Progression of optic neuritis to multiple sclerosis: a prospective study in an Italian population.

We prospectively studied 40 patients with uncomplicated optic neuritis (ON) to determine the risk of subsequent multiple sclerosis (MS). All patients were followed for at least 12 years. Ten patients (25%) developed MS. Seven of these 10 patients developed MS within 2 years. Both sexes were at high risk if ON occurred between the ages of 21 and 40. There was an overall increased risk of MS with recurrent ON. The course of MS appeared to be fairly benign during the period of observation.