What is the efficacy 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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In a randomized, double-blind, prospective, placebo-controlled study by Wheeler et al, 33 patients with a single cervical myofascial trigger point were injected with either 50 U or 100 U of BTX-A or normal saline. [43] All 3 groups showed significant treatment effects as measured by VAS, psychometric testing, and pressure algometry. Group differences were apparent only when the authors considered the number of patients who were asymptomatic from the injections, but no clear statistically significant benefit of BTX-A over placebo was demonstrated over 4 months.

However, a striking difference in treatment response was noted between the participants in the 2 BTX-A treated groups compared with those in the initial placebo group who elected to receive a second, unblinded BTX-A 100 U injection into the same trigger point. Using the same measurement criteria, this second study arm showed a beneficial effect from BTX-A, but the small number of participants precluded meaningful statistical analysis. [44]

In a follow-up open-label study, Wheeler and Goolkasian examined a 44 patient-cohort with refractory cervical-thoracic (73%) or lumbosacral (9%) muscular pain (or both) who received BTX-A treatment in a private outpatient clinic combined with physical therapy. [43] BTX-A treatment was directed at painful muscles with spasm or trigger points. BTX-A dosages were tailored to meet individual patient needs and varied between 50-200 U. Eighty percent of all patients reported significantly reduced pain after their initial treatment session. Forty-one percent of patients who only underwent one treatment session and an additional 27% who required a second injection session still reported "adequate pain relief" when contacted 2 years later.

However, in a third follow-up study, Wheeler and colleagues were unable to detect any statistically significant differences in pain reduction between BTXA and placebo-treated patients with painful cervical-thoracic paraspinal and trapezius muscles using higher total doses of BTX-A (eg, 200-300 U/session), similar to treatment doses commonly used for cervical dystonia.

In the studies described so far, physicians have used similar injection methodology by placing the neurotoxin into symptomatic trigger points, a practice consistent with the treatment techniques originally described by Simons et al. [45]

However, some advocate placement of BTX into the muscle's motor point (eg, into standardized sites in the mid-belly of affected muscles). [46] Using a BTX treatment technique that involved injecting the muscle in it's motor point pattern with doses of BTXA ranging from 20-600 U, Lang studied the treatment of 72 patients who received 95 injection session treatments. [46] Sixty percent of patients experienced good-to-excellent results at 22-60 days following injection.

In a 12-week randomized, double-blind, placebo-controlled study, 132 patients with cervicothoracic myofascial pain were treated with BTX-A or saline by Ferrante et al. [47] No significant differences in outcome were seen between groups. Patients receiving BTX-A were treated with a total of 50-250 U of toxin divided among 5 injection sites.

Porta, in a single blinded study, evaluated the difference between lidocaine/methylprednisolone injections compared with BTX-A injections into symptomatic myofascial trigger points in the psoas, piriformis, or scalenus anterior muscles; [48] 80-150 U of toxin were used. Each group received benefit, but the toxin-treated patients experienced a greater duration of relief.

Opida presented 31 patients with posttraumatic neck pain who he treated with BTX-B injections in an open-label study. [49] Seventy-one percent of his patients reported significant reductions in headache pain frequency and severity. In 2 separate open-label studies, Taqi and colleagues showed that either type of BTX may be effective in the treatment of myofascial pain. [50, 51] Several case reports using BTX-B injections in the management of chronic myofascial pain have suggested overall beneficial results. [52, 53, 54]

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