Lumbar Spinal Stenosis

Lumbar spinal stenosis means a constriction or lack of the usual space for the spinal cord or the nerves in the low back. The spinal cord ends in the upper part of the lumbar spine, usually around the level of the L1-2 disc. Therefore, it is mostly the collection of nerves called the "cauda equina" which can be compressed as it continues down toward the sacrum. Some individuals can have a "congenital" stenosis, meaning that the space in their spinal canal from birth is smaller than in most people. A large Herniated Lumbar Disc can reduce the space remaining for the cauda equina which is sometimes referred to as "secondary" stenosis. Typically, the term "lumbar spinal stenosis" means narrowing of the entire spinal canal including the central portion and is referred to as "central" stenosis. The facet joints on both sides toward the back of the canal can become arthritic and enlarged which produces narrowing of the side portions of the canal, a condition called "lateral recess stenosis". Nerves which are descending and about to exit are essentially obligated to occupy the lateral recesses and they can be trapped underneath the enlarged joint. The symptoms of both central and lateral spinal stenosis can be very similar to those of disc herniation although there are also some distinguishing features.

Cause of Lumbar Spinal Stenosis

Lumbar spinal stenosis with cauda equina compression usually occurs due to a combination of degenerative features in the lumbar spine. Enlargement of the facet joints ("facet hypertrophy") can crowd the spinal canal from the rear aspect on one or both the sides. Deposits of calcium in the ligament at the edges where the disc meets the vertebral bodies in front of the nerves, a condition called "spondylosis", can crowd the canal from the front along with herniated or bulged discs. The ligament bridging the gaps in the laminae on the back side of the spinal canal called the "yellow ligament" can become thickened and crowd the canal from the rear in the center or to the sides. In the vast majority of people, this represents an advanced form of degenerative change in the spine sometimes referred to as "osteoarthritis" or degenerative arthritis. Since these changes take many decades to develop, they are rare in younger individuals. Injuries to the low back usually have uncertain relevance to spinal stenosis and sometimes blend with a long history of variable low back discomfort. However, some people have no significant pain. The spinal canal is most often constricted at roughly the same region where two vertebral bodies are joined by an intervertebral disc. It is not at all unusual to see patients with stenosis of varying degrees at multiple segments. It is also not unusual to find misalignments of the vertebral bodies with one body at little forward or behind the other, a condition called "degenerative spondylolisthesis", although the structural stability is often quite solid. In some cases, there is instability and abnormal sliding movement of one body on the other which can cause problems. Moderate and even severe distortion of the cauda equina can be tolerated without symptoms in some individuals but others seem more sensitive to spinal stenosis and develop symptoms.

Treatment of Lumbar Spinal Stenosis

Although neurological symptoms are frequently simultaneous with mechanical symptoms of the spine when degenerative conditions are severe, most of the spinal stenosis patients in my experience have some history of mechanical back pains which they have learned to accommodate with general success. The neurological symptoms, if they develop, are not always associated with an increase in back pain although some people do have this. Excluding situations of structural instability, pains in the back are not a primary reason to consider surgery if no neurological features are present. Individuals with mild neurological or exclusively mechanical symptoms might improve with a brief course of physical therapy and anti-inflammatory medication. Once there are neurological symptoms and if they can be explained by spinal stenosis seen on diagnostic testing, surgical decompression becomes a potential option. Unfortunately, although milder symptoms might vary and occasionally disappear, there seems to be little option other than surgery when symptoms are moderate to severe. Surgical decompression usually involves removal of bone and ligament from the back side to "unroof" the spinal canal across the constricted areas. Some patients face a rather large amount of removal but, despite this, surgery can be tolerated even in most elderly people. Sometimes there is also reason to consider spinal fusion along with the decompression but most patients do not need this and will not be putting their spines "to the test" as much as younger persons following surgery.

Outcome of Lumbar Spinal Stenosis

The prognosis for patients with lumbar spinal stenosis is difficult to exactly predict but the chances for improvement of leg function easily justify an operation in properly selected individuals. In some cases, surgery can cause a dramatic improvement in leg strength and resolution of radiating pains which used to be quite incapacitating. Release from the detrimental effects of spinal stenosis on a person's capacity for independence can be gratifying. Factors which might limit the degree of recovery include general arthritis, muscular deconditioning, poor vascular supply to the legs, and nerve problems unrelated to the spine (such as "neuropathy" due to diabetes). Unless there is a structural instability, following a period of recuperation, most patients do not experience substantial worsening of back pain as a result of surgery. In fact, some people who undergo decompressive laminectomy, for some reason, have surprisingly little discomfort. Naturally, there is no cure for the degenerative arthritis in the spine which was the reason the stenosis occurred and most patients will continue to have some spinal arthritic pains. Reoccurrence of spinal stenosis at previously decompressed levels of the spine is possible but not common. Development of stenosis at different spinal segments in the future is sometimes seen but usually unrelated to the first surgery. In patients whose symptoms are mild or resolved without surgery, some arthritic pain might be all that happens on an indefinite basis.


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