Diagnostic and therapeutic values of intraoperative electrophysiological neuromonitoring during resection of intradural extramedullary spinal tumors: a single-center retrospective cohort and meta-analysis

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With the advent of intraoperative electrophysiological neuromonitoring (IONM), surgical outcomes of various neurosurgical pathologies, such as brain tumors and spinal deformities, have improved. However, its diagnostic and therapeutic value in resecting intradural extramedullary (ID-EM) spinal tumors has not been well documented in the literature. The objective of this study was to summarize the clinical results of IONM in patients with ID-EM spinal tumors.


A retrospective patient database review identified 103 patients with ID-EM spinal tumors who underwent tumor resection with IONM (motor evoked potentials, somatosensory evoked potentials, and free-running electromyography) from January 2010 to December 2015. Patients were classified as those without any new neurological deficits at the 6-month follow-up (group A; n = 86) and those with new deficits (group B; n = 17). Baseline characteristics, clinical outcomes, and IONM findings were collected and statistically analyzed. In addition, a meta-analysis in compliance with the PRISMA guidelines was performed to estimate the overall pooled diagnostic accuracy of IONM in ID-EM spinal tumor resection.


No intergroup differences were discovered between the groups regarding baseline characteristics and operative data. In multivariate analysis, significant IONM changes (p < 0.001) and tumor location (thoracic vs others, p = 0.018) were associated with new neurological deficits at the 6-month follow-up. In predicting these changes, IONM yielded a sensitivity of 82.4% (14/17), specificity of 90.7% (78/86), positive predictive value (PPV) of 63.6% (14/22), negative predictive value (NPV) of 96.3% (78/81), and area under the curve (AUC) of 0.893. The diagnostic value slightly decreased in patients with schwannomas (AUC = 0.875) and thoracic tumors (AUC = 0.842). Among 81 patients who did not demonstrate significant IONM changes at the end of surgery, 19 patients (23.5%) exhibited temporary intraoperative exacerbation of IONM signals, which were recovered by interruption of surgical maneuvers; none of these patients developed new neurological deficits postoperatively. Including the present study, 5 articles encompassing 323 patients were eligible for this meta-analysis, and the overall pooled diagnostic value of IONM was a sensitivity of 77.9%, a specificity of 91.1%, PPV of 56.7%, and NPV of 95.7%.


IONM for the resection of ID-EM spinal tumors is a reasonable modality to predict new postoperative neurological deficits at the 6-month follow-up. Future prospective studies are warranted to further elucidate its diagnostic and therapeutic utility.

ABBREVIATIONS AUC = area under the curve; CEL = clinical evidence level; EBL = estimated blood loss; EEG = electroencephalography; EMG = electromyography; GTR = gross-total resection; ID-EM = intradural extramedullary; IONM = intraoperative neuromonitoring; MEP = motor evoked potential; NMJB = neuromuscular junction blockade; NPV = negative predictive value; PPV = positive predictive value; SSEP = somatosensory evoked potential.

Article Information

Correspondence Sheng-fu L. Lo: Johns Hopkins University School of Medicine, Baltimore, MD. larrylo@jhmi.edu.

INCLUDE WHEN CITING Published online March 1, 2019; DOI: 10.3171/2018.11.SPINE181095.

W.I. and J.C. contributed equally to this work.

Disclosures Mr. Casaos is an HHMI Medical Student Research Fellow. Dr. Theodore is a consultant to Globus Medical. Dr. Gokaslan receives non−study-related research support from AOSpine North America and honoraria from AO Foundation and is a shareholder of Spinal Kinetic as well as US Spine. Dr. Sciubba is a consultant to Medtronic, DePuy-Synthes, Stryker, NuVasive, K2M, Baxter, and Misonix. Dr. Witham receives non–study-related support from the Gordon and Marilyn Macklin Foundation as well as Eli Lilly and Co. Dr. Wolinsky is a consultant to Siemens and DePuy-Synthes. Dr. Lo receives non–study-related financial support from the AO Foundation and Chordoma Foundation.

© AANS, except where prohibited by US copyright law.



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    PRISMA flowchart depicting our Web-based literature search strategy. ED = extradural.

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    Overall pooled diagnostic value of intraoperative neuromonitoring in predicting postoperative neurological deficits at long-term follow-ups: sensitivity (A), specificity (B), PPV (C), and NPV (D).

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    Funnel plots describing logit event rates and standard errors of included studies (white dots) and imputed studies (black dots, indicating potential bias) as well as pooled diagnostic value (white rhomboid) and adjusted diagnostic value (black rhomboid, with imputed studies taken into consideration): sensitivity (A), specificity (B), PPV (C), and NPV (D).


  • 1

    Accadbled FHenry Pde Gauzy JSCahuzac JP: Spinal cord monitoring in scoliosis surgery using an epidural electrode. Results of a prospective, consecutive series of 191 cases. Spine (Phila Pa 1976) 31:261426232006

  • 2

    Berends HIJournée HLRácz Ivan Loon JHärtl RSpruit M: Multimodality intraoperative neuromonitoring in extreme lateral interbody fusion. Transcranial electrical stimulation as indispensable rearview. Eur Spine J 25:158115862016

  • 3

    Clark AJSafaee MChou DWeinstein PRMolinaro AMClark JP III: comparative sensitivity of intraoperative motor evoked potential monitoring in predicting postoperative neurologic deficits: nondegenerative versus degenerative myelopathy. Global Spine J 6:4524582016

  • 4

    Duval STweedie R: Trim and fill: a simple funnel-plot-based method of testing and adjusting for publication bias in meta-analysis. Biometrics 56:4554632000

  • 5

    Eseonu CIRincon-Torroella JReFaey KLee YMNangiana JVivas-Buitrago T: Awake craniotomy vs craniotomy under general anesthesia for perirolandic gliomas: evaluating perioperative complications and extent of resection. Neurosurgery 81:4814892017

  • 6

    Forster MTMarquardt GSeifert VSzelényi A: Spinal cord tumor surgery–importance of continuous intraoperative neurophysiological monitoring after tumor resection. Spine (Phila Pa 1976) 37:E1001E10082012

  • 7

    Ghadirpour RNasi DIaccarino CGiraldi DSabadini RMotti L: Intraoperative neurophysiological monitoring for intradural extramedullary tumors: why not? Clin Neurol Neurosurg 130:1401492015

  • 8

    Guo LQuiñones-Hinojosa AYingling CDWeinstein PR: Continuous EMG recordings and intraoperative electrical stimulation for identification and protection of cervical nerve roots during foraminal tumor surgery. J Spinal Disord Tech 19:37422006

  • 9

    Gutzwiller EMCabrilo IRadovanovic ISchaller KBoëx C: Intraoperative monitoring with visual evoked potentials for brain surgeries. J Neurosurg 130:6546602019

  • 10

    Hadley MNShank CDRozzelle CJWalters BC: Guidelines for the use of electrophysiological monitoring for surgery of the human spinal column and spinal cord. Neurosurgery 81:7137322017

  • 11

    Harel RSchleifer DAppel SAttia MCohen ZRKnoller N: Spinal intradural extramedullary tumors: the value of intraoperative neurophysiologic monitoring on surgical outcome. Neurosurg Rev 40:6136192017

  • 12

    Kaneko KKato YKojima TImajyo YTaguchi T: Intraoperative electrophysiologic studies on the functions of nerve roots involved in cervical dumbbell-shaped schwannoma and their clinical utility. J Spinal Disord Tech 19:5715762006

  • 13

    Kang HGwak HSShin SHWoo MKJeong IHYoo H: Monitoring rate and predictability of intraoperative monitoring in patients with intradural extramedullary and epidural metastatic spinal tumors. Spinal Cord 55:9069102017

  • 14

    Korn AHalevi DLidar ZBiron TEkstein PConstantini S: Intraoperative neurophysiological monitoring during resection of intradural extramedullary spinal cord tumors: experience with 100 cases. Acta Neurochir (Wien) 157:8198302015

  • 15

    Kothbauer KF: Intraoperative neurophysiologic monitoring for intramedullary spinal-cord tumor surgery. Neurophysiol Clin 37:4074142007

  • 16

    Kothbauer KFDeletis V: Intraoperative neurophysiology of the conus medullaris and cauda equina. Childs Nerv Syst 26:2472532010

  • 17

    Kreiner DSShaffer WOBaisden JGilbert TSummers JToton J: Diagnosis and Treatment of Degenerative Lumbar Spinal Stenosis. Burr Ridge, IL: North American Spine Society2011 (http://content.guidelinecentral.com/guideline/get/pdf/4230) [Accessed December 24 2018]

  • 18

    Lakomkin NMistry AMZuckerman SLLadner TKothari PLee NJ: Utility of intraoperative monitoring in the resection of spinal cord tumors: an analysis by tumor location and anatomical region. Spine (Phila Pa 1976) 43:2872942018

  • 19

    Luk KDHu YWong YWCheung KM: Evaluation of various evoked potential techniques for spinal cord monitoring during scoliosis surgery. Spine (Phila Pa 1976) 26:177217772001

  • 20

    Martirosyan NLFeuerstein JSTheodore NCavalcanti DDSpetzler RFPreul MC: Blood supply and vascular reactivity of the spinal cord under normal and pathological conditions. J Neurosurg Spine 15:2382512011

  • 21

    McCormick PCTorres RPost KDStein BM: Intramedullary ependymoma of the spinal cord. J Neurosurg 72:5235321990

  • 22

    Mehta AIMohrhaus CAHusain AMKarikari IOHughes BHodges T: Dorsal column mapping for intramedullary spinal cord tumor resection decreases dorsal column dysfunction. J Spinal Disord Tech 25:2052092012

  • 23

    Moher DLiberati ATetzlaff JAltman DG: Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Int J Surg 8:3363412010

  • 24

    Ng ZNg SNga VTeo KLwin SNing C: Intradural spinal tumors-review of postoperative outcomes comparing intramedullary and extramedullary tumors from a single institution’s experience. World Neurosurg 109:e229e2322018

  • 25

    Nuwer MREmerson RGGalloway GLegatt ADLopez JMinahan R: Evidence-based guideline update: intraoperative spinal monitoring with somatosensory and transcranial electrical motor evoked potentials. J Clin Neurophysiol 29:1011082012

  • 26

    Parney IFGoerss SJMcGee KHuston J 3rdPerkins WJMeyer FB: Awake craniotomy, electrophysiologic mapping, and tumor resection with high-field intraoperative MRI. World Neurosurg 73:5475512010

  • 27

    Quinones-Hinojosa AGulati MLyon RGupta NYingling C: Spinal cord mapping as an adjunct for resection of intramedullary tumors: surgical technique with case illustrations. Neurosurgery 51:119912072002

  • 28

    Resnick DKAnderson PAKaiser MGGroff MWHeary RFHolly LT: Electrophysiological monitoring during surgery for cervical degenerative myelopathy and radiculopathy. J Neurosurg Spine 11:2452522009

  • 29

    Rho YJRhim SCKang JK: Is intraoperative neurophysiological monitoring valuable predicting postoperative neurological recovery? Spinal Cord 54:112111262016

  • 30

    Sala FBricolo AFaccioli FLanteri PGerosa M: Surgery for intramedullary spinal cord tumors: the role of intraoperative (neurophysiological) monitoring. Eur Spine J 16 (Suppl 2):S130S1392007

  • 31

    Sala FDvorak JFaccioli F: Cost effectiveness of multimodal intraoperative monitoring during spine surgery. Eur Spine J 16 (Suppl 2):S229S2312007

  • 32

    Samuel NTetreault LSantaguida CNater AMoayeri NMassicotte EM: Clinical and pathological outcomes after resection of intramedullary spinal cord tumors: a single-institution case series. Neurosurg Focus 41(2):E82016

  • 33

    Scibilia ATerranova CRizzo VRaffa GMorelli AEsposito F: Intraoperative neurophysiological mapping and monitoring in spinal tumor surgery: sirens or indispensable tools? Neurosurg Focus 41(2):E182016

  • 34

    Shamji MFMaziak DEShamji FMGinsberg RJPon R: Circulation of the spinal cord: an important consideration for thoracic surgeons. Ann Thorac Surg 76:3153212003

  • 35

    Sutter MDeletis VDvorak JEggspuehler AGrob DMacdonald D: Current opinions and recommendations on multimodal intraoperative monitoring during spine surgeries. Eur Spine J 16 (Suppl 2):S232S2372007

  • 36

    Sutter MEggspuehler AGrob DJeszenszky DBenini APorchet F: The diagnostic value of multimodal intraoperative monitoring (MIOM) during spine surgery: a prospective study of 1,017 patients. Eur Spine J 16 (Suppl 2):S162S1702007

  • 37

    Verla TFridley JSKhan ABMayer RROmeis I: Neuromonitoring for intramedullary spinal cord tumor surgery. World Neurosurg 95:1081162016

  • 38

    Wang STian YLin XRen ZZhao YZhai J: Comparison of intraoperative neurophysiologic monitoring outcomes between cervical and thoracic spine surgery. Eur Spine J 26:240424092017

  • 39

    Wicks RTPradilla GRaza SMHadelsberg UCoon ALHuang J: Impact of changes in intraoperative somatosensory evoked potentials on stroke rates after clipping of intracranial aneurysms. Neurosurgery 70:111411242012

  • 40

    Xu RRitzl EKSait MSciubba DMWolinsky JPWitham TF: A role for motor and somatosensory evoked potentials during anterior cervical discectomy and fusion for patients without myelopathy: analysis of 57 consecutive cases. Surg Neurol Int 2:1332011




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