What is spinal stenosis and what causes it?
Lumbar spinal stenosis is a very common condition in the spine. "Stenosis" means "narrowing". In the lumbar spine, the nerves are encased in a structure called the "dural sac". The dural sac is contained in an area called the spinal canal. When the spinal canal is narrowed (or "stenotic"), this means there is less space available for the dural sac, which can lead to pressure on the spinal nerves that are within this dural sac.
The most common cause of spinal stenosis is arthritis in the spine, which results from the normal aging process. As we age, several changes occur in the region surrounding the spinal canal. For example, discs deteriorate and bulge into the spinal canal and the joinTs and bones in the spine may harden or become overgrown, forming bone spurs that begin to press on the nerves. This is called arthritis or "degeneration" and these arthritic changes can narrow the space around the spinal nerves. Spinal stenosis most often occurs in patients over age 55. Much less commonly, the condition occurs in younger patients who were born with a narrow spinal canal, which is called congenital spinal stenosis.
Symptoms of Spinal Stenosis
Patients with lumbar stenosis usually complain of pain and discomfort in the buttock region and in the legs. Symptoms are very variable. For example, some patients have numbness and pain in the calves only with walking, some have pain in the buttock region that does not go into the legs. Patients may have pain and discomfort in one leg or both legs, and the pain may begin in the buttocks and extend a variable distance into the legs, sometimes all the way down to the feet. A common finding is leg discomfort that is worse with walking, but that is relieved somewhat with sitting and rest. Bending forward at the waist typically relieves or improves the pain in the legs. Many patients with spinal stenosis have what is referred to as the "shopping cart sign". This means when they go grocery shopping, they lean forward on the shopping cart – what they are doing is bending at the waist, which opens up room for the spinal nerves, thus relieving the discomfort in the legs.
The best test for diagnosing spinal stenosis is an MRI of the lumbar spine. Some patients cannot get an MRI (for example, patients with a pacemaker), and in these patients, a CT myelogram is the test of choice.
The initial treatment for spinal stenosis consists of anti-inflammatory medications (ibuprofen, naproxen), physical therapy and epidural steroid injections. Of these, epidural injections are most likely to provide pain relief.
Patients who do not respond to the above treatments and who continue to experience pain that is affecting their quality of life are good candidates for what is called "surgical decompression". The term "decompression" means just that – taking pressure off pinched nerves. As in all spine surgery, patient selection is very important in achieving a good result. Patients who have significant low back pain and minimal to no leg pain generally do not have a good result. Surgery is primarily for patients who experience buttock or leg symptoms.
There are several variations to the type of surgery that is performed, but the common thread among all of them is that pressure is taken off the nerves that are pinched ("Decompression"). Some patients have a pinched nerve on only the left or right side, some have pinched nerves at only one level, while others have pinched nerves on both sides and/or at 2 or 3 levels. The type of surgery that is done is tailored to each patient, depending on the above scenarios.
If a lumbar laminectomy or laminotomy is recommended to you, Click here on more information about this procedure. A lumbar laminectomy is essentially the same thing as a lumbar decompression. The term "laminectomy" literally means removing the lamina (which is the bone on the back of the spine – you can think of it as the "roof" of a house).
Some patients with spinal stenosis also have what is referred to as "spinal instability". The word "instability" should not alarm you. It just means that there is abnormal motion (or too much motion) at that level in your spine, which is caused by wearing out of the joints in your spine. When the joints wear out due to arthritis, they become incompetent and that spinal level is described as "unstable". But this does not mean that your spine is going to fall apart. Spinal instability is somewhat of an arbitrary term, and there is no precise definition for it. One finding that implies some degree of spinal instability is the presence of spondylolisthesis. This term refers to an X-ray finding of one vertebra shifting forward in relationship to the vertebra below it. Click here for a picture and xray of spondylolisthesis. When spinal stenosis is present with spondylolisthesis, fusion is also recommended in addition to a decompression.
Another finding that implies instability is a curvature in the spine called scoliosis. Some patients with scoliosis develop stenosis and as the spine deteriorates from arthritis, the joints become incompetent and the vertebrae begin to shift in relation to one another. In such cases, fusion is also necessary.
So to summarize
- Patients with spinal stenosis WITHOUT instability need a laminectomy alone. Fusion is not necessary in these patients
- Patients with spinal stenosis AND instability need a laminectomy AND fusion.
The implications of the presence of instability are important. A laminectomy alone is a relatively minor surgical procedure, and if only one level is involved, this can be an outpatient procedure. If a fusion is necessary, this adds to the length of the surgery and the magnitude of the surgery. Screws and rods, in addition to bone graft, are inserted to obtain a fusion. So the hospital stay can be longer and the length of recovery is also considerably longer than a laminectomy alone.