Intraoperative neurophysiological monitoring

Intraoperative neurophysiological monitoring

Intraoperative neurophysiological monitoring (IONM) or intraoperative neuromonitoring is the use of electrophysiological methods to monitor the functional integrity of certain neural structures (e.g., nerves, spinal cord, and parts of the brain) during surgery. The purpose of IONM is to reduce the risk to the patient of iatrogenic damage to the nervous system, and/or to provide functional guidance to the surgeon and anesthesiologist.

see Intraoperative neurophysiological monitoring indications.

see Intraoperative neurophysiological monitoring Anesthesia.

Evoked potentials:

Somatosensory evoked potentials (SSEP)

Motor evoked potential (MEP)

Brainstem auditory evoked potentials (BAEP)

Visual evoked potentials (VEP)

Electroencephalography (EEG)

Electromyography (EMG) .


Triggered electromyography.

see Intraoperative stimulation mapping.

Intraoperative neurophysiological monitoring case series.

Seidel K, Krieg SM. Special Topic Issue: Intraoperative Neurophysiological Monitoring. J Neurol Surg A Cent Eur Neurosurg. 2021 Jul;82(4):297-298. doi: 10.1055/s-0041-1731685. Epub 2021 Jul 14. PMID: 34261154.

Intraoperative neurophysiological monitoring for anterior cervical discectomy and fusion

Intraoperative neurophysiological monitoring for anterior cervical discectomy and fusion

Although Intraoperative neurophysiological monitoring has been shown to decrease the risk of neurological injury in deformity surgery, its utility in anterior cervical spine surgery (ACSS) remains controversial 1) 2) 3) 4) 5) 6)7) 8).

Proponents of intraoperative neurophysiological monitoring for ACSS claim that it improves patient safety and functional outcome whereas opponents refute this claim by citing increased cost and the lack of correlation between intraoperative neurophysiological monitoring abnormalities and postoperative neurological deficits especially with anterior cervical discectomy and fusions (ACDFs) 9) 10) 11) 12).

In a systematic review and meta-analysis from 2017, the risk of neurological injury after ACSS was low although procedures involving a corpectomy may carry a higher risk. For ACDFs, there is no difference in the risk of neurological injury with or without ION use. Unimodal ION has a higher specificity than multimodal ION and may minimize “subclinical” intraoperative alerts in ACSS 13)

A analysis of over 140,000 cases from the National Inpatient Sample data set, found that the use of intraoperative neurophysiological monitoringfor anterior cervical discectomy and fusion was not associated with a reduced rate of neurological complication14).



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Diab M, Smith AR, Kuklo TR. Neural complications in the surgical treatment of adolescent idiopathic scoliosis. Spine. 2007;32:2759–63.

Eggspuehler A, Sutter MA, Grob D, et al. Multimodal intraoperative monitoring during surgery of spinal deformities in 217 patients. Eur Spine J. 2007;16:S188–96.

Forbes HJ, Allen PW, Waller CS, et al. Spinal cord monitoring in scoliosis surgery. Experience with 1168 cases. J Bone Joint Surg Br. 1991;73:487–91.

Kamerlink JR, Errico T, Xavier S, et al. Major intraoperative neurologic monitoring deficits in consecutive pediatric and adult spinal deformity patients at one institution. Spine. 2010;35:240–5.

Nuwer MR, Emerson RG, Galloway G, et al. Evidence-based guideline update: intraoperative spinal monitoring with somato-sensory and transcranial electrical motor evoked potentials*. J Clin Neurophysiol. 2012;29:101–8.

Resnick DK, Choudhri TF, Dailey AT, et al. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 15: electrophysiological monitoring and lumbar fusion. J Neurosurg Spine. 2005;2:725–32.

Zhuang Q, Wang S, Zhang J, et al. How to make the best use of intraoperative motor evoked potential monitoring? Experience in 1162 consecutive spinal deformity surgical procedures. Spine. 2014;39:E1425–32.

Engler GL, Spielholz NJ, Bernhard WN, et al. Somatosensory evoked potentials during Harrington instrumentation for scoliosis. J Bone Joint Surg Am. 1978;60:528–32.

Epstein NE, Danto J, Nardi D. Evaluation of intraoperative somatosensory-evoked potential monitoring during 100 cervical operations. Spine. 1993;18:737–47.

Taunt CJ, Jr, Sidhu KS, Andrew SA. Somatosensory evoked potential monitoring during anterior cervical discectomy and fusion. Spine. 2005;30:1970–2.

Traynelis VC, Abode-Iyamah KO, Leick KM, et al. Cervical decompression and reconstruction without intraoperative neurophysiological monitoring. J Neurosurg Spine. 2012;16:107–13.

Ajiboye RM, Zoller SD, Sharma A, Mosich GM, Drysch A, Li J, Reza T, Pourtaheri S. Intraoperative Neuromonitoring for Anterior Cervical Spine Surgery: What Is the Evidence? Spine (Phila Pa 1976). 2017 Mar 15;42(6):385-393. doi: 10.1097/BRS.0000000000001767. Review. PubMed PMID: 27390917; PubMed Central PMCID: PMC5552368.

Badhiwala JH, Nassiri F, Witiw CD, Mansouri A, Almenawer SA, da Costa L, Fehlings MG, Wilson JR. Investigating the utility of intraoperative neurophysiological monitoring for anterior cervical discectomy and fusion: analysis of over 140,000 cases from the National (Nationwide) Inpatient Sample data set. J Neurosurg Spine. 2019 Mar 29:1-11. doi: 10.3171/2019.1.SPINE181110. [Epub ahead of print] PubMed PMID: 30925481.

Intraoperative Neurophysiological Monitoring in Spine Surgery

Intraoperative Neurophysiological Monitoring in Spine Surgery

The objective of a systematic literature review was to evaluate if intraoperative neurophysiological monitoring (IONM) can prevent neurological injury during spinal operative surgical procedures.

IONM seems to have presumable positive effects in identifying neurological deficits. However, the role of IONM in the decrease of new neurological deficits remains unclear.

Using the Preferred Reporting Items for Systematic Reviews and MetaAnalyses (PRISMA) guidelines for systematic reviews and Meta-analysis, Daniel et al., from São Paulo, Brazil, reviewed clinical comparative study who evaluate the rate of new neurological events in patients who had a spinal surgery with and without IONM. Studies were then classified according to their level of evidence. Methodological quality was assessed according to methodological index for non-randomized studies instrument.

Six studies were evaluated comparing neurological events with and without IONM use by the random effects model. There was a great statistical heterogeneity. The pooled odds ratio (OR) was 0.72 {0.71; 1.79}, P = 0.4584. A specific analysis was done for two studies reporting the results of IONM for spinal surgery of intramedullary lesions. The OR was 0.1993 (0.0384; 1.0350), P = 0.0550.

IONM did not result into fewer neurological events with the obtained evidence of the included studies. For intramedullary lesions, there was a trend to fewer neurological events in patients who underwent surgery with IONM. Further prospective randomized studies are necessary to clarify the indications of IONM in spinal surgery 1).


Daniel JW, Botelho RV, Milano JB, Dantas FR, Onishi FJ, Neto ER, Bertolini EF, Borgheresi MAD, Joaquim AF. Intraoperative Neurophysiological Monitoring in Spine Surgery: A Systematic Review and Meta-Analysis. Spine (Phila Pa 1976). 2018 Aug;43(16):1154-1160. doi: 10.1097/BRS.0000000000002575. PubMed PMID: 30063222.
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