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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, people experience pain differently and some patients experience pain more intensely than others.  These individuals may be predisposed to developing chronic pain and disability.  If the initial pain experience is very high and continues this way without reduction central pain hypersensitivity may develop.  Rapidly deceasing pain after an injury or acute episode prevents the development of chronic pain, disability and central pain hypersensitivity.

Central pain hypersensitivity describes a physiological process whereby uninterrupted painful stimulus increases the nervous system’s sensitivity incoming signals.  Nerve receptors that respond to various sorts of tissue damage are called nociceptors.  There are three types of nociceptors with varying degrees of function.  When injured tissue repetitively stimulates nociceptors, their firing threshold lowers, they fire more frequently and with less stimulus.   The continued stimulation of nociceptors magnifies and the brain receives more signals.  As a result, pain feels stronger and is more easily elicited even though the initial insult may not have worsened.

Two manifestations of central pain hypersensitivity include hyperalgesia or allodynia.  Hyperalgesia denotes exaggerated pain to normally painful sensations.  Allodynia, on the other hand, represents painful sensation caused by non-painful stimulus, e.g., clothing touching the skin, light touch.

Early intervention and prevention remains the best safeguard against central pain hypersensitivity.  Rapid pain relief is key.  Diagnosing and treating the source of pain often provides the fastest relief.  Diagnosing is an important part of this strategy because it provides a road map to effective and timely results.

In addition to diagnosis based treatment, 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.  As a result, the elevated stress contributes to an increased pain response.  However, “hurt” and “harm” do not always mean the same thing.  Most mechanical injuries are painful.  However, they usually are not life threatening.  The presence of pain does not necessarily mean the injury is getting worse.  This concept helps prevent anxiety over pain.  For this reason, patients should also actively seek strategies to manage their pain.  This approach empowers the patient and can have a powerful psychological effect in controlling pain.  However, when patients are mismanaged and self-help strategies fail, the continued search for relief produces anxiety and frustration or, worse still, depression.   Overall, active coping offers a better option than the alternative.  Ignoring the problem neither addresses the pain nor the source.  Passive coping can have a serious effect on the patients psyche and quality of life (1, 2).

According to research, acupuncture is not the best approach for low back pain or neck pain (3).  However, several studies support the pain reducing effects 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, scientists believe that acupuncture physically interrupts nerve signals from pain fibers, and among nearby pressure receptors, that attenuate signaling to the spinal cord (4, 10).  This mechanism of action may temporarily interfere with low level stimulation of pressure sensitive receptors in the skin, called merckel cells, and decrease pain signals reaching the spine.  This study supports others that suggest merckel cells participate in pain modulation.  Another author suggests a review of possible explanations for the pain reducing effects of acupuncture.   For example, Acupuncture is thought to release opiate-based chemicals which exert a pain reducing effect much like morphine (7).  The release of dynorphin, a natural opioid, may accelerate tolerance to chronic inflammatory pain (9).  Acupuncture also seems to release serotonin in the central nervous system (7, 10).  This chemical is well known to stimulate centers in the brain that ultimately block pain pathways starting in the spinal cord.  This action interrupts pain signals before reaching the brain.  Third, acupuncture may inhibit a group of nerves in the sympathetic nervous system that regulate inflammation and pain (7, 11).  The sympathetic response–typically known as the flight or fright response–kicks in when we experience stress.  Polymodal nociceptors—one of the three types of “pain” receptors mentioned earlier– monitor the body’s ability to maintain a stable internal environment.  So polymodal nociceptors monitor internal stress and influence inflammatory signaling through the sympathetic nervous system.  Less inflammation reduces pain (11).  Of note, the mechanical and neurological mechanism of pain reduction in acupuncture mirrors the therapeutic effect of chiropractic manipulation.

In addition to the mechanical and neurological blocking of pain, acupuncture appears to affect pain induced by chemical inflammation.  A surplus of literature link inflammation and pain.  Inflammation is not bad because it is the first phase of normal healing.   The problem arises when healing remains or lingers in this stage much longer than it should.  When this happens, chronic pain, disability, or central pain hypersensitivity may develop.

Acupuncture blocks chemical receptors that promote inflammation.  For example, one study demonstrated how acupuncture counteracted increased pain associated with nerve growth factor 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 chemical that binds to and activates cannabinoid receptors that block pain transmission and results in pain reduction (5).  The hypersensitivity of tissue surrounding an injury may be partially due to disruption of the endocannabinoid system which normally acts to inhibit nerve transmission.  This system may be linked to merckel cells (mentioned earlier) and pain modulation.  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 for reducing pain associated with inflammation.  Many common over the counter drugs such as Advil, Motrin, or Aspirin are cox inhibitors.  Acupuncture also attenuates the affects of pro-inflammatory chemicals that have a long association with pain:  interleukin and nitric oxide (12, 13).   Scientists continue to study the relationship between acupuncture and inflammation as an alternative to pain reduction.

Based on the literature, acupuncture can influence pain mechanically, neurologically, and chemically.  Patient selection and diagnosis-based treatment determines the effectiveness of any treatment.  Acupuncture may provide a helpful strategy for reducing pain in a particular sub-group of patients.  People with consistently high levels of pain that find no relief from traditional or alternative therapies may benefit from acupuncture.  More importantly, high pain levels limit the effectiveness of manual treatment. Acupuncture may provide gradual exposure that helps de-sensitize pain receptors and increases patient tolerance to painful activities and/or manual treatment that targets the source of pain.  From a non-surgical standpoint, acupuncture provides an alternative approach for lowering pain to a tolerable level that allows treatment in the same way that epidural steroid injections or joint blocks decrease pain to allow aggressive manual treatment in patients minimally responsive to a trial of conservative care.

As a side note, if you 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 greater pain response through a low level state of chronic inflammation.  All good books on nutrition touch on this painful fact.  For this reason, a diet high in fruits and vegetables with moderate levels of carbohydrates and meats; miniscule quantities of refined grains, sugars, and other processed food products ultimately decrease pain and promote rapid healing (14).  Lifestyle changes have the greatest impact on health.  Unfortunately, they are the hardest changes to make.

References:

  1. 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
  2. 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
  3. Lewis K, Abdi S.  Acupuncture for lower back pain: a review. Clin J Pain. Jan;26(1):60-9.
  4. Silberstein M.  The cutaneous intrinsic visceral afferent nervous system: A new model for acupuncture analgesia.  J Theor Biol. 2009 Sep 16.
  5. Chen L, et al.  Endogenous anandamide and cannabinoid receptor-2 contribute to electroacupuncture analgesia in rats.  J Pain. 2009 Jul;10(7):732-9. Epub 2009 May 5
  6. Aloe L, Manni L.  Low-frequency electro-acupuncture reduces the nociceptive response and the pain mediator enhancement induced by nerve growth factor.   Neurosci Lett. 2009 Jan 16;449(3):173-7. Epub 2008 Nov 7
  7. Lin JG, Chen WL.  Acupuncture analgesia: a review of its mechanisms of actions.  Am J Chin Med. 2008;36(4):635-45.
  8. Lau WK, et al.  Electroacupuncture inhibits cyclooxygenase-2 up-regulation in rat spinal cord after spinal nerve ligation.  Neuroscience. 2008 Aug 13;155(2):463-8. Epub 2008 Jun 14.
  9. 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. 2008 Oct;33(10):2107-11. Epub 2008 May 7.
  10. Li A, et al.  Electroacupuncture suppresses hyperalgesia and spinal Fos expression by activating the descending inhibitory system.  Brain Res. 2007 Dec;1186:171-9. Epub 2007 Oct 22.
  11. Kim HW, etal.  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. 2008 Mar 28;75(5):698-705. Epub 2007 Dec 26.
  12. Garrido-Suárez BB et al. Pre-emptive anti-hyperalgesic effect of electroacupuncture in carrageenan-induced inflammation: role of nitric oxide.Brain Res Bull. 2009 Aug 14;79(6):339-44. Epub 2009 May 3
  13. 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. 2009 Mar 30;78(6):335-41. Epub 2008 Nov 18
  14. Seaman D.  Clinical Nutrition for Pain, Inflammation, and Tissue Healing.  NutrAnalysis, Inc., 1998