title: Facial nerve palsy after vestibular schwannoma surgery: dynamic risk-stratification based on continuous EMG-monitoring.
abstract: OBJECTIVE
  A-trains are a pathological pattern in intraoperative EMG-monitoring. Traintime, a parameter calculated by automated EMG-analysis, quantifies A-train activity. Its extent is associated with the degree of postoperative facial nerve palsy. However, false positive results have been observed. A systematic flaw in automated analysis was hypothesized.
  
  
  METHODS
  Facial nerve EMG-data from 79 patients undergoing vestibular schwannoma surgery were analyzed visually. Automated traintime was compared with these results. The progressive risk for postoperative paresis was calculated with respect to traintime (visual and automated).
  
  
  RESULTS
  Automated analysis identified a small (1.46%), but highly representative fraction of overall A-train activity: Pearson's correlation coefficient between both values was 0.944 (p<0.001). Both were correlated with clinical outcome in a highly significant way (p<0.001) with Spearman's Rho 0.592 (automated) and 0.563 (visual). Progressive risk development was visualized as an inverse sigmoid curve with traintime on a logarithmic scale.
  
  
  CONCLUSIONS
  Automated traintime is a representative and reliable expression for overall A-train activity. As risk-development is complex, rigid thresholds are problematic.
  
  
  CONCLUSIONS
  Individual risk for postoperative palsy can be estimated on the basis of the calculated curve presented. This approach is of higher practical value than a rigid (and low) threshold.
authors.affiliation: Department of Neurosurgery, University of Halle, Ernst-Grube-Str. 40, 06097 Halle, Germany. Electronic address: julian.prell@medizin.uni-halle.de.
authors.forename: Julian
authors.initials: J
authors.lastname: Prell
authors.affiliation: Department of Neurosurgery, University of Halle, Ernst-Grube-Str. 40, 06097 Halle, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Strauss
authors.affiliation: Department of Neurosurgery, University of Halle, Ernst-Grube-Str. 40, 06097 Halle, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Rachinger
authors.affiliation: Department of Neurosurgery, University of Halle, Ernst-Grube-Str. 40, 06097 Halle, Germany.
authors.forename: Alex
authors.initials: A
authors.lastname: Alfieri
authors.affiliation: Department of Neurosurgery, University of Halle, Ernst-Grube-Str. 40, 06097 Halle, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Scheller
authors.affiliation: Department of Neurosurgery, University of Halle, Ernst-Grube-Str. 40, 06097 Halle, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Herfurth
authors.affiliation: Department of Neurosurgery, University of Halle, Ernst-Grube-Str. 40, 06097 Halle, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rampp
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004576:Electromyography; D005154:Facial Nerve / Q000503:physiopathology; D005158:Facial Paralysis / Q000209:etiology* / Q000503:physiopathology / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009464:Neuroma, Acoustic / Q000150:complications / Q000601:surgery*; D019635:Neurosurgical Procedures / Q000009:adverse effects; D018570:Risk Assessment
keywords: A-train; EMG; Facial nerve; Neurophysiologic monitoring; Traintime; Vestibular schwannoma