What Is A Spinal Cord Injury?

Spinal Cord Injury Definition

A spinal cord injury (SCI) usually begins with a sudden, traumatic blow to the spine. The blow fractures, compresses, or dislocates some of the vertebrae, which are the rings of bone that protect the nerves inside the spinal cord. Damage to the nerves causes a disruption in the pathway that carries messages up and down the spinal cord between the brain and the rest of the body. A spinal cord injury can affect feeling and movement below the level of the injury temporarily or permanently.

The Spinal Cord Pathway

Your spinal cord is a bundle of nerves about 18-inches long that runs down the middle of your back. It extends from the base of the brain down to somewhere near your waist. The nerves within the spinal cord constitute a pathway that carries messages back and forth from your brain to all parts of your body. This vital pathway is protected by a column of bony rings called vertebrae that surround the spinal cord. When an injury causes the vertebrae to break and press up against the spinal cord, the nerves within can be damaged, and the pathway broken or interrupted.

The break or interruption means that the messages that flow between the brain and the spinal cord can no longer get through. The paralysis that results depends on the location and extent of the break.

It’s a common misconception that the spinal cord is severed in people with a spinal cord injury. In fact, in most people with SCI, the spinal cord is intact; it is the cellular damage to the nerves that causes paralysis. This damage can occur even without damage to the vertebrae.

Complete Spinal Cord Injuries

A spinal cord injury is called “complete” if all feeling and ability to control movement is lost below the level of the injury, which suggests that no messages are getting through the spinal cord. With a complete spinal cord injury, you have no feeling or movement below the level of the injury. The damage to the nerves prevents any message from going back and forth between your body and your brain.

Incomplete Spinal Cord Injuries

With an incomplete spinal cord injury, the ability of the spinal cord to convey messages to and from the brain is not completely lost. Some signals still get through despite the damage. This means you have some feeling and movement below the level of the injury. With advances in the acute treatment of spinal cord injuries, incomplete injuries are becoming more common.


Paraplegia involves loss of movement and feeling in the lower half of the body. It means that paralysis affects all or part of the trunk and both legs, but not the arms. It usually happens as a result of injuries at T1 or below.

Quadriplegia (also called Tetraplegia)

Quadriplegia involves the loss of movement and feeling in all four limbs–both arms and legs. It usually happens as a result of an injury at T1 or above.

Effects on the Body

People with SCI often have medical complications resulting in bladder, bowel and sexual dysfunction. They may also develop chronic pain, respiratory complications, spasticity, unstable blood pressure and heart problems. Autonomic Dysreflexia, a condition in which the involuntary nervous system causes a dangerous spike in blood pressure that can lead to stroke, may affect people with spinal cord injuries at or above the T6 level.

Levels of Spinal Cord Injury

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