What is Spinal Stenosis?
Stenosis means narrowing of a hollow tube. Spinal stenosis is a condition where there is narrowing of the spinal canal causing compression of the spinal cord lying within it and/or narrowing of the spaces through which the spinal nerves leave the spinal column. Spinal stenosis usually occurs as part of the normal aging process. Compression of the nerves and blood vessels caused by stenosis leads to the typical features of pain. Depending on the nerves affected, there may be symptoms such as weakness, numbness, or pain in the neck, back, arms, or legs. However, not all patients with spinal stenosis develop symptoms.
Spinal stenosis is most common in the cervical (neck) and lumbar (back) regions. Almost 75% of cases of spinal stenosis occur in the lumbar region. Treatment may be conservative, such as rest, medication, physical therapy, and braces. Surgical decompression may be considered when other treatments fail to alleviate symptoms and mobility or quality of life is significantly impaired or in case of progressive muscle weakness with risk of permanent nerve damage.
The spinal column or the backbone is made of 33 small bones known as the vertebrae, which are stacked on top of each other. It runs from the cervical region (neck area) at the top down to the thoracic region (mid back) and then to the lumbar region (lower back). Spongy discs (intervertebral discs) between the vertebral bones act as a cushion and allows flexibility of the spine. The central hollow portion of the vertebrae form the spinal canal through which the spinal cord passes from the base of the skull to the level of L1 vertebra. The neural foramina are openings on either side of the vertebrae through which the spinal nerves exit the spinal column to supply various parts of the body.
There are 31 pairs of spinal nerves which contain both motor and sensory fibers. It carry signals to and from the brain to the rest of the body. The 8 pairs of cervical nerves supply the arms, neck, and upper trunk. The 12 pairs of thoracic nerves supply the trunk and abdomen. The 5 pairs of lumbar nerves and the 5 pairs of sacral nerves supply the legs, bladder, bowel, and sexual organs. There is 1 pair of coccygeal nerve. The spinal cord ends at the level of L1 vertebra. Below this level is the extension of the spinal cord known as the cauda equina which consists of fibers of the lumbar, sacral and coccygeal spinal nerves.
Spinal stenosis can result from a variety of conditions that leads to narrowing of the spinal canal and compression of the spinal cord or the spinal nerves. As a result of the normal aging process, the intervertebral disc may degenerate and collapse, most frequently at the level of C5-6 and C6-7. This may lead to bone growths on the vertebral body (osteophytes) or spur formation.
A bone growth towards the back (posteriorly) may cause lateral recess stenosis, which can impinge on the spinal nerves. The degenerative changes associated with arthritis such as bulging of the intervertebral disc and thickening of the ligaments between the vertebrae can also cause narrowing of the spinal canal and neural foramina. In spondylolisthesis, there is slippage of a vertebra on the one below, leading to spinal stenosis. This may be congenital (present from birth), degenerative, or following a spinal cord injury.
Causes and Risk Factors
Spinal stenosis can result from a variety of conditions that lead to narrowing of the spinal canal and compression of the spinal cord or the spinal nerves.
- Age – usually over 50.
- Family history
- Congenital or birth defects of the spine.
- Past history of herniated or slipped disc.
- People who are subjected to heavy strain on the back, such as laborers, athletes, and dancers.
- Spinal injury.
- Bone disease, such as Paget’s disease of the bone and achondroplasia.
- Spinal tumors.
Signs and Symptoms
Spinal stenosis may be present in some cases without producing any symptoms. Symptoms of spinal stenosis occur due to limited space in the spinal canal. They usually appear gradually, are unilateral in most cases, and may get worse with time. The symptoms will depend upon the nerves affected.
- Pseudoclaudication or discomfort in the legs on walking, which is relieved by rest, bending forwards, or walking uphill is the most common presentation. As a result, patients often adopt a simian posture (resembling a monkey or an ape) with a forward stoop and flexion of the hips and knees.
- Pain in other parts of the body, such as neck, shoulder, arms, and back may also be present.
- Problems with balance and coordination.
- Inability to control bladder or bowel function.
- Medical history may reveal a possible causative event or symptoms indicative of spinal stenosis.
- Physical examination, including neurological examination.
- CT scan
Conservative treatment consists of :
- Avoiding activities that worsen symptoms.
- Medication like nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen which may help to reduce inflammation and swelling around the nerves. Cortisone may be given orally or as epidural injection to reduce inflammation.
- Physical therapy – exercises to strengthen the muscles around the spinal column.
Spinal Stenosis Surgery
Spinal stenosis surgery helps to relieve pressure on the spinal cord or the spinal nerve roots by removing damaged parts of the spine and enlarging the spinal canal. However, symptoms may recur after a few years and surgery may be required again in a small number of cases.
Indications for Surgery
Surgery for spinal stenosis should be considered when :
- Other treatments fail to alleviate symptoms.
- The mobility or quality of life is significantly impaired.
- Progressive muscle weakness with risk of permanent nerve damage.
Types of Spinal Stenosis Surgery
Decompressive laminectomy is the most common type of surgery for spinal stenosis, done to relieve pressure on the spinal cord or spinal nerve roots. Laminectomy involves removal of the lamina, a portion of the vertebra that may be causing narrowing of the spinal canal. Fibrous tissue and bone spurs may also be removed. While laminectomy is more commonly done for lumbar spinal stenosis, cervical spinal stenosis is usually treated with anterior cervical discectomy and fusion (ACDF), where the intervertebral disc is removed as well as any bone spurs present.
Foraminotomy involves expanding the neural foramina to provide more space for the spinal nerve roots.
Arthrodesis or spinal fusion is sometimes done along with decompressive laminectomy to help stabilize certain portions of the spine. Arthrodesis may be done by various methods, such as bone taken from elsewhere in the body may be used to make a bridge between adjacent vertebrae, which will stimulate formation of new bone. In some patients, metal implants are used to hold the vertebrae together until new bone formation occurs between them. Spinal fusion is a major surgery, which may take several hours to perform. It may help to improve motor function and also relieve pain.
Laminoplasty involves creating space in the back of the spinal canal by opening the back of the spine and leaving it open with bone grafts or plates.
Complications of Spinal Stenosis Surgery
Complications may be related to other pre-existing medical conditions such as diabetes, hypertension, or cardiovascular problems.
Complications of the surgery itself may include :
- Complications of anesthesia.
- Nerve injury, causing numbness, weakness, or paralysis.
- Deep vein thrombosis, leading to pulmonary embolism.
- Instability of the spine.
- Injury to the surrounding fibrous tissue.
- Loss of bladder or bowel control.
- Difficulty in passing urine.
- Death, in rare cases.
Repeat surgery may sometimes be necessary.