The contribution of magnetic resonance imaging in the differential diagnosis of optic nerve damage

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.

Detection of lesions in the optic nerve with magnetic resonance imaging using a 3D convolutional neural network

BACKGROUND

Optic neuritis (ON) is one of the first manifestations of multiple sclerosis, a disabling disease with rising prevalence. Detecting optic nerve lesions could be a relevant diagnostic marker in patients with multiple sclerosis.

OBJECTIVES

We aim to create an automated, interpretable method for optic nerve lesion detection from MRI scans.

MATERIALS AND METHODS

We present a 3D convolutional neural network (CNN) model that learns to detect optic nerve lesions based on T2-weighted fat-saturated MRI scans. We validated our system on two different datasets (N = 107 and 62) and interpreted the behaviour of the model using saliency maps.

RESULTS

The model showed good performance (68.11% balanced accuracy) that generalizes to unseen data (64.11%). The developed network focuses its attention to the areas that correspond to lesions in the optic nerve.

CONCLUSIONS

The method shows robustness and, when using only a single imaging sequence, its performance is not far from diagnosis by trained radiologists with the same constraint. Given its speed and performance, the developed methodology could serve as a first step to develop methods that could be translated into a clinical setting.

Bilateral swollen optic nerve head etiology and management: A cross-sectional study

Background

The differential diagnosis of optic disc edema varies according to the presence of unilateral or bilateral edema. Papilledema may occur due to benign and life-threatening causes, but even benign causes may leave serious consequences for vision if not treated emergently. This study aimed to find out the prevalence of these causes in two major hospitals in Syria and observing the response of edema to treatment within a month and how visual acuity can be saved if edema is treated urgently.

Methods

This cross-sectional study was conducted in Al-Assad and Al-Mowasat Hospitals in Syria from October 2020 to the beginning of February 2022. It included 50 patients who had bilateral optic disc edema. Then a full study was carried out to reach the diagnosis and management appropriately and to monitor the extent of the efficacy of conservative measure in reducing edema, and how many of them needed surgical intervention.

Results

the study included 50 patients, 13 males and 37 females, the most common diagnosis was venous sinus thrombosis (12 cases with 24%), followed by idiopathic intracranial hypertension and tumors (10 cases each by 20%), infectious meningitis (8 cases by 16%), leptomeningeal metastasis (5 cases by 10%), arterial hypertension (3 cases by 6%) and autoimmune meningitis (2 by 4%). Edema improved after management within a month in most patients (37 patients by 74%) and edema was accompanied by low visual acuity in 21 patients (42%). 20 patients (40%) needed surgical intervention. Visual acuity reduced in 10 patients (20%) despite all treatments.

Conclusion

venous sinus thrombosis is the most common cause of bilateral optic disc edema then idiopathic intracranial hypertension and tumors, and despite the provision of all treatments, the visual acuity of 20% of patients has decreased.

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This cross-sectional study was conducted in Al-Assad and Al-Mouawsat Hospitals in Damascus.

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The study included 50 patients, 37 females, the most common diagnosis was venous sinus thrombosis (12 cases).

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Edema was accompanied by low visual acuity in 21 patients (42%).

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Edema improved after management within a month in most patients (37 patients).

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20 patients needed surgical intervention and Visual acuity reduced in 10 patients despite all treatments.

Diffusion-Weighted Imaging and Post-contrast Enhancement in Differentiating Optic Neuritis and Non-arteritic Anterior Optic Neuropathy

Non-arteritic anterior ischaemic optic neuropathy (NAION) and optic neuritis (ON) may be difficult to distinguish early in their disease courses. Our goal was to determine if specific magnetic resonance imaging characteristics differentiate acute NAION from ON. Neuroradiologists, masked to diagnosis, reviewed the diffusion-weighted imaging (DWI) and post-contrast enhancement (PCE) characteristics of the optic nerve in 140 eyes. PCE and DWI signals of the optic disc alone did not discriminate between NAION and ON. After taking age and sex into consideration, only DWI and PCE of the intraorbital segment of the optic nerve differentiated the two, with ON having the increased likelihood of these findings. Isolated PCE without DWI signal at the optic disc, however, was 100% specific for NAION. This may be the most specific way to radiographically differentiate between NAION and ON in the acute setting.

Role of coronal high-resolution diffusion-weighted imaging in acute optic neuritis: a comparison with axial orientation

PURPOSE

Through a comparison with the axial orientation, we aimed to evaluate the role of coronal high-resolution diffusion-weighted imaging (DWI) in acute optic neuritis based on diagnostic accuracy and the reproducibility of apparent diffusion coefficient (ADC) measurements.

METHODS

Orbital DWI, using readout-segmented, parallel imaging, and 2D navigator-based reacquisition (RESOLVE-DWI), was performed on 49 patients with acute vision loss. The coronal (thickness = 3 mm) and axial (thickness = 2 mm) diffusion images were evaluated by two neuroradiologists retrospectively. The sensitivity, specificity, and accuracy were calculated through diagnostic test; the inter- and intra-observer reliabilities were assessed with a weighted Cohen's kappa test. In addition, the agreement of ADC measurement among observers was evaluated by the intra-class correlation coefficient (ICC), coefficient of variation (CV), and Bland-Altman plots. Comparison of ADC values was also performed by unpaired t test.

RESULTS

Among the 49 patients, 47 clinically positive optic nerves and 51 clinically negative optic nerves were found. The sensitivity, specificity, and accuracy were 85.1/87.2%, 90.2/94.12%, and 87.8/90.8%, respectively, for coronal RESOLVE-DWI and 83.0/85.1%, 66.7/76.5%, and 75.5/79.6%, respectively, for axial RESOLVE-DWI. The inter-observer kappa values were 0.710 and 0.806 for axial and coronal RESOLVE-DWI, respectively, and the intra-observer kappa values were 0.822 and 0.909, respectively (each P < 0.0001). Regarding the reproducibility of ADC measurements on axial and coronal RESOLVE-DWI, the ICCs among observers were 0.846 and 0.941, respectively, and the CV values were 7.046 and 4.810%, respectively. Bland-Altman plots revealed smaller inter-observer variability on coronal RESOLVE-DWI. ADC values were significantly lower in positive group (each P < 0.0001).

CONCLUSION

Higher specificity and better reproducibility of ADC measurements were found for coronal RESOLVE-DWI, which demonstrated the feasibility of the use of coronal RESOLVE-DWI to examine acute optic neuritis patients.

Diffusion-weighted imaging using readout-segmented echo-planar imaging, parallel imaging, and two-dimensional navigator-based reacquisition in detecting acute optic neuritis

PURPOSE

To evaluate the accuracy of diffusion-weighted imaging (DWI) in comparison to contrast-enhanced, fat-suppressed T1 -weighted imaging (CET1WI) in detecting acute optic neuritis (ON).

MATERIALS AND METHODS

The clinical data and magnetic resonance imaging (MRI) findings of 42 patients who presented with decreased vision were retrospectively reviewed. Both 3.0T MRI DWI and CET1WI orbital imaging studies were performed. Two neuroradiologists independently evaluated the DWI and CET1WI. The sensitivity, specificity, and accuracy of the DWI and CET1WI were individually calculated using the clinical diagnosis as the reference standard. The interobserver and intraobserver reliability of DWI and CET1WI were assessed by using a weighted Cohen's kappa (κ) test; a value of P < 0.05 was set as the threshold for statistical significance.

RESULTS

Of the 42 patients, 34 patients (41 nerves) had clinically confirmed acute ON, two had ischemic optic neuropathy, and three had chronic recurrent ON. The sensitivities of DWI and CET1WI for acute ON were 82.9-82.9% and 68.3-85.4%, respectively; the specificities were 81.4-83.7% and 79.1-93.0%, respectively; and the accuracies were 82.1-83.3% and 82.1-90.0%, respectively. The interobserver kappa values were 0.596-0.643 and 0.694-0.734 for DWI and CET1WI, respectively; the intraobserver kappa values were 0.809-0.905 and 0.834-0.924 for DWI and CET1WI, respectively (each P < 0.0001).

CONCLUSION

Given that its sensitivity and specificity are similar to those of dedicated CET1WI for acute ON, DWI can play an important complementary role in detecting acute ON, especially in atypical ON cases, and can provide a quantitative modality that can be used to evaluate axonal damage in the optic nerves.

Neuroimaging in ophthalmology

In the past three decades, there have been countless advances in imaging modalities that have revolutionized evaluation, management, and treatment of neuro-ophthalmic disorders. Non-invasive approaches for early detection and monitoring of treatments have decreased morbidity and mortality. Understanding of basic methods of imaging techniques and choice of imaging modalities in cases encountered in neuro-ophthalmology clinic is critical for proper evaluation of patients. Two main imaging modalities that are often used are computed tomography (CT) and magnetic resonance imaging (MRI). However, variations of these modalities and appropriate location of imaging must be considered in each clinical scenario. In this article, we review and summarize the best neuroimaging studies for specific neuro-ophthalmic indications and the diagnostic radiographic findings for important clinical entities.

Acute postretinal blindness: ophthalmologic, neurologic, and magnetic resonance imaging findings in dogs and cats (seven cases)

OBJECTIVE

To describe the ophthalmologic, neurologic, and magnetic resonance imaging (MRI) findings of seven animals with acute postretinal blindness as sole neurologic deficit.

METHODS

Medical records were reviewed to identify dogs and cats with postretinal blindness of acute presentation, that had a cranial MRI performed as part of the diagnostic workup. Only animals lacking other neurologic signs at presentation were included. Complete physical, ophthalmic, and neurologic examinations, routine laboratory evaluations, thoracic radiographs, abdominal ultrasound, electroretinography, and brain MRI were performed in all animals. Cerebrospinal fluid analysis and postmortem histopathologic results were recorded when available.

RESULTS

Four dogs and three cats met the inclusion criteria. Lesions affecting the visual pathways were observed on magnetic resonance (MR) images in six cases. Location, extension, and MRI features were described. Neuroanatomic localization included: olfactory region with involvement of the optic chiasm (n = 4), pituitary fossa with involvement of the optic chiasm and optic tracts (n = 1), and optic nerves (n = 1). Of all lesions detected, five were consistent with intracranial tumors (two meningiomas, one pituitary tumor, two nasal tumors with intracranial extension), and one with bilateral optic neuritis that was confirmed by cerebrospinal fluid analysis. Histologic diagnosis was obtained in four cases and included one meningioma, one pituitary carcinoma, one nasal osteosarcoma, and one nasal carcinoma.

CONCLUSIONS

Central nervous system (CNS) disease should be considered in dogs and cats with acute blindness, even when other neurologic deficits are absent. This study emphasizes the relevance of MRI as a diagnostic tool for detection and characterization of CNS lesions affecting the visual pathways.

Optic neuritis in evolution

A case of progressive optic neuropathy in a woman with a history of breast cancer is presented. Differential diagnoses including optic neuritis, infiltrative optic neuropathy, carcinomatous meningitis, and toxic optic neuropathies are discussed. Risk factors for metastatic brain lesions are also discussed.

Pathology-guided MR analysis of acute and chronic experimental allergic encephalomyelitis spinal cord lesions at 1.5T

PURPOSE

To directly correlate spinal cord pathology of guinea pigs with experimental allergic encephalomyelitis (EAE) to the MRI data obtained at 1.5T.

MATERIALS AND METHODS

Spinal cords from EAE animals were imaged in vivo with the following MRI sequences: T2-FSE, PD-FSE, fluid-attenuated inversion recovery (FLAIR)-FSE, T2-CSE, T1-CSE, T1-CSE + gadolinium-DTPA (Gd-DTPA), PD-CSE, and short-tau inversion recovery (STIR)-FSE. The spinal cords were removed and the lesions with specific pathological compositions were identified by histological analysis. Regions of interest (ROIs) were drawn on the corresponding MR images, and signal-to-noise ratios (SNRs) were measured for each MR sequence and compared with controls.

RESULTS

The receiver operating characteristic (ROC) analysis of STIR-FSE and PD-CSE was able to differentiate tissue that contained cellular infiltrates with a high degree of accuracy. The SNRs of T2-FSE, STIR-FSE, T2-CSE, PD-CSE, and T1-CSE + Gd-DTPA were elevated in lesions that contained cellular infiltrates alone, whereas the SNRs of PD-CSE and T1-CSE + Gd-DTPA were reduced in demyelinated lesions that also contained inflammation.

CONCLUSION

The SNR difference between the two lesion groups suggests that the combination of STIR-FSE, PD-CSE, and T1-CSE + Gd-DTPA sequences may be useful for differentiating inflammatory lesions containing demyelination from lesions with inflammation alone.

Management of acute optic neuritis

Optic neuritis is a common condition that causes reversible loss of vision. It can be clinically isolated or can arise as one of the manifestations of multiple sclerosis. Occasional cases are due to other causes, and in these instances management can differ radically. The treatment of optic neuritis has been investigated in several trials, the results of which have shown that corticosteroids speed up the recovery of vision without affecting the final visual outcome. Other aspects of management, however, are controversial, and there is uncertainty about when to investigate and when to treat the condition. Here we review the diagnostic features of optic neuritis, its differential diagnosis, and give practical guidance about management of patients. The condition's association with multiple sclerosis will be considered in the light of studies that define the risk for development of multiple sclerosis and with respect to results of trials of disease-modifying drugs in these individuals.

Nitric oxide toxicity in CNS white matter: an in vitro study using rat optic nerve

Excessive nitric oxide formation may contribute to the pathology occurring in diseases affecting central white matter, such as multiple sclerosis. The rat isolated optic nerve preparation was used to investigate the potential toxicity of the molecule towards such tissue. The nerves were exposed to a range of concentrations of different classes of nitric oxide donor for up to 23 h, with or without a subsequent period of recovery, and the damage assessed by quantitative histological methods. Degeneration of axons and macroglia occurred in a time- and concentration-dependent manner, the order of susceptibility being: axons>oligodendrocytes>astrocytes. Use of NONOate donors differing in half-life indicated that nitric oxide delivered in an enduring manner at relatively low concentration was more toxic than the same amount supplied rapidly at high concentration. The mechanism by which nitric oxide affects axons was studied using a donor [3-(n-propylamino)propylamine/NO adduct, PAPA/NO] with an intermediate half-life that produced selective axonopathy after a 2-h exposure (plus 2 h recovery). Axon damage was abolished if, during the exposure, Na(+) or Ca(2+) was removed from the bathing medium or the sodium channel inhibitors tetrodotoxin or BW619C89 (sipatrigine) were added. In electrophysiological experiments, the donor elicited a biphasic depolarisation. The second, larger component (occurring after 7-10 min) was associated with a block of nerve conduction and could be inhibited by tetrodotoxin. Coincident with the secondary depolarisation was a reduction in ATP levels by about 50%, an effect that was also inhibited by tetrodotoxin. It is concluded that nitric oxide, in submicromolar concentrations, can kill axons and macroglia in white matter. The findings lend support to the hypothesis that nitric oxide may be of importance to white matter pathologies, particularly those in which inducible nitric oxide synthase is expressed. The axonopathy, at least when elicited over relatively short time intervals, is likely to be caused by metabolic inhibition. As in anoxia and anoxia/aglycaemia, nitric oxide-induced destruction of axons is likely to be caused by the Ca(2+) overload that follows a reduction in ATP levels in the face of continued influx of Na(+) through voltage-dependent channels.