Your ability to control your limbs after a spinal cord injury depends on two factors: the place of the injury along your spinal cord and the severity of injury to the spinal cord.

The lowest normal part of your spinal cord is referred to as the neurological level of your injury. The severity of the injury is often called "the completeness" and is classified as either of the following:

• Complete. If all feeling (sensory) and all ability to control movement (motor function) are lost below the spinal cord injury, your injury is called complete.
• Incomplete. If you have some motor or sensory function below the affected area, your injury is called incomplete. There are varying degrees of incomplete injury.

Additionally, paralysis from a spinal cord injury may be referred to as:

• Tetraplegia. Also known as quadriplegia, this means your arms, hands, trunk, legs and pelvic organs are all affected by your spinal cord injury.
• Paraplegia. This paralysis affects all or part of the trunk, legs and pelvic organs.

Your health care team will perform a series of tests to determine the neurological level and completeness of your injury.

Spinal cord injuries of any kind may result in one or more of the following signs and symptoms:

• Loss of movement
• Loss or altered sensation, including the ability to feel heat, cold and touch
• Loss of bowel or bladder control
• Exaggerated reflex activities or spasms
• Changes in sexual function, sexual sensitivity and fertility
• Pain or an intense stinging sensation caused by damage to the nerve fibers in your spinal cord
• Difficulty breathing, coughing or clearing secretions from your lungs

Spinal cord injuries may result from damage to the vertebrae, ligaments or disks of the spinal column or to the spinal cord itself.

A traumatic spinal cord injury may stem from a sudden, traumatic blow to your spine that fractures, dislocates, crushes or compresses one or more of your vertebrae. It also may result from a gunshot or knife wound that penetrates and cuts your spinal cord.

Additional damage usually occurs over days or weeks because of bleeding, swelling, inflammation and fluid accumulation in and around your spinal cord.

A nontraumatic spinal cord injury may be caused by arthritis, cancer, inflammation, infections or disk degeneration of the spine.

Brain and central nervous system

The central nervous system comprises the brain and spinal cord. The spinal cord, made of soft tissue and surrounded by bones (vertebrae), extends downward from the base of your brain and is made up of nerve cells and groups of nerves called tracts, which go to different parts of your body.

The lower end of your spinal cord stops a little above your waist in the region called the conus medullaris. Below this region is a group of nerve roots called the cauda equina.

Tracts in your spinal cord carry messages between the brain and the rest of the body. Motor tracts carry signals from the brain to control muscle movement. Sensory tracts carry signals from body parts to the brain relating to heat, cold, pressure, pain and the position of your limbs.

Damage to nerve fibers

Whether the cause is traumatic or nontraumatic, the damage affects the nerve fibers passing through the injured area and may impair part or all of your corresponding muscles and nerves below the injury site.

A chest (thoracic) or lower back (lumbar) injury can affect your torso, legs, bowel and bladder control, and sexual function. A neck (cervical) injury affects the same areas in addition to affecting movements of your arms and, possibly, your ability to breathe.

Common causes of spinal cord injuries

The most common causes of spinal cord injuries in the United States are:

• Motor vehicle accidents. Auto and motorcycle accidents are the leading cause of spinal cord injuries, accounting for almost half of new spinal cord injuries each year.
• Falls. A spinal cord injury after age 65 is most often caused by a fall. Overall, falls cause more than 15 percent of spinal cord injuries.
• Acts of violence. Around 12 percent of spinal cord injuries result from violent encounters, often involving gunshot and knife wounds.
• Sports and recreation injuries. Athletic activities, such as impact sports and diving in shallow water, cause about 10 percent of spinal cord injuries.
• Alcohol. Alcohol use is a factor in about 1 out of every 4 spinal cord injuries.
• Diseases. Cancer, arthritis, osteoporosis and inflammation of the spinal cord also can cause spinal cord injuries.

Although a spinal cord injury is usually the result of an accident and can happen to anyone, certain factors may predispose you to a higher risk of sustaining a spinal cord injury, including:

• Being male. Spinal cord injuries affect a disproportionate amount of men. In fact, females account for only about 20 percent of traumatic spinal cord injuries in the United States.
• Being between the ages of 16 and 30. You're most likely to suffer a traumatic spinal cord injury if you're between the ages of 16 and 30.
• Being older than 65. Falls cause most injuries in older adults.
• Engaging in risky behavior. Diving into too-shallow water or playing sports without wearing the proper safety gear or taking proper precautions can lead to spinal cord injuries. Motor vehicle crashes are the leading cause of spinal cord injuries for people under 65.
• Having a bone or joint disorder. A relatively minor injury can cause a spinal cord injury if you have another disorder that affects your bones or joints, such as arthritis or osteoporosis.

At first, changes in the way your body functions may be overwhelming. However, your rehabilitation team will help you develop the tools you need to address the changes caused by the spinal cord injury, in addition to recommending equipment and resources to promote quality of life and independence. Areas often affected include:

• Bladder control. Your bladder will continue to store urine from your kidneys. However, your brain may not be able to control your bladder as well because the message carrier (the spinal cord) has been injured.

The changes in bladder control increase your risk of urinary tract infections. The changes also may cause kidney infections and kidney or bladder stones. During rehabilitation, you'll learn new techniques to help empty your bladder.

• Bowel control. Although your stomach and intestines work much like they did before your injury, control of your bowel movements is often altered. A high-fiber diet may help regulate your bowels, and you'll learn techniques to optimize your bowel function during rehabilitation.
• Skin sensation. Below the neurological level of your injury, you may have lost part of or all skin sensations. Therefore, your skin can't send a message to your brain when it's injured by certain things such as prolonged pressure, heat or cold.

This can make you more susceptible to pressure sores, but changing positions frequently — with help, if needed — can help prevent these sores. You'll learn proper skin care during rehabilitation, which can help you avoid these problems.

• Circulatory control. A spinal cord injury may cause circulatory problems ranging from low blood pressure when you rise (orthostatic hypotension) to swelling of your extremities. These circulation changes may also increase your risk of developing blood clots, such as deep vein thrombosis or a pulmonary embolus.

Another problem with circulatory control is a potentially life-threatening rise in blood pressure (autonomic hyperreflexia). Your rehabilitation team will teach you how to address these problems if they affect you.

• Respiratory system. Your injury may make it more difficult to breathe and cough if your abdominal and chest muscles are affected. These include the diaphragm and the muscles in your chest wall and abdomen.

Your neurological level of injury will determine what kind of breathing problems you may have. If you have a cervical and thoracic spinal cord injury, you may have an increased risk of pneumonia or other lung problems. Medications and therapy can help prevent and treat these problems.

• Muscle tone. Some people with spinal cord injuries experience one of two types of muscle tone problems: uncontrolled tightening or motion in the muscles (spasticity) or soft and limp muscles lacking muscle tone (flaccidity).
• Fitness and wellness. Weight loss and muscle atrophy are common soon after a spinal cord injury. Limited mobility may lead to a more sedentary lifestyle, placing you at risk of obesity, cardiovascular disease and diabetes.

A dietitian can help you eat a nutritious diet to sustain an adequate weight. Physical and occupational therapists can help you develop a fitness and exercise program.

• Sexual health. Sexuality, fertility and sexual function may be affected by a spinal cord injury. Men may notice changes in erection and ejaculation; women may notice changes in lubrication. Physicians specializing in urology or fertility can offer options for sexual functioning and fertility.
• Pain. Some people experience pain, such as muscle or joint pain, from overuse of particular muscle groups. Nerve pain can occur after a spinal cord injury, especially in someone with an incomplete injury.
• Depression.Coping with all the changes a spinal cord injury brings and living with pain causes some people to experience depression.