Biomechanical Milieu of Trigger PointsDecember 31, 2008 |
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Journal of Bodywork and Movement Therapies (2008) 12, 371-384
MYOFASCIAL PAIN RESEARCH
Uncovering the biochemical milieu of myofascial trigger points using in vivo microdialysis: An application of muscle pain concepts to myofascial pain syndrome.
Jay P. Shah, MD, Elizabeth A. Gilliams, BA
Rehabilitation Medicine Department, Clinical Center, National Institutes of Health, 10 Center Drive,
Room 1-1469, MSC 1604, Bethesda, MD 20892-1604 USA
Received 8 April 2008; received in revised form 27 May 2008; accepted 3 June 2008
Summary
This article discusses muscle pain concepts in the context of myofascial pain syndrome (MPS) and summarizes microdialysis studies that have surveyed the biochemical basis of this musculoskeletal pain condition. Though MPS is a common type of non-articular pain, its pathophysiology is only beginning to be understood due to its enormous complexity. MPS is characterized by the presence of myofascial trigger points (MTrPs), which are defined as hyperirritable nodules located within a taut band of skeletal muscle. MTrPs may be active (spontaneously painful and symptomatic) or latent (non-spontaneously painful). Painful MTrPs activate muscle nociceptors that, upon sustained noxious stimulation, initiate motor and sensory changes in the peripheral and central nervous systems. This process is called sensitization. In order to investigate the peripheral factors that influence the sensitization process, a microdialysis technique was developed to quantitatively measure the biochemical milieu of skeletal muscle. Biochemical differences were found between active and latent MTrPs, as well as in comparison with healthy muscle tissue. In this paper we relate the findings of elevated levels of sensitizing substances within painful muscle to the current theoretical framework of muscle pain and MTrP development.
Introduction
Myofascial pain syndrome (MPS) is a major progenitor of non-articular local musculoskeletal pain and tenderness that affects every age group, and is commonly recognized as "muscle knots" (Kaoet al., 2007). MPS has been associated with numerous pain conditions including radiculopathies, joint dysfunction, disk pathology, tendonitis, craniomandibular dysfunction, migraines, tensiontype headaches, carpal tunnel syndrome, computer-related disorders, whiplash-associated disorders, spinal dysfunction, and pelvic pain and other urologic syndromes, post-herpetic neuralgia, and complex regional pain syndrome (Borg-Stein and Simons, 2002). Characterized by a physical finding and symptom cluster, MPS lacked demonstrable pathology and attracted little research attention until recently. Although the specific pathophysiological basis of MTrP development and symptomatology is unknown, several promising lines of scientific study (i.e. histological, neurophysiological, biochemical, and somatosensory) have revealed objective abnormalities (Reitinger et al., 1996; Windisch et al.,1999; Mense, 2003; Shah et al., 2005, 2008; Kuan et al., 2007; Niddam et al., 2007). These findings suggest that myofascial pain is a complex form of neuromuscular dysfunction consisting of motor and sensory abnormalities involving both the peripheral and central nervous systems. MPS is not to be confused with fibromyalgia syndrome, which is ascribed to a collection of complaints including chronic widespread pain, accompanied by tactile allodynia, fatigue, sleep disturbance, and psychological distress (Wolfe et al., 1990).
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Copyright (c) 2008 Published by Elsevier Ltd.
