As the term implies, SCIs occur when the spinal cord sustains damage in some form or fashion. The spinal cord is not actually a cord, per se. It comprises a bundle of nerves inside the spinal column, which consists of bones (vertebrae) and discs.
An SCI can result from a direct blow to the bony spinal column, or from trauma to the nerves, soft tissue, or blood vessels surrounding the spinal cord. One common feature of most spinal cord injuries consists of interruption of the signals the cord transmits from the brain to the body. The severity of the injury and the location of the injury on the cord determines the extent of that interruption.