Imaging description

Optic neuritis (ON) is an acute inflammatory process of presumed autoimmune etiology in the majority of the cases. Although it can have diverse etiology, the most common reason is multiple sclerosis (MS). ON can be the first manifestation of MS [1], or could represent neuromyelitis optica (NMO), acute disseminated encephalomyelitis (ADEM), and less likely isolated pediatric ON, which tends to be post-viral, post-vaccination, or due to ADEM. Depending on the geographic cohort, 14% (Japan) to 77% (UK) of patients with ON are subsequently found to have multiple sclerosis [2]. ON is the initial presentation of MS in 15–25% of the patients, while about 70–90% of MS patients develop ON at some point.

The diagnosis of ON is made clinically and confirmed with MRI by demonstrating focal or segmental high T2 signal within a diffusely enlarged optic nerve [3]. On post-contrast imaging, diffuse or central enhancement of optic nerve is seen in about 90% of patients (Fig. 73.1). On diffusion-weighted imaging, there may be decreased diffusivity in the acute stage and increased diffusivity in chronic ON [3,4]. Presence of high T2 and FLAIR signal white matter lesions within the brain is a strong predictor for MS in the setting of ON.