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

A case of acute macular neuroretinopathy in a pediatric patient with optic neuritis

Introduction

Acute macular neuroretinopathy (AMN) is a retinal disorder caused by ischemia in the deep capillary plexus. There have been several reports of AMN associated with optic neuritis in adults. We report a case of AMN associated with optic neuritis in a pediatric patient.

Case report

A 14-year-old boy presented with ocular pain upon eye movement and decreased vision with disc edema in the right eye, leading to a diagnosis of optic neuritis. After initiating steroid pulse therapy, his visual acuity improved promptly. Optical coherence tomography revealed a hyperreflective area in the outer retina on the nasal side of the macula, and fundus examination showed a reddish-brown, wedge-shaped lesion, confirming the diagnosis of AMN. The case was ultimately diagnosed as myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease. Post-treatment, visual acuity improved; however, a paracentral scotoma attributed to AMN remained.

Discussion and conclusion

The pathogenesis of AMN in cases of optic neuritis may involve mechanical arterial occlusion due to optic disc swelling. Regardless of age, careful fundus examination is necessary during the clinical course of optic neuritis, and MOG-immunoglobulin G testing can be considered for patients showing optic neuritis with AMN.

From BBB to PPP: Bioenergetic requirements and challenges for oligodendrocytes in health and disease

Mature myelinating oligodendrocytes, the cells that produce the myelin sheath that insulates axons in the central nervous system, have distinct energetic and metabolic requirements compared to neurons. Neurons require substantial energy to execute action potentials, while the energy needs of oligodendrocytes are directed toward building the lipid-rich components of myelin and supporting neuronal metabolism by transferring glycolytic products to axons as additional fuel. The utilization of energy metabolites in the brain parenchyma is tightly regulated to meet the needs of different cell types. Disruption of the supply of metabolites can lead to stress and oligodendrocyte injury, contributing to various neurological disorders, including some demyelinating diseases. Understanding the physiological properties, structures, and mechanisms involved in oligodendrocyte energy metabolism, as well as the relationship between oligodendrocytes and neighboring cells, is crucial to investigate the underlying pathophysiology caused by metabolic impairment in these disorders. In this review, we describe the particular physiological properties of oligodendrocyte energy metabolism and the response of oligodendrocytes to metabolic stress. We delineate the relationship between oligodendrocytes and other cells in the context of the neurovascular unit, and the regulation of metabolite supply according to energetic needs. We focus on the specific bioenergetic requirements of oligodendrocytes and address the disruption of metabolic energy in demyelinating diseases. We encourage further studies to increase understanding of the significance of metabolic stress on oligodendrocyte injury, to support the development of novel therapeutic approaches for the treatment of demyelinating diseases.

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.

Optical coherence tomography angiography measurements in multiple sclerosis: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Recent literature on multiple sclerosis (MS) demonstrates the growing implementation of optical coherence tomography-angiography (OCT-A) to discover potential qualitative and quantitative changes in the retina and optic nerve. In this review, we analyze OCT-A studies in patients with MS and examine its utility as a surrogate or precursor to changes in central nervous system tissue.

METHODS

PubMed and EMBASE were systematically searched to identify articles that applied OCT-A to evaluate the retinal microvasculature measurements in patients with MS. Quantitative data synthesis was performed on all measurements which were evaluated in at least two unique studies with the same OCT-A devices, software, and study population compared to controls. A fixed-effects or random-effects model was applied for the meta-analysis based on the heterogeneity level.

RESULTS

The study selection process yielded the inclusion of 18 studies with a total of 1552 evaluated eyes in 673 MS-associated optic neuritis (MSON) eyes, 741 MS without optic neuritis (MSNON eyes), and 138 eyes without specification for the presence of optic neuritis (ON) in addition to 1107 healthy control (HC) eyes. Results indicated that MS cases had significantly decreased whole image superficial capillary plexus (SCP) vessel density when compared to healthy control subjects in the analyses conducted on Optovue and Topcon studies (both P < 0.0001). Likewise, the whole image vessel densities of deep capillary plexus (DCP) and radial peripapillary capillary (RPC) were significantly lower in MS cases compared to HC (all P < 0.05). Regarding optic disc area quadrants, MSON eyes had significantly decreased mean RPC vessel density compared to MSNON eyes in all quadrants except for the inferior (all P < 0.05). Results of the analysis of studies that used prototype Axsun machine revealed that MSON and MSNON eyes both had significantly lower ONH flow index compared to HC (both P < 0.0001).

CONCLUSIONS

This systematic review and meta-analysis of the studies reporting OCT-A measurements of people with MS confirmed the tendency of MS eyes to exhibit reduced vessel density in the macular and optic disc areas, mainly in SCP, DCP, and RPC vessel densities.

The Role of Optical Coherence Tomography Angiography in Optic Nerve Head Edema: A Narrative Review

Optic nerve head (ONH) edema is a clinical manifestation of many ocular and systemic disorders. Ocular and central nervous system imaging has been used to differentiate the underlying cause of ONH edema and monitor the disease course. ONH vessel abnormalities are among the earliest signs of impaired axonal transportation. Optical coherence tomography angiography (OCTA) is a noninvasive method for imaging ONH and peripapillary vessels and has been used extensively for studying vascular changes in ONH disorders, including ONH edema. In this narrative review, we describe OCTA findings of the most common causes of ONH edema and its differential diagnoses including ONH drusen.

Peripapillary Choroid Thickness as a Predisposing Factor for Nonarteritic Anterior Ischemic Optic Neuropathy: A Semiautomated OCT Study

Purpose

The purpose of this study was to investigate the correlations between peripapillary choroidal thickness (PCT) and nonarteritic ischemic optic neuropathy (NAION) by using semiautomated optic coherence tomography (OCT).

Methods

A total of 35 NAION eyes, 29 unaffected fellow eyes, and 40 eyes from an age-matched control group were recruited. Enhanced-depth imaging OCT was performed after the resolution of disc edema. PCT was measured using a customized semiautomated MATLAB program. Regression models adjusted for multiple variables were used to inspect the correlation between mean PCT and NAION.

Results

The mean PCT in NAION eyes, unaffected fellow eyes, and the control group was 197.09 ± 38.09, 196.52 ± 38.47, and 153.53 ± 29.92 µm, respectively. The mean PCT was significantly thicker both in NAION-affected eyes and fellow eyes compared with the control group (P < 0.001). No significant difference existed between NAION-affected eyes and unaffected fellow eyes. The PCT of the superior quadrant was significantly thicker than that of the inferior quadrant in all three groups. In the multivariate logistic regression, PCT was the only predisposing factor for NAION. However, the value of the PCT was not correlated with final visual outcomes.

Conclusions

With a semiautomated program to alleviate the missing measurements, our study demonstrated significantly thicker PCT in both NAION-affected and unaffected eyes of patients, which indicated that peripapillary pachychoroid is a predisposing factor for NAION but may not be a prognostic factor for visual outcomes.

Translational Relevance

Accurate measurement of PCT by using semiautomated OCT illustrates the correlation between choroidal vasculature and NAION.

Oxidative Stress in Optic Neuropathies

Increasing evidence indicates that changes in the redox system may contribute to the pathogenesis of multiple optic neuropathies. Optic neuropathies are characterized by the neurodegeneration of the inner-most retinal neurons, the retinal ganglion cells (RGCs), and their axons, which form the optic nerve. Often, optic neuropathies are asymptomatic until advanced stages, when visual impairment or blindness is unavoidable despite existing treatments. In this review, we describe systemic and, whenever possible, ocular redox dysregulations observed in patients with glaucoma, ischemic optic neuropathy, optic neuritis, hereditary optic neuropathies (i.e., Leber's hereditary optic neuropathy and autosomal dominant optic atrophy), nutritional and toxic optic neuropathies, and optic disc drusen. We discuss aspects related to anti/oxidative stress biomarkers that need further investigation and features related to study design that should be optimized to generate more valuable and comparable results. Understanding the role of oxidative stress in optic neuropathies can serve to develop therapeutic strategies directed at the redox system to arrest the neurodegenerative processes in the retina and RGCs and ultimately prevent vision loss.

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.

Different alteration patterns of sub-macular choroidal thicknesses in aquaporin-4 immunoglobulin G antibodies sero-positive neuromyelitis optica spectrum diseases and isolated optic neuritis

PURPOSE

The ocular choroid is a sensitive biomarker of vascular perfusion in optic neuritis (ON) patients due to its vascular structures. The purpose of this study was to evaluate alterations in sub-macular choroidal thicknesses (sub-MCT) in aquaporin-4 immunoglobulin G antibodies (AQP4-IgG) sero-positive neuromyelitis optica spectrum disease (AQP4-IgG+/NMOSD) and isolated ON (ION) patients using optical coherence tomography (OCT).

METHODS

A total of 208 ON patients (275 eyes) and healthy controls (HCs) who underwent sub-MCT and retinal microstructure detection with OCT were enrolled in this study.

RESULTS

Among all the ON patients, 102 (49.0%) cases were identified as serum AQP4-IgG-positive, with 106 (51.0%) cases being negative, excluding multiple sclerosis as the ION cohort. The sub-MCT in the AQP4-IgG+/NMOSD patients decreased in 0-6 months after ON attacks. However, for the ION cohort, the sub-MCT decreased in 0-2 months and then stayed normal or slightly increased in 2-4 months after the first ON attack, finally sharply decreasing after 6 months. For unilateral AQP4-IgG+/NMOSD patients, eyes without ON also presented retinal layer thinning and sub-MCT slight reduction independent of ON attacks.

CONCLUSIONS

The sub-MCT in AQP4-IgG+/NMOSD patients were reduced at all stages of ON, which distinguished the ION patients as decreasing only at chronic stage of ON. It implied that ocular vascular hypoperfusion plays a potential role in ON pathogenesis and the different patterns could be caused by the distinct pathogenesis of AQP4-IgG+/NMOSD and ION.

Increased Levels of Endothelin-1 in Cerebrospinal Fluid Are a Marker of Poor Visual Recovery after Optic Neuritis in Multiple Sclerosis Patients

Background

Multiple sclerosis (MS), a chronic inflammatory and degenerative disease of the central nervous system, typically features immune-mediated focal demyelination and secondary axonal degeneration. Cerebral hypoperfusion of the normal-appearing white matter (NAWM) has been reported in MS patients and may be mediated by elevated levels of endothelin-1 (ET-1), a most potent vasoconstrictive peptide released from reactive astrocytes in MS focal lesions. Optic neuritis (ON) is one of the most frequent manifestations of MS and also shows peripapillary vascular hypoperfusion in combination with disc swelling.

Aims

We aimed to compare serum and cerebrospinal fluid (CSF) levels of ET-1 as a potential prognostic marker of MS-ON in two groups of patients differing for severity of MS-ON clinical presentation.

Materials and Methods

A cross-sectional study to compare serum and CSF levels of ET-1 between patients with clinically aggressive MS-ON (A-MS-ON) and nonaggressive MS-ON (NA-MS-ON) according to conventional ophthalmological criteria, including optical coherence tomography. CSF and serum concentrations of ET-1 were measured using a commercially available ELISA method.

Results

Sixteen patients consecutively referred to the Units of Neurology for visual disturbances attributable to MS were recruited, 11 (69%) patients with A-MS-ON and 5 (31%) with NA-MS-ON. Median CSF ET-1 levels and CSF/serum ET-1 quotient were significantly higher in patients with A-MS-ON (0.30 vs. 0.56 ng/ml) as compared to NA-MS-ON (0.16 vs. 0.16).

Conclusions

Severity and failure in the recovery from ON in MS patients may depend from vascular hypoperfusion of the optic nerve induced by high intrathecally produced ET-1, a potential prognostic marker of ON recovery in MS. The detection of CSF ET-1 levels may allow identifying groups of ON patients potentially benefitting from treatment with ET-1 antagonists (e.g., bosentan).

A new association: acute macular neuroretinopathy in acute optic neuritis

Background

Acute optic neuritis (AON) is a common optic nerve disease leading to retrograde degeneration of optic nerve axons, reflected by thinning of the inner retinal layers on optical coherence tomography. On the contrary, acute macular neuroretinopathy (AMN) type 2 is a rare outer retinal disorder that leads to thinning of the outer nuclear layers and is diagnosed by multimodal imaging. The aim of this study was to report a new association between these two diseases.

Methods

Patients with a first episode of optic neuritis were invited to participate in a study that involved optical coherence tomography evaluation at baseline and the following 1, 3, 6 and 12 months. All the study patients underwent ophthalmologic evaluation that comprised of visual acuity, visual field and multimodal imaging as well as orbital and brain Magnetic Resonance Imaging. A diagnosis of multiple sclerosis was made according to the 2010 McDonald criteria.

Results

Six of the 114 patients with acute optic neuritis also had acute macular neuroretinopathy, of whom three were positive for myelin oligodendrocyte glycoprotein antibodies (MOG‐Abs), two had relapsing–remitting multiple sclerosis and one had clinical isolated syndrome.

Conclusion

Our study suggests that it is imperative to check for associated AMN in cases of AON, especially those associated with MOG‐Abs.

Peripapillary and macular choroidal thickness in both eyes of patients with acute unilateral retrobulbar optic neuritis

PURPOSE

The purpose of this study was to examine macular and peripapillary choroidal thickness (CT) in patients with acute unilateral retrobulbar optic neuritis.

MATERIALS AND METHODS

In this cross-sectional study, 19 patients with acute unilateral retrobulbar optic neuritis were examined. A control group was matched with patients for sex and age. Enhanced depth imaging optical coherence tomography in macula and peripapillary areas in both eyes was performed for evaluation of CT. The CT was measured in subfoveal and other six points of macula and four points of peripapillary areas with a 3.4-mm scan circle centered on the optic nerve head.

RESULTS

The mean subfoveal CT was 384.7 ± 101.6 μm, 380.5 ± 109 μm, and 401.2 ± 84.6 μm for affected eye, unaffected fellow eye, and healthy control, respectively. All measurements of macular CT were thinner in the patient group compared with healthy controls. Global peripapillary CT in affected eyes, unaffected fellow eyes, and healthy controls were 202 ± 43.3, 195.1 ± 42.9, and 234 ± 71.2, respectively. The difference between the three groups was statistically significant in the nasal point of peripapillary area (P = 0.023). No correlation was seen between CT and initial visual acuity or duration from symptom onset to medical survey in acute phase of retrobulbar optic neuritis.

CONCLUSION

Patients with acute retrobulbar optic neuritis showed no significantly thinner macular and peripapillary CT in both eyes compared with healthy controls.