title: Efficacy and Safety of Single Botulinum Toxin Type A (Botox®) Injection for Relief of Upper Trapezius Myofascial Trigger Point: A Randomized, Double-Blind, Placebo-Controlled Study.
abstract: OBJECTIVE
  Botulinum toxin injection has been applied for pain relief in various chronic pain syndromes. Recently, systematic review studies reported inconclusive effects of Botulinum toxin in myofascial pain management. The present study aimed to demonstrate the efficacy and safety of Botulinum toxin type A (BTxA) (Botox®) injection for pain reduction in myofascial trigger point (MTrP) of the upper trapezius muscle.
  
  
  METHODS
  Thirty-three patients with 48 MTrP on the upper trapezius muscles over three months with moderate to severe pain intensity diagnosed at physical medicine and rehabilitation outpatient department were recruited between December 2011 and March 2012. Eligible patients were blinded and randomly injected with single 0.2 ml (20 IU) of BTxA for 24 MTrP and 0.2 ml of 0.9% NaCl solution for 24 MTrP at the most tender trigger point on the upper trapezius muscle. All patients were advised for stretching exercise and ergonomic adaptation throughout the study. At 3- and 6-week after injections, visual analogue scale (VAS), the pressure pain threshold (PPT), and reported adverse effects were measured.
  
  
  RESULTS
  Both BTxA and control groups demonstrated statistically significant differences in VAS reduction and increased PPT after 3 weeks and 6 weeks compared with before treatment. There were no statistically significant differences in VAS reduction from baseline between the two groups at 3- and 6-week after treatment. A statistically significant difference in improvement of PPT from baseline and 6-week after BTxA injection compared with 0.9% NaCl group was shown (1.0 ± 0.9 and 0.5 ± 0.7, p = 0.036). There was mild degree side-effects that spontaneous resolved within one week in both groups without significant difference in percentage. No severe adverse effects were reported during the study.
  
  
  CONCLUSIONS
  The efficacy in VAS reduction of a single 20 IU of Botulinum toxin type A (Botox®) injection was not different from 0.9% NaCl for myofascial trigger point at the upper trapezius muscle. However Botulinum toxin type A (Botox®) showed statistically significant more increased in pressure pain threshold at 6-week after injection without severe adverse effects.
authors.forename: Photsawee
authors.initials: P
authors.lastname: Kwanchuay
authors.forename: Thavatchai
authors.initials: T
authors.lastname: Petchnumsin
authors.forename: Pichet
authors.initials: P
authors.lastname: Yiemsiri
authors.forename: Nakkamol
authors.initials: N
authors.lastname: Pasuk
authors.forename: Wannarat
authors.initials: W
authors.lastname: Srikanok
authors.forename: Chanasak
authors.initials: C
authors.lastname: Hathaiareerug
mesh_terms: D065087:Acetylcholine Release Inhibitors / Q000008:administration & dosage / Q000009:adverse effects; D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage / Q000009:adverse effects; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007267:Injections; D008297:Male; D008875:Middle Aged; D009209:Myofascial Pain Syndromes / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects; D064171:Superficial Back Muscles / Q000503:physiopathology*; D016896:Treatment Outcome; D061028:Trigger Points / Q000503:physiopathology
chemical_list: D065087:Acetylcholine Release Inhibitors; D019274:Botulinum Toxins, Type A