Long-term brain magnetic resonance imaging changes after optic neuritis in patients without clinically definite multiple sclerosis.

BACKGROUND: Long-term follow-up of the Optic Neuritis Treatment Trial (ONTT) cohort to evaluate brain magnetic resonance imaging (MRI) in patients who have not developed clinically definite multiple sclerosis.

OBJECTIVE: To determine the proportion of patients with monosymptomatic optic neuritis who manifest new brain MRI lesions without having developed clinically definite multiple sclerosis 10 to 14 years after enrollment in the ONTT.

DESIGN: Observational study.

SETTING: Fourteen clinical centers.

PARTICIPANTS: One hundred eight ONTT patients who had not developed clinically definite multiple sclerosis 10 to 14 years after study enrollment.

MAIN OUTCOME MEASURE: Development of new T2 lesions on follow-up brain MRI.

RESULTS: At least 1 T2 lesion 3 mm or larger was observed on follow-up MRIs in 27 (44%) of 61 patients with normal baseline MRIs. Additional lesions (> or =3 mm) were present on follow-up MRIs in 26 (74%) of 35 patients with abnormal baseline MRIs.

CONCLUSIONS: A subset of patients with monosymptomatic optic neuritis manifest neither clinical signs nor MRI evidence of demyelination after more than 10 years of follow-up. In other cases followed up for this length of time, MRI signal abnormalities may accumulate without causing new clinical manifestations of multiple sclerosis. This information is useful in counseling patients who develop first-episode optic neuritis.