Causes of a spinal cord injury

Spinal cord injury (SCI) involves damage to the nerves within the bony protection of the spinal canal. The most common cause of SCI is trauma, although damage can occur from various diseases acquired at birth or later in life, from tumors, electric shock, poisoning or loss of oxygen related to surgical or underwater mishaps.

A common misconceptions is that a spinal cord injury means the spinal cord has to be severed in order for a loss of function to occur. In fact, most people who have sustained a SCI, the spinal cord is bruised and intact.

The spinal cord and the brain together make up the central nervous system (CNS). The spinal cord coordinates the body's movement and sensation. Therefore, 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. Often, this results in some level of paralysis.

Spinal cord injury is an age-old problem, but it wasn't until the 1940s that the prognosis for long-term survival was very optimistic. Prior to World War II, people routinely died of infections to the urinary tract, lungs, or skin. SCI went from a death sentence to a manageable condition. Nowadays, people with spinal cord injury approach the full life span of nondisabled individuals.

Acute care following an injury may involve surgery if the spinal cord appears to be compressed by bone, a herniated disk, or a blood clot. Traditionally, surgeons waited for several days to decompress the spinal cord, believing that operating immediately could worsen the outcome. More recently, many surgeons advocate immediate early surgery.

Generally speaking, after the swelling of the spinal cord begins to go down, most people show some functional improvement after an injury.

With many injuries, especially incomplete injuries (some motor or sensory function preserved below the injury level), a person may recover function eighteen months or more after the injury. In some cases, people with SCI regain some function years after the injury. There is a lot of information and resources to learn about the effects of a spinal cord injury. However, it is important to understand the functions of the spinal cord and its relationship to the brain.

The spinal cord includes neurons and long nerve fibers called axons. Axons in the spinal cord carry signals downward from the brain (along descending pathways) and upward toward the brain (along ascending pathways).

Many axons in these pathways are covered by sheaths of an insulating substance called myelin, which gives them a whitish appearance. Therefore, the region in which they lie is called "white matter." Loss of myelin, which can occur with cord trauma and is the hallmark of such diseases as multiple sclerosis, prevents effective transmission of nerve signals.

The nerve cells themselves, with their tree-like branches called dendrites that receive signals from other nerve cells, make up "gray matter." This gray matter lies in a butterfly-shaped region in the center of the spinal cord.

Like the brain, the spinal cord is enclosed in three membranes (meninges):

The spinal cord is organized into segments along its length, noted by their position along the thirty-three vertebrae of the backbone. Nerves from each segment connect to specific regions of the body, and thus control motor and autonomic functions.

In general, the higher in the spinal column an injury occurs, the more function a person will lose.

Cervical region The segments in the neck, or cervical region, referred to as C1 through C8, control signals to the neck, arms, hands, and, in some cases, the diaphragm. Injuries to this area result in tetraplegia, or as it is more commonly called, quadriplegia.

Thoracic region Nerves in the thoracic or upper back region (T1 through T12) relay signals to the torso and some parts of the arms.

Lumbar and sacral regions

Besides a loss of sensation or motor function, injury to the spinal cord leads to other changes, including loss of bowel, bladder, and sexual function, low blood pressure, autonomic dysreflexia (for injuries above T6), deep vein thrombosis, spasticity, and chronic pain.

Other secondary issues related to injury include pressure ulcers, respiratory complications, urinary tract infections, pain, obesity, and depression.

These complications of a spinal cord injury are mainly preventable with good healthcare, diet, and physical activity.

Several types of cells carry out spinal cord functions, including:

All of these glial cells produce substances that support neuron survival and influence axon growth. However, these cells may also impede recovery following injury; some glial cells become reactive and thereby contribute to formation of growth-blocking scar tissue after injury.

Nerve cells of the brain and spinal cord respond to trauma and damage differently than most other cells of the body, including those in the peripheral nervous system (PNS). The brain and spinal cord are confined within bony cavities that protect them, but this also renders them vulnerable to compression damage caused by swelling or forceful injury.

Cells of the CNS have a very high rate of metabolism and rely upon blood glucose for energy these cells require a full blood supply for healthy functioning; therefore, CNS cells are particularly vulnerable to reductions in blood flow (ischemia).

Other unique features of the CNS are the "blood-brain-barrier" and the "blood-spinal-cord barrier." These barriers, formed by cells lining blood vessels in the CNS, protect nerve cells by restricting entry of potentially harmful substances and cells of the immune system.

Trauma may compromise these barriers, potentially contributing to further damage in the brain and spinal cord. The blood-spinal-cord barrier also prevents entry of some therapeutic drugs.

What is the difference between a complete injury and an incomplete injury?

While there's almost always hope of recovering some function after a spinal cord injury, it is generally true that people with incomplete injuries have a better chance of getting more return.

The sooner muscles start working again, the better the chances are of additional recovery. When muscles come back later, after the first several weeks, they are more likely to be in the arms than in the legs.

As long as there is some improvement and additional muscles recover function, the chances are better that more improvement is possible. The longer there is no improvement, the lower the odds it will start to happen on its own.

A sample of the insights gleaned from the research on the prevalence of SCI include:

These findings have major implications for the treatment of spinal cord and paralysis-related diseases not only for those living with these conditions, but also for their families, caregivers, healthcare providers, and employers.

People who sustain a spinal cord injury are mostly in their teens or twenties, although as the population in general ages, the percentage of older persons with paralysis is increasing.

As the number of people living with paralysis rise and as they age with the injury, the costs associated with treating them increase as well. Each year, paralysis costs the healthcare system billions of dollars. Spinal cord injuries alone cost roughly $40.5 billion annually a 317 percent increase from costs estimated in 1998 ($9.7 billion).

People living with paralysis and spinal cord injuries are also often unable to afford health insurance that adequately covers the complex secondary or chronic conditions that are commonly linked with paralysis.

Currently, there is no cure for spinal cord injuries. However, ongoing research to test surgical and drug therapies is progressing rapidly. Injury progression prevention drug treatments, decompression surgery, nerve cell transplantation, nerve regeneration, and complex drug therapies are all being examined as a means to overcome the effects of spinal cord injury.

The Reeve Foundation has been leading the charge in spinal cord research for over 30 years, creating a framework to translate scientific breakthroughs into vital new therapies. Additionally, we have established programs to help cultivate the next generation of researchers that will safeguard a pipeline of innovation across the field and speed the delivery of cures for spinal cord injury.

If you are looking for more information on spinal cord injury or have a specific question, our information specialists are available business weekdays, Monday through Friday, toll-free at 800-539-7309 from 9am to 5pm ET.

Our Peer & Family Support Program also provides individualized support through a national peer-to-peer mentoring program.

Additionally, the Reeve Foundation maintains a SCI fact sheet with resources from trusted Reeve Foundation sources. Check out our repository of fact sheets on hundreds of topics ranging from state resources to secondary complications of paralysis.

We encourage you to also reach out to other SCI support groups and organizations, including:

Source: American Association of Neurological Surgeons, Craig Hospital, Christopher & Dana Reeve Foundation, The National Institute of Neurological Disorders and Stroke

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Spinal cord injury - Reeve Foundation

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