The spinal discs are located between the bony vertebrae of the spine. They act as shock absorbers within the spine, and they’re kept in place by the muscules and ligaments that surround and hold the spine together. Each disc has an inner core called the nucleus pulposus and a tough outer membrane called the annulus fibrosus. With the process of aging, these discs change in consistency from that of gel-filled sacs as children to that of hard rubber by middle age.
Disc herniations can occur both as a result of trauma and for no apparent cause other than the wear and tear that occurs with aging. These can include bulges, in which the disc membrane doesn’t rupture, but the shape of the disc swells outward in one or more directions. An injury, however, can also actually rupture the membrane and cause the inner material of the disc to extrude outward. In either situation, pressure from the bulging or ruptured disc can be placed either upon the spinal nerves as they exit from the spinal cord or upon the spinal cord itself. This pressure is what produceds most of the very significant pain associated with disc injuries.
Herniated discs are more common in the lumbar spine — the lower back — than in the neck region — the cervical spine. They are most common in people of middle age. Causes of disc herniation can include normal aging processes, poor body mechanics such as awkwardly lifting a heavy weight, or traumas such as sports injuries, motor vehicle collisions, and slip and fall incidents.