Improve Treatment Outcomes by Understanding the Physiology of Acupuncture
By Mark Kestner, DC, FIAMA, CCSP, CSCS
When an acupuncture needle is inserted into the skin of a patient, what effect does the needle have on the physiology of that patient? By answering that question, it is possible to improve the clinical outcomes of acupuncture. In order to improve acupuncture's usefulness, it is important to objectively examine the effects of acupuncture stimulation. It is also beneficial to view research from the perspective of contemporary human physiology.
Although there are volumes of theoretical concepts that have been published for thousands of years from a traditional Chinese medicine (TCM) perspective, these ancient concepts do not readily contribute to a discussion of acupuncture physiology from a contemporary scientific viewpoint.
Many proponents of acupuncture tend to view the treatment through a polarized lens that transmits only their preferred concept of what "acupuncture" is. Depending upon their training and preconceived notions, acupuncture may mean different things to different providers. This series of articles takes the view that acupuncture is a very valuable treatment as it has long been practiced, and its value can be enhanced by a more comprehensive scientific understanding of how its beneficial effects are produced.
In its purest form, the term acupuncture simply means "needle puncture." Regardless of who is applying the acupuncture stimulation, the intention of the needle puncture is to produce a physiological change for the patient, such as a reduction in pain or restoration of normal homeostasis.
Although acupuncture is often used to assist the body in regulating homeostatic processes, very little modern research has been directed toward understanding that effect. Most scientific research has been undertaken to determine the mechanism of action (MOA) of acupuncture in altering pain experience.
The pain experience is the combination of noxious pain stimulation, the transmission of neurological impulses from the peripheral nerves to the spine and brain, and the interpretation of these nerve impulses that occurs within the central nervous system. Descending modulation arises from the highest levels of the cerebral cortex and can inhibit or amplify the pain experience. Interestingly, various proposals of the MOA of acupuncture needling have suggested actions involving mitigation of the pain-generating process at all levels of the nervous system.
An example of how acupuncture has been shown to affect tissue at the local level involves trigger-point acupuncture. As early as 1952, Dr. Janet Travell's now-famous work defined myofascial trigger points. Travell later observed that needle stimulation directly into a myofascial trigger point was successful at mediating pain without the use of medication.1 This observation demonstrated the concept that stimulation of tissues using acupuncture needling played a local role in the treatment of pain. The stimulation affects the local tissues in such a way as to disrupt the origination of noxious stimuli.
In 1965, Melzack and Wall proposed that nerve stimulation (including such methods as acupuncture) can negate a pain signal as it is propagated along the ascending nerve pathways by activating a functional inhibitory gate (gate theory) that restricted the transmission of the pain signal to higher neurological centers.2 In 1976, Melzack published a paper noting the remarkable correspondence (71 percent) between the location of traditional classified acupuncture points and the myofascial trigger points mapped by Travell and Simons.3 This research helped establish that the transmission of pain signals could be blocked along ascending neurological pathways by secondary nerve signals created through acupuncture stimulation.
In 1980, research published in Lancet by Clement-Jones demonstrated that beta-endorphins were released in response to electroacupuncture stimulation.4 This research established that acupuncture also acted on the central nervous system with the resulting reduction of pain. Thus, as long ago as 1980 there was evidence that acupuncture acted on the peripheral and central nervous systems, as well as inhibiting the transmission of pain signals between the two areas.
In 1989, C. Chan Gunn published a well-received book that built upon the pioneering work of Travell. While Travell had established the pain-producing effects of myofascial trigger points, Gunn stated that all myofascial pain originated from radicular sources. In his view, myofascial trigger points were the result of neural insult at the radicular level. In his treatment protocol for chronic pain, he incorporated acupuncture needling techniques traditionally used by TCM acupuncturists, although applied according to a Western physiological rationale.5
Gunn's book described intramuscular stimulation (IMS) as a procedure that used acupuncture needling techniques to accomplish predictable physiological responses. His entire approach was based upon Western medical assessment, diagnosis and treatment protocols. As he pointed out in his text, the effectiveness of his procedure, as well as that of any other acupuncture-type stimulation, is dependent upon an intact neural pathway from the area stimulated to the central nervous system.
Other studies led to findings that suggested acupuncture has multiple and varied mechanisms of action. An often-cited study in 1977 by Mayer demonstrated that acupuncture had little analgesic effect when administered in the presence of naloxone, a drug used as an antagonist to opiods, including endogenous opiod peptides such as endorphins. In that research and many replicated studies, naloxone was shown to block the analgesic effect of acupuncture needling.6
Prior to the recognition that naloxone inhibited acupuncture analgesia in the central nervous system, Chiang, et al., reported in 1973 that local anesthetic could block the acupuncture effect.7These studies indicated that the action of acupuncture depended upon a functioning neurological pathway, and that local and central nervous system functions were involved with the clinical benefit of acupuncture.
From a clinical perspective, these various research studies confirm that acupuncture's effect on pain is dependent upon neurological pathways. The research also suggests that a clearer understanding of the specifics of acupuncture stimulation would be helpful in obtaining improved outcomes. For example, is it possible that focusing on a method of acupuncture that primarily stimulates the central nervous system would produce more profound or longer-lasting benefits for the patient?
Author's note: The next article in this series will discuss a method for using this research to plan appropriate treatment for patients with acute, subacute and chronic pain. Future articles will also introduce papers and texts by other contemporary acupuncture authors including Felix Mann, Yun-tao Ma, Adrian White, Peter Baldry, Anthony Campbell, Mark Seem, Z. H. Cho, Mike Cummings, David Mayer, Gabriel Stux, Bruce Pomeranz, Ji Sheng Han and Brian Berman. When viewed together, these works illustrate how the physiological mechanisms underlying the action of acupuncture have begun to emerge. Understanding this mechanism of action will lead to greater efficacy of acupuncture treatment.
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