The bony spine usually has 24 vertebrae: 7 cervical, 12 thoracic, and 5 lumbar. In the spine model I am holding in the picture above, the yellow pieces are the vertebra, which, together with the tailbone (sacrum), make up the bony spine. Each vertebra supports the load of the portion of the body above it, in addition to any additional weight the person is carrying and any additional stress temporarily placed on the spine during an injury event. Between the vertebrae are the intervertebral discs (the white pieces in the spine model above). The vertebrae and discs form the weight-bearing, flexible axis of the human body. Enclosed by the vertebrae and located behind the discs is the central spinal canal, which contains and protects the spinal cord (the orange cable in the spine model above).
The spinal cord is the thin, long, and soft continuation of the lower part of the brain that extends from the brainstem at the upper cervical spine to approximately the first lumbar (L1) vertebra (in most adults), from where it continues downward as a strand of multiple nerve roots (cauda equina). Spinal cord nerve fibers carry the electrical nerve signals from and to the brain and to and from the body below the head. The head has its own set of nerves (cranial nerves). The nerve fibers of the spinal cord leave and enter the bony spine as nerve roots through the intervertebral foramina (the holes in the side of the spine model above through which the orange cable is visible) at each vertebral level (the spine model above does not show the nerve roots themselves). Usually, there is lots of space around the spinal cord and the exiting nerve roots. Those spaces around the nerves of the spinal cord and cauda equina are filled with soft fat tissue and spinal fluid, which form a protective environment for those delicate and vulnerable nervous tissues.
Spinal injuries may affect the bones of the spine, the spinal cord, or the roots of the spinal nerves, which pass through the spaces between the vertebrae (neural foramina). The bundle of nerve roots that extend downward from the end of the spinal cord (cauda equina) may also be injured. At times, the treatment that is required can be extensive, and normal function may not fully return.
Most spinal cord injuries result from motor vehicle accidents, falls, assaults, and sports injuries and lead to some form of impingement or disruption of the delicate tissues of the spinal cord and nerve roots.
There are several ways in which the spinal cord or spinal nerves can be injured.
- The force of the injury can cause a concussion or bruise the delicate nerve structures. This may happen even more readily in individuals in which the space available for the spinal cord or nerve root was already narrowed before the injury because of spinal degeneration due to the aging process or congenital narrowing. In some instances, particularly in young children (who have very flexible spines), imaging findings can be very subtle or even normal.
- Disc herniations or spinal ligament ruptures can occur as a result of an injury that involves a lot of force, and the displaced disc tissue or unstable vertebrae can compress the spinal cord or spinal nerve roots.
- Vertebral fractures can occur from an injury that involves a lot of force but can also occur after relatively minor injuries (such as a fall on the same level) in people with osteoporosis (soft bone). Osteoporosis is a condition that is more common in older people, particularly in postmenopausal women.
- Infections can lead to infected fluid collections around the spine that may impinge nerve tissue and cause loss of function. This type of infection is more common in people with weakened immune systems, open skin sores, or decaying teeth, as well as in those who self-inject drugs of abuse.
Symptoms such as decreased skin sensation, decreased muscle strength, bowel or bladder impairment, and sexual function may occur early after an injury and may be temporary if the condition is promptly recognized and treated appropriately. Unfortunately, in some cases of nerve root or spinal cord injury, some permanent impairment of function remains. In some individuals, the impairment can be catastrophic. Paraplegia describes the inability of an individual to use the legs for walking and is usually associated with some degree of sensory impairment and bowel, bladder, and sexual function disturbance. Quadriplegia is the inability of an individual to fully use the arms and legs. Depending on the spinal level and severity of injury, some degree of function may be preserved. If the spinal cord injury occurs at a high spinal level (usually at or above the C4 spinal level), the ability to breathe may be impaired, and the affected individual may need a ventilator (breathing machine) either full-time or intermittently.
Magnetic resonance imaging (MRI; which assessed injury to the soft tissue, spinal cord, or ligaments) and/or computed tomography (CT; which assessed injury to bone) and x-rays are commonly used after an initial assessment by a medical provider raises suspicion for a possible spinal injury. The history (the event that caused the injury and the new difficulties the person experiences) and the physical examination (the impairment of function that the medical provider can objectively determine) will guide the medical provider in determining the appropriate diagnostic studies that will identify or rule out a suspected injury. It is part of the science and art of medicine for the medical provider to obtain and consider all the information provided by the history, the physical examination, and the diagnostic studies to arrive at the diagnoses (the names and corresponding codes that describe the exact observed anatomical and functional conditions present) and then propose appropriate forms of treatment.
Finding the most appropriate form of treatment after a spinal injury depends on several factors, including the person’s symptoms, exam findings, general health, age, and diagnoses. Fortunately, human beings are often surprisingly resilient and can “walk away,” even from relatively serious, high-speed, and high-force accidents and injuries. In many cases, the individual reports neck or back pain, but the examination and diagnostic imaging studies show no serious anatomic injury. In these instances, the diagnosis of a sprain/strain injury of the spine is often made. In most instances of sprain strain injuries, the painful symptoms are temporary and last only a few days to a few weeks. Most people are able to return to work after 1 week, and the majority of symptoms typically resolve within 2-4 weeks. Sometimes, medical providers recommend nonsteroidal anti-inflammatory medications like ibuprofen and naproxen for 1-2 weeks and prescribe up to ten physical or chiropractic therapy sessions. If symptoms unexpectedly linger, the diagnostic studies may be repeated, or different studies may be recommended.
For more serious spinal injuries, treatment may involve immobilization of the spine, drugs to relieve symptoms, sometimes surgery, and usually rehabilitation.