title: Electrophysiologic change and facial contour following botulinum toxin A injection in square faces.
abstract: BACKGROUND
  This study was proposed to evaluate the facial contour and electrophysiologic changes of the masseter and temporalis muscles before and after botulinum toxin A injection in the wide lower face (square face).
  
  
  METHODS
  The botulinum toxin A injections were performed on 10 patients for the treatment of square face with masseter hypertrophy. To obtain an objective evaluation of the change in the facial contour, physical measurements, cephalometry, and clinical photographs were taken; and for evaluation of the function of the masseter and temporalis muscles, electromyographic studies were performed before and 1, 3, 5, 7, 9, and 12 months after treatment.
  
  
  RESULTS
  By physical measurements and cephalometry, the maximal reduction in lower facial contour (mean reduction, 6.6 mm by physical measurements and 7.5 mm by cephalometry) was observed 3 months after the injection, and increased slowly until 12 months after treatment. The maximal amplitude of the right and left masseter muscles decreased to the lowest value 1 month after treatment, with continuous increase being observed thereafter. There were statistically significant differences at all of the follow-up time points in reduction of lower facial contour by physical measurements and in electromyographic studies of the left masseter muscles. There was no hypertrophy of the temporalis muscle to compensate for the atrophy of the masseter muscles.
  
  
  CONCLUSIONS
  In this study, there was a 2-month interval between the lowest value of the maximal amplitude of the surface electromyography and the maximal clinical effects following botulinum toxin A injection, and there was similarity between the recovery of the masseter function and the diminution of the clinical effect. The clinical effect of botulinum toxin A persisted for 12 months after treatment on physical measurements, and the authors felt that this long-lasting effect of botulinum toxin A beyond expectation could be explained by incomplete recovery of muscle function.
authors: Incheon, South Korea From the Departments of Plastic and Reconstructive Surgery and Neurology, College of Medicine, Inha University.
authors: Choong Jae
authors: CJ
authors: Lee
authors: Sun Goo
authors: SG
authors: Kim
authors: Yu Jin
authors: YJ
authors: Kim
authors: Jin Yi
authors: JY
authors: Han
authors: Seong Hye
authors: SH
authors: Choi
authors: Se Il
authors: SI
authors: Lee
mesh_terms: D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004576:Electromyography; D004594:Electrophysiology; D005145:Face / Q000002:abnormalities* / Q000033:anatomy & histology; D005152:Facial Muscles / Q000187:drug effects* / Q000502:physiology*; D005260:Female; D006801:Humans; D006984:Hypertrophy / Q000188:drug therapy; D007273:Injections, Intramuscular; D008406:Masseter Muscle / Q000473:pathology*; D009465:Neuromuscular Agents / Q000008:administration & dosage*
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A
references: Baek, S. M., Baek, R. M., and Shin, M. S. Refinement in aesthetic contouring of the prominent mandibular angle. Aesthetic Plast. Surg. 18: 283, 1994.
references: Deguchi, M., Iio, Y., Kobayashi, K., and Shirakabe, T. Angle-splitting ostectomy for reducing the width of the lower face. Plast. Reconstr. Surg. 99: 1831, 1997.
references: von Lindern, J. J., Niedernhagen, B., Appel, T., Berge, S., and Reich, R. H. Type A botulinum toxin for the treatment of hypertrophy of the masseter and temporal muscles: An alternative treatment. Plast. Reconstr. Surg. 107: 327, 2001.
references: To, E. W., Ahuja, A. T., Ho, W. S., et al. A prospective study of the effect of botulinum toxin A on masseteric muscle hypertrophy with ultrasonographic and electromyographic measurement. Br. J. Plast. Surg. 54: 197, 2001.
references: Kim, H. J., Yum, K. W., Lee, S., et al. Effects of botulinum toxin type A on bilateral masseteric hypertrophy evaluated with computed tomographic measurement. Dermatol. Surg. 29: 484, 2003.
references: Park, M. Y., Ahn, K. Y., and Jung, D. S. Botulinum toxin type A treatment for contouring of the lower face. Dermatol. Surg. 29: 477, 2003.
references: Kim, N. H., Chung, J. J., Park, R. H., and Park, J. B. The use of botulinum toxin type A in aesthetic mandibular contouring. Plast. Reconstr. Surg. 115: 919, 2005.
references: Borodic, G. E., Ferrante, R. J., Pearce, L. B., et al. Pharmacology and histology of the therapeutic application of botulinum toxin. In J. Jankovic and M. Hallot (Eds.), Therapy with Botulinum Toxin. New York: Marcel Dekker, 1994. Pp. 119–157.
references: Bottero, L., Lefaucheur, J. P., Fadhul, S., et al. Electromyographic assessment of rectus abdominis muscle function after deep inferior epigastric perforator flap surgery. Plast. Reconstr. Surg. 113: 156, 2004.
references: Merlo, E., Pozzo, M., Antonutto, G., et al. Time-frequency analysis and estimation of muscle fiber conduction velocity from surface EMG signals during explosive dynamic contractions. J. Neurosci. Methods 142: 267, 2005.
references: Matarasso, A., and Deva, A. K. Botulinum toxin. Plast. Reconstr. Surg. 109: 1191, 2001.
references: Rorich, R. J., Janis, J. E., Figien, S., and Stuzin, J. M. The cosmetic use of botulinum toxin. Plast. Reconstr. Surg. 112: 177s, 2003.