Acupuncture and Pain Management

There is a large and expanding body of scientific evidence supporting the use of acupuncture in pain management. In the last decade, our understanding of how the brain processes acupuncture analgesia has undergone considerable development. Profound studies on neural mechanisms underlying acupuncture analgesia have evolved rapidly and predominately focus on cellular and molecular substrate and functional brain imaging. The currently understood mechanisms of acupuncture analgesia are complex and involve direct and indirect neurohumoral effects that block pain perception, reduce the pain response, relieve muscle spasms, and reduce inflammation. The analgesic mechanisms of acupuncture involve the spinal cord grey matter, hypothalamic-pituitary axis, mid-brain periaqueductal grey matter, medulla oblongata, limbic system, cerebral cortex, and autonomic nervous system. Electroacupuncture (EA) stimulation of these sites results in activation of descending pathways that inhibit pain through endogenous opioid, noradrenergic, and serotonergic systems. There are growing numbers of human trials supporting the use of acupuncture as an evidence-based practice for pain management in human medicine. There are many studies that support the efficacy of acupuncture for low back pain, neck pain, chronic idiopathic and migraine headaches, knee pain, shoulder pain, fibromyalgia, temporomandibular joint pain, and postoperative pain. Although the number of well-designed, controlled clinical research studies in veterinary medicine is lagging behind the number of studies in human medicine, much of the basic science research has been done in animals with neurophysiology that is more similar to veterinary patients than humans. Although there is research to support EA as an evidence-based practice for the control of back pain in horses, additional studies are needed in other clinical situations in veterinary medicine where pain management is required. Author’s address: PO Box 717, Clarksburg, NJ 08510-0717; e-mail: jdkenneydvm@ msn.com. © 2011 AAEP.

1. Introduction

According to the World Health Organization (WHO), the effectiveness of acupuncture analgesia has been established in controlled clinical trials, and the use of acupuncture to control chronic pain is comparable with morphine without the risk of drug dependence and other adverse side effects.¹  Acupuncture is an effective treatment for many types of pain, is welltolerated by patients, and has a minimal likelihood of serious adverse effects.^1–3  Modern and traditional acupuncture techniques have been shown to provide relief from low back pain, neck pain, chronic idiopathic or tension headaches, migraine headaches, knee pain, shoulder pain, fibromyalgia, temperomandibular joint pain, and postoperative pain.²  Acupuncture was more effective for chronic pain than placebos (sham acupuncture) based on the results of systematic reviews of pooled data from highquality randomized controlled trials.^1,3  For shortterm outcomes (less than 6 mo), acupuncture was significantly superior to sham treatments for back pain, knee pain, and headache. For longer-term outcomes (6 –12 mo), acupuncture was significantly more effective for knee pain and tension-type headache but inconsistent for back pain (one meta-analysis was positive and one meta-analysis was inconclusive).

Acupuncture can effectively treat chronic pain of the locomotor system with restricted movements of the joints, because it not only alleviates pain but also reduces the muscle spasm that causes reduced mobility.^4,5 Muscle spasm can result in abnormal loads placed on joints, often causing clinical signs of pain before changes are demonstrable on radiographs. In controlled studies of joint pain of unknown etiology, acupuncture was superior to conventional therapy, delayed-treatment controls, and several other sham acupuncture techniques. According to the WHO analysis of controlled studies, acupuncture can effectively reduce pain from cervical spondylitis and other causes of neck pain, periarthritis of the shoulder, fibromyalgia, fasciitis, epicondylitis, low back conditions, sciatica, osteoarthritis, and radicular and pseudoradicular pain syndromes.¹ In some cases, acupuncture integrated with conventional treatments was more effective than conventional treatments alone. Although acupuncture may not reduce pain to the degree that some conventional treatments reduce pain, it is associated with a low incidence of serious adverse side effects.¹ For example, acupuncture may not be as effective as corticosteroids for pain relief in some patients with rheumatoid arthritis, but chronic corticosteroid use may result in gastro-intestinal ulceration, osteopenia, muscle loss, and other adverse effects. Acupuncture not only reduces pain and inflammation but has positive effects on the immune system, which directly benefits patients with rheumatoid arthritis, and less conventional medication may be needed.¹

2. Pain Pathways and Modulation

Pain may be classified as acute or chronic, adaptive or maladaptive, and neuropathic or nociceptive, and these types of pain have different underlying mechanisms.² Neuropathic pain occurs from damage to the peripheral or central nervous system (PNS or CNS, respectively). Pain associated with activation of sensory (afferent) receptors (nociceptors) by mechanical, thermal, or chemical stimuli is considered nociceptive pain and will primarily be reviewed here. The pathways involved in nociceptive pain are also involved with the modulation of pain by acupuncture. Understanding PNS and CNS pain pathways is essential to understanding acupuncture analgesia.⁶ Terms associated with pain and pain modulation are defined in Table 1.
 

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