Sciatic Nerve Pain from Bulging Discs

What causes sciatica?

Sciatic nerve pain is most often caused by a bulging or prolapsed disc. Have another look at the lumbar spine disc and nerve roots in the human spine anatomy section.

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These tough structures are designed to cushion and shock absorb between the vertebrae, and they do their job very well for most of us, most of the time.

• Unfortunately sometimes the centre of the disc, the nucleus, presses on a portion of the outer rings of the disc causing them to bulge outward, usually to one side or another.



• This bulging disc can cause irritation and inflammation of the sciatic nerve.



• This can lead to the characteristic sciatic nerve pain which is usually severe leg pain and sometimes symptoms of weakness, pins and needles and numbness in the leg or foot.

It is important to understand that it is not uncommon to get leg pain even if the sciatic nerve is not actually squashed or pinched. Inflammation in the area of the nerve root will cause nerve irritation and considerable sciatic nerve pain -even if the nerve is not squashed at all.

Occasionally the disc bulges very badly and the rings of the outer layer of the disc develop a fissure or crack and some of the material from inside the central, softer part of the disc leaks out. This is called a herniated disc or a prolapsed disc. This can cause inflammation and irritation of the sciatic nerve, but this can sometimes squash the nerve causing numbness, weakness and sciatic nerve pain.

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The area of the leg affected depends on which part of the sciatic nerve is irritated. Different levels in the spine cause different sciatic nerve pain patterns in the buttock and legs. This diagram gives a rough idea of the spread of the pain in relationship to the level that is irritated. The image shows a typical pattern for the 4th and 5th Lumbar level on the left and the 5th lumbar and 1st Sacral levels on the right. It is not an exact science, just a guide.

A disc can't actually slip anywhere. It is firmly attached even with the most severe of disc prolapses.

I have had so many people describe their back pain to me as a slipped disc I have lost count!

In fact , very few people really have a disc problem at all. Most have the most common type of back pain, postural or simple back pain. I don't like this term because I think its quite frightening to think that something can slip about inside your back.

I wouldn't like that idea much. It would probably make me afraid and very careful of my movements and activities in case I caused it to slip right out. In fact movement is the best thing for most types of back pain and l talk about that in the treatment section.

So, even if someone has told you that you have a slipped disc, remember your discs can't slip anywhere, although they can bulge or prolapse and cause a lot of pain.

Who gets sciatica?

Disc bulges and sciatic nerve pain usually occur in younger people, as we age our discs naturally become less hydrated and fat, they are therefore less likely to bulge

How does sciatica start?

Often it starts by lifting with a twist. Picking up a heavy object and turning with it for example. Occasionally the pain is immediate and severe but sometimes it builds up over a few hours or even days. Sometimes people develop disc bulges and sciatic nerve pain even though they haven't lifted anything.

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An important thing to know is that lots of people have disc bulges and don't know it! They are walking around out there with no pain and no symptoms. In fact some studies estimate a great many of us may have disc bulges 2, 3. This is important because you may have had a scan that found a disc bulge and you may have been told that is why you have pain. A disc bulge may be the cause of your pain, of course, but bear in mind that you may have the more common postural type of lower back pain and the disc bulge may be a red herring.

Which Investigations and tests are useful?

Plain X-rays rarely show anything useful but an MRI scan may show disc bulges and prolapses and will show if a nerve is being compressed.

Tests for the nervous system such as reflexes, sensation and muscle power can be performed by your doctor or physio and may point to sciatic nerve problems if they are abnormal.

There are also other clinical tests that your doctor of physical therapist can do, such as a straight leg raise test, which may help with diagnosis. If this test is negative its very unlikely that you have sciatic nerve pain although a positive test does not automatically mean that you have.

In practice the findings in a clinical examination are taken together with the onset, symptoms and behaviour of the problem to make a diagnosis.

References

1.Sciatica Guidelines

2.Kleinstuck-Frank, Are structural abnormalities on magnetic resonance imaging a contraindication to the successful conservative treatment of chronic non-specific low back pain?
Spine, 1 Sep 2006, vol. 31, no. 19, p. 2250-7

3.Carragee-Eugene, Alamin-Todd, Cheng-Ivan, Franklin-Thomas, van-den-Haak-Erica, Hurwitz-Eric.
Are first-time episodes of serious LBP associated with new MRI findings? The spine journal: official journal of the North American Spine Society, Nov-Dec 2006 ,vol. 6, no. 6, p. 624-35

Sciatica Causes and Management

Causes and Types of Lower Back Pain

Sciatic nerve pain -review the anatomy of the sciatic nerve .

Lower Back Pain Toolkit Home Page

July 2, 2012