The risorius muscle: Anatomic considerations with reference to botulinum neurotoxin injection for masseteric hypertrophy

Jung Hee Bae, Da Yae Choi, Jae Gi Lee, Kyle K. Seo, Tanvaa Tansatit, Heejin Kim

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

BACKGROUND: The botulinum neurotoxin Type A (BTX) injection into the masseter muscle often causes a change in the facial expression. There is as yet no precise anatomic evidence to support this etiologic factor of constrained facial expressions. OBJECTIVE: The aim of this study was to clarify the location and boundaries of the risorius muscle and its topographical relationship with the surrounding structures. MATERIALS AND METHODS: This study involved the dissection of 48 hemifaces. The locations of origin and insertion points of the risorius muscle were measured, and the masseter muscle was divided into 6 equally sized rectangular areas. RESULTS: Cases where the masseter muscle was covered by the risorius muscle were classified into the following 4 types: in Type A, Area III was partially covered by the risorius (17.8%); in Type B, Area VI was partially covered (20.0%); in Type C, Areas III and VI were partially covered (53.3%); and in Type D, Areas II, III, and VI were covered (6.7%). CONCLUSION: These findings suggest that the medial part of the masseter muscle represents a hazard zone into which the injection of BTX may affect the risorius muscle, potentially resulting in iatrogenic unnatural facial expressions.

Original languageEnglish
Pages (from-to)1334-1339
Number of pages6
JournalDermatologic Surgery
Volume40
Issue number12
DOIs
Publication statusPublished - 2014 Jan 1

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Masseter Muscle
Neurotoxins
Hypertrophy
Facial Expression
Muscles
Injections
Dissection

All Science Journal Classification (ASJC) codes

  • Surgery
  • Dermatology

Cite this

Bae, Jung Hee ; Choi, Da Yae ; Lee, Jae Gi ; Seo, Kyle K. ; Tansatit, Tanvaa ; Kim, Heejin. / The risorius muscle : Anatomic considerations with reference to botulinum neurotoxin injection for masseteric hypertrophy. In: Dermatologic Surgery. 2014 ; Vol. 40, No. 12. pp. 1334-1339.
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abstract = "BACKGROUND: The botulinum neurotoxin Type A (BTX) injection into the masseter muscle often causes a change in the facial expression. There is as yet no precise anatomic evidence to support this etiologic factor of constrained facial expressions. OBJECTIVE: The aim of this study was to clarify the location and boundaries of the risorius muscle and its topographical relationship with the surrounding structures. MATERIALS AND METHODS: This study involved the dissection of 48 hemifaces. The locations of origin and insertion points of the risorius muscle were measured, and the masseter muscle was divided into 6 equally sized rectangular areas. RESULTS: Cases where the masseter muscle was covered by the risorius muscle were classified into the following 4 types: in Type A, Area III was partially covered by the risorius (17.8{\%}); in Type B, Area VI was partially covered (20.0{\%}); in Type C, Areas III and VI were partially covered (53.3{\%}); and in Type D, Areas II, III, and VI were covered (6.7{\%}). CONCLUSION: These findings suggest that the medial part of the masseter muscle represents a hazard zone into which the injection of BTX may affect the risorius muscle, potentially resulting in iatrogenic unnatural facial expressions.",
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The risorius muscle : Anatomic considerations with reference to botulinum neurotoxin injection for masseteric hypertrophy. / Bae, Jung Hee; Choi, Da Yae; Lee, Jae Gi; Seo, Kyle K.; Tansatit, Tanvaa; Kim, Heejin.

In: Dermatologic Surgery, Vol. 40, No. 12, 01.01.2014, p. 1334-1339.

Research output: Contribution to journalArticle

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AU - Tansatit, Tanvaa

AU - Kim, Heejin

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N2 - BACKGROUND: The botulinum neurotoxin Type A (BTX) injection into the masseter muscle often causes a change in the facial expression. There is as yet no precise anatomic evidence to support this etiologic factor of constrained facial expressions. OBJECTIVE: The aim of this study was to clarify the location and boundaries of the risorius muscle and its topographical relationship with the surrounding structures. MATERIALS AND METHODS: This study involved the dissection of 48 hemifaces. The locations of origin and insertion points of the risorius muscle were measured, and the masseter muscle was divided into 6 equally sized rectangular areas. RESULTS: Cases where the masseter muscle was covered by the risorius muscle were classified into the following 4 types: in Type A, Area III was partially covered by the risorius (17.8%); in Type B, Area VI was partially covered (20.0%); in Type C, Areas III and VI were partially covered (53.3%); and in Type D, Areas II, III, and VI were covered (6.7%). CONCLUSION: These findings suggest that the medial part of the masseter muscle represents a hazard zone into which the injection of BTX may affect the risorius muscle, potentially resulting in iatrogenic unnatural facial expressions.

AB - BACKGROUND: The botulinum neurotoxin Type A (BTX) injection into the masseter muscle often causes a change in the facial expression. There is as yet no precise anatomic evidence to support this etiologic factor of constrained facial expressions. OBJECTIVE: The aim of this study was to clarify the location and boundaries of the risorius muscle and its topographical relationship with the surrounding structures. MATERIALS AND METHODS: This study involved the dissection of 48 hemifaces. The locations of origin and insertion points of the risorius muscle were measured, and the masseter muscle was divided into 6 equally sized rectangular areas. RESULTS: Cases where the masseter muscle was covered by the risorius muscle were classified into the following 4 types: in Type A, Area III was partially covered by the risorius (17.8%); in Type B, Area VI was partially covered (20.0%); in Type C, Areas III and VI were partially covered (53.3%); and in Type D, Areas II, III, and VI were covered (6.7%). CONCLUSION: These findings suggest that the medial part of the masseter muscle represents a hazard zone into which the injection of BTX may affect the risorius muscle, potentially resulting in iatrogenic unnatural facial expressions.

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