title: Electromyographic differences between normal upper and lower facial muscles and the influence of onabotulinum toxin a.
abstract: OBJECTIVE
  Empirically determined doses of onabotulinum toxin A for aesthetic treatments are as much as 5 times higher for the upper than for the lower facial muscles.
  
  
  OBJECTIVE
  To use electromyography (EMG) to determine objectively whether the disparity between doses is due to intrinsic differences between the muscle groups' responses to onabotulinum toxin A or to variable amounts of paralysis required to achieve the desired aesthetic outcomes.
  
  
  METHODS
  We collected EMG data before and at 2 to 4 weeks and 3 months after 8- and 2-U onabotulinum toxin A injections to the corrugator and depressor anguli oris muscles, respectively.
  
  
  METHODS
  A private oculofacial plastic surgery practice.
  
  
  METHODS
  Twenty-six subjects recruited from February 1 through April 1, 2009.
  
  
  METHODS
  Electromyography recordings and cosmetic onabotulinum toxin A injections.
  
  
  METHODS
  Mean motor unit (MU) durations and maximal amplitudes at baseline and 2 to 4 weeks and 3 months after injection.
  
  
  RESULTS
  Baseline mean MU amplitudes were similar for the corrugator and depressor anguli oris muscles. At 2 to 4 weeks after injection, 78% MU and 64% maximal amplitude reduction for the corrugator muscle were detected, but only 54% MU and 18% maximal amplitude reduction for the depressor anguli oris (P = 2.7 × 10-8 and P = 1.3 × 10-14, respectively). At 3 months, function was partially recovered for both muscle groups.
  
  
  CONCLUSIONS
  Onabotulinum toxin A causes a similar dose-dependent reduction in MU and maximal voluntary amplitudes for muscles of the upper and lower face. The dose disparity appears to result from differences in the amount of paralysis required to achieve desirable aesthetic results.
  
  
  METHODS
  2.
authors: Harkness Eye Institute, Department of Ophthalmology, Columbia University, New York, NY 10032, USA. bjw15@columbia.edu
authors: Bryan J
authors: BJ
authors: Winn
authors: Bryan S
authors: BS
authors: Sires
mesh_terms: D000328:Adult; D000368:Aged; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage / Q000494:pharmacology*; D003357:Cosmetic Techniques; D004305:Dose-Response Relationship, Drug; D004576:Electromyography; D005152:Facial Muscles / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage / Q000494:pharmacology*; D017063:Outcome Assessment, Health Care
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A