A prospective study of the effect of botulinum toxin A on masseteric muscle hypertrophy with ultrasonographic and electromyographic measurement

Br J Plast Surg. 2001 Apr;54(3):197-200. doi: 10.1054/bjps.2000.3526.


We evaluated the effect of botulinum toxin A on masseteric muscle hypertrophy by using ultrasound and electromyography. Five patients (four with bilateral and one with unilateral masseteric muscle hypertrophy) were studied prospectively. In each patient, ultrasound-guided percutaneous intramuscular injection of botulinum toxin A was carried out. The change in muscle bulk was evaluated using serial ultrasonography and the electrical activity was assessed with electromyography. All five patients (nine hypertrophic muscles) showed a good response, with the maximal effect of a 31% reduction in muscle bulk seen 3 months after treatment. The effect remained stable one year after injection for six of the hypertrophic muscles, whereas three muscles needed a second injection to maintain the atrophy. This preliminary prospective study suggests that botulinum toxin A is a safe alternative method of treating masseteric muscle hypertrophy. However, the effect may be temporary and further intramuscular injection may be required to maintain atrophy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Botulinum Toxins, Type A / therapeutic use*
  • Electromyography
  • Female
  • Humans
  • Hypertrophy / drug therapy
  • Injections, Intramuscular
  • Male
  • Masseter Muscle / diagnostic imaging
  • Masseter Muscle / drug effects
  • Masseter Muscle / pathology*
  • Prospective Studies
  • Recurrence
  • Ultrasonography


  • Botulinum Toxins, Type A