How is optic neuritis in suspected MS typically presented, and what is the first-line diagnostic test?

• A. Acute unilateral vision loss with eye pain on movement; first-line diagnostic test is MRI of the brain (and orbits) with gadolinium.
• B. Bilateral vision loss with no eye pain; EEG.
• C. Chronic progressive vision loss; CT head.
• D. Vision loss with papilledema; LP.

Answer: (A)

Optic neuritis in suspected multiple sclerosis most often presents as sudden, unilateral vision loss with eye pain that worsens with eye movement. This combination is highly characteristic because inflammation of the optic nerve typically causes pain during movement and rapid loss of vision.

The first-line diagnostic test is MRI of the brain and orbits with gadolinium. MRI is the most sensitive test for detecting demyelinating lesions of MS, including optic nerve involvement, and it helps establish dissemination in space (lesions in multiple CNS regions) and dissemination in time (new or enhancing lesions over time). Other tests like EEG or CT are not as helpful for diagnosing MS-related optic neuritis, and while lumbar puncture can support the diagnosis with CSF findings (like oligoclonal bands), it is not the initial test.