What and Why? Spinal injury and spinal cord injury result when the body is exposed to forces greater than its parts can withstand. Force in amounts that can cause such damage result from auto crashes, falls from heights, falls, crashes and blows associated with sport and recreation, contact with an unmovable object or surface when diving or, from penetration by gunshot or sharp objects. Spinal Injury Sometimes only the bony structures and/or ligaments are damaged, resulting in various kinds of fractures (broken bones and discs or dislocations) and an unstable spine. Though the area affected will probably need to be immobilized until healing results, the spinal cord is not affected. Spinal Cord Injury When the injury involves the spinal cord, the flow of messages between the brain and the rest of the body is interrupted or broken. The interruption results in a decrease or loss in motor function (movement) or sensation (feeling) – or both – below the level of injury, and will also affect bowel, bladder and sexual function. The Spine and Spinal Cord The Spine The spine or backbone gives the body stability and protects the spinal cord. It is a flexible column made up of 33 vertebrae (spinal bones). Through the centre of this column is a narrow canal where the spinal cord is located. The column is made flexible by the discs (spongy shock absorbers) located between each vertebra, and the ligaments made of tough elastic fibers, which hold the vertebrae together. The Vertebrae are separated into groups: o 7 cervical (neck) C1-C7 o 12 thoracic (chest) T1-T12 o 5 lumbar (lower back) L1-L5 o 5 sacral S1-S5 fused o 4 coccyx (tailbone) fused The Vertebral Body The shape of each vertebra (bone) that makes up the column varies slightly depending on its location. In general, each vertebra is composed of a body and an arch from which several fingers of bone (processes) extend. The Spinal Cord The spinal cord, located within the spinal canal, is a delicate tube of nerve cells and nerve fibers that extends from the brain to the lower back. It then branches into a sheaf of nerves called the cauda equine, or horse's tail, which extends to the coccyx. The spinal cord is composed of 31 functional segments, with a pair of spinal nerves attached at each segment. The cord is encased in a tough fibrous membrane (dura mater) and is bathed in a fluid (cerebral-spinal fluid) which provides further protection. Several arteries supply the cord with blood. Together, the brain and the spinal cord make up the central nervous system. The function of the spinal cord is to relay messages (nerve impulses) from the brain to the body and from the body to the brain. All movements of the body and limbs, and all sensation, are relayed through the spinal cord. Injury to the cord results in an interruption in the ability to relay these messages. Within the cord, nerve fibres are arranged in bundles or tracks, each of which controls a different function (motor or sensory functions). A number of important reflexes such as bladder and bowel control, sexual function and tendon reflexes are controlled through the spinal cord as well. Motor messages, carried on motor nerves, involve voluntary movement, such as moving an arm or a leg. Sensory messages, carried on sensory nerves, indicate temperature, pain, touch and vibration. The spinal cord also plays a part in the transmission of messages from the autonomic nervous system. The spinal nerves, which attach to the cord at the nerve roots, provide pathways for the involuntary functions (meaning without your conscious control) of the autonomic nervous system. The autonomic nervous system has two divisions, the sympathetic and the parasympathetic. Together, they regulate many of the body functions that we are mostly unaware of - for example, heart beat, maintenance of blood pressure, muscle tone, temperature regulation, bladder emptying, sexual functioning. An imbalance of the divisions of the autonomic nervous system, which happens with some spinal cord injuries, can disturb circulation, blood pressure control and bowel, bladder and sexual function. Complete and Incomplete Injuries Injuries to the spinal cord are called complete or incomplete to describe the degree of interruption in the transmission of messages. A complete injury means that there is no transmission (delivery) of messages beyond the level of injury, resulting in no sensation and no voluntary movement below this area. A complete injury also implies that there is no voluntary contraction of the anal sphincter and absent sensation around the anus (the opening to the rectum). An incomplete injury indicates that some messages are being transmitted. Depending on the location and kind of injury, the interrupted messages may be either motor or sensory or, a combination of both. When the injury is incomplete, the pattern of interruption varies greatly from person to person. The cord can be damaged by forces such as cutting, crushing, squeezing, bruising, or by the effects of swelling or a decrease in blood supply. The level at which the injury occurs will be a clue to the after-effects or permanent deficits (loss of function). The higher up the cord, the greater the loss of function. Based on spinal nerve distribution, a general picture of the effects of injury at specific levels of the cord can be made. Quadriplegia / Tetraplegia The nerves that supply feeling and movement to the arms and hands, as well as the nerves of the diaphragm, come from the nerve roots in the cervical spinal cord. If the cord is injured in this region, movement and sensation may be interrupted to arms and hands as well as the rest of the body (including muscles in the abdomen, chest and legs, as well as bladder, bowel and sexual function). If the injury is high enough that the diaphragm is affected, breathing problems will also occur. Thus, quadriplegia is a condition that causes paralysis of both the upper and lower limbs. Paraplegia An injury to the cord in the thoracic or lumbar spine may affect the legs and trunk (abdomen and lower back) as well as bladder, bowel and sexual function, but arms and hands are unaffected. For more information, visit the Canadian Spinal Research Organizationwww.csro.com