‘Slip Disc’ is a very common working diagnosis that all of us practitioners hear day in and day out. What exactly is this slip disc and what are its repercussions – this is what I would like to discuss in this column.
Our spine is composed of a series of vertebrae, which are stacked on top of each other like a pile of cards. These vertebrae are linked to each other with the help of soft fleshy structures called as the intervertebral disc. The spinal column is, I feel, nature’s engineering marvel. Give a challenge to any engineer to make a structure that is strong but flexible, and I am sure he will have no answer for the same.
Our spinal column is one such natural engineering feat. The disc, which is there in between two vertebrae, is so string that it can withstand the pressure that is equivalent to the pressures sustained by the tyre of a Boeing 747 jumbo jet when it strikes the runway during landing. What a marvelous structure that nature has created! But, I feel that humans probably have beaten nature in this aspect. In spite of being such a strong structure, we human beings have managed to conquer nature and managed to injure this structure every now and then. The disc is not a solid structure. It is actually a thick viscous jelly, which is held in place with a help of a strong fibrous tissue membrane. This strong fibrous tissue membrane is called as the annulus. As the spine flexes and extends or twists and turns, the jelly in this strong annulus will adjust to the forces upon it, thereby maintaining the stability and the balance of the spine. In front of the disc is the spinal cord, which starts from the brain and passes down to the tailbone or the sacrum.
At each level of every disc, the spinal cord gives out two nerves, which are called as the spinal nerves. They will traverse out of a small hole within the vertebra and then run down along either the arm or the trunk or the abdomen or the legs to supply the area of skin and muscle and joint which is specific to that particular nerve level.
A disc problem can present in two ways. Firstly, you have an acute disc herniation or prolapse. In this, due to an acute injury, there is a tear within the annulus ligament and then the jelly material will either bulge or protrude or it will escape from the disc and come inside the spinal canal. As a result of the same, there is usually irritation of the nerve or in extreme cases there is compression on the nerve. Based on the degree of irritation or compression, the patient would usually get symptoms of tingling, numbness, pain and muscle spasm in relation to the distribution of the nerve. The second modality is that of the disc degeneration which is more of a long-standing, slowly progressing, chronic degeneration process. In this process, the disc looses its strength, turgidity, water content and elasticity and ends up being a stiff inelastic and collapsed structure. In doing so it is no longer able to absorb the normal day-to-day stresses and forces.
As a result, there is more strain that is placed now on the joints of the vertebra rather than on the disc itself. This increased force on the joints of the vertebra, causes them to deteriorate rapidly which then leads to arthritis of the ‘facet joints’ of the spine. This results in not only a compression or irritation on the nerve root because of the disc, but there is also bony narrowing of the spinal canal causing the so-called classic neurogenic claudication. Neurogenic claudication is a symptom in which the patient experiences heaviness in the leg, especially the calves after walking for a certain distance. This is basically as a result of compromised blood supply to the area of the lumbar spine due to compression by thickened ligaments and inflamed joints. Once the patients rests for a few minutes, the blood supply gets restored and then the patient can continue to walk again.
This was, in short, the processes that affects our intervertebral disc. In the next column, I will discuss the various strategies of treatment and prevention for the same.
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