A Slipped Disk is a term commonly used to describe a condition involving the inter vertebral discs, which form part of the spine. The disc is a round cushion shape, and is attached across its entire upper and lower surface to the bony vertebral body above and below it.
An Inter vertebral disc is constructed of two different types of tissue. The outer layer is made up of fibrous rings of tissue and is called the Annulus, which is strong and helps to maintain its shape. The central part of the disc is called the Nucleus Pulposes and is made of a much softer, almost jelly like substance, and has the ability to flow from one side to the other within its fibrous case.
Pressure exerted through the spine causes the disc to act as a cushion and shock absorber for the bones. In a young person the disc is fairly thick in relation to the bones of the spine. As you get older the thickness decreases due to a loss of water content within the tissue itself.
Each vertebral bone is shaped on each side with an archway, which helps to form a canal through which the peripheral nerves of the spinal cord leave in order to supply specific parts of the body. This canal or neural foramen is made up of 2 halves. One part is formed by the vertebra above the disc, the other by the one below.
The thickness of the disc determines the ultimate size of the canal, if you can imagine two U's opposite each other with a gap (disc) separating them. Pressure down through the spine can be 3x more when sitting compared to standing. Lifting or carrying heavy objects can also exert extra pressure down through the spine.
During movements of bending both forwards and sideways, the nucleus moves to the opposite side to where the pressure is being exerted, allowing flexibility in the spine. It will return centrally when that movement returns back to the upright position. If during the first stage of movement, the bending causes the nucleus to flow towards the edges of the disc and cause a slight bulge at the edges, this can in turn, if repeated frequently, cause a weakening of the fibrous outer case or Annulus.
If this is happening at the same time as a twisting movement of the spine and there is a lot of pressure as in lifting, then this bulge of the annulus can become fixed for a while. This is known as a Herniation of the disc, if the bulge is stressed to its extreme, then sometimes the outer casing ruptures and the soft jelly like nucleus escape, this is called a Prolapsed disc.
When this happens it is more usual for the disc to bulge or rupture posteriorly or posterolaterally. If this happens the nerves that lie very close in the foramen are irritated either by pressure from a bulge or by foreign material from a ruptured disc. The loss of some of the disc contents reduces the thickness of the disc and so brings the two parts of the foramen or neural canal, closer together, making the canal smaller. A narrow canal means less space for the nerve to travel through.
Signs that there is disc involvement is normally pain in the area supplied by the irritated nerve. There are discs the whole length of the spine starting below the 2nd vertebra in the neck, so symptoms can occur in the head, neck, trunk, arms, low back and legs depending on which disc is affected.
The Cervical discs problems usually give rise to symptoms down the arms, and the Lumber disc problems, down the leg. It is usually one sided unless the disc has ruptured centrally. Nerve reflexes are often lost a short time after onset of symptoms, and muscle weakness can quickly follow.
Sensory disturbances apart from pain can include pins and needles, loss of feeling or numbness, or diminished sensation. Muscle spasms and their associated pain are common as the spinal muscles contract to help protect and support the spine.
Occasionally a lower spinal disc will irritate the nerves that supply the bladder and the patient finds that they cannot empty their bladder. This is a medical emergency and they should seek help immediately.
Exact diagnosis can be confirmed by M.R.I. scans or CAT scans, X-rays are helpful but do not give an accurate image, as changes in the gaps between the bones can be recent or longstanding. Treatment is always initially bed rest, remember sitting exerts 3x more pressure down through the spine then standing, so must be avoided.
Analgesics and anti-inflammatory drugs are useful. Occasionally it is necessary to surgically remove the escaped disc nucleus material and this is sometimes done as microsurgery. As recovery begins so can gentle exercise involving stretches mainly, so there is no reason why if paying attention to posture and lifting techniques in the future, that a full recovery can be made.
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