Neurophysiological Mechanisms of Acupuncture
To the age-old question “Where should the needle be placed, and how should it be stimulated for maximum benefit?” there is no one, single answer—it depends on what mechanism needs to be activated and what desired physiological outcome is determined. In this chapter we will look at five mechanisms: local, spinal segmental, endogenous opioid circuit, CNS, and neuromuscular.
1. Local mechanism
What is going on at the focal point of the acupuncture needle at the time of insertion and stimulation?
Why is it that when an acupuncture needle alone is inserted, incredible healing occurs locally? In Korea, a protocol has been introduced in which acupuncture needles are inserted all around the border and directly into second- and third-degree burns. This leads to incredible faster healing of the burn and much less scarring, if any, and results in little to no post-pathological neuropathy. I have utilized this theory style with tremendous success in the treatment of burns, post-op, stubborn, non-healing incisions, and skin infections. And why has simply inserting acupuncture needles directly into the plantar fascia resulted in the resolution of plantar fasciitis? How about needling around or directly into affected areas of slow-healing traumatic injuries?
At the site of the insertion, the special design of the needle (microscopically round, filiform, sterile, etc.) and the insertion technique produce a unique, healing, biochemical soup. The body’s complex reaction to the simple insertion of an acupuncture needle is really quite remarkable. The instant an acupuncture needle is inserted, and then stimulated, an “axon reflex” occurs throughout the meshwork of surrounding nerves. This reflex results in the stimulation of specific fibers located in the terminal network of the primary nociceptive afferent A-delta fibers (including A-gamma and sometimes A-beta) and II and III muscle fibers. This in turn triggers the release of the CGRP (see Chapter 2), one of the body’s most powerful vasodilators. This in turn dilates the surrounding local capillaries and leads to the release of other powerful neuropeptides. Locally, neuropeptides are released as a result of this local neuro-tissue stimulus. These chemicals have several specific therapeutic effects on the local tissues. It has been discovered that this local neurochemical accumulation consists of prostaglandins, red and white blood cells, glutamate, other excitatory amino acids, Substance P, and even serotonin from the local mast cells. This chemical soup begins to down-regulate the pain cascade, aids in reducing inflammation, starts the healing process of local and surrounding tissues, fights infections, and increases local circulation (Filshie & White, 1998; Marieb & Hoehn, 2009; White et al., 2008).
There is an interesting technique I have learned and used called “osteopuncture.” In this technique, you gently needle directly into accessible periosteum. This is a wonderful technique that directs that chemical soup to the bone level to treat such conditions as arthritis, stubborn fractures, ligament injuries, and shin splints. You do not needle deeply into the bone, just superficially into the periosteum or attaching ligament. The local chemical soup that is produced helps to heal bone injuries and ligament inflammatory injuries.
What is actually happening when a De Qi sensation has been obtained locally?
When a De Qi sensation has been achieved, we are certain that, based on the type of sensation the patient reports, we can determine which specific afferent sensory nerves have been stimulated. Those neuropeptides that are released locally (mentioned above) are what stimulate the afferent fibers and result in the De Qi sensation. Different needle stimulation techniques result in different sensations due to different neuropeptides being released as a result of the technique employed. The different techniques also have an effect on the amount of chemicals released (stronger techniques yield more). Hence different sensations lead to the stimulation of different afferent fibers and different outcomes. In other words, the local cutaneous afferent nerve fibers when stimulated elicit a specific sensation and reaction referred to as “axon reflex,” which results with the initial stimulation of the “acupoint.”
When we are training, our teachers constantly remind us, as do the TCM classics, of the importance of the De Qi sensation. For either the patient or we the practitioners feeling “the Qi gripping the needle,” De Qi is important for the outcome of the treatment. We can now explain through neurochemistry what our patients are feeling, as described above, and it is an interesting fact that under electro-microscopic imaging a sterile, disposable, microscopically round acupuncture needle has been shown to grasp and wrap tiny nerve fibers (A-delta) around its shaft during rotation techniques, explaining why practitioners feel the “Qi grasping” the needle.
Needling is effective when one obtains De Qi. (Ling Shu, Chapter 3)
Needling is effective when Qi arrives. (Ling Shu, Chapter 1)
When the patient inhales, twist the needle to get De Qi. (Su Wen, Chapter 2)
Throughout my researching and reviewing of clinical trials on the efficacy of acupuncture in scientific environments, I have found that the more concrete findings, highest success rates, and consistent reproducible outcomes are achieved when the patient obtains a De Qi sensation. I have read in so many texts: “The needle was stimulated until a De Qi sensation was obtained.” So, seeing that pattern and putting it into clinical practice and theory, we find a systematic approach to yield better outcomes.
The acupuncture needle can be inserted utilizing traditional hand insertion or guide-tube insertion. In either event, the needle after insertion should be stimulated until the patient feels a De Qi sensation. Remember, this should be a comfortable Qi sensation, not a sharp or stabbing/burning/painful sensation. A dull, achy, warm, heavy, distended, traveling, fullness sensation, or even a small muscle fasciculation, is fine. (Also, keep in mind that certain medications can amplify pain, such as with hyperalgesia.) As explained above, those classical sensations are the peripheral afferent nerve fibers firing and eventually hitting their mark: the brain and specific receptors. For a patient to feel those sensations, or any sensation for that matter, the afferent fibers of the A-delta, II and III muscle fibers, or C-fibers must have been stimulated (see Chapter 1 for the neuro-breakdown of De Qi sensations).
Light touch, pressure, vibration
Deep pressure, heaviness in muscle, pinprick in skin, cold
Soreness, aching, itching, heat, calmness, second burning pain