There is no obvious connection between a decerebrate frog and Her Majesty the Queen, except in my mind and perhaps in the minds of doctors who studied medicine at Oxford half a century ago.

Whenever I am told that someone is crippled by a spasm of muscles in their back, I remember one of the first experiments we did as students. This involved connecting the nerve from a debrained frog’s spine to its legs and then passing an electric current along the nerve. The relationship between the current and the strength of the spasm in the muscles of the frog’s leg was then measured.

Whatever the patient may think of muscle spasm as a diagnosis, in reality it is not a satisfactory one — and incomplete unless it also takes into account the cause of the symptoms.

Anyone who has suffered from disabling backache, or looked after those who have, knows the difficulties that the pain can cause. Everything that involves movement becomes an ordeal, and the pain when turning over in bed can exacerbate these difficulties by causing restless, or even sleepless, nights.

In medical practice, the diagnostic destitute often take refuge in summarising the patients’ symptoms in a single descriptive phrase and handing it back as if it is an explanation for their troubles. Tonsillitis, for example, is not a disease but a symptom. It is a way of describing, in archaic terms, inflammation of the tonsils. What both patients and doctors need to know is why the tonsils have become inflamed and the organism that has caused this.

Another example is sciatica — the technical description for the pain and spasm in the lower back that radiates down the sciatic nerve into the buttocks and lower limbs. But like the term tonsillitis, it merely sums up the account the patient has already given the doctor. What is necessary, and what is expected of the doctor, is an explanation of the factors that caused the nerve irritation that has led to this.

Whatever the factor was, it is the equivalent to the electric shock that caused the luckless decerebrate Oxford frogs’ legs to go into spasm when their sciatic nerves were stimulated all those years ago.

A survey has shown that of 2,100 randomly selected adults, 870 had suffered from severe back pain in the previous two years. Interestingly, nearly a third of the sufferers were keen gardeners.

The most common cause of severe and sudden spasm of muscles in the lower back, with pain radiating into the buttocks and lower limbs, is a herniated intervertebral disc – a slipped disc — or degenerative changes as a result of osteoarthritis of the spinal joints.

The prolapsed disc presses on and irritates the nerve roots, or root, as they leave the spinal cord. This produces pain in the part of the body supplied by these nerve roots. So commonly do prolapsed intervertebral discs give rise to back pain, that in adults it is justifiable to wait three weeks (and recently a cost-conscious NHS suggested six weeks) before a persistent pain is investigated more carefully. The best means of investigation is an MRI scan.

If it appears that the nerve roots are not being irritated by pressure from a disc or osteoarthritis, or from pressure on the spinal cord itself from the disc, and that the condition stems from trouble in the vertebral bone, the latest smart investigation is a CT/PET scan. This will demonstrate the nature of any trouble within the bone. Straight X-rays are less helpful.

The initial treatment while waiting to see if backache settles is to resume everyday activities — but with nothing that is too energetic — after two days of rest.

TOPIC OF THE WEEK

Send your queries on backache to Dr Stuttaford here. His answers will appear online at 1pm on Wednesday, November 8.