Neuropathic pain results from damage to, or dysfunction of, the system that normally signals pain. The International Association for the Study of Pain (IASP 2007) defines neuropathic pain as follows: ‘Pain initiated or caused by a primary lesion or dysfunction in the nervous system. Peripheral neuropathic pain occurs when the lesion or dysfunction affects the peripheral nervous system. Central pain may be retained as the term for when the lesion or dysfunction affects the central nervous system’. A review of the epidemiology of chronic pain found that there is still no accurate estimate available for the population prevalence of neuropathic pain.(Smith and Torrance 2010)
Neuropathic pain is often chronic, and can be severe and difficult to treat.(NICE 2010) The origin of neuropathic pain can be metabolic, inflammatory, infective or neoplastic, or can be due to an injury, compression or infiltration (e.g. by tumour) of peripheral nerves. Various conditions can cause neuropathic pain include diabetic neuropathy, postherpetic neuralgia and trigeminal neuralgia, pain following chemotherapy and HIV infection.
Neuropathic pain is commonly described as burning, stabbing, stinging, shooting, aching or electric shock-like in quality.(Sykes 1997; Galer 1995) The pain may superficial or deep, intermittent or constant, and can be spontaneous or be triggered by various stimuli.
Conventional management often involves the combined use of a range of pharmacological (e.g. amitriptyline, gabapentin, opioids, NSAIDs, topical treatments such as capsaicin and lidocaine) and non-drug approaches, (e.g. transcutaneous electrical nerve stimulation, psychological treatments, and specialist procedures to stimulate, block or destroy discrete areas of the nervous system.(Sykes 1997)
Galer BS. Neuropathic pain of peripheral origin: advances in pharmacologic treatment. Neurology 1995; 45 (suppl 9): S17-25.
International Association for the Study of Pain (2007). IASP Pain terminology [online]. Available: www.iasp-pain.org/AM/Template.cfm?Section=Home&Template=/CM/HTMLDisplay.cfm&ContentID=3058#Neuropathic
National Institute for Health and Clinical Excellence, 2010. CG96 Neuropathic pain - pharmacological management: full guideline [online]. Available: http://guidance.nice.org.uk/CG96/Guidance
Smith BH, Torrance N (2010) Neuropathic pain. In: Croft PR, editor. Chronic pain epidemiology: from aetiology to public health. Oxford: Oxford University Press, in press (ISBN 9780199235766)
Sykes J et al. Difficult pain problems. BMJ 1997; 315: 867-9.
How acupuncture can help
This Factsheet focuses on the evidence for acupuncture in trigeminal neuralgia, chemical-induced neuropathy and neuropathy due to HIV infection. Diabetic neuropathy is discussed in the Type 2 diabetes mellitus Factsheet. There are also Factsheets on Sciatica and Cancer. Carpal tunnel syndrome and postherpetic neuralgia will be discussed in future Factsheets.
One systematic review of randomised controlled trials comparing acupuncture with carbamazepine for trigeminal neuralgia found acupuncture to be as effective as drug treatment, but to cause fewer unwanted effects.(Liu 2010) In single randomised controlled trials, electroacupuncture was found not to be effective for chronic painful neuropathy in general (Penza 2011); acupuncture was found to be more effective than cobamamide for peripheral neuropathy due to chemotherapy (Xu 2010); acupuncture plus acupoint injection was found to be more effective than carbamazepine for greater occipital neuralgia (Pan 2008); and neither acupuncture nor amitriptyline were found to be more effective than placebo for peripheral neuropathy due to HIV infection, but acupuncture was associated with reduced attrition and mortality rates(Shlay 1998; Shiflett 2011). Other non-randomised studies have found encouraging results with acupuncture for chemotherapy-induced neuropathy, HIV/AIDs-induced neuropathy, trigeminal neuralgia and peripheral neuropathy of undefined aetiology.(Donald 2011; Schrader 2007; Phillips 2004; Galantino 1999; Spacek 1998).
In summary, acupuncture seems to be at least as beneficial as the drugs it has been tested against, though in some circumstances neither may be very effective. As yet, there is insufficient research to indicate which patient groups it may be most helpful for. Acupuncture may offer additional benefits, from better sleep to reduced mortality, and probably has fewer side effects than pharmaceutical treatment.
In general, acupuncture is believed to stimulate the nervous system and cause the release of neurochemical messenger molecules. The resulting biochemical changes influence the body's homeostatic mechanisms, thus promoting physical and emotional well-being.
Research has shown that acupuncture treatment may specifically help to relieve neuropathic pain by:
- Reducing hypersensitivity induced by spinal nerve ligation, an effect dependent on the opioid system (Cidral-Filho 2011);
- Inhibiting paclitaxel-induced allodynia/hyperalgesia through spinal opioid receptors (Meng 2011);
- Influencing the neurotrophic factor signalling system, which is important in neuropathic pain (Dong 2006).
- Acting on areas of the brain known to reduce sensitivity to pain and stress, as well as promoting relaxation and deactivating the ‘analytical’ brain, which is responsible for anxiety and worry (Hui 2010; Hui 2009);
- Increasing the release of adenosine, which has antinociceptive properties (Goldman 2010);
- Improving muscle stiffness and joint mobility by increasing local microcirculation (Komori 2009), which aids dispersal of swelling;
- Reducing inflammation, by promoting release of vascular and immunomodulatory factors (Kavoussi 2007);