Evaluating Current Understanding of Low-level Laser Light in the Management of Pain

Edmund Wong, James Zucherman, Dean T Mason, Garrett Lee
US Musculoskeletal Review, 2011;6(1):56-60
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Abstract

Low-level laser (LLL) light has been shown to have salutary effects on cellular processes and biological systems. Evidence is mounting that it is useful in alleviating certain clinical pain syndromes. Clinical studies have demonstrated the effectiveness of LLL in relieving acute and chronic neck pain, migraine and migrainous headache pain, musculoskeletal chest and back pain, specific types of tendonitis, repetitive stress injury, and other pain conditions, when the light is directed at the culprit soft tissue injury site(s). However, it might not be a panacea for managing all pain conditions; some tissue injuries might be more suited for LLL treatment. Clinical trials evaluating pain, in particular chronic pain, have their limitations. Importantly, merely directing the light on a painful site might not be adequate to treat the tissue injury; it is vital to improve understanding of the anatomy and physiology of different pain syndromes, to define the types and extent of injury, and to determine whether the different LLL parameters are sufficient to manage the specific types and extent of traumatic lesion that cause pain. Chronic studies must monitor the patient’s activities to protect the damaged site and avoid further re-injuries. LLL therapy is generally safe and devoid of major adverse effects. The management of pain using LLL is exciting and more controlled trials are under way to verify these timely observations and clinical studies.
Keywords
Low-level laser, low-power laser, low-level laser therapy, low-power laser therapy, pain management, pain control, musculoskeletal pain treatment
Disclosure The authors have no conflicts of interest to declare.
Received: April 15, 2011 Accepted May 20, 2011
Correspondence: Garrett Lee, MD, 450 Stanyan Street, San Francisco, California 94117. E: glee3@chw.edu

Laser is the acronym for light amplification by stimulated emission of radiation. The light has unique properties in that it is coherent, monochromatic, and collimated, and it has many applications in industry, communication, and medicine. Unlike high-power laser, which has been used as a surgical tool to cut and coagulate tissue, low-level laser (LLL) uses a power level that is 500mW or less, generates almost no thermal energy, and cannot cut or coagulate tissue. The LLL light is generally safe on all human tissue, with the exception of the retina, and has potential applications in wound healing, anesthesia, and pain management. With the emergence of low-power laser diodes, namely the gallium–aluminum–arsenide (830nm wavelength) or the gallium–arsenide (904nm wavelength), the LLL light can be delivered from a small, lightweight, convenient, portable laser unit. The purpose of this article is to evaluate the current status of LLL in the clinical management of pain.

Fundamental Actions of Low-level Lasers
Since Mester et al. first described the potential application of LLL light in wound healing in 1971,1 data on the non-surgical medicinal effects of light have been robust. The literature is replete with LLL affecting cellular processes including fibroblast proliferation, collagen synthesis, and tissue repair.2–6 Some of the mechanisms that have been elucidated to explain the beneficial effects of LLL in accelerating healing include absorbing light by receptors and enzymes within components of the respiratory chain and increasing adenosine triphosphate (ATP) synthesis within the mitochondria, signaling and expressing various genes that enhance cell proliferation, suppressing the immune responses of the body, promoting an anti-inflammatory effect, increasing microvascular circulation, and the lymphatic drainage of edematous fluid.7–15 In animal studies, LLL has been found to have a possible direct inhibitory effect on the nerve conduction of pain.16,17

Clinical Effects of Low-level Laser on Pain
Numerous papers have been published showing the benefits of LLL in relieving pain. Wong and colleagues have shown the efficacy of the 830nm LLL in patients with migraine and migrainous-type headaches, based on methodically examining and treating the actual sites of soft tissue injury.18 By this similar method, LLL has also been shown to reduce pain in patients with temporomandibular joint dysfunction,19,20 temporal headaches relating to the styloid process,21 carpal tunnel syndrome, and repetitive stress injury. The use of the LLL was safe and there were no major adverse effects.

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