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Open AccessArticle

Anatomical Considerations When Treating Compensatory Hypertrophy of the Upper Part of the Masseter after Long-Term Botulinum Neurotoxin Type A Injections

1
Division in Anatomy and Developmental Biology, Department of Oral Biology, Human Identification Research Institute, BK21 PLUS Project, Yonsei University College of Dentistry, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
2
Labella clinic, 455 Gangnam-daero, Seocho-gu, Seoul 06611, Korea
3
Clinical Practitioner, 200 W 60th St, New York, 10023 NY, USA
4
Department of Materials Science & Engineering, College of Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Toxins 2020, 12(3), 202; https://doi.org/10.3390/toxins12030202
Received: 7 February 2020 / Revised: 19 March 2020 / Accepted: 19 March 2020 / Published: 22 March 2020
(This article belongs to the Special Issue Botulinum Neurotoxin Injection)
The masseter is the most targeted muscle when treating hypertrophy to produce a smooth face shape. Compensatory hypertrophy is a well known clinical sequela that occurs in botulinum neurotoxin (BoNT) treatments and is limited to the lower part of the masseter. Based on the masseteric hypertrophy procedure, which targets a confined area, we predicted the possibility of compensatory hypertrophy occurring in the upper part of the masseter. If the patient complains about an unexpected result, additional injections must be performed, but the involved anatomical structures have not been revealed yet. The aim of this study was to identify the morphological patterns of the masseter. Deep tendons were observed in most specimens of the upper part of the masseter and mostly appeared in a continuous pattern (69.7%). The superficial and deep tendons could be classified into a simply connected form and forms surrounding part of the muscle. In 45.5% of cases there were tendon capsules that completely enclosed the muscle, which can interfere with how the injected toxin spreads. Interdigitation patterns in which the tendons could be identified independently between the muscles were present in 9.1% of cases. The present findings provide anatomical knowledge for use when injecting BoNT into the masseter. View Full-Text
Keywords: superficial part of masseter muscle; compensatory hypertrophy; botulinum neurotoxin type A injection; masseteric hypertrophy treatment superficial part of masseter muscle; compensatory hypertrophy; botulinum neurotoxin type A injection; masseteric hypertrophy treatment
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Lee, K.-L.; Cho, H.J.; Bae, H.; Park, H.J.; Park, M.S.; Kim, H.-J. Anatomical Considerations When Treating Compensatory Hypertrophy of the Upper Part of the Masseter after Long-Term Botulinum Neurotoxin Type A Injections. Toxins 2020, 12, 202.

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