Topography of the masseter muscle in relation to treatment with botulinum toxin type A.
OBJECTIVE
The objective of this study was to provide the safest and most efficient site for injection of botulinum toxin type A into the masseter muscle.


METHODS
This study was performed on 40 hemifaces from cadavers. The surface of the masseter was compartmentalized into areas I to VIII. Areas I, III, V, and VII were assigned to represent the upper 4 compartments from the posterior aspect of each muscle, and areas II, IV, VI, and VIII were assigned to represent the lower 4 compartments.


RESULTS
The parotid gland usually covered compartments I and II, and the marginal mandibular branch of the facial nerve was located a mean of 7.4 mm above the inferior mandibular margin. The parotid duct was usually located above the reference line connecting the tragus and the cheilion.


CONCLUSIONS
The center of compartment VI is the safest and most efficient injection site for botulinum toxin type A into the masseter muscle.
Hu
Kyung-Seok
KS
Division in Anatomy and Developmental Biology, Department of Oral Biology, Yonsei University College of Dentistry, Seoul, Korea.
Kim
Seong-Taek
ST
Hur
Mi-Sun
MS
Park
Ju-Hyun
JH
Song
Wu-Chul
WC
Koh
Ki-Seok
KS
Kim
Hee-Jin
HJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D002102:Cadaver; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular / Q000379:methods; D008297:Male; D008340:Mandibular Nerve / Q000033:anatomy & histology; D008406:Masseter Muscle / Q000033:anatomy & histology* / Q000098:blood supply / Q000294:innervation; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D010306:Parotid Gland / Q000033:anatomy & histology; D012449:Safety
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A