Acute disseminated encephalomyelitis in China, Singapore and Japan: a comparison with the USA

Background and purpose Ethnicity‐related differences in the incidence of acute disseminated encephalomyelitis (ADEM) and other demyelinating diseases including multiple sclerosis and neuromyelitis optica spectrum disorders have been reported. Little is reported on the influence of ethnicity and geographical location in ADEM. Methods Medical records of patients who presented with ADEM (ICD‐9 323.61 and 323.81) at large referral hospitals in China, Singapore and Japan (years 1992–2015) were retrospectively reviewed and data were collected in a centralized database. Presenting features and outcomes of ADEM were compared between this multi‐country Asian cohort and a uniformly collected US cohort using risk differences and risk ratios. Both cohorts were standardized to a 35% pediatric population to facilitate the comparison. Results There were 83 Asian patients (48 male, 16 pediatric) followed for a median of 2 (25th–75th percentile 1–10) months. Asian patients exhibited a 26% higher prevalence of spinal cord involvement on magnetic resonance imaging [95% confidence interval (CI) 0–52%; P = 0.05; 63% vs. 37%], a 39% lower prevalence of preceding events (95% CI 12–65%; P < 0.01; 33% vs. 72%) and a 23% lower prevalence of corpus callosum involvement (95% CI 7–39%; P < 0.01; 8% vs. 31%). No difference was observed between the two cohorts in the probability of relapse over the first year after disease onset. Conclusions It is hypothesized that the high proportion of Asian patients with spinal cord lesions relates to genetic vulnerability or the higher incidence of neuromyelitis optica spectrum disorders in Asia or could be a spurious association. ADEM presentations most probably vary across geographical settings or ethnicities.