What Happens in Lumbar Stenosis?

In the normal spinal canal, the nerve roots are contained in the thecal sac and exit between each vertebra (foramina). The central spinal canal and the foramen contain the thecal sac and nerve roots respectively.

Figure 1

The canal and foramen are formed (Figure 1) by bony structures (vertebral body, facets, pedicles) as well as soft tissue structures (ligamentum flavum, facet capsules, intervertebral disc annulus). As we age, degenerative changes occur in our spine causing narrowing of the central spinal canal area, and/or the area where the nerve roots exit the spinal canal (foramina). One of these degenerative changes is the formation of extra bony growths called osteophytes. Additionally, the large connective "band" (ligamentum flavum) which runs along the inside the spinal canal can become coarse and thickened also causing narrowing of the central canal space.

How do you get Lumbar Stenosis?

Though we don't know why some people develop symptoms of spinal stenosis and others do not, we do know that some people are born with the predisposition towards it. In normal development, the spinal canal reaches adult size by about age four. If the canal does not reach adequate size by this age, then it will never "catch up" and spinal stenosis results and occurs uniformly throughout the spine (Figure 2a).

Figure 2a

With this type of stenosis, you may remain symptom free until other conditions further compromise the canal space. Such conditions include formation of extra bony growths (osteophytes), trauma, or intervertebral disc problems. Others may develop stenosis without this predisposition but can instead "acquire" it through trauma, degenerative changes (osteophytes), bulging of the large connective "band" (ligamentum flavum), and most commonly by spondylosis.

As we age our body begins to dehydrate. This process causes our intervertebral discs to dry out thus decreasing the area of cushioning between each vertebra. Normally our discs separate each vertebra, act as shock absorbers during regular activity, and allow our spine to move freely. A decrease in the area of cushioning leads to trauma of our vertebrae and formation of osteophytes. This condition is referred to as Spondylosis. Several of these changes are demonstrated in Figure 2b.

Figure 2b

Figure 2c demonstrates changes from the normal anatomy to those found in lumbar and foraminal; stenosis.

Figure 2c

 

The vertebrae are connected in the back by the bony facets and intervening pars interarticularis. These structures in combination with the intervertebral disc help to interlock each level of the spine. Degeneration, spondylosis, and some congenital conditions can cause these joints to progressively fail. Eventually, a vertebra can slip forward and compromise either the central canal space and/or the opening through which the nerve root exits the spinal canal (foramina). This condition is called spondylolisthesis (Figure 3). It is more prominent in groups of people with who place a lot of stress on their backs including manual laborers, heavy machine operators, and professional athletes.

Figure 3

Symptoms: What to Look For

LSS can cause compression of the spinal nerves in the lumbar area (cauda equina). At the same time, the cauda equina between the levels of stenosis becomes congested due to alterations in the blood vessels that drain blood from the area. This congestion prevents the nerve roots from conducting effectively, especially when walking. When this happens, there can be a significant amount of pain, numbness, and/or weakness in the buttocks, thighs, and legs. Often, this can severely limit or altogether stop the patient from walking. The discomfort usually disappears after 5 -10 minutes of rest. Lying with the legs flexed, sitting, or squatting can also help as these maneuvers increase the area of the spinal canal. These symptoms may begin in the lower legs and progress upwards toward the buttocks or they may begin in the buttocks and progress downward. This is referred to a "sensory march." Low back pain is also a very common complaint. The symptoms may begin on one side but will often end up involving both sides. You may hear your doctor refer to this as neurogenic claudication.

Neurogenic claudication tends to occur more frequently in men than women and is usually seen after age 50. Most people will gradually decrease the walking distance until they reach a comfort zone. Typically, patients are able to walk at least 100 meters. Unfortunately, this condition is lifelong and can be progressive. Sometimes physical therapy, medical pain management and other non-surgical measures can provide adequate symptomatic relief. If your symptoms continue to progress or become too painful, surgery to widen the spinal canal may be your best option (surgical decompression).

It is important for your physician to differentiate neurogenic claudication from decreased blood flow to the lower extremities due to calcified blood vessels (peripheral vascular disease) since this condition also often occurs in older people and has similar symptoms. However, symptoms of peripheral vascular disease typically are not relieved by changes in posture and do not exhibit any of the "sensory march" symptoms.

LSS can also cause pain extending down the leg along the area that corresponds to the affected nerve root. This occurs because the area where the nerve root exits the spinal canal (foramina) has become narrowed causing pressure on the nerve root. Foraminal stenosis is thus a form of LSS and can coexist with central stenosis and classic claudication symptoms. Often, foraminal stenosis does respond well to conservative treatment without surgery, but may require 6 to12 months for recovery. However, those with persistent severe pain will likely benefit from surgery to widen the foraminal space (surgical decompression).

Diagnostic Studies: X-rays, CT Scan, MRI, Myelography

Diagnostic studies are usually performed if symptoms do not subside after a period of 3 to 6 months of therapy such as rest, anti-inflammatory medications, and physical therapy. X-rays are ordered cautiously because many people who do not have any symptoms of spinal stenosis have abnormal x-rays, CT scans, and MRI's. Surgery should only be performed in patients whose symptoms correlate with findings on these studies and a history that supports these findings.

Typically, plain x-rays are done first. They are helpful in looking for infection, tumors, and identifying problems with alignment of the spine (Figure 4a).

Figure 4a

But X-rays will not always identify LSS. CT scans have become the most widely used test for evaluating the spine because it is noninvasive and provides three-dimensional views of the spine. It is also particularly helpful in differentiating between hard tissue (bony osteophytes) and soft tissue (intervertebral discs). Myelography involves injection of dye into the spinal sac where is mixes with the cerebrospinal fluid. Any outward protrusion will block the flow of the dye. CT scans done in conjunction with myelography are particularly helpful diagnosing LSS (Figure 4b).

Figure 4b

The MRI is the newest non-invasive diagnostic test for evaluating the spine and offers more precise description of disc disease, soft tissue changes and the degree of stenosis (Figure 4c).

Figure 4c

Treatment Options: Medication, Physical Therapy, Surgery

Once the diagnosis of LSS is made, you and your doctor will decide on the most appropriate therapy including medications, physical therapy, and surgery. Many patients will respond to non-surgical interventions. Anti-inflammatory medications such as ibuprofen and acetaminophen can help reduce symptoms in the earlier stages of LSS. Cortisone injections at the site of low back pain can also help reduce inflammation of the spinal nerves and nerve roots to help control pain. Usually no more than three cortisone injections per year are recommended. However, these are temporary relief measures and symptoms may resurface once the medication wears off.

In addition to medications, physical therapy can help to restore flexibility and strengthen back and abdominal muscles to provide substantial relief from symptoms of LSS. If non-surgical measures do not offer adequate relief, your doctor may recommend back surgery.

Who is a Candidate for Surgery to Relieve LSS?

Patients who are generally in good health should have no problem undergoing surgery. Age alone is not a major limiting factor however, if you have other medical conditions such as high blood pressure, or diabetes that typically accompany old age, surgery may pose greater risk.

Surgical Procedures

The operations typically used to treat Lumbar Stenosis include the classic laminectomy, laminotomy, and foraminotomy. For patients who meet the proper indications, these procedures can also be combined with a spinal fusion operation. The most commonly used decompressive surgery is the laminectomy. To perform a classic laminectomy a 3-4 inch incision is made in your lower back (Figure 5a), though it may be longer depending on how many levels of your lamina are affected.

Figure 5a

A laminectomy involves removing the bony extensions (lamina) from the backside of the vertebral body which are causing pressure on the spinal sac and/or the nerve roots (Figure 5c-e).

Figure 5c	Figure 5d	Figure 5e

Often, only a portion of the lamina needs to be removed to relieve the pressure on the nerve roots (laminotomy). The ligaments (ligamentum flavum) and soft-tissue (facet capsules, herniated or bulging discs) in the affected area are also removed to increase the canal space. At the same time, a portion of the facet joints at the sides of the lamina may also be removed since they also cause increased pressure on the central and foraminal areas (Figure 5b).

Figure 5b

The goal of a foraminotomy is to enlarge the space where the nerve roots exit the spinal canal thus decreasing pressure on them. Foraminotomies can be done by themselves or often in conjunction with a laminectomy.

Some patients may develop instability of the spine with surgery. This occurs when a lot of bone needs to be removed and/or when multiple levels are operated on in order to provide adequate decompression. As such, many surgeons prefer more limited lamina removal (laminotomy) and only partial facet removal (medial facetectomy). Others may already have instability from their disease as in cases of spondylolisthesis. For all these patients, a spinal fusion is needed in addition to decompression. Spinal fusion involves grafting bone onto the spine and using instrumentation, such as screws and rods, to support the spine and provide stability. Your neurosurgeon can usually determine whether you will need a fusion prior to surgery so that you will be able to discuss this possibility beforehand.

Microendoscopic Laminectomy

The Micro-Endoscopic Laminotomy (MEL) is an exciting new treatment option for patients who are candidates for the surgical treatment of lumbar stenosis. MEL accomplishes the same goal as the classical laminectomy but it involves using a minimally-invasive approach, a state-of-the-art surgical endoscope for visualization , and microsurgical decompressive techniques.

A thin needle is placed under fluoroscopic (x-ray) guidance down to the involved level on one side of the midline spine (Figure 6a).

Figure 6a

A small ½ to 1-inch incision is then made around this needle. Using a set of tapered metal dilators passed over the guiding needle, the tissue and muscles are then gently spread off the underlying bone (Figure 6b,c).

Figure 6b	Figure 6c

A hollow metal cylinder is then passed down to the area of the stenosis and secured. Through this working channel, a rigid surgical micro-endoscopic camera is placed to provide your surgeons with a close-up, magnified view of the pathology (Figure 6d,e).

Figure 6d

Figure 6e

With this close-up operative view, your surgeon can then microsurgically remove the bone (Figure 6f) compressing the nerve roots thereby relieving the stenosis.

Figure 6f

In addition, soft tissue such as the ligamentum flavum (Figure 6g) and herniated discs can also be removed through the MEL technique (Figure 6h). In our experience, excellent decompression of both sides of the spinal canal can be achieved through this one-sided approach.

Figure 6g

Figure 6h

In the hands of experienced spinal, the same amount of decompression can be achieved through the MEL technique as would typically be obtained through open surgery (Figure 6i).

Figure 6i

Through the same incision, the surgeon can swing the endoscope to decompress the level immediately above and below as well. Overall when compared to traditional open procedures, the MEL technique offers the attractive benefits of far less disruption of normal tissue, faster surgical time, decreased post-operative discomfort, quicker recovery time, and a typically more rapid return to normal activity. You should contact your surgeon to find out if the MEL operation is available in your area and whether or not you are a candidate for the procedure.

Your Recovery

You will be asleep during surgery under general anesthesia. After surgery you will be taken to the recovery area where you will be monitored until you awaken. Most patients can begin getting out of bed on the same day surgery is performed. Activity is gradually increased and patients are typically able to go home within two to five days after a classical laminectomy and one to two days after MEL. However, these time frames may be longer depending on the extent your surgery.

Typically you will experience pain for a few weeks after surgery and you may need over-the-counter or prescription pain medications. Your neurosurgeon may also prescribe a course of physical therapy to help you regain strength in your abdomen and back and promote a better recovery. The total recovery time after lumbar surgery can take anywhere from eight weeks to six months, depending on the severity of your condition before surgery as well as your overall health condition prior to surgery. Common sense tells you the healthier you are the quicker you will heal. As smoking weakens bones, accelerate degeneration and slows the healing process, we also highly recommend you stop before any type of surgical procedure.

Understanding the Risks

Decompressive laminectomy is the most common and successful surgery done for treatment of symptoms associated with LSS. Over 60,000 such surgeries are done annually on patients over 60. However, it is still surgery and any surgery involves risk. Your neurosurgeon will discuss these risks in detail with you, but the most common ones are bleeding, infection, injury to the nerve, scarring, and the usual risks of anesthesia. Those with accompanying chronic health conditions such as diabetes, obesity, and high blood pressure or those with advanced stenosis carry greater risk and may have poorer outcomes. Ultimately you will be the one to decide which treatment option is best for you. Your neurosurgeon will discuss all options with you and explain the pros and cons of each to help you decide. Only you can determine if your pain warrants a more definitive treatment plan such as surgery.