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

Optic neuritis presentations are thought to have a better prognosis. The aim of our study was to compare conversion to multiple sclerosis on the different topographies of CISs. We prospectively evaluated 320 patients with CISs (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 brain MRI within 3 months of their first attack and again 12 months later. Conversion to multiple sclerosis 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% in brainstem syndromes, 24% in spinal cord syndromes, and 18.5% in other syndromes. Optic neuritis behaved differently from the other CISs for lower conversion to clinically definite multiple sclerosis and 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. Optic neuritis has a smaller risk for conversion to multiple sclerosis. Nevertheless, MRI at baseline, not CIS topography, appears to be the crucial issue at multiple sclerosis presentation.