Spinal Cord Injury

What is a Spinal Cord Injury?

A spinal cord injury (SCI) is damage to the spinal cord that results in a loss of function, such as mobility, feeling and/or autonomic function (for example, bladder control) in the parts of the body served by the spinal cord below the level of the injury. Injury can occur at any level of the spinal cord and can be complete injury with a total loss of sensation and muscle function, or incomplete, meaning some nervous signals are able to travel past the injured area of the cord.

In the majority of cases, the damage results from physical trauma, such as falls, car accidents, sports injuries or gun shot or knife injuries, but spinal cord injury can also result from non-traumatic causes, such as infections, insufficient blood flow, tumours or disease (polio, spina bifida, Friedreich’s ataxia, etc.).
The spinal cord does not have to be completely severed for a loss of function to occur. In fact, in most people with spinal cord injury, much of the spinal cord is intact but damaged due to compression by the vertebrae resulting in loss of function.

Spinal cord injuries can be divided into two types of injury – functionally complete and functionally incomplete.

  • Functionally Complete Spinal Cord Injury: a complete injury means there is no function below the level of the injury – no sensation and no voluntary movement. Both sides of the body are equally affected. Functionally complete spinal cord injury can be further divided into:

    • Anatomically Complete Spinal Cord Injury: the spinal cord is completely severed. There are no spared tracks passing from above the injury to below the injury.

    • Anatomically Incomplete Spinal Cord Injury: the spinal cord contains some spared tracks at the level of injury; however, these pathways are non-functional. Most functionally complete spinal cord injuries are of this type.

  • Functionally Incomplete Spinal Cord Injury: an incomplete injury means there is some function below the primary level of 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. With the advances in acute treatment of spinal cord injuries, incomplete injuries are becoming more common.

Cervical spine MRI of patient with SCI: C4 fracture and
dislocation, spinal cord compression
Source: Wikipedia

How are Spinal Cord Injuries Classified?

There are multiple ways to classify spinal cord injuries according to (i) the cause of the injury, (ii) the location of the injury, and (iii) the degree of impairment.

  • Cause of the injury – Spinal cord injury can be traumatic or non-traumatic and can be classified into three types based on cause: mechanical forces, toxic, and ischemic (from lack of blood flow). The damage can also be divided into primary and secondary. The primary injury is the cell death that occurs immediately in the original injury. The secondary injury includes the biochemical cascades that are initiated by the original insult and cause further tissue damage. These secondary injury pathways include the ischemic cascade, inflammation, swelling, cell suicide and neurotransmitter imbalances that occur minutes or weeks following the injury.
  • Location of the Injury – The location of a spinal cord injury refers to the location along the spinal cord that the primary damage is incurred. In general, the higher in the spinal column the injury occurs, the more dysfunction a person will experience.
  • Degree of Impairment – The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), published by the American Spinal Injury Association (ASIA)4, is widely used to document sensory and motor impairments following SCI. It is based on neurological responses, touch and pinprick sensations tested in each dermatome, and strength of the muscles that control key motions on both sides of the body. Muscle strength is scored on a scale of 0–5 and sensation is graded on a scale of 0–2: 0 is no sensation, 1 is altered or decreased sensation, and 2 is full sensation. Each side of the body is graded independently.

ASIA Impairment Scale for Classifying Spinal Cord Injury

Current Treatments and Unmet Needs

Unfortunately, currently there’s no way to reverse damage to the spinal cord incurred in a spinal cord injury. Researchers are continually working on new treatments, including prostheses and medications that may promote nerve cell regeneration or improve the function of the nerves that remain after a spinal cord injury.

Spinal cord injury treatment focuses on preventing further injury, rehabilitation, and empowering people with a spinal cord injury to return to an active and productive life.

Spinal Cord Injury Facts and Figures

  • In the US there are approximately 17,700 new spinal cord injury cases each year.1
  • The estimated number of people living with spinal cord injury in the United States is approximately 290,000 persons.2

References

  1. Jain, N.B., Ayers, G.D., Peterson, E.N., Harris, M.B., Morse, L., O’Connor, K.C., and Garshick, E. (2015). Traumatic spinal cord injury in the United States, 1993-2012. JAMA 313, 2236–2243.
  2. Lasfargues, J.E., Custis, D., Morrone, F., Carswell, J., and Nguyen, T. (1995). A model for estimating spinal cord injury prevalence in the United States. Paraplegia 33, 62–68.
  3. National Spinal Cord Injury Statistical Center, Facts and Figures at a Glance. Birmingham, AL: University of Alabama at Birmingham, 2020
  4. Betz, R., Biering-Sørensen, F., Burns, S.P., Donovan, W., Graves, D.E., Guest, J., Jones, L., Kirshblum, S., Krassioukov, A., Mulcahey, M.J., et al. (2019). The 2019 revision of the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI)—What’s new? Spinal Cord 57, 815–817.