Medicine

Useful chinks in the bamboo curtain

John Link later

When news of the Chinese technique of acupuncture analgesia reached the medical press, it was received with varying shades of disbelief. Acupuncture is a 2,000 year old form of folk medicine, in which needles are inserted into mystical positions and planes to cure disease. Sophisticated commentators thus dismissed it with scorn, recalling that in 1950 Mao Tse-tung had issued a directive for integrating ancient Chinese medical lore with modern medical teaching. The new acupuncture, however, has nothing to do with the old folk medicine. It depends upon prolonged stimulation, by vibrating needle or by rhythmical massage, of certain key points on the body. This eventually induces analgesia in other areas principally in the same spinal segment.

In recent years the technique has been greatly improved as the result of a massive research project. Acupuncture is now successful in 90 per cent of cases, principally those on the thorax and front of the neck. Patients are usually prepared, for a few days beforehand, to exclude those who are too nervous to remain awake during a major operation. The surgeon sometimes employs local injections of lignocaine on the lines of incision. An orthodox anaesthetist always stands by to ta.ke hver in rase of failure.

A resume of Chinese research has now been published by Professor Chang Hsiang Tung, of the physiological research centre at Shanghai, and the surprising thing is that there is still no entirely satisfactory Chinese explanation of acupuncture. The technique is still entirely pragmatic. I therefore propose to line up some of theprincipal facts that have been established, and submit a hypothesis.

The most effective acupuncture points coincide with body positions in which either muscle spindles or tendon stretch receptors are situated. These spindles are fine chains of minute separately innervated muscles located within the main skeletal muscles of the body. They function like a servo mechanism to keep the main muscles at the length at which they are set by voluntary effort and also they maintain posture. The nerve fibres leading from each spindle along the spinal cord to the brain are most active when the main muscle is under greatest tension.

It follows that rhythmical and vigorous massage of the spindle areas when the body is relaxed will flood the central nervous system with bursts of unnecessary, unfelt impulses which will gradually tend to block other messages travelling by similar routes. Analgesia thus produced is most effective within the same spinal segment.

This process of blocking one sensory input by means of another is well established. Every general practitioner knows that by rubbing an infant's forehead briskly while the nurse injects its bottom, he will usually succeed in eliciting a chuckle instead of a wail. This demonstrates that one painless, but brisk and surprising, sensory input has blocked the arrival of trivial pain from another area.

In addition to one sensory input blocking another, the brain can, actively and selectively, itself block sensory input by means of nerve fibres that descend from the grey matter of the cortex to the relay stations or nuclei by which sensory input travels upwards to the brain. This is another way of saying that we do not actually hear the distant sound of waves on the shore when we are intently watching a nearby, interesting object. Similarly, when we are considering some inner problem deeply, we tend to block, or inhibit, all sensory input: we are then said to be pre-occupied.

If the brain did not have this capacity selectively to cootrol different nerve impulses, we could never pay attention to anything at all. We should be in the ridiculous position of a commander-in-chief, all of whose subordinates were continually reading their situation reports to him simultaneously at the tops of their voices.

Severe pain is in a separate category. It carries an urgent message and breaks through any inhibitory block unless the inhibition is very strong as, for example, in battle when a soldier scarcely notices what would otherwise be a painful wound until the battle is over.

If one considers this, both' teleologically and phylogenetically, it becomes evident that conditions under which our ancestors found pain to be, not only a useless sensation, but indeed a positive embarrassment, are precisely those conditions in which muscle spindle activity is highest. It .should not, therefore, be surprising that analgesia can be induced by triggering these spindles by means of acupuncture.

The Chinese produce, as evidence that the muscle spindle theory is incomplete, the fact that the external ear forms a good acupuncture site for pain in all positions on the body surface, not necessarily from the same segment.

I feel that the Chinese have not done their homework properly because it was known at least twelve years ago, in a different experimental context, that stimulation of the ear alters the length of muscle spindles all over the body. Apart from this, the ears that our ancestors could waggle when listening for an enemy, were certainly linked with posture and with muscle spindles.

The auditory part of the inner ear is derived from the lateral line organ of our still more distant fishy forefathers. This organ extended down to their tails and enabled them to maintain posture in turbulent water, by registering water pressure at each spinal segment.

These are therefore three reasons to suggest that the diffuse effect of the ear as an acupuncture site is confirmation rather than contradiction, of the muscle spindle explanation.

In addition there are nerve fibres connecting the muscle spindles with the reticular formation, an area of the brain stem which controls arousal and sleep. Sleep is caused primarily by blocking sensory input.

If I had to bet, I would put my money on the reticular formation as the site of a slow build-up on inhibition that ultimately blocks pain from the operation site, and research further into all its nerve connections. Even the time course of the phenomenon suggests a process of going to sleep. Most reflexes are measured in milliseconds, whereas acupuncture analgesia takes five to fifteen minutes to develop.