MOG antibody-associated optic neuritis

Abstract

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is a demyelinating disorder, distinct from multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD). MOGAD most frequently presents with optic neuritis (MOG-ON), often with characteristic clinical and radiological features. Bilateral involvement, disc swelling clinically and radiologically, and longitudinally extensive optic nerve hyperintensity with associated optic perineuritis on MRI are key characteristics that can help distinguish MOG-ON from optic neuritis due to other aetiologies. The detection of serum MOG immunoglobulin G utilising a live cell-based assay in a patient with a compatible clinical phenotype is highly specific for the diagnosis of MOGAD. This review will highlight the key clinical and radiological features which expedite diagnosis, as well as ancillary investigations such as visual fields, visual evoked potentials and cerebrospinal fluid analysis, which may be less discriminatory. Optical coherence tomography can identify optic nerve swelling acutely, and atrophy chronically, and may transpire to have utility as a diagnostic and prognostic biomarker. MOG-ON appears to be largely responsive to corticosteroids, which are often the mainstay of acute management. However, relapses are common in patients in whom follow-up is prolonged, often in the context of early or rapid corticosteroid tapering. Establishing optimal acute therapy, the role of maintenance steroid-sparing immunotherapy for long-term relapse prevention, and identifying predictors of relapsing disease remain key research priorities in MOG-ON.

Fig. 1. Localisation of visual pathway involvement in MOG-ON, AQP4-ON and MS-ON.

A MOG-ON (red): Typical features include bilateral longitudinally extensive ON, with optic disc swelling, involvement of the retrobulbar segment of the optic nerve, and optic nerve sheath involvement or optic perineuritis. B AQP4-ON (blue): Longitudinally extensive ON, with optic chiasm +/− optic tract involvement. C MS-ON (green): focal ON. AQP4 aquaporin 4, MOG myelin oligodendrocyte glycoprotein, MS multiple sclerosis, ON optic neuritis.

Fig. 2. Clinical and radiological characterisation of MOG antibody-associated optic neuritis.

A Bilateral optic nerve head swelling and oedema visualised on fundoscopy in a patient with a first presentation of MOGAD. B Unilateral left optic nerve T2 hyperintensity (arrow) (Cor T2). C Unilateral right sided longitudinally extensive optic neuritis (arrow) with associated T2 hyperintensity and swelling (Ax T2). D During acute left optic neuritis, swelling resulted in increased periparillary retinal nerve fibre layer (RNFL – yellow) thickness on optical coherence tomography. E Bilateral optic neuritis (arrows) with marked T2 hyperintensity (Cor T2 FS). F Bilateral longitudinally extensive optic neuritis (arrows) with gadolinium enhancement (Ax T1 FS Gad). G Visual field testing with dense peripheral constriction and relative central sparing in a pattern strongly suggestive of optic perineuritis. H Right optic perineuritis (arrow) with optic nerve sheath inflammation and enhancement (Cor T1 FS Gad). I Right optic perineuritis with extension of enhancement into intraorbital fat (arrow) (Cor T1 FS Gad). Figure 1A, G was reproduced from Ramanathan et al. [63] with permission from John Wiley and Sons. Ax axial, Cor coronal, FS fat suppressed, Gad gadolinium enhancement, MOGAD myelin oligodendrocyte glycoprotein antibody-associated disease, OS oculus sinister (left eye), RNFL retinal nerve fibre layer.