Prolapsed intervertebral disc

 

What is it?

The intervertebral discs are circular pads of tissue that separate the bones of the back (vertebrae). These discs consist of a jelly-like centre encapsulated in a fibrous coating and act as shock absorbers between the vertebrae to soften the pressure forces in the back especially when someone is running, bending and lifting.

A prolapse of a disc (often called a slipped disc) happens when so much pressure is put on the disc that the gelatinous centre bursts out of the coating. This protrusion may then press on one of the nerves leaving the spinal cord and running just behind the disc, causing the nerve to become numb or to send pain messages to the brain.

The most common place for a prolapsed disc to occur is in the lumbar (lower back) region although it may occur in the cervical region (neck) or, less commonly, in other places down the spine.

How does it occur?

A prolapsed disc usually occurs because a sudden increase in the pressure put on the disc causes the outer fibrous ring of the disc to rupture, allowing the jelly-like centre to burst out. This not only causes swelling and inflammation in the area of the rupture, but also often results in the gelatinous protrusion pressing on a nearby nerve causing pain, numbness and tingling along the nerve. The best known example of this is sciatica, so called because the prolapsed disc presses on the sciatic nerve that runs down the leg. The result is pain and sometimes numbness or tingling along the back of the affected leg, often reaching the outer side of the foot.

Why does it occur?

Anything that causes an increase in pressure within a disc can lead to a prolapse. This includes such activities as bending, lifting or twisting, although even coughing or sneezing can result in a prolapsed disc. Prolapse within a disc is more common in those that have already been subjected to wear and tear and it is therefore uncommon in very young people. However, elderly people are unlikely to suffer from this problem because their discs have very little jelly in the centre due to 'drying out' with age.

 

What are the symptoms?

The symptoms of a prolapsed intervertebral disc are usually a combination of pain at the site of the affected disc and symptoms resulting from pressure on a nearby nerve. For example in the case of sciatica the sufferer will usually experience pain in the lower back where the disc has burst, but will also get pain, numbness or tingling along the path of the sciatic nerve ie down the back of the leg to the outside of the foot.

If the prolapse is higher up, for example in the neck, the individual will probably suffer from neck pain and shooting pains down the shoulder or arm resulting from pressure on the nerve to that area. If the pressure is severe it may even result in weakness of the muscles served by the affected nerve.

Occasionally a bad prolapse may cause sciatica down both legs simultaneously or may even affect the nerves to the bladder causing the sufferer to become incontinent or unable to pass water or to lose control of their bowels. This is usually a serious situation and indicates that urgent medical attention should be sought.

 

How is it diagnosed?

Usually the diagnosis is made by the doctor from the history (description) of the problem given by the sufferer and from an examination which may show worsening of the pain in certain positions and sometimes a loss of reflexes in the affected limb if the arms or legs are involved. The doctor may also test the power and sensation in the affected arm or leg since these may be reduced in severe cases of a prolapsed disc.

Dependent upon the outcome of the examination the doctor may suggest additional tests such as an MRI (magnetic resonance imaging) or CT (computerised tomography) scan especially if surgery is being considered.

It is worth noting that back pain can arise as a result of referred pain from another pathology (cause) and may not necessarily be due to a prolapsed disc. This is where an MRI or CT scan can assist in the definitive diagnosis. Many people may have changes shown on a scan but remain asymptomatic.

The treatment would be based upon the severity of the symptoms and degree of neurological deficit (loss of sensation or movement).

Another test that is occasionally done is something called a myelogram where dye is injected unto the fluid around the spinal cord and a series of x-rays is then taken. This can help to indicate any areas of pressure on the nerves leaving the spinal cord or points of pressure on the cord itself. A myelogram is less commonly performed these days because of the invasive nature of the procedure, which involves placing a needle into the back.

 

What is the treatment?

About 90 per cent of people with prolapsed discs will get better without an operation. Treatment usually starts with rest and pain relief. Anti-inflammatory drugs such as Ibuprofen, muscle relaxants such as a low dose of diazepam (Valium) and painkillers are often prescribed. If this is unsuccessful the doctor may then recommend physiotherapy or osteopathy either of which can help to ease the pressure on the nerve, reduce inflammation and limit the spasm in the surrounding muscles.

Over the years the advice relating to activity or rest whilst someone has sciatica has changed. Traditionally, doctors used to advise strict rest lying in bed or on a hard surface such as the floor. However, recently studies suggest that this has no long-term benefit in the treatment of sciatica and does not speed recovery when compared with the person remaining as active as they can (within reason). In fact there is some evidence that too much rest may even be slightly harmful and delay recovery.

If the pain from the sciatica does not improve but surgery is not felt to be suitable, the patient may be referred to a so-called 'pain clinic'. This is usually run by specialist anaesthetists who are able to prescribe medication or administer special types of injection to relieve the pain.

One type of injection used is an epidural, better known for its use to dull the pain for women in labour. However, it can also be used to relieve the symptoms of sciatica. It involves a needle being inserted into a small space surrounding the spinal cord. A tube is then fed through the needle and is placed in the area where the nerves that go to make up the sciatic nerve emerge from the spinal cord. Local anaesthetic or cortisone is then injected through the tube therefore bathing the nerves in this solution. Studies have shown that in many cases this can significantly improve the pain of sciatica.

Another method of pain relief that is sometimes used in sciatica is a TENS (transcutaneous electrical nerve stimulation) machine. This works by applying small electrical pulses to an area of skin via electrodes stuck to the body in a particular region, eg the back in the case of sciatica. It reduces the pain signals sent to the brain in the same way that rubbing part of the body that has been hurt minimises the sensation of pain. Many people find it helpful for chronic pain caused by a number of different conditions.

If the pain persists, is severe, or there are signs of serious pressure on the nerve or spinal cord the individual will then be referred to a specialist. In the rare case where signs of spinal cord pressure exist such as loss of power or sensation below a particular line of the body or difficulties with bladder or bowel control, referral for emergency surgery is required urgently in order to relieve the pressure as soon as possible.

 

Surgery

Laminectomy or discectomy 

The operation for a prolapsed disc is usually a laminectomy or discectomy. Firstly, the exact disc involved is ascertained usually with a CT or an MRI scan. The patient is then given a general anaesthetic and the disc in question is exposed. The part of the disc pressing on the nerve is then removed along with any other parts of the disc that the surgeon feels may be causing problems. In many cases, most of the disc is removed. In some cases the vertebrae either side are then fused by using a bone graft made up of pieces of bone removed from the rim of the person's pelvis in the region of the hip. This provides extra stability for the part of the back or neck involved.

This type of operation is fairly common but involves major surgery requiring a long period of recovery. Initially the patient is given painkillers and is gradually mobilised with the help of physiotherapists. Numbness or weakness may persist after the operation but these symptoms should gradually improve. Damage to the spinal nerves can occur but is very unusual and unfortunately in some people the nerve pain may not get better despite surgery. Generally the patient is allowed home after about a week with instructions about gradually resuming normal activities. Lifting and bending is usually not allowed for about three months. Heavy manual work may be prohibited for even longer. Driving can usually be resumed after about four weeks.

Microdiscectomy 

In this operation, the prolapsed part of the disc is removed through a small incision in the back via an operating microscope. The advantage of this technique is that the operation is much less invasive and often the patient can be discharged the day after. However, some trials have concluded that a microdiscectomy can take longer to perform and in the long term has no advantages over the traditional so-called 'open' laminectomy.

Chemonucleosis

Some hospitals are able to shrink the bulging disc by injecting a special chemical into it under X-ray guidance. This is called chemonucleosis but it is and has been found by some researchers to be less effective than a surgical discectomy.

 

Are there any new developments in the treatment of prolapsed intervertebral disc?

Work is being done into artificial intervertebral disc replacement which means the removal of the prolapsed disc as described above but then, instead of leaving the body without a disc or alternatively fusing the two vertebrae above and below the disc, the disc is replaced with a synthetic one. This has the advantage of restoring stability and 'shock absorbing' properties to that part of the spine. This technique is still new and should be regarded as of unproven benefit.

Can prolapsed intervertebral discs be prevented?

Unfortunately it is not always possible to prevent prolapsed discs from occurring or from happening again. However, by treating one's back with respect and particularly by avoiding lifting heavy objects with a bent back (lifting should always be done with a straight back) it is possible to reduce the chances of recurrence.

 

Where can I get more information?

Apart from contacting your own GP, the following organisations may be of help:

Back Care
16 Elmtree Road
Teddington
Middlesex
TW11 8ST
Telephone: 020 8977 5474
Email: website@backcare.org.uk
Website: www.backpain.org

British Chiropractic Association
Blagrave House
17 Blagrave Street
Reading
Berkshire
RG1 1QB
Telephone: 0118 950 5950
Email: enquiries@chiropractic-uk.co.uk
Website: www.chiropractic-uk.co.uk