Is optic neuritis more benign than other first attacks in multiple sclerosis?

Multiple sclerosis (MS) often presents with isolated optic neuritis; indeed, a number of patients with isolated optic neuritis eventually develop definite MS. Natural history studies have suggested that such forms of MS may have a better prognosis than those presenting with brainstem syndromes or myelitis. The goal of this study was to compare the rate of conversion with definite MS based on the first clinical presentation (isolated optic neuritis, brainstem syndrome, or myelitis). The authors prospectively evaluated 320 patients with a clinically isolated syndrome (123 with optic neuritis, 78 with brainstem syndromes, 89 with spinal cord syndromes, and 30 with other topographies) who were observed for a median of 39 months. Patients underwent a brain MRI within 3 months of their first attack and again 12 months later. Conversion to MS, determined either clinically or by MRI, was evaluated according to topography. Baseline MRI was normal in 49.2% of patients with optic neuritis compared with 24% of patients with brainstem syndromes, 24% of patients with spinal cord syndromes, and 18.5% of patients with other syndromes. Optic neuritis patients had a lower conversion to clinically definite MS and a smaller proportion of patients fulfilling MRI dissemination in space, time, or both. Nevertheless, when only patients with abnormal cranial MRI results at baseline were selected, no differences for clinical or MRI conversion were found. The authors conclude that even though optic neuritis patients have a smaller risk for conversion to MS, it is the MRI at baseline, not the clinical presentation, which determines the subsequent risk of definite MS. —Valerie Biousse