Magnetic resonance imaging of optic perineuritis.

Optic perineuritis, an uncommon variant of orbital pseudotumor, may be clinically indistinguishable from retrobulbar optic neuritis. Because treatment and prognosis for these two entities are different, early diagnosis is important. We report a case of a 47 year-old woman with clinical findings suggestive of retrobulbar optic neuritis, but whose magnetic resonance images suggested optic perineuritis. A dramatic clinical response to oral corticosteroids was observed. Optic perineuritis should be considered in cases of presumed retrobulbar optic neuritis. MRI may differentiate these two entities in the acute stage, and should be considered before treatment is decided.