History of the development of intraoperative spinal cord monitoring

Quadripolar Stimulation as an Adjunct to Neuromonitoring in Scoliosis Surgery: A Case Report

CASE

A healthy 13-year-old adolescent girl with a normal spine magnetic resonance imaging underwent posterior spinal fusion for adolescent idiopathic scoliosis (AIS). Before surgery, she had abnormal baseline motor-evoked potentials (MEPs). After technical issues were ruled out, quadripolar stimulation yielded normal baseline MEPs and somatosensory evoked potentials. The surgery was completed without complication, and the patient awoke from surgery without signs of neurological deficits.

CONCLUSION

Quadripolar stimulation with the use of an additional paired anode and cathode is a useful adjunct and should be used in troubleshooting abnormal baseline neuromonitoring in patients with AIS with normal spine imaging undergoing posterior spinal fusion.

Next-Generation Neuromonitoring in Minimally Invasive Spine Surgery: Indications, Techniques, and Clinical Outcomes

Neuromonitoring in minimally invasive spine surgery (MISS) provides real-time feedback to surgeons and enhances surgical precision for improved patient safety. Since the 1970s, established techniques like somatosensory evoked potentials, motor evoked potentials, and electromyography have been integrated into spine surgeries, significantly reducing the risk of neurological complications. These neuromonitoring modalities have been crucial, particularly in complex procedures with limited direct visualization. Refinements in these techniques have led to greater confidence in nerve root safety, contributing to the success of MISS. Despite some debate regarding the routine use of neuromonitoring in noncomplex surgeries, its importance in complex cases is well-documented. Studies have demonstrated high sensitivity and specificity rates for these techniques, with multimodal approaches offering the best outcomes. Advancements in mechanomyography and its potential integration into neuromonitoring protocols highlight the continuous improvement in this field. This review explores the historical development, current techniques, clinical outcomes, and future directions of neuromonitoring in MISS. It emphasizes the critical role of these technologies in enhancing surgical outcomes and patient care. As MISS continues to evolve, adopting next-generation neuromonitoring systems, including artificial intelligence and machine learning, will play a pivotal role in advancing the efficacy and safety of spine surgeries.

Characteristics and Usefulness of Neurophysiological Monitoring in Corrective Procedures for Abnormally Curved Spine in Young Patients

PURPOSE

To identify and characterize events of deterioration in intraoperative neuromonitoring data during correction procedures for thoracic and lumbar abnormal spinal curvature in young patients.

METHODS

Records of 1,127 cases were retrospectively reviewed to identify events with deterioration of the neuromonitoring data. General etiological and demographic variables were summarized, and neuromonitoring events were studied and characterized.

RESULTS

Adolescent idiopathic cases were associated with female dominance and older age. Nonadolescent idiopathic cases were associated with a higher rate of neuromonitoring events. The neuromonitoring events evolved during the different procedural stages, were primarily reflected in the motor-evoked potential data and affected a range of neural structures to varying degrees. Most of the events were resolved, partially or completely, following a corresponding intervention by the surgical team, before the end of the procedure. Significant immediate weakness of the lower extremities was demonstrated in patients with unresolved neuromonitoring events, most of them were nonadolescent idiopathic patients.

CONCLUSIONS

Neurophysiological monitoring enables the intraoperative assessment of the integrity of neural pathways and allows the detection of surgery-related impending neural injuries. Neuromonitoring contributes to intraoperative decision making, either when data are uneventful and allow confident continuation or when data deteriorate and lead to corresponding intervention. Further awareness should be paid to the vulnerable characteristics of the patient, surgery course, and neuromonitoring data. Proper interpretation of the neuromonitoring data, together with corresponding intervention by the surgeon when necessary, has the potential to reduce postoperative neurological insults and improve clinical outcomes.

Intraoperative neuromonitoring is not a useful adjunct for Chiari malformation decompressive surgery: a cost-benefit and legal analysis

OBJECTIVES

Posterior fossa decompression is currently an operative treatment of choice for Chiari Malformation I (CM1). However, there is controversy surrounding the possible benefits of employing intraoperative neuromonitoring (INM) for this type of procedure. In addition to presenting our single-center experience on the use of INM, we analyze the cost associated with INM in Chiari Malformation (CM) decompression surgery using the Healthcare Cost and Utilization Project (HCUP) database and discuss the legal implications of somatosensory evoked potentials (SSEP) monitoring during decompression for CM1.

METHODS

We conducted a retrospective review of all patients undergoing CM1 decompression with SSEP neuromonitoring from 2011 to 2018. We collected patient characteristics, hospital charges, and surgical cost data from the HCUP database for patients undergoing CM decompression. Finally, we performed a review within the Thompson Reuters Westlaw Edge database for reported litigation involving INM for CM decompression.

RESULTS

None of the 110 patients submitted to surgery for CM1 at our institution had any significant SSEP changes intraoperatively or developed post-operative neurological deterioration. There were higher mean total hospital charges and surgical costs associated with INM ($31,272) for patients who received INM compared to patients who did not receive INM ($24,112). A careful review of the Westlaw database with multiple-word search strategies revealed no reported medical malpractice claims regarding the absence of SSEP neuromonitoring in a CM decompression procedure.

CONCLUSION

Using data collected at our institution and the HCUP national database, we showed that intraoperative neuromonitoring did not affect surgical planning and decision-making or post operative care, while adding unnecessary costs to CM decompression procedures. The absence of reported malpractice claims targeting the lack of neuromonitoring in CM cases suggests that SSEP neuromonitoring during CM may be unnecessary. We propose that neuromonitoring should not be used for routine CM decompression.

Utilization of Neuromonitoring in Surgical Cervical Spondylosis Patients With the Presence or Absence of Myelopathy. Is it Standard?

STUDY DESIGN

Cross-sectional, observational study.

OBJECTIVE

Investigate the frequency of intraoperative neuromonitoring (IONM) utilization among Medicare patients diagnosed with cervical spondylosis (CS), both with and without myelopathy.

BACKGROUND

IONM is widely used as a tool in spine surgery. However, the overall prevalence of neuromonitoring utilization among CS undergoing surgical intervention is not well characterized.

METHODS

This study observed neuromonitoring usage in CS patients who had cervical spinal procedures from 2012 to 2020, using a 5% random sample of Medicare data. Logistic regression compared patient characteristics between those who received neuromonitoring and those who did not. The model included age, sex, region, Elixhauser Comorbidity Index score, year of surgery, elective status, and procedure type. Odds ratios with a 95% CI were generated for each covariate.

RESULTS

Of the 6224 patients who underwent cervical procedures for CS, 4053 were included in the study, with 2845 having myelopathy and 1208 without. Myelopathy patients had a higher number of hospitalizations (2884) compared with non-myelopathy patients (1229). Among myelopathy patients, the prevalence of neuromonitoring increased from 49.2% in 2012 to 56.5% in 2020. The range of utilization for each type of monitoring was: 96.4%-100% for somatosensory evoked potential, 73.2%-86.1% for electromyography, 70.0%-86.1% for motor evoked potential, and 17.6%-33.6% for other modalities. For non-myelopathy patients, neuromonitoring prevalence increased from 33.1% in 2012 to 43.3% in 2020. The range of utilization for each type of monitoring was: 93.0%-100% for somatosensory evoked potential, 68.9%-89.7% for electromyography, 55.8%-77.4% for motor evoked potential, and 17.8%-36.4% for other modalities.

CONCLUSIONS

This study investigates the utilization of IONM during cervical spinal surgeries in Medicare patients with cervical spondylotic myelopathy or CS between 2012 and 2020. Although IONM is employed in cervical spine procedures, its adoption and standardization appear to vary across the country and different health care settings.

Intraoperative somatosensory evoked potential (SEP) monitoring: an updated position statement by the American Society of Neurophysiological Monitoring

Somatosensory evoked potentials (SEPs) are used to assess the functional status of somatosensory pathways during surgical procedures and can help protect patients' neurological integrity intraoperatively. This is a position statement on intraoperative SEP monitoring from the American Society of Neurophysiological Monitoring (ASNM) and updates prior ASNM position statements on SEPs from the years 2005 and 2010. This position statement is endorsed by ASNM and serves as an educational service to the neurophysiological community on the recommended use of SEPs as a neurophysiological monitoring tool. It presents the rationale for SEP utilization and its clinical applications. It also covers the relevant anatomy, technical methodology for setup and signal acquisition, signal interpretation, anesthesia and physiological considerations, and documentation and credentialing requirements to optimize SEP monitoring to aid in protecting the nervous system during surgery.

There's No "I" in "Team": Recommendations for Effective Teamwork and Communication in IONM

Effective teamwork is essential in almost every job, and can even mean life, death, or disability in some jobs. Intraoperative neurophysiological monitoring (IONM) is a career in which effective teamwork and accurate communication are of utmost importance, yet it comes with a unique set of challenges in which to achieve those goals. Operating rooms can be very stressful environments, even if a surgical neurophysiologist (SNP) works in the same hospital every day. Often an SNP is required to travel from hospital to hospital and work with different teams each day. In addition, communication with the IONM oversight professional (IONM-P) can be challenging by nature of the telemedicine model which is becoming the most commonly applied IONM model in the United States. It is unfortunate that such critical skills are assumed and are rarely formally trained. In this article, we present evidence-based recommendations for establishing effective team function. We also provide several tools designed to help create effective and efficient teams. Teams cannot function at their best without outstanding communication, so improving teamwork also means improving communication. This article also provides several techniques for excellent communication, regardless of the situation or context.

Cost-Effectiveness of Intraoperative Electromyography to Determine Adequate Screw Position

STUDY DESIGN

Prospective observational cohort.

OBJECTIVES

To examine the cost-effectiveness of IntraOperative ElectroMyeloGraphy (IO-EMG) by evaluating how often an abnormal IO-EMG signal changed the surgeon's surgical plan, or replaced a pedicle screw either intra-operatively or as a second unplanned surgery.

METHODS

Patients undergoing instrumented posterolateral lumbar fusion were monitored with intraoperative triggered EMG's. Pedicle screws were placed freehand from L1 to S1 by attending physicians and fellows. Concern for pedicle breach was a screw stimulation<10 mA.

RESULTS

There were 145 cases with a total of 725 pedicle screws placed. Mean age was 57.8 ± 14.2 yrs, OR time was 238 ± 95 minutes, EBL was 426.8 ± 354.3cc. Mean number of surgical levels fused was 2.7 ± 1.1. 686 (95%) screws stimulated at >10 mA and 39 (5%) screws stimulated at <10 mA. All 39 screws were removed and pedicles re-examined. Intraoperative screw repositioning was necessary in 8 of 145 cases (6%). No patient required a return to the OR for screw repositioning. As a worst case cost analysis, assuming the 8 patients requiring intraoperative screw positioning would have returned to the OR at a cost of $11,798 per readmission, the per patient cost is $651 which is less than the ION per patient cost of $750.

CONCLUSIONS

Only 1% of the 725 lumbar pedicle screws placed in 8 of 145 cases required repositioning. Due to the infrequency of pedicle wall breaches and the cost of ION, the utility of this modality in straightforward lumbar fusions should be critically evaluated.

The adjunct use of descending neurogenic-evoked potentials when transcranial motor-evoked potentials degrade into warning criteria in pediatric spinal deformity surgery: minimizing false-positive events

PURPOSE

This studies objective was to evaluate the utility of descending neurogenic-evoked potentials (DNEPs) in the setting of transcranial motor-evoked potentials (TCeMEPs) degradation into warning criteria during pediatric spinal deformity surgery.

METHODS

An institutional spinal cord monitoring database was queried to identify all primary and revision pediatric spinal deformity cases, < / = 21 years of age performed from 1/2006 to 12/2021, in which TCeMEPs were the primary motor tract assessment modality which degraded into warning criteria, with subsequent initiation of adjunct DNEPs.

RESULTS

Fourteen surgical cases (0.42%; 3351 total cases) in fourteen patients met inclusion criteria. Mean age was 13.2 years (7.5-21.3).

DIAGNOSES

syndromic (n = 7), kyphosis (n = 3), congenital (n = 2), and idiopathic (n = 2). Three-column osteotomies (3CO)were done in eight patients. TCeMEPs degraded into warning criteria during screw placement (n = 7), 3CO performance/closure (n = 4), or deformity correction (n = 3). DNEPs were present in all cases of warning-criteria TCeMEPs and one case had degradation of DNEPs. Intraoperative Stagnara wake-up tests were performed in only 2/14 cases, with one transient new neurologic deficit (NND). In this specific scenario, DNEPs sensitivity was 50%, specificity 100%, positive predictive value 100%, and negative predictive value 92% to detect aNND.

CONCLUSION

DNEPs were useful in assessing spinal cord function in the setting of TCeMEP data degradation in complex pediatric deformity surgeries. DNEPs demonstrated a higher specificity and positive predictive value in this clinical setting than TCeMEPs when assessing long-term neurologic function after surgery. Based on this small cohort, DNEPs appear to be a useful adjunct modality to TCeMEPs, in this challenging clinical scenario.

Multimodal Intraoperative Neurophysiological Monitoring in Cranial and Spinal Tumour Surgeries: A Descriptive Observational Study

Intraoperative neurophysiological monitoring (IONM) involves monitoring the functional integrity of critical brain regions and pathways as well as identifying and preserving functionally viable neural tissues (mapping) during surgery using electrophysiological techniques. Multimodality combines various neurophysiological techniques to optimise diagnostic effectiveness and to improve the outcomes of the surgeries. The present study is a case series with comprehensive and illustrative descriptions of the neurophysiological changes in five neuromonitored cases of cranial and spinal cord tumour surgeries conducted with a multimodal approach. The cases were monitored with somatosensory evoked potentials (SSEP), transcranial motor evoked potentials (TcMEP), and both free run and triggered electromyography (fEMG and tEMG). No false negative outcomes were identified in the cases studied as there was an association of absence of change in SSEP and TcMEP both, with no neurological deficit postoperatively. Two cases were identified as having true positive neuromonitoring alerts. No false positive alerts were found in any case. Multimodal monitoring using SSEP, TcMEP, and EMG (fEMG and tEMG) in cranial and spinal tumour surgeries can improve performance with fewer false-negative and false-positive results. Neuromonitoring approaches used in combination can provide reliable information regarding postoperative neurological outcomes.

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.

A long-term survival rat model of spinal cord ischemia injury: Thoracic aortic occlusion combined with aortic bypass circulation

OBJECTIVE

This study aims to investigate the methods for rat spinal cord ischemia injury models with a high long-term survival rate.

METHODS

The rats were divided into three groups: the treatment group, the control group, and the sham operation group. The treatment group had a blocked thoracic aorta (landing zone 3 by Ishimaru - T11) + aortic bypass circulation for 20 min. In the control group, the thoracic aorta at the landing zone 3 was blocked for 20 min. In the sham operation group, only thoracotomy without thoracic aortic occlusion was performed. The mean arterial blood pressure (MABP) of the thoracic aorta and caudal artery before and after thoracic aortic occlusion was monitored intraoperatively. Spinal cord function was monitored by a transcranial motor evoked potential (Tc-MEP) during the operation. Spinal cord function was evaluated by the BBB scale (Basso, Beattie, & Bresnahan locomotor rating scale) scores at multiple postoperative time points. The spinal cord sections of the rats were observed for 7 days after surgery, and the survival curves were analyzed for 28 days after surgery.

RESULTS

After aortic occlusion, the MABP of thoracic aorta decreased to 6% of that before occlusion, and the MABP of caudal artery decreased to 63% of that before occlusion in the treatment group. In the control group, the MABP of both thoracic aorta and caudal artery decreased to 19% of that before occlusion. The Tc-MEP waveform of the treatment group disappeared after 6 min, and that of the control group disappeared after 8 min until the end of surgery. There was no change in the Tc-MEP waveform in the sham operation group. The BBB score of the treatment group decreased more obviously than the control group, and there was a significant difference. There was no decrease in the sham group. Spinal cord sections showed a large number of degeneration and necrosis of neurons, infiltration of inflammatory cells, and proliferation of surrounding glial cells in the treatment group. In the control group, multiple neurons were necrotic. The histology of the sham operation group was normal. The 28-day survival rate of the treatment group was 73.3%, which was higher than the control group (40.0%), and there was a significant difference (p < 0.05).

CONCLUSION

Thoracic aortic occlusion combined with aortic bypass is an effective modeling method for rats with accurate modeling effects and high long-term survival rates.

Comprehensive Perioperative Approach to Complex Spine Deformity Management

OBJECTIVE

Study perioperative strategies for optimizing neuroprotection in complex spine deformity correction surgery.

METHODS

We report the case of a patient with severe lumbar dextroscoliosis, thoracolumbar junction hyperkyphosis with a 40-degree Cobb angle levoconvex scoliosis who underwent spinal deformity correction with loss of neuromonitoring during surgery. We performed a literature review on perioperative management of complex spine deformity.

RESULTS

A 50-year-old man presented with lumbar pain and right L4 radiculopathy. Surgical intervention for deformity correction and decompression was indicated with T4-L4 posterior instrumentation L2/L3 and L3/L4 transforaminal lumbar interbody fusion. Surgery was aborted due to the loss of neuromonitoring. Postsurgery, the patient had left sensory deficit and the neurocritical care team clinically suspected and deduced the anatomic location of the spinal cord compression. Magnetic resonance imaging confirmed a T10-T11 hyperintensity suggestive of cord ischemia due to osteophyte compressing the spinal cord. The patient underwent a second corrective surgery with no intraoperative events and has no long-term neurological sequela.

CONCLUSIONS

This case illustrates that a comprehensive perioperative approach and individualized risk factor assessment is useful in complex spine deformity surgery. Further research is needed to determine how this individualized comprehensive approach can lead to intraoperative and postoperative countermeasures that improved spine surgery outcomes.

LEVEL OF EVIDENCE

Level V.

Year in Review: Synopsis of Selected Articles in Neuroanesthesia and Neurocritical Care from 2021

This review is a synopsis of selected articles from neuroscience, neuroanesthesia, and neurocritical care from 2021 (January–December 2021). The journals reviewed include anesthesia journals, critical care medicine journals, neurology, and neurosurgical journals as well as high-impact medical journals such as the Lancet, Journal of American Medical Association, New England Journal of Medicine, and Stroke. This summary of important articles will serve to update the knowledge of anesthesiologists and other perioperative physicians who provide care to neurosurgical and neurocritical care patients. In addition, some of the important narrative reviews that are of interest to neuroanesthesiologists are also listed.

Intraoperative Neuromonitoring Auxiliary Significance of DNEP for MEP-positive Event During Severe Spinal Deformity Surgery

STUDY DESIGN

This was a retrospective analysis.

OBJECTIVE

The objective of this study was to assess the intraoperative neuromonitoring auxiliary significance of descending neurogenic-evoked potential (DNEP) for motor-evoked potential (MEP) during severe spinal deformity surgery when MEP-positive event occurs.

SUMMARY OF BACKGROUND DATA

MEP detection is the most widely applied neurological monitoring technique in spinal deformity surgery. MEP is quite vulnerable to anesthesia, blood pressure, and other intraoperative factors, leading to a high false-positive rate of MEP (3.2%-45.0%), which has greatly interfered with the surgical process. At present, the widely used "presence-or-absence" alarm criteria of MEP is not enough to solve the problem of false positive of MEP.

METHODS

A total of 205 cases undergoing severe spinal deformity correction were retrospectively studied. Overall, 74 MEP-positive cases were classified as 2 subgroups: DNEP (+) and DNEP (-) groups. The MEP recovery, wake-up test, and Frankle grade were used to assess the neurological functions. The perioperative and long-term neurological outcomes were assessed.

RESULTS

There were significant differences in preoperative scoliosis angle and kyphosis angle between DNEP (-) and DNEP (+) groups. Patients in DNEP (-) group showed more MEP improvement (81.5%), compared with the DNEP (+) group (53.2%). The Wake-up test showed 59.3% motor function deficit cases in DNEP (-) group, which was lower than the 87.2% in DNEP (+) group. More patients in DNEP (-) group had normal nerve function (Frankel level E) than those in DNEP (+) group immediately after surgery, as well as at follow-up.

CONCLUSIONS

MEP-positive cases with intraoperative DNEP (-) showed superior prognosis after severe spinal deformity surgery. Intraoperative DNEP could be regarded as an important quantitative tool to assist MEP to monitor neurological injury and can serve as a temporary substitution monitoring technique after MEP is lost.

Degenerative cervical myelopathy: Neuroradiological, neurophysiological and clinical correlations in 27 consecutive cases

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New insight into prognostic factors for recovery of clinical function following posterior decompression for degenerative cervical myelopathy.

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An increase of IOM amplitude of at least 50% coupled with preoperative T2-only and diffuse T2 signal changes on MRI is a positive prognostic factors for clinical improvement 6 months after surgery.

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Clinical improvement at 6 months follow-up can be expected in patients with T1 hypo intensity if a diffuse border of the lesion on T2 images is present.

The muscle evoked potential after epidural electrical stimulation of the spinal cord as a monitor for the corticospinal tract: studies by collision technique and double train stimulation

To study if spinal motor evoked potentials (SpMEPs), muscle responses after electrical stimulation of the spinal cord, can monitor the corticospinal tract. Study 1 comprised 10 consecutive cervical or thoracic myelopathic patients. We recorded three types of muscle responses intraoperatively: (1) transcranial motor evoked potentials (TcMEPs), (2) SpMEPs and (3) SpMEPs + TcMEPs from the abductor hallucis (AH) using train stimulation. Study 2 dealt with 5 patients, who underwent paired train stimulation to the spinal cord with intertrain interval of 50-60 ms for recording AH SpMEPs. We will also describe two illustrative cases to demonstrate the clinical value of AH SpMEPs for monitoring the motor pathway. In Study 1, SpMEPs and SpMEPs + TcMEPs recorded from AH measured nearly the same, suggesting the collision of the cranially evoked volleys with the antidromic signals induced by spinal cord stimulation via the corticospinal tracts. In Study 2, the first and second train stimuli elicited almost identical SpMEPs, indicating a quick return of transmission after 50-60 ms considered characteristic of the corticospinal tract rather than the dorsal column, which would have recovered much more slowly. Of the two patients presented, one had no post-operative neurological deteriorations as anticipated by stable SpMEPs, despite otherwise insufficient IONM, and the other developed post-operative motor deficits as predicted by simultaneous reduction of TcMEPs and SpMEPs in the face of normal SEPs. Electrical stimulation of the spinal cord primarily activates the corticospinal tract to mediate SpMEPs.

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.

Neurophysiologic Intraoperative Monitoring for Spine Surgery: A Practical Guide From Past to Present

Intraoperative neuromonitoring was introduced in the second half of the 20th century with the goal of preventing patient morbidity for patients undergoing complex operations of the central and peripheral nervous system. Since its early use for scoliosis surgery, the growth and utilization of IOM techniques expanded dramatically over the past 50 years to include spinal tumor resection and evaluation of cerebral ischemia. The importance of IOM has been broadly acknowledged, and in 1989, the American Academy of Neurology (AAN) released a statement that the use of SSEPs should be standard-of-care during spine surgery. In 2012, both the AAN and the American Clinical Neurophysiology Society (ACNS) recommended that: "Intraoperative monitoring (IOM) using SSEPs and transcranial MEPs be established as an effective means of predicting an increased risk of adverse outcomes, such as paraparesis, paraplegia, and quadriplegia, in spinal surgery." With a multimodal approach that combines SSEPs, MEPs, and sEMG with tEMG and D waves, as appropriate, sensitivity and specificity can be maximized for the diagnosis of reversible insults to the spinal cord, nerve roots, and peripheral nerves. As with most patient safety efforts in the operating room, IOM requires contributions from and communication between a number of different teams. This comprehensive review of neuromonitoring techniques for surgery on the central and peripheral nervous system will highlight the technical, surgical and anesthesia factors required to optimize outcomes. In addition, this review will discuss important trouble shooting measures to be considered when managing ION changes concerning for potential injury.

Visualization of electrical activity in the cervical spinal cord and nerve roots after ulnar nerve stimulation using magnetospinography

OBJECTIVE

To establish a method for magnetospinography (MSG) measurement after ulnar nerve stimulation and to clarify its characteristics.

METHODS

Using a 132-channel magnetoneurography system with a superconducting quantum interference device, cervical MSG measurements were obtained for 10 healthy volunteers after stimulation of the ulnar nerve at the elbow and the wrist, and neural current distribution was calculated and superimposed on the cervical X-ray images.

RESULTS

Neuromagnetic signals were obtained in all participants after applying the stimulus artifact removal algorithm. The measured magnetic field intensity after elbow stimulation was about twice that after wrist stimulation. Calculated neural currents flowed into the intervertebral foramina at C6/7 to T1/2 and propagated cranially along the spinal canal. The conduction velocity from the peak latency of inward currents at C5-C7 was 73.4 ± 19.6 m/s.

CONCLUSIONS

We successfully obtained MSG measurements after ulnar nerve stimulation. The neural currents flowed into the spinal canal from more caudal segments after ulnar nerve stimulation compared with median nerve stimulation, and these MSG measurements were effective in examining the spinal tracts at C5/6/7.

SIGNIFICANCE

This is the first report on the use of MSG to visualize electrical activity in the cervical spinal cord and nerve root after ulnar nerve stimulation.

Intraoperative neuromonitoring in spine deformity surgery: modalities, advantages, limitations, medicolegal issues - surgeons' views

In spine deformity surgery, iatrogenic neurologic injuries might occur due to the mechanical force applied to the spinal cord from implants, instruments, and bony structures, or due to ischemic changes from vessel ligation during exposure and cord distraction/compression during corrective manoeuvres.

Prompt reaction within the reversible phase (reducing of compressive/distractive forces) usually restores functionality of the spinal cord, but if those forces continue to persist, a permanent neurological deficit might be expected.

With monitoring of sensory pathways (dorsal column–medial lemniscus) by somatosensory-evoked potentials (SSEPs), such events are detected with a sensitivity of up to 92%, and a specificity of up to 100%.

The monitoring of motor pathways by transcranial electric motor-evoked potentials (TceMEPs) has a sensitivity and a specificity of up to 100%, but it requires avoidance of halogenated anaesthetics and neuromuscular blockades.

Different modalities of intraoperative neuromonitoring (IONM: SSEP, TceMEP, or combined) can be performed by the neurophysiologist, the technician or the surgeon. Combined SSEP/TceMEP performed by the neurophysiologist in the operating room is the preferable method of IONM, but it might be impractical or unaffordable in many institutions. Still, many spine deformity surgeries worldwide are performed without any type of IONM. Medicolegal aspects of IONM are different worldwide and in many cases some vagueness remains.

The type of IONM that a spinal surgeon employs should be reliable, affordable, practical, and recognized by the medicolegal guidelines.

Cite this article: EFORT Open Rev 2020;5:9-16. DOI: 10.1302/2058-5241.5.180032

Somatosensory evoked potential loss due to intraoperative pulse lavage during spine surgery: case report and review of signal change management

Intraoperative neurophysiologic monitoring (IONM) includes various neurophysiologic tests which assess the functional integrity of the central and peripheral nervous systems during surgical procedures which place these structures at risk for iatrogenic injury. The rational for using IONM is to provide timely feedback of changes in neural function to enable the reversal of such insult before the development of irreversible neural injury. There are various causes of intraoperative loss of neuromonitoring signals and it is important to systematically rule out all possible causes quickly and thoroughly in order to target the cause of signal loss, correct it and take measures to prevent the same in the future. One such rare cause, is targeted and pressurized cold (room temperature) irrigation of the surgical site, which may induce irritation and vasospasm leading to ischemia of the affected portion of the spinal cord, hence leading to signal changes. We present this case to stress the importance of having knowledgeable members of the team who are well acquainted with all aspects of monitoring in close proximity to the operating room, so as to minimize troubleshooting time. Furthermore, we suggest the use of warm (body temperature) saline during irrigation to the surgical site, especially when using pressurized irrigation systems.

The Efficacy of Intraoperative Neurophysiological Monitoring to Detect Postoperative Neurological Deficits in Transforaminal Lumbar Interbody Fusion Surgery

BACKGROUND

Despite the extensive use of intraoperative neurophysiological monitoring (IONM) in spinal procedures, there is no standard guideline for what types of IONM tests should be monitored during lumbar procedures with instrumentation. Moreover, the efficacy of IONM during transforaminal lumbar interbody fusion (TLIF) surgery in detecting postoperative neurological deficits has not been well described.

OBJECTIVE

To analyze waveform changes from individual IONM tests (somatosensory evoked potentials [SSEP], motor evoked potentials [MEP], and electromyography [EMG]) during TLIF and compare the sensitivity and specificity of these tests in order to determine the best combination to detect postoperative neurological deficits.

METHODS

Two hundred seventy-five consecutive TLIF cases with IONM between 2010 and 2014 were reviewed, and new postoperative sensory and motor deficits were documented. Sensitivity and specificity for each IONM test in detecting postoperative sensory and/or motor deficits were analyzed.

RESULTS

SSEP and EMG tests were performed on all 275 patients with 66 patients undergoing additional MEP tests. A total of 7 postoperative deficits have been reported: 2 sensory and 5 motor deficits. MEP test had high sensitivity (80.0%) and specificity (100%) in detecting motor deficits. However, SSEP changes failed to detect sensory deficits and EMG test had high false-positive rates for detecting both sensory (100%) and motor deficits (97.3%).

CONCLUSION

MEP test should be incorporated in monitoring protocols during spinal procedures that involve instrumentations below vertebral level L1 such as TLIF, as it provides high sensitivity and specificity in detecting postoperative motor deficits. In addition, we propose modifying the standard lower extremity SSEP monitoring protocol to correspond to the vertebral levels being operated on.

The impact and value of uni- and multimodal intraoperative neurophysiological monitoring (IONM) on neurological complications during spine surgery: a prospective study of 2728 patients

PURPOSE

We compared the value of different uni- and multimodal intraoperative neurophysiological monitoring (IONM) methods on the detection of neurological complications during spine surgery.

METHODS

IONM data derived from sensory spinal and cortical evoked potentials combined with continuous electromyography monitoring, motor evoked potentials and spinal recording were evaluated in relation to subsequent post-operative neurological changes. Patients were categorised based on their true-positive or true-negative post-operative neurological status.

RESULTS

In 2728 consecutive patients we had 909 (33.3%) IONM alerts. We had 8 false negatives (0.3%) with post-operative radicular deficit that completely recovered within 3 months, except for one. There was no false negative for spinal cord injury. 107 were true positives, and 23 were false positives. Multimodal IONM sensitivity and specificity were 93.0% and 99.1%, respectively. The frequency of neurological complications including minor deficits was 4.2% (n = 115), of which 0.37% (n = 10) were permanent. Analysis of the single IONM modalities varied between 13 and 81% to detect neurological complications compared with 93% when using all modalities.

CONCLUSION

Multimodal IONM is more effective and accurate in assessing spinal cord and nerve root function during spine surgeries to reduce both neurological complications and false-negative findings compared to unimodal monitoring. We recommend multimodal IONM in all complex spine surgeries. These slides can be retrieved from Electronic Supplementary Material.

The effect of positive changes during intraoperative monitoring of the functional improvement in patients with cervical compressive myelopathy

Background

Cervical compressive myelopathy (CCM) is a progressive, degenerative spine disease and the most common cause of spinal cord dysfunction in older individuals. Current clinical guidelines for spinal surgery recommend multimodal intraoperative monitoring (IOM) during spinal surgery as a reliable and valid diagnostic adjunct to assess spinal cord integrity. The aim of this study was to evaluate the effect of positive changes during IOM on the functional status in patients with CCM.

Methods

Patients who underwent spinal surgery with IOM due to CCM were enrolled. During the surgery, patients underwent IOM using motor evoked potential (MEP) and somatosensory evoked potential (SEP). MEP and SEP were checked before and immediately after decompression. A decrease in latency >10% or an increase in amplitude >50% was regarded as a “positive changes”. Subjects were divided according to the presence of positive changes. Motor scores of American Spinal Injury Association (ASIA) impairment scale and Korean version of Modified Barthel Index (K-MBI) were evaluated before and after operation.

Results

Twenty-nine patients underwent spinal surgery due to CCM. Eleven patients showed positive changes in MEP during IOM. When the two groups were compared, improvement rate in the ASIA motor score and K-MBI were significantly higher in patients with positive changes than in patients without positive changes at 1 month after surgery. However, 6 months after surgery, there were no significance differences between the groups. Regardless of positive change, nearly all patients suffered from neuropathic pain after operation.

Conclusion

Positive changes in MEP during IOM may affect functional improvement 1 month after operation and early discharge without significant complications in CCM patients. However, they do not affect the neuropathic pain and long-term functional outcome. Thus, tailored proper management is needed to achieve maximal functional recovery in each patient after cervical spinal decompression surgery.

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

BACKGROUND

To identify temporal changes to the demographics and utilization of intraoperative neuromonitoring (IONM) throughout the United States (U.S.).

METHODS

The National Inpatient Sample (NIS) database was queried for IONM of central and peripheral nervous electrical activity (ICD-9-CM 00.94) between 2008 and 2014. The NIS database represents a 20% sample of discharges from U.S. Hospitals, weighted to provide national estimates. Demographic and economic data were obtained which included the annual number of surgeries, age, sex, insurance type, location, and frequency of routine discharge.

RESULTS

The estimated use of IONM of central and peripheral nervous electrical activity increased 296%, from 31,762 cases in 2008 to 125,835 cases in 2014. Based on payer type, privately insured patients (45.0%), rather than Medicare (36.8%) or Medicaid patients (9.2%), were more likely to undergo IONM during spinal procedures. When stratifying by median income for patient zip code, there was a substantial difference in the rates of IONM between low (19.9%) and high-income groups (78.1%). IONM was significantly more likely to be utilized at urban teaching hospitals (72.9%) rather than nonteaching hospitals (25.0%) or rural centers (2.2%).

CONCLUSIONS

Over the last decade, there has been a massive increase of 296% in utilization of IONM during spine surgery. This is likely due to its proven benefit in reducing neurologic morbidity in spinal deformity surgery, while introducing minimal additional risk. While IONM may improve patient care, it is still rather isolated to teaching hospitals and patients from higher income zip codes.

Development of a modified model of spinal cord ischemia injury by selective ligation of lumbar arteries in rabbits

STUDY DESIGN

Experimental study.

OBJECTIVE

The aim of this study is to develop a modified model of spinal cord ischemia in rabbits.

SETTINGS

Shenzhen Key Laboratory of Spine Surgery, Shenzhen, China.

METHODS

In total, 20 New Zealand rabbits were divided into the following four groups according to the level of ligation of bilateral lumbar arteries: (1) group A, sham group, no ligation, n=5; (2) group B, ligation of bilateral lumbar arteries at three levels (L2-L4, n=5); (3) group C, ligation of bilateral lumbar arteries at four levels (L2-L5, n=5); and (4) group D, ligation of bilateral lumbar arteries at five levels (L1-L5, n=5). The latency of motor-evoked potentials was measured intraoperatively and the modified Tarlov grades were scored, followed by a histological observation of spinal cord, on the seventh day after surgery.

RESULTS

All 10 rabbits in Group A and Group B were electrophysiologically, neurologically and histologically normal. In Group C, moderate spinal cord ischemia injury was found in three of five rabbits: they had prolonged latency of motor-evoked potentials and neuronal karyopyknosis in the anterior horn of spinal cord, and the average Tarlov score was 4.2±0.8. In Group D, severe spinal cord ischemia injury was recorded in all the five rabbits: the latency of motor-evoked potential prolonged in one rabbit, whereas the waveform disappeared in four rabbits; loss of neurons and vacuolation of gray matter were seen in spinal cord sections, and the average Tarlov score was 0.6±0.9.

CONCLUSION

Selective ligation of lumbar arteries was a modified method to induce feasible and reproducible model of spinal cord ischemia in rabbits.

A multi-train electrical stimulation protocol facilitates transcranial electrical motor evoked potentials and increases induction rate and reproducibility even in patients with preoperative neurological deficits

This study sought to evaluate the facilitation effect of repetitive multi-train transcranial electrical stimulation (mt-TES) at 2 repetition rates on transcranial electrical motor evoked potential (Tc-MEP) monitoring during spinal surgery, and to assess the induction rate in patients with impaired motor function from a compromised spinal cord or spinal nerve. We studied 32 consecutive patients with impaired motor function undergoing cervical or thoracic spinal surgery (470 muscles). A series of 10 TESs with 5 pulse trains were preoperatively delivered at 2 repetition rates (1 and 5 Hz). All peak-topeak amplitudes of the MEPs of the upper and lower extremity muscles elicited by the 10 TESs were measured. The induction rates of the lower extremity muscles were also assessed with muscle and preoperative lower extremity motor function scores. In each of the muscles, MEP amplitudes were augmented by about 2-3 times at 1 Hz and 5-6 times at 5 Hz. Under the 5-Hz condition, all limb muscles showed significant amplification. Also, in all preoperative motor function score groups, the amplitudes and induction rates of the lower extremity muscles were significantly increased. Moreover, the facilitation effects tended to peak in the last half of the series of 10 TESs. In all score groups of patients with preoperative neurological deficits, repetitive mt-TES delivered at a frequency of 5 Hz markedly facilitated the MEPs of all limb muscles and increased the induction rate. We recommend this method to improve the reliability of intraoperative monitoring during spinal surgery.

Magnetospinography visualizes electrophysiological activity in the cervical spinal cord

Diagnosis of nervous system disease is greatly aided by functional assessments and imaging techniques that localize neural activity abnormalities. Electrophysiological methods are helpful but often insufficient to locate neural lesions precisely. One proposed noninvasive alternative is magnetoneurography (MNG); we have developed MNG of the spinal cord (magnetospinography, MSG). Using a 120-channel superconducting quantum interference device biomagnetometer system in a magnetically shielded room, cervical spinal cord evoked magnetic fields (SCEFs) were recorded after stimulation of the lower thoracic cord in healthy subjects and a patient with cervical spondylotic myelopathy and after median nerve stimulation in healthy subjects. Electrophysiological activities in the spinal cord were reconstructed from SCEFs and visualized by a spatial filter, a recursive null-steering beamformer. Here, we show for the first time that MSG with high spatial and temporal resolution can be used to map electrophysiological activities in the cervical spinal cord and spinal nerve.

Diagnostic Accuracy of Combined Multimodality Somatosensory Evoked Potential and Transcranial Motor Evoked Potential Intraoperative Monitoring in Patients With Idiopathic Scoliosis

STUDY DESIGN

Systematic review.

OBJECTIVE

The aim of the study was to determine the predictive value of combined multimodality somatosensory evoked potential (SSEP) and transcranial motor evoked potential (TcMEP) monitoring in detecting impending neurological injury during surgery for idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

The diagnostic of motor evoked potential monitoring and SSEP monitoring have been established. However, the predictive value of combined multimodality SSEP and TcMEP monitoring in detecting impending neurological injury during surgery for idiopathic scoliosis has not been evaluated.

METHODS

A systematic literature search was performed using PubMed/MEDLINE, Web of Science, and EMBASE from 1974 to January 2015. All titles and abstracts were independently reviewed by the authors. We included all studies that were (1) randomized controlled trials, prospective or retrospective cohort studies; (2) included patients with idiopathic scoliosis undergoing scoliosis correction surgery; (3) included multimodality SSEP and TcMEP monitoring during spinal surgery; (4) included immediate postoperative neurological assessment; (5) idiopathic scoliosis patient population n ≥25; and (6) published in English.

RESULTS

Seven studies comprising a total of 2052 patients with idiopathic scoliosis were included in our meta-analysis. The incidence of neurological deficit in this cohort was 0.93%. The pooled sensitivity, specificity, and Diagnostic Odds Ratio were 82.6% (95% CI 56.7%-94.5%), 94.4% (95% CI 85.1%-98.0%), and 106.16 (95% CI 24.952-451.667), respectively. The area under the curve was 0.928, indicating excellent discriminatory ability.

CONCLUSION

Idiopathic scoliosis corrective surgery patients who experience a new neurological deficit are 106.16 times more likely to have had an SSEP and/or TcMEP change during corrective procedures. The results of this meta-analysis demonstrate that combined multimodality SSEP and TcMEP monitoring possess some advantage over use of each alone, and that intraoperative neurophysiological monitoring may provide a valuable biomarker in detection of impending neurological injury.

LEVEL OF EVIDENCE

2.

Intraoperative Neurophysiological Monitoring for Endoscopic Endonasal Approaches to the Skull Base: A Technical Guide

Intraoperative neurophysiological monitoring during endoscopic, endonasal approaches to the skull base is both feasible and safe. Numerous reports have recently emerged from the literature evaluating the efficacy of different neuromonitoring tests during endonasal procedures, making them relatively well-studied. The authors report on a comprehensive, multimodality approach to monitoring the functional integrity of at risk nervous system structures, including the cerebral cortex, brainstem, cranial nerves, corticospinal tract, corticobulbar tract, and the thalamocortical somatosensory system during endonasal surgery of the skull base. The modalities employed include electroencephalography, somatosensory evoked potentials, free-running and electrically triggered electromyography, transcranial electric motor evoked potentials, and auditory evoked potentials. Methodological considerations as well as benefits and limitations are discussed. The authors argue that, while individual modalities have their limitations, multimodality neuromonitoring provides a real-time, comprehensive assessment of nervous system function and allows for safer, more aggressive management of skull base tumors via the endonasal route.

The Efficacy of Intraoperative Neurophysiological Monitoring Using Transcranial Electrically Stimulated Muscle-evoked Potentials (TcE-MsEPs) for Predicting Postoperative Segmental Upper Extremity Motor Paresis After Cervical Laminoplasty

STUDY DESIGN

Prospective study.

OBJECTIVE

To investigate the efficacy of transcranial electrically stimulated muscle-evoked potentials (TcE-MsEPs) for predicting postoperative segmental upper extremity palsy following cervical laminoplasty.

SUMMARY OF BACKGROUND DATA

Postoperative segmental upper extremity palsy, especially in the deltoid and biceps (so-called C5 palsy), is the most common complication following cervical laminoplasty. Some papers have reported that postoperative C5 palsy cannot be predicted by TcE-MsEPs, although others have reported that it can be predicted.

METHODS

This study included 160 consecutive cases that underwent open-door laminoplasty, and TcE-MsEP monitoring was performed in the biceps brachii, triceps brachii, abductor digiti minimi, tibialis anterior, and abductor hallucis. A >50% decrease in the wave amplitude was defined as an alarm point. According to the monitoring alarm, interventions were performed, which include steroid administration, foraminotomies, etc.

RESULTS

Postoperative deltoid and biceps palsy occurred in 5 cases. Among the 155 cases without segmental upper extremity palsy, there were no monitoring alarms. Among the 5 deltoid and biceps palsy cases, 3 had significant wave amplitude decreases in the biceps during surgery, and palsy occurred when the patients awoke from anesthesia (acute type). In the other 2 cases in which the palsy occurred 2 days after the operation (delayed type), there were no significant wave decreases. In all of the cases, the palsy was completely resolved within 6 months.

DISCUSSION

The majority of C5 palsies have been reported to occur several days after surgery, but some of them have been reported to occur immediately after surgery. Our results demonstrated that TcE-MsEPs can predict the acute type, whereas the delayed type cannot be predicted.

CONCLUSIONS

A >50% wave amplitude decrease in the biceps is useful to predict acute-type segmental upper extremity palsy. Further examination about the interventions for monitoring alarm will be essential for preventing palsy.

Intraoperative neurophysiological monitoring in spinal surgery

Recently, many surgeons have been using intraoperative neurophysiological monitoring (IOM) in spinal surgery to reduce the incidence of postoperative neurological complications, including level of the spinal cord, cauda equina and nerve root. Several established technologies are available and combined motor and somatosensory evoked potentials are considered mandatory for practical and successful IOM. Spinal cord evoked potentials are elicited compound potentials recorded over the spinal cord. Electrical stimulation is provoked on the dorsal spinal cord from an epidural electrode. Somatosensory evoked potentials assess the functional integrity of sensory pathways from the peripheral nerve through the dorsal column and to the sensory cortex. For identification of the physiological midline, the dorsal column mapping technique can be used. It is helpful for reducing the postoperative morbidity associated with dorsal column dysfunction when distortion of the normal spinal cord anatomy caused by an intramedullary cord lesion results in confusion in localizing the midline for the myelotomy. Motor evoked potentials (MEPs) consist of spinal, neurogenic and muscle MEPs. MEPs allow selective and specific assessment of the functional integrity of descending motor pathways, from the motor cortex to peripheral muscles. Spinal surgeons should understand the concept of the monitoring techniques and interpret monitoring records adequately to use IOM for the decision making during the surgery for safe surgery and a favorable surgical outcome.

Intraoperative neurophysiological monitoring during resection of intradural extramedullary spinal cord tumors: experience with 100 cases

BACKGROUND

Intradural-extramedullary spinal cord tumor surgery is common. Unlike intramedullary spinal cord tumor surgery, where intraoperative neurophysiological monitoring (IONM) has been described extensively, the application of IONM has not been described in this context, and its relevance has not been investigated.

METHODS

From 2001 to 2012, 100 patients underwent intradural-extramedullary spinal cord tumor resection with IONM. Preoperative and postoperative clinical evaluations were completed retrospectively, using a modified McCormick grading scale and correlated with IONM monitorability and dynamics. IONM consisted of transcranial motor evoked potentials (tcMEP), spinal (D wave) and muscle generators, somatosensory evoked potentials (SSEP), and electromyography (EMG). Both short-term and long-term clinical evaluations were performed. Patient demographics, tumor type, span, location, and morphologic complexity were analyzed.

RESULTS

Surgeries were performed for resection of schwannomas (33 %), meningiomas (22 %), ependymomas (12 %), and other pathologies (20 %); pathology was unknown in 13 % of patients. Tumor locations were cervical in 21 %, thoracic in 46 %, thoracolumbar in 7 %, lumbar 20 %, and not specified in 6 %. Tumors spanned an average of 2.2 spinal levels. Monitorability was 97 and 67 % with tcMEP and SSEP modalities respectively. D waves were monitorable in 73 % of attempts. Intraoperative tcMEP changes were reported in 29 cases with 14 resolved intraoperatively, There were one false-negative outcome and five true-positive outcomes. For SSEP, 13 changes were noted and three resolved; there were three false-negative results and one true-positive result. For D wave monitoring there were two intraoperative changes with none resolved leading to one false negative and one true positive result. With a multimodality approach incorporating any change in evoked potential, IONM demonstrated sensitivity of 0.82, specificity of 0.95, positive predictive value of 0.82, and a negative predictive value of 0.95.

CONCLUSIONS

IONM is feasible and useful in the context of intradural-extramedullary spinal cord surgery for identifying iatrogenic injury to the spinal cord.

Technological innovation in neurosurgery: a quantitative study

OBJECT

Technological innovation within health care may be defined as the introduction of a new technology that initiates a change in clinical practice. Neurosurgery is a particularly technology-intensive surgical discipline, and new technologies have preceded many of the major advances in operative neurosurgical techniques. The aim of the present study was to quantitatively evaluate technological innovation in neurosurgery using patents and peer-reviewed publications as metrics of technology development and clinical translation, respectively.

METHODS

The authors searched a patent database for articles published between 1960 and 2010 using the Boolean search term "neurosurgeon OR neurosurgical OR neurosurgery." The top 50 performing patent codes were then grouped into technology clusters. Patent and publication growth curves were then generated for these technology clusters. A top-performing technology cluster was then selected as an exemplar for a more detailed analysis of individual patents.

RESULTS

In all, 11,672 patents and 208,203 publications related to neurosurgery were identified. The top-performing technology clusters during these 50 years were image-guidance devices, clinical neurophysiology devices, neuromodulation devices, operating microscopes, and endoscopes. In relation to image-guidance and neuromodulation devices, the authors found a highly correlated rapid rise in the numbers of patents and publications, which suggests that these are areas of technology expansion. An in-depth analysis of neuromodulation-device patents revealed that the majority of well-performing patents were related to deep brain stimulation.

CONCLUSIONS

Patent and publication data may be used to quantitatively evaluate technological innovation in neurosurgery.

Median effective effect-site concentration of sufentanil for wake-up test in adolescents undergoing surgery: a randomized trial

BACKGROUND

To determine the median effective concentration of sufentanil as an analgesic during wake-up tests after sevoflurane anesthesia during surgery for adolescent idiopathic scoliosis (AIS).

METHODS

This is a randomised controlled trial. Sixty patients aged 13-18 years scheduled for AIS surgery were randomized into six groups of 10 patients each to receive target effect-site concentrations of sufentanil of 0.19, 0.1809, 0.1723, 0.1641, 0.1563, and 0.1489 ng/ml (target concentration ratio, 1.05). Wake-up time was recorded. Median EC50 and 95% confidence interval (CI) for sufentanil target-controlled infusion (TCI) were determined using Kärber's method. The primary outcome was median EC50 for sufentanil TCI as an analgesic during the wake-up test after sevoflurane anesthesia during surgery for AIS.

RESULTS

The EC50 and 95% CI of sufentanil TCI were 0.1682 ng/ml and 0.1641 ~ 0.1724 ng/ml, respectively.

CONCLUSIONS

The EC50 of sufentanil TCI was 0.1682 ng/ml (95% CI: 0.1641 ~ 0.1724 ng/ml) during sevoflurane anesthesia in adolescents undergoing surgery for idiopathic scoliosis with intraoperative wake-up tests.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: ChiCTR-TTRCC-12002696.

Novel aspects of spinal cord evoked potentials (SCEPs) in the evaluation of dorso-ventral and lateral mechanical impacts on the spinal cord

OBJECTIVES

The aim of the current study was to mimic mechanical impacts on the spinal cord by manifesting the effects of dorsoventral (DVMP) and lateral (LMP) mechanical pressure on neural activity to address points to be considered during surgery for different purposes, including spinal cord decompression.

APPROACHES

Spinal cords of anesthetized rats were compressed at T13. Different characteristics of axons, including vulnerability, excitability, and conduction velocity (CV), in response to promptness, severity, and duration of pressure were assessed by spinal cord evoked potentials (SCEPs). Real-time SCEPs recorded at L4-5 revealed N1, N2, and N3 peaks that were used to represent the activity of injured sensory afferents, interneurons, and MN fibers. The averaged SCEP recordings were fitted by trust-region algorithm to find the equivalent Gaussian and polynomial equations.

MAIN RESULTS

The pyramidal and extrapyramidal pathways possessed CVs of 3-11 and 16-80 m s(-1), respectively. DVMP decreased the excitability of myelinated neural fibers in antidromic and orthodromic pathways. The excitability of fibers in extrapyramidal and pyramidal pathways of lateral corticospinal (LCS) and anterior corticospinal (ACS) tracts decreased following LMP. A significant drop in the amplitude of N3 and its conduction velocity (CV) revealed higher susceptibility of less-myelinated fibers to both DVMP and LMP. The best parametric fitting model for triplet healthy spinal cord CAP was a six-term Gaussian equation (G6) that fell into a five-term equation (G5) at the complete compression stage.

SIGNIFICANCE

The spinal cord is more susceptible to dorsoventral than lateral mechanical pressures, and this should be considered in spinal cord operations. SCEPs have shown promising capabilities for evaluating the severity of SCI and thus can be applied for diagnostic or prognostic intraoperative monitoring (IOM).

How to make the best use of intraoperative motor evoked potential monitoring? Experience in 1162 consecutive spinal deformity surgical procedures

STUDY DESIGN

A retrospective study of 1162 consecutive patients who underwent spinal deformity surgical procedures at our spine center from January 2010 to December 2013.

OBJECTIVE

To develop and evaluate a protocol of intraoperative motor evoked potential (MEP) monitoring with the warning criteria we had established on the basis of our clinical experiences and the review of previous literature.

SUMMARY OF BACKGROUND DATA

Though MEPs monitoring have become widely used in spinal deformity surgery, different alarm criteria and response protocol used in different studies compromised their comparability; Furthermore, high false-positive rate of MEP reported by previous studies has become an increasingly prominent problem that will limit its clinical use and development.

METHODS

The intraoperative monitoring data of 1162 consecutive patients who underwent spinal deformity surgical procedures at our spine center were retrospectively analyzed. Age, sex, diagnosis, preoperative neurological status, intraspinal anomalies, baseline MEP, and MEP change were collected. The protocol with the warning criteria we had established was used. The false-positive rate, false-negative rate, and positive predictive value were calculated.

RESULTS

Significant intraoperative changes were seen in the MEP data in 52 (4.4%) of all the cases. In 25 cases among which, significant MEP changes were synchronously and logically associated with high-risk surgical maneuver (pedicle screw insertion, osteotomy, correction, etc.). The false-positive rate of MEP monitoring was 0.26% (3/1140), whereas the sensitivity and specificity of MEP for detection of clinically significant intraoperative cord injury were 100% and 99.7%, respectively. The positive predictive value of a MEP alert in terms of a new postoperative neurological deficit was 83.3%.

CONCLUSION

Our study indicates that the appropriate use of MEP monitoring based on our protocol is able to obtain satisfying sensitivity and specificity and thus provide important information for intraoperative decision making.

Efficacy of biphasic transcranial electric stimulation in intraoperative motor evoked potential monitoring for cervical compression myelopathy

STUDY DESIGN

Retrospective analysis of prospectively collected data from consecutive patients undergoing 2 methods of transcranial electrical motor evoked potential (TCE-MEP) monitoring during cervical spine surgery.

OBJECTIVE

To investigate the efficacy of biphasic transcranial electric stimulation, the deviation rate, amplitude of TCE-MEPs, complications, and sensitivity and specificity of TCE-MEP monitoring were compared between the biphasic and conventional monophasic stimulation methods.

SUMMARY OF BACKGROUND DATA

With biphasic stimulation, unlike monophasic stimulation, measurement time can be reduced considerably because a single stimulation elicits bilateral responses almost simultaneously. However, no study has yet reported a detailed comparison of the 2 methods.

METHODS

Examination 1: Amplitude and derivation rate of TCE-MEPs was compared for monophasic and biphasic stimulation in the same 31 patients with cervical compression myelopathy. Examination 2: Sensitivity, specificity, and complications of TCE-MEP monitoring were compared in 200 patients with cervical compression myelopathy who received monophasic or biphasic stimulation (100 patients each) during intraoperative monitoring.

RESULTS

Examination 1: Derivation rates of biphasic stimulation in the deltoid, biceps brachii, abductor digiti minimi, and flexor hallucis brevis muscles were the same or higher than for monophasic stimulation. TCE-MEP amplitudes elicited by biphasic stimulation compared with monophasic stimulation were significantly larger in the biceps (paired t, P < 0.0001), but similar in the other 3 muscles. Examination 2: In the biphasic and monophasic stimulation groups, warnings were issued to surgeons in 10 and 11 cases, for a sensitivity of 100% for both groups and specificity of 97.8% and 96.7%, respectively. No complications related to stimulation were observed in any of the 200 patients.

CONCLUSION

Biphasic stimulation had similar or higher derivation rates and equivalent sensitivity and specificity than monophasic stimulation. No complications were observed for either stimulation method. Biphasic stimulation is an effective TCE-MEP monitoring method for cervical spine surgery that may also reduce measurement time.

LEVEL OF EVIDENCE

4.

History of spinal osteotomy

Spinal deformity is one of the oldest known diseases with descriptions documented many of the earliest civilizations. Historical treatments have had little efficacy, especially in adults. However, in the modern era, there has been a rapid expansion of new technologies and surgical techniques aided by advances in supportive care that now allow the spinal surgeon to have powerful tools to correct spinal deformity. In this manuscript, we review the origins of spinal deformity surgery and the development of spinal instrumentation. The focus of the manuscript is to review the relationship of these developments to the implementation of spinal osteotomies for deformity correction.

Snapshot of 1973 and 1974: critical thinkers and contemporary research ideas in neurosurgical anesthesia during the first years of SNACC

The year 2012 marks the 40th anniversary of the Society of Neuroscience in Anesthesiology and Critical Care (SNACC). To celebrate this occasion, we provide a review, speculative synthesis, and commentary addressing research relevant to neurosurgical anesthesiology in 1973 and 1974--the early years of SNACC. We address topics such as effects of anesthetic drugs, neuroprotection, cerebral physiology, and monitoring as they relate to the perioperative care of neurosurgical patients or patients experiencing or at risk for neurological disorders. Our hypothesis is that a review of these publications will identify the foundations of research and practice concepts that persist until today and will also identify concepts that have dwindled or outright disappeared.

Keratan sulfate restricts neural plasticity after spinal cord injury

Chondroitin sulfate (CS) proteoglycans are strong inhibitors of structural rearrangement after injuries of the adult CNS. In addition to CS chains, keratan sulfate (KS) chains are also covalently attached to some proteoglycans. CS and KS sometimes share the same core protein, but exist as independent sugar chains. However, the biological significance of KS remains elusive. Here, we addressed the question of whether KS is involved in plasticity after spinal cord injury. Keratanase II (K-II) specifically degraded KS, i.e., not CS, in vivo. This enzyme digestion promoted the recovery of motor and sensory function after spinal cord injury in rats. Consistent with this, axonal regeneration/sprouting was enhanced in K-II-treated rats. K-II and the CS-degrading enzyme chondroitinase ABC exerted comparable effects in vivo and in vitro. However, these two enzymes worked neither additively nor synergistically. These data and further in vitro studies involving artificial proteoglycans (KS/CS-albumin) and heat-denatured or reduced/alkylated proteoglycans suggested that all three components of the proteoglycan moiety, i.e., the core protein, CS chains, and KS chains, were required for the inhibitory activity of proteoglycans. We conclude that KS is essential for, and has an impact comparable to that of CS on, postinjury plasticity. Our study also established that KS and CS are independent requirements for the proteoglycan-mediated inhibition of axonal regeneration/sprouting.