www.elsevier.com/locate/semss Available online at www.sciencedirect.com Intraoperative neurophysiologic monitoring in high-grade spondylolisthesis Philip K. Louie, MD a , A. Jay Khanna, MD, MBA b , Hamid Hassanzadeh, MD c,n , and Khaled M. Kebaish, MD b a Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL b Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, MD c Department of Orthopaedic Surgery, University of Virginia, P.O. Box 800159, Charlottesville, VA 22908 abstract Intraoperative neurophysiologic monitoring during high-grade spondylolisthesis surgery has enabled surgeons to expand operative treatment while preventing iatrogenic nerve injuries. Studies show improvement in the safety profile of a multimodal approach to intraoperative neuromonitoring in high-grade spondylolisthesis procedures to prevent neurologic damage. Electromyography-inclusive monitoring, with or without additional monitoring techniques (somatosensory evoked potentials and motor evoked potentials), successfully alerts surgical teams to potential intraoperative nerve injury. The value of intraoperative neuromonitoring is high in high- grade spondylolisthesis reduction procedures, screw placement, and L5 vertebrectomies, allowing for immediate corrective maneuvers in the form of hemodynamic stabilization and suspension of manipulations. & 2015 Published by Elsevier Inc. 1. Introduction Intraoperative neurophysiologic monitoring has gained pop- ularity in the operative fixation for high-grade spondylolis- thesis (HGS). For the past 2–3 decades, the multimodal use of neuromonitoring has evolved with the methods of spinal deformity correction associated with HGS. Improvements in the sensitivity and specificity of intraoperative neurophysio- logic monitoring to neuromuscular changes have enabled surgeons to expand operative treatment options while pre- venting iatrogenic injuries that can cause irreversible nerve damage. Surgical correction of HGS poses a risk of neurologic injury from degenerative changes and ligamentous laxity seen in degenerative spondylolisthesis, the close proximity of the spinal cord to the pathologic site in traumatic spondylolis- thesis, and the aberrant anatomy observed in congenital spondylolisthesis. Numerous surgical treatment options have been described in the literature with goals of relieving pain, resolving neurologic dysfunction, obtaining solid arthrodesis, and restoring sagittal balance and appearance. 1–6 Procedures include posterior in situ arthrodesis with or without lam- inectomy, reduction followed by posterior fixation with or without interbody fusion, instrumented fusions without reduction, L5 vertebrectomy (Gaines procedure), and com- bined anterior–posterior procedures. 4 The risk of neurologic injury is compounded by intraoperative nerve root compres- sion, nerve root strain, direct trauma from dural manipula- tions, expansion of hemostatic agents, and small hematomas. 7–10 Neurologic complications have been reported in 3À43% 1–3,8,11–15 of patients undergoing the aforementioned operations. Although most of these complications are tem- porary, permanent neurologic damage and cauda equina syndrome have been reported. 10,13,16,17 Early detection of iatrogenic neurologic injury during spinal deformity correction, including for HGS, dates back to 1973 with the Stagnara wake-up test. 18 However, there were limitations to these efforts, including many false http://dx.doi.org/10.1053/j.semss.2015.04.007 1040-7383/& 2015 Published by Elsevier Inc. n Corresponding author. E-mail address: hh14@virginia.edu (H. Hassanzadeh). S EMIN S PINE S URG 27 (2015) 217 – 221