Stenosis is defined as narrowing. The term is commonly applied to spinal anatomy to describe an abnormal reduction in size of the various structures, which transmit nerves.
For example, spinal stenosis refers to an abnormal narrowing of the spinal canal (Anatomy fig.2) which holds the spinal cord or the nerves, which flow from it in the low back (cauda equina). Compression of the nerves as they pass through this narrowing causes arm or leg symptoms such as numbness, weakness, or pain.
Symptoms from spinal stenosis, which occur with activity, are defined as neurogenic claudication. Spinal stenosis can be divided into two major categories: congenital or degenerative (acquired).
Congenital spinal stenosis occurs because of abnormal formation of one or various components of the spine which through abnormal growth produces canal narrowing. This type of stenosis is found inpatients with short stature.
Degenerative stenosis is more common than congenital stenosis and is found in older individuals. Age related changes of the spine such as disc degeneration and arthritis causes bone buildup in and around the canal and nerve holes producing nerve compression. (Anatomy fig.6).
Because bone buildup occurs in areas of the spine with high mobility, it is commonly found in the neck and low back, and rarely found in the thoracic spine. Because nerve compression from spinal stenosis occurs over time, characteristically the symptoms are insidious and rarely occur acutely with for example, an identifiable traumatic event. The patient may notice that over weeks or months he or she has noticed that with walking the legs become tired or numb. The symptoms are not quickly relieved with rest as is common with claudication secondary to poor blood flow in the legs. Changes in position of the spine can affect symptoms quickly-for example, many patients admit that when they lean on a shopping cart, the tiredness in their legs improves. Forward flexion of the spine produces widening of the spinal canal and nerve holes which relieves pressure on the nerves and decreases symptoms.
As with most spinal problems, conservative measures are useful to alleviate symptoms in the early stages of the problem. Physical therapy may improve muscle tone and fitness, but ultimately will not reverse the narrowing and nerve compression, which is the primary problem.
During epidural injections, a needle is introduced into the spine at or near the narrowing and cortisone is placed on the nerves. The anti-inflammatory effect of the steroids may reduce nerve swelling. If the nerve swelling decreases, the relative relationship of the nerve diameter to the bony hole becomes favorable, thereby reducing symptoms. Traditionally, three epidurals per year can be performed.
If the symptoms become refractory to conservative treatments, then surgery is indicated. Removal of bony narrowing around nerves is called decompression. The operative strategy will depend not only on the location of the spinal narrowing, but the relative stability and condition of the spine as a whole. If the stenosis is associated with a spondylolisthesis, then a fusion may have to be performed with the nerve decompression. Curvature, or scoliosis of the spine, may also complicate that treatment in that bony narrowing relieved with surgery may recur quickly in a curved spine because of asymmetric collapse on the concavity of the curve. Stabilization may have to accompany the decompression in these cases for long term and sustained good results after surgery. Decompression can be done a number of ways. The most popular techniques are laminectomy and laminotomy.
Click on laminectomy or laminotomy for explanations of these procedures. Every patient’s surgical treatment should be individualized according to his or her anatomy and presentation.