Functional and structural changes in the visual pathway in multiple sclerosis

Abstract

IntroductionMultiple sclerosis (MS) is a heterogeneous disease with an unpredictable course. Visual pathway is a target of the disease and may reflect mechanisms that lead to disability. Structural and functional changes in the visual pathway may be studied by noninvasive techniques such as optical coherence tomography (OCT), visual evoked potentials (VEP), or B‐mode transorbital sonography (TOS).ObjectivesThe aim is to assess changes in the visual pathway in eyes of MS patients with and without a history of optic neuritis over a 3‐year period and to explore their relationship with disability.Materials and MethodsIn total, 112 eyes from 56 patients with relapsing MS were recruited: 29 with, and 83 without a history of ON (hON and nhON, respectively). Several parameters were measured by OCT, VEP, and TOS. Baseline measurements were also compared to 29 healthy controls. At 36 months, measurements were repeated in all eyes.ResultsAt baseline, all tests showed significant differences in optic nerve structure and function in both patient cohorts in all the parameters studied, suggestive of more impairment of the visual pathway among the hON cohort. OCT showed significant differences between healthy controls and the nhON cohort. At 36 months, the nhON cohort showed significant changes by OCT, VEP, and TOS suggestive of further visual pathway impairment. OCT measurements also correlated with baseline EDSS among the nhON cohort.ConclusionsOCT is the most suitable technique and outperforms VEP and TOS to detect subclinical damage in the visual pathway. It discriminated MS patients from healthy controls and showed a progressive decline in optic nerve thickness over time among these patients.

OCT Variability Prevents Their Use as Robust Biomarkers in Multiple Sclerosis

“…2,40 Our results agree with previous reports showing thinner pRFNL and FT in MS patients w/w ON history. 2,3,11 However, we did not find differences in the pRFNL between healthy and MS eyes without ON history (thinning lower than 2 μm), although it has been previously reported. 3,[40][41][42] The small difference between pRFNL of healthy versus MS patients without ON history is close to previously reported pRFNL repeatability achieved For personal use only.…”

“…In fact, they obtain normal mean values of 86.8±21.4 µm to 104.7±12.5 µm while our values are lower even though our population of normal subjects is significantly younger (Table 1). The Cracelen-Gadea et al report 11 is of particular interest because it used the Spanish population of similar ages (35.0±5.84), with MS patients and because it is carried out with same equipment (Topcon SD 3D OCT). The pRNFL mean value in normal controls was 104.28±8.5 µm, in MS patients without ON it was 97.31±13.0 µm and in MS patients with past history of ON it was 93.5±11.8 µm.…”

“…10 Furthermore, detectable retinal axonal loss is assumed to occur early in the course of the MS disease. 11 Currently SD-OCT is considered to be the most suitable technique and outperforms Visual Evoked Potential (VEP) and B-mode transorbital sonography (TOS) to detect subclinical damage discriminating MS patients from healthy controls. It also shows a progressive decline in optic nerve thickness over time in MS patients.…”

“…It also shows a progressive decline in optic nerve thickness over time in MS patients. 11 Therefore OCT has been accepted as a non-invasive method able to quantify intraretinal layer volumes and it is widely used to quantify the peripapillary retinal nerve fiber layer (pRNFL) and foveal and macular thickness (FT/MT), providing a clinical objective method for monitoring axonal injury in MS and other neurodegenerative diseases. 11,12 However, it does not seem that at the clinical level this ancillary test has been incorporated in a routine way in most hospitals.…”

Visual Evoked Potentials in Joubert Syndrome: A Suggested Useful Method for Evaluating Future Approaches Targeted to Improve Visual Pathways’ Function

“…Maria et al [ 36 ], reporting neuroradiologic data of a cohort of 46 JS patients, suggested an involvement of the myelination process in 33% of cases. This process is crucial for normal neural conduction along visual pathways, and it is well known that in demyelinating neurodegenerative diseases (i.e., multiple sclerosis), there is a delay in neural conduction along the visual pathways detectable by abnormal VEP responses (see Carcelén-Gadea et al for a review [ 37 ]). Thus, it is conceivable that also in JS patients there could be an abnormal myelination of nerve fibers forming the visual pathways, leading to the observed VEP abnormalities.…”