Degenerative Disc Disease – Spinal Stenosis
The progressive degeneration, through wear and tear, of the intervertebral discs is considered a natural part of ageing. With an accumulation of shocks and knocks, and jolts and bumps to the spine throughout our lives it is unsurprising that the discs’ ability to cushion our movements gradually reduces. Degenerative disc disease is often responsible for spinal stenosis as disc herniation or a bulging disc can directly impinge upon spinal nerves in the neural foramen or spinal canal, can cause spinal cord compression, or may contribute to the collapse of the disc space and the resulting slippage of the spine. Symptoms of spinal stenosis due to degenerative disc disease usually worsen for patients during the day as inflammation and back strain gradually increase with movement. Use of an inversion table may help remove the compression temporarily and afford some relief from back and/or neck pain, paraesthesia, and numbness or weakness.
Intervertebral discs are made up of a fibrous outer shell called the annulus fibrosus, and a soft gel-like center called the nucleus pulposus. The discs are arranged in a radial striated fashion which limits the degree of twisting that can occur in the spine. This protects the spinal nerves and the spinal cord from undue compression but the protective mechanism may be impaired where degenerative disc disease is present. Discs are largely made up of water and, with no direct nutrient supply, they can quickly become dehydrated and brittle. A dry and malnourished disk is more likely to warp, tear, or herniate and cause the inner gel to leak into the spinal canal where it can cause spinal stenosis and nerve compression.
Diagnosis of Degenerative Disc Disease and Spinal Stenosis
Degenerative disc disease may be indicated by a patient’s symptoms and confirmed by an X-Ray, MRI or CT scan which can show the relative dehydration of an intervertebral disc quite clearly as it appears much darker than the better nourished discs. Many patients have a degree of degenerative disc disease at a number of levels after they are fifty or older and this can make it difficult to pinpoint the exact vertebral level where spinal stenosis is causing nerve root or spinal cord compression responsible for their symptoms of back and/or neck pain.
A physician may use selective nerve root blocks to determine which nerve is at the root of the symptoms with the patient experiencing relief from their condition when the appropriate nerve is treated with an analgesic and corticosteroid injection. If the treatment and diagnostic method fails to relieve the pain then another level may be considered responsible for the symptoms.
Causes of Degenerative Disc Disease and Spinal Stenosis
In some cases a degenerative disc may be able to be treated using non-surgical traction to encourage it to retract back into its disc space and remove the compression on the spinal nerves. Where significant levels of degeneration are present this is unlikely to benefit a patient however, especially where the disc has already herniated and is causing spinal stenosis. Six months of conservative treatment is a common therapeutic course and often involves the use of NSAIDs for spinal stenosis pain management, and physical therapy to help with mobility and strength and conditioning training. Many patients use natural remedies to encourage their connective tissues to remain healthy although some of these are unlikely to provide much benefit to the deeper tissues of the spine due to the poor circulation in the area.
Those who smoke are much more likely to suffer from degenerative disc disease and spinal stenosis due to the damaging effects of the chemicals in tobacco. Quitting smoking is a priority for anyone with evidence of disc degeneration, along with achieving a healthy weight and remaining physically active. Those who practice yoga regularly and over the long-term are less likely to suffer from severe disc degeneration than the general population, most likely as result of improved flexibility and strength of the muscles supporting the spine (Jeng, 2010). This effect is much more pronounced in the cervical spine compared to the lumbar spine, perhaps due to the increased amount of movement and strain experienced in the neck.
Those who suffer acute trauma to the spine may incur intervertebral disc damage or even an acute herniation of a previously unproblematic bulging disc. Whiplash is associated with an increased incidence of degenerative disc disease with symptoms more likely to occur earlier due to general instability and initial damage to the cervical spine. Degenerative disc disease in the lumbar spine is responsible for around 62% of all spinal intervertebral disease, with 36% accounted for by cervical disc degeneration (Windsor, 2004). Cervical spondylosis and spondylolisthesis, along with Rheumatoid Arthritis, osteoporosis, and other diseases affecting the bones and joints can contribute to the development of spinal stenosis by exacerbating degenerative disc disease. Conversely, instability of the spine caused by disc degeneration and the collapse of the disc space may induce arthritic changes or spinal slippage causing spinal stenosis, spinal muscle and ligament degeneration and spinal instability.
Treatment of Degenerative Disc Disease and Spinal Stenosis
Surgery is usually a last resort for degenerative disc disease, and takes the form of discectomy, disc replacement, spinal fusion, and laminectomy amongst other procedures. Degenerative disc disease with myelopathy is less common than radiculopathy due to disc degeneration and usually requires fairly urgent surgery in order to prevent permanent spinal cord damage. Radicular pain often responds well to conservative treatments and patients who can continue daily activities and manage their symptoms are usually not considered as surgical candidates due to the complications that can arise after spinal surgery.
Where myelopathy is causing weakness, numbness, mobility problems, or bladder and/or bowel incontinence decompressive back surgery is indicated to relieve pressure on the spinal nerves and spinal cord. However, the number one reason for failed back surgery syndrome is misdiagnosis and operation on the wrong vertebral level, making discectomy and other surgical procedures very complex decisions. Where degeneration is evident at a number of vertebral levels it may be inadvisable to fuse the spine after decompression without also fusing these degenerative vertebral levels. This is because the pressure on the spine may be transferred from the fused region to the vertebrae above and below in what is referred to as adjacent segment syndrome. Where isolated disc degeneration is present it may be possible to relieve spinal stenosis using an artificial disc replacement or transforaminal interbody fusion procedure (or similar fusion using a posterior or anterior approach). If osteophytes are also evident then the spinal stenosis may be adequately relieved by a partial discectomy and foraminotomy operation without the need for spinal fusion.