What is the efficacy of botulinum toxin in the treatment of myofascial pain?

Updated: Mar 11, 2019
  • Author: Heather Rachel Davids, MD; Chief Editor: Elizabeth A Moberg-Wolff, MD  more...
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Many therapies are available to patients with myofascial pain syndrome. Much of the variation in forms of treatment (and diagnoses) of this disorder probably results from differences in culture, training, and recognition of an often undiagnosed syndrome of pain, dysfunction, and autonomic dysregulation. The etiology of myofascial pain syndrome associated with trigger points is incompletely understood. Some clinicians believe that it characteristically results from either an acute episode of muscle overload or from chronic and/or repetitive muscle overload. Active myofascial trigger points (MTrPs), which cause pain, exhibit marked localized tenderness and often refer pain to distant sites and disturb motor function. In addition, MTrPs may produce autonomic changes.

For clinical identification of MTrPs, the clinician palpates a localized tender spot in a nodular portion of a taut ropelike band of muscle fibers. Pressure over a trigger point elicits pain at that area and also may elicit pain at a site distant from the point under the fingertip (in a phenomenon known as referred pain). Upon palpation, MTrPs also elicit pain that mirrors the patient's experience. Applied pressure often evokes from the patient the response, "That's my pain!" Insertion of a needle, abrupt palpation, or even a brisk tap with the fingertip directly over the trigger point may result in a brief muscle contraction that is detectable by the examiner. This rapid contraction of muscle fibers of the ropelike taut band is termed a local twitch response.

In muscles that move a relatively small mass or are large and superficial (eg, finger extensors, gluteus maximus), the response is seen easily and may cause the limb to jump when the examiner introduces a needle into the trigger point. Localized abnormal response from the autonomic nervous system may cause piloerection, localized sweating, or regional temperature changes in the skin, attributed to altered blood flow.

Injection of muscles with botulinum toxin has been reported to be effective for myofascial pain caused by trigger points (TrPs) in a few small prospective studies. However, strong evidence of efficacy in larger, multicenter trials is lacking. [8, 32, 33]

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