New Aspects of Myofascial Trigger Points: Etiological and Clinical

SUMMARY

Objectives: To identify important new developments in our understanding of the nature and clinical characteristics of myofascial trigger points [TrPs].

Findings: Recent research studies reinforce the credibility of three key features of an integrated hypothesis that is designed to explain the pathophysiology of TrPs: increased acetylcholine effect, increased muscle-fiber tension, and local release of sensitizing substances. Electromyographic studies of TrPs support an increased acetylcholine effect that produces endplate noise. Nine histological studies of animal and human subjects identify features that indicate abnormally increased muscle-fiber tension and help to account for the taut bands observed clinically. Microdialysis studies by Jay Shah, MD and colleagues at the National Institutes of Health compared, in nine subjects, the findings in active TrPs to findings in latent TrPs and in normal muscles [nine examinations]. They found a significantly reduced pressure pain threshold and pH at the three active TrPs. In active TrPs, seven pain-related substances were significantly increased: substance P, calcitonin gene-related peptide, bradykinin, serotonin, norepinephrine, tumor necrosis factor, and interleukin-1β. Using shockwave generators, Wolfgang Bauermeister, MD located active TrPs in the gluteus medius and/or gluteus minimus muscles in all of 114 patients with sciatica. In another study, treatment of idiopathic low back pain with piezoelectric generated shockwaves resulted in 80 percent reduction of pain in 15 of 20 patients after 10 treatments. Treatment with electrohydraulic shockwaves reduced the pain 85 percent in 18 of 20 patients after six treatments.

Conclusions: The microdialysis findings in TrPs help to validate the integrated hypothesis and to explain the painfulness of TrPs. Either an electrohydraulic or piezoelectric shockwave device can be used to locate and treat TrPs. Clinically, the electrohydraulic method seems preferable.

KEYWORDS:

• Myofascial pain
• trigger points
• prevalence
• diagnosis
• microdialysis
• shockwave