Acupuncture points – do they really exist??

The question of the existence of acupuncture points and their anatomical-physiological basis has been studied in various ways :

1. By comparing the effects of needling real points against pseudoacupuncture at non-acupuncture points.
2. By searching for specific anatomical structures on acupuncture points.
3. By examining the electrophysiological properties of the skin at acupuncture points.
4. By examining the nerves that are activated by acupuncture.

Needling at acupuncture points leads to better results than at non-acupuncture points?

Various investigators have shown for acute, experimentally produced pain in human subjects that needling at proper acupuncture points produces pronounced analgesia, whereas treatment at placebo points produces only very weak effects [16 e, 22, 179].

The results were unequivocal, as the effect of stimulating pseudo-points was practically non-existent in experimentally induced acute pain (correspondingly, placebo tablets have little effect in acute pain, causing analgesia only in 3% of cases). In contrast to these very clear results, the studies on patients with chronic pain were less clear-cut.

Placebo anesthesia has a significant effect in chronic pain conditions, working in 30–35% of patients. Needle treatment on non-acupuncture points seems to work in as many as 33–50% of patients, while real points are effective in 55–85% of cases [197].

Statistical significance of differences between acupuncture and pseudoacupuncture

To work out the statistical significance of these differences between acupuncture and pseudoacupuncture would require large numbers of patients — at least 122 per study — and such studies have not yet been performed [197]. It is somewhat perplexing that pseudoacupuncture is effective in 33–35% of patients with chronic pain, while it is virtually ineffective for acute, laboratory-induced pain.

Because of these problems, the specificity of acupuncture points has only been demonstrated in studies of subjects with acute pain and has yet to be conclusively studied for chronic pain conditions, where the number of patients involved has never reached the required 122.

Verum acupuncture in animals

In animal studies with mice [149], cats [19, 56], horses [35], rats [182, 188], and rabbits [55, 99], many investigators have shown that verum acupuncture works better than placebo needling for acute pain conditions. These findings are in agreement with research on acute pain in humans.

It is important in such animal experiments to apply mild stimulation in the awake animal to rule out stress-induced analgesia; strong stimulation even at pseudo-points can induce stress analgesia [144]. Stress analgesia is a well-documented phenomenon [108] and is endorphin-mediated. When the applied stimulation is very strong, the stress becomes very large under both real and pseudoacupuncture.

In contrast, in studies under anesthesia, problems from psychogenic stress are reduced [19, 55, 56, 137, 147, 148, 150, 152, 153, 188].

Thus, many studies on acute pain in animals and humans show in no uncertain terms that AA (acupuncture analgesia) using proper acupuncture points works far better than AA using pseudo points. However, further studies on chronic pain are needed to see if the true points are more effective than arbitrary points here as well.

Acupuncture points – Are there specific anatomical structures?

Although various histological studies of the skin and subcutaneous structures at acupuncture points have been performed, no specific structures have been found. However, several authors [62, 123] have made the astute observation that the majority of acupuncture points coincide with „trigger points“: for instance, Melzack et al. found that 71% of acupuncture points correspond to trigger points [123].

This suggests that the needles activate sensory nerves emanating from muscles. This in turn is consistent with findings that stimulation of muscle afferents is important in producing analgesia [37, 104, 201]. Travell’s research on trigger points, beginning in 1952 [190] and culminating in an extensive book in 1983 [191], shows that there are small, hypersensitive districts in the myofascial structures which, when palpated or pressed, produce a larger painful area in an adjacent or even distant (corresponding) area.

She found that „dry pricking“ of these trigger points with hypodermic needles — i.e., pricking, without the injection of a drug — produced pain relief. When skin sites are sensitive to pressure, the Chinese call them Ah-Shi points, and recommend needling them.

In a recent review of the anatomy of acupuncture points, Dung [47] enumerates ten structures found in the vicinity of acupoints (with 5, 6, and 9 in particular being associated with trigger points). With decreasing importance he names:

1. Larger peripheral nerves. The larger the nerve, the better.
2. nerves that originate from a deeper localization and come more to the surface in their course.
3. Cutaneous nerves arising from deep fasciae.
4. Nerves emerging from bone foramina.
5. Motor points at neuromuscular junctions: these are the points where the nerves enter the muscle mass. They are not always identical with the location of the actual synaptic connection, the neuromuscular endplate, which may be located a few centimeters further into the muscle after the nerve has branched into smaller branches. The pathophysiological significance of these neuromuscular junctions is not known.
6. Blood vessels in the neighborhood of neuromuscular junction sites.
7. Nerves composed of fibers of different thicknesses. This is more often the case with muscular nerves than with cutaneous nerves.
8. Branch points of peripheral nerves.
9. Tendons and ligaments, joint capsules, fascia sheets, collateral ligaments, as these structures are rich in nerve endings.
10. Bone sutures of the skull.

From this list it is clear that there is no specific structure that would be found dominating at acupuncture points. The most important correlate is probably the presence of nerves, whether larger bundles (item 1–8 of the list) or nerve endings (item 9 u. 10). According to a recent publication by Heine, 80% of acupuncture points are said to correlate with perforations in the superficial fascia of cadavers.

Cutaneous vascular nerve bundles pass through these holes to the skin. If these findings can be reproduced, they could provide a morphologic basis for acupuncture points [75 a]. The suppression of the AA effect by injecting local anesthetics into the acupuncture point before starting the stimulation [37, 151] is strong evidence that nerves are important for this phenomenon.

However, one should not hastily rule out the possibility that acupuncture effects other than anesthesia — for example, the immunological-anti-allergic effects of acupuncture — may underlie quite different mechanisms. One can speculate on the possible release of arachidonic acid from the membranes injured during needling, which in turn brings on leukotrienes and prostaglandins that affect immunity.

Also, chemoelectrical influences due to tissue injury could be important for nerve regeneration. Do local anesthetics block all other acupuncture effects as well as the AA? This should be easy to answer, but so far the non-analgesic acupuncture effects have been relatively little studied.

Author: Prof. Bruce Pomeranz
University of Toronto
25, Harbord Street
Toronto, Canada

From: Stux, Stiller, Pomeranz (1999): Acupuncture – Textbook and Atlas, Chapter 2, 5. [75 a] 3rd edition, Springer Verlag, Berlin Heidelberg New York