title: Efficacy of the Disappearance of Lateral Spread Response before and after Microvascular Decompression for Predicting the Long-Term Results of Hemifacial Spasm Over Two Years.
abstract: OBJECTIVE
  The purpose of this large prospective study is to assess the association between the disappearance of the lateral spread response (LSR) before and after microvascular decompression (MVD) and clinical long term results over two years following hemifacial spasm (HFS) treatment.
  
  
  METHODS
  Continuous intra-operative monitoring during MVD was performed in 244 consecutive patients with HFS. Patients with persistent LSR after decompression (n=22, 9.0%), without LSR from the start of the surgery (n=4, 1.7%), and with re-operation (n=15, 6.1%) and follow-up loss (n=4, 1.7%) were excluded. For the statistical analysis, patients were categorized into two groups according to the disappearance of their LSR before or after MVD.
  
  
  RESULTS
  Intra-operatively, the LSR was checked during facial electromyogram monitoring in 199 (81.5%) of the 244 patients. The mean follow-up duration was 40.9±6.9 months (range 25-51 months) in all the patients. Among them, the LSR disappeared after the decompression (Group A) in 128 (64.3%) patients; but in the remaining 71 (35.6%) patients, the LSR disappeared before the decompression (Group B). In the post-operative follow-up visits over more than one year, there were significant differences between the clinical outcomes of the two groups (p<0.05).
  
  
  CONCLUSIONS
  It was observed that the long-term clinical outcomes of the intra-operative LSR disappearance before and after MVD were correlated. Thus, this factor may be considered a prognostic factor of HFS after MVD.
authors.affiliation: Department of Neurosurgery, Cerebro-Vascular Center, Bongseng Memorial Hospital, Busan, Korea.
authors.forename: Min-Cheol
authors.initials: MC
authors.lastname: Kang
authors.forename: Yu-Seok
authors.initials: YS
authors.lastname: Choi
authors.forename: Hak-Ki
authors.initials: HK
authors.lastname: Choi
authors.forename: Sang-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Chang-Gu
authors.initials: CG
authors.lastname: Ghang
authors.forename: Chang-Hyun
authors.initials: CH
authors.lastname: Kim
keywords: Clinical outcome; Hemifacial spasm; Lateral spread response; Microvascular decompression