Sometimes people assume that acupuncture treatment will involves putting needles where the problem is – in the knee if the problem is a painful knee, in the head to treat dizziness, and so on. But this isn’t always how it works.
The traditional Chinese understanding of acupuncture involves a fairly sophisticated system of about 360 acupuncture points distributed all over the body, from the top of the head to the sole of the foot. Many of these points have a number of functions, not all of which are obviously related to the actual location of the acupuncture point. But we can also invoke a western scientific understanding of the various effects the insertion of an acupuncture needle has to help us understand why needles go where they do - and not always in the location of the problem.
i) GENERAL EFFECTS
Our skin and muscles contain many different kinds of nerve endings or receptors, which respond to different kinds of stimulation. For instance, there are receptors which detect heat and ones that detect pressure – so that we can become aware for example of hot objects on or near our skin, or of something pressing against our skin. One of the most important kinds of nerve which seems to be involved in acupuncture treatment are called Aδ nerves (or type II/III nerves in muscles), which amongst other things convey a feeling of heaviness which will perhaps be familiar to acupuncture patients.
Once an Aδ nerve has been stimulated by an acupuncture needle entering the skin in its vicinity, information travels along the nerve to the spinal cord, and from there up towards the brain, where it can initiate a number of different subtle changes in the almost infinitely complex activity within the various parts of the brain. One of these changes involves triggering a number of ‘descending inhibitory pathways’. These refer to different pain relieving substances which are released from the brain and descend down the spinal cord (and in some cases also pass into the blood stream) to inhibit or block pain signals from any part of the body. One such substance is called β-endorphin, somewhat similar to morphine, which is released from the pituitary gland within the brain into the blood stream, and from the hypothalamus, another part of the brain, into and down the spinal cord. In other words, the needles cause the brain to trigger some of the body’s own built in pain relieving systems.
Hence acupuncture in the hands and feet, where it is usually easy to stimulate the Aδ nerves, can result in a generalised pain relief, not just in the hands and feet, but throughout the body.
Another part of the brain which is reached by the signals travelling along the Aδ nerves is the limbic system, which seems to be crucially involved in emotion. These signals tend to deactivate the limbic system and, as far as pain is concerned, this may reduce the emotional component of that pain, so that we are less bothered by it.
These kinds of effects are not thought to be particularly dependent on where the needles are placed as long as there is a reasonably strong stimulation of the Aδ nerves. (Traditional acupuncturists would demur a bit here: whilst many traditional acupuncture points are considered to trigger numerous general effects throughout the body-mind, these points are considered to be in need of precise location.)
ii) SEGMENTAL EFFECTS
But some effects of acupuncture, whilst not confined to the exact vicinity of the needle, are nevertheless particular to one section of the body. Or rather, to one segment. A segment in this context refers to that part of the body served by nerves which enter and leave the spinal cord at one particular level.
So, for instance, nerves entering and leaving the spinal cord at the level of the fifth lumbar vertebra (L5) in the lower back serve amongst other things, some of the main buttock muscles, as well as the tibialis anterior muscle just outside the shin bone and the muscle which is used to lift up the big toe; and also a band of skin running across the buttock and down the side of the leg and including the top of the foot.
Acupuncture needles inserted into points within this segment may of course trigger the kind of systemic or general effects mentioned above, but they can also have effects particular to the segment in which they lie. One of these is segmental analgesia, whereby pain which has its origin in any part of the segment is relieved by needles placed somewhere within that segment. So if we wanted to treat pain associated with the tibialis anterior muscle we could choose to place needles somewhere in the area innervated by the L5 segment - for example on the top of the foot, or in the lower back adjacent to the L5 vertebra, knowing that the pain relief we are generating will include the tibialis anterior.
One explanation for this segmental pain relief is called gate control theory. In simple terms, once the signal from an Aδ nerve stimulated by an acupuncture needle somewhere –anywhere – in the segment reaches the spinal cord at the L5 level, say, it blocks (or closes the gate to) any pain signals arriving at that level from pain transmitting nerves in the segment, so that these pain signals cannot travel up the spinal cord to the brain, and so we do not feel pain.. So, to reiterate, we can treat pain arising from a specific part of the body by identifying which segment that part lies in, and inserting acupuncture needles at a place within that segment.
Of course we might choose to use acupuncture points at or near the site of the pain, which will obviously lie in the correct segment, but sometimes that may not be possible or appropriate. In the case of a recent injury, for instance, where the tissue around the injury is painful and inflamed, we may think that it is best to avoid acupuncture in and around that painful area, but we can still have a pain killing effect by needling other points in the segment which are at a distance from the painful place.
iii) REFERRED PAIN AND TRIGGER POINTS
Referred pain is pain which is felt at some distance from the part of the body which is damaged or problematic. One type of referred pain which acupuncture is a useful treatment for is pain which is caused by trigger points, which are small knots within muscles that have become tense. The pain caused by a trigger point, either when it is pressed or when the muscle itself is stretched, is usually felt some way away from the trigger point. For instance, a trigger in the trapezius muscle in the shoulder, just to the side of the neck, commonly causes pain which radiates around the side of the head to the temple.
Trigger points can and do appear in many of the muscles in the body; fortunately the location of the pain a particular trigger point causes is fairly predictable, so that if we have reason to believe that a pain may have, at least in part, a muscular origin, we can quickly identify which muscle may be causing the pain and examine that muscle for trigger points, which are easily located by someone trained to use their hands properly. Pressing on the trigger point for a few seconds will often lead the patient to say that that is just the pain they are complaining of.
So in this case we need to treat the trigger point, not the place where the pain is; in the example above, we need to release the muscle in the shoulder, either with acupuncture of massage, so as to make the pain in the side of the head go away. Incidentally, migraine sufferers often identify the temple as the place where the throbbing, pounding pain of a migraine is felt; such people are often found to have an active trigger in the trapezius which, if not entirely responsible for the migraine, is at least part of the problem.
iv) LOCAL TREATMENT
Despite all the above, however, it is still often useful to use acupuncture points in the place where the problem is. One of the localised effects of acupuncture, for instance, is an increase in blood flow around the site of the needle. (This increased perfusion of blood is triggered once again by the Aδ nerves which cause local blood vessels to dilate.) This is often observable as a reddening of the skin around the needle, and can be useful for a number of reasons, such as the fact that it supports the body’s own healing systems, which use the blood to bring the necessary nutrients to the site. Another local effect involves the build-up of endorphins in the vicinity of the needle, peaking at around 24 hours after the treatment, which is perhaps why some of the beneficial effects of acupuncture are often felt a day or two after treatment.
Here is some of the latest news on acupuncture and related things, perhaps with a few of my thoughts thrown in for good measure.