What is the role of botulinum toxin (BTX) injections for the management of musculoskeletal pain?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Multiple studies have looked at the neurotoxin's potential for treatment of painful musculoskeletal conditions, including chronic myofascial and spinal pain syndromes.

Musculoskeletal pain is often attributed to myofascial pain syndrome (MPS). Of patients with pain presenting to various specialists, the prevalence of MPS has been reported to vary from 30-90%, depending on the subspecialty practice and setting. MPS is characterized by painful muscles with increased tone and stiffness containing trigger points, which are tender, firm nodules, or taut bands, usually 3-6 mm in diameter. Palpation produces aching pain in localized reference zones.

Mechanical stimulation of the taut band by needling or brisk transverse pressure produces a localized muscle twitch. Trigger point palpation often elicits a "jump sign"—an involuntary reflexlike recoil or flinching from the pain—that is disproportionate to the pressure applied. Multiple treatments, including trigger point injections, have long been advocated; however, reports conflict as to whether any therapeutic substance injected into a muscle provides more benefit than dry needling alone.

The pathogenesis of myofascial trigger points is unknown; however, Simons postulates that abnormally increased motor endplate activity caused by excessive release of acetylcholine at the neuromuscular junction results in spontaneous electrical activity and extrafusal muscle contraction in the immediate vicinity of the extrafusal muscle end plates, thus forming the taut band and trigger point. [41]

Numerous studies have examined the role of BTX for treating chronic cervical-thoracic pain associated with myofascial pain and dysfunction. In a randomized, controlled, crossover study, Cheshire et al injected myofascial trigger points in the cervical and shoulder region in 6 patients with either BTX-A (50 U spread out over 2-3 areas) or normal saline (NS). [42] Crossover occurred at 8 weeks. Four of the 6 patients reported at least 30% pain reduction, as measured by visual analogue scales (VAS), with BTX-A, but not saline injections.


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