The Facts about Spinal Cord Injury

The spinal cord is the major bundle of nerves that carry nerve impulses to and from the brain to the rest of the body. These nerve impulses are the starting place for all our movements – the ones we have to think about (like walking or touching) and the ones that happen automatically (like breathing). The brain and the spinal cord make up the Central Nervous System. Motor and sensory nerves outside the central nervous system make up the Peripheral Nervous System; other systems that control involuntary functions (like blood pressure and temperature) are called the Sympathetic and Parasympathetic Nervous Systems.

Spinal Cord Injury (SCI) damages the spinal cord and results in loss of functions such as mobility or feeling. Frequent causes of damage are trauma (car accident, gunshot, falls, etc.) or disease (polio, spina bifida, etc.). The spinal cord does not have to be completely severed in order for a loss of function to occur. In fact, most people with SCI still have an intact, but damaged, spinal cord.

Severe SCI often causes paralysis (loss of control over voluntary movement and muscles of the body) and loss of sensation and reflexes below the point of injury, including autonomic activities such as breathing and other activities such as bowel and bladder control. Other symptoms such as pain or sensitivity to stimuli, muscle spasms, and sexual dysfunction might also occur. SCI patients are also prone to developing secondary medical problems including bladder infections, lung infections, and bedsores.

Outcome Depends on Location and Type of Injury
When an SCI occurs the spinal cord usually swells. This can cause changes in virtually every system in the body. After days or weeks, the swelling begins to go down and people might regain varied levels of body function. With many injuries, especially incomplete injuries, the injured person may continue to recover some functioning for many months. In very rare cases, people with SCI will regain some functioning years after the injury. However, only a very small fraction of individuals sustaining SCIs recover all functioning.

The effects of SCI depend on the type of injury and the location at which it occurs on the spine. SCIs can be divided into two types – complete and incomplete. A complete injury means that there is no function below the level of the injury; no sensation and no voluntary movement. Both sides of the body are equally affected. An incomplete injury means that there is some functioning below the primary level of the injury. A person with an incomplete injury may be able to move one limb more than another, may be able to feel parts of the body that cannot be moved, or may have more functioning on one side of the body than the other.

Besides a loss of sensation or motor functioning, individuals with SCI also experience other changes. For example, they may have bowel and/or bladder dysfunction. Sexual functioning is frequently disrupted or lost with SCI. Men may have their fertility affected, while women's fertility often is not. Injuries that occur very high on the spine can result in a loss of many involuntary functions, including the ability to breathe. People with these injuries will need breathing aids such as mechanical ventilators. Other effects of SCI may include low blood pressure, inability to regulate blood pressure effectively, reduced control of body temperature, inability to sweat, and chronic pain. Although these might not sound like serious side effects, extreme variations in blood pressure or body temperature can, in fact, be fatal.

Anatomy and Loss of Function
The spinal cord is surrounded by rings of bone called vertebrae. People can "break their back” or “break their neck" but still not sustain a spinal cord injury if only the bones around the vertebrae are damaged. The level of injury is very helpful in predicting what parts of the body might be affected by paralysis and loss of function. In general, the higher in the spinal column the injury occurs, the more dysfunction a person will experience. The vertebrae are named according to their location:

• The seven vertebrae in the neck are called the cervical vertebrae. The top vertebra is called C-1, the next one down is C-2, and the numbers continue to C-7. Injuries to the highest cervical vertebrae usually result in quadriplegia, in which both arms, both legs, and often the trunk are paralyzed. Injuries above the C-4 level may require a ventilator for the person to breathe; bowel and bladder function are lost. High C-level injuries usually require that the individual use a power wheelchair. Injuries that affect the lower cervical vertebrae might leave some head, neck, shoulder, arm or hand control. Bowel and bladder elimination are not automatic and people with these injuries will need varying levels of assistance to achieve elimination. Low C-level injuries and below usually allow the person to use a manual wheelchair.

• Moving down the spine, the next twelve vertebrae – those in the chest – are called the thoracic vertebrae. The first thoracic vertebra, T-1, is the vertebra where the top rib attaches. Injuries in the thoracic region (T-1 through T-12) usually affect the chest and the legs and result in paraplegia. Individuals with C-7 and T-1 injuries can straighten their arms but still may have dexterity problems with the hand and fingers. At T-1 to T-8 there is most often control of the hands, but poor trunk control as the result of lack of abdominal muscle control. Lower T-injuries (T-9 to T-12) allow good trunk control and good abdominal muscle control. Sitting balance is very good, and these individuals can typically perform their own procedures to achieve bowel and bladder elimination.

• The vertebrae in the lower back between the thoracic vertebrae, where the ribs attach, and the pelvis (hip bone), are the lumbar vertebrae (L-1 thru L-5). The lowest vertebrae, the sacral vertebrae, run from the pelvis to the end of the spinal column (S-1 thru S-5). Injuries to the five lumbar vertebrae and/or to the five sacral vertebrae generally result in loss of functioning in the hips and legs. Depending on the level and type of injury, bowel, bladder and sexual functions might be partially or even fully intact.

Statistics Grim, but Researchers Making Progress
Before World War II, most people who sustained SCI died within weeks of their injury due to urinary dysfunctions, respiratory infections or bedsores. With the advent of modern antibiotics, materials such as plastics and latex, and better procedures for dealing with the everyday issues of living with SCI, many people approach the lifespan of non-disabled individuals. Interestingly, other than level of injury, the type of rehab facility used is the greatest indicator of long-term survival. This illustrates the importance of and the difference made by going to a facility that specializes in SCI. People who use vents are at some increased danger of dying from pneumonia or respiratory infection, but modern technology is improving in that area as well. Pressure sores are another common cause of hospitalization, and can be fatal if not treated.

Overall, 85% of SCI patients who survive the first 24 hours are still alive 10 years later. The most common cause of death is due to diseases of the respiratory system, with most of these being due to pneumonia. In fact, pneumonia is the single leading cause of death throughout the entire 15-year period immediately following SCI. The second leading cause of death is heart disease; these are almost always unexplained heart attacks that often occur among young people with no previous history of underlying heart disease.

Deaths from external causes is the third leading cause of death for SCI patients. These include subsequent unintentional injuries, suicides and homicides, but do not include persons dying from multiple injuries sustained during the original accident. The majority of these deaths are the result of suicide.

About 450,000 people in the US live with SCI. There are about 10,000 new SCIs every year; the majority of them (82%) involve young males between the ages of 16 and 30. Most of these injuries result from motor vehicle accidents (36%), violence (28.9%) or falls (21.2%).

Although there is no cure for SCI, researchers have made many advances in treatment, including some that could result in a decreased amount of damage at the time of the injury. Steroid drugs such as methylprednisolone reduce swelling, which is a common cause of secondary damage. Certain experimental drugs, although not completely understood, appear to reduce the loss of function.

This article includes information from the National Institute of Neurological Disorders and Stroke.

For more information, see the HealthLink article Spinal Cord Injuries – and Treatment – Can Change Lives.