Mimics and chameleons of optic neuritis

Optic neuritis is a common problem and most neurologists are familiar with it. Recent studies have suggested that it can be overdiagnosed in as many as 10% of cases. The major reasons for this relate to confusion regarding terminology and lack of familiarity with common mimics. This article covers typical 'idiopathic' demyelinating optic neuropathy (IDON) and several possible variations in the way it can present (chameleons). We then discuss several conditions that can mimic IDON, including neuromyelitis optica, sarcoidosis, chronic relapsing inflammatory optic neuropathy, anterior ischaemic optic neuropathy, infectious/parainfectious optic neuropathy, neuroretinitis, Leber's hereditary optic neuropathy, and some 'ocular' mimics including autoimmune retinopathy and central serous choroidoretinopathy.