title: Hemimasticatory spasm associated with localized scleroderma and facial hemiatrophy.
abstract: OBJECTIVE
  To report a case and discuss the mechanism of hemimasticatory spasm.
  
  
  METHODS
  Case report.
  
  
  METHODS
  A 37-year-old woman had a 3-year history of involuntary spasms of the right masseter muscle in association with localized scleroderma and facial hemiatrophy. Electrophysiological studies revealed a normal blink reflex. However, the masseter reflex and silent period were absent on the affected side. Distal latency and compound muscle action potential of the masseter nerve were normal. Needle electromyography demonstrated irregular bursts of motor unit potentials similar to those described in hemifacial spasm. A magnetic resonance imaging scan of the head showed mild hypertrophy of the masseter muscle and atrophy of subcutaneous fatty tissues on the affected side. Local injection of botulinum toxin A into the masseter muscle resolved the patient's symptoms.
  
  
  CONCLUSIONS
  On the basis of clinical and electrophysiological findings, focal demyelination of motor branches of the trigeminal nerve owing to deep tissue changes is suggested as the cause of abnormal excitatory electrical activities resulting in involuntary masticatory movement.
authors.affiliation: Department of Neurology, College of Medicine, Seoul National University, Korea.
authors.forename: H J
authors.initials: HJ
authors.lastname: Kim
authors.forename: B S
authors.initials: BS
authors.lastname: Jeon
authors.forename: K W
authors.initials: KW
authors.lastname: Lee
mesh_terms: D000200:Action Potentials; D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage; D004576:Electromyography; D005150:Facial Hemiatrophy / Q000150:complications*; D005260:Female; D006801:Humans; D006984:Hypertrophy / Q000209:etiology / Q000473:pathology; D007273:Injections, Intramuscular; D008279:Magnetic Resonance Imaging; D008406:Masseter Muscle / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D011930:Reaction Time; D012021:Reflex, Abnormal; D012594:Scleroderma, Localized / Q000150:complications*; D016896:Treatment Outcome; D014313:Trismus / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology*
chemical_list: D019274:Botulinum Toxins, Type A