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Masticatory muscle defects in hemifacial microsomia: A new embryological concept
Author(s) -
Heude Églantine,
Rivals Isabelle,
Couly Gérard,
Levi Giovanni
Publication year - 2011
Publication title -
american journal of medical genetics part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.064
H-Index - 112
eISSN - 1552-4833
pISSN - 1552-4825
DOI - 10.1002/ajmg.a.34095
Subject(s) - masticatory force , hemifacial microsomia , craniofacial , hypoplasia , anatomy , agenesis , neural crest , facial muscles , muscles of mastication , biology , masseter muscle , mandible (arthropod mouthpart) , medicine , orthodontics , embryo , genetics , temporomandibular joint , microbiology and biotechnology , botany , genus
First arch syndromes correspond to a wide spectrum of human latero‐facial congenital anomalies affecting cranial neural crest cells (CNCCs) derivatives of the first pharyngeal arch (PA1). The abnormal traits display variable quantitative expression and are often unilateral. Mandibular skeletal defects are invariably accompanied by hypoplasia or agenesis of masticatory muscles, but no explanation has been proposed for this association. Indeed, during embryonic development, CNCCs give only rise to skeletal components of the head while muscles derive from cephalic myogenic mesodermal cells (CMMCs). Recent studies on animal models have shown that communication between CNCCs and CMMCs is essential for the development of masticatory muscles: genetic lesions affecting only CNCCs can prevent muscularization of the jaws. To evaluate the involvement of CNCC/CMMC interactions in human craniofacial development, we performed a quantitative analysis of masticatory muscle and mandibular bone volumes on craniofacial CT‐scans from 8 children, ages 3 months to 16 years, affected by hemifacial microsomia. We found that: (1) in seven patients the masseter muscle is absent in the affected side; (2) the absence of masseter is correlated neither with the age of the patients nor with the volume and shape of the affected ramus; and (3) in all cases the pterygoid and the temporal muscles are either reduced or absent. Our findings suggest that an early developmental event is the origin of the muscular defects in these patients. We propose that the hypoplasia or agenesis of masticatory muscles derives from a defect in the CNCCs/CMMCs communication during early embryonic development. © 2011 Wiley‐Liss, Inc.