Early factors associated with axonal loss after optic neuritis

Assessing the visual afferent pathway with the multifocal visual evoked potentials in the radiologically isolated syndrome

The early identification of individuals with radiologically isolated syndrome (RIS) who are at an elevated risk of progressing to multiple sclerosis (MS) is essential for making informed treatment decisions. This study aimed to evaluate the predictive potential of multifocal Visual Evoked Potentials (mfVEP) measures in individuals with RIS with respect to their conversion to MS. A prospective observational cohort study was conducted, involving 21 individuals with RIS recruited from a MS center. Baseline assessments, including mfVEP, magnetic resonance imaging (MRI), and clinical examinations, were performed, and participants were longitudinally followed for up to 24 months. The primary outcome measures were the conversion to MS. Over a clinical follow-up period of 24 months, five individuals (5/21) with RIS progressed to MS. MfVEP amplitude responses (interocular and monocular probability analysis) demonstrated abnormal cluster visual field defects in 47.6% of RIS eyes at baseline, whereas multifocal VEP latency analysis showed significant delays in 38.4%. A reduction in interocular amplitude [OR = 0.036, (95% CI 0.003-0.503); P = 0.014], monocular amplitude [OR = 0.083, (95% CI 0.007-0.982); P = 0.048], and a prolonged interocular latency [OR = 0.095, (95% CI 0.009-0.972); P = 0.047] were associated with a higher relative risk of clinical conversion at the 2-year follow-up. Multifocal VEP may serve as a novel and independent risk factor for predicting the conversion to MS in individuals with Radiologically Isolated Syndrome.

The Study of Remyelinating Therapies in Multiple Sclerosis: Visual Outcomes as a Window Into Repair

INTRODUCTION

Amelioration of disability in multiple sclerosis requires the development of complementary therapies that target neurodegeneration and promote repair. Remyelination is a promising neuroprotective strategy that may protect axons from damage and subsequent neurodegeneration.

METHODS

A review of key literature plus additional targeted search of PubMed and Google Scholar was conducted.

RESULTS

There has been a rapid expansion of clinical trials studying putative remyelinating candidates, but further growth of the field is limited by the lack of consensus on key aspects of trial design. We have not yet defined the ideal study population, duration of therapy, or the appropriate outcome measures to detect remyelination in humans. The varied natural history of multiple sclerosis, coupled with the short time frame of phase II clinical trials, requires that we develop and validate biomarkers of remyelination that can serve as surrogate endpoints in clinical trials.

CONCLUSIONS

We propose that the visual system may be the most well-suited and validated model for the study potential remyelinating agents. In this review, we discuss the pathophysiology of demyelination and summarize the current clinical trial landscape of remyelinating agents. We present some of the challenges in the study of remyelinating agents and discuss current potential biomarkers of remyelination and repair, emphasizing both established and emerging visual outcome measures.

Tissue Hypoxia and Associated Innate Immune Factors in Experimental Autoimmune Optic Neuritis

Visual loss in acute optic neuritis is typically attributed to axonal conduction block due to inflammatory demyelination, but the mechanisms remain unclear. Recent research has highlighted tissue hypoxia as an important cause of neurological deficits and tissue damage in both multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) and, here, we examine whether the optic nerves are hypoxic in experimental optic neuritis induced in Dark Agouti rats. At both the first and second peaks of disease expression, inflamed optic nerves labelled significantly for tissue hypoxia (namely, positive for hypoxia inducible factor-1α (HIF1α) and intravenously administered pimonidazole). Acutely inflamed nerves were also labelled significantly for innate markers of oxidative and nitrative stress and damage, including superoxide, nitric oxide and 3-nitrotyrosine. The density and diameter of capillaries were also increased. We conclude that in acute optic neuritis, the optic nerves are hypoxic and come under oxidative and nitrative stress and damage. Tissue hypoxia can cause mitochondrial failure and thus explains visual loss due to axonal conduction block. Tissue hypoxia can also induce a damaging oxidative and nitrative environment. The findings indicate that treatment to prevent tissue hypoxia in acute optic neuritis may help to restore vision and protect from damaging reactive oxygen and nitrogen species.

Visually Evoked Potential as Prognostic Biomarker for Neuroaxonal Damage in Multiple Sclerosis From a Multicenter Longitudinal Cohort

BACKGROUND AND OBJECTIVES

With the increasing use of visually evoked potentials (VEPs) as quantitative outcome parameters for myelin in clinical trials, an in-depth understanding of longitudinal VEP latency changes and their prognostic potential for subsequent neuronal loss will be required. In this longitudinal multicenter study, we evaluated the association and prognostic potential of VEP latency for retinal neurodegeneration, measured by optical coherence tomography (OCT), in relapsing-remitting MS (RRMS).

METHODS

We included 293 eyes of 147 patients with RRMS (age [years, median ± SD] 36 ± 10, male sex 35%, F/U [years, median {IQR} 2.1 {1.5-3.9}]): 41 eyes had a history of optic neuritis (ON) ≥6 months before baseline (CHRONIC-ON), and 252 eyes had no history of ON (CHRONIC-NON). P100 latency (VEP), macular combined ganglion cell and inner plexiform layer volume (GCIPL), and peripapillary retinal nerve fiber layer thickness (pRNFL) (OCT) were quantified.

RESULTS

P100 latency change over the first year predicted subsequent GCIPL loss (36 months) across the entire chronic cohort (p = 0.001) and in (and driven by) the CHRONIC-NON subset (p = 0.019) but not in the CHRONIC-ON subset (p = 0.680). P100 latency and pRNFL were correlated at baseline (CHRONIC-NON p = 0.004, CHRONIC-ON p < 0.001), but change in P100 latency and pRNFL were not correlated. P100 latency did not differ longitudinally between protocols or centers.

DISCUSSION

VEP in non-ON eyes seems to be a promising marker of demyelination in RRMS and of potential prognostic value for subsequent retinal ganglion cell loss. This study also provides evidence that VEP may be a useful and reliable biomarker for multicenter studies.

Multifocal visual evoked potential evaluation for diagnosis of acute optic neuritis and for prediction of visual outcome and ganglion cell layer thinning following optic neuritis

BACKGROUND

While damage to the optic nerve following optic neuritis (ON) is readily quantifiable, the evaluation of prognosis for visual function and neuroaxonal loss in the acute ON is challenging.

OBJECTIVE

The objective of this study is to investigate the value of multifocal visual evoked potential (mfVEP) in acute ON, diagnostically for acute ON and prognostically for visual outcome and subsequent ganglion cell/inner plexiform layer thickness (GCLIPLt).

METHODS

A prospective cohort study of mfVEP and full-field visual evoked potential (ffVEP) in acute, unilateral ON (onset < 31 days) was conducted. Comparisons with healthy controls (n = 30) and association analysis with follow-up optical coherence tomography (OCT) measurements (of the GCLIPLt) and visual function (Sloan low-contrast visual acuity (LCVA)) were conducted.

RESULTS

Seventy-nine ON patients were included (mean: 17 days from onset). Excluding measurements with conduction block, ffVEP (n = 54) and mfVEP (n = 44) showed sensitivities of 89% and 84% to a specificity of 97%. 65/79 patients were re-examined (mean: 200 days follow-up). mfVEP amplitude and latency inter-eye asymmetry in acute ON correlated with GCLIPLt (r = 0.587 and Spearman's ρ = 0.597, for both, p < 0.001). mfVEP amplitude correlated with LCVA inter-eye asymmetry at follow-up (r = 0.421, p < 0.001), mfVEP latency did not.

CONCLUSION

mfVEP may support the prognostic evaluation of acute ON patients and prove valuable in future neuroprotective and remyelinating trials. In acute ON, the increase in diagnostic value of mfVEP to ffVEP may be limited due to widespread conduction block.

Peripapillary and parafoveal microvascular changes in eyes with optic neuritis and their fellow eyes measured by optical coherence tomography angiography: an Exploratory Study

PURPOSE

This study aimed to evaluate parafoveal and peripapillary microvascular alterations in eyes with optic neuritis (ON) along with their fellow eyes compared to healthy control eyes using optical coherence tomography angiography (OCT-A).

METHODS

We included 31 ON-affected eyes and 31 fellow eyes of 31 patients who had experienced unilateral ON and 33 eyes of 33 healthy controls in this exploratory retrospective cross-sectional study. Optical coherence tomography angiography (OCT-A) was used to generate microvascular structural images and quantify the vessel density of the superficial retinal capillary plexus (SRCP), the deep retinal capillary plexus (DRCP) and radial peripapillary capillary (RPC) segments. We used the Kruskal-Wallis test for the comparison of OCT-A results between the three groups and generalized estimating equation models for the pairwise comparisons.

RESULTS

There were significant differences of SRCP (p = 0.0003) and RPC segment (p < 0.0001) vessel densities between the three groups. Specifically, there was a reduction in parafoveal and peripapillary vessel density in the ON-affected eyes compared to fellow eyes (SRCP, estimates, -1.97, 95% confidence interval [CI], -3.07, -0.87; RPC, -6.95, 95% CI, -8.70, -5.19) and controls (SRCP, -3.15, 95% CI, -4.61, -1.69; RPC, -8.66, 95% CI, -10.55, -6.76). The superior sector of the RPC segments vessel density in the fellow eyes was decreased compared to the controls (-4.93, 95% CI, -8.07, -1.80).

CONCLUSIONS

The results of this study suggest that microvascular changes occur in both the affected eye and unaffected fellow eye after a unilateral ON episode. Future studies are needed to clarify the clinical implications of these findings.

Visual Evoked Potentials as a Biomarker in Multiple Sclerosis and Associated Optic Neuritis

: ABSTRACT:: Multiple sclerosis (MS) is an inflammatory, degenerative disease of the central nervous system (CNS) characterized by progressive neurological decline over time. The need for better "biomarkers" to more precisely capture and track the effects of demyelination, remyelination, and associated neuroaxonal injury is a well-recognized challenge in the field of MS. To this end, visual evoked potentials (VEPs) have a role in assessing the extent of demyelination along the optic nerve, as a functionally eloquent CNS region. Moreover, VEPs testing can be used to predict the extent of recovery after optic neuritis (ON) and capture disabling effects of clinical and subclinical demyelination events in the afferent visual pathway. In this review, the evolving role of VEPs in the diagnosis of patients with ON and MS and the utility of VEPs testing in determining therapeutic benefits of emerging MS treatments is discussed.

Pathophysiological basis of low contrast visual acuity loss in multiple sclerosis

Objective

There is currently an urgent need for reliable clinical biomarkers of remyelination to be used in Phase 2 and Phase 3 clinical trials. Low contrast visual acuity (LCVA) has been suggested as a functional measure of the integrity of the visual pathway. Therefore, the aim of this study was to elucidate the potential contribution of axonal loss and demyelination to LCVA loss in MS patients.

Method

In this study, 50 consecutive relapsing remitting MS patients with a previous history of unilateral optic neuritis were enrolled. Using the linear regression model, we assessed the relative contribution of multifocal Visual Evoked Potentials (mfVEP) latency and Retinal Nerve Fiber Layer (RNFL) thickness to LCVA deficit.

Results

Intereye asymmetry of mfVEP latency and RNFL thickness correlated significantly with intereye asymmetry of LCVA (P < 0.001). A linear regression model demonstrated increased predictive power of LCVA when mfVEP latency and RNFL thinning were combined (reaching R ² = 0.67) and confirmed a higher predictive value of RNFL thinning compared to mfVEP latency delay for both contrast levels. However, elimination of subjects with severe axonal loss dramatically increased the relative contribution of mfVEP latency, with contribution of RNFL thickness losing significance for both 1.25% and 2.5% LCVA.

Interpretation

While retinal ganglion cell axonal loss is a superior predictor of LCVA, the degree of demyelination contributes significantly to worsening of LCVA, particularly when patients with severe axonal loss are excluded. These results support the feasibility of using LCVA as a functional biomarker in remyelination therapy trials, providing appropriate patient's selection criteria are implemented.

Changes in oxygen saturation and the retinal nerve fibre layer in patients with optic neuritis - a pilot study

PURPOSE

Assessment of retinal oxygen saturation, thickness of a retinal nerve fibre layer (RNFL) and functional changes in the optic nerve during optic neuritis (ON) in patients with multiple sclerosis (MS).

METHODS

Thirty-two patients with ON due to MS within 3 months of onset of symptoms were enrolled [22 females, 10 males, age 34 ± 9 years, median 32.5 years, 22 patients with the clinically isolated syndrome (CIS), 10 patients with relapsing-remitting from of MS (RRMS)]. All patients were examined using optical coherence tomography (OCT model 4000, Carl Zeiss Meditec, Dublin, CA, USA), automatic optical oximetry (Oxymap ehf, Reykjavik, Iceland) and using visual evoked potentials (VEP) (Metronic Keypoint^® , Minneapolis, MN, USA).

RESULTS

Arterio-venous difference (AVD) was increased in patients ON affected eye compared to patients' unaffected eye (PUE) [34.2 ± 4.7 versus 31.3 ± 4.6, p = 0.044 (mean ± standard deviation)]. No statistically significant difference was found in vessel oxygen saturation as well as in RNFL thickness in ON affected eyes when compared to unaffected MS eyes and healthy individuals. Significantly lower optic nerve conduction velocity was found in the affected eye when compared to unaffected MS eye and healthy (p < 0.0001 for both comparisons). No correlation between oxygen saturation values and VEP was observed in patients with MS.

CONCLUSION

The AVD in oxygen saturation is altered in patients with acute ON. In the early stage of ON, AVD could reflect inflammatory and metabolic changes in the affected eye. Therefore, oximetry could be used as another diagnostic method in MS patients in suspicion of ON. This result would be promising for future investigation in this field.

Multiple sclerosis

Multiple sclerosis continues to be a challenging and disabling condition but there is now greater understanding of the underlying genetic and environmental factors that drive the condition, including low vitamin D levels, cigarette smoking, and obesity. Early and accurate diagnosis is crucial and is supported by diagnostic criteria, incorporating imaging and spinal fluid abnormalities for those presenting with a clinically isolated syndrome. Importantly, there is an extensive therapeutic armamentarium, both oral and by infusion, for those with the relapsing remitting form of the disease. Careful consideration is required when choosing the correct treatment, balancing the side-effect profile with efficacy and escalating as clinically appropriate. This move towards more personalised medicine is supported by a clinical guideline published in 2018. Finally, a comprehensive management programme is strongly recommended for all patients with multiple sclerosis, enhancing health-related quality of life through advocating wellness, addressing aggravating factors, and managing comorbidities. The greatest remaining challenge for multiple sclerosis is the development of treatments incorporating neuroprotection and remyelination to treat and ultimately prevent the disabling, progressive forms of the condition.

Frequent retinal ganglion cell damage after acute optic neuritis

BACKGROUND

To identify the extent of ganglion cell damage after first-time optic neuritis (ON) using the inter-ocular difference between affected and fellow eyes, and whether this approach is able to detect more patients suffering from ganglion cell damage than using absolute values.

METHODS

Thirty-four patients with first-time unilateral ON were followed for a median 413 days. Patients underwent optical coherence tomography testing to determine ganglion cell plus inner plexiform layer thickness (GCIP). Ganglion cell loss was quantified as GCIP difference between ON-affected and fellow eyes (inter-GCIP) and was compared against measurements from 93 healthy controls (HC). Visual function was assessed with high contrast visual acuity; and standard automated perimetry-derived measures of mean deviation and foveal threshold.

RESULTS

At clinical presentation after median 19 days from symptom onset, 47.1% of patients showed early GCIP thinning in the ON-affected eye based on inter-GCIP. At the last visit acute ON was associated with 16.1 ± 10.0 µm GCIP thinning compared to fellow eyes (p = 3.669e-06). Based on inter-GCIP, 84.9% of ON patients sustained GCIP thinning in their affected eye at the last visit, whereas using absolute values only 71.0% of patients suffered from GCIP thinning (p = 0.002076). Only 32.3% of these patients had abnormal visual function. The best predictor of GCIP thinning as a measure of ON severity at the last visit was worse visual field mean deviation at clinical presentation.

CONCLUSION

Inter-ocular GCIP identifies significantly more eyes suffering damage from ON than absolute GCIP, visual fields or visual acuity loss. Effective interventional options are needed to prevent ganglion cell loss.

Vascular hypoperfusion in acute optic neuritis is a potentially new neurovascular model for demyelinating diseases

PURPOSE

Optic neuritis is highly correlated with multiple sclerosis and is a major cause of acute visual loss and long-term neuronal degeneration. Primary cerebral hypoperfusion has been reported in brain demyelinating diseases. This study investigated whether peripapillary perfusion is changed in patients with acute optic neuritis (AON).

METHODS

This three-year cohort study was conducted from September 1 2012, to August 31, 2015. Two hundred and forty-one patients with non-glaucomatous acute optic neuropathy were screened, and 42 non-highly myopic patients who had suffered their first episode of unilaterally idiopathic AON were studied. All cases received spectral-domain optical coherence tomography (OCT) examination, general survey, and standard corticosteroid therapy. OCT images were analyzed using a customized MATLAB program for measuring peripapillary choroidal thickness (PCT). Multivariate regression models were constructed to identify factors that are significantly related to peripapillary perfusion.

RESULTS

Decreased PCT was found in eyes experiencing AON combined with disc swelling (the ratio of lesion eye PCT/fellow eye PCT was 0.87 ± 0.08; range, from 0.75 to 1.00). In comparison to the healthy fellow eyes, approximately every 26% increase in the thickness of the retinal nerve fiber layer due to axonal swelling was associated with a 10% decreased thickness of PCT. Thinner PCT is also correlated with poorer trough vision, which may lead to poorer final vision. These findings were obvious in patients with optic papillitis but not in patients with retrobulbar neuritis.

CONCLUSIONS

Peripapillary vascular hypoperfusion was found in patients experiencing AON combined with disc swelling. These findings are unlike those for other ocular inflammatory diseases but are consistent with cerebral hypoperfusion, which is found in brain demyelinating diseases; thus, these findings may represent a new neurovascular model in this field.

Diffusion tensor imaging for multilevel assessment of the visual pathway: possibilities for personalized outcome prediction in autoimmune disorders of the central nervous system

The afferent visual pathway represents the most frequently affected white matter pathway in multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD). Diffusion tensor imaging (DTI) can reveal microstructural or non-overt brain tissue damage and quantify pathological processes. DTI facilitates the reconstruction of major white matter fiber tracts allowing for the assessment of structure-function and damage-dysfunction relationships. In this review, we outline DTI studies investigating the afferent visual pathway in idiopathic optic neuritis (ON), NMOSD, and MS. Since MS damage patterns are believed to depend on multiple factors, i.e., ON (anterior visual pathway damage), inflammatory lesions (posterior visual pathway damage), and global diffuse inflammatory and neurodegenerative processes, comprehensive knowledge on different contributing factors using DTI in vivo may advance our understanding of MS disease pathology. Combination of DTI measures and visual outcome parameters yields the potential to improve routine clinical diagnostic procedures and may further the accuracy of individual prognosis with regard to visual function and personalized disease outcome. However, due to the inherent limitations of DTI acquisition and post-processing techniques and the so far heterogeneous and equivocal data of previous studies, evaluation of the true potential of DTI as a possible biomarker for afferent visual pathway dysfunction is still substantially limited. Further research efforts with larger longitudinal studies and standardized DTI acquisition and post-processing validation criteria are needed to overcome current DTI limitations. DTI evaluation at different levels of the visual pathway has the potential to provide markers for individual damage evaluation in the future. As an imaging biomarker, DTI may support individual outcome prediction during personalized treatment algorithms in MS and other neuroinflammatory diseases, hereby leveraging the concept of predictive, preventive, and personalized medicine in the field of clinical neuroimmunology.

Validity of low-contrast letter acuity as a visual performance outcome measure for multiple sclerosis

Low-contrast letter acuity (LCLA) has emerged as the leading outcome measure to assess visual disability in multiple sclerosis (MS) research. As visual dysfunction is one of the most common manifestations of MS, sensitive visual outcome measures are important in examining the effect of treatment. Low-contrast acuity captures visual loss not seen in high-contrast visual acuity (HCVA) measurements. These issues are addressed by the MS Outcome Assessments Consortium (MSOAC), including representatives from advocacy organizations, Food and Drug Administration (FDA), European Medicines Agency (EMA), National Institute of Neurological Disorders and Stroke (NINDS), academic institutions, and industry partners along with persons living with MS. MSOAC goals are acceptance and qualification by regulators of performance outcomes that are highly reliable and valid, practical, cost-effective, and meaningful to persons with MS. A critical step is elucidation of clinically relevant benchmarks, well-defined degrees of disability, and gradients of change that are clinically meaningful. This review shows that MS and disease-free controls have similar median HCVA, while MS patients have significantly lower LCLA. Deficits in LCLA and vision-specific quality of life are found many years after an episode of acute optic neuritis, even when HCVA has recovered. Studies reveal correlations between LCLA and the Expanded Disability Status Score (EDSS), Multiple Sclerosis Functional Composite (MSFC), retinal nerve fiber layer (RNFL) and ganglion cell layer plus inner plexiform layer (GCL + IPL) thickness on optical coherence tomography (OCT), brain magnetic resonance imaging (MRI), visual evoked potential (VEP), electroretinogram (ERG), pupillary function, and King-Devick testing. This review also concludes that a 7-point change in LCLA is clinically meaningful. The overall goal of this review is to describe and characterize the LCLA metric for research and clinical use among persons with MS.

Quantitative visual tests after poorly recovered optic neuritis due to multiple sclerosis

BACKGROUND

Visual dysfunction in MS can be quantified using a variety of tests. Many vision tests have not been formally evaluated among MS patients with existing visual dysfunction.

OBJECTIVE

Evaluate several versions of visual acuity and contrast sensitivity tests, measures of central and peripheral vision, retina structure, electrophysiologic function, and quality of life among MS patients with moderate/severe visual dysfunction.

METHODS

Cross-sectional study of 46 patients with stable, incompletely recovered optic neuritis. Testing included Snellen eye charts, several Sloan low contrast charts, Pelli Robson (PR) contrast sensitivity charts, optical coherence tomography, visual fields, Farnsworth Munsell 100-hue test, visual evoked potentials (VEP), and visual function quality of life (VFQ-25) testing.

RESULTS

98% of eyes could read two lines of the PR chart, while only 43% read the 2.5% contrast chart. Low contrast tests correlated strongly with each other and with retinal nerve fiber layer (RNFL) thickness, visual fields, and color vision but not with VEPs. For patients with RNFL <75µm, VFQ-25 scores dropped by approximately 2 points for every 1µm decrease in RNFL.

CONCLUSION

Among MS patients with visual impairment due to optic neuritis, PR contrast sensitivity could be utilized as a single chart. Visual quality of life was associated with RNFL thinning below 75µm.

Retinal degeneration in primary-progressive multiple sclerosis: A role for cortical lesions?

Background:

Retinal atrophy in multiple sclerosis (MS) is secondary to optic nerve focal inflammation and to injury of the posterior visual pathway.

Objectives:

To investigate the contribution of cortical lesions (CLs) to retinal pathology in primary-progressive multiple sclerosis (PPMS).

Methods:

We performed a cross-sectional evaluation of 25 patients and 20 controls, relating magnetic resonance imaging (MRI) metrics of visual pathway integrity with parameters derived from spectral-domain optical coherence tomography (peripapillary retinal nerve fiber layer (RNFL) thickness, ganglion cell + inner plexiform layer (GCIPL) thickness, and macular volume (MV)).

Results:

Mean RNFL, GCIPL thickness, and MV were significantly reduced in patients compared to controls. MV and GCIPL thickness were significantly correlated with visual acuity. RNFL thinning was associated with thalamus and visual cortex volume (respectively, p = 0.01 and p < 0.05). In addition to thalamic volume, GCIPL thinning was associated with CLs and intracortical lesion number and volume, leucocortical lesion volume (all p ⩽ 0.05) while MV decrease was associated with CLs volume ( p = 0.05) and intracortical lesion number and volume ( p < 0.05).

Conclusion:

Our results suggest that RNFL thinning and GCIPL thinning/MV decrease may be explained by alternative mechanisms including retrograde trans-synaptic degeneration and/or a common pathophysiologic process affecting both the brain with CLs and the retina with neuronal loss.

Amiloride Clinical Trial In Optic Neuritis (ACTION) protocol: a randomised, double blind, placebo controlled trial

INTRODUCTION

Neurodegeneration is a widely accepted contributor to the development of long-term disability in multiple sclerosis (MS). While current therapies in MS predominantly target inflammation and reduce relapse rate they have been less effective at preventing long-term disability. The identification and evaluation of effective neuroprotective therapies within a trial paradigm are key unmet needs. Emerging evidence supports amiloride, a licenced diuretic, as a neuroprotective agent in MS through acid sensing ion channel blockade. Optic neuritis (ON) is a common manifestation of MS with correlates of inflammation and neurodegeneration measurable within the visual pathways. Amiloride Clinical Trial In Optic Neuritis (ACTION) will utilise a multimodal approach to assess the neuroprotective efficacy of amiloride in acute ON.

METHODS AND ANALYSIS

46 patients will be recruited within 28 days from onset of ON visual symptoms and randomised on a 1:1 basis to placebo or amiloride 10 mg daily. Double-blinded treatment groups will be balanced for age, sex and visual loss severity by a random-deterministic minimisation algorithm. The primary objective is to demonstrate that amiloride is neuroprotective in ON as assessed by scanning laser polarimetry of the peripapillary retinal nerve fibre layer (RNFL) thickness at 6 months in the affected eye compared to the unaffected eye at baseline. RNFL in combination with further retinal measures will also be assessed by optical coherence tomography. Secondary outcome measures on brain MRI will include cortical volume, diffusion-weighted imaging, resting state functional MRI, MR spectroscopy and magnetisation transfer ratio. In addition, high and low contrast visual acuity, visual fields, colour vision and electrophysiology will be assessed alongside quality of life measures.

ETHICS AND DISSEMINATION

Ethical approval was given by the south central Oxford B research ethics committee (REC reference: 13/SC/0022). The findings from ACTION will be disseminated through peer-reviewed publications and at scientific conferences.

TRIAL REGISTRATION NUMBER

EudraCT2012-004980-39, ClinicalTrials.gov Identifier: NCT01802489.

Cerebrospinal fluid neurofilament light chain levels predict visual outcome after optic neuritis

Background:

Optic neuritis is a good model for multiple sclerosis relapse, but currently no tests can accurately predict visual outcome.

Objective:

The purpose of this study was to examine whether cerebrospinal fluid (CSF) biomarkers of tissue damage and remodelling (neurofilament light chain (NF-L), myelin basic protein, osteopontin and chitinase-3-like-1) predict visual outcome after optic neuritis.

Methods:

We included 47 patients with optic neuritis as a first demyelinating episode. Patients underwent visual tests, optical coherence tomography (OCT), magnetic resonance imaging (MRI) and lumbar puncture. Biomarkers were measured in CSF by enzyme-linked immunosorbent assay (ELISA). Patients were followed up six months after onset and this included visual tests and OCT. Outcome measures were inter-ocular differences in low contrast visual acuity (LCVA), retinal nerve fibre layer (RNFL) and ganglion cell layer+inner plexiform layer (GC-IPL) thicknesses.

Results:

CSF NF-L levels at onset predicted inter-ocular differences in follow-up LCVA (β=13.8, p=0.0008), RNFL (β=5.6, p=0.0004) and GC-IPL (β=4.0, p=0.0008). The acute-phase GC-IPL thickness also predicted follow-up LCVA (β=12.9, p=0.0021 for NF-L, β=−1.1, p=0.0150 for GC-IPL). Complete/incomplete remission was determined based on LCVA from 30 healthy controls. NF-L had a positive predictive value of 91% and an area under the curve (AUC) of 0.79 for incomplete remission.

Conclusion:

CSF NF-L is a promising biomarker of visual outcome after optic neuritis. This could aid neuroprotective/regenerative medical advancements.

Acute optic neuritis: Unmet clinical needs and model for new therapies

Idiopathic demyelinating optic neuritis (ON) most commonly presents as acute unilateral vision loss and eye pain and is frequently associated with multiple sclerosis. Although emphasis is often placed on the good recovery of high-contrast visual acuity, persistent deficits are frequently observed in other aspects of vision, including contrast sensitivity, visual field testing, color vision, motion perception, and vision-related quality of life. Persistent and profound structural and functional changes are often revealed by imaging and electrophysiologic techniques, including optical coherence tomography, visual-evoked potentials, and nonconventional MRI. These abnormalities can impair patients' abilities to perform daily activities (e.g., driving, working) so they have important implications for patients' quality of life. In this article, we review the sequelae from ON, including clinical, structural, and functional changes and their interrelationships. The unmet needs in each of these areas are considered and the progress made toward meeting those needs is examined. Finally, we provide an overview of past and present investigational approaches for disease modification in ON.

Re-evaluating the treatment of acute optic neuritis

Clinical case reports and prospective trials have demonstrated a reproducible benefit of hypothalamic-pituitary-adrenal (HPA) axis modulation on the rate of recovery from acute inflammatory central nervous system (CNS) demyelination. As a result, corticosteroid preparations and adrenocorticotrophic hormones are the current mainstays of therapy for the treatment of acute optic neuritis (AON) and acute demyelination in multiple sclerosis.Despite facilitating the pace of recovery, HPA axis modulation and corticosteroids have failed to demonstrate long-term benefit on functional recovery. After AON, patients frequently report visual problems, motion perception difficulties and abnormal depth perception despite 'normal' (20/20) vision. In light of this disparity, the efficacy of these and other therapies for acute demyelination require re-evaluation using modern, high-precision paraclinical tools capable of monitoring tissue injury.In no arena is this more amenable than AON, where a new array of tools in retinal imaging and electrophysiology has advanced our ability to measure the anatomic and functional consequences of optic nerve injury. As a result, AON provides a unique clinical model for evaluating the treatment response of the derivative elements of acute inflammatory CNS injury: demyelination, axonal injury and neuronal degeneration.In this article, we examine current thinking on the mechanisms of immune injury in AON, discuss novel technologies for the assessment of optic nerve structure and function, and assess current and future treatment modalities. The primary aim is to develop a framework for rigorously evaluating interventions in AON and to assess their ability to preserve tissue architecture, re-establish normal physiology and restore optimal neurological function.

Clinical trials to clinical use: using vision as a model for multiple sclerosis and beyond

Optical coherence tomography (OCT) has made possible the structure-function correlations that uniquely characterize the afferent visual pathway as a model for understanding multiple sclerosis (MS) and for developing new treatments. During the past decade, OCT measures of retinal nerve fiber layer (RNFL) and ganglion cell/inner plexiform layer (GCL + IPL) thickness have evolved from being a means to validate visual function tests, such as low-contrast letter acuity, to provide a window on the axonal and neuronal loss that are now widely recognized as contributors to permanent visual dysfunction in MS. Although acute optic neuritis (ON) leads to thinning of the RNFL by 20%-40% within 3 months after a single episode, thinning of the RNFL and GCL + IPL occur over time in MS eyes even in the absence of an acute ON history. As such, OCT and its functional and patient-reported correlates of low-contrast acuity and vision-specific quality of life (QOL) have now been incorporated into MS clinical trials. Results of an ongoing, phase 2 trial of a remyelinating agent that uses acute ON as a model for assessing therapeutic efficacy will define even further the important role for OCT in documenting structural changes as we move forward from clinical trials to clinical use.

Longitudinal Changes in Retinal Nerve Fibre Layer Thickness after an Isolated Unilateral Retrobulbar Optic Neuritis: 1-Year Results

The objective of this study was to investigate the longitudinal changes in retinal nerve fibre layer (RNFL) thickness 1 year after an episode of unilateral acute optic neuritis. This prospective cohort study recruited consecutive patients with a first episode of isolated, unilateral acute optic neuritis from October 2010 to June 2013. RNFL thickness of the attack and normal fellow eyes was measured by optical coherence tomography on presentation and 3, 6, and 12 months post attack in both the treatment and non-treatment groups. The treatment group consisted of subjects that opted for systemic steroids to hasten recovery time. In 20 subjects, 11 received systemic steroids and 9 were treated conservatively. The baseline RNFL thickness was similar in the attack and fellow eyes (p ≥ 0.4). Progressive RNFL thinning was seen in the attack eye over the 12-month period, with significant differences for baseline versus 3 months; baseline versus 12 months; and 3 versus 12 months (all p < 0.0001). At 12 months, the attack eye had a thinner average RNFL than the fellow eye (100.9 ± 6.1 versus 107.3 ± 5.5 µm; p = 0.002). The 12-month RNFL was similar between the treatment and non-treatment groups (p ≥ 0.6). A single episode of optic neuritis triggered an accelerated, progressive RNFL thinning up to 6 months post attack. Initial treatment with systemic steroids did not seem to alter the degree of RNFL loss at 12 months.

Vision and vision-related outcome measures in multiple sclerosis

Visual impairment is a key manifestation of multiple sclerosis. Acute optic neuritis is a common, often presenting manifestation, but visual deficits and structural loss of retinal axonal and neuronal integrity can occur even without a history of optic neuritis. Interest in vision in multiple sclerosis is growing, partially in response to the development of sensitive visual function tests, structural markers such as optical coherence tomography and magnetic resonance imaging, and quality of life measures that give clinical meaning to the structure-function correlations that are unique to the afferent visual pathway. Abnormal eye movements also are common in multiple sclerosis, but quantitative assessment methods that can be applied in practice and clinical trials are not readily available. We summarize here a comprehensive literature search and the discussion at a recent international meeting of investigators involved in the development and study of visual outcomes in multiple sclerosis, which had, as its overriding goals, to review the state of the field and identify areas for future research. We review data and principles to help us understand the importance of vision as a model for outcomes assessment in clinical practice and therapeutic trials in multiple sclerosis.

Imaging outcomes for trials of remyelination in multiple sclerosis

Trials of potential neuroreparative agents are becoming more important in the spectrum of multiple sclerosis research. Appropriate imaging outcomes are required that are feasible from a time and practicality point of view, as well as being sensitive and specific to myelin, while also being reproducible and clinically meaningful. Conventional MRI sequences have limited specificity for myelination. We evaluate the imaging modalities which are potentially more specific to myelin content in vivo, such as magnetisation transfer ratio (MTR), restricted proton fraction f (from quantitative magnetisation transfer measurements), myelin water fraction and diffusion tensor imaging (DTI) metrics, in addition to positron emission tomography (PET) imaging. Although most imaging applications to date have focused on the brain, we also consider measures with the potential to detect remyelination in the spinal cord and in the optic nerve. At present, MTR and DTI measures probably offer the most realistic and feasible outcome measures for such trials, especially in the brain. However, no one measure currently demonstrates sufficiently high sensitivity or specificity to myelin, or correlation with clinical features, and it should be useful to employ more than one outcome to maximise understanding and interpretation of findings with these sequences. PET may be less feasible for current and near-future trials, but is a promising technique because of its specificity. In the optic nerve, visual evoked potentials can indicate demyelination and should be correlated with an imaging outcome (such as optic nerve MTR), as well as clinical measures.

Interleukin-8 is associated with acute and persistent dysfunction after optic neuritis

Background:

Acute optic neuritis is often in association with multiple sclerosis (MS). Proinflammatory cytokines trigger neuronal damage in neuroinflammatory disorders but their role in optic neuritis is poorly investigated.

Objective:

The objective of this work is to investigate the associations of intrathecal contents of proinflammatory cytokines with transient and persistent dysfunctions after optic neuritis.

Methods:

In 50 MS patients followed for up to six months, cerebrospinal fluid (CSF) levels of IL-1β, TNF and IL-8 were determined, along with clinical, neurophysiological and morphological measures of optic neuritis severity.

Results:

Visual impairment, measured by high- and low-contrast visual acuity, and delayed visual-evoked potential (VEP) latencies were significantly correlated to IL-8 levels during optic neuritis. IL-8 at the time of optic neuritis was also associated with persistent demyelination and final axonal loss, inferred by VEP and optical coherence tomography measures, respectively. Contents of IL-8 were correlated to functional visual outcomes, being higher among patients with incomplete recovery. Multivariate analysis confirmed that IL-8 significantly predicted final visual acuity, at equal values of demographics and baseline visual scores.

Conclusion:

Our study points to IL-8 as the main inflammatory cytokine associated with demyelination and secondary neurodegeneration in the optic nerve after optic neuritis.

The value of clinical electrophysiology in the assessment of the eye and visual system in the era of advanced imaging

Electrophysiological techniques allow clinical investigations to include a 'dissection' of the visual system. Using suitable electrophysiological techniques, the 'dissection' allows function to be ascribed to the different photoreceptors (rod and cone photoreceptors), retinal layers, retinal location or the visual pathway up to the visual cortex. Combined with advances in genetics, retinal biochemistry, visual fields and ocular imaging, it is now possible to obtain a better understanding of diseases affecting the retina and visual pathways. This paper reviews core electrophysiological principles that can complement other examination techniques, including advanced ocular imaging, and help the interpretation of other clinical data and thus, refine and guide clinical diagnosis.

Understanding the pharmacology of stroke and multiple sclerosis through imaging

Stroke and multiple sclerosis (MS) illustrate how clinical imaging can facilitate early phase drug development and most effective medicine use in the clinic. Imaging has enhanced understanding of the dynamics of evolution of disease pathophysiology, better defining treatment targets. Imaging measures can enable stratification of patients for clinical trials and for most cost-effective use in the clinic. In MS, imaging has allowed smaller Phase II clinical trials and contributed to medicine differentiation. It also has led to consideration of suppression of inflammation and neurodegeneration as meaningfully distinct pharmacodynamic concepts. Similar imaging measures can be used in preclinical and clinical studies. Testing translational pharmacological hypotheses using clinical imaging more explicitly could improve the success of the next generation of stroke therapeutics.

Optic neuritis

Acute optic neuritis is the most common optic neuropathy affecting young adults. Exciting developments have occurred over the past decade in understanding of optic neuritis pathophysiology, and these developments have been translated into treatment trials. In its typical form, optic neuritis presents as an inflammatory demyelinating disorder of the optic nerve, which can be associated with multiple sclerosis. Atypical forms of optic neuritis can occur, either in association with other inflammatory disorders or in isolation. Differential diagnosis includes various optic nerve and retinal disorders. Diagnostic investigations include MRI, visual evoked potentials, and CSF examination. Optical coherence tomography can show retinal axonal loss, which correlates with measures of persistent visual dysfunction. Treatment of typical forms with high-dose corticosteroids shortens the period of acute visual dysfunction but does not affect the final visual outcome. Atypical forms can necessitate prolonged immunosuppressive regimens. Optical coherence tomography and visual evoked potential measures are suitable for detection of neuroaxonal loss and myelin repair after optic neuritis. Clinical trials are underway to identify potential neuroprotective or remyelinating treatments for acutely symptomatic inflammatory demyelinating CNS lesions.

Prospective study on retinal nerve fibre layer thickness changes in isolated unilateral retrobulbar optic neuritis

Purpose. To investigate the retinal nerve fibre layer (RNFL) thickness after unilateral acute optic neuritis using optical coherence tomography (OCT). Patients and Methods. This prospective cohort study recruited consecutive patients with a first episode of isolated, unilateral acute optic neuritis. RNFL thickness and visual acuity (VA) of the attack and normal fellow eye were measured at presentation and 3 months in both the treatment and nontreatment groups. Results. 11 subjects received systemic steroids and 9 were treated conservatively. The baseline RNFL thickness was similar in the attack and fellow eye (P ≥ 0.4). At 3 months, the attack eye had a thinner temporal (P = 0.02) and average (P = 0.05) RNFL compared to the fellow eye. At 3 months, the attack eye had significant RNFL thinning in the 4 quadrants and average thickness (P ≤ 0.0002) compared to baseline. The RNFL thickness between the treatment and nontreatment groups was similar at baseline and 3 months (P ≥ 0.1). Treatment offered better VA at 3 months (0.1 ± 0.2 versus 0.3 ± 0.2 LogMAR, P = 0.04). Conclusion. Generalized RNFL thinning occurred at 3 months after a first episode of acute optic neuritis most significantly in the temporal quadrant and average thickness. Visual improvement with treatment was independent of RNFL thickness.

MRI texture heterogeneity in the optic nerve predicts visual recovery after acute optic neuritis

PURPOSE

To test the feasibility of using multi-scale MRI texture analysis to assess optic nerve pathology and to investigate how visual recovery relates to the severity of acute tissue damage in the optic nerve in patients after optic neuritis (ON).

MATERIALS AND METHODS

We recruited 25 patients with acute ON. Retinal nerve fiber layer (RNFL) thickness; MRI lesion length and enhancement; optic nerve area ratio; and multi-scale MRI texture analysis, a measure of structural integrity, were used to assess tissue damage at baseline, and at 6 and 12 months. The recovery in vision was defined as the functional outcome. Eight healthy subjects were imaged for control.

RESULTS

We identified 25 lesions in the affected eyes (9 enhanced) and 5 in the clinically non-affected eyes (none enhanced). At baseline, we found that RNFL values were 20% thicker and lesion texture 14% more heterogeneous in the affected eyes than in the non-affected eyes, and lesion texture ratio of affected to non-affected eyes was greater in patients than in controls. In the affected eyes, visual acuity recovered significantly over 6 (18/23 patients) and 12 months (18/21 patients) when RNFL thickness and optic nerve area ratio decreased over time. Texture heterogeneity in the standard MRI of acute optic nerve lesions was the only measure that predicted functional recovery after ON.

CONCLUSIONS

Tissue heterogeneity may be a potential measure of functional outcome in ON patients and advanced analysis of the texture in standard MRI could provide insights into mechanisms of injury and recovery in patients with similar disorders.

[Diagnosis and monitoring of multiple sclerosis: the value of optical coherence tomography]

Besides the relapse rate and neurological examination, magnetic resonance imaging (MRI) plays a key role in multiple sclerosis (MS) monitoring. However, MRI is costly and even in Germany not always readily available. Additionally, routine MRI scans are not sensitive enough regarding differentiation between demyelination and neurodegeneration and show a discrepancy between lesion load and the degree of disability. In contrast, optical coherence tomography (OCT) is a validated non-invasive method for the quantification of neurodegenerative processes in the retina, as they appear in MS and other neurological diseases. The OCT is inexpensive, easy to handle and highly reproducible. Additionally, it is well tolerated and thus represents a promising tool for monitoring of neurodegenerative disorders. This article describes in detail the OCT technique and its usefulness for both diagnosis and monitoring of MS.

The afferent visual pathway: designing a structural-functional paradigm of multiple sclerosis

Multiple sclerosis (MS) is a disease of the central nervous system (CNS) believed to arise from a dysfunctional immune-mediated response in a genetically susceptible host. The actual cause of MS is not known, and there is ongoing debate about whether this CNS disorder is predominantly an inflammatory versus a degenerative condition. The afferent visual pathway (AVP) is frequently involved in MS, such that one in every five individuals affected presents with acute optic neuritis (ON). As a functionally eloquent system, the AVP is amenable to interrogation with highly reliable and reproducible tests that can be used to define a structural-functional paradigm of CNS injury. The AVP has numerous unique advantages as a clinical model of MS. In this review, the parameters and merits of the AVP model are highlighted. Moreover, the roles the AVP model may play in elucidating mechanisms of brain injury and repair in MS are described.

Assessment of structural and functıonal vısual outcomes ın relapsıng remıttıng multıple sclerosıs wıth vısual evoked potentıals and optıcal coherence tomography

The purpose of this study is to consider the clinical utility of optical coherence tomography (OCT) and find a correlation with VEP. Effects of different disease modifying treatments (DMT) were further evaluated by measuring OCT parameters and whether a correlation exists between the RNFL thickness, disease duration and expanded disability status scale (EDSS) were also assessed. 13 patients were on interferon beta-1a (IFN), 14 patients were receiving glatiramer acetate (GA), 19 patients were not being treated with any DMT and 21 healthy controls were included the study. During OCT examination, retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) thickness was found to be lower in all MS groups but macular volume (MV) was lower only in GA group than controls. Although, P100 latencies were longer than controls in all MS groups, there was no statistically significant difference between IFN and w/o DMT groups. Patients with ON history, P100 latencies were found significantly longer than those without ON. VEP amplitudes were found lower with ON history patients than those without ON, however this was not statistically significant. EDSS strongly correlated with P100 latency, RNLF, GCC but no correlation was observed with VEP amplitude and MV. Our results show that RNFL, GCC and MV were all decreased in MS patients with or without DMT comparing to controls and it is more prominent in eyes with ON. Further follow-up studies are warranted to understand the pathophysiology of CNS axonal degeneration and involvement of optic nerves.

Three-dimensional geometries representing the retinal nerve fiber layer in multiple sclerosis, optic neuritis, and healthy eyes

BACKGROUND

To represent and interpret the three-dimensional (3D) geometry and the distribution of the axonal damage to the retinal nerve fiber layer (RNFL) in patients with multiple sclerosis (MS) compared with healthy subjects. To analyze alterations in RNFL morphology in eyes of MS patients with or without previous episodes of optic neuritis (ON).

METHODS

MS patients (n = 122) and age-matched healthy subjects (n = 108) were enrolled. The Spectralis optical coherence tomography system was used to determine the circumpapillary RNFL thickness. The 768 RNFL thickness measurements were used to evaluate thickness measurements in patients with or without antecedent ON and to design a 3D reconstruction of the RNFL thickness representing the mechanobiologic tissue response to neurodegeneration caused by MS and ON episodes.

RESULTS

RNFL thickness was decreased in MS patients, and was higher in the MS group with previous ON. Statistical analysis and 3D RNFL reconstruction revealed greater damage to the ganglionar cells in the superonasal RNFL area (101.77 µm in MS vs. 125.47 µm in healthy subjects) and in the inferotemporal RNFL (119.05 µm in MS eyes and 149.26 µm in healthy eyes).

CONCLUSIONS

The 3D representation of RNFL thickness based on measurements allows physicians to better observe damage in the temporal areas, especially in patients with previous ON.

Retinal nerve fibre layer thinning in patients with clinically isolated optic neuritis and early treatment with interferon-beta

BACKGROUND

Optic neuritis is associated with neurodegeneration leading to chronic impairment of visual functions.

OBJECTIVE

This study investigated whether early treatment with interferon beta (IFN-β) slows retinal nerve fibre layer (RNFL) thinning in clinically isolated optic neuritis.

METHODS

Twenty patients with optic neuritis and visual acuity decreased to ≤0.5 (decimal system) were included into this prospective, open-label, parallel group 4-month observation. After methylprednisolone pulse therapy, 10 patients received IFN-β from week 2 onwards. This group was compared to 10 patients free of any disease modifying treatment (DMT). The parameter of interest was change in RNFL thickness assessed at baseline and at weeks 4, 8, and 16. Changes in visual acuity, visual field, and visual evoked potentials (VEPs) served as additional outcome parameters.

RESULTS

RNFL thinning did not differ between the groups with a mean reduction of 9.80±2.80 µm in IFN-β-treated patients (±SD) vs. 12.44±5.79 µm in patients who did not receive DMT (baseline non-affected eye minus affected eye at week 16; p = 0.67, t-test, 95% confidence interval: -15.77 to 10.48). Parameters of visual function did not show any differences between the groups either.

CONCLUSIONS

In isolated optic neuritis, early IFN-β treatment did not influence RNFL thinning nor had it any effect on recovery of visual functions.

Retinal damage in multiple sclerosis disease subtypes measured by high-resolution optical coherence tomography

Background. Optical coherence tomography (OCT) has facilitated characterisation of retinal alterations in MS patients. Only scarce and in part conflicting data exists on different MS subtypes. Objective. To analyse patterns of retinal changes in different subtypes of MS with latest spectral-domain technology. Methods. In a three-centre cross-sectional study 414 MS patients and 94 healthy controls underwent spectral-domain OCT examination. Results. Eyes of MS patients without a previous optic neuritis showed a significant reduction of both retinal nerve fibre layer (RNFL) thickness and total macular volume (TMV) compared to healthy controls independent of the MS subtype (P < 0.001 for all subtypes). RNFL thickness was lower in secondary progressive MS (SPMS) eyes compared to relapsing-remitting MS (RRMS) eyes (P = 0.007), and TMV was reduced in SPMS and primary progressive MS (PPMS) eyes compared to RRMS eyes (SPMS: P = 0.039, PPMS: P = 0.005). Independent of the subtype a more pronounced RNFL thinning and TMV reduction were found in eyes with a previous optic neuritis compared to unaffected eyes. Conclusion. Analysis of this large-scale cross-sectional dataset of MS patients studied with spectral-domain OCT confirmed and allows to generalize previous findings. Furthermore it carves out distinct patterns in different MS subtypes.

Advances in imaging to support the development of novel therapies for multiple sclerosis

Multiple sclerosis (MS) is a common neurological disease in North America and Europe. Although most patients develop major locomotor disability over the course of 15-20 years, in approximately one-third of patients the long-term course is favorable, with minimal disability. Although current disease-modifying treatments reduce the relapse rate, their long-term effects are uncertain. MS treatment trials are challenging because of the variable clinical course and typically slow evolution of the disease. Magnetic resonance imaging (MRI) is sensitive in monitoring MS pathology and facilitates evaluation of potential new treatments. MRI measurements of lesion activity have identified new immunomodulatory treatments for preventing relapse. Quantitative measurements of tissue volume and structural integrity, capable of detecting neuroprotection and repair, should facilitate new treatments designed to prevent irreversible disability. Higher-field MR scanners and new positron emission tomography (PET) radioligands are providing new insights into cellular and pathophysiological abnormalities, and should be valuable in future therapeutic trials. Retinal axonal loss measured using optical coherence tomography (OCT) can assess acute neuroprotection in optic neuritis.