Acute idiopathic optic neuritis: not always benign

Background and purpose: Few recent data are available concerning idiopathic optic neuritis (ON). We aimed to describe a large cohort of patients with idiopathic ON. We compared this cohort with patients with ON related to myelin oligodendrocyte glycoprotein (MOG) or ON related to aquaporin-4 (AQP4) antibodies.

Methods: This was a monocentric retrospective observational study. Inclusion criteria for idiopathic ON were as follows: age ≥ 16 years, follow-up of at least 2 years, negative for antibodies against MOG and AQP4 immunoglobulin G, and no magnetic resonance imaging (MRI) lesions suggestive of demyelination (two brain MRI scans, one at baseline and one during follow-up, and one spinal cord MRI scan).

Results: Among 23 patients with idiopathic ON (female, 82.6%; median age, 36 years; median follow-up time, 41.4 months), 56.5% had recurrent ON (median time to a second ON episode, 6 months). The final visual acuity in this group (median, 0; mean, 0.43; range, 0-3) was similar to that in the AQP4 group (n = 18; P-value after Bonferroni correction = 0.936) but worse than that in the MOG group (n = 25; P-value after Bonferroni correction = 0.019). At the last evaluation, visual acuity levels were ≤0.5 and <0.2, respectively, in 36.8% and 21% of the idiopathic ON group, 58.3% and 26.7% of the AQP4 group, and 0% and 0% of the MOG group.

Conclusion: The recovery of visual acuity among patients with idiopathic ON was poor, similar to that observed in the AQP4 group.