title: Volume and shape of masticatory muscles in patients with hemifacial microsomia.
abstract: OBJECTIVE
  To test the following hypotheses in hemifacial microsomia (HFM): (1) the volumes of the masseter, lateral and medial pterygoid, and temporal muscles are reduced on the affected versus unaffected side; (2) significant differences exist between the degrees of right-left disproportion in these four masticatory muscles; (3) circumferential shapes of the masticatory muscles are more irregular on the affected versus unaffected side; and (4) the degree of masticatory muscle right-left disproportion can be judged by the degree of ear, mandibular, or dental anomalies.
  
  
  METHODS
  Ten preadolescent patients with HFM were studied using facial photographs, dental casts, cephalometric and panoramic radiographs, and helical computed tomography scanning and three-dimensional reconstruction technique. Volumes of masseter, lateral and medial pterygoid, and temporal muscles on both sides were measured. Muscle volume disproportion was expressed as the affected/unaffected ratio. Muscle circumferential irregularity was expressed as the ratio between the total circumferential length and corresponding cross-sectional area.
  
  
  RESULTS
  Masticatory muscle volumes were significantly smaller on the affected versus unaffected side. No significant differences were observed between the degrees of disproportion of the four masticatory muscles examined. Circumferential shapes of masticatory muscles were significantly more irregular on the affected versus unaffected side. There were no significant relationships of the degree of ear, mandibular, or dental anomalies in relation to masticatory muscle disproportion.
  
  
  CONCLUSIONS
  In HFM the masseter, lateral and medial pterygoid, and temporal muscles all have a significantly smaller volume on the affected versus unaffected side, and specific muscles were not severely affected in the present subjects. Furthermore, all four muscles showed a significantly more irregular shape on the affected versus unaffected side. Finally, the severity of masticatory muscle disproportion can probably not be judged by the degree of ear, mandibular, and dental anomalies in preadolescent patients with HFM.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Graduate School of Dentistry, Osaka University, Osaka, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Takashima
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kitai
authors.forename: Shumei
authors.initials: S
authors.lastname: Murakami
authors.forename: Souhei
authors.initials: S
authors.lastname: Furukawa
authors.forename: Sven
authors.initials: S
authors.lastname: Kreiborg
authors.forename: Kenji
authors.initials: K
authors.lastname: Takada
mesh_terms: D000293:Adolescent; D002508:Cephalometry; D002648:Child; D004431:Ear, External / Q000002:abnormalities; D005146:Facial Asymmetry / Q000150:complications / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008334:Mandible / Q000002:abnormalities; D008406:Masseter Muscle / Q000473:pathology; D008410:Masticatory Muscles / Q000473:pathology*; D003765:Models, Dental; D010781:Photography; D011626:Pterygoid Muscles / Q000473:pathology; D011862:Radiography, Panoramic; D018709:Statistics, Nonparametric; D013703:Temporal Muscle / Q000473:pathology; D036542:Tomography, Spiral Computed; D014071:Tooth Abnormalities / Q000150:complications