The optic neuritis is seen in about one third of multiple sclerosis. Moreover, nearly 50% or greater (45- 80%) of patients with optic neuritis will develop multiple sclerosis within 15 years and the optic neuritis may be the only manifestation of multiple sclerosis.
The main differential diagnosis of MS with optic neuritis is the neuromyelitis optica (NMO); the main differential points are:
Optic nerve involvement in NMO is typically bilateral with possible involvement of the chiasm while unilateral in MS
The spinal cord involvement is typical and extensive usually extending to more than three vertebral levels and is central in distribution - MS spinal cord lesions (15% spinal cord involvement in MS) are short, focal and peripheral in location
Brain is typically normal in NMO, however different demyelinating lesions are reported