Diagnosis and classification of neuromyelitis optica (Devic's syndrome).

Neuromyelitis optica (NMO) is an autoimmune disorder, predominantly characterized by severe optic neuritis (ON) and transverse myelitis (TM). Historically considered a variant of Multiple sclerosis, the discovery that most NMO patients have autoantibodies against aquaporin-4 (AQP4) or NMO-IgG, dramatically changed our understanding of the disease. The finding of NMO-IgG revealed wider array of clinical presentations, including patients with recurrent ON of TM alone, now considered part of the NMO spectrum. Furthermore, symptoms other than optic-spinal involvement and the presence of brain lesions, do not exclude the diagnosis of NMO as traditionally accepted. We present an overview of the epidemiology, clinical manifestations and current diagnostic criteria for NMO and NMO spectrum disorders.