J Korean Soc Plast Reconstr Surg.  2005 May;32(3):311-313.

Surface Mapping of Masseter for Botulinum Toxin Injection

• Kim JH
• Lee MJ
• Kim HJ
• Son DG
• Han KH
• Lee SY
• Lim JG
• Choi IJ

Abstract

Generally, many Asian women tend to dislike the square jaw, as they believe it makes the face look wider, giving a stubborn and strong impression. Contouring of the mandible is therefore a relatively common aesthetic procedure among Asians. These days, the use of botulinum toxin for contouring of the lower face offer simple alternative to surgery. Motor point, which is the site over a muscle where its contraction may be elicited by a minimal intensity short duration electrical stimulus, is the optimal injection point of botulinum toxin. Study was undertaken to identify the location of motor point of the masseter muscle and the skin surface landmark. First, the thickest point of the masseter muscle was inspected through palpation and inspection by 3 different individual plastic surgeons and then compound muscle action potentials(CMAPs) of masseter muscle in 15 health volunteers were recorded using EMG. For the localization of the measured points, line between lateral canthus to the mandibular angle was used. Location of motor points were mapped to skin surface from lateral canthus in a percentage of the distance along the landmark line and in distance in millimeters. The clinical injection point was located at 71.69 percentile and 7.3mm of the landmark line. The motor point test was located at 72.54 percentile and 7.1mm of the landmark line. The depth of motor point was 16mm. There was no statistically significant difference between the clinical injection point and the motor point. We conclude that surface mapping of motor point of the masseter muscle would increase accessibility and accuracy in botulinum toxin injection for contouring of the lower face.

Keyword

Benign masseteric hypertrophy; Botulinum toxin; Motor point; Surface mapping

MeSH Terms

Asian Continental Ancestry Group
Botulinum Toxins*
Female
Humans
Jaw
Mandible
Masseter Muscle
Palpation
Skin
Volunteers
Botulinum Toxins