Neurophysiological identification of position-induced neurologic injury during anterior cervical spine surgery

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.

Unilateral abnormality of initial motor-evoked potential in the upper limb detected during lumbar spine surgery: a case report

BACKGROUND

We present a case with abnormal findings of initial motor-evoked potential (MEP) in the left upper limb after prone positioning during lumbar spine surgery.

CASE PRESENTATION

A 71-year-old man with bilateral lower extremity numbness without a history of preexisting motor weakness underwent L3-5 spinal fenestration. Initial MEP monitoring after prone positioning revealed markedly prolonged latency and lower amplitude in the left abductor pollicis brevis (APB). Because the left upper limb somatosensory-evoked potentials had normal values, a position-related impending peripheral nerve injury located between the neck and the forearm was excluded. Postoperative examination revealed that MEP abnormality in the left APB was caused by carpal tunnel syndrome.

CONCLUSIONS

Abnormal initial MEP from the upper limb was unexpectedly detected after prone positioning during lumbar spine surgery. The condition was caused by preexisting carpal tunnel syndrome.

A Novel Intraoperative Posture-Adjustment Apparatus for Correction of Cervical Lordosis in Anterior Cervical Surgery

OBJECTIVE

Cervical alignment is a crucial factor related to the success of anterior cervical surgical procedures. In patients with severe spinal cord compression, a traditional neck pillow (TNP) may not adequately correct cervical position during surgery. Therefore, the aim of this study was to introduce this innovative intraoperative posture-adjustment apparatus (IPAA), and explored its clinical and radiological results in cervical angle correction against TNP in patients who had undergone anterior cervical surgery.

METHODS

The clinical and radiological data of 86 patients who underwent anterior cervical surgery with a minimum follow-up period of 1 year were retrospectively reviewed. Of these, 58 patients underwent IPAA, whereas 28 underwent TNP. Radiological parameters such as the degree of C2-C7 lordosis (CL), functional spinal unit angle (FSUA), C7 slope (C7S), fusion rate, and adjacent segment disease (ASD) were recorded and compared between the groups. Clinical outcomes including the Japanese Orthopaedic Association (JOA), neck disability index (NDI), visual analogue scale (VAS) for neck and arm were recorded. Complications such as kyphosis, dysphagia, Braden Scale score, revision surgery, hematoma, cerebrospinal fluid leakage, wound infection, and deep venous thrombosis were also recorded. The independent t-test or Mann-Whitney U test was used to compare continuous data, and categorical variables were assessed using the Pearson's chi-square test or Fisher's exact test.

RESULTS

Compared with the pre-operative data, the post-operative CL, FSUA, and C7S were significantly increased in both groups. CL, FSUA, and C7S in the IPAA group (14.44 ± 4.94°, 7.36 ± 2.91°, 16.54 ± 4.63°) were significantly higher than those in the TNP group (7.17 ± 8.19°, 4.99 ± 5.36°, 14.19 ± 4.48°; P < 0.05). Although there were no significant differences between the groups in terms of VAS arm and JOA scores, the post-operative and final follow-up NDI and VAS neck scores in the IPAA group were significantly lower than those in the TNP group (p < 0.05). At the last follow-up, the TNP group had significantly more kyphotic patients than the IPAA group (2 vs. 0, p = 0,041). There was no significant difference between the groups in terms of fusion rate, ASD, or complications such as dysphagia, Braden's Scale score, revision surgery, hematoma, cerebrospinal fluid leakage, wound infection, or deep venous thrombosis.

CONCLUSION

IPAA was shown to be more effective than TNP in adjusting cervical alignment (CL, FSUA, and C7S). These findings suggest that IPAA could be used as an alternative way to TNP in neck setting and cervical alignment adjustment and IPAA could potentially improve clinical outcomes after anterior cervical surgery.

Confirming a C5 Palsy with a Motor Evoked Potential Trending Algorithm during Insertion of Cervical Facet Spacers: A Case Study

The use of cervical facet spacers has shown favorable clinical results in the treatment of cervical spondylotic disease; however, there are limited data regarding neurological complications associated with the procedure. This case report demonstrates the specificity of multi-myotomal motor evoked potentials (MEPs) in detecting acute postoperative C5 palsy following placement of facet spacers. A posterior cervical fusion with decompression and instrumentation involving DTRAX (Providence Medical Technology; Lafayette, CA) was used to treat a patient with cervical stenosis and myelopathy. Intraoperative neurophysiological monitoring (IONM) consisting of MEPs, somatosensory evoked potentials (SSEPs), and free-run electromyography (EMG), was used throughout the procedure. Immediately following the placement of the DTRAX spacers at C4-5, a decrease in amplitudes from the right deltoid and biceps MEP recordings (>65%) was detected. All other IONM modalities remained stable; it is noteworthy that there was an absence of mechanically elicited EMG. A novel post-alert regression analysis trending algorithm of MEP amplitudes confirmed the visual alert. This warning along with an intraoperative computed tomography (CT) scan of the cervical spine subsequently resulted in the decision to remove one of the facet spacers. Surgical intervention did not result in recovery of the aforementioned MEP recordings, which remained attenuated at the time of wound closure. Postoperatively, the patient exhibited an immediate right C5 palsy (2/5). A post-surgery application of the trending algorithm demonstrated that it correlated to the visual alert until the end of monitoring.

The value of intraoperative neurophysiological monitoring during positioning in pediatric scoliosis correction: A case report

Introduction

Prone position during posterior spine surgery can represent a potentially risky procedure for the nervous system. Infrequent injuries due to prone positioning consist of subtle spinal cord infarction or myelopathy that can be promptly detected by intraoperative neurophysiological monitoring (IONM), if applied in this phase of surgery. Here, we report a case that stresses the value of IONM even in detecting spinal positioning-related neurological complications during kyphoscoliosis correction.

Case presentation

A 3-year-old child with a severe thoracic kyphoscoliosis with the angle in the tract T5-T6 underwent an early treatment of scoliosis with growing rods. Before instrumentation or the reduction maneuver, lower limb somatosensory and motor responses disappeared. The patient was repositioned with neck and chest in a more protective position and neuromonitoring signals returned to baseline. The surgery could be completed and the patient had no postoperative neurologic or vascular deficits.

Conclusion

Our findings suggest the importance of extending neuromonitoring in the early phases of anesthesia induction and patient positioning during corrective spinal deformity surgery.

Transcranial electric stimulation motor evoked potentials for cervical spine intraoperative monitoring complications: systematic review and illustrative case of cardiac arrest

PURPOSE

We show a systematic review of known complications during intraoperative neuromonitoring (IONM) using transcranial electric stimulation motor evoked potentials (TES-MEP) on cervical spine surgery, which provides a summary of the main findings. A rare complication during this procedure, cardiac arrest by cardioinhibitory reflex, is also described.

METHODS

Findings of 523 scientific papers published from 1995 onwards were reviewed in the following databases: CENTRAL, Cochrane Library, Embase, Google Scholar, Ovid, LILACS, PubMed, and Web of Science. This study evaluated only complications on cervical spine surgery undergoing TES-MEP IONM.

RESULTS

The review of the literature yielded 13 studies on the complications of TES-MEP IONM, from which three were excluded. Five studies are case series; the rest are case reports. Overall, 169 complications on 167 patients were reported in a total of 38,915 patients, a global prevalence of 0.43%. The most common complication was tongue-bite in 129 cases, (76.3% of all complication events). Tongue-bite had a prevalence of 0.33% (CI 95%, 0.28-0.39%) in all patients on TES-MEP IONM. A relatively low prevalence of severe complications was found: cardiac-arrhythmia, bradycardia and seizure, the prevalence of this complications represents only one case in all the sample. Alongside, we report the occurrence of cardiac arrest attributable to TES-MEP IONM.

CONCLUSIONS

This systematic review shows that TES-MEP is a safe procedure with a very low prevalence of complications. To our best knowledge, asystole is reported for the first time as a complication during TES-MEP IONM.

Single-port transaxillary robotic thyroidectomy (START): 200-cases with two-step retraction method

Background

This study aims to report the results of a pioneering clinical study using the single-port transaxillary robotic thyroidectomy (START) for 200 patients with thyroid tumor and to introduce our novel two-step retraction method.

Methods

START was performed on consecutive 200 patients using the da Vinci Single-Port (SP) robot system from January 2019 to September 2020 at the Yonsei University Health System, Seoul, Korea. The novel two-step retraction technique, in which a 3.5 cm long incision is made along the natural skin crease, was used for the latter 164 patients. The surgical outcome and invasiveness of the SP two-step retraction method were analyzed.

Results

Among the 200 cases who underwent START, 198 were female and 2 were male, with a mean age of 34.7 (range: 13–58 years). Thyroid lobectomy was performed for 177 patients and total thyroidectomy was performed for 23 patients. Ten patients had benign thyroid nodules, whereas the other 190 had thyroid malignancy. The mean body mass index (BMI) was 22.2 ± 3.7 kg/m² (range: 15.9–37.0 kg/m²). All of the operations were performed successfully without any open conversions, and patients were discharged on postoperative day 3 or 4 without significant complication. The mean operative time for thyroid lobectomy with the two-step retraction method was 116.69 ± 23.23 min, which was similar to that in the conventional robotic skin flap method (115.33 ± 17.29 min). We could minimize the extent of the robotic skin flap dissection with the two-step retraction method.

Conclusions

START is a practical surgical method. By employing the new two-step retraction method, we can maximize the cosmetic and functional benefits for patients and reduce the workload fatigue of surgeons by increasing robotic dependency.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00464-021-08837-9.

A novel approach of using brachial plexus blockade as an experimental model for diagnosis of intraoperative nerve dysfunction with somatosensory evoked potentials: a blinded proof-of-concept study

PURPOSE

Intraoperative nerve dysfunction has been difficult to investigate because of its rarity and unpredictable occurrence. The diagnostic test attributes of nerve function monitors have not been clearly defined. This proof-of-concept study aimed to assess the feasibility of using brachial plexus blockade (BPB) in awake patients as an experimental model for nerve dysfunction to characterize the diagnostic test attributes of somatosensory evoked potentials (SSEPs).

METHODS

We obtained baseline SSEPs and neurologic function in patients and subsequently placed BPBs (experimental model) to generate progressive states of nerve dysfunction. We monitored SSEP changes (index test) and neurologic symptoms (reference standard) simultaneously during the onset of BPB to determine the temporal relationships and diagnostic test attributes of SSEPs.

RESULTS

Brachial plexus blockade produced differential motor and sensory dysfunction that allowed simultaneous clinical and neurophysiologic assessment. One hundred and fifty-seven pairs of multiple data points from 14 patients were included for final analysis. The onset of abnormal SSEP signals almost always preceded the onset of neurologic symptoms. The sensitivities and specificities of SSEP to detect the impairment of power (motor rating score ≤ 4/5), cold sensation, and two-point discrimination were 100% and 67%, 99% and 55%, and 100% and 46%, respectively.

CONCLUSION

This study found that BPB can produce sufficient differential nerve dysfunction to allow adequate evaluation of the diagnostic test attributes of SSEPs as a nerve monitor. The results of this study may stimulate further work on refining intraoperative nerve dysfunction models and diagnostic nerve function monitors.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT03409536); registered 24 January 2018.

Reducing the Risk and Impact of Brachial Plexus Injury Sustained From Prone Positioning-A Clinical Commentary

INTRODUCTION

Prone positioning is deployed as a critical treatment for improving oxygenation in patients with Acute Respiratory Distress Syndrome. This regimen is currently highly prevalent in the COVID-19 pandemic. The pandemic has brought about increased concern about how best to safely avoid brachial plexus injuries when caring for unconscious proned patients.

METHODS

A review of the published literature on brachial plexus injuries secondary to proning ventilated patients was performed. This was combined with a review of available international critical care guidelines in order to produce a succinct set of guidelines to aid critical care departments in reducing brachial plexus injuries during these challenging times.

DISCUSSION

There is no one manner in which prone positioning an unconscious patient can be made universally safe. This paper provides 6 key steps to reducing the incidence of brachial plexus injuries while proning and suggests a safe and sensible management and referral pathway for the conscious patient in which a brachial plexus injury is identified.

CONCLUSION

There is in truth no completely safe position for every patient and certainly there will be anomalies in anatomy that will predispose certain individuals to nerve injury. Thus the injury rate cannot be reduced to zero but an understanding of the principles of protection will inform those undertaking positioning.

Protecting prone positioned patients from facial pressure ulcers using prophylactic dressings: A timely biomechanical analysis in the context of the COVID-19 pandemic

Prone positioning is used for surgical access and recently in exponentially growing numbers of coronavirus disease 2019 patients who are ventilated prone. To reduce their facial pressure ulcer risk, prophylactic dressings can be used; however, the biomechanical efficacy of this intervention has not been studied yet. We, therefore, evaluated facial soft tissue exposures to sustained mechanical loads in a prone position, with versus without multi‐layered silicone foam dressings applied as tissue protectors at the forehead and chin. We used an anatomically realistic validated finite element model of an adult male head to determine the contribution of the dressings to the alleviation of the sustained tissue loads. The application of the dressings considerably relieved the tissue exposures to loading. Specifically, with respect to the forehead, the application of a dressing resulted in 52% and 71% reductions in soft tissue exposures to effective stresses and strain energy densities, respectively. Likewise, a chin dressing lowered the soft tissue exposures to stresses and strain energy densities by 78% and 92%, respectively. While the surgical context is clear and there is a solid, relevant need for biomechanical information regarding prophylaxis for the prone positions, the projected consequences of the coronavirus pandemic make the present work more relevant than ever before.

Decreasing the prospect of upper extremity neuropraxia during robotic assisted laparoscopic prostatectomy: a novel technique

Risk of intraoperative neuropathic injury in minimally invasive surgery has been established as a leading complication. Continuous intraoperative neuromonitoring (IONM), such as upper extremity somatosensory evoked potentials (ueSSEPs), to decrease peripheral nerve injury due to positional stress has been described. Robotic-assisted laparoscopic prostatectomy (RALP) requires steep Trendelenberg, which may predispose patients to upper extremity neuropraxia. Subdermal stimulating electrodes were placed on the patients' bilateral wrists over the ulnar nerve and the nerve was stimulated. Realtime waveforms were compared to baseline data to prevent and detect injury to the ulnar nerve. Established intervention criteria, indicating risk for neuropathic damage necessitating intraoperative patient repositioning, was a 50% loss in amplitude or a 10% increase in latency. One hundred and forty three patients received RALP with IONM. 17 of 143 patients (11.8%) met ueSSEP intervention criteria. Only weight was significantly different between the two groups (p = 0.04). Mean reduction in amplitude was 79.9% (SE 4.1). Average amplitude loss duration was 22 min (SE 4.0). Weight and BMI were correlated to the degree of amplitude reduction (p = 0.03 and < 0.01), while operative time and DM approached significance (p = 0.09 and p = 0.14). This is the first study to use IONM to reduce the risk of nerve injury during genitourinary surgery. Realtime nerve monitoring using ueSSEP allowed for upper extremity intraoperative monitoring and repositioning. This may decrease the risk of upper extremity neuropraxia due to malpositioning during RALP. Weight and BMI were identified as risk factors for possible nerve injury. Further data collection and analysis to preoperatively stratify patients for application of IONM during RALP is currently ongoing.

Positional disappearance of motor evoked potentials is much more likely to occur in non-idiopathic scoliosis

PURPOSE

This study evaluates intraoperative disappearance of motor waveforms related to patient positioning in neurologically asymptomatic patients with spinal deformity.

METHODS

This is a retrospective review of 190 neurologically asymptomatic patients aged seven to 17 years planned for posterior instrumentation under neuromonitoring. There were 159 patients with adolescent idiopathic scoliosis and 31 patients with secondary scoliosis. Patients underwent surgery with transcranial electric stimulation motor evoked potentials (TES-MEPs). In case of abnormal findings, surgery was temporarily discontinued and necessary measures undertaken. In case of permanent signal disappearance surgery was definitively discontinued.

RESULTS

Six patients showed permanent loss of signal during early stages of surgery. These patients had a mean major curve of 64° Cobb angle and a mean thoracic kyphosis (D2 to D12) of 72°. The 184 remaining patients had a mean major curve of 50° Cobb angle and a thoracic kyphosis of 35°. A retrospective descriptive review of the patients' radiographs shows hyperkyphosis to be the common ground between the six secondary scoliosis cases. Gradual preoperative traction maintained during the surgery applied in two of these patients taken back to surgery six months later was associated with maintenance of TES-MEP signals throughout the surgery.

CONCLUSION

This study shows that positional permanent loss of neuromonitoring signals is more likely to occur in patients with secondary scoliosis and hyperkyphosis shown to have sharper spine deformity and suspected to have a more vulnerable spinal cord. Gradual skeletal traction performed in two of these patients and maintained during surgery showed promising results.

LEVEL OF EVIDENCE

IV.

Somatosensory evoked potential: Preventing brachial plexus injury in transaxillary robotic surgery

OBJECTIVES/HYPOTHESIS

The potential for brachial plexopathy due to arm positioning is a major concern regarding the robotic transaxillary approach. Intraoperative nerve monitoring via somatosensory evoked potential (SSEP) has been suggested to prevent such injury. In this study, we examined the use of SSEP in detecting imminent brachial plexus traction during robotic transaxillary thyroid and parathyroid surgery.

STUDY DESIGN

Retrospective case series.

METHODS

A analysis was performed for all patients undergoing robotic transaxillary surgery with continuous intraoperative SSEP monitoring at a North American institution between 2015 and 2017. A significant intraoperative SSEP change was defined as a decrease in signal amplitude of >50% or an increase in latency of >10% from baseline established during preoperative positioning.

RESULTS

One hundred thirty-seven robotic transaxillary surgeries using SSEP monitoring were performed on 123 patients. Seven patients (5.1%) developed significant changes, with an average SSEP amplitude reduction of 73% ± 12% recorded at the signals' nadir. Immediate arm repositioning resulted in recovery of signals and complete return to baseline parameters in 14.3 ± 9.2 minutes. There was no difference in age (40.4 ± 9.4 years vs. 44.5 ± 13.4 years; P = .31) or body mass index (27.3 ± 3.7 kg/m² vs. 26.9 ± 6.1 kg/m² ; P = .79) between cases with and without SSEP change. Operative time was shorter for patients with significant SSEP change (131.6 ± 14.7 minutes vs. 146.5 ± 46.7 minutes; P = .048). There were no postoperative positional brachial plexus injuries.

CONCLUSIONS

SSEP is a novel, safe, and reliable tool in detection of position-related brachial plexus neuropathy. Intraoperative monitoring using SSEP can play a vital role in early recognition and prevention of injury during robotic transaxillary thyroid and parathyroid surgery.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:2663-2668, 2019.

Intraoperative Neurophysiological Monitoring for Craniovertebral Junction Surgery

Craniovertebral junction (CVJ) surgery encompasses a wide spectrum of neurosurgical procedures ranging from transoral approaches for CVJ bone anomalies to surgery for intramedullary tumours. Intraoperative neurophysiological monitoring (IONM) has been increasingly used in recent years because of its ability to prevent neurological complications during surgery. In CVJ surgery the risk of neurological injuries is related first to the positioning of the patient and then to the surgical procedure. Application of IONM during the positioning of the patient permits fast recognition of impending causes of neurological injury. During surgery, continuous IONM permits real-time assessment of the functional integrity of the spinal tracts and provides useful feedback during surgical manoeuvres. The applications of IONM are mainly related to intradural procedures, but wider application of these techniques during surgery for CVJ instability and degenerative disorders has recently been described, leading also to better understanding of the pathophysiology of spinal cord injuries. In this paper we review and discuss the principal IONM techniques used during surgery around the CVJ.

Spinal cord monitoring

Spinal cord surgery carries the risk of spinal cord or nerve root injury. Neurophysiologic monitoring decreases risk of injury by continuous assessment of spinal cord and nerve root function throughout surgery. Techniques include somatosensory evoked potentials (SEPs), transcranial electrical motor evoked potentials (MEPs), and electromyography (EMG). Baseline neurophysiologic data are obtained prior to incision. Real-time signal changes are identified in time to correct compromised neural function. Such monitoring improves postoperative neurologic functional outcomes. Challenges in neurophysiologic intraoperative monitoring (NIOM) include effects of anesthetics, neuromuscular blockade, hypotension, hypothermia, and preexisting neurological conditions, e.g., neuropathy or myelopathy. Technical factors causing poor quality data must be overcome in the electrically noisy operating room environment. Experienced monitoring teams understand tactics to obtain quality recordings and consider confounding variables before raising alarms when change occurs. Once an alert is raised, surgeons and anesthesiologists respond with a variety of actions, such as raising blood pressure or adjusting retractors. In experienced hands, NIOM significantly reduces postoperative neurological deficits, e.g., 60% reduction in risk of paraplegia and paraparesis. A technologist in the operating room sets up the NIOM procedure. An experienced clinical neurophysiologist supervises the case, either in the operating room or remotely on-line continuously in real time.

Loss of intraoperative neurological monitoring signals during flexed prone positioning on a hinged open frame during surgery for kyphoscoliosis correction: case report

Various complications of prone positioning in spine surgery have been described in the literature. Patients in the prone position for extended periods are subject to neurological deficits and/or loss of intraoperative signals due to compression neuropathies, but positioning-related spinal deficits are rare in the thoracolumbar deformity population. The authors present a case of severe kyphoscoliotic deformity with critical thoracolumbar stenosis in which, during the use of a hinged open frame in the prone position, complete loss of intraoperative neural monitoring signals occurred while the frame was flexed into kyphosis to facilitate exposure and instrumentation placement. When the frame was reset to a neutral position, evoked potentials returned to baseline and the operation proceeded without complications. This case represents, to the authors’ knowledge, the first report of loss of evoked potentials due to an alteration of prone positioning on a hinged open frame. When positioning patients in such a manner, careful attention should be directed to intraoperative signals in patients with critical stenosis and kyphotic deformity.

Risk factors for positioning-related somatosensory evoked potential changes in 3946 spinal surgeries

The goal of this study was to evaluate the risk factors associated with positioning-related SSEP changes (PRSC). The study investigated the association between 18 plausible risk factors and the occurrence of intraoperative PRSC. Risk factors investigated included demographic variables, comorbidities, and procedure related variables. All patients were treated by the University of Pittsburgh Medical Center from 2010 to 2012. We used univariate and multivariate statistical methods. 69 out of the 3946 (1.75%) spinal surgeries resulted in PRSC changes. The risk of PRSC was increased for women (p < 0.001), patients older than 65 years of age (p = 0.01), higher BMI (p < 0.001) patients, smokers (p < 0.001), and patients with hypertension (p < 0.001). No associations were found between PRSC and age greater than 80 years, diabetes mellitus, cardiovascular disease, and peripheral vascular disease. Three surgical situations were associated with PRSC including abnormal baselines (p < 0.001), patients in the "superman" position (p < 0.001), and patients in surgical procedures that extended over 200 min (p = 0.03). Patients with higher BMIs and who are undergoing spinal surgery longer than 200 min, with abnormal baselines, must be positioned with meticulous attention. Gender, hypertension, and smoking were also found to be risk factors from their odds ratios.

Intraoperative Neurophysiologic Monitoring for Degenerative Cervical Myelopathy

Multimodal intraoperative neurophysiologic monitoring is a reliable tool for detecting intraoperative spine injury and is recommended during surgery for degenerative cervical myopathy (DCM). Somatosensory evoked potential (SEP) can be used to monitor spine and peripheral nerve injury during positioning in surgery for DCM. Compensation technique for transcranial evoked muscle action potentials (tcMEPs) should be adopted in intraoperative monitoring during surgery for DCM. Free-running electromyography is a useful real-time monitoring add-on modality in addition to SEP and tcMEP.

Guideline Implementation: Positioning the Patient

Every surgical procedure requires positioning the patient; however, all surgical positions are associated with the potential for the patient to experience a positioning injury. The locations and types of potential injuries (eg, stretching, compression, pressure injury) depend on the position. Factors that may increase the patient's risk for an injury are the length of the procedure and risk factors inherent to the patient (eg, weight, age, frailty). AORN's updated "Guideline for positioning the patient" provides guidance on injury prevention practices for all surgical positions including supine, Trendelenburg, reverse Trendelenburg, lateral, lithotomy, prone, and sitting positions and modifications of these positions. This article focuses on the key points of the guideline covering the use of prophylactic dressings, neurophysiological monitoring, and safely positioning the patient in the supine and prone positions. Perioperative RNs should review the complete guideline for additional information and for guidance when writing and updating policies and procedures.

Brachial Plexopathy After Cervical Spine Surgery

STUDY DESIGN

Retrospective, multicenter case-series study and literature review.

OBJECTIVES

To determine the prevalence of brachial plexopathy after cervical spine surgery and to review the literature to better understand the etiology and risk factors of brachial plexopathy after cervical spine surgery.

METHODS

A retrospective case-series study of 12 903 patients at 21 different sites was performed to analyze the prevalence of several different complications, including brachial plexopathy. A literature review of the US National Library of Medicine and the National Institutes of Health (PubMed) database was conducted to identify articles pertaining to brachial plexopathy following cervical spine surgery.

RESULTS

In our total population of 12 903 patients, only 1 suffered from postoperative brachial plexopathy. The overall prevalence rate was thus 0.01%, but the prevalence rate at the site where this complication occurred was 0.07%. Previously reported risk factors for postoperative brachial plexopathy include age, anterior surgical procedures, and a diagnosis of ossification of the posterior longitudinal ligament. The condition can also be due to patient positioning during surgery, which can generally be detected via the use of intraoperative neuromonitoring.

CONCLUSIONS

Brachial plexopathy following cervical spine surgery is rare and merits further study.

Transcranial Motor Evoked Potentials during Spinal Deformity Corrections-Safety, Efficacy, Limitations, and the Role of a Checklist

Introduction

Intraoperative neuromonitoring (IONM) has become a standard of care in spinal deformity surgeries to minimize the incidence of new onset neurological deficit. Stagnara wake up test and ankle clonus test are the oldest techniques described for spinal cord monitoring, but they cannot be solely relied upon as a neuromonitoring modality. Somatosensory evoked potentials monitor only dorsal tracts and give high false positive and negative alerts. Transcranial motor evoked potentials (TcMEPs) monitor the more useful motor pathways. The purpose of our study was to report the safety, efficacy, limitations of TcMEPs in spine deformity surgeries, and the role of a checklist.

Study design

Retrospective review of all spinal deformity surgeries performed with TcMEPs from 2011 to 2015.

Materials and methods

All patients were subjected to IONM by TcMEPs during the spinal deformity surgery. Patients were included in the study only if complete operative reports and neuromonitoring data and postoperative neurological data were available for review. An alert was defined as 80% or more decrement in the motor evoked potential amplitude, or increase in threshold of 100 V or more from baseline. The systemic and surgical causes of IONM alerts and the postoperative neurological status were recorded.

Results

In total, 61 patients underwent surgery for spinal deformities with TcMEPs. The average age was 12.6 years (6–36 years) and male:female ratio was 1:1.3. Diagnoses included idiopathic scoliosis (n = 35), congenital scoliosis (n = 13), congenital kyphosis (n = 7), congenital kyphoscoliosis (n = 4), post-infectious kyphosis (n = 1), and post-traumatic kyphosis (n = 1). The average kyphosis was 72° (45°–101°) and the average scoliosis was 84° (62°–128°). There were in total 33 alerts in 22 patients (36%). The most common causes were hypotension (n = 7), drug induced (n = 5), deformity correction (n = 5), osteotomies (n = 3), tachycardia (n = 1), screw placement (n = 2), and electrodes disconnection (n = 1). Reversal of the inciting event cause resulted in complete reversal of the alert in 90% of the times. Three patients showed persistent alerts, out of whom one had a positive wake up test and woke up with neurodeficit, which recovered over few weeks, while the other patients showed persistent alerts but woke up without any deficit. Sensitivity and specificity of TcMEP in deformity correction surgery were 100 and 96.6%, respectively, in our study.

Conclusion

IONM alerts are frequent during spinal deformity surgery. In our study, more than 50% of the alerts were associated with anesthetic management. IONM with TcMEPs is a safe and effective monitoring technique and wake up test still remains a valuable tool in cases of a persistent alert.

What Is the Frequency of Intraoperative Alerts During Pediatric Spinal Deformity Surgery Using Current Neuromonitoring Methodology? A Retrospective Study of 218 Surgical Procedures

INTRODUCTION

There is variability in intraoperative neuromonitoring (IONM), anesthetic and surgical techniques for the treatment of pediatric spinal deformity. This study evaluates a series of patients treated at multiple centers utilizing transcranial motor and somatosensory evoked potentials (TcMEP and SSEP) and electromyography (EMG). The frequency of alerts and the intraoperative follow-up is reported.

METHODS

Standard patient demographics and IONM data were collected from a two-month cohort of pediatric spine deformity cases.

RESULTS

Data from 218 scoliosis patients were included from 46 facilities and 72 surgeons. Baseline upper and lower extremity TcMEP data were present in 96.7% and 93.9% patients respectively. Baseline upper and lower SSEPs were present in 99.5% and 95.4% respectively Surgical TCMEP alerts occurred in 19 (8.7%) patients during deformity correction (n = 11), placement of instrumentation (n = 5), decompression (n = 2), and closing (n = 1) with concurrent SSEP alerts occurring in five patients. Nine had TCMEP recovery, eight showed partial recovery and two did not recover. Additional alerts occurred due to: positioning (n = 16), inhalational agent change (n = 4), global physiological change (n = 4) and technical reasons (n = 2). A total of 2164 pedicle screws were tested. Of 197 (9.1%) screws that tested from 6-9 mA, 171 (65.4%) were left unchanged, 10 (51%) removed, eight (4.1%) repositioned with improved threshold, and eight (4.1%) without improvement. Of 26 screws that tested ≤ 5 milliamperes (mA), 17 (65.4%) were left unchanged, five (19.2%) removed, two (7.7%) repositioned with improved threshold, and two (7.7%) without improvement.

CONCLUSIONS

IONM provides data that causes re-evaluation in about 10% of pediatric spinal deformity cases.

Intermittent Feet Dorsiflexion as a Simple Trick to Improve Cervical Fluoroscopic Visualization

BACKGROUND

Anterior cervical surgery is routinely performed using fluoroscopy. Visualizing the lower cervical levels can be challenging, particularly in obese, muscular, and broad-shouldered patients. We found that grabbing both feet of the patient at the level of the metatarsals and cranially pushing the feet, creating dorsiflexion at the ankle joints, seems to increase the number of fluoroscopically visualized cervical levels. We aimed to measure the average change in fluoroscopically visualized levels when performing this maneuver.

METHODS

In 10 consecutive patients undergoing an anterior cervical discectomy and fusion procedure, we counted the number of fluoroscopically visualized cervical levels. Visible cervical levels in lateral fluoroscopic cervical images that were taken with and without the execution of the aforementioned maneuver were counted by 2 blinded observers.

RESULTS

Performing this maneuver added on average almost 1 vertebral body height to the fluoroscopic image. The additional number of fluoroscopically visible cervical levels was significantly higher in patients <50 years old but was not affected by sex or body mass index.

CONCLUSIONS

We propose a simple, convenient, and effective technique to increase the number of visualized cervical levels on lateral cervical fluoroscopy. This maneuver may have some advantages compared with other commonly used techniques.

Contemporaneous Evaluation of Intraoperative Ulnar and Median Nerve Somatosensory Evoked Potentials for Patient Positioning: A Review of Four Cases

Somatosensory evoked potentials (SSEPs) are a valuable tool for assessing changes in peripheral nerve pathways caused by patient positioning during spinal surgeries. These changes, when left undiagnosed, may lead to postoperative neurological sequelae. Why an upper extremity SSEP attenuates due to positioning is not necessarily clear and can be multifactorial, affecting the peripheral nerves or elements of the brachial plexus. A conduction block can occur at any point along the course of the nerve secondary to entrapment, compression, and ischemia. These mechanisms of injury may be caused by extreme body habitus, the length of the procedure, or the patient's metabolic underpinnings. The goal of neuromonitoring for positional injury is to predict and prevent both peripheral nerve and brachial plexus injuries. Using ulnar and median nerve SSEPs contemporaneously may lead to better identification of compromised structures when an SSEP change to one or both of the nerves occurs. The investigators provide four case reports where intraoperative SSEP assessment of contemporaneous ulnar and median nerves prevented postoperative upper extremity neural deficits.

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.

Clinical Decision Support and Perioperative Peripheral Nerve Injury: A Quality Improvement Project

Decision support at the point of care has been demonstrated to be an effective tool in providing a safe environment and improving patient outcomes. The operating room is typically an area where advanced technology is introduced to nurses on a regular basis. This quality improvement project focused on preventing a peripheral nerve injury, which is an example of a postoperative adverse event that is considered preventable. Injury of a peripheral nerve is the result of compression, hyperextension, flexion, or ischemia surrounding the nerve. The goals for this project were to improve the knowledge of peripheral nerve injury of the operating room nurses, design and implement a peripheral nerve injury assessment screen that could provide decision support within the operating room record, improve the nursing documentation of peripheral nerve injury interventions, and (long term) decrease the incidence of peripheral nerve injury. A decision support screen within the operating room record was designed to supplement the operating room nurse's risk assessment for peripheral nerve injury. The components of this project involved a preliminary and postproject surveys on peripheral nerve injury knowledge, an educational presentation, and a retrospective random review of nursing documentation in the operating room electronic health records. Project results demonstrated a significant increase in nursing documentation of peripheral nerve injury interventions (63%-92%) and a positive attitude toward their exposure to basic decision support (P = .046). Recommendations for future studies and establishing a standardized coding system for peripheral nerve injury identification were identified.

Exploration of the Intraoperative Motor Evoked Potential

STUDY DESIGN

Prospective study.

OBJECTIVE

The objectives of the study was to (1) seek a relation between motor evoked potential (MEP) and corresponding cervical cord function in cervical compression myelopathy (CCM) and (2) explore a high-sensitive MEP range that can predict the intraoperative monitoring change ahead in cervical spine surgery.

SUMMARY OF BACKGROUND DATA

There have been lots of controversies concerning the application of transcranial MEP in cervical spine surgery.

METHODS

We prospectively investigate 86 consecutive patients with CCM who underwent posterior laminoplasty or laminectomy from December 2012 to September 2014. The 18-point modified Japanese Orthopedic Association (mJOA) score and intraoperative MEP were used for neurological and electrophysiological assessment. Statistical correlation analysis and curve fitting were used to definite the relationship between MEP and corresponding cervical cord function. And a novel concept of high-sensitive MEP range was firstly addressed for predicting the intraoperative monitoring change ahead in CCM.

RESULTS

Our results showed that the preoperative mJOA score of lower extremity presented a significant correlation with MEP parameters in CCM, and the correlation was expressed in an exponential relationship. The monitoring change in CCM often appeared at a high-sensitive MEP range (amplitude <159 μV or latency >36.1 ms). In addition, the high-sensitive MEP ranges not only included MEP degeneration but also a larger number of MEP improvement cases.

CONCLUSION

Intraoperative MEP may imply an exponential correlation with the corresponding cervical cord function in CCM. And we first characterize a high-sensitive MEP range which may indicate high risk for the impending monitoring change during cervical cord decompression and we must watch more closely.

The cause of brachial plexopathy in robot-assisted transaxillary thyroidectomy-A neurophysiological investigation

OBJECTIVES/HYPOTHESIS

During robot-assisted transaxillary thyroidectomy, the patient's arm is maintained in an overhead flexed position for a prolonged time, which poses a risk of postoperative brachial plexopathy. The aim of the study was to identify the causes of brachial plexopathy and to assess the benefit of intraoperative neurophysiological monitoring (IONM) in preventing positional brachial plexopathy in this setting.

STUDY DESIGN

Retrospective case series.

METHODS

The computerized database of a tertiary medical center was searched for all consecutive patients who underwent robot-assisted transaxillary thyroidectomy between 2012 and 2014. Clinical, operative, and outcome parameters were collected from the medical files. Findings were compared between patients operated with and without IONM.

RESULTS

The cohort included 30 patients, 14 operated with IONM and 16 without. Three events of impending brachial plexopathy were detected in the monitored group. The monitored group had significantly better shoulder movement (P = .003), a lower rate of hypoesthesia (P = .011), less pain (P = .001) in the early postoperative period than the nonmonitored group and higher quality of life in the early postoperative period (P = .012). The monitored group was significantly younger than the nonmonitored one (P = .02) and had a significantly larger diameter of thyroid nodule than the nonmonitored group (P = .043).

CONCLUSIONS

IONM during robot-assisted transaxillary thyroidectomy may improve short-term postoperative pain and shoulder movement and longer-term quality of life.

LEVEL OF EVIDENCE

4 Laryngoscope, 126:2187-2193, 2016.

Monopolar-probe monitoring during spinal surgery with expandable prosthetic ribs

BACKGROUND

Intraoperative monitoring (IOM) has been proven to decrease the risk of neurological injury during scoliosis surgery. The vertical expandable prosthetic titanium rib (VEPTR) is a device that allows spinal growth. However, injuries to the spinal cord and brachial plexus have been reported after VEPTR implantation in 2 and 5% of patients, respectively. Simultaneous monitoring of these two structures requires the use of multiple time-consuming and complex methods that are ill-suited to the requirements of paediatric surgery, particularly when repeated VEPTR lengthening procedures are needed. We developed a monopolar stimulation method derived from Owen's monitoring technique. This method is easy to implement, requires only widely available equipment, and allows concomitant monitoring of the spinal cord and brachial plexus. The primary objective of this study was to assess the reliability of our technique for brachial plexus monitoring by comparing the stability of neurogenic mixed evoked potentials (NMEPs) at the upper and lower limbs.

HYPOTHESIS

We hypothesised that the coefficients of variation (CVs) of NMEPs were the same at the upper and lower limbs.

MATERIAL AND METHODS

Twelve VEPTR procedures performed in 6 patients between 1st January 2012 and 1st September 2014 were monitored using a monopolar stimulating probe. NMEPs were recorded simultaneously at the upper and lower limbs, at intervals of 150 s. The recording sites were the elbow over the ulnar nerve and the popliteal fossa near the sciatic nerve. Wilcoxon's test for paired data was used to compare CVs of the upper and lower limb NMEPs on the same side.

RESULTS

Mean CV of NMEP amplitude at the lower limbs was 16.34% on the right and 16.67% on the left; corresponding values for the upper limbs were 18.30 and 19.75%, respectively. Mean CVs of NMEP latencies at the lower limbs were 1.31% on the right and 1.19% on the left; corresponding values for the upper limbs were 1.96 and 1.73%. The risk of type I error for a significant difference between the upper and lower limbs was 0.5843 on the right and 0.7312 on the left for NMEP amplitudes and 0.7618 on the right and 0.4987 on the left for NMEP latencies.

CONCLUSION

Using an epidural active electrode and a sternal return electrode allows simultaneous stimulation of the cervical spinal cord and brachial plexus roots. The NMEPs thus obtained are as stable (reliable) at the upper limbs as at the lower limbs. This easy-to-implement method allows simultaneous monitoring of the upper and lower limbs. It seems well suited to VEPTR procedures.

LEVEL OF EVIDENCE

IV, retrospective single-centre non-randomised study.

Complications associated with prone positioning in elective spinal surgery

Complications associated with prone surgical positioning during elective spine surgery have the potential to cause serious patient morbidity. Although many of these complications remain uncommon, the range of possible morbidities is wide and includes multiple organ systems. Perioperative visual loss (POVL) is a well described, but uncommon complication that may occur due to ischemia to the optic nerve, retina, or cerebral cortex. Closed-angle glaucoma and amaurosis have been reported as additional etiologies for vision loss following spinal surgery. Peripheral nerve injuries, such as those caused by prolonged traction to the brachial plexus, are more commonly encountered postoperative events. Myocutaneous complications including pressure ulcers and compartment syndrome may also occur after prone positioning, albeit rarely. Other uncommon positioning complications such as tongue swelling resulting in airway compromise, femoral artery ischemia, and avascular necrosis of the femoral head have also been reported. Many of these are well-understood and largely avoidable through thoughtful attention to detail. Other complications, such as POVL, remain incompletely understood and thus more difficult to predict or prevent. Here, the current literature on the complications of prone positioning for spine surgery is reviewed to increase awareness of the spectrum of potential complications and to inform spine surgeons of strategies to minimize the risk of prone patient morbidity.

Post-operative brachial plexus neuropraxia: A less recognised complication of combined plastic and laparoscopic surgeries

This presentation is to increase awareness of the potential for brachial plexus injury during prolonged combined plastic surgery procedures. A case of brachial plexus neuropraxia in a 26-year-old obese patient following a prolonged combined plastic surgery procedure was encountered. Nerve palsy due to faulty positioning on the operating table is commonly seen over the elbow and popliteal fossa. However, injury to the brachial plexus has been a recently reported phenomenon due to the increasing number of laparoscopic and robotic procedures. Brachial plexus injury needs to be recognised as a potential complication of prolonged combined plastic surgery. Preventive measures are discussed.

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.

Use of somatosensory evoked potentials to detect and prevent impending brachial plexus injury during surgical positioning for the treatment of supratentorial pathologies

Somatosensory evoked potentials (SSEPs) are widely utilized for the intraoperative detection and prevention of nerve conduction injuries. Their use in identifying position-related injuries to the brachial plexus in patients undergoing supine craniotomies for the treatment of supratentorial pathology is not well documented. This case series describes three instances of unilateral upper extremity SSEP changes in patients positioned for supine craniotomies. In all three cases SSEP responses improved after repositioning. None of the patients exhibited new neurological deficits post-operatively. This case series highlights the importance of vigilant monitoring in the period after final positioning and demonstrates the usefulness of SSEPs as a tool to aid in the early detection and prevention of impending position-related nerve injury.

Somatosensory-evoked potential monitoring during instrumented scoliosis corrective procedures: validity revisited

BACKGROUND

Intraoperative monitoring (IOM) using somatosensory-evoked potentials (SSEPs) plays an important role in reducing iatrogenic neurologic deficits during corrective pediatric idiopathic procedures for scoliosis. However, for unknown reasons, recent reports have cited that the sensitivity of SSEPs to detect neurologic deficits has decreased, in some to be less than 50%. This current trend, which is coincident with the addition of transcranial motor-evoked potentials, is surprising given that SSEPs are robust, reproducible responses that were previously shown to have sensitivity and specificity of >90%.

PURPOSE

Our primary aim was to assess whether SSEPs alone can detect impending neurologic deficits with similar sensitivity and specificity as originally reported. Our secondary aim was to estimate the potential predictive value of adding transcranial motor-evoked potentials to SSEP monitoring in idiopathic scoliosis procedures.

DESIGN

This was a retrospective review to analyze the efficacy of SSEP monitoring in the group of pediatric instrumented scoliosis fusion cases.

PATIENT SAMPLE

We retrospectively reviewed all consecutive cases of patients who underwent idiopathic scoliosis surgery between 1999 and 2009 at Children's Hospital of Pittsburgh. We identified 477 patients who had the surgery with SSEP monitoring alone. Exclusion criteria included any patients with neuromuscular disorders or unreliable SSEP monitoring. Patients who had incomplete neurophysiology data or incomplete postoperative records were also excluded.

OUTCOME MEASURES

Major outcomes measured were clinically significant postoperative sensory or motor deficits, as well as significant intraoperative SSEP changes.

METHODS

Continuous interleaved upper- and lower-extremity SSEPs were obtained throughout the duration of all procedures. We considered a persistent 50% reduction in primary somatosensory cortical amplitude or a prolongation of response latency by >10% from baseline to be significant. Persistent changes represent significant deviation in SSEP amplitude or latency in more than two consecutive averaged trials. Patients were classified into one of four categories with respect to SSEP monitoring: true positive, false positive, true negative, and false negative. The sensitivity, specificity, positive predictive value, and negative predictive value were then calculated accordingly.

RESULTS

Our review of 477 idiopathic scoliosis surgeries monitored using SSEPs alone revealed a new deficit rate of 0.63% with no cases of permanent injury. Sensitivity = 95.0%, specificity = 99.8%, positive predictive value = 95%, negative predictive value = 99.8%. Using evidence-based epidemiologic measures, we calculated that the number needed to treat was 1,587 patients for one intervention to be performed that would have been missed by SSEP monitoring alone. In addition, the number needed to harm, which represents the increase in false positives with the addition of transcranial electrical motor-evoked potentials, was 200.

CONCLUSION

SSEP monitoring alone during idiopathic scoliosis continues to be a highly reliable method for the detection and prevention of iatrogenic injury. Our results confirm the high sensitivity and specificity of SSEP monitoring alone published in earlier literature. As such, we suggest the continued use of SSEP alone in idiopathic scoliosis surgeries. At this time we do not believe there are sufficient data to support the addition of MEP monitoring, although more studies and revised criteria for the use of MEP may provide added value for its use in the future.

Differential rates of false-positive findings in transcranial electric motor evoked potential monitoring when using inhalational anesthesia versus total intravenous anesthesia during spine surgeries

BACKGROUND CONTEXT

False-positive loss of transcranial electrical motor evoked potentials (TCe-MEPs) limits the efficacy of motor tract monitoring during spine surgery. Although total intravenous anesthesia (TIVA) is widely regarded as the optimal regimen for TCe-MEPs, inhalational anesthesia is an alternative regimen.

PURPOSE

To compare the rates of false-positive TCe-MEPs during spine surgery for patients anesthetized with TIVA and inhalation anesthesia.

STUDY DESIGN

A retrospective analysis of data collected from consecutive patients undergoing TCe-MEP monitoring during spinal surgery.

PATIENT SAMPLE

Consecutive adult patients from multiple surgical centers undergoing spine surgery inclusive of cervical or thoracic spinal levels during 2008-2009 who received TIVA or inhalation anesthesia.

OUTCOME MEASURES

The primary outcome measure was the rate of false-positive alerts using TCe-MEPS, defined as a persistent loss of 90% or greater of the amplitude of TCe-MEP in one or more muscles not attributed to technical or transient systemic factors (hypotension or hypoxia) and not associated with any postoperative neurologic deficit.

METHODS

Patients were divided into two groups according to anesthetic regimen: those anesthetized with one or more inhalational agents (n=1,303) and patients anesthetized with TIVA (n=511). The Fisher exact test and unpaired t test were used to compare group characteristics and false-positive rates. Each group was further subdivided by spinal region (cervical, thoracic, and thoracolumbar) and by presence of preoperative motor deficit. A Pearson chi-squared test was used to identify differences according to spinal region. This study was not supported by any financial sources nor do the authors have any financial relationships to disclose.

RESULTS

Patient with inhaled anesthesia showed significantly higher rates of false-positive TCe-MEP changes (15.0% vs. 3.2%) compared with the TIVA group. These differences were significant across all surgical subgroups. The inhaled group had a larger number of patients with preoperative motor deficits compared with TIVA (45.0% vs. 37.4%), a potential confounder for false-positive results. However, a significantly higher rate of false-positive TCe-MEP changes was still observed in the inhaled group (11.4% vs. 0.6% for TIVA) when analyzing only those patients without preoperative motor deficits.

CONCLUSIONS

Use of inhalation anesthesia during adult spinal surgery is associated with significantly higher rates of false-positive changes compared with TIVA during TCe-MEP monitoring. This relationship appears independent of preoperative motor status. Further study and multivariate analysis of anesthetic agents, diagnosis, and symptoms is necessary to elucidate the impact of these variables. The potential confounding effects of inhalational anesthesia on TCe-MEP monitoring should be considered when determining anesthetic regimen.

Modified robotic-assisted thyroidectomy: an initial experience with the retroauricular approach

OBJECTIVES/HYPOTHESIS

New approaches for robotic-assisted thyroidectomy, including the retroauricular approach, were recently described. We have modified the established surgical approach for retroauricular robotic thyroidectomy. Herein, we report our initial experience to identify challenges and limitations of this new surgical approach.

STUDY DESIGN

Prospective case series.

METHODS

This study was performed under institutional review board approval for patients who underwent retroauricular robotic hemithyroidectomy at an academic North American institution. The retroauricular approach was modified by using the space between the two heads of the sternocleidomastoid muscle as our working space. Additionally, selected patients underwent concomitant neck lift surgery with robotic thyroid surgery. Clinical characteristics, total operative time, blood loss, surgical outcomes, and length of hospital stay were evaluated.

RESULTS

Twelve female patients were included in this study. Mean age was 45 ± 4.43 years, and mean body mass index was 28.6 ± 2.15. Mean thyroid nodule size was 1.15 ± 0.26 cm(3). All cases were completed successfully via single retroauricular incision. There was no conversion to an open approach. Four out of 12 patients (33%) underwent additional concomitant neck lift surgery, with a mean total operative time of 156 ± 15.88 minutes. The mean operative time for the remaining eight patients who underwent the robotic approach without additional neck lift surgery was 145.4 ± 10.08 minutes. There were no cases of permanent vocal cord paralysis or permanent hypoparathyroidism. Mean blood loss was 22.4 ± 4.32 mL. Four patients (33%) were discharged home on the same day of surgery, and the remaining eight patients were discharged after an overnight stay.

CONCLUSIONS

Single-incision retroauricular robotic hemithyroidectomy can be a safe and feasible alternative to other remote access techniques. Neck lift surgery can be performed safely in a select group of patients. However, future studies are warranted to further evaluate the benefits and limitations of this novel approach.

Predictive Value of Somatosensory Evoked Potential Monitoring during Resection of Intraparenchymal and Intraventricular Tumors Using an Endoscopic Port

BACKGROUND AND PURPOSE

Intraoperative neurophysiological monitoring (IONM) using upper and lower somatosensory evoked potentials (SSEPs) is an established technique used to predict and prevent neurologic injury during intracranial tumor resections. Endoscopic port surgery (EPS) is a minimally-invasive approach to deep intraparenchymal and intraventricular brain tumors. The authors intended to evaluate the predictive value of SSEP monitoring during resection of intracranial brain tumors using a parallel endoscopic technique.

METHODS

A retrospective review was conducted of patients operated on from 2007-2010 utilizing IONM in whom endoscopic ports were used to remove either intraparenchymal or intraventricular tumors. Cases were eligible for review if an endoscopic port was used to resect an intracranial tumor and the electronic chart included all intraoperative monitoring data as well as pre- and post-operative neurologic exams.

RESULTS

139 EPS cases met criteria for inclusion. Eighty five patients (61%) had intraparenchymal and fifty four (39%) had intraventricular tumors or colloid cysts. SSEP changes were seen in eleven cases (7.9%), being irreversible in three (2.2%) and reversible in eight cases (5.8%). Seven patients (5.0%) with intraparenchymal tumors had SSEP changes which met our criterea for significant changes while there were four (2.9%) with intraventricular (p-value=0.25). Five patients suffered post operative deficits, two reversible and two irreversible SSEP changes. Only one case exhibited post operative hemiparesis with no SSEP changes. The positive predictive value of SSEP was 45.4% and the negative predictive value was 99.2%.

CONCLUSIONS

Based on the high negative and low positive predictive values, the utility of SSEP monitoring for cylindrical port resections may be limited. However, the use of SSEP monitoring can be helpful in reducing the impact of endoscopic port manipulation when the tumor is closer to the somatosensory pathway.

Efficacy of intraoperative monitoring of transcranial electrical stimulation–induced motor evoked potentials and spontaneous electromyography activity to identify acute-versus delayed-onset C-5 nerve root palsy during cervical spine surgery

Object

Deltoid muscle weakness due to C-5 nerve root injury following cervical spine surgery is an uncommon but potentially debilitating complication. Symptoms can manifest upon emergence from anesthesia or days to weeks following surgery. There is conflicting evidence regarding the efficacy of spontaneous electromyography (spEMG) monitoring in detecting evolving C-5 nerve root compromise. By contrast, transcranial electrical stimulation–induced motor evoked potential (tceMEP) monitoring has been shown to be highly sensitive and specific in identifying impending C-5 injury. In this study the authors sought to 1) determine the frequency of immediate versus delayed-onset C-5 nerve root injury following cervical spine surgery, 2) identify risk factors associated with the development of C-5 palsies, and 3) determine whether tceMEP and spEMG neuromonitoring can help to identify acutely evolving C-5 injury as well as predict delayed-onset deltoid muscle paresis.

Methods

The authors retrospectively reviewed the neuromonitoring and surgical records of all patients who had undergone cervical spine surgery involving the C-4 and/or C-5 level in the period from 2006 to 2008. Real-time tceMEP and spEMG monitoring from the deltoid muscle was performed as part of a multimodal neuromonitoring protocol during all surgeries. Charts were reviewed to identify patients who had experienced significant changes in tceMEPs and/or episodes of neurotonic spEMG activity during surgery, as well as those who had shown new-onset deltoid weakness either immediately upon emergence from the anesthesia or in a delayed fashion.

Results

Two hundred twenty-nine patients undergoing 235 cervical spine surgeries involving the C4–5 level served as the study cohort. The overall incidence of perioperative C-5 nerve root injury was 5.1%. The incidence was greatest (50%) in cases with dual corpectomies at the C-4 and C-5 spinal levels. All patients who emerged from anesthesia with deltoid weakness had significant and unresolved changes in tceMEPs during surgery, whereas only 1 had remarkable spEMG activity. Sensitivity and specificity of tceMEP monitoring for identifying acute-onset deltoid weakness were 100% and 99%, respectively. By contrast, sensitivity and specificity for spEMG were only 20% and 92%, respectively. Neither modality was effective in identifying patients who demonstrated delayed-onset deltoid weakness.

Conclusions

The risk of new-onset deltoid muscle weakness following cervical spine surgery is greatest for patients undergoing 2-level corpectomies involving C-4 and C-5. Transcranial electrical stimulation–induced MEP monitoring is a highly sensitive and specific technique for detecting C-5 radiculopathy that manifests immediately upon waking from anesthesia. While the absence of sustained spEMG activity does not rule out nerve root irritation, the presence of excessive neurotonic discharges serves both to alert the surgeon of such potentially injurious events and to prompt neuromonitoring personnel about the need for additional tceMEP testing. Delayed-onset C-5 nerve root injury cannot be predicted by intraoperative neuromonitoring via either modality.

Preventing perioperative peripheral nerve injuries

Peripheral nerve injuries are largely preventable injuries that can result from incorrect patient positioning during surgery. Patients who are diabetic, are extremely thin or obese, use tobacco, or undergo surgery lasting more than four hours are at increased risk for developing these injuries. When peripheral nerve injuries occur, patients may experience numbness, burning, or tingling and may have difficulty getting out of bed, walking, gripping objects, or raising their arms. These symptoms can interrupt activities of daily living and impede recovery. Signs and symptoms of peripheral nerve injury may appear within 24 to 48 hours of surgery or may take as long as a week to appear. Careful attention to body alignment and proper padding of bony prominences when positioning patients for surgery is necessary to prevent peripheral nerve injury. The use of a preoperative assessment tool to identify at-risk patients, collaboration between physical therapy and OR staff members regarding patient positioning, and neurophysiological monitoring can help prevent peripheral nerve injuries.

Somatosensory evoked potentials help prevent positioning-related brachial plexus injury during skull base surgery

OBJECTIVE

Evaluate the use of somatosensory evoked potentials (SSEP) monitoring to detect positioning-related brachial plexus injury during skull base surgery.

STUDY DESIGN

Prospective cohort observational study.

SETTING

University Hospital.

SUBJECTS AND METHODS

Patients undergoing skull base surgery had a focused neurologic exam of the brachial plexus performed before and after surgery. Under stable anesthesia, brachial plexus SSEP values were obtained before and after surgical positioning. Significant SSEP changes required a readjustment of arm or neck positions. SSEPs were assessed every 30 minutes. If changes were noted, position was readjusted and SSEPs were reassessed until surgical completion. Demographic data, neurologic exams, SSEP latency, and amplitude values were recorded. Persistent changes were correlated with postoperative neurologic findings.

RESULTS

Sixty-five patients, 15 to 77 years old, were studied. Six patients (9.2%) developed SSEP amplitude changes after positioning (average amplitude decrease 72.8%). One patient had a significant latency increase. The sensitivity of SSEP for detection of injury was 57%, while specificity was 94.7%. The average body mass index (BMI) of patients with normal and abnormal SSEPs was 28.7 ± 5.6 versus 29.2 ± 8.0, respectively. Average BMI of patients with postoperative symptoms regardless of SSEP findings was 33.8 ± 4.3. Two patients who had persistent SSEP changes after positioning had BMIs of 40.1 and 31.2 kg/m(2), respectively. Improvement in neurologic findings occurred in all patients after surgery.

CONCLUSIONS

This study demonstrates that upper extremity nerve stress can be detected in real time using SSEP and may be of value in protecting patients from nerve injury undergoing lateral skull base surgery.