CSF testing may reveal a mild mononuclear pleocytosis of up to 40 lymphocytes. Patients may have significant conduction defects along visual, somatosensory, and brainstem pathways without clinical complaints. Visual and somatosensory evoked responses have the highest sensitivity. Gadolinium enhancement detects actively demyelinating lesions. An abnormal MRI, without convincing clinical symptoms, cannot be used to make the diagnosis, however, and a normal MRI of the brain and spinal cord, but with a consistent history or examination, does not exclude the diagnosis.
Corticosteroids accelerate the recovery from an exacerbation.
Most exacerbations do not require treatment. Avoid long-term treatment with prednisone or adrenocorticotropic hormone. Individuals with an isolated episode of optic neuritis and MRI evidence of other clinically silent lesions may benefit from a brief course of i.v. methylprednisolone, followed by a rapid oral taper of prednisone. Oral steroids should not be used initially for optic neuritis. Beta-interferon is given by subcutaneous injection every other day.