Transverse myelitis is an inflammation of the spinal cord that affects one or more spinal cord levels completely or almost completely.

When the lesion is located in the cervical cord, symptoms occur in all four extremities.

When the lesion is located in the dorsal medulla, only the lower extremities are affected.

Transverse myelitis may occur spontaneously (idiopathic forms), after an infectious condition (post-infectious forms) or in association with other neurological or general diseases (e.g. multiple sclerosis, neuromyelitis optica, lupus erythematosus).