Update of Extracorporeal Shockwave Therapy in Myofascial Pain Syndrome

Abstract

Myofascial pain syndrome (MPS) is identified by palpating skeletal muscle for myofascial trigger points (MTrPs). A MTrP is “a hyperirritable spot in skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band.” There are emerging findings suggest that MPS is a complex form of neuromuscular dysfunction consisting of motor and sensory abnormalities involving both the peripheral and central nervous systems. Sensitization in corresponding spinal segments plays a major role in the formation of continuous pain in a given part of the body. The clinical manifestation of dorsal horn sensitization includes hyperalgesia of the dermatome, pressure pain sensitivity of the sclerotome and myofascial trigger points within the myotomes, which are supplied by the same sensitized spinal segment. Hence therapeutic approaches require varieties of techniques for eradiation of MTrP and desensitization of the whole related spinal segment. Extracorporeal Shock Wave Therapy (ESWT) also plays a role as desensitization. It can be nowadays approved as an effective, safe, noninvasive therapy for many musculoskeletal diseases and many conditions where regenerative effects are desirable. The proposed mechanisms for the benefit of ESWT on regeneration of musculoskeletal tissues and effective for pain relief include direct effects on tissue calcification, alteration of cell activity through cavitation, acoustic micro streaming, hypervascularity and blood flow increment, alteration of cell membrane permeability and effects on nociceptors through hyper stimulation, blocking the gate control mechanism. The effect of ESWT in myofascial pain syndrome (MPS), may by mechanotransduction effects, including increase perfusion, promote angiogenesis and alter the pain signaling in ischemic tissues caused by the influx of calcium, produce transient dysfunction of nerve excitability at the neuromuscular junction by bringing about the degeneration of AChR, and finally, a pure mechanistic with break-up the actin myosin links. The pain relief with ESWT might work by means of hyper stimulation analgesia. Overstimulation of the treated site would lead to a diminished transmission of signals to the brainstem. Animal studies show that ESWT has an influence on pain transmission by acting on substance P, calcitonin generelated peptide (CGRP) expression in the dorsal root ganglion and on neurovascular sprouting. In conclusion, ESWT plays a role as desensitization. It can be nowadays approved as an effective, safe, noninvasive therapy for many musculoskeletal diseases including MPS. It is considered as regenerative therapy as well.