Project Summary Myofascial pain syndrome (MPS) remains a poorly characterized entity. Although affecting millions of individuals, we do not understand the basic underlying mechanisms of its development, persistence, and response to therapy, including the use of common therapies such as trigger point (TrP) injection, dry needling, and myofascial release. Improved methods of assessing MPS, both in its active and latent phases, and its response to therapy are needed, not only to improve our diagnostic capabilities but also to better understand MPS’ origins and for quantifying the effect of treatment. In this study, we propose to apply three methodologies to the assessment of MPS and TrP quantification, two of which, to our knowledge, have never been used before in this context. The first, electrical impedance myography (EIM), a recently developed method that characterizes muscle tissue non-invasively using directed, very high-frequency, electrical current provides insights into tissue histological features and structure non-invasively. It has been shown to be sensitive to conditions in which muscle fibers are hypertrophied or atrophied or in which disease other pathological changes, such as fibrosis, are present. An advantage of this technique is that it is entirely painless, rapid to apply to discrete areas of muscle, and can even be performed at home. The second method, myofiber threshold tracking (TT) excitability testing, assesses the relatively excitability of myofibers by using a single small needle electrode to provide a conditioning stimulus followed by a test stimulus. The conditioning stimulus increases the speed of conduction in the myofibers and can thus provide a convenient measure of excitability within a TrP. It has already proven to be sensitive to a number of conditions impacting myofiber function. The third method, ultrasound with shear wave elastography (SWE), has been studied to some extent in MPS and provides insight into the rigidity of the muscle tissue and will provide a valuable comparator to these other two technologies. In the R61 phase of the proposed work, we will study patients with both active and latent MPS affecting the upper trapezius, as well as a group of healthy subjects with these three methodologies to establish differences between groups, repeatability of the techniques, and the relationships across them (Aims 1a, 1b, and 1c, respectively) and their relationship to standard pain scores. After approval based on our R61milestones, in the R33 phase (Aim 2), we will use all three methods in a clinical trial assessing the effectiveness of TrP dry needling in a group of patients with active MPS affecting the upper trapezius. EIM outcomes will serve as the primary outcome of interest, with data being collected both in the clinic and at home. At the conclusion of this work, we will have established the use of these technologies for the assessment MPS, providing new insights into underlying mechanisms and convenient new biomarkers to predict and assess the benefit of therapeutic intervention.

Project Narrative Myofascial pain syndrome (MPS) remains a poorly characterized entity causing considerable disability and resulting in the use of prescription pain medications. Tools to quantitatively assess MPS and the effect of therapy are needed so that better therapies can be devised and tested and its underlying physiology better understood. In this study, we propose to study three separate but complementary modalities, electrical impedance myography, muscle fiber electrical excitability testing, and ultrasound with shear wave elastography, as tools in the evaluation of MPS and the effect of therapy.