Auricular acupuncture for the treatment of pain

Taras Usichenko,MD,

Department of Anaesthesiology and Intensive Care Medicine, University of Greifswald, Germany.

Auricular acupuncture (AA) represents an excellent model to be tested, using the research methodology of Randomised Controlled Trials (RCT). The assumption of a somatotopic representation of the entire human body on the external auricle allows the easy application of necessary RCT attributes (blinding, invasive or non-invasive control conditions) in acupuncture research (1). In the last decade, this methodological phenomenon facilitated the performance of an array of RCT on the clinical effectiveness of AA for conditions mainly affecting the central nervous system (2,3). The most common described clinical application of AA is the treatment of acute and chronic pain (4,5). Two recent systematic reviews of studies evaluating AA for pain treatment suggested that AA may be effective for the treatment of a variety of types of pain, especially postoperative pain (5,6). These clinical analgesic effects of AA can be explained using the neurophysiological model. The auricle receives the overlapping innervation of the cranial (trigeminal and vagal) and spinal C1–C3 nerves (7). The afferent ﬁbres of the auricular branch of the vagal nerve terminate in the solitary and spinal trigeminal nuclei, which are involved in the transmission and processing of pain. In animal model, vagal stimulation, which produced analgesia, was mediated via the nucleus tractus solitarii and involved the system of endogenous opioids (11,12). In chronic pain patients AA, applied for treatment of pain, was associated with increased beta-endorphine in cerebral fluid (13). There is evidence that stimulation of central regions of the external auricle produces analgesic effects, supported with the biologic mechanism of these effects.

References:

1. Usichenko et al. The effect of auricular acupuncture on anaesthesia: a search for optimal design. Anaesthesia 2003;58:928–9.

2. White AR, Moody RC. The effects of auricular acupuncture on smoking cessation may not depend on the point chosen - an exploratory meta-analysis. Acupunct Med 2007; 24: 149-56.

3. Chen et al. Auricular acupuncture treatment for insomnia: a systematic review. J Altern Complement Med 2007; 13: 669-76.

4. Asher et al. Auriculotherapy for Pain Management: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Altern Complement Med 2010; 16: 1097-1118.

5. Alimi et al. Analgesic effect of auricular acupuncture for cancer pain: A randomized, blinded, controlled trial. J Clin Oncol 2003; 21: 4120-6.

6. Usichenko et al. Auricular acupuncture for postoperative pain control: a systematic review of randomised clinical trials. Anaesthesia 2008;63 (in press).

7. Peuker ET, Filler TJ. The nerve supply of the human auricle. Clin Anat 2002; 15: 35-7.

8. Randich et al. Characterization of antinociception produced by glutamate microinjection in the nucleus tractus solitarius and the nucleus reticularis ventralis. J Neurosci 1988;8:4675–4684.

9. Aicher SA, Randich A. Effects of intrathecal antagonists on the antinociception, hypotension, and bradycardia produced by intravenous administration of [D-Ala2]-methionine enkephalinamide (DALA) in the rat. Pharmacol Biochem Behav 1988;30:65–72.

10. Clement-Jones et al. Increased beta- endorphin but not met-enkephalin levels in human cerebrospinal fluid after acupuncture for recurrent pain. Lancet 1980;2:946-9.