Spinal care should always be diagnosis-based and tissue-specific to achieve the best results. The treating doctor should identify the source of pain before recommending treatment. However, some patients experience pain more intensely than others.
Consequences of CPH: Hyperalgesia and Allodynia
Central pain sensitivity describes a physiological process whereby uninterrupted nociceptive signaling increases central nervous system sensitivity to stimuli. There are three types of nociceptors with varying degrees of function. When injured tissue continuously stimulates nociceptors, their firing threshold lowers and they fire more frequently. The continued stimulation of nociceptors magnifies and the brain receives and interprets more signals. As a result, pain feels stronger and is more easily elicited, even though the initial insult may not have worsened.
Hyperalgesia and allodynia are two manifestations of CPH. Hyperalgesia is exaggerated pain to normally painful sensations. Allodynia, on the other hand, is painful sensation caused by a non-painful stimulus; e.g., clothing touching the skin or a light touch from someone's hand or other object.
Like many ailments, early intervention and prevention remain the best treatment. Rapid pain relief is key. Diagnosing and treating the primary pain generator often provides the fastest relief. Diagnosing is an important part of this strategy because it provides a road map to efficiently addressing patient concerns.1-2
Behavior also plays a role in precipitating symptoms because pain is an emotion. The magnification of pain creates worry that something is wrong and emotional stress increases. Elevated stress contributes to an increased pain response. However, "hurt" and "harm" do not always mean the same thing. Mechanical injuries are painful, but usually are not life-threatening. The presence of pain does not necessarily mean the injury is getting worse. This concept helps reduce anxiety over pain.
For this reason, patients should become active participants in seeking strategies for pain control. This approach empowers the patient and can have a powerful psychological effect in managing pain. In contrast, when patients are mismanaged and self-help strategies fail, the continued search for relief produces anxiety and frustration or, worse still, depression. Active coping offers a better option than the alternative. Ignoring the problem addresses neither the pain nor the source. Passive coping can have a serious effect on the patient's psyche and quality of life.1-2
The Analgesic Effects of Acupuncture
Scientific literature does not support acupuncture as a first-line approach for low back pain or neck pain.3 However, a number of studies support the analgesic effect of acupuncture.4-13 Acupuncture reduces pain via two different mechanisms. One decreases the stimulation of nerve signals that lead to pain; the other reduces the expression of inflammatory chemicals that stimulate nerve endings that cause pain. Both of these mechanisms likely co-exist.
On one hand, acupuncture may physically interrupt nerve signals from nociceptors and among nearby sensory receptors that attenuate signaling to the spinal cord.4,10 This mechanism may temporarily interfere with low-level stimulation of pressure-sensitive receptors in the skin, called Merckel cells, and decrease nociceptive signals reaching the spine. New research also suggests Merckel cells may have a neuro-endocrine function that modulates pain.
Other research suggests several possible mechanisms behind the analgesic effects of acupuncture. First, acupuncture may release naturally occurring opiate-based chemicals in the body.7 The release of dynorphin, a natural opioid, may accelerate tolerance to chronic inflammatory pain.9 Second, acupuncture apparently releases serotonin in the CNS.7,10 This chemical is well-known to stimulate descending inhibitory pathways (DIP) in the brain that block pain pathways in the dorsal horn and interrupt signals before reaching the brain. Third, acupuncture may also inhibit stimulation of the sympathetic nervous system (SNS) to regulate inflammation and pain.7,11 Polymodal nociceptors influence inflammatory signaling through the SNS. Polymodal nociceptors, one of the three types of "pain" receptors mentioned previously, monitor the body's ability to maintain a homeostasis. Internal stress activates these nociceptors and the sympathetic response kicks in.
Acupuncture may inhibit neurological pathways that influence the inflammatory control of the SNS and indirectly reduce pain associated with inflammation.11 Of note, the mechanical and neurological mechanism of pain reduction achieved with acupuncture mirrors the therapeutic effect of chiropractic manipulation.
Acupuncture also appears to affect pain induced by inflammation. A great deal of literature links inflammation and pain. Inflammation is the first phase of normal healing. Unfortunately, many people linger in this stage much longer than they should and live in a chronic state of low-level inflammation. When this happens, chronic pain, disability, or CPH may develop.
New literature describes how acupuncture blocks chemical receptors that promote inflammation. For example, one study demonstrated how acupuncture counteracted increased pain associated with nerve growth factor (NGF) and Substance P at the site of injury and in the spine.6 Another study notes that acupuncture releases anandamide from inflamed tissues. Anandamide is a derivative of arachadonic acid an acts a neurotransmitter for cannabinoid receptors that inhibit nociceptive transmission.5 The hypersensitivity of tissue surrounding an injury may be partially due to disruption of the endocannabinoid system which normally acts to inhibit nociceptive transmission. Some researchers suggest Merckel cells participate in this process. Interestingly, these chemicals resemble the active ingredient in cannabis, which may partially explain its pain-reducing effect in chronic pain sufferers.
Acupuncture also seems to suppress Cox-2 in the spinal cord.8 Cox inhibitors are commonly used in NSAIDs for reducing pain associated with inflammation. Many common over-the-counter drugs including Advil, Motrin and aspirin are Cox inhibitors. Acupuncture also attenuates the effects of pro-inflammatory chemicals interleukin (IL-1) and nitric oxide (NO).12-13 Scientists continue to study the relationship between acupuncture and inflammation as an alternative to pain control.
Based on the literature, acupuncture can influence pain mechanically, neurologically, and chemically. Patient selection and diagnosis-based treatment determines the effectiveness of any course of care. Acupuncture may provide a helpful strategy for reducing pain in a particular subgroup of patients, particularly people with consistently high levels of pain who find no relief from traditional or alternative therapies. More importantly, high pain levels limit the effectiveness of manual treatment. Acupuncture may gradually desensitize nociceptors and increase patient tolerance to painful activities and/or manual treatment targeting the primary pain generator.
From a non-surgical standpoint, acupuncture provides an alternative approach for lowering pain to a tolerable level that allows treatment much in the same way that epidural steroid injections or joint blocks decrease pain sufficiently to allow aggressive manual treatment in patients whose pain limits their progress.
As a side note, if patients dislike needles, dietary changes can control pain related to inflammation. My professor once said people eat pain. Many people view diet as a luxury instead of a necessity. This mindset leads to habitually poor dietary choices that create a low-level state of chronic inflammation. All good books on nutrition touch on this painful fact.14 Lifestyle changes are priceless. Unfortunately, they are the hardest changes to make.
References
- Murphy DR, Hurwitz EL. A theoretical model for the development of a diagnosis-based clinical decision rule for the management of patients with spinal pain. BMC Musculoskeletal Disorders, 2007;8:75.
- Murphy DR, Hurwitz EL, Nelson CF. A diagnosis-based clinical decision rule for spinal pain part 2: review of the literature. Chiropractic & Osteopathy, 2008;16:7.
- Lewis K, Abdi S. Acupuncture for lower back pain: a review. Clin J Pain, January 2010;26(1):60-9.
- Silberstein M. The cutaneous intrinsic visceral afferent nervous system: a new model for acupuncture analgesia. J Theor Biol, Dec. 21, 2009;261(4):637-42.
- Chen L, et al. Endogenous anandamide and cannabinoid receptor-2 contribute to electroacupuncture analgesia in rats. J Pain, July 2009;10(7):732-9.
- Aloe L, Manni L. Low-frequency electro-acupuncture reduces the nociceptive response and the pain mediator enhancement induced by nerve growth factor. Neurosci Lett, January 2009;449(3):173-7.
- Lin JG, Chen WL. Acupuncture analgesia: a review of its mechanisms of actions. Am J Chin Med, 2008;36(4):635-45.
- Lau WK, et al. Electroacupuncture inhibits cyclooxygenase-2 up-regulation in rat spinal cord after spinal nerve ligation. Neuroscience, Aug. 13, 2008;155(2):463-8.
- Huang C, et al. Electroacupuncture effects in a rat model of complete Freund's adjuvant-induced inflammatory pain: antinociceptive effects enhanced and tolerance development accelerated. Neurochem Res, October 2008;33(10):2107-11.
- Li A, et al. Electroacupuncture suppresses hyperalgesia and spinal Fos expression by activating the descending inhibitory system. Brain Res, December 2007;1186:171-9.
- Kim HW, et al. Low-frequency electroacupuncture suppresses carrageenan-induced paw inflammation in mice via sympathetic post-ganglionic neurons, while high-frequency EA suppression is mediated by the sympathoadrenal medullary axis. Brain Res Bull, March 28, 2008;75(5):698-705.
- Garrido-Suarez BB et al. Pre-emptive anti-hyperalgesic effect of electroacupuncture in carrageenan-induced inflammation: role of nitric oxide. Brain Res Bull, Aug. 14, 2009;79(6):339-44.
- Song MJ, et al. Additive anti-hyperalgesia of electroacupuncture and intrathecal antisense oligodeoxynucleotide to interleukin-1 receptor type I on carrageenan-induced inflammatory pain in rats. Brain Res Bull, March 30, 2009;78(6):335-41.
- Example: Seaman D. Clinical Nutrition for Pain, Inflammation, and Tissue Healing. NutrAnalysis, Inc., 1998.
Dr. Marco Lopez, a graduate of Palmer College of Chiropractic Florida, completed undergraduate study (pre-med) at Boston University. He practices in the New York Metro area, including northern N.J., and can be contacted with questions and comments at www.njspinedoc.com.