Low conversion rate to multiple sclerosis in idiopathic optic neuritis patients in Taiwan

To investigate the clinical characteristics of patients with idiopathic optic neuritis (ON) in Taiwan and to assess the conversion rate to multiple sclerosis (MS) in these patients.

We studied the medical records of a total of 109 patients with a clinical diagnosis of idiopathic ON treated in the Taipei Veterans General Hospital during the period from January 1986 to May 2003. Clinical characteristics, management, and disease courses were retrospectively reviewed. Our main focus was on the development of multiple sclerosis after an ON attack. Univariate and multivariate analyses were used to evaluate the risk indicators for MS conversion.

The patients (58 women, 51 men) had a mean age of 41.2 years at onset. ON was retrobulbar in 46.8% of the patients. Management with or without pulse therapy did not affect the final visual outcome. Female sex, retrobulbar type ON, recurrent cases, elevated cerebrospinal fluid (CSF) IgG index, and central nervous system (CNS) imaging abnormalities were identified as risk indicators for the development of MS (P < 0.05). The 2-year cumulative probability of developing MS was 5.92%, and the 5-year cumulative probability was 14.28%. The conversion rate to MS did not differ among treatment groups.

Idiopathic ON patients in Taiwan have an older age at onset and a higher percentage of optic disc edema than reported in previous literature. The characteristic features of ON patients associated with a high risk of developing MS are female sex, retrobulbar type ON, CNS imaging abnormalities, elevated CSF IgG index, and recurrence. Idiopathic ON patients in Taiwan display a significantly lower conversion rate to MS.