Spinal Cord Injury Health Article

Definition

Spinal cord injury is damage to the spinal cord that causes loss of sensation and motor control.

Description

Approximately 11,000 new spinal cord injuries (SCIs) occur each year in the United States. About 200,000 people are currently affected. Spinal cord injuries can happen to anyone at any time of life. The typical patient, however, is a man between the ages of 19 and 26, injured in a motor vehicle accident (about 35% of all SCIs), a fall (20%), an act of violence (15%), most often related to firearms use, or a sporting accident (14%). According to the Centers for Disease Control, violence-related SCIs have been steadily increasing since 1980, and in 2001, violence is associated with 30% of all SCI cases.

Most SCI patients are white, but the nonwhite fraction of SCI patients is larger than the nonwhite fraction of the general population. In fact, the SCI rate among blacks, who are at higher risk for SCI than whites, has been rising in recent years. Alcohol or other drug abuse plays an important role in a large percentage of all spinal cord injuries. Six percent of people who receive injuries to the lumbar spine die within a year, and 40% of people who sustain the more frequent higher, or rostral injuries, also die within a year.

Short-term costs for hospitalization, equipment, and home modifications are approximately $140,000 for an SCI patient capable of independent living. Lifetime costs may exceed one million dollars. Costs may be three to four times higher for the SCI patient who needs long-term institutional care. Overall costs to the American economy in direct payments and lost productivity are more than $10 billion per year.

Causes

The spinal cord descends from the brain down the back through the spinal canal that lies within the bony spinal column. The spinal cord is composed of neurons and axons (nerve cells). The neurons carry sensory data from the areas outside the spinal cord (periphery) to the brain, and convey motor commands from brain to periphery. Peripheral neurons are bundled together to comprise the 31 pairs of peripheral nerve roots. The peripheral nerve roots enter and exit the spinal cord by passing through the spaces between the stacked vertebrae (the neural foramen). Each pair of nerves is named for the vertebra from which it exits. These are known as:

• C1-8. These nerves enter from the seven cervical or neck vertebrae.
• T1-12. These nerves enter from the thoracic or chest vertebrae.
• L1-5. These nerves enter from the lumbar vertebrae of the lower back.
• S1-5. These nerves enter through the sacral, or pelvic vertebrae.
• Coccygeal. These nerves enter through the coccyx, or tailbone.

Peripheral nerves carry motor commands to the muscles and internal organs, and transmit sensations from these areas and from the body's surface. (Sensory data from the head, including sight, sound, smell, and taste, do not pass through the spinal cord and are not affected by most SCIs. These nerves, called the cranial nerves, pass through the brain stem.) Damage to the spinal cord interrupts these signals. The interruption damages motor functions that enable the muscles to move, sensory functions (e.g., feeling heat and cold, and autonomic functions (e.g., urination, sexual function, sweating, and blood pressure).

Spinal cord injuries most often occur where the spine is most flexible, in the regions of C5–C7 of the neck, and T10–L2 at the base of the rib cage.

Several physically distinct types of damage are recognized. Sudden and violent jolts to nearby tissues can jar the cord. This jarring causes a transient neurological deficit, known as temporary spinal concussion. Concussion symptoms usually disappear completely within several hours of injury. A spinal contusion, or bruise, is bleeding within the spinal column. The pressure from the excess fluid may kill spinal cord neurons. Spinal compression is caused by an object, such as a tumor, pressing on the cord. Lacerations, or tears, cause direct damage to cord neurons. Lacerations may be caused by bone fragments or missiles, such as bullets. Spinal transection describes the complete severing of the cord. Most spinal cord injuries involve two or more of these types of damage.