title: The efficacy of botulinum toxin type A in managing chronic musculoskeletal pain: a systematic review and meta analysis.
abstract: BACKGROUND
  Botulinum toxin type A (BoNTA) is a neurotoxin that acts by inhibiting the release of neurotransmitters acetylcholine at neuromuscular junctions, thus reducing muscular contractions. Recent evidence suggests that BoNTA can reduce nociceptive activities of sensory neurons in animal models by inhibiting release of certain neuropeptides. Despite the therapeutic benefit of BoNTA in alleviating painful muscle spasms, its efficacy in other musculoskeletal pain conditions is less clear.
  
  
  OBJECTIVE
  We aim to examine the efficacy of BoNTA in reducing chronic musculoskeletal pain.
  
  
  METHODS
  Studies for inclusion in our report were identified using MEDLINE, EMBASE, PUBMED, Cochrane Central Register of Controlled Trials, CINAHL, and reference lists of relevant articles. Studies were considered eligible for inclusion if they were randomized controlled trials (RCTs), evaluating the efficacy of BoNTA injections in pain reduction. All studies were assessed and data were abstracted independently by paired reviewers. The outcome measures were baseline and final pain scores as assessed by the patients. The internal validity of trials was assessed with the Jadad scale. Disagreements were resolved through discussions.
  
  
  RESULTS
  Twenty-one studies were included in the systematic review and 15 of them were included in the final meta-analysis. There was a total of 706 patients in the meta-analysis, represented from trials of plantar fasciitis (n = 1), tennis elbow (n = 2), shoulder pain (n = 1), whiplash (n = 3), and myofascial pain (n = 8). Overall, there was a small to moderate pain reduction among BoNTA patients when compared to control (SMD = -0.27, 95% CI: -0.44 to -0.11). When the results were analyzed in subgroups, only tennis elbow (SMD = -0.44, 95% CI: -0.86 to -0.01) and plantar fasciitis (SMD = -1.04, 95% CI: -1.68 to -0.40) demonstrated significant pain relief. Although not in the meta-analysis, one back pain study also demonstrated positive results for BoNTA. Lastly, BoNTA was effective when used at ≥ 25 units per anatomical site or after a period ≥ 5 weeks.
  
  
  CONCLUSIONS
  In our meta-analysis, BoNTA had a small to moderate analgesic effect in chronic musculoskeletal pain conditions. It was particularly effective in plantar fasciitis, tennis elbow, and back pain, but not in whiplash or shoulder pain patients. However, more evidence is required before definitive conclusions can be drawn. On the other hand, there is convincing evidence that BoNTA lacks strong analgesic effects in patients with myofascial pain syndrome. A general dose-dependent and temporal response with BoNTA injections was also observed.
authors.affiliation: Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada.
authors.forename: Tony
authors.initials: T
authors.lastname: Zhang
authors.forename: Aleem
authors.initials: A
authors.lastname: Adatia
authors.forename: Wasifa
authors.initials: W
authors.lastname: Zarin
authors.forename: Misha
authors.initials: M
authors.lastname: Moitri
authors.forename: Abi
authors.initials: A
authors.lastname: Vijenthira
authors.forename: Rong
authors.initials: R
authors.lastname: Chu
authors.forename: Lehana
authors.initials: L
authors.lastname: Thabane
authors.forename: Walter
authors.initials: W
authors.lastname: Kean
mesh_terms: D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D006801:Humans; D009140:Musculoskeletal Diseases / Q000188:drug therapy*; D009141:Musculoskeletal System / Q000187:drug effects*; D010146:Pain / Q000188:drug therapy*; D016032:Randomized Controlled Trials as Topic
chemical_list: D019274:Botulinum Toxins, Type A