The Distribution and Demographics of Optic Neuritis Subtypes in Alberta

Authors: Etienne Benard-Seguin, Abdullah Al-Ani, Fiona Costello.

Author Disclosure Block: A. Al-Ani: Funded grants or clinical trials; Name of for-profit or not-for-profit organization(s); Fighting Blindness Canada, Neuro Nexus. E. Benard-Seguin: Funded grants or clinical trials; Name of for-profit or not-for-profit organization(s); Fighting Blindness Canada, Neuro Nexus, North American Neuro- Ophthalmology Society. F. Costello: Funded grants or clinical trials; Name of for-profit or not-for-profit organization(s); Neuro Nexus, North American Neuro-Ophthalmology Society.

Purpose: Optic neuritis (ON) is a complex clinical syndrome often associated with central nervous system demyelination disorders. While ON may be sporadic in nature or encountered in the setting of multiple sclerosis (MS), the discovery of two biomarkers, myelin oligodendrocyte glycoprotein (MOG)-IgG and aquaporin-4-immunoglobulin G (AQP-IgG), has enabled clinicians to diagnose other subtypes. Herein, we evaluate the distribution and clinical presentation of various ON subtypes within a Canadian population. 

Study Design: A retrospective study of patients referred for neuro-ophthalmic consultation in Calgary, Alberta from 2008-2020. Methods: Through a detailed chart review of each patient, the following variables were collected: demographics (sex, age, and ethnicity); symptoms on presentation; and most responsible etiology/diagnosis. Final diagnosis was reviewed for all patients. Patients were excluded if a final diagnosis of ON was not established or if a final diagnosis was not recorded. 

Results: Our analysis has identified 468 ON cases. Of these patients, 253 (55%) were diagnosed with MS, 94 (20%) were diagnosed with a Clinically Isolated Syndrome (CIS), and 121 (25%) were diagnosed with another ON subtype [18 (4%) were diagnosed with Myelin oligodendrocyte glycoprotein IgG associated disease (MOGAD), 15 (3%) with Neuromyelitis Optica Spectrum Disorder (NMOSD), 10 (2%) with cryptogenic ON, 5 (1%) with CRION], 4 (1%) with sarcoid, 4 (1%) with systemic lupus erythematosus, 4 (1%) with syphilis, 4 (1%) with neuroretinits and 4 (1%) with perineuritis]. Further examination of the data revealed that 67% of MOGAD and 75% of NMOSD patients were females with an average age of 34.4 and 31.2 years at presentation, respectively. Additionally, 11 (65%) of MOGAD and 10 (67%) NMOSD patients presented with ocular pain, while 5 (28%) and 6 (40%) presented with bilateral ocular pain, respectively. 

Conclusions: To the best of our knowledge, this is the first Canadian study that describes the distribution of the various ON subtypes. This data establishes statistical evidence to inform clinical practice and prioritize investigations in the workup of ON.