The traditional explanation for pain in Chinese Medicine is ‘If there is free flow, there is no pain: if there is pain, there is no free flow’. Trauma leads to inflammation, scar tissue, bruising, restriction of circulation at local or distal tissues, taut bands of muscles, impinged nerves, trigger points etc and all of these are a disruption of the normal circulation of qi and blood. Acupuncturists who work with patients, and patients who receive acupuncture may experience pain reduction, improved circulation, improved range of motion, improved mobility and for those of us who have had positive experiences, the proof of the pudding is in the eating.
However there are a number of questions bouncing around regarding ‘why that particular point there, instead of somewhere else?’ And ‘is it just placebo?’
How acupuncture might influence chronic pain through specific pain pathways is something we will consider below. How acupuncture might influence the healing of injured tissue is a question for another article.
What is pain?
If for a moment we consider the perception of pain specifically, without getting into the pathological tissue itself, we can question if acupuncture affects these pain pathways.
At the Acupuncture Research Symposium in 2013, Dr Frauke Musial explained some of the research that has identified specific pain mechanisms moderated by acupuncture, which should substantially weaken the placebo argument.
There are a number of neural pathways involved in the experience of both acute and chronic pain, from ‘bottom up’ processes ie nociception (stimulation from the periphery towards the central nervous system, excluding cognitive processes eg stubbing your toe) to ‘top down’ processes (ie ‘descending pain modulatory pathways’, from the brain towards the peripheral nervous system, such as stress, placebo, expectation eg stubbing your toe and ‘knowing’ that it is going to hurt).
It is difficult in an acupuncture clinic to separate ‘bottom up’ processes of acupuncture from ‘top down’ processes of patient expectation or even placebo. But there are some clear mechanisms influenced by acupuncture:
1. Gate control (simple explanation):
- First you have the source of original pain ie nociception (ie ‘bottom up’ peripheral stimulation, excluding complex emotional cognitive factors).
- If you add a second mechanosensitive stimulation, it results in suppression of the spinal cord neuron for a period of time.
- This corresponds to hitting your toe and rubbing on it to relieve the pain.
- When you remove the second stimulation the pain may return.
2. Diffuse noxious inhibitory Control (DNIC)
- Begin with the same nociceptive source eg a stubbed toe (although in an acupuncture clinic we are more likely to be treating something more prolonged)
- This time instead of rubbing the local sore spot, you add a further noxious stimulation distal to the nociceptive source, so for example the head, or the contralateral extremity. (Anywhere away from the site of pain, but it is very important that it is far away from the source, the further the better!)
- This pain suppression lasts longer than gate control theory (DNIC effect)
- DNIC is highly biologically significant. It involves inhibition of the somatosensory system and does not necessarily require strong stimulation.
DNIC pathway and Acupuncture
It is very interesting that in traditional acupuncture distal points are a very important part of treatment. Informed by classical theory, there is not necessarily a direct anatomical or segmental relationship, but DNIC confirms that adding a second noxious stimulation away from the site of trauma moderates pain. This is very useful in acute cases in clinic, where needling the pathological tissue might lead to aggravation of the injury.
A study by LeBars D, Willer J-C (2002) demonstrated inhibition of pain perception both from a non-acupuncture point (sham acupuncture) and a specific acupuncture point with a stronger more persistent reaction from the acupuncture point ST-36. This shows that point specificity is important, although some effect is achieved by inserting acupuncture needle anywhere in the body.
Does acupuncture induce DNIC pain inhibition?
For acupuncture to affect a DNIC response, it must be a nociceptive signal. In other words, inhibition of pain via the DNIC pathway by acupuncture is dependent upon achieving a needling sensation. Acupuncturists will talk to their patients about the deqi sensation, perceived by the patient perhaps as tingling, soreness, a dull ache, or propagated sensation away from the site of needle insertion and perceived by the acupuncture as a gentle tug or ‘grasping’ of the needle by the soft tissue into which it is inserted. It appears to be crucial to effective pain moderation.
DNIC is one of many possible mechanisms of acupuncture. It is probably more effective in acute pain than chronic pain. But it may contribute by helping ‘retrain’ DNIC in chronic pain patients. There are likely to be many other mechanisms also occurring and DNIC is just one of these.
Does acupuncture induce placebo?
The the most infamous ‘top down’ process is placebo. Placebo can be a result of positive expectations in patients due to friend referrals, a good rapport with the acupuncturist etc. It is not possible to eliminate these ‘top down’ processes in a real clinic, although clinical trials attempt to eliminate it from the procedure through things like 'sham' acupuncture or using incorrect locations, this is another area for debate. In clinic, the client should be able to trust that their practitioner is competant and willing to do his or her best to help. It is therefore probable that for some patients placebo may influence the outcome.
What does this all mean for acupuncture treatment? We have to acknowledge that pain has many processes both ‘bottom up’ and ‘top down’. It is not possible to separate these processes and influence them independently in a real clinical situation, and for the best outcome neither is it desirable. Acupuncture may induce placebo, but it doesn’t only induce placebo. As practicioners we must ensure that as far as possible we are objectively reviewing progress and measuring outcomes for example not just with pain scale references but measuring range of motion and using provocative tests. This is an area which interests me in particular and one in which I strive to improve through training and reflective practice.
It has been demonstrated that acupuncture influences specific pain pathways and there are also many other mechanisms not discussed here. A practitioner should attempt to provide the best of all these influences. Through clinical experience and knowledge of the research, by having confidence in treatment goals and acupuncture techniques, building rapport and trust with the patient, managing patient expectations and by being able to convince the patient of appropriate self-care. Acupuncture is a proven and effective therapy in the treatment of both acute and chronic pain.
To listen to Dr Frauke Musial’s fascinating lecture in full, visit the Acupuncture Research Symposium website: http://www.arrcsymposium.org.uk/watch-and-download/item/15-dr-frauke-musial.html
Le Bars D. (2002) The whole body receptive field of dorsal horn multireceptive neurones. Brain Res Brain Res Rev 40:29–44
LeBars D, Willer J-C: Pain modulation triggered by high-intensity stimulation: implication for acupuncture analgesia? International Congress Series 2002;1238:11-29.
Emma Van Loock - July 2015