is a neurological disorder caused by inflammation across both sides of one level, or segment, of the spinal cord. The term myelitis refers to inflammation of the spinal cord; transverse describes the position of the inflammation, that is, across the width of the spinal cord. Attacks of inflammation can damage or destroy myelin, the fatty insulating substance that covers nerve cell fibers. This damage causes nervous system scars that interrupt communications between the nerves in the spinal cord and the rest of the body. Transverse myelitis is part of a spectrum of neuroimmunologic diseases of the central nervous system. Other disorders in this spectrum include, Acute Disseminated Encephalomyelitis (ADEM), Optic Neuritis, and Neuromyelitis Optica (Devic's disease). Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.