The natural history of recurrent optic neuritis.

BACKGROUND Optic neuritis (ON) may occur in isolation or may herald multiple sclerosis (MS) or neuromyelitis optica (NMO). Occasionally, ON may recur many times without intervening evidence of dissemination in space. OBJECTIVE To define the clinical course and prognosis of patients with recurrent ON. DESIGN Retrospective medical record review and telephone follow-up survey. SETTING Clinic-based practice in a large tertiary referral institution. MAIN OUTCOME MEASURES Survival analysis of conversion to MS and NMO and final visual impairment. We studied the association of clinical and demographic factors, the presence of brain lesions on magnetic resonance images, and the use of corticosteroid treatment at the time of the first ON occurrence with conversion to MS and NMO. RESULTS We identified 1274 patients with ON between 1994 and 2000 and selected 72 (5.7%) with recurrent ON without intervening symptoms of a disseminated demyelinating condition for further analysis. The 5-year conversion rate to NMO was 12.5% and to MS, 14.4%. Among 5 patients with 2 or more lesions consistent with MS on brain magnetic resonance images, 2 (40.0%) converted to MS and none to NMO, while among 11 patients without such lesions, none converted to MS and 2 (18.2%) converted to NMO (P =.16). Conversion to MS occurred in 7 (19.4%) of 36 individuals treated for their first ON episode with corticosteroids vs 4 (44.4%) of 9 untreated individuals (P =.19). There was no difference in the conversion rate to MS between those treated with intravenous steroids (4 [16.7%] of 24) vs oral steroids (3 [25.0%] of 12) (P =.33). Conversion to NMO occurred earlier than conversion to MS (2.3 +/- 1.6 vs 5.3 +/- 4.3 years, respectively; P =.01). Women tended to convert to NMO more frequently than men (female-male ratio for NMO converters, 7:1; MS converters, 2:1; nonconverters, 2:1; P =.56), as did those with a higher annual frequency of ON episodes (NMO converters, 2.0 +/- 1.3; MS converters, 1.0 +/- 1.0; nonconverters, 0.6 +/- 0.5; P =.04). The number of ON events in the first 2 years following the first ON episode was higher in the NMO group (NMO converters, 2.4 +/- 0.9; MS converters, 1.9 +/- 1.1; nonconverters, 1.7 +/- 0.7; P =.04). The final visual impairment was greatest in the NMO group (P =.02). CONCLUSIONS Patients with rapid succession of severe ON events are more likely to develop a generalized demyelinating disease. Patients with NMO had a worse visual outcome.