Spinal cord injury levels, (SCI), ASIA impairment scale; Anatomy related to spinal cord injuries.
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The spinal cord, enclosed in the spinal column, functions as a communication gateway between the brain and the trunk and limbs. It does so by way of spinal nerves, which send sensory information from all over the body to the brain, and convey central instructions from the brain to body muscles and organs.
There are 31 pairs of spinal nerves, each arise from a segment of the cord and innervate a particular part of the body. They are named after the vertebra from which they emerge. Accordingly, there are 8 pairs of cervical nerves, from C1 to C8; 12 pairs of thoracic nerves, T1 to T12; 5 pairs of lumbar nerves, L1 to L5, 5 pairs of sacral nerves, S1 to S5 and 1 pair of coccygeal nerves.
Spinal cord injury is most commonly caused by trauma to the spinal cord, but there are also non-traumatic causes. As injury occurs, spinal nerves are damaged, and the communication between the brain and the body is blocked. Because spinal nerves are responsible for both sensory and motor functions, spinal cord injury may cause loss of both sensation and muscle control. The latter not only leads to paralysis, but also dysfunction in processes such as urine voiding, bowel movement, breathing, and speaking. The higher the injury occurs on the cord, the more nerves are affected, the more extensive the disability.
At the lowest levels, injuries may result in some loss of function in the hips and legs; little or no control of bowel or bladder, and impaired sexual functions, but the patient may still be able to walk. At lumbar levels, the chance of walking recovery is greatly reduced. Patients will typically require manual wheelchair or walking braces. Thoracic injury additionally affects abdominal, chest and back muscles.
Patients with low-cervical injury may also suffer, on top of all that, from loss of control of arms and hands, at various degrees. High-cervical injury usually results in total paralysis from the neck down. In addition, patients may not be able to breathe on their own; their ability to speak is also reduced.
There are two broad types of spinal cord injury, each consisting of several levels:
- Tetraplegia, formerly termed quadriplegia, is loss of sensory and/or motor functions from the neck down, including paralysis of both arms and legs.
- and paraplegia is when there is disability in the trunk and both legs, but not the arms.
Spinal cord injuries are also classified by degrees of severity:
- Complete injury is when all sensory and motor functions below the injured level are lost.
- and incomplete injury is when some functions below the injured level remain. There are several grades of incomplete injury which can be assessed using the impairment scale by the American Spinal Injury Association.
Damage to the spinal cord cannot be reversed, but emergency and early treatments can help prevent further damage and minimize the severity. People with mild injuries at lower levels may partially recover with rehabilitation. Modern equipment and devices can help patients manage daily activities and return to a productive life.