Axonal loss in multiple sclerosis: a morphological and functional analysis of retinal nerve fibbers

Abstract

AbstractPurpose The main purpose of this work was to study the retinal nerve fibber layer (RNFL) atrophy by optic coherence tomography in different subtypes of multiple sclerosis (MS) patients and to compare these results with electrophysiological examinations.Methods Fifty eight patients were included, 43 suffered from a relapsing‐remitting MS and 15 suffered from a progressive MS. We studied all eyes according 2 groups, MS eyes with a history of acute optic neuritis (MS‐ON eyes, n=39) and MS eyes without history of optic neuritis (MS‐non ON eyes, n=76). Electrophysiological exams were performed in all MS patients: (1) visual letter acuity (Snellen Charts), (2) visual evoked potentials, (3) pattern electroretinogram and (4) perimetry (Metrovision France). Retinal nerve fibber thickness were measured by Optical coherence tomography (OCT; fast RNFL thickness protocol).Results The rate of MS‐ON eyes and MS non‐ON eyes were not different between the 2 subtypes of MS (p>0.05, Fisher test). Progressive MS demonstrated a mean value decrease of RNFL thickness particularly in inferior quadrant compared to relapsing‐remitting MS (respectively, 92.9 um and 98.7 um for mean value, p= 0,04; 117.7 um and 127.4 um for inferior RNFL thickness, p=0,05). An increased P100 latency and decreased P50 and N95 amplitude were noted in MS‐non ON eyes compared to MS‐ON eyes (respectively p=0,013; p=0,026 and p=0,003).Conclusion This study seemed to illustrate a potential axonal loss in MS patients through these structural and functional differences between progressive MS and relapsing‐remitting MS optic nerves. The N95 amplitude of non‐affected eyes measurement appeared to be a new index to diagnose early progressive MS.