Utilization of intraoperative neuromonitoring throughout the United States over a recent decade: an analysis of the nationwide inpatient sample

New frontiers in intraoperative neurophysiologic monitoring: a narrative review

Background and Objective

Neurological insults during surgery arise from anatomic and/or physiologic perturbations. Intraoperative neurophysiologic monitoring (IONM) fills a critical role of ensuring that any neurological insults during certain surgical procedures are caught in real-time to prevent patient harm. IONM provides immediate feedback to the surgeon and anesthesiologist about the need for an intervention to prevent a neurologic deficit postoperatively. As important as it seems to have IONM available to any patient having surgery where a neurological injury is possible, the truth is that IONM is unavailable to large swaths of people around the world. This review is intended to bring attention to all of the ways IONM is critically important for a variety of surgeries and highlight the barriers preventing most patients around the world from benefiting from the technology. Expansion of IONM to benefit patients from all over the world is the new frontier.

Methods

We searched all English language original papers and reviews using Embase and MEDLINE/PubMed databases published from 1995 to 2022. Different combinations of the following search terms were used: intraoperative neuromonitoring, neurosurgery, low-income countries, cost, safety, and efficacy.

Key Content and Findings

We describe common IONM modalities used during surgery as well as explore barriers to implementation of IONM in resource-limited regions. Additionally, we describe ongoing efforts to establish IONM capabilities in new locations around the world.

Conclusions

In this paper, we performed a review of the literature on IONM with an emphasis on the basic understanding of clinical applications and the barriers for expansion into resource-limited settings. Finally, we provide our interpretation of "new frontiers" in IONM quite literally facilitating access to the tools and education so a hospital in Sub-Saharan Africa can incorporate IONM for their high-risk surgeries.

Lumbar Fusion for Active Duty Service Members Performed at an Overseas Military Treatment Facility: A 2-Year Retrospective Analysis

INTRODUCTION

Among U.S. Military active duty service members, low back pain (LBP) and lumbar radiculopathy are common causes of disability and effect job performance and readiness and can lead to medical separation from the military. Among surgical therapies, lumbar fusion is an option in select cases; however, elective lumbar fusion performed while serving overseas has not been studied extensively.

MATERIALS AND METHODS

A retrospective analysis of a prospectively collected surgical database from an overseas military treatment facility (MTF) over a 2-year period (2019-2021) was queried. Patient and procedural data were collected to include single and 2-level lumbar fusion, indications for surgery, military rank, age, tobacco use, pre- and postoperative Visual Analog Scale (VAS) scores for pain, and the presence of radiographic fusion after surgery. Chi-square and Student's t-test analyses were performed to identify variables associated with return to full duty.

RESULTS

A total of 21 patients underwent lumbar fusion with an average follow-up of 303.2 days (110-832 days). Eleven (52.4%) were able to return to full duty without restriction. Four (19%) patients ultimately required medical separation from the military, and six (28.6%) remained in a partial or limited duty status. Three (14.3%) patients required tour curtailment and return from overseas duty prematurely. Older age (40.2 ± 5.9 years), rank of E7 or greater, and reduction in VAS of 50% postoperatively were all associated with return to full unrestricted active duty. Three surgical complications occurred; all patients were able to recover overseas within a 3-month postoperative period.

CONCLUSIONS

Low back pain (LBP) and lumbar radiculopathy may ultimately require treatment with instrumented lumbar fusion and decompression. In this series, we demonstrate that overseas duty with treatment at a community-sized MTF does not preclude this therapy and should be considered among treatment options.

Intraoperative neuromonitoring in spine surgery: large database analysis of cost-effectiveness

BACKGROUND

Given the increased attention to functional improvement in spine surgery as it relates to activities of daily living and cost, it is critical to fully understand the health care economic impact of enabling technologies. The use of intraoperative neuromonitoring (IOM) during spine surgery has long been controversial. Questions pertaining to utility, medico-legal considerations, and cost-effectiveness continue to be unresolved. The purpose of this study is to determine the cost-effectiveness by assessing quality-of-life due to adverse events averted, decreased postoperative pain, decreased revision rates, and improved patient reported outcomes (PROs).

METHODS

The study patient population was extracted from a large multicenter database collected by a single, national IOM provider. Over 50,000 patient charts were abstracted and included in this analysis. The analysis was conducted in accordance with the second panel on cost-effectiveness health and medicine. Health-related utility was derived from questionnaire answers and expressed in quality-adjusted life years (QALYs). Both cost and QALY outcomes were discounted at a yearly rate of 3% to reflect their present value. Cost-effectiveness was calculated as the incremental cost-effectiveness ratio (ICER) for IOM. A value under the commonly accepted United States-based willingness-to-pay (WTP) threshold of $100,000 per QALY was considered cost-effective. Scenario (including litigation), probabilistic (PSA), and threshold sensitivity analyses were conducted to determine model discrimination and calibration.

RESULTS

The primary time horizon used to estimate cost and health utility was 2-years following index surgery. On average, index surgery for patients with IOM costs are approximately $1,547 greater than non-IOM cases. The base case assumed an inpatient Medicare population however multiple outpatient and payer scenarios were assessed in the sensitivity analysis. From a health system perspective IOM is cost-effective, yielding better utilities but at a higher cost than the non-IOM strategy (ICER $60,734 per QALY). From a societal perspective the IOM strategy was dominant, suggesting that better outcomes were achieved at less cost. Except for an entirely privately insured population, alternative scenarios such as, outpatient and a 50:50 Medicare/privately insured population sample also demonstrated cost-effectiveness. Notably, IOM benefits were unable to overcome the sheer costs associated many litigation scenarios, but the data was severely limited. In the 5,000 iteration PSA, at a WTP of $100,000, 74% of simulations using IOM were cost-effective.

CONCLUSIONS

The use of IOM in spine surgery is cost-effective in most scenarios examined. In the emerging and rapidly expanding field of value-based medicine, there will be an increased demand for these analyses, ensuring surgeons are empowered to make the best, most sustainable solutions for their patients and the health care system.

Intraoperative Triggered Electromyography for Pedicle Screw Placement Under Spinal Anesthesia: A Preliminary Report

BACKGROUND

Triggered electromyography (tEMG) is an intraoperative neuromonitoring technique used to assess pedicle screw placement during instrumented fusion procedures. Although spinal anesthesia is a safe alternative to general anesthesia in patients undergoing lumbar fusion, its use may potentially block conduction of triggered action potentials or may require higher threshold currents to elicit myotomal responses when using tEMG. Given the broad utilization of tEMG for confirmation of pedicle screw placement, adoption of spinal anesthesia may be hindered by limited studies of its use alongside tEMG.

OBJECTIVE

To investigate whether spinal anesthesia affects the efficacy of tEMG, we compare the baseline spinal nerve thresholds during lumbar fusion procedures under general vs spinal anesthesia.

METHODS

Twenty-three consecutive patients (12 general and 11 spinal) undergoing single-level transforaminal lumbar interbody fusion were included in the study. Baseline nerve threshold was determined through direct stimulation of the spinal nerve using tEMG.

RESULTS

Baseline spinal nerve threshold did not differ between the general and spinal anesthesia cohorts (3.25 ± 1.14 vs 3.64 ± 2.16 mA, respectively; P = .949). General and spinal anesthesia cohorts did not differ by age, body mass index, American Society of Anesthesiologists score status, or surgical indication.

CONCLUSION

We report that tEMG for pedicle screw placement can be safely and effectively used in procedures under spinal anesthesia. The baseline nerve threshold required to illicit a myotomal response did not differ between patients under general or spinal anesthesia. This preliminary finding suggests that spinal anesthetic blockade does not contraindicate the use of tEMG for neuromonitoring during pedicle screw placement.

Utilization Trends of Intraoperative Neuromonitoring for Anterior Cervical Discectomy and Fusion in New York State

STUDY DESIGN

Retrospective cohort analysis.

OBJECTIVE

To elucidate trends in the utilization of intraoperative neuromonitoring (IONM) during anterior cervical discectomy and fusion (ACDF) procedures in NY state using the Statewide Planning and Research Cooperative System and to determine if utilization of IONM resulted in a reduction in postoperative neurological deficits.

SUMMARY OF BACKGROUND DATA

IONM has been available to spinal surgeons for several decades. It has become increasingly prevalent in all facets of spinal surgery including elective ACDF procedures. The utility of IONM for preventing a neurological deficit in elective spine procedures has recently been called into question.

MATERIALS AND METHODS

The Statewide Planning and Research Cooperative System database were accessed to perform a retrospective cohort study comparing monitored versus unmonitored ACDF procedures between 2007 and 2018 as defined by the International Classification of Disease-9 and 10 Procedural Coding System (ICD-9 PCS, ICD-10 PCS) codes. Patient demographics, medical history, surgical intervention, pertinent in-hospital events, and urban versus rural medical centers (as defined by the United States Office of Management and Budget) were recorded. Propensity-score-matched comparisons were used to identify factors related to the utilization of IONM and risk factors for neurological deficits after elective ACDF.

RESULTS

A total of 70,838 [15,092 monitored (21.3%) and 55,746 (78.7%) unmonitored] patients' data were extracted. The utilization of IONM since 2007 has increased in a linear manner from 0.9% of cases in 2007 to 36.7% by 2018. Overall, baseline characteristics of patients who were monitored during cases differed significantly from unmonitored patients in age, race/ethnicity, insurance type, presence of myelopathy or radiculopathy, and Charlson Comorbidity Index; however, only race/ethnicity was statistically significant when analyzed using propensity-score-matched. When comparing urban and rural medical centers, there is a significant lag in the adoption of the technology with no monitored cases in rural centers until 2012 with significant fluctuations in utilization compared with steadily increasing utilization among urban centers. From 2017 to 2018, reporting of neurological deficits after surgery resembled literature-established norms. Pooled analysis of these years revealed that the incidence of neurological complications occurred more frequently in monitored cases than in unmonitored (3.0% vs. 1.4%, P < 0.001).

CONCLUSIONS

The utility of IONM for elective ACDF remains uncertain; however, it continues to gain popularity for routine cases. For medical centers that lack similar resources to centers in more densely populated regions of NY state, reliable access to this technology is not a certainty. In our analysis of intraoperative neurological complications, it seems that IONM is not protective against neurological injury.

Efficacy of Intraoperative Neuromonitoring during the Treatment of Cervical Myelopathy

Objective The accuracy of intraoperative neuromonitoring (IONM) during surgery for cervical spondylotic myelopathy (CSM) to detect iatrogenic nervous system injuries while they are reversible remains unknown. We evaluated a cohort of patients who had IONM during surgery to assess accuracy.

Methods Patients who underwent surgical treatment of CSM that included IONM from January 2018 through August 2018 were retrospectively identified. A standardized protocol was used for operative management. Clinical changes and postoperative neurological deficits were evaluated.

Results Among 131 patients in whom IONM was used during their procedure, 42 patients (age 58.2 ± 16.3 years, 54.8% males) showed IONM changes and 89 patients had no change. The reasons for IONM changes varied, and some patients had changes detected via multiple modalities: electromyography (n = 25, 59.5%), somatosensory-evoked potentials (n = 14, 33.3%), motor evoked potentials (n = 13, 31.0%). Three patients, all having baseline deficits before surgery, had postoperative deficits. Among the 89 patients without an IONM change, 4 showed worsened postoperative deficits, which were also seen at last follow-up. The sensitivity of IONM for predicting postoperative neurological change was 42.86% and the specificity was 68.55%. However, most patients (124, 94.7%) in whom IONM was used showed no worsened neurological deficit.

Conclusions IONM shows potential in ensuring stable postoperative neurological outcomes in most patients; however, its clinical use and supportive guidelines remain controversial. In our series, prediction of neurological deficits was poor in contrast to some previous studies. Further refinement of clinical and electrophysiological variables is needed to uniformly predict postoperative neurological outcomes.

The Role of Intraoperative Neuromonitoring Modalities in Anterior Cervical Spine Surgery

Background: Intraoperative neuromonitoring (IONM) is frequently used during spine surgery to mitigate the risk of neurological injuries. Yet, its role in anterior cervical spine surgery remains controversial. Without consensus on which anterior cervical spine surgeries would benefit the most from IONM, there is a lack of standardized guidelines for its use in such procedures. Purpose: We sought to assess the alerts generated by each IONM modality for 4 commonly performed anterior cervical spinal surgeries: anterior cervical diskectomy and fusion (ACDF), anterior cervical corpectomy and fusion (ACCF), cervical disk replacement (CDR), or anterior diskectomy. In doing so, we sought to determine which IONM modalities (electromyography [EMG], motor evoked potentials [MEP], and somatosensory evoked potentials [SSEP]) are associated with alert status when accounting for procedure characteristics (number of levels, operative level). Methods: We conducted a retrospective review of IONM data collected by Accurate Neuromonitoring, LLC, a company that supports spine surgeries conducted by 400 surgeons in 8 states, in an internally managed database from December 2009 to September 2018. The database was queried for patients who underwent ACCF, ACDF, anterior CDR, or anterior diskectomy in which at least 1 IONM modality was used. The IONM modalities and incidence of alerts were collected for each procedure. The search identified 8854 patients (average age, 50.6 years) who underwent ACCF (n = 209), ACDF (n = 8006), CDR (n = 423), and anterior diskectomy (n = 216) with at least 1 IONM modality. Results: Electromyography was used in 81.3% (n = 7203) of cases, MEP in 64.8% (n = 5735) of cases, and SSEP in 99.9% (n = 8844) of cases. Alerts were seen in 9.3% (n = 671), 0.5% (n = 30), and 2.7% (n = 241) of cases using EMG, MEP and SSEP, respectively. In ACDF, a significant difference was seen in EMG alerts based on the number of spinal levels involved, with 1-level ACDF (6.9%, n = 202) having a lower rate of alerts than 2-level (10.0%, n = 272), 3-level (15.2%, n = 104), and 4-level (23.4%, n = 15). Likewise, 2-level ACDF had a lower rate of alerts than 3-level and 4-level ACDF. A significant difference by operative level was noted in EMG use for single-level ACDF, with C2-C3 having a lower rate of use than other levels. Conclusions: This retrospective review of anterior cervical spinal surgeries performed with at least 1 IONM modality found that SSEP had the highest rate of use across procedure types, whereas MEP had the highest rate of nonuse. Future studies should focus on determining the most useful IONM modalities by procedure type and further explore the benefit of multimodal IONM in spine surgery.

Assessment of neuromonitoring use and postoperative readmission rates in pediatric Chiari I malformation with syrinx

INTRODUCTION

While operative intervention for Chiari malformation type I (CMI) with syringomyelia is well established, there is limited data on outcomes of intraoperative neuromonitoring (IONM). This study sought to explore differences in procedural characteristics and their effects on postoperative readmission rates.

METHODS

The Nationwide Readmission Database was queried from 2010 to 2014 for patients ≤ 18 years of age with CMI and syringomyelia who underwent cranial decompression or spinal decompression. Demographics, hospital characteristics, and outcomes were analyzed.

RESULTS

Over the 5-year period, 2789 patients were identified that underwent operative treatment for CMI with syringomyelia. Mean age was 10 ± 4 years with 55% female. During their index hospitalization 14% of the patients had IONM. Patients receiving IONM had no significant difference in Charleston Comorbidity Index ≥ 1 (16% vs. 15% without, p = 0.774). IONM was more often used in those with private insurance (63% vs. 58% without, p = 0.0004) and less likely in those with Medicaid (29% vs. 37% without, p = 0.004). Patients receiving IONM were more likely to have a postoperative complication (23% vs 17%, p = 0.004) and were more likely to have hospital lengths of stay > 7 days (9% vs. 5% without, p = 0.005). Readmission rates for CMI were 9% within 30 days and 15% within the year. The majority (89%) of readmissions were unplanned. 25% of readmissions were for infection and 27% of readmissions underwent a CMI reoperation. The 30-day readmission rate was higher for those with IONM (12% vs. 8% without, p = 0.010). Median cost for hospitalization was significantly higher for patients with IONM ($26,663 ($16,933-34,397)) vs. those without ($14,577 ($11,538-18,392)), p < 0.001.

CONCLUSION

The use of intraoperative neuromonitoring for operative repair of CMI is associated with higher postoperative complications and readmissions. In addition, there are disparities in its use and increased cost to the healthcare system. Further studies are needed to elucidate the factors underlying this association.

Estimating Intraoperative Neurophysiological Monitoring Rates for Anterior Cervical Discectomy and Fusion: Are Diagnostic or Procedural Codes Accurate?

BACKGROUND

The utility of intraoperative neurophysiological monitoring (IONM) is well established for some spine surgeries (eg, intramedullary tumor resection, scoliosis deformity correction), but its benefit for most degenerative spine surgery, including anterior cervical discectomy and fusion (ACDF), remains debated. National datasets provide "big data" approaches to study the impact of IONM on spine surgery outcomes; however, if administrative coding in these datasets misrepresents actual IONM usage, conclusions will be unreliable. The objective of this study was to compare estimated rates (administrative coding) to actual rates (chart review) of IONM for ACDF at our institution and extrapolate findings to estimated rates from 2 national datasets.

METHODS

Patients were included from 3 administrative coding databases: the authors' single institution database, the Nationwide Inpatient Sample (NIS), and the National Surgical Quality Improvement Program (NSQIP). Estimated and actual institutional rates of IONM during ACDF were determined by administrative codes (International Classification of Diseases [ICD] or Current Procedural Terminology [CPT]) and chart review, respectively. National rates of IONM during ACDF were estimated using the NIS and NSQIP datasets.

RESULTS

Estimated institutional rates of IONM for ACDF were much higher with CPT than ICD coding (73.2% vs 16.5% in 2019). CPT coding for IONM better approximated actual IONM usage at our institution (74.6% in 2019). Estimated IONM utilization rates for ACDF in national datasets varied widely: 0.76% in CPT-based NSQIP and 18.4% in ICD-based NIS.

CONCLUSIONS

ICD coding underestimated IONM usage during ACDF at our institution, whereas CPT coding was more accurate. Unfortunately, the CPT-based NSQIP is nearly devoid of IONM codes, as it has not been a collection focus of that surgical registry. ICD-based datasets, such as the NIS, likely fail to accurately capture IONM usage. Multicenter and/or national datasets with accurate IONM utilization data are needed to inform surgeons, insurers, and guideline authors on whether IONM has benefit for various spine surgery types.

LEVEL OF EVIDENCE: 4

CLINICAL RELEVANCE

Currently available national databases based on administrative codes do not accurately reflect IONM usage.

Natural language processing for automated surveillance of intraoperative neuromonitoring in spine surgery

We sought to develop natural language processing (NLP) methods for automated detection and characterization of neuromonitoring documentation from free-text operative reports in patients undergoing spine surgery. We included 13,718 patients who received spine surgery at two tertiary academic medical centers between December 2000 - December 2020. We first validated a rule-based NLP method for identifying operative reports containing neuromonitoring documentation, comparing performance to standard administrative codes. We then trained a deep learning model in a subset of 993 patients to characterize neuromonitoring documentation and identify events indicating change in status or difficulty establishing baseline signals. Performance of the deep learning model was compared to gold-standard manual chart review. In our patient population, 3,606 (26.3%) patients had neuromonitoring documentation identified using NLP. Our NLP method identified notes containing neuromonitoring documentation with an F1-score of 1.0, surpassing performance of standard administrative codes which had an F1-score of 0.64. In the subset of 993 patients used for training, validation, and testing a deep learning model, the prevalence of change in status was 6.5% and difficulty establishing neuromonitoring baseline signals was 6.6%. The deep learning model had an F1-score = 0.80 and AUC-ROC = 1.0 for identifying change in status, and an F1-score = 0.80 and AUC-ROC = 0.97 for identifying difficulty establishing baseline signals. Compared to gold standard manual chart review, our methodology has greater efficiency for identifying infrequent yet important types of neuromonitoring documentation. This method may facilitate large-scale quality improvement initiatives that require timely analysis of a large volume of EHRs.

Automated Nerve Monitoring in Shoulder Arthroplasty: A Prospective Randomized Controlled Study

BACKGROUND

Evoked potential monitoring is believed to prevent neurologic injury in various surgical settings; however, its clinical effect has not been scrutinized. It was hypothesized that an automated nerve monitor can minimize intraoperative nerve injury and thereby improve clinical outcomes in patients undergoing shoulder arthroplasty.

METHODS

A prospective, blinded, parallel group, superiority design, single-center, randomized controlled study was conducted. Study participants were equally randomized into either the automated nerve-monitored or the blinded monitored groups. The primary outcome was intraoperative nerve injury burden as assessed by the cumulative duration of nerve alerts. Secondary outcomes were neurologic deficits and functional scores of the operative arm, and the quality of life index (Euro Quality of life-5 domain-5 level score) at postoperative weeks 2, 6, and 12.

RESULTS

From September 2018 to July 2019, 213 patients were screened, of whom 200 were randomized. There was no statistically significant difference in the duration of nerve alerts between the automated nerve-monitored and control groups (median [25th, 75th interquartile range]: 1 [0, 18] and 5 [0, 26.5]; Hodges-Lehman difference [95% CI]: 0 [0 to 1] min; P = 0.526). There were no statistically significant differences in secondary outcomes between groups. However, in the ancillary analysis, there were reductions in neurologic deficits and improvements in quality of life index occurring in both groups over the course of the study period.

CONCLUSIONS

Protection from nerve injury is a shared responsibility between surgeons and anesthesiologists. Although a progressive improvement of clinical outcomes were observed over the course of the study in both groups as a consequence of the real-time feedback provided by the automated nerve monitor, this trial did not demonstrate that automated nerve monitoring by itself changes important clinical outcomes compared with no monitoring.

EDITOR’S PERSPECTIVE

The utility of intraoperative neuromonitoring on simple posterior lumbar fusions-analysis of the National Inpatient Sample

BACKGROUND

Several studies have demonstrated the utility of intraoperative neuromonitoring (IOM) including somatosensory evoked potentials (SSEPs), motor-evoked potentials (MEPs), and electromyography (EMG), in decreasing the risk of neurologic injury in spinal deformity procedures. However, there is limited evidence supporting the routine use of IOM in elective posterolateral lumbar fusion (PLF).

METHODS

The National Inpatient Sample (NIS) was analyzed for the years 2012-2015 to identify patients undergoing elective PLF with (n=22,404) or without (n=111,168) IOM use. Statistical analyses were conducted to assess the impact of IOM on length of stay, total charges, and development of neurologic complications. These analyses controlled for age, gender, race, income percentile, primary expected payer, number of reported comorbidities, hospital teaching status, and hospital size.

RESULTS

The overall use of IOM in elective PLFs was found to have increased from 14.6% in the year 2012 to 19.3% in 2015. The total charge in hospitalization cost for all patients who received IOM increased from $129,384.72 in 2012 to $146,427.79 in 2015. Overall, the total charge of hospitalization was 11% greater in the IOM group when compared to those patients that did not have IOM (P<0.001). IOM did not have a statistically significant impact on the likelihood of developing a neurological complication.

CONCLUSIONS

While there may conceivably be benefits to the use of this technology in complex revision fusions or pathologies, we found no meaningful benefit of its application to single-level index PLF for degenerative spine disease.

Achieving Value in Spine Surgery: 10 Major Cost Contributors

STUDY DESIGN

Narrative Review.

OBJECTIVES

The increasing cost of healthcare overall and for spine surgery, coupled with the growing burden of spine-related disease and rising demand have necessitated a shift in practice standards with a new emphasis on value-based care. Despite multiple attempts to reconcile the discrepancy between national recommendations for appropriate use and the patterns of use employed in clinical practice, resources continue to be overused-often in the absence of any demonstrable clinical benefit. The following discussion illustrates 10 areas for further research and quality improvement.

METHODS

We present a narrative review of the literature regarding 10 features in spine surgery which are characterized by substantial disproportionate costs and minimal-if any-clear benefit. Discussion items were generated from a service-wide poll; topics mentioned with great frequency or emphasis were considered. Items are not listed in hierarchical order, nor is the list comprehensive.

RESULTS

We describe the cost and clinical data for the following 10 items: Over-referral, Over-imaging & Overdiagnosis; Advanced Imaging for Low Back Pain; Advanced imaging for C-Spine Clearance; Advanced Imaging for Other Spinal Trauma; Neuromonitoring for Cervical Spine; Neuromonitoring for Lumbar Spine/Single-Level Surgery; Bracing & Spinal Orthotics; Biologics; Robotic Assistance; Unnecessary perioperative testing.

CONCLUSIONS

In the pursuit of value in spine surgery we must define what quality is, and what costs we are willing to pay for each theoretical unit of quality. We illustrate 10 areas for future research and quality improvement initiatives, which are at present overpriced and underbeneficial.

Filum terminale lipomas-the role of intraoperative neuromonitoring

BACKGROUND

Filum terminale lipomas (FTL) represent a sub-type of spinal lipomas, where there is fatty infiltration of the filum. It becomes a surgical entity when it manifests as clinical or radiological tethered cord syndrome. Intraoperative neuromonitoring (IONM) has been suggested as a valuable tool in children for tethered cord surgeries. FTL is distinct and cannot be compared with complex tethered cord syndrome (TCS). Untethering an FTL is a relatively straightforward microsurgical exercise, usually based on anatomical findings. Neurological morbidity in FTL untethering is extremely low. The necessity of IONM in FTL has not been evaluated. The objective of this study was to identify the role of IONM in untethering an FTL METHODS: Available electronic data and case files were interrogated to identify children (0-18 years) who underwent an untethering of FTL between 2008 and 2019. We had a shift in our policy and tried to use IONM as often as possible in all tethered cord surgery from 2014. All children were categorised under 'IONM implemented' or 'no IONM' group. Outcomes analysed were as follows: (1) Clinical status on short-term and long-term follow-up, (2) alteration of surgical course by IONM and (3) complications specifically associated with IONM RESULTS: Among 80 children included in this study, IONM was implemented in 37 children and 43 children underwent untethering without IONM. 32.5% of children were 'syndromic'. Seventy-five percent of children were under age 3 years during surgery. Both groups (No IONM vs. IONM implemented) were well matched in most variables. Majority of 'no IONM' surgeries were performed prior to 2014. There was no neurological morbidity in the entire cohort. Mean duration of follow-up was 49.10 (± 33.67) months. Short-term and long-term clinical status remained stable in both cohorts. In 16 children, the filum was stimulated. Based on our protocol, majority had a negative response. One child showed a positive response, contradicted by thorough microscopic inspection. Despite a positive response, the filum was untethered. IONM was not associated with any complication in this study.

CONCLUSION

FTL untethering is an inherently low-risk microsurgery in experienced hands with rarely reported neurological morbidity. IONM may not be required for all FTL and may be used more judiciously.

Feasibility of Using Intraoperative Neuromonitoring in the Prophylaxis of Dysesthesia in Transforaminal Endoscopic Discectomies of the Lumbar Spine

(1) Background: Postoperative nerve root injury with dysesthesia is the most frequent sequela following lumbar endoscopic transforaminal discectomy. At times, it may be accompanied by transient and rarely by permanent motor weakness. The authors hypothesized that direct compression of the exiting nerve root and its dorsal root ganglion (DRG) by manipulating the working cannula or endoscopic instruments may play a role. (2) Objective: To assess whether intraoperative neurophysiological monitoring can help prevent nerve root injury by identifying neurophysiological events during the initial placement of the endoscopic working cannula and the directly visualized video endoscopic procedure. (3) Methods: The authors performed a retrospective chart review of 65 (35 female and 30 male) patients who underwent transforaminal endoscopic decompression for failed non-operative treatment of lumbar disc herniation from 2012 to 2020. The patients’ age ranged from 22 to 86 years, with an average of 51.75 years. Patients in the experimental group (32 patients) had intraoperative neurophysiological monitoring recordings using sensory evoked (SSEP), and transcranial motor evoked potentials (TCEP), those in the control group (32 patients) did not. The SSEP and TCMEP data were analyzed and correlated to the postoperative course, including dysesthesia and clinical outcomes using modified Macnab criteria, Oswestry disability index (ODI), visual analog scale (VAS) for leg and back pain. (4) Results: The surgical levels were L4/L5 in 44.6%, L5/S1 in 23.1%, and L3/L4 in 9.2%. Of the 65 patients, 56.9% (37/65) had surgery on the left, 36.9% (24/65) on the right, and the remaining 6.2% (4/65) underwent bilateral decompression. Postoperative dysesthesia occurred in 2 patients in the experimental and six patients in the control group. In the experimental neuromonitoring group, there was electrodiagnostic evidence of compression of the exiting nerve root’s DRG in 24 (72.7%) of the 32 patients after initial transforaminal placement of the working cannula. A 5% or more decrease and a 50% or more decrease in amplitude of SSEPs and TCEPs recordings of the exiting nerve root were resolved by repositioning the working cannula or by pausing the root manipulation until recovery to baseline, which typically occurred within an average of 1.15 min. In 15 of the 24 patients with such latency and amplitude changes, a foraminoplasty was performed before advancing the endoscopic working cannula via the transforaminal approach into the neuroforamen to avoid an impeding nerve root injury and postoperative dysesthesia. (5) Conclusion: Neuromonitoring enabled the intraoperative diagnosis of DRG compression during the initial transforaminal placement of the endoscopic working cannula. Future studies with more statistical power will have to investigate whether employing neuromonitoring to avoid intraoperative compression of the exiting nerve root is predictive of lower postoperative dysesthesia rates in patients undergoing videoendoscopic transforaminal discectomy.

Barriers of neurophysiology monitoring in spine surgery: Latin America experience

Background:

Intraoperative neurophysiological monitoring (IOM) has become valuable in spine surgery. Unfortunately, it is not always available in many spine centers, especially in developing countries. Our aim was to evaluate the accessibility and barriers to IOM in spine surgery in Latin America.

Methods:

We designed a questionnaire to evaluate the characteristics of surgeons and their opinions on the usefulness of IOM for different spine operations. The survey was sent to 9616 members and registered users of AO Spine Latin America (AOSLA) from August 1, 2019, to August 21, 2019. Major variables studied included nationality, years of experience, specialty (orthopedics or neurosurgery), level of complexity of the hospital, number of spine surgeries performed per year by the spine surgeon, the types of spinal pathologies commonly managed, and how important IOM was to the individual surgeon. General questions to evaluate use included accessibility, limitations of IOM usage, management of IOM changes, and the legal value of IOM. The results were analyzed and compared between neurosurgeon and orthopedics, level of surgeon experience, and country of origin.

Results:

Questionnaires were answered by 200 members of AOSLA from 16 different countries. The most common responses were obtained from orthopedic surgeons (62%), those with more than 10 years of practice (54%); majority of surgeons performed more than 50 spine surgeries per year (69%) and treated mainly spine degenerative diseases (76%). Most surgeons think that IOM has a real importance during surgeries (92%) and not just a legal value. Although surgeons mostly considered IOM essential to scoliosis surgery in adolescents (70%), thoracolumbar kyphosis correction (68%), and intramedullary tumors (68%), access to IOM was limited to 57% for economic reasons. Of interest, in 64% of cases, where IOM was available and significant change occurred, the actual operative procedures were significantly altered.

Conclusion:

Despite the fact that 68% of spine surgeons believe IOM to be indispensable for complex spine surgery, cost remains the main barrier to its use/availability in Latin America.

Indication and technical implementation of the intraoperative neurophysiological monitoring during spine surgeries-a transnational survey in the German-speaking countries

BACKGROUND

Intraoperative neurophysiological monitoring is widely used in spine surgery (sIONM). But guidelines are lacking and its use is mainly driven by individual surgeons' preferences and medicolegal advisements. To gain an overview over the current status of sIONM implementation, we conducted a transnational survey in the German-speaking countries.

METHODS

We developed a Web interface-based survey assessing prevalence, indication, technical implementation, and general satisfaction regarding sIONM in German, Austrian, and Swiss spine centers. The electronic survey was performed between November 2017 and April 2018, including both neurosurgical and orthopedic spine centers.

RESULTS

A total of 463 German, 60 Austrian, and 52 Swiss spine centers were contacted with participation rates of 64.1% (Germany), 68.3% (Austria), and 55.8% (Switzerland). Some 75.9% participating neurosurgical spine centers and only 14.7% of the orthopedic spine centers applied sIONM. Motor- and somatosensory-evoked potentials (93.7% and 94.3%, respectively) were the most widely available modalities, followed by direct wave (D wave; 66.5%). Whereas sIONM utilization was low in spine surgeries for degenerative, traumatic, and extradural tumor diseases, it was high for scoliosis and intradural tumor surgeries. Overall, the general satisfaction within the institutional setting regarding technical skills, staff, performance, and reliability of sIONM was rated as "high" by more than three-quarters of the centers. However, shortage of skilled staff was claimed to be a negative factor by 41.1% of the centers and reimbursement was considered to be insufficient by 83.5%.

CONCLUSIONS

sIONM availability was high in neurosurgical but low in orthopedic spine centers. Main modalities were motor/somatosensory-evoked potentials and main indications were scoliosis and intradural spinal tumor surgeries. A more frequent sIONM use, however, was mainly limited by the shortage of skilled staff and restricted reimbursement.