP) is widely used for the diagnosis of Optic Neuritis (ON), but this method has some limitations. The aim of this study was to examine the added value of multifocal visual evoked potentials (mfVEP) and spectral-domain optical coherence tomography (SD-OCT) in the diagnosis of ON in patients that exhibit a normal pVEP. Thirty-three patients with a history of having ON and 30 sex- and age-matched healthy controls (HC) were investigated. We included patients who were suspected of having a first-time ON and in whom pVEP showed normal results. Both eyes of the patients and HC were systematically investigated with SD-OCT, visual acuity, pVEP and mfVEP. The ON-affected eyes of the patients were compared with only one randomly selected eye per person in the HC group. The fellow "non-affected" eye of patients was held as a separate group. Statistical analyses were performed (including t test, Spearman's rank-order correlation test) using SPSS Statistics, Version 24.0. A significant difference was found in OCT mean retinal nerve fibre layer thickness (RNFLt) between patients and HC (p = 0.013) (i.e. 84.24 (± 17.00) μm versus 93.48(± 6.44) μm). An association was detected in patients between mean inter-eye asymmetry of the RNFLt and global (averaged) mfVEP amplitude (r = 0.565, p = 0.002). When analysing mfVEP signals from sectors in the upper hemifield, a significant difference was found in mean mfVEP amplitude between patients and HC (p = 0.005). Abnormality is potentially measurable (via reduced RNFLt and focal analyses with mfVEP amplitude) in patients suspected of having a first episode of ON where pVEP reports no abnormality. The mfVEP and SD-OCT may together be of value as supplementary tools in diagnosing ON in this patient group.