Background: An important controversy on the development of multiple sclerosis (MS) after an isolated episode of optic neuritis (ON) exists. Magnetic resonance imaging (MRI) is the method of election in order to detect demyelinated lesions in MS. The current study was designed to determine the prevalence of brain abnormalities on MRI and to asses the further development of MS after an isolated idiopathic ON in our population.
Patients and methods: From 1991 to 1995, 60 patients with decrease of visual acuity were studied, 35 (28 women, half age 31 +/- 10 years) completed criteria of idiopathic ON. A brain MRI was performed in all patients after the diagnosis of idiopathic ON and they subsequently were followed in the outpatient clinic from our center for a mean time of 29 +/- 16 months. 24 out of the 35 patients were treated with corticosteroids in different ways.
Results: It has been found 43% of the patients with idiopathic ON to have brain lesions by MRI. During the follow-up 14% of the patients developed a clinically definite MS; all of them had a pathological brain MRI at the basal evaluation (p = 0.009). None of the patients that were treated with high-dose of intravenously corticosteroids developed MS.
Conclusions: The prevalence of silent cerebral lesions in the MRI after an idiopathic ON is elevated in our population although further development of MS is lower possibly due to the short follow-up carried out. The presence of lesions in the MRI confers a high risk for developing MS after an idiopathic ON.