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How Acupuncture Works – The Science

To explain how acupuncture works in a scientific context, it will be necessary to briefly enter the world of neuroscience. This is an area of science which can be fairly complex. I always believe that simple straightforward explanations are best, so I will try to stick to that approach here.

There are five mechanisms which can be used to explain how medical acupuncture works, each can be used for a different purpose which is why anyone using medical acupuncture must be able to make a conventional medical diagnosis and have an understanding of the underlying pathology to be effective. The different mechanisms require variations in the treatment technique and so this needs to be tailored to the individual patient.

The five mechanisms are:

Local effects:

This refers to the ability of acupuncture to stimulate nerve fibres in the skin and muscle. Needling one of these nerves sets off action potentials (nerve impulses) which spread around the local network of nerve fibres – this is called an axon reflex. Various substances are released as a result including calcitonin gene related peptide (CGRP) which causes local blood vessels to dilate causing an increase in local blood flow. The blood flow is also increased in the deeper tissues which encourages tissue healing.

Summary:

Acupuncture promotes local healing in the tissues.

Segmental Analgesia:

The action potentials which have been generated by the insertion of the needle also travel along the nerve directly to its particular segment (entry point) in the spinal cord where it causes a depression in activity at the dorsal horn which reduces its response to painful stimuli. This is called the ‘segmental effect’ of acupuncture and is most likely the main mechanism by which acupuncture is able to relieve pain.

Acupuncture is capable of inhibiting pain signals arising from any structure which sends sensory nerves to that particular part (segment) of the spinal cord. A good example is pain arising from an arthritic knee. The nerves from the painful knee enter the spinal cord at the same segments in the spinal cord as the muscles around the knee. As such, by inserting needles into the muscles around the knee it is possible to inhibit pain arising from the knee itself.

Summary:

Inserting a needle into, or near a painful structure may bring about strong pain relieving effects.

Hetero-segmental analgesia:

The action potentials which having occurred due to the needle stimulating the nerve endings in the muscle and skin then travel up the spinal cord to the brainstem where they stimulate the body’s own pain suppressing mechanisms by activating the hypothalamus.

This causes the brain to release neurotransmitters which travel along nerves which descend back down the spinal cord and inhibit pain signals entering the spinal cord at every segment. In this way acupuncture can have an all over body effect in terms of relieving pain. This effect is most likely not dependant on where the needle in inserted, anywhere will do but muscles are generally a good option.

This effect is called extra- segmental analgesia and although not the most powerful, does help the overall effect of acupuncture.

Summary:

Inserting a needle anywhere in the body will bring about some pain relieving effects.

Central Regulatory effects:

Once the action potentials have passed through the mid brain, they then pass to other area of the brain. One of these is the somato-sensory cortex which processes sensory information and registers the needle sensation which is usually felt as a deep, dull, achy, numbing or tingly feeling. It is not meant to be aversively painful, if it is then the needle should be removed as it is less likely to have a therapeutic effect.

The action potentials then go on to influence other parts of the brain. One of these is the limbic system which is the emotional centre of the brain. This may explain why acupuncture has a calming effect on many patients and improves their sense of wellbeing. They become more cheerful and more motivated with a positive outlook on life. It is important to recognise that this effect may also be influenced by other aspects of the therapeutic relationship with the practitioner.

Another part of the brain which is influenced by acupuncture is the hypothalamus, otherwise known as the ‘central regulator’ due to its role in controlling a number of body functions.

As such acupuncture may, due to its effect on the hypothalamus:

  • Regulate the autonomic nervous system which controls automatic body processes such as blood vessel constriction and dilation, heart rate and blood pressure.
  • Regulate various hormones, such as those female hormones which control the menstrual cycle.

Summary:

Acupuncture has a calming effect and improves wellbeing.

Myofascial Trigger Points:

When a muscle is overworked or overloaded, put in a position of stress for a prolonged period of time, or strained due to an awkward movement it can develop a small area of injury which can be slow to heal and go on to cause persistent pain and dysfunction.

These small knots which develop within taut bands of muscle are called Myofascial Trigger Points (MTrP). These MTrP’s are not fully understood however it is essential they are identified and treated otherwise they may go on to cause persistent pain.

Unfortunately most people, including those in the medical profession view injuries to muscle as less serious and just expect them to heal. This does not always occur and it takes an experienced clinician to identify the MTrP’s and treat them effectively.

One of the simplest and most effective ways to treat these MTrP’s is to use acupuncture – when used in this way the technique is often referred to as ‘Dry Needling’

Summary: 

MTrP’s are often a cause of continued pain after an injury, it is important to identify and treat them and acupuncture/ dry needling is an effective method.

References
Campbell A. Acupuncture in practice: beyond points and meridians. Butterworth-Heineman, Oxford; 2001.
White A, Cummings M. Filshie J. An introduction to western medical acupuncture. Churchill Livingston; 2008.
Simons DG, Travell JG, Simons PT. Travell & Simons’ myofascial pain & dysfunction. The trigger point manual. Volume 1. Upper Half of Body. 2nd ed. Baltimore: Williams & Wilkins; 1999.
Baldry PE. Acupuncture, trigger points and musculoskeletal pain. 3rd ed. Edinburgh: Elsevier Churchill Livingston; 2005.
Fields H L. Pain. New York: McGraw Hill; 1987.

by Simon.


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