Risk factors for the development of multiple sclerosis in patients with acute optic neuritis

This prospective cohort study was designed to evaluate risk factors in 389 patients with acute optic neuritis for the development of definite multiple sclerosis (MS) within two years.

Exposure variables that were assessed included gender, age, race, randomized corticosteroid treatment assignment, brain MRI signal abnormalities, previous fellow eye optic neuritis, prior ill-defined neurologic symptoms, family history of MS, location of residences up to age 15, viral syndrome preceding optic neuritis, season of onset, fellow eye visual field abnormalities, antinuclear antibody (ANA) blood level, and various clinical features of the optic neuritis.

Outcome was defined as the development within two years of a neurologic event sufficient for a diagnosis of definite MS.

Treatment of the optic neuritis with the regimen of intravenous followed by oral corticosteroids had a marked protective effect, reducing the two-year risk of definite MS by about 2.5 fold compared to placebo (adjusted relative risk 0.36, 95% confidence interval 0.17-0.78). Signal abnormalities on brain MRI were a powerful risk factor with the risk increasing relative to the number of lesions on the scan (adjusted relative risk 5.44, 95% confidence interval 2.38-12.46 in patients with three or more lesions). Previous fellow eye optic neuritis, family history of MS, prior neurologic symptoms, preceding viral syndrome, residence in north prior to age 15, and Caucasian race all were associated with increased risk. Neither age and gender nor any of the other exposure variables were found to be significant risk factors.

From the results of the study high and low risk profiles for the development of MS after optic neuritis can be established. It is apparent that MRI scanning is now a critical part of the evaluation of patients with acute optic neuritis in order to establish this risk and to determine the benefit that can be anticipated from intravenous corticosteroid treatment. Treatment is now indicated for optic neuritis patients with brain MRI signal abnormalities, but this study cannot determine whether patients with a normal scan also will benefit from treatment.