Spinal stenosis is a common condition that occurs when the space around the nerves or spinal cord narrows. The narrowing puts pressure on the spinal cord and/or the spinal nerve roots, often leading to symptoms of pain, tingling, numbness and muscle weakness.
The condition usually begins gradually and progresses over time as the narrowing increases. When the narrowing takes place in the spinal canal lumbar spine, the symptoms are felt in the lower back, buttocks, thighs, legs and feet. In essence, spinal stenosis is a “space issue” where the nerves compete with bone and soft tissues (ligamentum flavum) for space, and the nerves always lose.
The goal of treatment for spinal stenosis is to decompress or relieve pressure on the nerves.
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Who Gets Spinal Stenosis?
Spinal stenosis affects men and women equally and is most common in older adults (50+). Typically, the normal “wear-and-tear” or degenerative effects of aging and arthritis of the spine cause the overgrowth of bone into the spinal canal. Degenerative changes of the spine are seen in up to 95% of people by the age of 50! However, stenosis may occur in younger people who are born with a small spinal canal or those who have a herniated disc.
Where Can Spinal Stenosis Occur?
The most common location of spinal stenosis is in the lumbar or low back region and the neck or cervical region. Thoracic spinal stenosis, which affects the mid-back, is much less common.
Many people show evidence of spinal stenosis on MRI scans but have no signs or symptoms, even when the MRI findings are moderate to severe. This is because spinal stenosis usually occurs gradually over a period of years. This gradual compression gives the nerves a chance to accommodate and adjust slowly over time without any symptoms.
Symptoms can develop slowly over time, or rapidly over a period of months. Unfortunately, once these symptoms manifest, they can become chronic and quite debilitating. Symptoms vary, depending on the location, type and severity of spinal stenosis.
What Is the Most Common Type of Stenosis?
Lumbar spinal stenosis is the most common form of spinal stenosis. An estimated 400,000 Americans suffer from leg pain and/or low back pain caused by lumbar spinal stenosis. There are two canals in the lumbar spine that can be stenotic, the central and the foraminal canal. This discussion is about central canal stenosis.
What Are the Symptoms of Lumbar Spinal Stenosis?
Pain, tingling, weakness and numbness are common complaints. These symptoms can radiate to the buttocks, thighs, legs and feet. A general term for these symptoms is “sciatica”. Loss of walking endurance is another hallmark of lumbar spinal stenosis. This results from pain and cramping in the thighs and legs that is sometimes referred to as pseudo-claudication. This is because the pain from spinal stenosis can mimic the symptoms of vascular claudication in the legs caused by diminished blood perfusion of the legs. Loss of sexual drive and activity frequently accompanies painful back conditions like spinal stenosis.
Walking endurance can improve by leaning forward. Leaning forward can open the spinal canal a little and give the nerves a little more room. It’s common to hear someone say that they like to lean forward and push a cart at the grocery store or any place they have a cart. They call this a “positive shopping cart sign” which is a strong indicator that spinal stenosis is present.
Lower back pain is a common symptom or complaint. The pain is from the degenerative disc disease or degenerative (arthritic) facet joints that often accompany aging. The degenerative facets not only hurt but also get enlarged and overgrow into the spinal canal. This overgrowth into the spinal canal is a primary cause of stenosis.
What Are the Most Serious Symptoms?
Abnormal function or loss of bowel and/or bladder control (cauda-equina syndrome) is very serious. This may be considered a surgical emergency as the onset of symptoms can occur quickly.
Partial or complete leg paralysis is also serious, especially if it occurs over a short period of time. Cauda-equina and paralysis can be considered medical emergencies that require a trip to the emergency room as quickly as possible. Remember that acute symptoms from this type of stenosis are usually from a sudden herniation of a large disc.
(Both of these can be considered medical emergencies and you should get to an emergency room as quickly as possible!)
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What Aggravates and Relieves the Symptoms?
Leaning backward or extend your back can aggravate symptoms, especially when you walk downhill. Even just standing up straight for prolonged periods can cause back and leg symptoms. The pain gets better, sometimes almost immediately, in certain positions. When you flex or lean forward to walk uphill or push a grocery cart, the symptoms can improve immediately. Symptoms can also dissipate when sitting or lying down.
What Are 5 Causes that Contribute to Spinal Stenosis?
The bottom line of stenosis is a narrowing of the tunnels or canals that allow passage of the nerves. There are certain conditions that contribute to these phenomena of narrowing.
Aging
There are certain effects of “wear-and-tear” that cause either structural changes or inflammation that begin the narrowing process. Arthritis can cause both. All of the factors below occur with normal aging and may cause the tunnels in the spine to narrow:
- Gravity is working against your spine from the moment that you stand up. The weight of your body will collapse the discs over time and cause the spinal canal to shorten (notice how people get shorter as they age). There is a thick ligament (ligamentum flavum) that lines the inside of the spinal canal. When the spine shortens with age and disc collapse, this thick ligament can fold over on itself and contribute to stenosis of the spinal canal.
Arthritis
As you age, the spinal discs, which act as shock absorbers between the vertebrae, become dehydrated and start losing their spongy quality and structural integrity. This loss of water can lead to a loss of disc height. The loss of disc height can lead to arthritic or degenerative changes of the facet joints. These degenerative changes lead to overgrowth of the joints and thickening of the bones that can expand into the spinal canal, causing spinal stenosis.
Osteoarthritis is a chronic, degenerative process of joints that is more likely to occur in middle-aged and older people. Osteoarthritis of the facet joints breaks down the cartilage in your joints and is often accompanied by overgrowth of bone, formation of bone spurs and impaired function. The overgrowth of bone is the problem that crowds the spinal canal. A degenerative facet can also result in a synovial cyst that “herniates” into the spinal canal.
Heredity
If a spinal canal is narrow as it develops, it would be more sensitive to any cause of spinal stenosis.
Trauma
Accidents and injuries can cause disc herniations or displaced bone from a spinal fracture that can damage the contents of the spinal canal.
Tumors in the Spine (rare)
Irregular growths of soft tissue (malignant or benign) on the inside of the spinal canal can press on the spinal cord and nerves.
When Should Surgery Be Considered & What Are 5 Surgical Options?
If your pain does not respond to conservative treatments, or you lose strength or the ability to walk, you may need surgery. However, surgery might be considered immediately if you have acute weakness that interferes with walking, impaired bowel or bladder function, or other neurological deficits. The bottom line with surgery for stenosis is to decompress the nerves that are pinched or compressed. Beyond this, the next question is whether decompression is enough or does a fusion need to be done too.
Intervertebral Spacers
One of the main causes of spinal stenosis is the collapse of the intervertebral discs. This occurs with age and is the primary reason that people get shorter with age. The collapse of the disc spaces causes the facet joints to get arthritic and the ligamentum flavum to double up on itself. Both of these actions contribute to the stenosis.
One solution to this problem has been to insert a spacer between the spinous processes on the backside of the spine. This spacer holds the spinous processes apart and acts as a “jack” to hold the vertebrae apart. It compensates for the loss of height that the disc provided. One problem is that there is not a large enough spinous process on sacral 1 to hold a spacer, so spacers cannot be used for the L5-S1 level.
Decompressive Laminotomy
This refers to partial removal of the lamina to take the pressure off the affected nerves. This can be done with “minimally invasive” surgery or an open surgery with or without a fusion.
Endoscopic Spine Surgery
The goal of endoscopic surgery is decompression and to avoid a spinal fusion when possible. Endoscopic spine surgeons believe that, if surgery is necessary, then it should be performed through the smallest possible incision, with minimal disturbance of soft tissue. This procedure can address both soft tissues (ligamentum flavum) and bone overgrowth in the spinal canal that leads to stenosis.
The size of the tubes are as small as 7 mm, so the soft tissue trauma and scar tissue formation will be minimal. Another interesting feature of endoscopic spine surgery is that the surgery is performed in a water environment which means there is no air in contact with the operative site. This is because water is pumped continuously through the endoscope under pressure which means there is no air contact with the surgical site – lower infection rate and probably less scar formation. A small surgical incision (3/8 – 1/2 inch), means less pain postoperatively and a quicker recovery. Endoscopic spine surgery is the most minimal and least invasive because of the small incision.
Decompressive Laminectomy
The most common type of surgery for spinal stenosis is the laminectomy. This is an open back surgery that involves the complete removal of the lamina (a portion of the vertebra), ligamentum flavum and bone spurs if present. The surgery requires making an incision into the back (usually 2 to 6 inches) and often includes a spinal fusion.
Spinal Fusion
When the vertebrae shift or slip significantly (spondylolisthesis) or move excessively (instability), spinal stenosis can occur. The abnormal motion between the vertebrae can be eliminated with a spinal fusion. There are many variations of the spinal fusion, but the bottom line is that motion is eliminated with some hardware (rods, screws, cages for example) and bone graft material. Spinal fusion surgery is usually an open surgery procedure that uses a 3 to 6” incision and may be required in addition to decompression.
Each of these procedures has benefits, shortcomings and results to discuss inupcoming posts.