Frequency of AQP4 and MOG Antibodies in Patients With Optic Neuritis Fulfilling Minimal New Multiple Sclerosis MRI Criteria.

OBJECTIVES: Recent revisions to multiple sclerosis (MS) diagnostic criteria include the optic nerve as a site of dissemination in space, enabling this diagnosis in patients with acute optic neuritis (ON) and a single additional MS-typical location on MRI if dissemination in time (DIT) is demonstrated. We aimed to assess the frequency of non-MS diagnoses in this context. METHODS: We retrospectively analyzed consecutive patients with inaugural acute ON and at least 1 MS-typical lesion in a single brain location on baseline MRI across 3 French centers. All patients met DIT criteria and underwent aquaporin-4 (AQP4) and myelin oligodendrocyte glycoprotein (MOG) antibody testing. Final diagnoses were based on clinical, radiologic, and follow-up data. RESULTS: Among 96 patients (mean age 35.8 years; 70.8% female), 73 (76.0%) were diagnosed with MS and 23 (24.0%) with MOG antibody-associated disease (n = 18) or neuromyelitis optica spectrum disorder. Longitudinally extensive lesions, bilateral involvement, chiasmal enhancement, or optic perineuritis were observed in 100% of non-MS patients and 24.6% of patients with MS (difference 75.4%, 95% CI: 64.3-86.6; p < 0.001). All patients without these patterns were ultimately diagnosed with MS. DISCUSSION: AQP4 and MOG antibody testing, along with careful orbital MRI interpretation, is recommended in patients with ON meeting minimal new MS criteria.