title: Reliability of intraoperative neurophysiological monitoring using motor evoked potentials during resection of metastases in motor-eloquent brain regions: clinical article.
abstract: OBJECTIVE
  Resection of gliomas in or adjacent to the motor system is widely performed using intraoperative neuromonitoring (IOM). For resection of cerebral metastases in motor-eloquent regions, however, data are sparse and IOM in such cases is not yet widely described. Since recent studies have shown that cerebral metastases infiltrate surrounding brain tissue, this study was undertaken to assess the value and influence of IOM during resection of supratentorial metastases in motor-eloquent regions.
  
  
  METHODS
  Between 2006 and 2011, the authors resected 206 consecutive supratentorial metastases, including 56 in eloquent motor areas with monitoring of monopolar direct cortically stimulated motor evoked potentials (MEPs). The authors evaluated the relationship between the monitoring data and the course of surgery, clinical data, and postoperative imaging.
  
  
  RESULTS
  Motor evoked potential monitoring was successful in 53 cases (93%). Reduction of MEP amplitude correlated better with postoperative outcomes when the threshold for significant amplitude reduction was set at 80% (only > 80% reduction was considered significant decline) than when it was set at 50% (> 50% amplitude reduction was considered significant decline). Evidence of residual tumor was seen on MR images in 28% of the cases with significant MEP reduction. No residual tumor was seen in any case of stable MEP monitoring. Moreover, preoperative motor deficit, recursive partitioning analysis Class 3, and preoperative radiotherapy were independent risk factors for a new surgery-related motor weakness (occurring in 64% of patients with and 11% of patients without radiotherapy, p > 0.01).
  
  
  CONCLUSIONS
  Continuous MEP monitoring provides reliable monitoring of the motor system and also influences the course of operation in resection of cerebral metastases. However, in establishing warning criteria, only an amplitude decline > 80% of the baseline should be considered significant.
authors.affiliation: Departments of Neurosurgery, Technische Universität München, Munich, Germany.
authors.forename: Sandro M
authors.initials: SM
authors.lastname: Krieg
authors.forename: Michael
authors.initials: M
authors.lastname: Schäffner
authors.forename: Ehab
authors.initials: E
authors.lastname: Shiban
authors.forename: Doris
authors.initials: D
authors.lastname: Droese
authors.forename: Thomas
authors.initials: T
authors.lastname: Obermüller
authors.forename: Jens
authors.initials: J
authors.lastname: Gempt
authors.forename: Bernhard
authors.initials: B
authors.lastname: Meyer
authors.forename: Florian
authors.initials: F
authors.lastname: Ringel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000503:physiopathology / Q000556:secondary* / Q000601:surgery*; D001943:Breast Neoplasms / Q000473:pathology; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005910:Glioma / Q000503:physiopathology / Q000556:secondary* / Q000601:surgery*; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009043:Motor Activity / Q000502:physiology; D019635:Neurosurgical Procedures; D012086:Reoperation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D012878:Skin Neoplasms / Q000473:pathology; D016896:Treatment Outcome