Analysis of reasons for medical malpractice litigation due to anterior cervical discectomy and fusion

Background

Anterior cervical discectomy and fusions (ACDF) are among the most common cervical spine operations, with over 137,000 surgeries performed annually. Understanding reasons underlying malpractice pertaining to ACDF may inform physicians of practices to improve delivery of patient care and mitigate malpractice. The aim of our study was to analyze the causes and outcomes for lawsuits pertaining to ACDF.

Methods

The Westlaw Edge and Verdict Search databases were queried for malpractice claims utilizing the keywords "anterior cervical discectomy and fusion" and "ACDF". Inclusion criteria was based on relevance of case grievance(s) to ACDF. Data collected included date of case hearing, plaintiff demographics, defendant specialty, verdict ruling, location of filed claim, monetary award, and sustained injuries.

Results

Fifty cases were included in this study after excluding 1933 cases. Of the 50 cases, 34 (68%) resulted in a defendant outcome, 8 (16%) resulted in a plaintiff outcome, and 8 (16%) resulted in settlement. Plaintiff verdicts resulted in an average monetary payment of $9.70 million, while settlements resulted in an average payment of $2.06 million. Reasons for litigation were divided into 10 categories, most commonly improper postoperative management (20%), hardware failure (18%), intraoperative error (14%), off-label use of implants (14%), and insufficient informed consent (12%).

Conclusions

Malpractice claims due to ACDF are associated with higher frequencies of plaintiff verdicts and higher monetary costs compared to other spinal surgery procedures. There does not appear to be supporting evidence that spinal cord neuromonitoring is mandatory for ACDF procedures from a medicolegal standpoint.

Transcranial Motor Evoked Potentials as a Predictive Modality for Postoperative Deficit in Cervical Spine Decompression Surgery - A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic Review and Meta-analysis.

OBJECTIVE

The purpose of this study was to evaluate whether transcranial motor evoked potential (TcMEP) alarms can predict postoperative neurologic complications in patients undergoing cervical spine decompression surgery.

METHODS

A meta-analysis of the literature was performed using PubMed, Web of Science, and Embase to retrieve published reports on intraoperative TcMEP monitoring for patients undergoing cervical spine decompression surgery. The sensitivity, specificity, and diagnostic odds ratio (DOR), of overall, reversible, and irreversible TcMEP changes for predicting postoperative neurological deficit were calculated. A subgroup analysis was performed to compare anterior vs posterior approaches.

RESULTS

Nineteen studies consisting of 4608 patients were analyzed. The overall incidence of postoperative neurological deficits was 2.58% (119/4608). Overall TcMEP changes had a sensitivity of 56%, specificity of 94%, and DOR of 19.26 for predicting deficit. Reversible and irreversible changes had sensitivities of 16% and 49%, specificities of 95% and 98%, and DORs of 3.54 and 71.74, respectively. In anterior procedures, TcMEP changes had a DOR of 17.57, sensitivity of 49%, and specificity of 94%. In posterior procedures, TcMEP changes had a DOR of 21.01, sensitivity of 55%, and specificity of 94%.

CONCLUSION

TcMEP monitoring has high specificity but low sensitivity for predicting postoperative neurological deficit in cervical spine decompression surgery. Patients with new postoperative neurological deficits were 19 times more likely to have experienced intraoperative TcMEP changes than those without new deficits, with irreversible TcMEP changes indicating a much higher risk of deficit than reversible TcMEP changes.

Intraoperative Neurophysiological Monitoring for Intradural Extramedullary Spinal Tumours

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Intraoperative neurophysiological monitoring (IONM) is widely used in spinal neurosurgery, particularly for intramedullary tumours. However, its validity in intradural extramedullary (IDEM) spinal tumours is less clearly defined, this being the focus of this study.

METHODS

We compared outcomes for patients that underwent resection of IDEM tumours with and without IONM between 2010 and 2020. Primary outcomes were postoperative American Spinal Injury Association (ASIA) scores. Other factors assessed were use of intraoperative ultrasound, drain placement, postoperative complications, postoperative Eastern Cooperative Oncology Group (ECOG) score, extent of resection, length of hospital stay, discharge location and recurrence.

RESULTS

163 patients were included, 71 patients in the IONM group and 92 in the non-IONM group. No significant differences were noted in baseline demographics. For preoperative ASIA D patients, 44.0% remained ASIA D and 49.9% improved to ASIA E in the IONM group, compared to 39.7% and 30.2% respectively in the non-IONM group. For preoperative ASIA E patients, 50.3% remained ASIA E and 44.0% deteriorated to ASIA D in the IONM group, compared to 30.2% and 39.7% respectively in the non-IONM group (all other patients deteriorated further). Length of inpatient stay was significantly shorter in the IONM group (P = .043). There were no significant differences in extent of resection, postoperative complications, discharge location or tumour recurrence.

CONCLUSIONS

Research focusing on the use of IONM in IDEM tumour surgery remains scarce. Our study supports the use of IONM during surgical excision of IDEM tumours.

Application value of intraoperative electrophysiological monitoring in cerebral eloquent area glioma surgery: a retrospective cohort study

INTRODUCTION

Surgery for gliomas involving eloquent areas is a very challenging microsurgical procedure. Maximizing both the extent of resection (EOR) and preservation of neurological function have always been the focus of attention. Intraoperative neurophysiological monitoring (IONM) is widely used in this kind of surgery. The purpose of this study was to evaluate the efficacy of IONM in eloquent area glioma surgery.

METHODS

Sixty-eight glioma patients who underwent surgical treatment from 2014 to 2019 were included in this retrospective cohort study, which focused on eloquent areas. Clinical indicators and IONM data were analysed preoperatively, two weeks after surgery, and at the final follow-up. Logistic regression, Cox regression, and Kaplan‒Meier analyses were performed, and nomograms were then established for predicting prognosis. The diagnostic value of the IONM indicator was evaluated by the receiver operating characteristic (ROC) curve.

RESULTS

IONM had no effect on the postoperative outcomes, including EOR, intraoperative bleeding volume, duration of surgery, length of hospital stay, and neurological function status. However, at the three-month follow-up, the percentage of patients who had deteriorated function in the monitored group was significantly lower than that in the unmonitored group (23.3% vs. 52.6%; P < 0.05). Logistic regression analysis showed that IONM was a significant factor in long-term neurological function (OR = 0.23, 95% CI (0.07-0.70). In the survival analysis, long-term neurological deterioration indicated worsened overall survival (OS) and progression-free survival (PFS). A prognostic nomogram was established through Cox regression model analysis, which could predict the probability 3-year survival rate. The concordance index was 0.761 (95% CI 0.734-0.788). The sensitivity and specificity of IONM evoked potential (SSEP and TCeMEP) were 0.875 and 0.909, respectively. In the ROC curve analysis, the area under the curve (AUC) for the SSEP and TCeMEP curves was 0.892 (P < 0.05).

CONCLUSIONS

The application of IONM could improve long-term neurological function, which is closely related to prognosis and can be used as an independent prognostic factor. IONM is practical and widely available for predicting postoperative functional deficits in patients with eloquent area glioma.

Timing of intraoperative neurophysiological monitoring (IONM) recovery and clinical recovery after termination of pediatric spinal deformity surgery due to loss of IONM signals

BACKGROUND CONTEXT

Intraoperative neurophysiological monitoring (IONM) is used to reduce the risk of spinal cord injury during pediatric spinal deformity surgery. Significant reduction and/or loss of IONM signals without immediate recovery may lead the surgeon to acutely abort the case. The timing of when monitorable signals return remains largely unknown.

PURPOSE

The goal of this study was to investigate the correlation between IONM signal loss, clinical examination, and subsequent normalization of IONM signals after aborted pediatric spinal deformity surgery to help determine when it is safe to return to the operating room.

STUDY DESIGN/SETTING

This is a multicenter, multidisciplinary, retrospective study of pediatric patients (<18 years old) undergoing spinal deformity surgery whose surgery was aborted due to a significant reduction or loss of IONM potentials.

PATIENT SAMPLE

Sixty-six patients less than 18 years old who underwent spinal deformity surgery that was aborted due to IONM signal loss were enrolled into the study.

OUTCOME MEASURES

IONM data, operative reports, and clinical examinations were investigated to determine the relationship between IONM loss, clinical examination, recovery of IONM signals, and clinical outcome.

METHODS

Information regarding patient demographics, deformity type, clinical history, neurologic and ambulation status, operative details, IONM information (eg, quality of loss [SSEPs, MEPs], laterality, any recovery of signals, etc.), intraoperative wake-up test, postoperative neurologic exam, postoperative imaging, and time to return to the operating were all collected. All factors were analyzed and compared with univariate and multivariate analysis using appropriate statistical analysis.

RESULTS

Sixty-six patients were enrolled with a median age of 13 years [IQR 11-14], and the most common sex was female (42/66, 63.6%). Most patients had idiopathic scoliosis (33/66, 50%). The most common causes of IONM loss were screw placement (27/66, 40.9%) followed by rod correction (19/66, 28.8%). All patients had either complete bilateral (39/66, 59.0%), partial bilateral (10/66, 15.2%) or unilateral (17/66, 25.8%) MEP loss leading to termination of the case. Overall, when patients were returned to the operating room 2 weeks postoperatively, nearly 75% (40/55) had monitorable IONM signals. Univariate analysis demonstrated that bilateral SSEP loss (p=.019), bilateral SSEP and MEP loss (p=.022) and delayed clinical neurologic recovery (p=.008) were significantly associated with having unmonitorable IONM signals at repeat surgery. Multivariate regression analysis demonstrated that delayed clinical neurologic recovery (> 72 hours) was significantly associated with unmonitorable IONM signals when returned to the operating room (p=.006). All patients ultimately made a full neurologic recovery.

CONCLUSIONS

In children whose spinal deformity surgery was aborted due to intraoperative IONM loss, there was a strong correlation between combined intraoperative SSEP/MEP loss, the magnitude of IONM loss, the timing of clinical recovery, and the time of electrophysiological IONM recovery. The highest likelihood of having a prolonged postoperative neurological deficit and undetectable IONM signals upon return to the OR occurs with bilateral complete loss of SSEPs and MEPs.

AO Spine/Praxis Clinical Practice Guidelines for the Management of Acute Spinal Cord Injury: An Introduction to a Focus Issue

STUDY DESIGN

Narrative overview and summary.

OBJECTIVES

The objective of this introductory manuscript is to provide an overview of the effort that was undertaken to establish clinical practice guidelines for a number of important topics in spinal cord injury (SCI). These topics included: 1. The role and timing of surgical decompression after acute traumatic SCI; 2. The hemodynamic management of acute traumatic SCI; and 3. The definition, diagnosis, and management of intra-operative SCI. Here, we introduce the rationale for the guidelines, the methodology utilized, and summarize how the topics are addressed within various manuscripts of this Focus Issue.

METHODS

The key clinical questions were defined using the PICO format for treatment reviews (patient; intervention; comparison; outcomes) or PPO format (patient, prognostic factor, outcomes) for risk factor review. Multi-disciplinary, international guideline development groups (GDGs) were established to evaluate and collate the available evidence in a rigorous, systematic manner, followed by a review of systematically obtained evidence within the framework of the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) criteria and application of the Evidence to Decision process. Consensus meetings, using a modified Delphi approach, were held with the multidisciplinary, international GDGs using online video-conferencing technology and anonymous voting to develop the final recommendations for each of the topics addressed. All systematic review protocols followed PRISMA standards and were registered on PROSPERO; all potential conflicts were vetted in an open and transparent manner. The funders (AO Spine and Praxis Spinal Cord Institute) had no influence over editorial content or the guidelines process).

RESULTS

Updated guidelines were established for the timing of surgical decompression after acute SCI, with surgical decompression within 24 hours of injury now "recommended" as a treatment option. Updated guidelines were also established for hemodynamic management, with an expanded target range for mean arterial pressure (MAP) of 75-80 to 90-95 mmHg for between 3 to 7 days post-injury now "suggested" as a treatment option. The available literature mandated scoping and systematic reviews on the topic of intra-operative SCI, and this resulted in manuscripts to address the definition, frequency, and risk factors, to define the role of intra-operative neuromonitoring, and to suggest an evidence-based care pathway for management.

CONCLUSION

A rigorous process following GRADE standards was undertaken to review the available evidence and establish guideline recommendations around the role and timing of surgery in acute SCI, optimal hemodynamic management of acute SCI and the prevention, diagnosis and management of intraoperative SCI. This effort also identified key knowledge gaps and future directions for study, which will serve to refine these recommendations in the future.

Analysis of Intraoperative Motor Evoked Potential Changes and Surgical Interventions in 513 Pediatric Spine Surgeries

PURPOSE

(1) To determine probabilities of immediate postoperative new motor deficits after no, reversible, and irreversible motor evoked potentials (MEP) deteriorations and (2) to calculate the same outcome considering whether MEP deteriorations were followed by surgical interventions in the absence of confounding factors.

METHODS

We analyzed MEPs from 513 surgeries. Four-limb MEPs were evoked by transcranial electrical stimulation. Baseline recordings were obtained before skin incision and updated before instrumentation. Motor evoked potentials deteriorations were considered significant whenever they showed a persistent, reversible, or irreversible amplitude decrease of >80% of the baseline values.

RESULTS

Nine patients showed postoperative new motor deficits. Probabilities of postoperative new motor deficits were null, 2.8%, and 36.8% with no, reversible, and irreversible MEP deteriorations, respectively. The risk of immediate postoperative new motor deficits was significantly lower ( P = 0.0002) in reversible MEP compared with irreversible MEP deteriorations. In patients showing reversible/irreversible MEP deteriorations in the absence of confounding factors, surgical interventions compared with nonsurgical interventions significantly decreased the risk of immediate postoperative new motor deficits ( P = 0.0216).

CONCLUSIONS

This study shows that probabilities of immediate postoperative new motor deficits increase with the severity of intraoperative MEP changes. In addition, our results support the value of surgical interventions triggered by MEP deteriorations to reduce postoperative adverse motor outcomes.

Intraoperative Neurophysiologic Monitoring and Mapping During Surgery on Intramedullary Spinal Cord Tumors in Children and Adolescents

SUMMARY

Surgical resection of intramedullary spinal cord tumors carries significant risks of neurologic deficits, especially in cases of infiltrative tumors. In pediatric patients, this type of surgery may be associated with a high risk of poor neurologic outcome. Intraoperative neurophysiologic monitoring has been adopted as part of the clinical routine by many centers as a useful adjunct for intraoperative assessment of neurologic integrity. To what extent intraoperative neurophysiologic mapping strategies may further support intraoperative decision-making is still a matter of debate. Here, we report on a small cohort of five pediatric patients in whom mapping with the double-train paradigm was used to identify the dorsal column and corticospinal tract and to guide the surgical resection. We also discuss the possible benefits and challenges regarding the available literature.

Multimodal Intraoperative Neurophysiological Monitoring in Intramedullary Spinal Cord Tumors: A 10-Year Single Center Experience

OBJECTIVE

The study aimed at evaluating the efficacy and the ability of D-wave monitoring combined with somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) to predict functional outcomes in intramedullary spinal cord tumor (IMSCT) surgery.

METHODS

Between December 2011 and December 2020, all patients harboring IMSCT who underwent surgery at our institution were prospectively collected in a surgical spinal registry and retrospectively analyzed. Patient charts and surgical and histological reports were analyzed. The multimodal IONM included SSEPs, MEPs, and-whenever possible-D-waves. All patients were evaluated using the modified McCormick and Frankel grade at admission and 3, 6, and 12 months of follow-up.

RESULTS

Sixty-four patients were enrolled in the study. SSEP and MEP monitoring was performed in all patients. The D-wave was not recordable in seven patients (11%). Significant IONM changes (at least one evoked potential modality) were registered in 26 (41%) of the 64 patients. In five cases (8%) where the SSEPs and MEPs lost and the D-wave permanently dropped by about 50%, patients experienced a permanent deterioration of their neurological status. Multimodal IONM (SSEP, MEP, and D-wave neuromonitoring) significantly predicted postoperative deficits (p = 0.0001), with a sensitivity of 100.00% and a specificity of 95.65%. However, D-waves demonstrated significantly higher sensitivity (100%) than MEPs (62.5%) and SSEPs (71.42%) alone. These tests' specificities were 85.10%, 13.89%, and 17.39%, respectively. Comparing the area under ROC curves (AUCs) of these evoked potentials in 53 patients (where all three modalities of IONM were registered) using the pairwise t-test, D-wave monitoring appeared to have higher accuracy and ability to predict postoperative deficits with strong statistical significance compared with MEP and SSEP alone (0.992 vs. 0.798 vs. 0.542; p = 0.018 and p < 0.001).

CONCLUSION

The use of multimodal IONM showed a statistically significant greater ability to predict postoperative deficits compared with SSEP, MEP, and D-wave monitoring alone. D-wave recording significantly increased the accuracy and clinical value of neurophysiological monitoring in IMSCT tumor resection.

Utility of transcranial motor-evoked potential changes in predicting postoperative deficit in lumbar decompression and fusion surgery: a systematic review and meta-analysis

PURPOSE

The primary aim of this study was to evaluate whether TcMEP alarms can predict the occurrence of postoperative neurological deficit in patients undergoing lumbar spine surgery. The secondary aim was to determine whether the various types of TcMEP alarms including transient and persistent changes portend varying degrees of injury risk.

METHODS

This was a systematic review and meta-analysis of the literature from PubMed, Web of Science, and Embase regarding outcomes of transcranial motor-evoked potential (TcMEP) monitoring during lumbar decompression and fusion surgery. The sensitivity, specificity, and diagnostic odds ratio (DOR) of TcMEP alarms for predicting postoperative deficit were calculated and presented with forest plots and a summary receiver operating characteristic curve.

RESULTS

Eight studies were included, consisting of 4923 patients. The incidence of postoperative neurological deficit was 0.73% (36/4923). The incidence of deficits in patients with significant TcMEP changes was 11.79% (27/229), while the incidence in those without changes was 0.19% (9/4694). All TcMEP alarms had a pooled sensitivity and specificity of 63 and 95% with a DOR of 34.92 (95% CI 7.95-153.42). Transient and persistent changes had sensitivities of 29% and 47%, specificities of 96% and 98%, and DORs of 8.04 and 66.06, respectively.

CONCLUSION

TcMEP monitoring has high specificity but low sensitivity for predicting postoperative neurological deficit in lumbar decompression and fusion surgery. Patients who awoke with new postoperative deficits were 35 times more likely to have experienced TcMEP changes intraoperatively, with persistent changes indicating higher risk of deficit than transient changes.

LEVEL OF EVIDENCE II

Diagnostic Systematic Review.

A Longer Duration of Myelopathy Symptoms is Associated With the Lack of Intraoperative Motor Evoked Potential Improvement During Decompressive Cervical Myelopathy Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

We aim to investigate the relationship between the intraoperative motor evoked potential (MEP) signal changes during surgical treatment of cervical myelopathy with postoperative functional outcomes and determine what factors correlate with MEP signal changes.

SUMMARY OF BACKGROUND DATA

Intraoperative neurophysiologic monitoring with MEP for cervical cord decompression can potentially predict postoperative neurological complications.

MATERIALS AND METHODS

We prospectively collected data from 114 consecutive cervical compressive myelopathy patients who underwent decompressive cervical spine surgery. Functional outcomes were measured preoperatively and postoperatively at the 6-month mark, using the modified Japanese Orthopedic Association score.

RESULTS

Among the 114 patients, 87 patients showed significant MEP improvement, 1 patient with MEP degeneration, 3 patients with no change in MEP, and 23 patients with MEP change, but which eventually returned to baseline. Univariate analysis showed that patients with MEP improvement had similar 6-month functional and Japanese Orthopedic Association scores compared with patients who did not have MEP improvement. Critically, a longer duration of symptoms was shown to have a statistically significant relationship with patients who did not have MEP improvement on univariate analysis (49.2 wk in patients with no MEP improvement compared with 34.59 wk in patients with MEP improvement, P = 0.03) but this did not translate to differences in functional outcomes. There was also no statistically significant association between the functional outcome scores and demographics, surgical, or radiologic factors.

CONCLUSIONS

Our study shows that the duration of symptoms is not attributed to lower functional outcomes but is associated with a lack of MEP improvement.

LEVEL OF EVIDENCE

Level III.

Effect of Sugammadex During Transcranial Electrical Motor Evoked Potentials Monitoring in Spinal Surgery: A Randomized Controlled Trial

INTRODUCTION

Neuromuscular blockade suppresses transcranial electrical motor evoked potential (TceMEP) amplitude and is usually avoided during TceMEP monitoring. In this randomized controlled trial, we investigated whether rocuronium-induced suppression of TceMEP amplitude could be reversed by sugammadex in patients undergoing spine surgery.

METHODS

Seventy-six patients undergoing spinal surgery were randomly allocated into sugammadex and control groups. In the sugammadex group, a rocuronium infusion was titrated to maintain moderate neuromuscular blockade (2 twitches on train-of-four) until dural opening when the rocuronium infusion was discontinued and 2 mg/kg sugammadex administered. In the control group, no neuromuscular blockade was administered after induction of anesthesia. The primary outcome was a comparison between sugammadex and control groups of mean TceMEP amplitudes in the abductor pollicis brevis muscles of both upper extremities 5 minutes after dural. Secondary outcomes included TceMEP amplitudes at 10, 20, 30, and 60 minutes after dural opening.

RESULTS

Sixty-six patients were included in the analysis. TceMEP amplitudes were significantly greater in the sugammadex group (629 μV, interquartile range: 987 μV) than in the control group (502 μV, interquartile range: 577 μV; P =0.033) at 5 minutes after dural opening. TceMEP amplitudes were also greater in the sugammadex group at 10 minutes ( P =0.0010), 20 minutes ( P =0.003), 30 minutes ( P =0.001), and 60 minutes ( P =0.003) after dural opening.

CONCLUSIONS

Moderate neuromuscular blockade induced by continuous infusion of rocuronium was effectively reversed by sugammadex. This suggests that sugammadex could be used to enhance TceMEP waveform monitoring during spine surgery requiring muscle relaxation.

Efficacy of Intraoperative Neuromonitoring during the Treatment of Cervical Myelopathy

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

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

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

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

Functional Outcome in Spinal Meningioma Surgery and Use of Intraoperative Neurophysiological Monitoring

Data on intraoperative neurophysiological monitoring (IOM) during spinal meningioma (SM) surgery are scarce. The aim of this study was to assess the role of IOM and its impact on post-operative functional outcome. Eighty-six consecutive surgically treated SM patients were included. We assessed pre and post-operative Modified McCormick Scale (mMCS), radiological and histopathological data and IOM findings. Degree of cord compression was associated with preoperative mMCS and existence of motor or sensory deficits (p < 0.001). IOM was used in 51 (59.3%) patients (IOM-group). Median pre and post-operative mMCS was II and I, respectively (p < 0.001). Fifty-seven (66.3%) patients showed an improvement of at least one grade in the mMCS one year after surgery. In the IOM group, only one patient had worsened neurological status, and this was correctly predicted by alterations in evoked potentials. Analysis of both groups found no significantly better neurological outcome in the IOM group, but IOM led to changes in surgical strategy in complex cases. Resection of SM is safe and leads to improved neurological outcome in most cases. Both complication and tumor recurrence rates were low. We recommend the use of IOM in surgically challenging cases, such as completely ossified or large ventrolateral SM.

Application of electrophysiological measures in degenerative cervical myelopathy

Degenerative cervical myelopathy (DCM) is one of the leading causes of progressive spinal cord dysfunction in the elderly. Early diagnosis and treatment of DCM are essential to avoid permanent disability. The pathophysiology of DCM includes chronic ischemia, destruction of the blood–spinal cord barrier, demyelination, and neuronal apoptosis. Electrophysiological studies including electromyography (EMG), nerve conduction study (NCS), motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs) are useful in detecting the presymptomatic pathological changes of the spinal cord, and thus supplementing the early clinical and radiographic examinations in the management of DCM. Preoperatively, they are helpful in detecting DCM and ruling out other diseases, assessing the spinal cord compression level and severity, predicting short- and long-term prognosis, and thus deciding the treatment methods. Intra- and postoperatively, they are also useful in monitoring neurological function change during surgeries and disease progression during follow-up rehabilitation. Here, we reviewed articles from 1979 to 2021, and tried to provide a comprehensive, evidence-based review of electrophysiological examinations in DCM. With this review, we aim to equip spinal surgeons with the basic knowledge to diagnosis and treat DCM using ancillary electrophysiological tests.

Intraoperative Transcranial Electrical Motor Evoked Potential (TceMEP) as a Therapeutic Tool in Spine Surgery: A Case Series Report

We report two cases of unilateral loss of TceMEP secondary to spinal instrumentation errors and the subsequent recovery of TceMEP responses following prompt intervention. During the period of TceMEP loss, there were no concomitant SSEP changes beyond the threshold criteria. Postoperative physical examination revealed normal strength and motion in the affected extremities in both patients. These cases illustrate that in addition to being a reliable intraoperative diagnostic tool, TceMEP monitoring displays therapeutic usefulness in appraising corrective actions to the existential risk of neurological injuries.

Effect of intraoperative muscle relaxation reversal on the success rate of motor-evoked potential recording in patients undergoing spinal surgery: study protocol for a randomised controlled trial

INTRODUCTION

Transcranial motor-evoked potentials (TceMEPs) is conventionally performed without neuromuscular blockade (NMB) because of its potential interference with neuromuscular junction and signal interpretation. Sugammadex is the first highly selective antagonist that binds to rocuronium and can rapidly and effectively reverse NMB. This study aims to evaluate the success rate of intraoperative muscle relax reversal by sugammadex on intraoperative TceMEP recording.

METHODS AND ANALYSIS

We will conduct a single-centre randomised controlled study. In total, 162 patients undergoing thoracic or lumbar spinal surgery will be randomly divided into the sugammadex group or control group at a ratio of 1:1. Total intravenous anaesthesia by propofol and remifentanil will be performed in both groups. In the sugammadex group, patients will receive continuous infusion of rocuronium to produce a blockade maintained for at least two twitches in train-of-four, rocuronium infusion will be discontinued and 2 mg/kg sugammadex will be given while performing TceMEPs monitoring. In the control group, rocuronium infusion will be discontinued and the same volume of saline will be infused while performing TceMEPs monitoring. The primary aim of this study is to evaluate the success rate of TceMEPs recording between two groups.

ETHICS AND DISSEMINATION

The approval for the study was certificated by the Ethical Committee of Beijing Tiantan Hospital, Capital Medical University on, 16 July 2021 (KY2021-082-02). The study was registered on clincaltrials.gov on 25 October 2020. Our study might guide neuromuscular blockade plans in TceMEPs monitoring undergoing spinal surgery. The findings of the study will be published in peer-reviewed journals and will be presented at national or international conference.

TRIAL REGISTRATION NUMBER

NCT04608682.

The effect of hydroxyapatite on titanium pedicle screw resistance: an electrical model

BACKGROUND CONTEXT

Intraoperative detection of a pedicle wall breach implicitly reduces surgical risk, but the reliability of intraoperative neuromonitoring has been contested. Hydroxyapatite (HA) has been promulgated to increase pedicle screw resistance and negatively influence the accuracy of electromyography.

PURPOSE

The primary purpose of this experiment is to evaluate the effect of HA on pedicle screw electrical resistance using a controlled laboratory model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Stimulation of pedicle screws was performed in normal saline (0.9% NaCl). The experimental group included 8 HA coated (HAC) pedicle screws and matched manufacturer control pedicle screws without HAC (Ti6Al4V). All screws were stimulated at 5, 10-, 15-, 20-, and 25-mm submersion depths. Circuit current return was recorded, and pedicle screw electrical resistance was calculated according to Ohm's Law. Data were assessed for normality and variance. Mann-Whitney U and Kruskal-Wallis tests compared groups with Bonferroni correction for multiple testing. Effect size is reported with 95% confidence intervals (95CI). p values <.05 were considered significant.

RESULTS

Current return was detected for all screws (N=24) following subclinical 8.5 µA stimulation at 5, 10-, 15-, 20-, and 25-mm submersion depths (N=144). The effect estimate of HA on pedicle screw electrical resistance is -0.07 (-0.17 to 0.01 95CI). The estimated effect of HA on pedicle screw electrical resistance did not differ across manufacturers. Electrical resistance values were inversely related to submersion depth. Electrical resistance values were lower in the experimental group at 10 mm (p=.04), 15 mm (p=.04), and 25 mm (p=.02) submersion depths. The HA effect ranged from -0.03 to -0.08 as submersion depth varied.

CONCLUSIONS

We found no evidence that HA increased pedicle screw electrical resistance in a matched manufacturer control laboratory model. Electrical stimulation of pedicle screws may be reliable for pedicle breach detection in the presence of HA. Future research should investigate if laboratory findings translate to clinical practice and confirm that electrical stimulation of pedicle screws is a reliable method to detect pedicle breach in the presence of HA.

Prevention of Neurological Deficit With Intraoperative Neuromonitoring During Anterior Lumbar Interbody Fusion

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

While intraoperative neuromonitoring (IONM) has been increasingly used in spine surgery to have a real-time evaluation of the neurological injury, we aim here to assess its utility during anterior lumbar interbody fusion (ALIF) and its association with postoperative neurological deficit.

SUMMARY OF BACKGROUND DATA

ALIF is a beneficial surgical approach for patients with degenerative disease of the lower lumbar spine who would benefit from increased lordosis and restoration of neuroforaminal height. One risk of ALIF is iatrogenic nerve root injury. IONM may be useful in preventing this injury.

MATERIALS AND METHODS

We performed a retrospective cohort study of 111 consecutive patients who underwent ALIF at a tertiary care academic center by 6 spine surgeons. We aimed to describe the association between IONM, postoperative weakness, and factors that predispose our center to using IONM.

RESULTS

The 111 patients had a median age of 62 years [interquartile range (IQR): 53-69 y]. Neuromonitoring was used in 67 patients (60.3%) and not used in 44 patients. Seven neuromonitoring patients had IONM changes during the surgery. Three of these patients' surgeries featured intraoperative adjustments to reduce iatrogenic neural injury. The IONM cohort underwent significantly more complex procedures [5 levels (IQR: 3-7) vs. 2 levels (IQR: 2-5), P=0.001]. There was no difference in rates of new or worsened postoperative weakness (IONM: 20.6%, non-IONM: 20.5%).

CONCLUSIONS

We demonstrate evidence of the potential benefits of IONM for patients undergoing ALIF. Intraoperative changes in neuromonitoring signals resulted in surgical adjustments that likely prevented neurological deficits postoperatively. IONM was protective so that more complex surgeries did not have a higher rate of postoperative weakness.

Do Intraoperative Neurophysiological Changes During Decompressive Surgery for Cervical Myeloradiculopathy Affect Functional Outcome? A Prospective Study

STUDY DESIGN

Prospective cohort.

OBJECTIVE

To investigate whether intraoperative neuromonitoring (IONM) positive changes affect functional outcome after surgical intervention for myeloradiculopathy secondary to cervical compressive pathology (cervical compressive myelopathy).

METHODS

Twenty-eight patients who underwent cervical spine surgery with IONM for compressive myeloradiculopathy were enrolled. During surgery motor-evoked potential (MEP) and somatosensory evoked potential (SSEP) at baseline and before and after decompression were documented. A decrease in latency >10% or an increase in amplitude >50% was regarded as a "positive changes." Patients were divided into subgroups based on IONM changes: group A (those with positive changes) and group B (those with no change or deterioration). Nurick grade and modified Japanese Orthopaedic Association (mJOA) score were evaluated before and after surgery.

RESULTS

Nine patients (32.1%) showed improvement in MEP. The mean preoperative Nurick grade and mJOA score of group A and B were (2.55 ± 0.83 and 11.11 ± 1.65) and (2.47 ± 0.7 and 11.32 ± 1.24), respectively. The mean postoperative Nurick grade of groups A and B at 6 months was 1.55 ± 0.74 and 1.63 ± 0.46, respectively, and this difference was not significant. The mean postoperative mJOA score of groups A and B at 6 months was 14.3 ± 1.03 and 12.9 ± 0.98, respectively, and this difference was statistically significant (P = .011). Spearman correlation coefficient showed significant positive correlation between the IONM change and the mJOA score at 6 months postoperatively (r = 0.47; P = .01).

CONCLUSION

Our study shows that impact of positive changes in MEP during IONM reflect in functional improvement at 6 months postoperatively in cervical compressive myelopathy patients.

Prediction of Discharge Status and Readmissions after Resection of Intradural Spinal Tumors

Objective

Intradural spinal tumors are uncommon and while associations between clinical characteristics and surgical outcomes have been explored, there remains a paucity of literature unifying diverse predictors into an integrated risk model. To predict postresection outcomes for patients with spinal tumors.

Methods

IBM MarketScan Claims Database was queried for adult patients receiving surgery for intradural tumors between 2007 and 2016. Primary outcomes-of-interest were nonhome discharge and 90-day postdischarge readmissions. Secondary outcomes included hospitalization duration and postoperative complications. Risk modeling was developed using a regularized logistic regression framework (LASSO, least absolute shrinkage and selection operator) and validated in a withheld subset.

Results

A total of 5,060 adult patients were included. Most surgeries utilized a posterior approach (n=5,023, 99.3%) and tumors were most commonly found in the thoracic region (n=1,941, 38.4%), followed by the lumbar (n=1,781, 35.2%) and cervical (n=1,294, 25.6%) regions. Compared to models using only tumor-specific or patient-specific features, our integrated models demonstrated better discrimination (area under the curve [AUC] [nonhome discharge] = 0.786; AUC [90-day readmissions] = 0.693) and accuracy (Brier score [nonhome discharge] = 0.155; Brier score [90-day readmissions] = 0.093). Compared to those predicted to be lowest risk, patients predicted to be highest-risk for nonhome discharge required continued care 16.3 times more frequently (64.5% vs. 3.9%). Similarly, patients predicted to be at highest risk for postdischarge readmissions were readmitted 7.3 times as often as those predicted to be at lowest risk (32.6% vs. 4.4%).

Conclusion

Using a diverse set of clinical characteristics spanning tumor-, patient-, and hospitalization-derived data, we developed and validated risk models integrating diverse clinical data for predicting nonhome discharge and postdischarge readmissions.

To Use or Not Use Intraoperative Neuromonitoring: Utilization of Neuromonitoring During Spine Surgeries and Associated Conflicts of Interest, a Cross-Sectional Survey Study

There are no universal guidelines that dictate the indications for the use of intraoperative neuromonitoring (IONM) in spine surgery resulting in its variable use. The choice to use IONM has been both cited in malpractice lawsuits and insurance claims, but no data exist regarding surgeons' rationale for making this choice. The goal of this study was to assess (1) the use of certain IONM modalities during common spine surgeries, (2) surgeons' rationale for use of IONM, and (3) IONM practices and potential conflicts of interest associated with its use.

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.

Monitoring spinal surgery for extramedullary tumors and fractures

Meningiomas are the most common intradural extramedullary tumors, followed by nerve sheath tumors that can also grow extradurally. Metastases are the most frequent extradural tumors and most commonly affect the thoracic vertebrae. Spinal fractures with column dislocation and/or instability require surgical fixation. Spine surgery for an extramedullary tumor or fracture usually involves decompression of neural elements and instrumentation for stabilization. These procedures risk spinal cord and nerve root injury. The incidence of nerve root deficits after resection of nerve sheath tumors is particularly high since the tumor grows from the rootlets. Intraoperative neurophysiologic monitoring and mapping techniques have been introduced to prevent iatrogenic neurologic deficits. These include motor and sensory evoked potentials, electromyography, compound muscle action potentials, and the bulbocavernosus reflex. The combination of techniques chosen for a particular procedure depends on the surgical level and the character of the lesion.

Monitoring scoliosis and other spinal deformity surgeries

Surgery to correct a spinal deformity incurs a risk of injury to the spinal cord and roots. Injuries include postoperative paraplegia. Surgery for cervical myelopathy also incurs risk for postoperative motor deficits, as well as nerve injury most commonly at the C5 root. Risks can be mitigated by monitoring the nervous system during surgery. Ideally, monitoring detects an impending injury in time to intervene and correct the impairment before it becomes permanent. Monitoring includes several modalities of testing. Somatosensory evoked potentials measure axonal conduction in the spinal cord posterior columns. This can be checked almost continuously during surgery. Motor evoked potentials measure conduction along the lateral corticospinal tracts. Because motor pathway stimulation often produces a patient movement on the table, these often are tested periodically rather than continuously. Electromyography observes for spontaneous discharges accompanying injuries, and is useful to assess misplacement of pedicle screws. Literature demonstrates the usefulness of these techniques, their association with reducing motor adverse outcomes, and the relative value of the techniques. Neurophysiologic monitoring for scoliosis, kyphosis, and cervical myelopathy surgery are addressed, along with background information about those conditions.

Mapping and monitoring of tethered cord and cauda equina surgeries

Surgery involving the cauda equina and tethered cord can be associated with significant functional disability including pain, motor and sensory deficits, as well as bladder, bowel, and sexual dysfunction. Neurophysiologic intraoperative monitoring and mapping during these surgeries using a variety of techniques and applications contributes to lessen the risk of permanent injury. This chapter reviews the anatomy of the pelvic floor, describes the techniques involved in monitoring and mapping this area, and describes the limitations of neurophysiology applications. Additionally, this chapter details mapping and monitoring techniques as they apply to tethered cord surgical release in both children and adults with review of outcome studies, and describes complications which can arise from tethered cord repair and injury to the cauda equina despite appropriate neurophysiologic intraoperative involvement.

Predictive Value of Intraoperative Neuromonitoring in Brainstem Cavernous Malformation Surgery

OBJECTIVE

To evaluate the predictive value of intraoperative neuromonitoring (IONM) in brainstem cavernous malformation (BSCM) surgery.

METHODS

Surgically treated patients with BSCM were included. All patients received IONM consisting of motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SSEPs). Neurologic examination was conducted preoperatively and at discharge and follow-up >3 months after BSCM removal. Demographic, radiographic, and clinical features were assessed. Study end points were new motor or somatosensory deficits and functional disability.

RESULTS

A total of 62 patients were included. MEP decrease was associated with new motor deficits at discharge (P = 0.022), and SSEP decrease was associated with new somatosensory deficits at discharge (P < 0.001) and follow-up (P < 0.001). Sensitivity and specificity values for MEPs (discharge: 31% and 93%; follow-up: 33% and 91%) and SSEPs (discharge: 82% and 80%; follow-up: 85% and 79%) were calculated, respectively. Receiver operating characteristic analyses with area under the curve (AUC) metrics revealed acceptable performance of MEPs (AUC, 0.75; P = 0.022) and SSEPs (AUC, 0.72; P = 0.004) in predicting early deficits. Intraoperative decrease of MEPs (P = 0.047) and SSEPs (P = 0.017) was associated with early functional disability. Surgery-related subdural air accumulation impaired IONM reliability in predicting early (P = 0.048) and long-term (P = 0.013) deficits.

CONCLUSIONS

Established IONM warning criteria may be valid for BSCM removal. However, surgical approaches in the sitting position significantly limit the predictive value of IONM, to some extent because of intraoperative pneumocephalus.

Magnesium Sulfate Enables Patient Immobilization during Moderate Block and Ameliorates the Pain and Analgesic Requirements in Spine Surgery, Which Can Not Be Achieved with Opioid-Only Protocol: A Randomized Double-Blind Placebo-Controlled Study

Spine surgery is painful despite the balanced techniques including intraoperative and postoperative opioids use. We investigated the effect of intraoperative magnesium sulfate (MgSO₄) on acute pain intensity, analgesic consumption and intraoperative neurophysiological monitoring (IOM) during spine surgery. Seventy-two patients were randomly allocated to two groups: the Mg group or the control group. The pain intensity was significantly alleviated in the Mg group at 24 h (3.2 ± 1.7 vs. 4.4 ± 1.8, p = 0.009) and 48 h (3.0 ± 1.2 vs. 3.8 ± 1.6, p = 0.018) after surgery compared to the control group. Total opioid consumption was reduced by 30% in the Mg group during the same period (p = 0.024 and 0.038, respectively). Patients in the Mg group required less additional doses of rocuronium (0 vs. 6 doses, p = 0.025). Adequate IOM recordings were successfully obtained for all patients, and abnormal IOM results denoting warning criteria (amplitude decrement >50%) were similar. Total intravenous anesthesia with MgSO₄ combined with opioid-based conventional pain control enables intraoperative patient immobilization without the need for additional neuromuscular blocking drugs and reduces pain intensity and analgesic requirements for 48 h after spine surgery, which is not achieved with only opioid-based protocol.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

EDITOR’S PERSPECTIVE

Intraoperative Monitoring for Cauda Equina Tumors: Surgical Outcomes and Neurophysiological Data Accrued Over 10 Years

Objective

Cauda equina tumors affect the peripheral nervous system, and the validities of triggered electromyogram (tEMG) and intraoperative neurophysiologic monitoring (IOM) are unclear. We sought to evaluate the accuracy and relevance of tEMG combined with IOM during cauda equina tumor resection.

Methods

Between 2008 and 2018, an experienced surgeon performed cauda equina tumor resections using tEMG at a single institution. A cauda equina tumor was defined as an intradural-extramedullary or intradural-extradural tumor at the level of L2 or lower. The clinical presentation, extent of resection, pathology, recurrence, postoperative neurological outcomes, and intraoperative tEMG mapping and IOM data were retrospectively analyzed.

Results

One hundred three patients who underwent intraoperative tEMG were included; 38 underwent only tEMG (tEMG-only group), and 65 underwent a combination of tEMG and multimodal IOM (MIOM group). There were no significant differences between the neurologic outcomes, extents of resection, or recurrence rates of the 2 groups. No significant therapeutic benefit was observed; however, the accuracy of intraoperative predetection improved with the combination of IOM and tEMG (accuracy: tEMG-only group, 86.8%; MIOM group, 92.3%). When the involved rootlet was resected despite the positive tEMG result, motor function worsened in 3 of 8 cases. The sensitivity and specificity of tEMG were 37.5% and 94.7%, respectively.

Conclusion

tEMG is an essential adjunctive surgical tool for deciding on and planning for rootlet resection. If the tEMG finding is negative, complete resection, involving the rootlet, may be safe. The accuracy may be further improved by using a combination of tEMG and IOM.

Quadriplegia, an Unusual Outcome After Anterior Cervical Discectomy and Fusion: A Case Report

CASE

A 68-year-old woman who underwent a C5 to C6 anterior cervical discectomy and fusion (ACDF) surgery presented with new-onset postoperative quadriplegia. During discectomy, intraoperative neurophysiological monitoring alerted of a spinal cord (SC) dysfunction. The surgery was halted, and measures to ensure adequate SC perfusion were initiated. In the next 2-week follow-up, patient's motor deficit progressively improved.

CONCLUSIONS

We report an unusual and devastating outcome of new-onset quadriplegia after an elective ACDF and highlight the relevance of intraoperative monitoring during cervical spine surgery to early recognize and treat SC impending injury.

Motor Evoked Potential Recordings During Segmented Deep Brain Stimulation-A Feasibility Study

BACKGROUND

Segmented deep brain stimulation (DBS) leads, which are capable of steering current in the direction of any 1 of 3 segments, can result in a wider therapeutic window by directing current away from unintended structures, particularly, the corticospinal tract (CST). It is unclear whether the use of motor evoked potentials (MEPs) is feasible during DBS surgery via stimulation of individual contacts/segments in order to quantify CST activation thresholds and optimal contacts/segments intraoperatively.

OBJECTIVE

To assess the feasibility of using MEP to identify CST thresholds for ring and individual segments of the DBS lead under general anesthesia.

METHODS

MEP testing was performed during pulse generator implantation under general anesthesia on subjects who underwent DBS lead implantation into the subthalamic nucleus (STN). Stimulation of each ring and segmented contacts of the directional DBS lead was performed until CST threshold was reached. Stereotactic coordinates and thresholds for each contact/segment were recorded along with the initially activated muscle group.

RESULTS

A total of 34 hemispheres were included for analysis. MEP thresholds were recorded from 268 total contacts/segments. For segmented contacts (2 and 3, respectively), the mean highest CST thresholds were 2.33 and 2.62 mA, while the mean lowest CST thresholds were 1.7 and 1.89 mA, suggesting differential thresholds in relation to CST. First dorsal interosseous and abductor pollicis brevis (34% each) were the most commonly activated muscle groups.

CONCLUSION

MEP threshold recording from segmented DBS leads is feasible. MEP recordings can identify segments with highest CST thresholds and may identify segment orientation in relation to CST.

Neurologic Complications in Monitored versus Unmonitored Image-Guidance Assisted Posterior Lumbar Instrumentation

BACKGROUND

Intraoperative neurophysiologic monitoring (IOM) has been used clinically since the 1970s and is a reliable tool for detecting impending neurologic compromise. However, there are mixed data as to whether long-term neurologic outcomes are improved with its use. We investigated whether IOM used in conjunction with image guidance produces different patient outcomes than with image guidance alone.

METHODS

We reviewed 163 consecutive cases between January 2015 and December 2018 and compared patients undergoing posterior lumbar instrumentation with image guidance using and not using multimodal IOM. Monitored and unmonitored surgeries were performed by the same surgeons, ruling out variability in intersurgeon technique. Surgical and neurologic complication rates were compared between these 2 cohorts.

RESULTS

A total of 163 patients were selected (110 in the nonmonitored cohort vs. 53 in the IOM cohort). Nineteen signal changes were noted. Only 3 of the 19 patients with signal changes had associated neurologic deficits postoperatively (positive predictive value 15.7%). There were 5 neurologic deficits that were observed in the nonmonitored cohort and 8 deficits observed in the monitored cohort. Transient neurologic deficit was significantly higher in the monitored cohort per case (P < 0.0198) and per screw (P < 0.0238); however, there was no difference observed between the 2 cohorts when considering permanent neurologic morbidity per case (P < 0.441) and per screw (P < 0.459).

CONCLUSIONS

The addition of IOM to cases using image guidance does not appear to decrease long-term postoperative neurologic morbidity and may have a reduced diagnostic role given availability of intraoperative image-guidance systems.

Improved potential quality of intraoperative transcranial motor-evoked potentials by navigated electrode placement compared to the conventional ten-twenty system

Intraoperative neurophysiological monitoring of transcranial motor-evoked potentials (tcMEPs) may fail to produce a serviceable signal due to displacements by mass lesions. We hypothesize that navigated placement of stimulation electrodes yields superior potential quality for tcMEPs compared to the conventional 10–20 placement. We prospectively included patients undergoing elective cranial surgery with intraoperative monitoring of tcMEPs. In addition to electrode placement as per the 10–20 system, an electrode pair was placed at a location corresponding to the hand knob area of the primary motor cortex (M1) for every patient, localized by a navigation system during surgical setup. Twenty-five patients undergoing elective navigated surgery for intracranial tumors (n = 23; 92%) or vascular lesions (n = 2; 8%) under intraoperative monitoring of tcMEPs were included between June and August 2019 at our department. Stimulation and recording of tcMEPs was successful in every case for the navigated electrode pair, while stimulation by 10–20 electrodes did not yield baseline tcMEPs in two cases (8%) with anatomical displacement of the M1. While there was no significant difference between baseline amplitudes, mean potential quality decreased significantly by 88.3 µV (− 13.5%) for the 10–20 electrodes (p = 0.004) after durotomy, unlike for the navigated electrodes (− 28.6 µV [− 3.1%]; p = 0.055). For patients with an anatomically displaced M1, the navigated tcMEPs declined significantly less after durotomy (− 3.6% vs. 10–20: − 23.3%; p = 0.038). Navigated placement of tcMEP electrodes accounts for interindividual anatomical variance and pathological dislocation of the M1, yielding more consistent potentials and reliable potential quality.

What is the predictive value of intraoperative somatosensory evoked potential monitoring for postoperative neurological deficit in cervical spine surgery?-a meta-analysis

BACKGROUND CONTEXT

Cervical decompression and fusion surgery remains a mainstay of treatment for a variety of cervical pathologies. Potential intraoperative injury to the spinal cord and nerve roots poses nontrivial risk for consequent postoperative neurologic deficits. Although neuromonitoring with intraoperative somatosensory evoked potentials (SSEPs) is often used in cervical spine surgery, its therapeutic value remains controversial.

PURPOSE

The purpose of the present study was to evaluate whether significant SSEP changes can predict postoperative neurologic complications in cervical spine surgery. A subgroup analysis was performed to compare the predictive power of SSEP changes in both anterior and posterior approaches.

STUDY DESIGN

The present study was a meta-analysis of the literature from PubMed, Web of Science, and Embase to identify prospective/retrospective studies with outcomes of patients who underwent cervical spine surgeries with intraoperative SSEP monitoring.

PATIENT SAMPLE

The total cohort consisted of 7,747 patients who underwent cervical spine surgery with intraoperative SSEP monitoring.

METHODS

Inclusion criteria for study selection were as follows: (1) prospective or retrospective cohort studies, (2) studies conducted in patients undergoing elective cervical spine surgery not due to aneurysm, tumor, or trauma with intraoperative SSEP monitoring, (3) studies that reported postoperative neurologic outcomes, (4) studies conducted with a sample size ≥20 patients, (5) studies with only adult patients ≥18 years of age, (6) studies published in English, (7) studies inclusive of an abstract.

OUTCOME MEASURES

The sensitivity, specificity, diagnostic odds ratio (DOR), and likelihood ratios of overall SSEP changes, reversible SSEP changes, irreversible SSEP changes, and SSEP loss for predicting postoperative neurological deficit were calculated.

RESULTS

The total rate of postoperative neurological deficits was 2.50% (194/7,747) and the total rate of SSEP changes was 7.36% (570/7,747). The incidence of postoperative neurological deficit in patients with intraoperative SSEP changes was 16.49% (94/570) while only 1.39% (100/7,177) in patients without. All significant intraoperative SSEP changes had a sensitivity of 46.0% and specificity of 96.7% with a DOR of 27.32. Reversible and irreversible SSEP changes had sensitivities of 17.7% and 37.1% and specificities of 97.5% and 99.5%, respectively. The DORs for reversible and irreversible SSEP changes were 9.01 and 167.90, respectively. SSEP loss had a DOR of 51.39, sensitivity of 17.3% and specificity 99.6%. In anterior procedures, SSEP changes had a DOR of 9.60, sensitivity of 34.2%, and specificity of 94.7%. In posterior procedures, SSEP changes had a DOR of 13.27, sensitivity of 42.6%, and specificity of 94.0%.

CONCLUSIONS

SSEP monitoring is highly specific but weakly sensitive for postoperative neurological deficit following cervical spine surgery. The analysis found that patients with new postoperative neurological deficits were nearly 27 times more likely to have had significant intraoperative SSEP change. Loss of SSEP signals and irreversible SSEP changes seem to indicate a much higher risk of injury than reversible SSEP changes.

Filum terminale lipomas-the role of intraoperative neuromonitoring

BACKGROUND

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

CONCLUSION

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

Basics of Neuromonitoring and Anesthetic Considerations

It is important anesthesiologists understand the pharmacologic interactions of anesthetics and monitoring of evoked potentials or electroencephalography. Intravenous and inhaled anesthetics have varying degrees of influence on different monitoring modalities and can affect amplitude and latency of evoked potentials or voltage and frequency of electroencephalography. Sudden and abrupt changes in monitoring are concerning and should be evaluated promptly. The source of the changes is related to sudden modifications of anesthesia delivery, variations in vital parameters, or the result of surgical manipulation. Identifying sources of abnormal signals and determining the reason for the change should be addressed immediately and corrected accordingly.

Neurophysiological monitoring during anterior cervical discectomy and fusion for ossification of the posterior longitudinal ligament

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Postoperative neurological complications are not rare in ACDF for OPLL pathology.

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Multimodal IONM may reduce neurological damage in ACDF surgery for OPLL.

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IONM and preoperative myelopathy were associated with neurological complications.

Objective

This study aimed to investigate the value of intraoperative neurophysiological monitoring (IONM) in anterior cervical spine discectomy with fusion (ACDF) for ossification of the posterior longitudinal ligament (OPLL).

Methods

Patients who underwent multimodal IONM (transcranial electrical motor-evoked potentials [tcMEP], somatosensory-evoked potentials, and continuous electromyography) for ACDF from 2009 to 2019 were compared to historical controls from 2003 to 2009. The rates of postoperative neurological deficits, neurophysiological warnings, and their characteristics were analyzed.

Results

Among 196 patients, postoperative neurological deficit rates were 3.79% and 14.06% in the IONM and historical control (non-IONM) groups, respectively (p < 0.05). The use of IONM (OR: 0.139, p = 0.003) and presence of myelopathy (OR: 8.240, p = 0.013) were associated with postoperative neurological complications on multivariate regression. In total, 23 warnings were observed during IONM (17 tcMEP and/or electromyography; six electromyography). Sensitivity and specificity of IONM warnings for detecting neurological complications were 84.2% and 93.7%, respectively.

Conclusions

IONM, especially multimodal IONM, may be a useful tool to detect neurological damage in ACDF for high-risk conditions such as OPLL with pre-existing myelopathy.

Significance

The utility of IONM in ACDF for OPLL has not been evaluated due to its rarity. This study supports the use of IONM in cervical OPLL with myelopathy.

Predictive Value of Transcranial Evoked Potential Monitoring for Intramedullary Spinal Cord Tumors

BACKGROUND

 Intraoperative neurophysiologic monitoring (IONM) has increased patient safety and extent of resection in patients with eloquent brain tumors. Despite its comprehensive capability for the resection of intramedullary spinal cord tumors (ISCTs), the application during the resection of these tumors is controversial.

METHODS

 We retrospectively analyzed the resection of ISCTs in 83 consecutive cases. IONM was performed in all cases. Each patient's motor status and the McCormick scale was determined preoperatively, directly after surgery, at the day of discharge, and at long-term follow-up.

RESULTS

 IONM was feasible in 71 cases (85.5%). Gross total resection was performed in 75 cases (90.4%). Postoperatively, patients showed new transient deficits in 12 cases (14.5%) and new permanent deficits in 12 cases (14.5%). The mean McCormick variance between baseline and long-term follow-up was - 0.08 ± 0.54. IONM's sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for the patient's motor status at the day of discharge was 75.0%, 64.7%, 45.5%, and 86.8%. It was 88.9%, 59.7%, 24.2%, and 97.4% for the motor outcome at long-term follow-up. Patients experienced postoperative complications in 15 cases (18.1%).

CONCLUSION

 IONM, as performed in the present study, shows a high sensitivity and NPV but low specificity and PPV, particularly for the patient's motor status at the long-term follow-up. As far as practicable by a retrospective study on IONM, our results confirm IONM's usefulness for its application during the resection of ISCTs. However, these results must be approved by a prospective study.

Management of Extramedullary Intradural Spinal Tumors: The Impact of Clinical Status, Intraoperative Neurophysiological Monitoring and Surgical Approach on Outcomes in a 12-Year Double-Center Experience

Objective: Intradural Extramedullary (IDEM) tumors are usually treated with surgical excision. The aim of this study was to investigate the impact on clinical outcomes of pre-surgical clinical conditions, intraoperative neurophysiological monitoring (IONM), surgical access to the spinal canal, histology, degree of resection and intra/postoperative complications.

Methods: This is a retrospective observational study analyzing data of patients suffering from IDEM tumors who underwent surgical treatment over a 12 year period in a double-center experience. Data were extracted from a prospectively maintained database and included: sex, age at diagnosis, clinical status according to the modified McCormick Scale (Grades I-V) at admission, discharge, and follow-up, tumor histology, type of surgical access to the spinal canal (bilateral laminectomy vs. monolateral laminectomy vs. laminoplasty), degree of surgical removal, use and type of IONM, occurrence and type of intraoperative complications, use of Ultrasonic Aspirator (CUSA), radiological follow-up.

Results: A total number of 249 patients was included with a mean follow-up of 48.3 months. Gross total resection was achieved in 210 patients (84.3%) mostly in Schwannomas (45.2%) and Meningiomas (40.4%). IONM was performed in 162 procedures (65%) and D-wave was recorded in 64.2% of all cervical and thoracic locations (99 patients). The linear regression diagram for McCormick grades before and after surgery (follow-up) showed a correlation between preoperative and postoperative clinical status. A statistically significant correlation was found between absence of worsening of clinical condition at follow-up and use of IONM at follow-up (p = 0.01) but not at discharge. No associations were found between the choice of surgical approach and the extent of resection (p = 0.79), the presence of recurrence or residual tumor (p = 0.14) or CSF leakage (p = 0.25). The extent of resection was not associated with the use of IONM (p = 0.91) or CUSA (p = 0.19).

Conclusion: A reliable prediction of clinical improvement could be made based on pre-operative clinical status. The use of IONM resulted in better clinical outcomes at follow-up (not at discharge), but no associations were found with the extent of resection. The use of minimally invasive approaches such as monolateral laminectomy showed to be effective and not associated with worse outcomes or increased complications.

Surgical outcomes and factors related to postoperative motor and sensory deficits in resection for 244 cases of spinal schwannoma

In a large cohort the clinical presentation, management and outcomes of spinal schwannoma and factors related to postoperative motor and sensory deficits were invesgtigated. In 244 patients (males: 126, females: 118, average age 51.8 y) at one center, significant factors related to postoperative motor and sensory deficits were identified. Tumors were in the cervical (n = 79, 32.4%), lumbar (n = 66), thoracolumbar (T11-L1) (n = 55), and thoracic (n = 39) regions, and 5 patients had sacrum tumors. The rates of postoperative motor and sensory deterioration were 13.1% and 20.5%, respectively. The risk factors for motor deterioration were preoperative motor weakness, preoperative gait disturbance, dumbbell Eden type II, subtotal resection, and operative time, and those for postoperative sensory deficit were preoperative gait disturbance and subtotal resection. Of 12 patients with significant TcMEP changes, 11 had a new motor deficit after surgery; and of 216 patients with stable TcMEP data, 196 were neurologically intact after surgery (true negative) and 20 (11.0%) had deficits in the immediate postoperative stage (false negative). These deficits resolved during hospitalization for most patients. Of 15 patients with TcMEP deterioration and recovery, 11 (93.3%) had no motor deficits after surgery (p < 0.01).

The ethical and legal status of neurosurgical guidelines: the neurosurgeon's golden fleece or Achilles' heel?

Neurosurgical guidelines are fundamental for evidence-based practice and have considerably increased both in number and content over the last decades. Yet, guidelines in neurosurgery are not without limitations, as they are overwhelmingly based on low-level evidence. Such recommendations have in the past been occasionally overturned by well-designed randomized controlled trials (RCTs), demonstrating the volatility of poorly underpinned evidence. Furthermore, even RCTs in surgery come with several limitations; most notably, interventions are often insufficiently standardized and assume a homogeneous patient population, which is not always applicable to neurosurgery. Lastly, guidelines are often outdated by the time they are published and smaller fields such as neurosurgery may lack a sufficient workforce to provide regular updates. These limitations raise the question of whether it is ethical to use low-level evidence for guideline recommendations, and if so, how strictly guidelines should be adhered to from an ethical and legal perspective. This article aims to offer a critical approach to the ethical and legal status of guidelines in neurosurgery. To this aim, the authors discuss: 1) the current state of neurosurgical guidelines and the evidence they are based on; 2) the degree of implementation of these guidelines; 3) the legal status of guidelines in medical disciplinary cases; and 4) the ethical balance between confident and critical use of guidelines. Ultimately, guidelines are neither laws that should always be followed nor purely academic efforts with little practical use. Every patient is unique, and tailored treatment defined by the surgeon will ensure optimal care; guidelines play an important role in creating a solid base that can be adhered to or deviated from, depending on the situation. From a research perspective, it is inevitable to rely on weaker evidence initially in order to generate more robust evidence later, and clinician-researchers have an ethical duty to contribute to generating and improving neurosurgical guidelines.

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.

A Retrospective Study of Surgical Correction for Spinal Deformity with and without Osteotomy to Compare Outcome Using Intraoperative Neurophysiological Monitoring with Evoked Potentials

BACKGROUND This study aimed to evaluate the effects of different combined evoked potentials monitoring modes for non-osteotomy and osteotomy surgery of spinal deformity, and to select individualized modes for various surgeries. MATERIAL AND METHODS We retrospectively reviewed a total of 188 consecutive cases undergoing spinal deformity correction. All patients were classified into 2 cohorts: non-osteotomy (Group A) and osteotomy (Group B). According to intraoperative evoked potential monitoring mode, Group A was divided into 2 sub-groups: A1 [spinal somatosensory evoked potential (SSEP)/motor evoked potential (MEP), n=67)] and A2 [SSEP/MEP/descending neurogenic evoked potential (DNEP), n=52]. Group B was classified as B1 (SSEP/MEP, n=27) and B2 (SSEP/MEP/DNEP, n=42). The demographics, surgical parameters, and evoked potential events of different combined monitoring modes were analyzed within each group. RESULTS The baselines of SSEP/MEP/DNEP in all cases were elicited successfully. Three cases with evoked potential (EP) events (2 with MEP changes and 1 with SSEP/MEP change) were noted in Group A1 and 1 with SSEP change in Group A2, with no neurological complications. Thirteen cases in Group B1 were positive for MEP intraoperatively, including 16 EP events (13 with MEP change and 3 with both SSEP+MEP changes), with no neural complications. In Group B2, 15 cases had 21 EP events, including 12 with MEP change and 2 with SSEP+MEP changes, with no complications. Postoperative neurological complications were observed in 5 of the 7 cases with SS4EP/DNEP changes. CONCLUSIONS Intraoperative simultaneous SSEP/MEP can effectively reflect neurological function in non-osteotomy spinal surgery patients. Simultaneous SSEP/MEP/DNEP can effectively avoid the unnecessary interference by false-positive results of MEP during osteotomy.