A spinal cord injury (SCI) is damage to the spinal cord, whether temporary or permanent. These changes can lead to loss of muscle function, autonomic function (a subdivision of the peripheral nervous system that supplies smooth muscles and glands, as well as heart rate, digestion, respiratory rate, pupillary response, urination, flight-or-fight response and sexual arousal), and sensation. SCIs can cause pain, numbness and more severe problems such as incontinence, paralysis, tetraplegia (loss of use of all four limbs) and paraplegia (loss of motor and/or sensory function in the lower part of the body). SCIs include problems such as herniated discs.
There are many types of SCI, but they can be divided into three main categories: mechanical forces, toxic and ischemic (from lack of blood flow). Then there are two further subcategories: primary injury (cell death following the immediate aftermath of injury and the biochemical cascades from the original injury that cause further damage). SCIs are also split into where on the spine the injury occured.
The letter represents the part of the spine affected, and the number the specific discs and spinal nerves affected. At each level of the spinal column, spinal nerves branch off from either side of the spinal cord and exit between a pair of vertebrae, innervating a specific part of the body. The area of skin innervated by a specific spinal nerve is called a dermatome, and the group of muscles innervated by a single spinal nerve is called a myotome. These categories include:
- Cervical 1 – 8 (C 1-8) – SCI that affect the uppermost part of the spine. Areas of the body affected include the head, neck, shoulders, forearms and hands.
- Thoracic 1 – 12 (T1 – T12) – SCIs that affect the middle part of the spine and therefore the middle of the body. This includes the chest, back, stomach and underarms.
- Lumbar 1 – 5 (L1 – L5) – SCIs that affect the lower part of the body, specifically the right leg, parts of the left leg and pelvis.
- Sacral 1 – 5 (S1 – S5) – SCIs that affect the lower part of the body, including the left leg, parts of the right leg and the groin region.
- Coccyx – tailbone.
SCIs are usually evaluated using X-rays, CT scans or MRIs. SCIs are thought to affect between 10.4 and 83 people per million every year. In North America, about 39 in every million people incur a traumatic SCI each year. In the USA specifically, the rate is 40 in every million people incurring a traumatic SCI every year. Falls and other high impact injuries are common causes of SCIs, but people with arthritis or multiple sclerosis (MS) are also at high risk of SCIs.
Treatment for SCIs includes surgery, physiotherapy and rehabilitation exercises, antihypotensive agents (vasopressors), such as epinephrine or hydrocortisone, central venous catheters (a catheter put into the heart in order to control blood pressure), occupational therapy, recreational therapy and psychotherapy. Medications are usually prescribed to control pain, activate signalling pathways, and prevent inflammation, such as atorvastatin, fenretinide, opioids, antidepressants and NSAIDs.