title: [Asymmetric hypertrophy of the masticatory muscles].
abstract: BACKGROUND
  Hypertrophy of the masticatory muscles most commonly affects the masseter. Less common cases of isolated or associated temporalis hypertrophy are also reported. Parafunctional habits, and more precisely bruxism, can favor the onset of the hypertrophy. This condition is generally idiopathic and can require both medical and/or surgical management.
  
  
  METHODS
  A 29-year-old patient was referred to our department for an asymmetric swelling of the masticatory muscles. Physical examination revealed a bilateral hypertrophy of the masticatory muscles, predominantly affecting the right temporalis and the left masseter. Major bruxism was assessed by premature dental wearing. The additional examinations confirmed the isolated muscle hypertrophy. Benign asymmetric hypertrophy of the masticatory muscles promoted by bruxism was diagnosed. Treatment with injections of type A botulinum toxin was conducted in association with a splint and relaxation. Its effectiveness has been observed at six months.
  
  
  CONCLUSIONS
  Few cases of unilateral or bilateral temporalis hypertrophy have been reported, added to the more common isolated masseter muscles hypertrophy. The diagnosis requires to rule out secondary hypertrophies and tumors using Magnetic Resonance Imaging. The condition is thought to be favoured by parafunctional habits such as bruxism. The conservative treatment consists in reducing the volume of the masticatory muscles using intramuscular injections of type A botulinum toxin. Other potential conservative treatments are wearing splints and muscle relaxant drugs. Surgical procedures aiming to reduce the muscle volume and/or the bone volume (mandibular gonioplasty) can be proposed.
authors.affiliation: Clinique de chirurgie maxillofaciale et de stomatologie, CHU Hôtel-Dieu, 1 place Alexis-Ricardeau, Nantes, France.
authors.forename: L
authors.initials: L
authors.lastname: Arzul
authors.forename: P
authors.initials: P
authors.lastname: Corre
authors.forename: R H
authors.initials: RH
authors.lastname: Khonsari
authors.forename: J-M
authors.initials: JM
authors.lastname: Mercier
authors.forename: B
authors.initials: B
authors.lastname: Piot
mesh_terms: D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D002012:Bruxism / Q000150:complications; D003131:Combined Modality Therapy; D003937:Diagnosis, Differential; D006801:Humans; D006984:Hypertrophy / Q000175:diagnosis / Q000628:therapy; D008279:Magnetic Resonance Imaging; D008297:Male; D008406:Masseter Muscle / Q000473:pathology; D008410:Masticatory Muscles / Q000473:pathology*; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D017090:Occlusal Splints; D011862:Radiography, Panoramic; D013703:Temporal Muscle / Q000473:pathology; D014463:Ultrasonography
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A