Retinal Layer Thinning After Optic Neuritis Is Associated With Future Relapse Remission in Relapsing Multiple Sclerosis

BACKGROUND AND OBJECTIVES: Remission of relapses is an important contributor to both short- and long-term prognosis in relapsing multiple sclerosis (RMS). In MS-associated acute optic neuritis (MS-ON), retinal layer thinning measured by optical coherence tomography (OCT) is a reliable biomarker of both functional recovery and the degree of neuroaxonal damage. However, prediction of non-ON relapse remission is challenging. We aimed to investigate whether retinal thinning after ON is associated with relapse remission after subsequent non-ON relapses. METHODS: For this longitudinal observational study from the Vienna MS database, we included patients with MS with (1) an episode of acute ON, (2) available spectral domain OCT scans within 12 months before ON onset (OCT(baseline)), within 1 week after ON onset (OCT(acute)), and 3–6 months after ON (OCT(follow-up)), and (3) at least 1 non-ON relapse after the ON episode. Subsequent non-ON relapses were classified as displaying either complete or incomplete remission based on change in the Expanded Disability Status Scale score assessed 6 months after relapse. Association of retinal thinning in the peripapillary retinal nerve fiber layer (ΔpRNFL) and macular ganglion cell and inner plexiform layer (ΔGCIPL) with incomplete remission was tested by multivariate logistic regression models adjusting for age, sex, disease duration, relapse severity, time to steroid treatment, and disease-modifying treatment status. RESULTS: We analyzed 167 patients with MS (mean age 36.5 years [SD 12.3], 71.3% women, mean disease duration 3.1 years [SD 4.5]) during a mean observation period of 3.4 years (SD 2.8) after the ON episode. In 61 patients (36.5%), at least 1 relapse showed incomplete remission. In the multivariable analyses, incomplete remission of non-ON relapse was associated with ΔGCIPL thinning both from OCT(baseline) to OCT(follow-up) and from OCT(acute) to OCT(follow-up) (OR 2.4 per 5 μm, p < 0.001, respectively), independently explaining 29% and 27% of variance, respectively. ΔpRNFL was also associated with incomplete relapse remission when measured from OCT(baseline) to OCT(follow-up) (OR 1.9 per 10 μm, p < 0.001), independently accounting for 22% of variance, but not when measured from OCT(acute) to OCT(follow-up.) DISCUSSION: Retinal layer thinning after optic neuritis may be useful as a marker of future relapse remission in RMS.