Optic Neuritis (ON)

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Diagnosis Definition

Optic neuritis (ON) is classically a demyelinating process of the optic nerve, presenting as orbital pain, decreased vision or dyschromatopsia (change in color perception) that progresses over several days
Of patients presenting with ON, 40% are eventually diagnosed with multiple sclerosis
In the setting of neuromyelitis optica (which affects the optic nerve and spinal cord), the ON changes are often bilateral

Imaging Findings

On T2-weighted MR images, the optic nerve will be asymmetrically bright and may be mildly enlarged
T1 post-contrast imaging will show enhancement of the nerve
In the chronic phase, the nerve will atrophy, best demonstrated on thin-section fluid sensitive sequences

Pearls

In the presence of ON, it is important to evaluate the brain for lesions disseminated in space (i.e., separate lesions in the subcortical, juxtacortical, and infratentorial brain/spinal cord) and time (i.e., enhancing and nonenhancing lesions) according to the revised McDonald Criteria for multiple sclerosis
Differential considerations for ON include optic nerve glioma (marked enlargement of the nerve) and optic nerve sheath meningioma (calcification and thickened enhancement of the nerve sheath but a normal nerve)

References

Khanna S, Sharma A, Huecker J, Gordon M, Naismith RT, Van Stavern GP. Magnetic resonance imaging of optic neuritis in patients with neuromyelitis optica versus multiple sclerosis. Journal of Neuro-Ophthalmology 2012; 32(3):216-20
Polman CH, Reingold SC, Banwell B, Clanet M, Cohen JA, Filippi M, Fujihara K, Havrdova E, Hutchinson M, Kappos L, Lublin FD. Diagnostic criteria for multiple sclerosis: 2010 revisions to the McDonald criteria. Annals of Neurology 201; 69(2):292-302

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