Pathophysiologic and electrophysiologic mechanisms of myofascial trigger points.

OBJECTIVE: To review recent clinical and basic science studies on myofascial trigger points (MTrPs) to facilitate a better understanding of the mechanism of an MTrP.

DATA SOURCES: English literature in the last 15 years regarding scientific investigations on MTrPs in either humans or animals.

STUDY SELECTION: Research works, especially electrophysiologic studies, related to the pathophysiology of MTrP.

DATA SYNTHESIS: (1) Studies on an animal model have found that a myofascial trigger spot (MTrS) in a taut band of rabbit skeletal muscle fibers is similar to a human MTrP in many aspects. (2) An MTrP or an MTrS contains multiple minute loci that are closely related to nerve fibers and motor endplates. (3) Both referred pain and local twitch response (characteristics of MTrPs) are related to the spinal cord mechanism. (4) The taut band of skeletal muscle fibers (which contains an MTrP or an MTrS in the endplate zone) is probably related to excessive release of acetylcholine in abnormal endplates.

CONCLUSION: The pathogenesis of an MTrP appears to be related to integrative mechanisms in the spinal cord in response to sensitized nerve fibers associated with abnormal endplates.