Welcome back to the ThreeSpires Physiotherapy blog and our latest series of articles – this time looking at the use of acupuncture. In the last article we looked briefly at what acupuncture is, where it originated from and some of the ideas such as De-Qi and meridians. This time we take a brief look at some of the mechanisms by which acupuncture is proposed to work. I say proposed instead of “known” because this is an area of considerable research, complexity and difficulty and it is beyond the scope of this blog (and my brain power!) to analyse every single piece of neurophysiology research relating to acupuncture and come up with a conclusive answer about its mechanisms!! Simply I want to look at some of the basic mechanisms through which it is thought that acupuncture may produce a pain relieving response. I will also say that I will only be examining this from a Western medicine point of view and won’t be discussing the traditional Chinese medicine (TCM) perspective.

So... by sticking needles into someone in pain you relieve their pain?? I hear scepticism in your voice and rightly so!! Well before you decide that it can’t be true because clearly needles are sharp and will hurt let’s first have a brief look at some of the mechanisms by which this might work and my own personal take on some of these. In the next article I will examine in some detail the clinical evidence for the efficacy of acupuncture to relieve pain but today we will look at how it might work. At least this way when looking at if it works or not, we will have some perspective and insight into why it might work.

 

Well, the first mechanism that acupuncture utilises to relieve pain is the easiest to explain (the reason we are looking at it first!) but it is also probably the least potent method. It is something called descending noxious inhibitory control (DNIC) and sounds complex but is easy to relate to – basically the brain is programmed to concentrate on the area of most intense pain and will tend to block out other less intense pain stimuli (Carlsson 2002). Simply put if you have an aching pain in your back and I hit you on the foot with a lump hammer you will immediately forget about the pain in your back and concentrate on the pain in your foot (and probably get very angry!). In the case of acupuncture by putting sharp needles in someone this sensation is likely to block out the aching pain from their back and make them forget about it. Well, this doesn’t sound very good does it? At best it is likely to only have a very short lasting effect and is unlikely to offer any longer term pain relief, fortunately acupuncture has other mechanisms in its arsenal.

The next mechanism is called descending pain inhibition and is a supra-spinal mechanism like DNIC above. Sounds complicated I know but again is remarkably simple (I think neurophysiologists like to use big words to keep themselves in employment!). This effect relies upon the release of endorphins in the brain which can be triggered by a reasonably long period of acupuncture (somewhere over 30mins). These endorphins then suppress pain and give a generally feeling of well being, they are the same chemicals that are released during exercise (and other activities that are not appropriate for discussion in this blog) and give that general feeling of happiness and relaxation after exercise. Now this sounds great and it is thought that this is likely to be the strongest analgaesic acupuncture mechanism and possibly responsible for some of the long lasting pain effects of acupuncture that are often seen in patients. However, personally I am unsure about this as in a clinical setting it is not often that a patient would have the needles in situ for over 30 mins and in fact some people would suggest that the needles need to be in situ for 40 mins!

Acupuncture is also likely to have a localised effect (by dint of the fact that you are jabbing a needle there!) – needling locally is thought to stimulate the axon reflex and the release of sensory neuropeptides which induce vasodilation and increased blood flow (Bradnam 2007) which may improve tissue healing locally and reduce pain. Again this sounds complicated, but simply means that the needle triggers the release of local chemicals and an increased blood flow to the area which gives a localised pain relieving effect. This can often be seen by a general reddening of the area around and in between needles on patients and is possibly responsible for some of the benefits associated with trigger point or dry needling (we will look at this another time).

Next there are several possible effects of acupuncture at a segmental spinal level. For those reading this without a background in anatomy that simply means an effect at the same level of the spine that a nerve exits out of the spine at. For example in the low back (lumbar spine) nerves exit at each level L1-5 and then descend and provide innervations (nerve supply) to various areas. Without getting too complicated some areas in the lower limb are supplied by a particular spinal segment e.g. the sensation around the knee (roughly) is supplied by nerves from L3,4 &5. Needling can trigger the release of non-endogenous opioids such as enkephalin which block pain signals from being transmitted up the spinal cord through pre-synaptic inhibition (Zhi-Qi 2008). For acupuncture to be effective at a segmental level needles must be placed in tissues that are innervated by the appropriate spinal cord level (Bradnam 2007). Again it sounds complicated but basically if you have a lot of pain in an around the knee then placing needles at the level of L3,4&5 in the lumbar spine may trigger the release of chemicals which block any pain signals from being transmitted to the spinal cord and hence upwards to the brain. This from my experience (and I realise this isn’t hard evidence!) seems likely to be a strong effect in people that respond to acupuncture/needling as it doesn’t so heavily rely on a long time period for it to be effective and relates well to my experience of a relatively short period of needling producing dramatic results in some patients.

Another potential segmental effect revolves around the reduction of reflex activity in muscles supplied by that spinal segment and subsequent muscle relaxation. A common finding in most people with back pain for example is very hard, solid and clearly spasming lumbar paraspinal muscles – okay some of this will be caused by the person contracting the muscles themselves but some of this is likely to be caused by the triggering of reflex arcs between the muscles and the spinal cord (Bradnam 2007). A reflex arc is an automatic response by the spinal cord to trigger a muscle movement – the most well known of which is the one where you put your foot on a sharp pin and your leg and foot lift up before you even feel or register the pain in your brain. Your spinal cord did this all by itself – clever huh? This potential effect again corresponds well with my experience of how some people’s low back muscles become much more relaxed after needling and how again a short period of needling can have great results.

Finally (phew!) needling can also trigger the release of further chemicals which post synaptically inhibit the transmission of pain signals to the brain. This just means that once the signal has been transmitted chemicals restrict the onward transmission up to the brain and thus reduce the pain felt in your brain.

Okay, so a few caveats to those reading this blog post. Firstly the neurophysiology of pain is a vast and complicated area of research and I have had to summarise some very complicated and hotly debated areas for this blog. So if you are a clinician reading this, just be aware that this isn’t an attempt at a fully blown literature review, it is simply a general overview of some of the possible mechanisms of acupuncture mixed in with my own personal experiences. Secondly if you are not a clinician then please be aware that although all of the mechanisms above are plausible, unfortunately acupuncture/needling does not work in all patients nor even in the same patient all the time.

Next time we will look at the clinical evidence about the effectiveness of acupuncture – basically trying to answer the question: Does it actually work???!! I will warn you now that although I will review the evidence and try to be objective I will also mix in personal opinion and anecdotes – some people may frown upon such a thing but this isn’t a journal article and I also personally believe that evidence based medicine revolves around more than simply relying on RCTs and systematic reviews. I think here I am digressing and this is a topic for a blog on its own.

For those of you who haven't come across this blog before we are a home visit physiotherapy service operating across Lichfield and surrounding areas such as Burntwood, Whittington and Shenstone. We provide a variety of services to patients in Lichfield such as back pain relief, treatment for sciatica, post-operative rehabilitation following knee replacements, hip replacements and joint surgeries. If you live in or around Lichfield and need home visit physiotherapy then please get in touch our phone number is 0788 428 1623 and the email is enquiries@threespiresphysiotherapy.co.uk. 

References:

Bradnam, L. (2007) A proposed clinical reasoning model for Western acupuncture. Journal of the Acupuncture Association of Chartered Physiotherapists. 21-30

Carlsson, C. (2002) Acupuncture mechanisms for clinically relevant

long-term effects – reconsideration and a hypothesis. Acupuncture in Medicine 20(2-3), 82-99

Zhi-Qi, Z. (2008). Neural mechanism underlying acupuncture analgesia. Progress in Neurobiology, 85: 355–375