By Dr Fiona de Ferrars, Okement Surgery (part of the Wallingbrook health group) based in Okehampton Community Hospital.

Sciatica, otherwise known as a 'pain in the butt'

SCIATICA is pain in the distribution of the sciatic nerve, which supplies the skin and muscles in the buttock and at the back of the leg. It is the largest and longest nerve in the body and stretches all the way from the lower spine down to the foot.

It causes pain when it is irritated or compressed, which is usually due to a problem in the lower back. This is commonly due to a 'slipped disc'. Discs are found between the bones in the spine (vertebrae) and cushion the vertebrae from rubbing. The discs are composed of a soft centre which has the consistency of jelly, and this gel bulges out against the exterior casing. It is sometimes this bulge which presses against the sciatic nerve, and sometimes there is a rupture and then it can be the gel which causes the irritation.

However, other spinal problems such as arthritis or tight muscles can also cause sciatica. Recent research has shown that it is not only the disc gel which contains chemicals that cause irritation to the sciatic nerve, but that the chemicals are also released by other structures in the spine when they are diseased. Fortunately, the pain from chemical irritation can settle down with time.

When your GP listens to your history, they will be assessing for serious causes of back pain. These include symptoms of tumours, infection, osteoporosis, and trauma.

Sciatica often improves with exercises and stretches as these increase the distance between nerves and bones, and so reduce the pressure on the nerves.

Traditional painkillers such as ibuprofen and morphine often don't work very well on nerve pain, and so your GP is likely to suggest trying special painkillers such as amitriptyline or gabapentin. These aches rarely get better as you get older and so you will need to continue to treat by exercises and stretching in order to maintain your flexibility.

If the pain persists for more than 6 weeks despite regular physiotherapy, then your GP may consider making a referral for an appropriate assessment.

MRI scans differentiate between a compressed nerve and an irritated nerve. If a scan shows that a nerve is being compressed, and it matches where the pain is, then the GP may make a referral to the neurosurgeons, who will decide whether an operation may help. If surgery is not suitable, then there is a pain clinic which specialises in giving advice and treatment for chronic pain.

A few years ago, many spinal operations were performed. When the results were analysed, it was found that quite often just as good results or better were obtained after conservative management. So now, operations are only performed when essential.

Very rarely, sciatica can become a medical emergency if the nerves are seriously compressed. The symptoms to watch out for with all lower back and sciatic pain are:

l Problems with the bladder or bowels.

l Loss of sensation around the back passage and genitalia so that you can't feel it when you touch yourself.

l Weakness of the legs.

l Severe or progressive loss of sensation in the legs.

If any of these symptoms occur, then you must speak to a doctor at once, as you may need an urgent operation to relieve the pressure on the nerve before it is damaged forever.

Please see your own GP if you have any questions.