Quantitative characterization of optic nerve atrophy in patients with multiple sclerosis

Abstract

BackgroundOptic neuritis (ON) is one of the most common presentations of multiple sclerosis (MS). Magnetic resonance imaging (MRI) of the optic nerves is challenging because of retrobulbar motion, orbital fat and susceptibility artifacts from maxillary sinuses; therefore, axonal loss is investigated with the surrogate measure of a single heuristically defined point along the nerve as opposed to volumetric investigation.ObjectiveThe objective of this paper is to derive optic nerve volumetrics along the entire nerve length in patients with MS and healthy controls in vivo using high-resolution, clinically viable MRI.MethodsAn advanced, isotropic T2-weighted turbo spin echo MRI was applied to 29 MS patients with (14 patients ON+) or without (15 patients ON–) history of ON and 42 healthy volunteers. An automated tool was used to estimate and compare whole optic nerve and surrounding cerebrospinal fluid radii along the length of the nerve.Results and conclusionOnly ON+ MS patients had a significantly reduced optic nerve radius compared to healthy controls in the central segment of the optic nerve. Using clinically available MRI methods, we show and quantify ON volume loss for the first time in MS patients.

Atrophy of optic nerve detected by transorbital sonography in patients with demyelinating diseases of the central nervous system

“…As history of previous ON was found to be associated with reduced OND and ONSD (Table 2) and patients with acute ON were found to have higher rates of previous ON (Table 1), it could be hypothesized that any potential thickening of the retrobulbar portion of the optic nerve in the setting of acute ON was counterbalanced by the previously induced optic nerve atrophy as a result of past ON episodes [15,16]. Indeed, in a further analysis comparing patients with first episode to the group of patients with recurrent episodes of ON, a significant difference regarding the OND was identified.…”

Optic Chiasm Morphometric Changes in Multiple Sclerosis: Feasibility of a Simplified Brain Magnetic Resonance Imaging Measure of White Matter Atrophy

“…One important question that should be raised in interpretation of our results is whether the observed atrophy of the OC was owing to direct extension of the atrophic process (retrograde degeneration) from the adjacent ONs in association with optic neuritis, rather than a reflection on generalized brain atrophy associated with MS. We had hypothesized the latter, and indeed somewhat simplistically (in the context of this proof‐of‐principle study), avoided factoring in the presence or absence of ON optic neuritis precisely because it had been shown previously by Harrigan et al () that there was no difference in size of the ONs closest to insertion into the OC in MS patients, whether with or without prior optic neuritis—although both were thinner than in normal subjects. We acknowledge however that the issue may be much more complex as to whether the OC dimensions may be more affected by pathological involvement in the adjacent ON versus global WM atrophy that accompanies MS. For instance, Blanc et al () found atrophy of the OC in patients with neuromyelitis optica.…”

“…The OC is a WM structure that is often clearly visible on routine MRI and is anatomically related to the ONs, which are known to be affected in MS patients, whether with and without optic neuritis (Harrigan et al, ). In this study, we evaluated the morphometry of the OC in normal and MS patients to determine the feasibility of establishing a morphometric measure of atrophy that would be easier to derive than separate ON evaluation for atrophy, and that could potentially be obtained on routine clinical diagnostic MRI scans.…”

“…In chronic MS, evoked potential studies show evidence of ON involvement in 90% of patients, and the postmortem ON is atrophic in patients with chronic optic neuritis, and to a lesser extent in MS patients without optic neuritis (Harrigan et al, ). Although Harrigan et al () showed that differences in ON diameter between 42 healthy subjects and 28 patients with relapsing remitting MS without a history of optic neuritis were not statistically significant, their MS patients demonstrated overall thinner ONs. However, implementation of specific imaging of the ONs in combination with standard brain imaging is impractical on a routine basis owing to the complexity of this anatomical region and its surrounding structures (Fadzli et al, ; Storoni et al, ), the necessary additional imaging sequences that would be required for a dedicated examination of the ONs, or the need for volumetric imaging followed by post‐processing segmentation analysis (Harrigan et al, ).…”

“…As an alternative, the anterior visual pathway may offer a compelling model for the evaluation of inflammatory or demyelinating disease elsewhere within the CNS. Previous studies had shown that the extent of optic nerve (ON) atrophy may be useful in determining the stage of optic neuritis and for the following axonal loss over time (Youl et al, ; Frohman et al, ; Galetta et al, ; Harrigan et al, ). Optic neuritis is in fact the first and most common clinical sign of MS, occurring in 38% of diagnosed patients (Swanson, ; Harrigan et al, ).…”