title: The value of intraoperative neurophysiological monitoring for microsurgical removal of conus medullaris lipomas: a 12-year retrospective cohort study.
abstract: BACKGROUND
  Lipomas in the lower spinal canal can lead to progressive neurological deficits, so they may have to be surgically removed. Intraoperative neurophysiological monitoring serves to minimize the morbidity of the surgical procedure. However, so far there are no evidence-based recommendations which type of monitoring procedure or combination of procedures to choose.
  
  
  METHODS
  The aim of this study was to evaluate the feasibility and value of various intraoperative monitoring techniques: motor and sensory evoked potentials (MEP, SEP), free-running and triggered electromyography (EMG). Thirty cases of spinal lipomas of the Conus medullaris (dorsal Type A: 20.0%; caudal Type B: 33.3%; transitional Type C: 46.7%) were retrospectively evaluated over a 12-year period.
  
  
  RESULTS
  The patients were mostly pediatric and suffered from persistent pain (73.3%), pareses (56.7%), sensory deficits (43.4%), and/or urogenital dysfunctions (60.0%). SEPs were successfully evoked in 66.7% of cases, MEPs in 86.7% of cases, and EMGs in 100%. MEP alterations correlated with direct mechanical maneuvers in the operating site. SEP changes correlated mostly with physiological events, such as rinsing/cooling of the operating site. Spike-, burst- or tonic train-activity was found in the free-running EMG that occurred only with certain manipulation patterns. Irreversible MEP changes and signal loss in the triggered EMG correlated with post-operative deficits.
  
  
  CONCLUSIONS
  The results of this study showed, that intraoperative monitoring could be considered a helpful tool during lipoma tumor surgery near the Conus medullaris. Most reliable results were obtained from transcranial MEPs, free-running EMGs, and triggered EMGs. That's why the authors favor a routine set-up consisting of at least these three techniques, as this enables mapping at the beginning of the operation, continuous functional testing during surgery, and prognosis of the post-operative symptomology.
authors.affiliation: Zentrum für Wirbelsäulenchirurgie und Neurotraumatologie, DRK Kliniken Berlin Westend, Spandauer Damm 130, Berlin, 14050, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Suess
authors.affiliation: Zentrum für Wirbelsäulenchirurgie und Neurotraumatologie, DRK Kliniken Berlin Westend, Spandauer Damm 130, Berlin, 14050, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Mularski
authors.affiliation: Neurochirurgische Klinik, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Czabanka
authors.affiliation: Interdisziplinäres Wirbelsäulenzentrum, Vivantes Auguste-Viktoria-Klinikum, Berlin, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Cabraja
authors.affiliation: Neurochirurgie, Vivantes Klinikum im Friedrichshain, Berlin, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Hammersen
authors.affiliation: Abteilung für Neurochirurgie, Schlosspark-Klinik, Berlin, Germany.
authors.forename: Theodoros
authors.initials: T
authors.lastname: Kombos
keywords: Conus medullaris; Intraoperative monitoring; Microneurosurgery; Neurophysiological monitoring; Spinal lipoma