MOG and neuromyelitis optica: A combination of the following search terms was used: “neuromyelitis optica,” “NMO,” “NMOSD,” “aquaporin 4,” “AQP4,” “myelin oligodendrocyte glycoprotein,” “MOG,” “optico-spinal multiple sclerosis,” “OSMS,” “idiopathic inflammatory demyelinating disease,” “IIDD,” “epidemiology,” “prevalence,” “population,” and “demographic.” The reference lists in published articles on NMOSD were also queried to identify further studies.