SCIs result from damage to the vertebrae, ligaments, or disks of the spinal column or to the spinal cord itself.
A traumatic SCI may stem from a sudden blow to the spine that fractures, dislocates, crushes, or compresses one or more vertebrae. Car crashes are the leading cause of SCI among people younger than 65. Falls cause most SCIs in persons age 65 and older.
Since 2005, SCI has been caused by1:
- Car crashes (40.4%)
- Falls (27.9%)
- Violence, including gunshot wounds (15%)
- Sport-related accidents (8%)
- Other/unknown (8.5%)
What happens in your body when your spinal cord is injured?
When an SCI occurs, the spinal cord starts to swell at the damaged area, cutting off the vital blood supply to the nerve tissue and starving it of oxygen. This sets off a cascade of devastation that affects the entire body, causing the injured spinal tissue to die, be stripped of its insulation, and be further damaged by a massive response of the immune system.2
- Blood flow. The sluggish blood flow at the injury site begins to reduce the flow of blood in adjacent areas, which soon affects all areas of the body. The body begins to lose the ability to self-regulate, leading to drastic drops in blood pressure and heart rate.
- Flood of neurotransmitters. The SCI leads to an excessive release of neurotransmitters, or biochemicals that let nerve cells communicate with each other. These chemicals, especially glutamate, overexcite nerve cells, killing them through a process known as excitotoxicity. The process also kills the vital oligodendrocytes that surround and protect the spinal axons with the myelin insulation that allows the spinal nerves to transmit information to and from the brain.
- Invasion of immune cells. An army of cells of the immune system speeds to the damaged area of the spine. While they help by preventing infection and cleaning up dead cellular debris, they also promote inflammation. These immune cells stimulate the release of certain cytokines that, in high concentrations, can be toxic to nerve cells, especially those needed to maintain the myelin sheath around axons.3
- Onslaught of free radicals. The inflammation caused by cells in the immune system unleashes waves of free radicals, which are highly reactive forms of oxygen molecules. These free radicals react destructively with many types of cellular molecules, in the process severely damaging healthy nerve cells.
- Nerve cell self-destruction. A normally natural process of programmed cell death, known as apoptosis, goes out of control at the injury site. The reasons are not known. Days or weeks after the injury, oligodendrocytes die from no apparent cause, reducing the integrity of the spinal cord.
Additional damage usually occurs over the days or weeks following the initial injury because of bleeding, swelling, inflammation, and accumulation of fluid in and around the spinal cord.
- National Spinal Cord Injury Statistical Center. (2011). Spinal cord injury facts and figures at a glance. Retrieved May 21, 2012, from https://www.nscisc.uab.edu/PublicDocuments/nscisc_home/pdf/Facts%202011%20Feb%20Final.pdf (PDF - 197 KB)
- National Institute of Neurological Disorders and Stroke. (2012). Spinal cord injury: Hope through research. Retrieved May 22, 2012, from https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Spinal-Cord-Injury-Hope-Through-Research
- Edwards, S. P. The Dana Foundation. (2006). The other side of cytokines: The paradoxical effects of TNF-alpha. Retrieved June 27, 2012, from http://www.dana.org/Publications/Brainwork/Details.aspx?id=43669