title: Intraoperative neurophysiology in tethered cord surgery: techniques and results.
abstract: BACKGROUND
  Intraoperative neurophysiologic monitoring (IOM) is nowadays extensively used to minimize neurological morbidity in tethered cord surgery. Our goal is to describe and discuss the standard IOM techniques used during these surgical procedures and to summarize our clinical experience using a multimodal IOM approach.
  
  
  METHODS
  Neurophysiological mapping of the conus-cauda is performed through direct stimulation of these structures and bilateral recording from segmental target muscles. While mapping identifies ambiguous neural structures, their functional integrity during surgery can be assessed by monitoring techniques only, such as somatosensory evoked potentials (SEPs), transcranial motor-evoked potentials (MEPs) from the limb muscles and anal sphincters, and the bulbocavernosus reflex (BCR).
  
  
  RESULTS
  Between 2002 and 2012, we performed 48 surgical procedures in 47 patients with a tethered cord secondary to a variety of spinal dysraphisms. The monitorability rate was 84 % for SEPs, 97 % for limb muscle MEPs, 74 % for the anal sphincter MEPs, and 59 % for the BCR. In all patients but one, SEP, MEP, and BCR remained stable during surgery. Postoperatively, two out of 47 patients presented a significant-though transient-neurological worsening. In six patients, an unexpected muscle response was evoked by stimulating tissue macroscopically considered as not functional.
  
  
  CONCLUSIONS
  Mapping techniques allow identifying and sparing functional neural tissue and vice versa to cut nonfunctional structures that may contribute to cord tethering. Monitoring techniques, MEP and BCR in particular, improve the reliability of intraoperative neurophysiology, though these may require a higher degree of neuromonitoring expertise. IOM minimizes neurological morbidity in tethered cord surgery.
authors.affiliation: Institute of Neurosurgery, Department of Neurosciences, University Hospital, Verona, Italy. francesco.sala@univr.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Sala
authors.forename: Giovanna
authors.initials: G
authors.lastname: Squintani
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Tramontano
authors.forename: Chiara
authors.initials: C
authors.lastname: Arcaro
authors.forename: Franco
authors.initials: F
authors.lastname: Faccioli
authors.forename: Carlo
authors.initials: C
authors.lastname: Mazza
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D019054:Evoked Potentials, Motor / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D007223:Infant; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods*; D008297:Male; D009436:Neural Tube Defects / Q000601:surgery*; D019635:Neurosurgical Procedures / Q000379:methods*