Spinal Cord Injury
Spinal cord injury (SCI) is an insult to the spinal cord resulting in a change in the normal motor, sensory or autonomic function. This change can be temporary or permanent.
Frequent causes of damage include:
- Trauma, such as automobile crashes, falls, gunshots, diving accidents, sports injuries and war injuries
- Tumors, such as meningiomas, ependymomas, astrocytomas and metastatic cancer
- Ischemia, resulting from occlusion of spinal blood vessels, including dissecting aortic aneurysms, emboli arteriosclerosis
- Developmental disorders, such as spina bifida, meningomyolcoele and others
- Neurodegenerative diseases, such as Friedreich’s ataxia and spinocerebellar ataxia
- Demyelinative diseases, such as multiple sclerosis
- Transverse myelitis, resulting from stroke, inflammation or other causes
- Vascular malformations, such as arteriovenous malformation (AVM), dural arteriovenous fistula (AVF), spinal hemangioma, cavernous angioma and aneurysm
Spinal cord injuries are very different from back injuries like ruptured discs, spinal stenosis or pinched nerves. An individual can “break his back or neck” and not sustain an SCI if only the bones around the spinal cord (the vertebrae) are damaged, but the spinal cord is unaffected.
When spinal cord injuries occur, it’s more than just a single event. The initial blunt force damages or kills spinal nerve cells. Hours and days after the injury, a cascade of secondary events, including loss of oxygen and the release of toxic chemicals at the site of injury, may result in further damage to the cord.
Generally speaking, as the swelling of the spinal cord goes down, 66% to 80% of individuals will show return of function at one segment below the initially defined level of function. This is termed “root escape.” It implies that the return of function is typically due to preservation of peripheral nerve roots (versus actual spinal cord recovery) and it can happen within weeks or months after an injury.
Neurons of the peripheral nervous system (PNS), which carry signals to the limbs, torso and other parts of the body, are able to repair themselves after injury. However, nerves in the brain and spinal cord, the central nervous system (CNS), are not able to regenerate.
The spinal cord does not have to be severed in order for a loss of functioning to occur. In fact, in most individuals with spinal cord injury, the spinal cord is intact, but the damage results in loss of function. Since the spinal cord coordinates body movement and sensation, an injured cord loses the ability to send and receive messages from the brain to the body’s systems that control sensory, motor and autonomic function below the level of injury.
The level of injury is very helpful in predicting what parts of the body might be affected by paralysis and loss of function. Cervical (neck) injuries usually result in tetraplegia (commonly referred to as quadriplegia). Tetraplegia is the loss of partial or total function of all four limbs.
Injuries above the C4 level can result in a loss of many involuntary functions, including the ability to breathe, necessitating breathing aids such as mechanical ventilators or diaphragmatic pacemakers. The C5 injuries often result in shoulder and biceps control, but no control at the wrist or hand. The C6 injuries generally yield wrist control, but no hand function. Individuals with C7 and T1 injuries can straighten their arms but still may have dexterity problems with the hand and fingers.
Injuries at the thoracic level and below result in paraplegia, with the hands not affected. Paraplegia is impairment in motor or sensory function of the lower extremities. If only one limb is affected, the correct term is monoplegia. At T1 to T8, there’s most often control of the hands, but poor trunk control as the result of lack of abdominal muscle control. Lower T injuries (T9 to T12) allow good trunk control and good abdominal muscle control. Sitting balance is typically very good. Lumbar and sacral injuries yield decreasing control of the hip flexors and legs.
Besides a loss of sensation or motor functioning, individuals with SCI also experience other changes. They may experience bladder, bowel and sexual dysfunction. Other effects of SCI may include low blood pressure, inability to regulate blood pressure effectively, reduced control of body temperature, inability to sweat below the level of injury and chronic pain.