Encephalomyelitis is a general term for inflammation of the brain and spinal cord, describing a number of disorders:
acute disseminated encephalomyelitis or postinfectious encephalomyelitis, a demyelinating disease of the brain and spinal cord, possibly triggered by vaccination or viral infection;
myalgic encephalomyelitis, a syndrome involving inflammation of the central nervous system with symptoms of muscle pain and fatigue; the term has sometimes been used interchangeably with chronic fatigue syndrome, though there is still controversy over the distinction.