Impact of COVID-19 public health measures on myelin oligodendrocyte glycoprotein IgG-associated disorders in children

Introduction: Despite better characterization of the spectrum of MOG IgG-associated disorders (MOGAD) in children, the role of infection in its pathophysiology remains unclear. Objectives: The goal of this study was to evaluate if public health measures put in place to prevent the spread of SARS-CoV-2 in March 2020 in Ontario (Canada) have been associated with a change in the incidence of MOGAD and other neuroinflammatory disorders in children. Methods: We reviewed a single-centre cohort of children referred for a suspicion of neuroinflammatory disorder between 2015-2020. Age, date, sex, diagnosis, MOG IgG antibodies status and detected pathogens at presentation were identified. Comparative statistical analysis was performed between years and seasons using Pearson's Chi-squared test or Fisher's exact test for categorical variables and using ANOVA or Kruskal-Wallis test for continuous variables, as appropriate. Post-hoc pairwise comparisons between 2020 and previous years were performed on significant results. The analyses were repeated twice including either complete data from 2020 (January 1st to December 31st, 2020) or only data acquired after the spring lockdown (March 17th to Dec 31st, 2020). A false discovery rate adjustment with an adjusted p-value (q-value) < 0.05 was computed. It was hypothesized that the number of new MOGAD would be significantly lower in 2020 compared to previous years due to decreased regional pathogen transmission. Results: Among 479 referred cases, we identified 364 confirmed new cases of neuroinflammatory disorder between 2015 and 2020. The number of new neuroinflammatory disorder diagnoses did not change between years. We noted significantly fewer new MOGAD diagnoses in 2020 compared to previous years (q=0.003), with no MOGAD patient presenting in 2020 after the spring lockdown. Parallelly, there were significantly fewer parainfectious neuroinflammatory cases (q=0.038) and pathogen detected (q=0.045) in the post-lockdown period. The number of new multiple sclerosis (MS) and aquaporin-4 neuromyelitis optica spectrum disorders (AQP4-NMOSD) cases remained stable despite the lockdown (q-value=0.237 and 0.505 respectively). Conclusions: Enhanced population-based infection control strategies may have a role in modulating the incidence of MOGAD and parainfectious neuroinflammatory disorders, but not MS or AQP4-NMOSD.