Distinguishing Optic Neuritis in Neuromyelitis Optica Spectrum Disease From Multiple Sclerosis: A Novel Magnetic Resonance Imaging Scoring System

BACKGROUND:The management of acute optic neuritis differs according to the underlying etiology and techniques which may help with early differential diagnosis are therefore of considerable value. OBJECTIVE:We wanted to determine if multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) could be differentiated on the basis of neuroimaging abnormalities of the anterior visual pathways following an episode of optic neuritis. METHODS:Magnetic resonance imaging (MRI) findings of 27 patients diagnosed with MS (n = 15) or NMOSD (n = 12), who presented with acute isolated optic neuritis over a 3-year period, were reviewed retrospectively. The extent and location of inflammation along the anterior visual pathways were analyzed. A novel scoring system was devised, based upon the number of anatomical segments involved. RESULTS:Patients with NMOSD had a relative risk of 7.5 (confidence interval0.3–17.3) of having a score of 4 or more. Only NMOSD patients were found to have a score of 6 or higher. A trend for more posterior involvement of the anterior visual pathways was noted in the NMOSD group. CONCLUSION:This pilot study suggests that the MRI-based scoring system described here may aid in distinguishing patients with optic neuritis who have MS vs NMOSD. Visual pathway inflammation in NMOSD patients appears to be more extensive than in MS, mirroring the longitudinally extensive spinal cord lesions found in neuromyelitis optica.