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A 32 year old woman reports blurred vision in her left eye for several days, together with left periocular pain worsened by eye movement. Visual acuity is normal in the right eye, but subnormal in the left eye, which has an afferent pupil defect. The ocular examination, including the optic fundus, is normal. There is no personal or family history of multiple sclerosis (MS) and the patient has no symptoms or signs of MS. The brain MRI scan is normal. This is her orbit MRI. Serum aquaporin antibody and myelin oligodendrocyte antibody tests are negative.

    • Review Topic

    Within 15 years, what is the chance that she will develop clinically-definite MS?

    A) 10%

    Incorrect

    B) 15%

    Incorrect

    C) 20%

    Incorrect

    D) 25%

    Correct! The clinical manifestations are highly suggestive of typical optic neuritis. MRI is the strongest predictor of the chance of developing clinically-definite MS. With no white matter signal abnormalities, the untreated 15-year risk is 25%. When there is at least one signal abnormality typical of demyelination, the risk rises to 75%. The chance of recovering normal or near-normal visual function in the affected eye after a first bout of typical optic neuritis is 85% to 90%. The chance of a recurrence of optic neuritis in either eye over the next 15 years is 30%, evenly split between the previously affected and unaffected eyes. The chance of having long term neurologic disability—including visual disability—is only 10%. Whether treatment of any kind reduces the risks of developing MS in patients with isolated optic neuritis is unsettled; treatment is not currently recommended. Once MS is diagnosed, treatment with immune-modulating drugs probably reduces the pace of the illness.