Functional and structural changes in the visual pathway in multiple sclerosis

Retinal optical coherence tomography measures in multiple sclerosis: a systematic review and meta-analysis

Spectral domain-optical coherence tomography plays a crucial role in the early detection and monitoring of multiple sclerosis (MS) pathophysiology. We aimed to quantify differences in retinal layer measures among different groups of MS and explored different variables that correlate with retinal measures. This study was reported according PRISMA guidelines. A comprehensive search was done across PubMed, Embase, and Google Scholar. The mean difference in thickness of retinal layers and macular volume was assessed. Meta-regression was done to assess the sources of heterogeneity. A total of 100 articles were included in the meta-analyses. The peripapillary retinal nerve fiber layer (pRNFL) thickness significantly decreased in the MSON (MD: -16.44, P < 0.001), MSNON (MD: -6.97, P < 0.001), and PMS (MD: -11.35, P < 0.001) versus HC. The macular RNFL was lower among the MSON (MD: -6.24, P = 0.013) and MSNON (MD: -3.84, P <0.001) versus HC. Macular ganglion cell layer and inner plexiform layer (GCIPL) was thinner among MSON (MD: -14.83, P <0.001), MSNON (MD: -6.38, P < 0.001), and PMS (MD: -11.52, P < 0.001) compared with control eyes. Inner nuclear layer (INL) was higher in the MSON (MD: 0.49, P < 0.001) versus HC. Outer nuclear layer (ONL) thickness significantly lower in the MSNON (MD: -1.15, P = 0.019) versus HC. Meta-regression showed that disease duration, age, EDSS score, and percentage of patients taking DMT are all negatively correlated with pRNFL and GCIPL thickness; however, female gender was correlated with less atrophy. As conclusion, the study highlights substantial thinning in the pRNFL and macular GCIPL between MS versus controls. INL as valuable parameter for capturing inflammatory disease activity.

Combination among VEP, OCT and TCD data in patients with relapsing-remitting multiple sclerosis during attack-free period

AIMS

Multiple sclerosis (MS) is characterized by inflammation, demyelination, glial cell pathology and axonal injury in the central nervous system, and also progressive axonal loss of the optic nerve in cases with optic neuritis (ON). The previous transcranial Doppler (TCD) investigations suggest cortical hyperreactivity in patients with relapsing-remitting Multiple sclerosis (RRMS). We investigated the effect of ON involvement on visual reactivity.

MATERIAL AND METHODS

One hundred thirty patients with RRMS during attack-free period and 12 healthy subjects were enrolled to the study. Visual evoked potential (VEP), optic coherence tomography (OCT) and TCD examinations of all subjects were performed.

RESULTS

Cerebrovascular reactivity measured with breath holding (BH) test was found to be normal. VEP amplitude, visual reactivity and peripapillary retinal nerve fibre layer (pRNFL) measurements were found to be low in patients with ON involvement, whereas VEP latencies were long. Visual reactivity was negatively correlated with VEP amplitude and RFNL measurements, and positively correlated with VEP latency.

CONCLUSIONS

The present study supports that cerebrovascular reactivity is preserved in patients with RRMS except for attacks, and neurovascular reactivity is increased in patients without ON involvement.

Optical coherence tomography (OCT) measurements and disability in multiple sclerosis (MS): A systematic review and meta-analysis

BACKGROUND

Studies have demonstrated that people with multiple sclerosis (pwMS) experience visual impairments and neurodegenerative retinal processes. The disability progression in pwMS may be associated with retinal changes assessed with optical coherence tomography (OCT). This meta-analysis aims at synthesizing the correlations between OCT measurements of disability in pwMS.

METHODS

We systematically searched four databases (PubMed/MEDLINE, Embase, Scopus, and Web of Science) from inception to November 2022, then conducted a meta-analysis using a random effects model to determine the pooled correlation coefficient(r) between OCT measurements and disability scales by R version 4.2.3 with the meta version 6.2-1 package.

RESULTS

From 3129 studies, 100 studies were included. Among 9051 pwMS, the female-to-male ratio was 3.15:1, with a mean age of 39.57 ± 6.07 years. The mean disease duration and Expanded Disability Status Scale (EDSS) were 8.5 ± 3.7 and 2.7 ± 1.1, respectively. Among the pooled subgroup analyses, macular ganglion cell inner plexiform layer (mGCIPL) in patients with relapsing-remitting (pwRRMS) and peripapillary retinal nerve fiber layer (pRNFL) in patients with progressive MS (pwPMS) had strong correlations with EDSS, r = -0.33 (95% CI: -0.45 to -0.20, I2 = 45%, z-score = -4.86, p < 0.001) and r = -0.20 (95% CI:-0.58 to 0.26, I2 = 76%, z-score = -0.85, p = 0.395), respectively. According to subgroup analysis on pwMS without optic neuritis (ON) history, the largest correlation was seen between EDSS and macular ganglion cell complex (mGCC): r = -0.39 (95% CI: -0.70 to 0.04, I2 = 79%, z-score = -1.79, p = 0.073).

CONCLUSION

OCT measurements are correlated with disability in pwMS, and they can complement the comprehensive neurological visit as an additional paraclinical test.

Evaluation of multiple sclerosis severity using a new OCT tool

PURPOSE

To assess the ability of a new posterior pole protocol to detect areas with significant differences in retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) thickness in patients with multiple sclerosis versus healthy control subjects; in addition, to assess the correlation between RNFL and GCL thickness, disease duration, and the Expanded Disability Status Scale (EDSS).

METHODS

We analyzed 66 eyes of healthy control subjects and 100 eyes of remitting-relapsing multiple sclerosis (RR-MS) patients. Double analysis based on first clinical symptom onset (CSO) and conversion to clinically definite MS (CDMS) was performed. The RR-MS group was divided into subgroups by CSO and CDMS year: CSO-1 (≤ 5 years) and CSO-2 (≥ 6 years), and CDMS-1 (≤ 5 years) and CDMS-2 (≥ 6 years).

RESULTS

Significant differences in RNFL and GCL thickness were found between the RR-MS group and the healthy controls and between the CSO and CDMS subgroups and in both layers. Moderate to strong correlations were found between RNFL and GCL thickness and CSO and CDMS. Furthermore, we observed a strong correlation with EDSS 1 year after the OCT examination.

CONCLUSIONS

The posterior pole protocol is a useful tool for assessing MS and can reveal differences even in early stages of the disease. RNFL thickness shows a strong correlation with disability status, while GCL thickness correlates better with disease duration.

Evaluation of transorbital sonography measures of optic nerve diameter in the context of global and regional brain volume in multiple sclerosis

Transorbital sonography (TOS) could be a swift and convenient method to detect the atrophy of the optic nerve, possibly providing a marker that might reflect other quantitative structural markers of multiple sclerosis (MS). Here we evaluate the utility of TOS as a complementary tool for assessing optic nerve atrophy, and investigate how TOS-derived measures correspond to volumetric brain markers in MS. We recruited 25 healthy controls (HC) and 45 patients with relapsing-remitting MS and performed B-mode ultrasonographic examination of the optic nerve. Patients additionally underwent MRI scans to obtain T1-weighted, FLAIR and STIR images. Optic nerve diameters (OND) were compared between HC, MS patients with and without history of optic neuritis (non-ON) using a mixed-effects ANOVA model. The relationship between within-subject-average OND and global and regional brain volumetric measures was investigated using FSL SIENAX, voxel-based morphometry and FSL FIRST. OND was significantly different between HC-MS (HC = 3.2 ± 0.4 mm, MS = 3 ± 0.4 mm; p < 0.019) and we found significant correlation between average OND and normalised whole brain (β = 0.42, p < 0.005), grey matter (β = 0.33, p < 0.035), white matter (β = 0.38, p < 0.012) and ventricular cerebrospinal fluid volume (β = - 0.36, p < 0.021) in the MS group. History of ON had no impact on the association between OND and volumetric data. In conclusion, OND is a promising surrogate marker in MS, that can be simply and reliably measured using TOS, and its derived measures correspond to brain volumetric measures. It should be further explored in larger and longitudinal studies.

Disorders of vision in multiple sclerosis

Multiple sclerosis (MS) is a neurological inflammatory disorder known to attack the heavily myelinated regions of the nervous system including the optic nerves, cerebellum, brainstem and spinal cord. This review will discuss the clinical manifestations and investigations for MS and other similar neurological inflammatory disorders affecting vision, as well as the effects of MS treatments on vision. Assessment of visual pathways is critical, considering MS can involve multiple components of the visual pathway, including optic nerves, uvea, retina and occipital cortex. Optical coherence tomography is increasingly being recognised as a highly sensitive tool in detecting subclinical optic nerve changes. Magnetic resonance imaging (MRI) is critical in MS diagnosis and in predicting long-term disability. Optic neuritis in MS involves unilateral vision loss, with characteristic pain on eye movement. The visual loss in neuromyelitis optica spectrum disorder tends to be more severe with preferential altitudinal field loss, chiasmal and tract lesions are also more common. Other differential diagnoses include chronic relapsing inflammatory optic neuropathy and giant cell arteritis. Leber's hereditary optic neuropathy affects young males and visual loss tends to be painless and subacute, typically involving both optic nerves. MS lesions in the vestibulocerebellum, brainstem, thalamus and basal ganglia may lead to abnormalities of gaze, saccades, pursuit and nystagmus which can be identified on eye examination. Medial longitudinal fasciculus lesions can cause another frequent presentation of MS, internuclear ophthalmoplegia, with failure of ipsilateral eye adduction and contralateral eye abduction nystagmus. Treatments for MS include high-dose corticosteroids for acute relapses and disease-modifying medications for relapse prevention. These therapies may also have adverse effects on vision, including central serous retinopathy with corticosteroid therapy and macular oedema with fingolimod.

Visual Dysfunction in Multiple Sclerosis and its Animal Model, Experimental Autoimmune Encephalomyelitis: a Review

Visual disabilities in central nervous system autoimmune diseases such as multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), are important symptoms. Past studies have focused on neuro-inflammatory changes and demyelination in the white matter of the brain and spinal cord. In MS, neuro-inflammatory lesions have been diagnosed in the visual pathway; the lesions may perturb visual function. Similarly, neuropathological changes in the retina and optic nerves have been found in animals with chronic EAE. Although the retina and optic nerves are immunologically privileged sites via the blood-retina barrier and blood-brain barrier, respectively, inflammation can occur via other routes, such as the uvea (e.g., iris and choroid) and cerebrospinal fluid in the meninges. This review primarily addresses the direct involvement of the blood-retina barrier and the blood-brain barrier in the development of retinitis and optic neuritis in EAE models. Additional routes, including pro-inflammatory mediator-filled choroidal and subarachnoid spaces, are also discussed with respect to their roles in EAE-induced visual disability and as analogues of MS in humans.

OCT Variability Prevents Their Use as Robust Biomarkers in Multiple Sclerosis

Objective

To evaluate the agreement between the peripapillary retinal nerve fiber layer (pRNFL) and foveal thickness (FT) measurements among three different spectral domain-optical coherence tomography (SD-OCT) instruments in a sample of multiple sclerosis (MS) patients and a healthy age-matched control group.

Methods

An observational cross-sectional study with three groups: healthy subjects and MS patients w/w a previous clinical diagnosis of optic neuritis (ON) was conducted. The pRNFL and FT were measured using three different SD-OCT instruments (OCT PRIMUS 200 and OCT CIRRUS 500 SD-OCT [Carl Zeiss Meditec] and OCT 3D 2000 [Topcon]).

Results

Twenty eyes from 10 healthy subjects matched in age with MS patients without a previous history of eye disease and 62 MS eyes from 31 MS patients (29 eyes without history of ON and 33 eyes with history of ON) were enrolled. Healthy subjects and MS patients without ON did not show differences between the pRNFL and FT thickness (P>0.99) with any of the instruments. However, MS eyes with a previous episode of ON showed thinner pRNFL and FT (P<0.01). PRIMUS and CIRRUS OCT showed better agreement of the pRNLF and FT in both healthy and MS eyes. However, 3D OCT showed less agreement in the pRNFL measurement with CIRRUS in both healthy and MS eyes.

Interpretation

Although OCT is a valuable technology to improve MS patient assessment, differences between devices must be taken into account. It is necessary to create an international group that standardizes the measurement conditions and above all that provides reference bases for normal subjects.

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

Introduction

Joubert syndrome (JS) is a recessive disorder characterized by a congenital malformation of the mid-hindbrain and a large spectrum of clinical features including optic nerve morphologic abnormalities. The function of the visual pathways, including the optic nerve, can be objectively evaluated by visual evoked potential (VEP) recordings. Our work aims to employ VEP to evaluate the neural conduction along the visual pathways in JS patients with or without optic nerve morphologic abnormalities (ONMA).

Methods

In this observational and prospective study, 18 children with genetic diagnosis of JS (mean age 8.78 ± 5.87 years) and 17 healthy age-similar control subjects (control group, 9.05 ± 6.02 years) were enrolled.

Based on presence/absence of ONMA at fundus examination, JS patients were divided into two groups: the JS-A group (eight patients with ONMA) and JS-N group (ten patients without ONMA). Following the ISCEV standards, pattern VEPs were recorded in patients and controls in response to 60’ and 15’ checks to obtain a prevalent activation of large or small axons, respectively.

Results

Compared to controls, both the JS-A and JS-N groups showed significant abnormalities in 60’ and 15’ VEP implicit time and amplitude. Only in the JS-N group were values of 15’ VEP implicit significantly correlated with the corresponding values of visual acuity.

Conclusions

Our results suggest that a visual pathways dysfunction (of both large and small axons) detectable by VEP may occur in JS patients regardless of the presence of ONMA. Since clinical trials are envisaged in the near future to address JS-related ocular problems, our results might provide information about the potential usefulness of VEP recordings to assess the efficacy of treatments targeted to improve the visual pathways’ function.

Functional and structural changes in the visual pathway in multiple sclerosis

INTRODUCTION

Multiple 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).

OBJECTIVES

The 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 METHODS

In 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.

RESULTS

At 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.

CONCLUSIONS

OCT 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.