Differential diagnoses to MS: experiences from an optic neuritis clinic.

Optic neuritis (ON) is closely linked to multiple sclerosis (MS). It may, however, also be associated to a range of autoimmune or infectious diseases. The purpose of this study was to assess the differential diagnoses in patients with suspected ON. In this retrospective study, we reviewed the files of all patients referred to the Clinic of Optic Neuritis, Glostrup Hospital, University of Copenhagen, Denmark, between January 2000 and November 2011. All patients were referred by ophthalmologists with possible ON. Patients diagnosed with MS prior to referral were excluded from the study. A total of 643 patients were included in the study. Apart from ON, the most frequent diagnoses were tumors (n = 15), ischemic or hypertensive neuropathies (n = 13), and retinal or choroid disorders (n = 9). Six patients were diagnosed with neuromyelitis optica. Rarer causes of visual loss were infections (n = 5), giant cell arteritis (n = 4), sarcoidosis (n = 3), thyrotoxicosis (n = 2), and hereditary or toxic neuropathies (n = 2). Nine percent of patients referred to the Clinic of Optic Neuritis had symptoms caused by medical, neurosurgical or ophthalmic disorders, and 0.9 % of our patients had NMO. Though most of these conditions are rare, it is of importance to keep them in mind upon encountering patients with symptoms of ON.