Peripapillary retinal nerve fiber layer thickness measured by optical coherence tomography in different clinical subtypes of multiple sclerosis

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BackgroundMultiple sclerosis (MS) is a chronic inflammatory demyelinating autoimmune disease of the central nervous system (CNS) with axonal degeneration as major determinant of neurological disability. Assessment of unmyelinated retinal nerve fibers using optical coherence tomography (OCT) may be useful for diagnosing the onset and rate of progression of neurodegeneration. ObjectiveTo assess the incidence and severity of damage of the peripapillary retinal nerve fiber layer (RNFL) in two different MS subtypes: non-progressive [Prog(-)MS] and progressive [Prog(+)MS]. Methods48 patients (96 eyes) with MS were included: 13 males, 35 females; aged 22–62 years (mean 38.8; SD ± 10.02) in two subgroups: 26 Prog(-)MS and 22 Prog(+)MS. 3 subtypes of Prog(+)MS were identified by neurologist, according to Lublin criteria: 3 patients had PPMS (14%), 7 had SPMS(32%), 12 had PRMS(54%). RRMS subtype was considered a non-progressive phenotype, designated as Prog(-)MS. All 22 patients with progressive MS phenotypes were included in one group, designated as Prog(+)MS. Progressive disease can be defined over 1 year. The expanded EDSS score was determined by the treating MS specialist and confirmed by the study investigators through the records review. Definition included a 3-strata progression magnitude in the absence of a relapse, confirmed after 3 months within the leading Functional System and required an Expanded Disability Status Scale step≥4 and pyramidal score≥2. 11 Prog(-)MS (16 eyes) and 10 Prog(+)MS (13 eyes) patients had a history of optic neuritis (ON). EDSS score was 1.5–6.5 (mean 3.83 ± 1.62) in the Prog(+)MS group and 1.0–3.5 (mean 1.40 ± 0.57) in the Prog(-)MS. Control group: 31 healthy volunteers (3 males, 28 females), aged 20–62 years (mean 37.4 ± 10.88). Peripapillary RNFL thickness was measured around the optic nerve head (ONH) using spectral-domain OCT (Topcon OCT 1000 MarkII, FastMap v. 3.40, Topcon, Japan). Scans were obtained according to OSCAR-IB consensus criteria.The generalized estimating equation model (GEE) was used in the statistical analysis to assess differences in RNFL thickness between Prog(-)MS and Prog(+)MS patients, taking into consideration history of ON, EDSS score, immunomodulatory therapy, MS progression, MS duration, age and gender.The protocol was approved by the Ethical Committee of the Medical Centre of Postgraduate Education, Warsaw, Poland and informed consent was obtained from all subjects. ResultsThere was a significant difference between Prog(-)MS and Prog(+)MS groups for mean, nasal and superior quadrant of RNFL thickness. For individuals with a history of ON, significant differences were found between the two MS phenotypes regardless of RNFL thickness measurements. ConclusionsA significant correlation was established between RNFL thickness and progression of neurodegeneration in MS patients with no regard to history of ON. RNFL thickness may be considered a MS biomarker and potential diagnostic tool for assessment of disease progression.