Stenosis means narrowing, and when referenced to the spine means narrowing or constriction of the spinal canal, which contains the spinal cord and nerves. Although the lumbar spine region is more accommodating and forgiving (than the cervical or thoracic regions) of neurologic compression, it is also the most common location of its occurrence. Spinal stenosis is generally sequelae of aging and degenerative arthritis of the spine. As the degenerative process occurs, the ligamentum flavum becomes hypertropic (overgrown) and the facet joints enlarge and develop osteophytes (bone spurs) that encroach into the spinal canal. As the nerve compression worsens, patients often develop pain, numbness, weakness, and/or difficulty walking (neurogenic claudication). Spinal stenosis is increasingly being recognized as a major cause of pain and dysfunction in our society, particularly since the elderly population is growing exponentially. It is expected that by 2030, 20% of the population will be 65 years or older.
The most common cause of spinal stenosis is degenerative osteoarthritis of the spine, specifically the hypertrophy of the ligamentum flavum and the formation of large osteophytes adjacent to the facet joints. This is a gradual process that causes progressive compression of the spinal cord and neural elements. Mechanical irritation may cause a local inflammatory response, and decreased vascularity may cause decreased conduction of the nerve signals. Although aging and degeneration is the most common cause of stenosis, patients may have other medical conditions or trauma that predisposes them to develop spinal stenosis.
The degenerative process is typically slow and relentlessly progressive. Patients often have low back pain and stiffness. Many patients have mechanical symptoms that are aggravated with increased activity and relieved by rest. When the stenosis is severe, most patients will develop neurogenic claudication (radiating leg pain, numbness and/or weakness with standing and walking) and some patients will develop bowel or bladder dysfunction. The symptoms are often so gradual, that patients seek medical attention very late in the course of this condition. Patients may be so disabled and weak that they require the use of a wheelchair for mobility. In rare instances, severe spinal stenosis can cause paraplegia and/or bowel/bladder incontinence. This condition is called cauda equina syndrome when it occurs in the lumbar spine region, and is considered to be a surgical emergency.
The physical findings for patients with spinal stenosis are limited. Patients may or may not demonstrate tenderness and spasm, but usually have decreased lumbar range-of motion, especially extension. Patients are generally in greater pain with standing and leaning backward. If the spinal nerves are severely compressed, there may be significant numbness (loss of sensation) in the leg or foot and some of the leg muscles may be focally weak. Deep tendon reflexes may be diminished or absent. Pulses and vascularity of the leg should be normal. If not, the patient may also have concomitant vascular disease and vascular claudication.
Plain x-rays of the spine will not show spinal stenosis because an x-ray only shows bone structures, not the cartilage disc, ligaments, or spinal nerves. However, the spine x-rays may reveal that the patient has severe osteoarthritis, and this would suggest a high probability of spinal stenosis if correlative symptoms were present. A magnetic resonance imaging test (MRI) is necessary to clearly define the severity and extent of spinal stenosis and neurologic compression, and is noninvasive (no needles or dye injection). Before MRI was invented, patients were required to have a CT, myelogram, or CT-myelogram in order to confirm the diagnosis of herniated nucleus pulposus. MRI is now much easier to perform and generally provides better visualization of the stenotic lesions. However, some patients are not able to have an MRI, such as those patients with a cardiac pacemaker, and must have one of the other described imaging tests.
There are no laboratory tests used to diagnose spinal stenosis. Occasionally, specific tests are ordered to rule out infection or other causes or back pain, sciatica, or claudication.
The condition of spinal stenosis is extremely common and usually easily diagnosed. It can be complicated when the symptoms or physical findings are atypical. Some patients will complain of isolated “hip pain” or “knee pain,” and be evaluated and treated for this rather than a back problem. It is important for the clinician to conduct a thorough history and clinical examination prior to formulating a diagnosis so as not to misdiagnosis this condition. Imaging studies (and occasionally laboratory tests) must be used to clarify the diagnosis.
The treatment of lumbar spinal stenosis often depends on the severity of a patient’s symptoms and the severity of neurologic compression. Patients with mild or moderate stenosis may respond very well to conservative treatments. Conservative treatments may consist of oral anti-inflammatory medications and pain medications. Muscle relaxant medications should be used for severe pain and muscle spasms, and only for short duration in elderly patients. Complications secondary to medications are more common in the elderly, and all medications should be closely monitored by the prescribing physician. Physical therapy, manipulation, and modalities may also be utilized, primarily to improve a patient’s strength, endurance, and level of function. Epidural steroid injections may provide dramatic improvement of pain symptoms, but only 25% have long-term relief according to a study authored by Surin.
When a patient has severe spinal stenosis and symptomatology, or a patient with mild or moderate stenosis has failed conservative modalities, surgical intervention is considered. Patients noted to have multiple spinal levels involved are indicated for a laminectomy. If a patient only has one or two levels of involvement, then minimally invasive procedures such as a microscopic laminectomy or intra-laminar decompression may be considered. The goals of surgery are to improve a patient’s pain and level of function, as well as prevent further deterioration of function and worsening pain. Patients who demonstrate instability or mal-alignment of the spine may also require spinal fusion (mending the spine bones together) in addition to a decompression procedure. There is a high rate of success for patients treated surgically, yet there is a notable increase in morbidity and mortality in elderly patients over 80 years-old, especially those with significant medical problems. A careful preoperative evaluation and delicate perioperative and postoperative management is particularly important in this setting.
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