Myelography and discography

These two investigations involve the injection of dye under X-ray control — either into the discs themselves or into the fluids surrounding the spinal cord.

Such assessments are sometimes useful for the further diagnosis of precise locations of damage to the discs -— literally the shock absorbers between the bones of the spinal column. But such investigations are, by their nature, invasive or involve penetration of body structures and the injection of dye to which some are acutely allergic. These complications, although sometimes difficult to control are not usually serious.

Many physicians prefer to do these investigations only if the patient is prepared to have surgery, because the investigations may sometimes precipitate an acute problem.

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Joe, a Construction site foreman in his mid-30s, consulted his doctor about eight years ago because he had heard that the GP had started to practice acupuncture some months previously.

Joe told the doctor that he had been experiencing severe and intractable migraine headaches for the past three years.

He was concerned that for the past six months the only form of treatment that offered relief was an injection of Pethidine, a powerful narcotic. These had started off as one injection every two weeks but had recently been given to him at the rate of three injections a week.

After taking a full history and examining him and finding that there were no apparent abnormalities, the doctor proceeded to place approximately eight acupuncture needles into various parts of Joe’s body.

The needles were left in place for half an hour, occasionally being turned by hand. They were then removed and Joe was asked to return the following week for the second treatment.

Two years later he arrived at the doctor’s surgery and said that he had thought he had better come in for a second treatment because he had recently started to have headaches!

Joe has not been seen by the doctor since then, so further comments about his history cannot be given. Although Joe’s response to acupuncture was dramatic, it is not unusual. (According to pain clinic acupuncture practitioners approximately 50 to 70 per cent of classical migraine sufferers respond in some way to acupuncture on its own or combined with medication.)

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A scale called the visual analogue scale is a straight line — either horizontal or vertical — the ends of which are fixed by a statement of the extreme limits of the sensation to be measured. For example, ‘no pain’ or ‘excruciating pain’. You can then estimate your position on this line on a particular day, or a particular moment. Thus, on

one day a score of 80 might be obtained when your pain is at its severest. Yet, on another, a very good day, you may rate your pain as low as 20.-This simple method of self-assessment can therefore give the treating physician, or therapist, a reasonably accurate means of comparing your pain over a period of weeks or months. This type of scale appears to be very sensitive to changes in pain following treatments of all kinds.

This compares well with verbal rating scales where words are chosen from a list of up to 100 or more words to describe their pain.

A pressure algometer is also used. This is a spring-loaded device which measures the pressure needed to cause pain to the person undergoing the pain experiment.

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The Gate Control Theory, suggested by Melzack and Wall in 1965, is the most accepted theory of pain today — although it still has its critics. This theory suggests that a control mechanism exists in the back horn of the butterfly-shaped spinal cord’s inner structure. It particularly applies to an area called the substantia gelatinosa — a jelly-like substance. Melzack and Wall believe that a ‘gate’ is present in this area and, when open, pain messages can pass through to the brain and make their impact.

American Professor Ronald Lawrence suggests that his students imagine two men running for the same narrow gate. The ‘fat man’ (messages travelling along the thick nerve fibres) can run much faster than the ‘thin man’ (messages travelling along thin fibres). He can get to the gate first and can thus block the gate. The thin man can pass through the open gate as do the pain messages when the gate is not blocked. But when the gate is closed, for whatever reason, the pain signal is not received by the brain and is thus effectively blocked. The gate receptors appear to be special spinal nerve cells.Thus signals travel slowly to ‘keep the gate open’ along the small uncoated nerve fibres, and the larger, coated fibres, with their rapid signals, ‘close the gate’. To better understand this, imagine you stub your toe. The pain signal travels slowly along the thin A delta fibres. By rubbing your toe, you send messages along the thicker beta fibres causing the gate to ‘close’. Thus, the pain decreases. This partially explains the effectiveness of acupuncture and TENS (Transcutaneous Electrical Nerve Stimulation), a treatment derived initially from the observation that electricity applied to the skin could have profound effects in controlling pain. The smaller fibres seem able to increase the effect of the input of sensory information into different parts of the brain. These increased signals may initiate reactive signals that descend into the spinal cord. When enough of these signals are activated, another system comes into play — the avoidance system (a reflex phenomenon), performed without thinking of pain — (rubbing your stubbed toe, wagging the finger you’ve mistakenly hit with a hammer, withdrawing your hand from a hot stove.)

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