title: Botulinum toxin for masseter hypertrophy.
abstract: BACKGROUND
  Benign masseter muscle hypertrophy is an uncommon clinical phenomenon of uncertain aetiology which is characterised by a soft swelling near the angle of the mandible. The swelling may on occasion be associated with facial pain and can be prominent enough to be considered cosmetically disfiguring. Varying degrees of success have been reported for some of the treatment options for masseter hypertrophy, which range from simple pharmacotherapy to more invasive surgical reduction. Injection of botulinum toxin type A into the masseter muscle is generally considered a less invasive modality and has been advocated for cosmetic sculpting of the lower face. Botulinum toxin type A is a powerful neurotoxin which is produced by the anaerobic organism Clostridium botulinum and when injected into a muscle causes interference with the neurotransmitter mechanism producing selective paralysis and subsequent atrophy of the muscle.
  
  
  OBJECTIVE
  To assess the effects of botulinum toxin type A in the management of benign bilateral masseter hypertrophy.
  
  
  METHODS
  We searched the following databases in August 2008: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, issue 3); MEDLINE (via PubMed) (1950 to August 2008); EMBASE (via embase.com) (1980 to August 2008); and LILACS via BIREME. We searched two bibliographic databases of regional journals which may be expected to contain relevant trials (IndMED and Iranmedex) using free text terms appropriate for this review.
  
  
  METHODS
  Randomised controlled clinical trials (RCTs) and controlled clinical trials (CCTs) comparing intra-masseteric injections of botulinum toxin versus placebo administered for cosmetic facial sculpting in individuals of any age with bilateral benign masseter hypertrophy, which had been self-evaluated and confirmed by clinical and radiological examination. We excluded participants with unilateral or compensatory contralateral masseter hypertrophy resulting from head and neck radiotherapy.
  
  
  METHODS
  Two review authors conducted screening of studies in duplicate and independently, and although no eligible trials were identified, the two authors had planned to extract data independently and assess trial quality using standard Cochrane Collaboration methodologies.
  
  
  RESULTS
  We retrieved 167 references to studies, none of which matched the inclusion criteria for this review and all of which were excluded.
  
  
  CONCLUSIONS
  We were unable to identify any randomised controlled trials on the efficacy of intra-masseteric injections of botulinum toxin for people with bilateral benign masseter hypertrophy. The absence of high level evidence for the effectiveness of this intervention emphasises the need for well-designed, adequately powered, randomised controlled clinical trials (RCTs) and controlled clinical trials (CCTs).
authors.affiliation: Maxillofacial Surgery Unit, Bahrain Defence Force - Royal Medical Services, PO Box 33255, Essa Town, Bahrain.
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Al-Muharraqi
authors.forename: Zbys
authors.initials: Z
authors.lastname: Fedorowicz
authors.forename: Jaffer
authors.initials: J
authors.lastname: Al Bareeq
authors.forename: Reem
authors.initials: R
authors.lastname: Al Bareeq
authors.forename: Mona
authors.initials: M
authors.lastname: Nasser
mesh_terms: D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D006801:Humans; D006984:Hypertrophy / Q000188:drug therapy; D007273:Injections, Intramuscular; D008406:Masseter Muscle / Q000473:pathology*; D009465:Neuromuscular Agents / Q000627:therapeutic use*
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A