Surface Mapping of Masseter for Botulinum Toxin Injection.

Kim, Jun Hyung; Lee, Min Jae; Kim, Hyun Ji; Son, Dae Gu; Han, Ki Hwan; Lee, So Young; Lim, Jung Guen; Choi, In Jang

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Original Article

Journal of the Korean Society of Plastic and Reconstructive Surgeons 2005;32(3):311-313.
Published online May 1, 2005.

Surface Mapping of Masseter for Botulinum Toxin Injection.

Jun Hyung Kim, Min Jae Lee, Hyun Ji Kim, Dae Gu Son, Ki Hwan Han, So Young Lee, Jung Guen Lim, In Jang Choi

¹Deparment of Plasic and Reconstructive Surgery, Keimyung University School of Medicine, Daegu, Korea. med69@dsmc. or.kr
²Deparment of Rehabilitation, Keimyung University School of Medicine, Daegu, Korea.
³Deparment of Neurology, Keimyung University School of Medicine, Daegu, Korea.
⁴Deparment of Anatomy, Keimyung University School of Medicine, Daegu, Korea.

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.

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

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