The Nerve of Back Muscles and the Snowball Effect on Spinal Aging
How and when parts of the body age are the focus of many scientists. The spine and its nearby muscles are part of these studies. The steps in the aging of the spine are called the degenerative cascade. This refers to the fact that once a single event occurs, many other changes follow as a result.

For example, when the disc between the bones of the vertebrae starts to age, small tears in the outer rings (annulus) of the disc can develop. This in turn may allow the center of the disc (nucleus) to push out of its normal space. Next, the disc may begin to collapse, causing the nearby joints to bear increased weight and pressure. Changes in the joints, including production of joint pain, can result in this downward spiral.

The back muscles may have an important role in this cascade, too. These muscles, called the paraspinals, help control and move the spine. The loss of nerve impulses to the muscles is called denervation. Denervation of the paraspinal muscles can occur as the result of many spinal disorders.

When these impulses are knocked out, the paraspinal muscles can't do their job. One theory is that these muscles lose their ability to stiffen the spine during activity, leading to excess movement in the problem area of the spine. This sets up a snowball effect in which the aging process speeds up in the nearby parts of the spine.

Scientists who have studied the degenerative cascade think there are ways to protect the paraspinals. Specific exercises may help prevent damage that otherwise leads to denervation. As a general rule, doctors also believe that taking special care when doing back surgery is important. The paraspinal muscles do best when they are preserved and unharmed. During recovery after surgery, activities that stress the denervated paraspinals, such as overworking these muscles, should be avoided. In the future, there may be prevention and drug treatment to avoid paraspinal muscle injury.
Andrew J. Haig, MD. Paraspinal Denervation and the Spinal Degenerative Cascade. In The Spine Journal. September/October 2002. Vol. 2. No. 5. Pp. 372-380.