Diagnostic and therapeutic values of intraoperative electrophysiological neuromonitoring during resection of intradural extramedullary spinal tumors: a single-center retrospective cohort and meta-analysis

Impact of Preoperative Motor Status for the Positive Predictive Value of Transcranial Motor-Evoked Potentials Alerts in Thoracic Spine Surgery: A Prospective Multicenter Study by the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research

STUDY DESIGN

Prospective multicenter study.

OBJECTIVE

To investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in thoracic spine surgery and evaluate the impact of specific factors associated with positive predictive value (PPV).

METHODS

One thousand hundred and fifty-six cases of thoracic spine surgeries were examined by comparing patient backgrounds, disease type, preoperative motor status, and Tc-MEP alert timing. Tc-MEP alerts were defined as an amplitude decrease of more than 70% from the baseline waveform. Factors were compared according to preoperative motor status and the result of Tc-MEP alerts. Factors that showed significant differences were identified by univariate and multivariate analysis.

RESULTS

Overall sensitivity was 91.9% and specificity was 88.4%. The PPV was significantly higher in the preoperative motor deficits group than in the preoperative no-motor deficits group for both high-risk (60.3% vs 38.3%) and non-high-risk surgery groups (35.1% vs 12.8%). In multivariate logistic analysis, the significant factors associated with true positive were surgical maneuvers related to ossification of the posterior longitudinal ligament (odds ratio = 11.88; 95% CI: 3.17-44.55), resection of intradural intramedullary spinal cord tumor (odds ratio = 8.83; 95% CI: 2.89-27), preoperative motor deficit (odds ratio = 3.46; 95% CI: 1.64-7.3) and resection of intradural extramedullary spinal cord tumor (odds ratio = 3.0; 95% CI: 1.16-7.8). The significant factor associated with false positive was non-attributable alerts (odds ratio = .28; 95% CI: .09-.85).

CONCLUSION

Surgeons are strongly encouraged to use Tc-MEP in patients with preoperative motor deficits, regardless of whether they are undergoing high-risk spine surgery or not. Knowledge of PPV characteristics will greatly assist in effective Tc-MEP enforcement and minimize neurological complications with appropriate interventions.

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

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

Systematic Review Comparing Open Versus Minimally Invasive Surgical Management of Intradural Extramedullary Tumours (IDEM)

Background/Objectives: Intradural extramedullary (IDEM) spinal tumours are relatively rare and predominantly benign. Gross total resection (GTR) has been demonstrated as an effective treatment, with increasing evidence supporting the use of minimally invasive techniques to achieve GTR. This study reviews the current surgical management options for IDEM tumours and their outcomes. Methods: A systematic literature search without meta-analysis was conducted by two independent reviewers in December 2024. The population of interest comprised patients who underwent surgical treatment for IDEM tumours. Outcomes assessed included the extent of resection, postoperative neurological function, and complications. Results: Fifty-seven articles met the inclusion criteria, providing data on 4695 IDEM cases, of which 3495 were managed through open surgery and 750 via minimally invasive surgery. The extent of resection was high, with a mean GTR > 90% across studies. Open laminectomy and unilateral minimally invasive hemilaminectomy were the most common surgical approaches. Complications, such as cerebrospinal fluid leaks, were less frequent following minimally invasive procedures vs. open surgery (11.1% vs. 14.3%). Minimally invasive surgery also led to improved postoperative functional outcomes (mean McCormick score change -1.30 vs. -0.64) and a lower recurrence rate (1.4% vs. 10.0%). Conclusions: Whilst open surgery yields acceptable rates of resection and neurological improvement, there is growing evidence that minimally invasive surgery can achieve comparable, if not superior, rates of resection with fewer complications, leading to lower costs and shorter hospital stays.

Epidemiology study on the prognostic factors of intradural extramedullary spinal tumors

Introduction

Intradural extramedullary (IDEM) tumors are rare tumors of the spinal cord. Currently, there is no evidence on the factors that predict poor outcomes in the patients. The objective of this study was to determine the prognostic factors that are associated with poor outcomes in IDEM tumors.

Materials and Methods

Patients 18 years and older with IDEM tumors who underwent surgery at our institute were identified and retrospectively reviewed. The patient's demographic data, risk factors, and modified McCormick Scale score were collected.

Results

A total of 129 patients with IDEM were included in this study. The age ranged from 19 to 79 years (mean 51.3 years), with a predominantly female population (85 patients, 65.9%). Eighty-nine (68.9%) patients had a good outcome, while 40 (31.0%) patients had a poor outcome. The significant factors for poor outcomes included the number of vertebral levels removed for tumor access (adjusted odds ratio [OR] = 3.80, 95% confidence interval [CI] =1.30-11.08, P = 0.013); pathology other than meningioma, schwannoma, and neurofibroma (adjusted OR = 18.86, 95% CI = 2.16-164.49, P = 0.007); and bowel/bladder involvement (adjusted OR = 3.47, 95% CI = 1.15-10.39, P = 0.027).

Conclusion

We found that the factors for poor outcomes included bowel/bladder involvement, number of vertebral levels removed for tumor access, and pathology other than meningioma, schwannoma, and neurofibroma.

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.

Long-Term Functional Outcomes Following Surgical Treatment of Spinal Schwannomas: A Population-Based Cohort Study

Spinal schwannomas are the second most common form of primary intradural spinal tumor. Despite being benign, they may cause spinal cord compression and subsequently acute or chronic neurological dysfunction. The primary treatment is surgical resection. The aim of this study was to identify pre- and postoperative predictors of favorable outcomes after surgical treatment for spinal schwannoma. All adult patients surgically treated for spinal schwannoma between 2006 and 2020 were eligible for inclusion. Medical records and imaging data were retrospectively reviewed. The primary outcome measures were neurological improvement according to the modified McCormick Scale (mMC) and changes in motor deficit, sensory deficit, gait disturbance, bladder dysfunction, and pain at long-term follow-up. In total, 180 patients with a median follow-up time of 4.4 years were included. Pain was the most common presenting symptom (87%). The median time between symptom presentation and surgery was 12 months, while the median time between diagnosis (first MRI) and surgery was 3 months. Gross total resection (GTR) was achieved in 150 (83%) patients and the nerve root could be preserved in 133 (74%) patients. A postoperative complication occurred in 10 patients (5.6%). There were significant postoperative improvements in terms of motor, sensory, gait, and bladder functions, as well as pain (p < 0.001). Of these symptoms, bladder dysfunction was the one most often improved, with complete symptom resolution in all cases. However, no other predictors of improvement could be identified. There were three cases of recurrence after GTR and nine cases of regrowth after STR. Reoperation was performed in six (3.3%) cases. GTR was associated with a significant improvement in neurological status at long-term follow-up and increased the chance of progression-free survival.

Feasibility of multimodal intraoperative neurophysiological monitoring for extramedullary spinal cord tumor surgery in elderly patients

BACKGROUND/PURPOSE

Extramedullary spinal cord tumors (EMSCTs) are mostly benign tumors which are increasingly diagnosed and operatively treated in the elderly. While there are hints that multimodal intraoperative neurophysiological monitoring (IONM) could be influenced by age and age-related comorbidities, no study has ever systematically evaluated its feasibility and value for EMSCT surgery in elderly patients.

METHODS

We retrospectively evaluated all patients with microsurgical EMSCT resection under continuous multimodal IONM with SSEPs, MEPs and electromyography between 2016 and 2020. Epidemiological, clinical, imaging and operative/IONM records as well as detailed individual outcomes were analyzed and compared for the cohort < / ≥ 65 years.

RESULTS

Mean age was 45 years in cohort < 65 years (n = 109) and 76 years in cohort ≥ 65 years (n = 64), while baseline/operative characteristics did not significantly differ. Mean baseline SSEPs' latencies (left-right average) were significantly higher in the cohort ≥ 65 years for both median (20.9 ms vs. 22.1 ms; p < 0.01) and tibial nerve (42.9 ms vs. 46.1 ms; p < 0.01) without significant differences for SSEPs' amplitudes. Stimulation intensity to elicit intraoperative MEPs was significantly higher in the cohort ≥ 65 years (surrogate-marker: left-right-averaged quotient ID1-muscle/abductor-hallucis-muscle; 1.6 vs. 2.1; p < 0.001). Intraoperatively, SSEP and MEP monitoring were feasible in 99%/100% and 99%/98% for the cohort < / ≥ 65 years without significant differences in rates for significant IONM changes during surgery or postoperatively new sensorimotor deficits. Sensitivity of IONM was 29%/43%, specificity 99%/98%, positive and negative predictive values 67%/75% and 95%/93% for the cohort < / ≥ 65 years. Overall, age was no risk factor for IONM feasibility or rate of significant IONM changes.

DISCUSSION

Multimodal IONM is feasible/reliable for EMSCT surgery in elderly patients. An age-related prolongation of SSEPs' latencies and demand for higher stimulation intensities for MEPs' elicitation has to be considered.

Is There a Role for Intraoperative Neuromonitoring in Intradural Extramedullary Spine Tumors? Results and Indications from an Institutional Series

While intraoperative neurophysiological monitoring (IONM) is considered a standard for intramedullary spinal cord tumor surgery, the effective role of IONM in intradural extramedullary (IDEM) tumors is still debated. We present the results of 60 patients affected by IDEM tumors undergoing surgery with the aid of IONM. Each patient was evaluated according to the modified McCormick scale (MMS) at admission, discharge and at follow-up. During surgery, motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs) were studied using the Medtronic NIM-eclipse^® 32-channel system (Medtronic Xomed, Inc. 6743 Southpoint Drive North Jacksonville FL USA). Patients' age, gender and tumor location did not affect MMS modifications. Tumors involving more than three levels had an increased likelihood of MMS worsening, while meningioma pathology was associated with worse preoperative and 1-year follow-up MMS. No MEP amplitude ratio was able to predict clinical variations, while intraoperative SEP worsening was associated with 100% risk of poor MMS at discharge and with 50% risk of poor MMS at long-term follow-up. In our opinion, SEP monitoring is a valid tool that may contribute to the preservation of the patient's neurological status. MEP monitoring is not mandatory in IDEM surgery while more studies are required to explore the feasibility and the role of D-wave in this kind of surgery.

Intradural extramedullary tumor location in the axial view affects the alert timing of intraoperative neurophysiologic monitoring

OBJECTIVE

Intraoperative neurophysiologic monitoring (IONM) reportedly helps prevent postoperative neurological complications following high-risk spinal cord surgeries. There are negative and positive reports about using IONM for intradural extramedullary (IDEM) tumors. We investigated factors affecting alerts of IONM in IDEM tumor surgery.

METHODS

We analyzed 39 patients with IDEM tumors who underwent surgery using IONM at our hospital between January 2014 and March 2021. Neurological symptoms were evaluated pre- and postoperatively using the manual muscle test (MMT). All patients were evaluated to ascertain the tumor level and location in the axial view, the operative time, intraoperative bleeding volume, and histological type. Additionally, the intraoperative procedure associated with significant IONM changes in transcranial electrical stimulation muscle-evoked potential was investigated.

RESULTS

There were 11 false-positive and 16 true-negative cases. There was one true-positive case and one false-negative case; the monitoring accuracy achieved a sensitivity of 50%, a specificity of 59%, a positive predictive value of 8%, and a negative predictive value of 94%. In the 22 alert cases, if the tumor was located anterolateral in the axial view, alerts were triggered with a significant difference (p = 0.02) during tumor resection. Alerts were generated for fifteen patients during tumor resection; nine (60%) showed waveform improvement by intervention and were classified as rescue cases.

CONCLUSION

Alert is probably triggered during tumor resection for anterolaterally located tumors. Alerts during tumor resection procedures were more likely to be rescued than other procedures in IDEM tumor surgery.

Predictive Value of Motor Evoked Potentials in the Resection of Intradural Extramedullary Spinal Tumors in Children

This study aimed to evaluate the predictive value of motor evoked potentials (MEP) in the resection of pediatric intradural extramedullary (IDEM) tumors. Additionally, we aimed to assess the impact of MEP alerts on the extent of tumor resection. Medical records of pediatric patients who underwent resection of IDEM tumors with the assistance of MEP between March 2011 and October 2020 were reviewed. The occurrence of postoperative motor deficits was correlated with intraoperative MEP alerts. Sixteen patients were included. MEP alerts appeared in 2 patients (12.5%), being reflective of new postoperative motor deficits. Among the remaining 14 patients without any intraoperative MEP alerts, no motor decline was found. Accordingly, MEP significantly predicted postoperative motor deficits, reaching sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 100% (p < 0.001). In the absence of MEP alerts, 11 out of 14 patients (78.6%) underwent GTR, while no patient with intraoperative IONM alerts underwent GTR (p = 0.025). Although MEP alerts limit the extent of tumor resection, the high sensitivity and PPV of MEP underline its importance in avoiding iatrogenic motor deficits. Concurrently, high specificity and NPV ensure safer tumor excision. Therefore, MEP can reliably support surgical decisions in pediatric patients with IDEM tumors.

The Utility of Transcranial Stimulated Motor-Evoked Potential Alerts in Cervical Spine Surgery Varies Based on Preoperative Motor Status

STUDY DESIGN

A prospective multicenter observational study.

OBJECTIVE

The aim was to investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in cervical spine surgery and identify factors associated with positive predictive value when Tc-MEP alerts are occurred.

SUMMARY OF BACKGROUND DATA

The sensitivity and specificity of Tc-MEP for detecting motor paralysis are high; however, false-positives sometimes occur.

MATERIALS AND METHODS

The authors examined Tc-MEP in 2476 cases of cervical spine surgeries and compared patient backgrounds, type of spinal disorders, preoperative motor status, surgical factors, and the types of Tc-MEP alerts. Tc-MEP alerts were defined as an amplitude reduction of more than 70% from the control waveform. Tc-MEP results were classified into two groups: false-positive and true-positive, and items that showed significant differences were extracted by univariate analysis and detected by multivariate analysis.

RESULTS

Overall sensitivity was 66% (segmental paralysis: 33% and lower limb paralysis: 95.8%) and specificity was 91.5%. Tc-MEP outcomes were 33 true-positives and 233 false-positives. Positive predictive value of general spine surgery was significantly higher in cases with a severe motor status than in a nonsevere motor status (19.5% vs . 6.7%, P =0.02), but not different in high-risk spine surgery (20.8% vs . 19.4%). However, rescue rates did not significantly differ regardless of motor status (48% vs . 50%). In a multivariate logistic analysis, a preoperative severe motor status [ P =0.041, odds ratio (OR): 2.46, 95% confidence interval (95% CI): 1.03-5.86] and Tc-MEP alerts during intradural tumor resection ( P <0.001, OR: 7.44, 95% CI: 2.64-20.96) associated with true-positives, while Tc-MEP alerts that could not be identified with surgical maneuvers ( P =0.011, OR: 0.23, 95% CI: 0.073-0.71) were associated with false-positives.

CONCLUSION

The utility of Tc-MEP in patients with a preoperative severe motor status was enhanced, even in those without high-risk spine surgery. Regardless of the motor status, appropriate interventions following Tc-MEP alerts may prevent postoperative paralysis.

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.

Emerging Super-specialty of Neurology: Intraoperative Neurophysiological Monitoring (IONM) and Experience in Various Neurosurgeries at a Tertiary Care Hospital in Doha, Qatar

Introduction

Intraoperative neurophysiological monitoring (IONM) helps in better patient outcomes by minimizing risks related to the functional status of the nervous system during surgical procedures. An IONM alert to the surgical team during the surgery can help them identify the cause and take immediate corrective action. IONM confers possible benefits, including improved surgical morbidity and mortality, better patient care, minimal neurological deficits, reduced hospital stay, medical costs, and litigation risk. In addition, a highly skilled IONM team will make a better patient outcome.

Methods

We retrospectively reviewed 62 consecutive patients who underwent intracranial and spinal neurosurgical procedures. Multimodality IONM was utilized, including somatosensory evoked potentials, transcranial electrical motor evoked potential, spontaneous and triggered electromyography, electroencephalography, electrocorticography, cortical sensory mapping, and direct electrical cortical stimulation. Of a total of 62 patients, two patients revealed neurotonic EMG discharges during IONM, and most patients woke up without any new neurological deficit.

Results

Sixty-two patients were included, ranging from age 5 to 77 years (mean 43.5 years), with 54.8% men and 45.2% female. Multimodality IONM was used in all patients. Two EMG alerts were recorded during IONM, during a brain tumor resection, and right acetabular hip surgery with postoperative right foot drop.

Conclusion

Multimodality IONM is the gold standard of care for any surgical services and is used as real-time monitoring of functional integrity of neural structures at risk. If utilized by trained and expert teams, numerous surgeries may benefit from multimodality intraoperative neurophysiologic monitoring.

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).