Spinal stenosis is a narrowing of spaces in the spine (backbone) that results in pressure on the spinal cord and/or nerve roots. This disorder usually involves the narrowing of one or more of three areas of the spine: (1) the canal in the center of the column of bones (vertebral or spinal column) through which the spinal cord and nerve roots run, (2) the canals at the base or roots of nerves branching out from the spinal cord, or (3) the openings between vertebrae (bones of the spine) through which nerves leave the spine and go to other parts of the body. The narrowing may involve a small or large area of the spine. Pressure on the lower part of the spinal cord or on nerve roots branching out from that area may give rise to pain or numbness in the legs. Pressure on the upper part of the spinal cord (that is, the neck area) may produce similar symptoms in the shoulders, or even the legs.
Who Gets Spinal Stenosis?
This disorder is most common in men and women over 50 years of age. However, it may occur in younger people who are born with a narrowing of the spinal canal or who suffer an injury to the spine.
What Causes Spinal Stenosis?
The normal vertebral canal provides adequate room for the spinal cord. Narrowing of the canal, which occurs in spinal stenosis, may be inherited or acquired. Some people inherit a small spinal canal or have a curvature of the spine (scoliosis) that produces pressure on nerves and soft tissue and compresses or stretches ligaments. In an inherited condition called achondroplasia, defective bone formation results in abnormally short and thickened pedicles that reduce the diameter (distance across) of the spinal canal.
What Are the Symptoms of Spinal Stenosis?
The space within the spinal canal may narrow without producing any symptoms. However, if narrowing places pressure on the spinal cord, cauda equina, or nerve roots, there may be a slow onset and progression of symptoms. The neck or back may or may not hurt. More often, people experience numbness, weakness, cramping, or general pain in the arms or legs. If the narrowed space within the spine is pushing on a nerve root, people may feel pain radiating down the leg (sciatica). Sitting or flexing the lower back should relieve symptoms. (The flexed position “opens up” the spinal column, enlarging the spaces between vertebrae at the back of the spine.) Flexing exercises are often advised, along with stretching and strengthening exercises.
People with more severe stenosis may have problems with bowel and bladder function and foot disorders. For example, cauda equina syndrome is a severe, and very rare, form of spinal stenosis. It occurs because of compression of the cauda equina, and symptoms may include loss of control of the bowel, bladder, or sexual function and/or pain, weakness, or loss of feeling in one or both legs. Cauda equina syndrome is a serious condition requiring urgent medical attention.
How Is Spinal Stenosis Diagnosed?
The doctor may use a variety of approaches to diagnose spinal stenosis and rule out other conditions.
- Medical history. The patient tells the doctor details about symptoms and about any injury, condition, or general health problem that might be causing the symptoms.
- Physical examination. The doctor (1) examines the patient to determine the extent of limitation of movement, (2) checks for pain or symptoms when the patient hyper-extends the spine (bends backwards), and (3) checks for normal neurologic function (for instance, sensation, muscle strength, and reflexes) in the arms and legs.
- X ray. An x-ray beam is passed through the back to produce a two-dimensional picture. An x ray may be done before other tests to look for signs of an injury, tumor, or inherited problem. This test can show the structure of the vertebrae and the outlines of joints, and can detect calcification.
- MRI magnetic resonance imaging). Energy from a powerful magnet (rather than x rays) produces signals that are detected by a scanner and analyzed by computer. This produces a series of cross-sectional images (“slices”) and/or a three-dimensional view of parts of the back. An MRI is particularly sensitive for detecting damage or disease of soft tissues, such as the disks between vertebrae or ligaments. It shows the spinal cord, nerve roots, and surrounding spaces, as well as enlargement, degeneration, or tumors.
- Computerized axial tomography (CAT). X rays are passed through the back at different angles, detected by a scanner, and analyzed by a computer. This produces a series of cross-sectional images and/or three-dimensional views of the parts of the back. The scan shows the shape and size of the spinal canal, its contents, and structures surrounding it.
- Myelogram. A liquid dye that x rays cannot penetrate is injected into the spinal column. The dye circulates around the spinal cord and spinal nerves, which appear as white objects against bone on an x-ray film. A myelogram can show pressure on the spinal cord or nerves from herniated disks, bone spurs, or tumors.
- Bone scan. An injected radioactive material attaches itself to bone, especially in areas where bone is actively breaking down or being formed. The test can detect fractures, tumors, infections, and arthritis, but may not tell one disorder from another. Therefore, a bone scan is usually performed along with other tests.
What Are Some Nonsurgical Treatments for Spinal Stenosis?
In the absence of severe or progressive nerve involvement, a doctor may prescribe one or more of the following conservative treatments:
- Nonsteroidal anti–inflammatory drugs (NSAIDs), such as aspirin, naproxen, ibuprofen, or indomethacin, to reduce inflammation and relieve pain.
- Analgesics, such as acetaminophen, to relieve pain.
- Corticosteroid injections into the outermost of the membranes covering the spinal cord and nerve roots to reduce inflammation and treat acute pain that radiates to the hips or down a leg.
- Anesthetic injections, known as nerve blocks, near the affected nerve to temporarily relieve pain.
- Restricted activity (varies depending on extent of nerve involvement).
- Prescribed exercises and/or physical therapy to maintain motion of the spine, strengthen abdominal and back muscles, and build endurance, all of which help stabilize the spine. Some patients may be encouraged to try slowly progressive aerobic activity such as swimming or using exercise bicycles.
- A lumbar brace or corset to provide some support and help the patient regain mobility. This approach is sometimes used for patients with weak abdominal muscles or older patients with degeneration at several levels of the spine.
When Should Surgery Be Considered and What Is Involved?
In many cases, the conditions causing spinal stenosis cannot be permanently altered by nonsurgical treatment, even though these measures may relieve pain for a period of time. To determine how much nonsurgical treatment will help, a doctor may recommend such treatment first. However, surgery might be considered immediately if a patient has numbness or weakness that interferes with walking, impaired bowel or bladder function, or other neurological involvement. The effectiveness of nonsurgical treatments, the extent of the patient’s pain, and the patient’s preferences may all factor into whether or not to have surgery.
The purpose of surgery is to relieve pressure on the spinal cord or nerves and restore and maintain alignment and strength of the spine. This can be done by removing, trimming, or adjusting diseased parts that are causing the pressure or loss of alignment. The most common surgery is called decompressive laminectomy: removal of the lamina (roof) of one or more vertebrae to create more space for the nerves. A surgeon may perform a laminectomy with or without fusing vertebrae or removing part of a disk. Various devices may be used to enhance fusion and strengthen unstable segments of the spine following decompression surgery.
Patients with spinal stenosis caused by spinal trauma or achondroplasia may need surgery at a young age. When surgery is required in patients with achondroplasia, laminectomy (removal of the roof) without fusion is usually sufficient.
National Institute of Neurological Disorders and Stroke
National Institutes of Health