title: Somatosensory evoked potential monitoring during endoscopic endonasal approach to skull base surgery: analysis of observed changes.
abstract: BACKGROUND
  Intraoperative neurophysiological monitoring, including upper- and lower-extremity somatosensory evoked potentials (SSEPs), has been used to identify and prevent injury to neurovascular structures during conventional skull base surgery. The expanded endonasal approach (EEA) is a novel minimally invasive approach to skull base surgery. However, it carries the risk of injury to neurovascular structures, including the internal carotid artery, anterior cerebral artery, and cranial nerves.
  
  
  OBJECTIVE
  To evaluate the value of SSEP monitoring to predict and/or prevent neurovascular deficits during EEA to skull base surgery.
  
  
  METHODS
  We retrospectively identified 999 consecutive patients who had intraoperative neurophysiological monitoring during EEA skull base surgery at our institution. A total of 976 patients had SSEP monitoring and a documented postoperative neurological examination.
  
  
  RESULTS
  The incidence of changes in SSEP during the procedure was 20 of 976 (2%). The incidence of new postoperative neurological deficits was 5 of 976 (0.5%). The positive and negative predictive values of SSEPs during EEA to predict neurovascular deficits were 80.00% and 99.79%, respectively.
  
  
  CONCLUSIONS
  Intraoperative SSEP monitoring was able to identify impending risk to neurovascular structures to prevent permanent postoperative neurological deficits. We advocate a comprehensive approach to neurophysiological monitoring during EEAs, including SSEPs, spontaneous and triggered electromyography of the cranial nerves III through XII, brainstem auditory evoked potentials, and electroencephalogram, depending on the surgical approach and location of the neural structures at risk.
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA. thirumalapd@upmc.edu
authors.forename: Parthasarathy D
authors.initials: PD
authors.lastname: Thirumala
authors.forename: Amin B
authors.initials: AB
authors.lastname: Kassasm
authors.forename: Miguel
authors.initials: M
authors.lastname: Habeych
authors.forename: Kelley
authors.initials: K
authors.lastname: Wichman
authors.forename: Yue-Fang
authors.initials: YF
authors.lastname: Chang
authors.forename: Paul
authors.initials: P
authors.lastname: Gardner
authors.forename: Daniel
authors.initials: D
authors.lastname: Prevedello
authors.forename: Carl
authors.initials: C
authors.lastname: Snyderman
authors.forename: Ricardo
authors.initials: R
authors.lastname: Carrau
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Crammond
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Balzer
mesh_terms: D004576:Electromyography / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000009:adverse effects / Q000379:methods; D016343:Monitoring, Intraoperative / Q000379:methods*; D044583:Neuroendoscopy / Q000009:adverse effects / Q000379:methods; D011183:Postoperative Complications / Q000517:prevention & control; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D019291:Skull Base / Q000601:surgery*