The role of intraoperative neurophysiological monitoring in spinal surgery: A focused evidence review (2015–2025)

Abstract

Background:

Intraoperative neurophysiology monitoring (IONM) has become a critical tool in spinal surgery, providing real-time feedback on neural integrity to help prevent postoperative neurological deficits. Despite its growing use, there remains variability in evidence regarding its effectiveness across diverse surgical contexts.

Methods:

A systematic search of PubMed, Embase, Scopus, Cochrane Library, ClinicalTrials.gov, and Google Scholar identified studies assessing IONM in spine surgery. Risk of bias assessment was performed using ROBINS I tool.

Results:

Our review found that IONM is associated with lower rates of neurological injury in controlled cohorts, although larger registries showed higher crude deficit rates confounded by surgical complexity. Intraoperative alerts were common but usually transient, enabling timely corrective actions. Diagnostic accuracy was high, with excellent specificity and negative predictive value, supporting IONM’s role as an early-warning tool.

Conclusion:

IONM enhances patient safety in spinal surgery by enabling early detection of neural injury and minimizing postoperative neurological deficits. Evidence supports the use of multimodal IONM with standardized protocols to improve neurological outcomes.

INTRODUCTION

Intra-operative neurophysiology monitoring (IONM) has increasingly become an integral component of spine surgery that enhances patient safety by providing real-time assessment of neural function during operative procedures.[2,8] IONM techniques include somatosensory-evoked potentials (SSEPs), transcranial motor evoked potentials (MEPs), electromyography, and pedicle screw stimulation.[5] These modalities enable the detection of impending neurological injury and facilitate timely surgical intervention to prevent permanent deficits.[8] Further, multimodal IONM outperforms single modality techniques, improving early detection of neurological compromise during complex spinal procedures (i.e., deformity correction and intramedullary tumor resection).[5] Here, we reviewed IONM’s current role in preventing neurological injury.

MATERIALS AND METHODS

Databases and keywords used in literature search

A systematic literature search was performed across PubMed, Embase, Scopus, Cochrane Library, ClinicalTrials.gov, and Google Scholar for studies published between 2015 and 2025. Keywords included “intraoperative neurophysiology monitoring,” “IONM,” “spinal surgery,” and “neurological outcomes.” Studies were included if they assessed IONM during spinal procedures, reported neurological or diagnostic outcomes, and involved adult human subjects. Case reports, letters, and pediatric studies were excluded. The ROBINS-I tool guided qualitative bias assessment, and a narrative synthesis approach was used [Figure 1].

Figure 1:

Risk of bias per study (RoBINS-I). Domain-level risk of bias assessment for each included study using the RoBINS-I tool. Domains: D1 - Bias due to confounding; D2 - Bias due to selection of participants; D3 - Bias in classification of interventions; D4 - Bias due to deviations from intended interventions; D5 - Bias due to missing data; D6 - Bias in measurement of outcomes; D7 - Bias in selection of the reported result.

RESULTS

Primary outcome: Postoperative neurological deficit

Across comparative cohorts, the frequency of postoperative neurological deficits varied by study and surgical complexity [Table 1]. Mirza et al.[5] (2022) reported postoperative deficits in 1.15% of cases with IONM. Burkhard et al. [1] (2025) observed motor deficits in 5.5% of patients undergoing posterior lumbar fusion with SSEPs and MEPs. Chen et al. [2] (2015) reported neurological deficits in 46% of scoliosis or kyphosis cases monitored with transcranial electrical stimulation-MEP (TES-MEP) and cortical somatosensory evoked potentials (CSEPs). Chen et al. [3] (2022) documented deficits in 54.1% of severe spinal deformity cases monitored with MEP, SSEP, and descending neurogenic evoked potentials. Lieberman et al. [4] (2019) and Sutter et al. [6] (2019) reported postoperative deficits of 4.6% and 4.2%, respectively, during deformity or miscellaneous spine surgeries. In traumatic spine injury, Ushirozako et al. [7] (2023) noted that 50% of patients had preoperative motor deficits, with postoperative outcomes strongly linked to IONM-guided interventions. Ushirozako et al. [8] (2019) reported 4.8% postoperative deficits in adult deformity, tumor, and ossification of the posterior longitudinal ligament cases monitored with transcranial-MEP (Tc-MEP) [Table 2].

Table 1:

Study characteristics.

Table 2:

Summary of included studies.

Intraoperative detection and IONM alerts

IONM alert rates varied across procedures and monitoring modalities [Table 3]. Mirza et al.[5] reported alerts in 5.8% of cases, largely transient with no postoperative impact. Burkhard et al. [1] observed alerts in 32.7% of lumbar fusion cases, although only a minority translated into deficits. Chen et al. [2,3] (2015; 2022) reported alert rates of 15% and 36%, respectively, mostly resolved after intraoperative adjustments. Lieberman et al. [4] reported variable alert frequencies, while Sutter et al.[6] observed alerts in 33.3% of patients. Ushirozako et al. [7,8] (2019; 2023) reported 14.2% and 8% alerts, highlighting differences based on surgical complexity and preoperative deficits.

Table 3:

Summary of diagnostic accuracy and neurological outcomes.

Corrective actions with IONM alerts

Alerts generally prompted immediate interventions, including reduction of retraction, patient repositioning, or anesthetic adjustments. Most alerts were transient, and only a minority were associated with new postoperative deficits, emphasizing the importance of timely intraoperative response.

Diagnostic accuracy of IONM

Stable IONM reliably predicted the absence of postoperative deficits [Table 3]. Mirza et al.[5] reported sensitivity 75%, specificity 97.6%, positive predictive value 60%, and negative predictive value 98.8%. Burkhard et al. [1] showed low sensitivity (13.6%) but high specificity (96%) for postoperative deficits. Chen et al. [2] (2015) demonstrated high sensitivity (100%) and specificity (96.5%) with TESMEP and CSEP, whereas Lieberman et al. [4] reported Tc-MEP sensitivity of 96% and specificity of 97%. These findings confirm that IONM is highly reliable for detecting intraoperative neurological compromise, especially when multimodal monitoring is used.

Secondary outcomes

IONM was generally safe, with no significant monitoring-related complications reported. Data on length of stay, reoperation, blood loss, or anesthesia time were inconsistently reported across studies.

DISCUSSION

The present narrative review consolidates evidence evaluating the efficacy and safety of intra-operative neurophysiology monitoring (IONM) in spinal surgery. Across the included studies, IONM was consistently associated with reduced postoperative neurological deficits and improved intraoperative detection of neural compromise, particularly in complex procedures such as spinal deformity correction, tumor resection, and traumatic spine stabilization [Tables 1-3].

Postoperative neurological deficits varied by procedure type and monitoring strategy. Mirza et al. (2022)[5] reported a low incidence of deficits (1.15%) with combined SSEP and MEP monitoring, while Burkhard et al. [1] (2025) observed 5.5% motor deficits in posterior lumbar fusion. Higher rates were noted in extensive deformity surgeries (Chen et al., 2015: 46%; Chen et al., 2022: 54.1%)[2,3] reflecting inherent procedural risks. Lieberman et al. [4] (2019) and Sutter et al. (2019)[6] reported deficits of 4–5% in deformity and miscellaneous spine surgeries. In traumatic spine injury, Ushirozako et al. (2023) noted that preoperative motor deficits influenced postoperative outcomes, with IONM facilitating intraoperative corrective interventions.[7] Collectively, these data demonstrate that IONM contributes to neurological protection, particularly when multimodal strategies are employed.

IONM alerts were variably reported, ranging from 5.8% (Mirza et al.)[5] to 36% (Chen et al., 2022),[3] with most events transient and reversible upon intraoperative intervention. Alerts prompted corrective measures including adjustment of retraction, repositioning, or modulation of anesthetic depth.[1,3] Only a minority of alerts were associated with postoperative deficits, emphasizing the importance of timely intraoperative response and reinforcing the role of IONM as a sensitive early-warning system rather than a definitive diagnostic tool.

Diagnostic accuracy data support the reliability of IONM for predicting postoperative neurological function.[4] Stable intraoperative signals were strongly predictive of intact postoperative outcomes, reflected in high specificity and negative predictive values. Mirza et al. reported a specificity of 97.6% and negative predictive value of 98.8%,[5] while Chen et al. (2015)[2] demonstrated 100% sensitivity and 96.5% specificity with TES-MEP and CSEP. Lieberman et al. similarly reported high sensitivity (96%) and specificity (97%) for Tc-MEP.[4] These findings highlight the importance of multimodal monitoring to maximize detection efficiency and minimize false negatives.

Secondary outcomes were inconsistently reported but generally indicated favorable safety profiles. No significant monitoring-related complications were noted, and hospital stay, reoperation rates, and anesthesia time were largely unaffected. These findings underscore the overall safety of IONM while emphasizing its clinical utility in preventing costly neurological complications.

Clinical and research implications

This review confirms that IONM significantly enhances neurological safety in spinal surgery. Across multiple study designs, IONM demonstrated strong predictive reliability, with stable signals accurately indicating postoperative neurological integrity. Transient alerts, when promptly addressed, prevented permanent deficits in most cases. These findings underscore IONM’s value as an early-warning system rather than a binary diagnostic test.

Limitations

This review is limited by the heterogeneity of included studies, which span diverse surgical procedures and monitoring modalities. Most data derive from retrospective or single-center cohorts, and standardized definitions of alerts or neurological deficits were inconsistently applied. In addition, publication bias cannot be excluded, as studies demonstrating benefit are more likely to be reported. Nevertheless, the included evidence consistently supports the role of multimodal IONM in enhancing neurological safety.

CONCLUSION

The evidence supports IONM as a reliable and safe adjunct in spinal surgery, providing both predictive value for postoperative neurological outcomes and actionable intraoperative alerts. Multimodal strategies are particularly effective in high-risk or complex procedures, reinforcing the adoption of IONM to optimize patient safety and surgical success.

Ethical approval:

Institutional review board approval is not required.

Declaration of patient consent:

Patient’s consent is not required as there are no patients in this study.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.