title: [Abnormal muscle response monitoring during microvascular decompression for hemifacial spasm and long term results].
abstract: OBJECTIVE
  There is some debate over the reliability of intraoperative abnormal muscle response (AMR) monitoring as an indicator of postoperative long-term outcome in patients with hemifacial spasm (HFS). We investigated whether AMR findings obtained during microvascular decompression reflect postoperative long-term outcome. MATERIAS AND METHODS: Subjects were 51 HFS patients who underwent AMR monitoring during surgery. AMR recordings were obtained from the mentalis muscle by electrical stimulation of the temporal branch of the facial nerve and from the orbicularis oculi muscles by stimulation of the marginal mandibular branch. Postoperative follow-up was more than 5 years (range 61-118 months, mean 87 months).
  
  
  RESULTS
  In 37 patients, AMR disappeared after vascular decompression. Among those patients, only one presented with spasm at the final follow-up examination. In 6 of 7 patients with AMR that disappeared early before the completion of decompression, hemifacial spasm resolved completely. Five of six patients in whom AMR still remained but with decreased amplitude at the end of surgery experienced complete resolution.
  
  
  CONCLUSIONS
  Our findings suggest that intraoperative cessation including prior to decompression or decreased amplitude of AMR at the end of surgery indicates a high likelihood of postoperative long-term relief of HFS. We believe that intraoperative AMR monitoring is useful in MVD surgery for HFS.
authors.affiliation: Department of Neurosurgery, Brain Research Institute, University of Niigata, 1-757 Asahimachi-dori, Niigata-City 951-8585, Japan. mfuku529@bri.niigata-u.ac.jp
authors.forename: Masafumi
authors.initials: M
authors.lastname: Fukuda
authors.forename: Shinya
authors.initials: S
authors.lastname: Yamashita
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kawaguchi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Watanabe
authors.forename: Hiroatsu
authors.initials: H
authors.lastname: Murakami
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Takao
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D000368:Aged; D019299:Decompression, Surgical; D004558:Electric Stimulation; D004576:Electromyography; D005152:Facial Muscles / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D019569:Hemifacial Spasm / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D011379:Prognosis; D016896:Treatment Outcome