Encephalomyelitis: Inflammation of both the brain and the spinal cord. Encephalomyelitis can
be caused by a variety of conditions, including viruses that infect the nervous system. One type
of encephalomyelitis, acute disseminatedencephalomyelitis, occurs most commonly after an acute viral infection, such as measles (rubeola). It is due to an autoimmune attack on the nervous system, meaning that the immune system mistakenly attacks body tissue that it believes to be the measles virus. Also known as myeloencephalitis.
