Spinal cord injuries (SCIs) can be classified based on function (how much feeling and movement you have) or on where the damage occurred. When a nerve in the spinal cord is injured, the nerve location and number are often used to describe how much damage there is. For example, a C7 injury is associated with the seventh cervical nerve of the neck and its effect on feeling and movement. Saying you are a C7 communicates that you can feed yourself and partially dress yourself but may need help bathing, and so on. C7 is known as the functional level of injury. These classifications are often used by people who have SCIs to describe themselves.
The spinal cord is surrounded by protective rings of bone called vertebrae. The vertebrae and spinal nerves are organized into segments , starting at the top of the spinal cord. Within each segment, the vertebrae and nerves are numbered. The segments are as follows:
- Cervical. The neck area contains 7 cervical vertebrae (C1 through C7) and 8 cervical nerves (C1 through C8). Cervical SCIs usually cause loss of function in the chest, arms, and legs. Cervical injuries can also affect breathing and bowel and bladder control.
- Thoracic. The chest area contains 12 thoracic vertebrae (T1 through T12) and 12 thoracic nerves (T1 through T12). The first thoracic vertebra, T1, is the vertebra where the top rib attaches to the spine. Thoracic SCIs usually affect the chest and the legs. Injuries to the upper thoracic area can affect breathing. Thoracic injuries can also affect bowel and bladder control.
- Lumbar. The lumbar area (between the chest area and the pelvis) contains 5 lumbar vertebrae (L1 through L5) and 5 lumbar nerves (L1 through L5). Lumbar SCIs usually affect the hips and legs. Lumbar injuries can also affect bowel and bladder control.
- Sacral. The sacral area (from the pelvis to the end of the spine) contains 5 sacral vertebrae (S1 through S5) and 5 sacral nerves (S1 through S5). Sacral SCIs also usually affect the hips and legs. Injuries to the upper sacral area can also affect bowel and bladder control.
The higher the damage occurs on the spinal cord, the more of the body is affected. This is because the nerves in the area of a vertebra control body parts in that area . When the spinal cord is damaged, messages cannot "jump over" the damaged area. This means that messages sent from the brain cannot make it to body parts below the damaged area, and vice versa. Thus, the body at and below the level of injury is affected.
For example, in an injury to the spinal nerves in the neck area (C1 through C8), messages are stopped in the neck area. This usually results in at least some paralysis of the chest, arms, and legs (tetraplegia, also known as quadriplegia). In an L3 injury, messages are stopped at the lower back. This results in at least some paralysis of the legs and hips (paraplegia).
SCIs are also described as complete and incomplete, and an incomplete injury is further classified into four subsections. The American Spinal Injury Association (ASIA) classifies SCIs as follows:
|A||Complete: No feeling or movement of the areas of your body that are controlled by your lowest sacral nerves. This means you do not have feeling around the anus or control of the muscle that closes the anus. People with complete SCI do not have control of bowel and bladder function.|
|B||Incomplete: Feeling but no movement below the level of injury, including sacral segments that control bowel and bladder function.|
|C||Incomplete: Feeling and movement below the level of injury. More than half of key muscles can move, but not against gravity. Moving against gravity means moving up, for example, raising your hand to your mouth when you are sitting up.|
|D||Incomplete: Feeling and movement below the level of injury. More than half of key muscles can move against gravity.|
|E||Feeling and movement are normal.|