Neuromyelitis Optica (NMO) is an inflammatory demyelinating disease of the central nervous system (CNS) that primarily involves the optic nerve and spinal cord. NMO has long been considered a subtype of multiple sclerosis (MS), but evidence suggests that it has many clinical and pathological manifestations distinct from MS, and in 2006 was recognized as a separate disease unit and the first CNS autoimmune ion channelopathy. Unlike in Western countries, optic neuromyelitis optica is more common than MS in East Asian countries such as China and Korea and Japan, and early diagnosis can directly change the management and prognosis of the disease.