Spinal cord injury is devastating to the victim, as well as being costly in terms of medical expenses, lost wages, and lost independence. The initial damage to the spinal cord results from several mechanisms of injury--flexion, extension, compression, penetration, rotation, and the disease process. When the spinal cord is injured and there is necrosis of the nervous tissue, no regeneration of that tissue occurs. Unlike in the peripheral nervous system, where regeneration is possible, the spinal cord is part of the central nervous system, as is the brain. The spinal cord extends from the base of the skull to the L1 vertebrae: the cervical levels innervate the diaphragm and muscles of the arms; the thoracic levels innervate the muscles of the chest and abdomen; and the lumbar and sacral levels innervate the muscles of the legs. In addition, the sacral levels are responsible for bowel, bladder, and sexual function. The higher the level of injury, the more severe the loss of function because, not only is the level of injury affected, but also the levels below. Injury occurs by initial trauma to the surrounding ligaments, bones, and muscles, which then affect the spinal cord. There may be total loss of function with damage completely across the cord or partial loss of function with damage affecting only part of the cord. No current treatment can reverse this initial injury, which causes irreversible damage within minutes of injury. Secondary damage occurs as the injury spreads over several hours. Treatment can help prevent this secondary damage.