Differences in clinical features between optic neuritis in neuromyelitis optica spectrum disorders and in multiple sclerosis

Background: Optic neuritis (ON) is one of the common manifestations both in neuromyelitis-optica spectrum disorders (NMOSD) and in multiple sclerosis (MS). Objectives: The objective of this paper is to compare clinical presentations, laboratories and imaging findings in ON associated with MS and NMOSD. Methods: A retrospective chart review was performed in patients presenting with ON in 59 NMOSD patients with 72 eyes’ involvement and 163 ON attacks, and 20 MS patients with 23 eyes’ involvement and 36 ON attacks. Results: ON-NMOSD patients had recurrent ON more often and tended to have simultaneous bilateral ON involvement at their first ON attack. Individuals with ON-NMOSD revealed worse visual acuity at first ON attacks and also had poorer long-term visual outcome than those with ON-MS, with nearly half of ON-NMOSD patients still having LogMAR visual acuity 1 at their last follow-up (p ¼ 0.035). Significant thinner average retinal nerve fiber layer thickness was found in the ON-NMOSD group. We found no significant differences in segmentation location of the optic nerve lesions and the length of involvement between the two groups. Conclusions: It was difficult to completely differentiate ON-NMOSD from ON-MS. ON-NMOSD patients, however, tended to have simultaneous bilateral ON involvement and poorer long-term visual outcome than individuals with ON-MS.