Intraoperative Neuromonitoring Data Research Articles

Machine learning allows expert level classification of intraoperative motor evoked potentials during neurosurgical procedures

ObjectiveTo develop and evaluate machine learning (ML) approaches for muscle identification using intraoperative motor evoked potentials (MEPs), and to compare their performance to human experts. BackgroundThere is an unseized opportunity to apply ML analytic techniques to the world of intraoperative neuromonitoring (IOM). MEPs are the ideal candidates given the importance of their correct interpretation during a surgical operation to the brain or the spine. In this work, we develop and test a set of different ML models for muscle identification using intraoperative MEPs and compare their performance to human experts. In addition, we provide a review of the available literature on current ML applications to IOM data in neurosurgery. MethodsWe trained and tested five different ML classifiers on a MEP database developed from six different muscles in patients who underwent brain or spinal cord surgery. MEPs were obtained by both transcranial (TES) and direct cortical stimulation (DCS) protocols. The models were evaluated within a single patient and on previously unseen patients, considering signals from TES and DCS both independently and mixed. Ten expert neurophysiologists classified a set of 50 randomly selected MEPs, and their performance was compared to the best performing model. ResultsA total of 25.423 MEPs were included in the study. Random Forest proved to be the best performing model with 99 % accuracy in the single patient dataset task and a 78 %–94 % accuracy range on previously unseen patients. The model performance was maximized by representing MEPs as a set of features typically employed in signal processing compared to traditional neurophysiological parameters. The classification ability of the Random Forest model between six different muscles and across different MEP acquisition modalities (79 %) significantly exceeded that of human experts (mean 48 %). ConclusionsCarefully selected ML models proved to have reliable capacity of extracting meaningful information to classify intraoperative MEPs using a limited number of features, proving robustness across patients and signal acquisition modalities, outperforming human experts, and with the potential to act as decision support systems to the IOM team. Such encouraging results lay the path to further explore the underlying nature of clinically important signals, with the aim to continue to produce useful applications to make surgeries safer and more efficient.

31. Can the recovery of root-level intraoperative neuromonitoring data result in a lower risk for postoperative lower extremity weakness in spine deformity surgery?

31. Can the recovery of root-level intraoperative neuromonitoring data result in a lower risk for postoperative lower extremity weakness in spine deformity surgery?

Does an improvement in cord-level intraoperative neuromonitoring data lead to a reduced risk for postoperative neurologic deficit in spine deformity surgery?

To determine if an improvement in cord-level intraoperative neuromonitoring (IONM) data following data loss results in a reduced risk for new postoperative motor deficit in pediatric and adult spinal deformity surgery. A consecutive series of 1106 patients underwent spine surgery from 2015 to 2023 by a single surgeon. Cord alerts were defined by Somatosensory-Evoked Potentials (SSEP; warning criteria: 10% increase in latency or > 50% loss in amplitude) and Motor-Evoked Potentials (MEP; warning criteria: 75% loss in amplitude without return to acceptable limits after stimulation up 100V above baseline level). Timing of IONM loss and recovery, interventions, and baseline/postoperative day 1 (POD1) lower extremity motor scores were analyzed. IONM Cord loss was noted in 4.8% (53/11,06) of patients and 34% (18/53) with cord alerts had a POD1 deficit compared to preoperative motor exam. MEP and SSEP loss attributed to 98.1% (52/53) and 39.6% (21/53) of cord alerts, respectively. Abnormal descending neurogenic-evoked potential (DNEP) was seen in 85.7% (12/14) and detected 91.7% (11/12) with POD1 deficit. Abnormal wake-up test (WUT) was seen in 38.5% (5/13) and detected 100% (5/5) with POD1 deficit. Most cord alerts occurred during a three-column osteotomy (N = 23/53, 43%); decompression (N = 12), compression (N = 7), exposure (N = 4), and rod placement (N = 14). Interventions were performed in all 53 patients with cord loss and included removing rods/less correction (N = 11), increasing mean arterial pressure alone (N = 10), and further decompression with three-column osteotomy (N = 9). After intervention, IONM data improved in 45(84.9%) patients (Full improvement: N = 28; Partial improvement: 17). For those with full and partial IONM improvement, the POD1 deficit was 10.7% (3/28) and 41.2% (7/17), respectively. For those without any IONM improvement (15.1%, 8/53), 100% (8/8) had a POD1 deficit, P < 0.001. A full or partial improvement in IONM data loss after intraoperative intervention was significantly associated with a lower risk for POD1 deficit with an absolute risk reduction of 89.3% and 58.8%, respectively. All patients without IONM improvement had a POD1 neurologic deficit.

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

To identify and characterize events of deterioration in intraoperative neuromonitoring data during correction procedures for thoracic and lumbar abnormal spinal curvature in young patients. Records of 1,127 cases were retrospectively reviewed to identify events with deterioration of the neuromonitoring data. General etiological and demographic variables were summarized, and neuromonitoring events were studied and characterized. Adolescent idiopathic cases were associated with female dominance and older age. Nonadolescent idiopathic cases were associated with a higher rate of neuromonitoring events. The neuromonitoring events evolved during the different procedural stages, were primarily reflected in the motor-evoked potential data and affected a range of neural structures to varying degrees. Most of the events were resolved, partially or completely, following a corresponding intervention by the surgical team, before the end of the procedure. Significant immediate weakness of the lower extremities was demonstrated in patients with unresolved neuromonitoring events, most of them were nonadolescent idiopathic patients. Neurophysiological monitoring enables the intraoperative assessment of the integrity of neural pathways and allows the detection of surgery-related impending neural injuries. Neuromonitoring contributes to intraoperative decision making, either when data are uneventful and allow confident continuation or when data deteriorate and lead to corresponding intervention. Further awareness should be paid to the vulnerable characteristics of the patient, surgery course, and neuromonitoring data. Proper interpretation of the neuromonitoring data, together with corresponding intervention by the surgeon when necessary, has the potential to reduce postoperative neurological insults and improve clinical outcomes.

Stereoscopic Monitoring Technique for Motor Area Tumors

The balance between comprehensive intraoperative neurophysiological monitoring (IONM) for both upper and lower limbs while ensuring the reliability of motor evoked potentials (MEPs) is paramount in motor area surgery. It is commonly difficult to obtain good simultaneous stimulation of both upper and lower limbs. A series of factors can bias MEP accuracy, and inappropriate stimulation intensity can result in unreliable monitoring. The presented IONM technique is based on the concurrent use of both transcranial and cortical strip electrodes to facilitate simultaneous monitoring of both upper and lower limbs at optimized stimulation intensities to increase IONM accuracy during motor area surgery. Ten nonconsecutive motor area tumors were studied. Good visualization of both limbs was observed in the series at a low amperage (1.2 mA from thestrip electrode and 165.3 mA from the transcranial electrode). Our analysis confirms concordance between the IONM data and postoperative outcomes. An MEP reduction >20% and >50% correlated with postoperative modified Rankin scale score changes without false-negative IONM findings. The technique was demonstrated to be accurate in providing a good simultaneous neurophysiological evaluation of both upper and lower limbs with an optimized and stimulation amplitude. The technique results in a low encumbrance of electrodes in the surgical field. Our results have confirmed the "proof of concept," its reliability and feasibility.

Prospective Validation of the Spinal Cord Shape Classification System in the Prediction of Intraoperative Neuromonitoring Data Loss: Assessing the Risk of Spinal Cord Data Loss During Spinal Deformity Correction.

The Spinal Cord Shape Classification System (SCSCS) class has been associated with spinal cord monitoring data loss during spinal deformity surgery. The objective of the current study was to prospectively validate the SCSCS as a predictor of spinal cord monitoring data loss during spinal deformity surgery. A prospective cohort study of consecutive patients who were undergoing primary deformity surgery at a single institution from 2018 to 2023 and whose major curve was in the spinal cord region was undertaken. Spinal cord morphology at the apex of the major curve on preoperative axial T2-weighted magnetic resonance imaging was used to categorize patients into 3 spinal cord shape types based on the SCSCS. The primary outcome was intraoperative neuromonitoring (IONM) data loss related to spinal cord dysfunction. Demographics and surgical and radiographic variables were compared between patients with IONM data loss and those without loss. Predictors of IONM loss were determined using bivariate and multivariable logistic regression analyses. A total of 256 patients (168 adult, 88 pediatric) were included and were separated into 3 SCSCS types: 110 (43.0%) with Type I, 105 (41.0%) with Type II, and 41 (16.0%) with Type III. IONM loss was observed in 30 (11.7%) of the 256 patients, including 7 (6.4%) of 110 with SCSCS Type I, 7 (6.7%) of 105 with Type II, and 16 (39.0%) of 41 with Type III. IONM loss was associated with SCSCS Type III, the preoperative deformity angular ratio, performance of 3-column osteotomies, greater operative time, greater transfusion volume, and greater postoperative sagittal corrections. SCSCS type was the strongest independent predictor of IONM data loss. SCSCS Type III had the greatest odds of IONM loss (odds ratio [OR] = 6.68, 95% confidence interval [CI] = 2.45 to 18.23 compared with Types I and II combined). The overall predictive performance with respect to IONM loss (area under the receiver operating characteristic curve = 0.827) was considered excellent. This prospective cohort study of patients undergoing spinal deformity correction confirmed that patients with a Type-III spinal cord shape had greater odds of IONM loss. Inclusion of the SCSCS in preoperative risk stratification and intraoperative management of spinal deformity corrective surgery is recommended. Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Electrophysiological monitoring of the nonrecurrent inferior laryngeal nerve and radiological evaluation of concurrent vascular anomalies.

The objective of this study was to characterize the electrophysiological characteristics of nonrecurrent inferior laryngeal nerves (NRILNs) that were dissected via intraoperative neuromonitoring (IONM) and concomitant vascular anomalies in patients with NRILNs. A retrospective analysis was conducted on 7865 patients who underwent thyroidectomy with IONM at three tertiary referral centers. The study included 42 patients in whom an NRILN was detected. IONM data and postoperative vocal cord (VC) examinations were recorded for all patients. The absence of an initial vagal EMG response and/or a short (<3.5 ms) latency period during the initial vagal stimulation or the inability to identify the RLN within the Beahrs triangle was considered highly suspicious for the presence of an NRILN. Postoperative cross-sectional imaging was performed in 36 out of 42 patients to assess any concurrent vascular anomalies. The prevalence of NRILN was 0.53%. An NRILN was suspected due to EMG findings in 32 (76%) patients and the inability to identify the RLN within the Beahrs triangle in the remaining 10 (24%) patients. The mean right VN latency period was 3.05 ± 0.15 ms. The V1 latency period of the right VN was shorter than 3.5 ms in 39 (93%) and longer than 3.5 ms in 3 (7%) patients. One of these three patients with latency>3.5ms had a large mediastinal goiter. Transient VC paralysis occurred in one (2.4%) patient. Of the 36 patients with postoperative imaging data, 33 (91.4%) had vascular anomalies. All 33 patients had aberrant right subclavian arteries, and 13 (39.4%) also had accompanying additional vascular anomalies. The NRILN is an anatomical variation that increases the risk of nerve injury. Observation of an absent EMG response and/or a short latency period during the initial vagal stimulation facilitates the detection of an NRILN at an early stage of thyroidectomy in the majority of patients.

Variability of somatosensory evoked potential and motor evoked potential change criteria in thoracic spinal decompression surgery based on preoperative motor status

Background contextCombined somatosensory- and motor-evoked potential (SSEP and MEP) changes for predicting prognosis in thoracic spinal surgery have been variably reported. PurposeWe aimed to explore the validity of combined SSEP and MEP for predicting postoperative motor deficits (PMDs) in thoracic spinal decompression surgery (TSDS) and identify a relatively optimal neurophysiological predictor of PMDs in patients based on preoperative motor status. Study settingRetrospective study. Patient sampleA total of 475 patients were analyzed. Outcome MeasuresA reduction in muscle strength by more than or equal to one manual muscle testing (MMT) grade postoperatively compared with the preoperative MMT grade was identified as PMDs. Postoperative motor deficits were detected by comparing the preoperative and postoperative physical examination findings in short- and long-term follow-up visits. MethodsAll patients were divided into two subgroups according to preoperative motor status. The following data were collected: (1) demographic data; (2) IONM (intraoperative neuromonitoring) data; and (3) postoperative motor outcomes. Binary logistic regression analysis was performed to assess the efficacy of IONM change to predict PMDs. A receiver operating characteristic curve (ROC) was used to establish optimal IONM warning criteria. ResultsNinety-eight patients had severe preoperative motor deficits (Group S), and 377 patients did not (Group N). MEP and SSEP change was effective for predicting PMDs in the short term (p<.01) and long term (p<.01) for TSDS patients. In Group N, the cutoff values for predicting PMDs in the short term were a decrease of 65% in SSEP amplitude and 89.5% in MEP amplitude of the baseline value. Furthermore, the cutoff values for predicting PMDs in the short term were durations of change of 24.5 minutes for SSEP and 32.5 minutes for MEP. In Group S, however, the cutoff values for predicting PMDs in the short term were a decrease of 36.5% in SSEP amplitude and 59.5% in MEP amplitude of the baseline value. Moreover, the critical values for predicting short-term PMDs were durations of change of 16.5 minutes for SSEP and 17.5 minutes for MEP. ConclusionsThe optimal IONM changes for prediction vary depending on preoperative motor status. Combined SSEP and MEP are excellent for predicting PMDs in TSDS.

Evaluation of intraoperative neuromonitoring (IONM) data with the Mainz IONM Quality Assurance and Analysis tool

Abstract Background Intraoperative neuromonitoring is widely used in thyroid and parathyroid surgery to prevent unilateral and especially bilateral recurrent nerve paresis. Reference values for amplitude and latency for the recurrent laryngeal nerve and vagus nerve have been published. However, data quality measures that exclude errors of the underlying intraoperative neuromonitoring (IONM) data (immanent software errors, false data labelling) before statistical analysis have not yet been implemented. Methods The authors developed an easy-to-use application (the Mainz IONM Quality Assurance and Analysis tool) using the programming language R. This tool allows visualization, automated and manual correction, and statistical analysis of complete raw data sets (electromyogram signals of all stimulations) from intermittent and continuous neuromonitoring in thyroid and parathyroid surgery. The Mainz IONM Quality Assurance and Analysis tool was used to evaluate IONM data generated and exported from ‘C2’ and ‘C2 Xplore’ neuromonitoring devices (inomed Medizintechnik GmbH) after surgery. For the first time, reference values for latency and amplitude were calculated based on ‘cleaned’ IONM data. Results Intraoperative neuromonitoring data files of 1935 patients consecutively operated on from June 2014 to May 2020 were included. Of 1921 readable files, 34 were excluded for missing data labelling. Automated plausibility checks revealed: less than 3 per cent device errors for electromyogram signal detection; 1138 files (approximately 60 per cent) contained potential labelling errors or inconsistencies necessitating manual review; and 915 files (48.5 per cent) were indeed erroneous. Mean(s.d.) reference onset latencies for the left vagus nerve, right vagus nerve, recurrent laryngeal nerve, and external branch of the superior laryngeal nerve were 6.8(1.1), 4.2(0.8), 2.5(1.1), and 2.1(0.5) ms, respectively. Conclusion Due to high error frequencies, IONM data should undergo in-depth review and multi-step cleaning processes before analysis to standardize scientific reporting. Device software calculates latencies differently; therefore reference values are device-specific (latency) and/or set-up-specific (amplitude). Novel C2-specific reference values for latency and amplitude deviate considerably from published values.

Intraoperative Neuromonitoring during Peripheral Arteriovenous Malformation Embolization

PurposeTo evaluate whether intraoperative neuromonitoring (IONM), including pre-embolization lidocaine injection challenge (“provocative testing”) is associated with reduced risk of irreversible nerve injury during embolization of peripheral arteriovenous malformations (AVMs). Materials and MethodsMedical records of patients with peripheral AVMs who underwent embolotherapy with IONM with provocative testing between 2012 and 2021 were reviewed retrospectively. Data collected included patient demographic characteristics, AVM location and size, embolic agent used, IONM signal changes after lidocaine and embolic agent injections, postprocedural adverse events, and clinical outcomes. Decisions regarding whether embolization would proceed at specific locations were based on IONM findings after the lidocaine challenge and as embolization proceeded. ResultsA cohort of 17 patients (mean age, 27 years ± 19; 5 women) who underwent 59 image-guided embolization procedures with adequate IONM data was identified. No permanent neurologic deficits occurred. Transient neurologic deficits were observed in 3 patients (4 sessions), comprising skin numbness (2 patients), extremity weakness (1 patient), and extremity weakness and numbness (1 patient). All neurologic deficits resolved by postoperative day 4 without additional treatment. ConclusionsIONM, including provocative testing, during AVM embolization may minimize potential nerve injury.

Upper extremity neuromonitoring changes are more common than lower extremity during spinal fusion for Scheuermann's kyphosis.

The purpose of this study is to determine the incidence of intraoperative neuromonitoring (IONM) changes and postoperative neurologic deficit in patients with Scheuermann's Kyphosis (SK) undergoing posterior spinal fusion (PSF). Single-center, retrospective chart review of the clinical, surgical and IONM data (somatosensory evoked potential (SSEP) and neurogenic motor evoked potential (NMEP) or transcranial motor evoked potential (TcMEP)) from patients with SK undergoing PSF at our center from 1993 to 2021. One hundred and four SK patients (mean 16.4 ± 1.9years) underwent PSF with correction of kyphosis from mean 79.4 ± 10.8° to 35.4 ± 13.9°. MEP data were obtained using either NMEP in 34.6% of patients) or TcMEP in 65.4% of patients. Only 3.8% of cases had lower extremity (LE) IONM changes during surgery, with no postoperative neurologic deficits in those patients. IONM changes occurred more frequently in the upper extremities (UE) with 14 (13.4%) patients having changes in UE SSEPs. Patients with UE IONM changes had significantly longer surgical times (p = 0.0096) and higher number of levels fused (p = 0.003) compared to patients without changes. Their weight, but not BMI, was also significantly higher (p = 0.036). These UE IONM changes resolved with arm repositioning in all but one patient who had a postoperative UE neurapraxia that resolved by 6weeks. There was 1 postoperative transient femoral nerve palsy without IONM changes thought to be due to patient positioning. The incidence of critical LE IONM changes during PSF for SK is 3.4%, which is similar to that reported in AIS. UE IONM changes are significantly more common at 13.4%, revealing that these patients are vulnerable to malpositioning of the arms during surgery.

Intraoperative neuromonitoring for pediatric Chiari decompression: when is it useful?

Surgical treatment for symptomatic Chiari I malformation involves surgical decompression of the craniovertebral junction. Given the proximity of critical brainstem structures, intraoperative neuromonitoring (IONM) is employed for safe decompression in some institutions. However, IONM adds time and cost to the operation, and the benefit to the patient has not been defined. Given the diversity in surgical practices, there is no evidence-based standard of care regarding when to use IONM and which modalities are most helpful. The purpose of this study was to review a single-surgeon experience with IONM in order to determine the sensitivity, specificity, and predictive values of various IONM modalities routinely used in pediatric Chiari I decompression; to examine the associations between patient, clinical, and radiographic characteristics and IONM alerts; and to obtain data regarding the usefulness of these modalities during the surgical process to improve patient outcomes. A retrospective review was performed for 300 consecutive pediatric patients who underwent suboccipital craniectomy and C1 laminectomy for Chiari decompression performed by a single surgeon over a 15-year period. Clinical, radiographic, and IONM data were collected. Radiographic measurements of the skull base morphological abnormalities, including clival angle, Chamberlain's line, and Grabb-Oakes line, were compared between patients with and without true IONM signal changes. A total of 291 cases were included, with an age range of 6 months to 19 years. Among 291 cases, somatosensory evoked potentials (SSEPs) were monitored in 291, motor evoked potentials (MEPs) in 209, cranial nerve spontaneous electromyography (sEMG) in 290, and brainstem auditory evoked potentials (BAEPs) in 110. Sensitivity, specificity, positive predictive value, and negative predictive value, respectively, were as follows: 1.00, 1.00, 1.00, and 1.00 for SSEPs; 1.00, 0.99, 0.67, and 1.00 for MEPs; 0.00, 0.88, 0.00, and 1.00 for sEMG; and not appliable, 1.00, not applicable, and 1.00 for BAEPs. Six patients had true IONM signal changes. These patients had radiographic evidence of more severe concomitant craniocervical instability and basilar invagination, with steeper clival angles (124° vs 146°, p = 0.02) and larger Grabb-Oakes lines (10.1 mm vs 6.7 mm, p = 0.02), when compared with the patients without any true IONM changes. Intraoperative neuromonitoring may be best utilized for patients who show radiographic features of abnormal skull base morphology, defined as a clival angle < 135° or Grabb-Oakes line > 9 mm. When IONM is employed, SSEP and MEP monitoring are the most useful modalities.

Is There Any Reliable Predictor of Functional Recovery Following Post-thyroidectomy Vocal Fold Paralysis?

Predicting definitive outcomes of post-thyroidectomy vocal fold paralysis (VFP) is challenging. We aimed to identify reliable predictors based on intraoperative neuromonitoring (IONM) and flexible fiberoptic laryngostroboscopy (FFL) findings. Among 1172 thyroid operations performed from April to December 2021, all patients who exhibited vocal fold paralysis (VFP) at post-operative laryngoscopy were included. IONM data, including type of loss of signal (LOS), were collected. Patients underwent FFL, with arytenoid motility assessment, at 15, 45 and 120days post-operatively. Patients were divided into two groups: those who recovered vocal fold motility (VFM) by the 120th post-operative day (recovery group) and those who did not (non-recovery group). Fifty-nine VFP cases (5.0% of total patients) met the inclusion criteria. Eight patients were lost at follow-up and were excluded. Overall, 9 patients were included in the non-recovery group (0.8% of total patients) and 42 in the recovery group. Among various predictive factors, only arytenoid fixation (AF) at the 15th post-operative day and Type I LOS were significant predictors for no VFM recovery (p = 0.007, RR = 9.739, CI:1.3-72.3 and p = 0.001, RR = 9.25, CI:2.2-39.3 for AF and Type I injury, respectively). The combination of type of LOS and arytenoid motility at the 15th post-op day yielded satisfactory predictive values for the progression of transient VFP to permanent. Arytenoid motility at the 15th post-op day and type II LOS are associated with recovery of VFM. Type of LOS and FFL could be included in the follow-up protocols of patients with VFP to reliably predict clinical outcomes.

Utilization of intraoperative neuromonitoring during the Woodward procedure for treatment of Sprengel deformity.

Brachial plexus injury (BPI) leading to palsy of the upper extremities is the most serious complication of the Woodward procedure for treatment of Sprengel deformity. Intraoperative neuromonitoring (IONM) is widely used for detecting emerging spinal cord or peripheral nerve injury during spinal and shoulder surgery. However, to date, its utilization in pediatric patients with Sprengel deformity is limited. Furthermore, it remains unclear whether IONM can help prevent BPI during surgery. The purpose of the current study was to assess the feasibility and effectiveness of IONM for early identification and prevention of nerve injury during the Woodward procedure. We retrospectively reviewed the records of patients who underwent the Woodward procedure for Sprengel deformity at our institution between January 2017 and January 2020. IONM, including somatosensory evoked potentials (SEP) and motor evoked potentials (MEPs), was performed in all patients. Detailed IONM data were collected and analyzed. Preoperative and postoperative cosmetic appearance (according to the Cavendish classification), shoulder joint abduction function, and radiologic evaluation of the scapula were reviewed. Surgical complications were recorded. Forty-six patients (19 girls, 27 boys) were included (mean age, 5.1±2.1 years). Both SEP and MEP (amplitude of the abductor pollicis) were successfully performed (100%). MEP alerts occurred in 3 patients (6.5%). After scapula position adjustment, signals recovered in 2 patients and remained unchanged in 1 patient-this patient exhibited postoperative motor deficits that resolved completely by 4 months recovery. The SEP amplitudes decreased in all 3 patients but did not reach the warning criteria. Forty patients were classified as grade III and 6 as grade IV in the Cavendish classification, whereas 35 patients were classified as grade II and 11 as grade III in the Rigault scale. The preoperative Cavendish grade was III (III, IV) and the postoperative Cavendish grade was I (I, II) (χ2=88.098, P<.001). The preoperative Rigault grade was II (II, III) and the postoperative Rigault grade was I (I, II) (χ2=62.133, P<.001). The mean arc of shoulder joint abduction improved from 99°±8° to 167°±7° (t=-45.871, P<.001) after surgery. Except for temporary motor deficits detected in 1 patient, no other postoperative complications were observed through the time of final follow-up. IONM during the Woodward procedure for Sprengel deformity is feasible and effective in detecting intraoperative neurologic changes and may be effective in preventing BPI associated with surgery.

The Role of Intraoperative Neuromonitoring Modalities in Anterior Cervical Spine Surgery.

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

A Loading Dose of Dexmedetomidine With Constant Infusion Inhibits Intraoperative Neuromonitoring During Thoracic Spinal Decompression Surgery: A Randomized Prospective Study.

Background: The effect of a bolus dose of dexmedetomidine on intraoperative neuromonitoring (IONM) parameters during spinal surgeries has been variably reported and remains a debated topic. Methods: A randomized, double-blinded, placebo-controlled study was performed to assess the effect of dexmedetomidine (1 μg/kg in 10 min) followed by a constant infusion rate on IONM during thoracic spinal decompression surgery (TSDS). A total of 165 patients were enrolled and randomized into three groups. One group received propofol- and remifentanil-based total intravenous anesthesia (TIVA) (T group), one group received TIVA combined with dexmedetomidine at a constant infusion rate (0.5 μg kg−1 h−1) (D1 group), and one group received TIVA combined with dexmedetomidine delivered in a loading dose (1 μg kg−1 in 10 min) followed by a constant infusion rate (0.5 μg kg−1 h−1) (D2 group). The IONM data recorded before test drug administration was defined as the baseline value. We aimed at comparing the parameters of IONM. Results: In the D2 group, within-group analysis showed suppressive effects on IONM parameters compared with baseline value after a bolus dose of dexmedetomidine. Furthermore, the D2 group also showed inhibitory effects on IONM recordings compared with both the D1 group and the T group, including a statistically significant decrease in SSEP amplitude and MEP amplitude, and an increase in SSEP latency. No significance was found in IONM parameters between the T group and the D1 group. Conclusion: Dexmedetomidine delivered in a loading dose can significantly inhibit IONM parameters in TSDS. Special attention should be paid to the timing of a bolus dose of dexmedetomidine under IONM. However, dexmedetomidine delivered at a constant speed does not exert inhibitory effects on IONM data.

HP33: A global survey of intraoperative monitoring: Needs and availability

Introduction: Results from a multi-factorial global survey regarding the awareness of, need for, and availability of Intraoperative Neurophysiological monitoring in a cross-section of populations and socio-economic conditions will be presented. A statistical analysis of the responses will be given. Conclusions from these data will be discussed. Intraoperative Neuromonitoring (IOM) is a proven technology for reducing iatrogenic sequelae and improving patient outcomes. Unfortunately, its availability is not universal, leaving many populations without access to this beneficial service. In order to target IOM resources most efficiently, thereby maximizing its availability to under-served patients, an understanding of the current state of IOM delivery in the global market is necessary. To establish a representative “cross-section” of respondents, we surveyed 12 countries across North and South America, Africa, Europe, and Asia. Respondents included surgeons, neurologists and clinical neurophysiologists. Of primary interest in the Survey was the demand for IOM, and the availability of trained Neurophysiology clinicians to meet that demand. Other critical factors examined included surgeon awareness of IOM, non-standardized delivery models, the relative paucity of education curricula or training resources for the IOM clinician, real-time physician oversight for the interpretation of the IOM data, and budgetary constraints related to reimbursement and capital equipment purchases. We are able to draw several conclusions from this survey. Demand for IOM far exceeds the available trained clinical staff, particularly in emerging economic regions. Increasing surgeon advocacy through awareness and education will drive improved opportunities to deliver this critical patient care.

The Effect of Patient Positioning on Intraoperative Neuromonitoring During Thyroid and Parathyroid Surgery.

Intraoperative neuromonitoring (IONM) has been accepted as a routine adjunct among surgeons who perform thyroid and parathyroid surgeries. Thyroid and parathyroid surgeries use various patient positioning strategies that have poorly understood effects on IONM. The aim of this study was to compare IONM signals between the transaxillary and transcervical approaches. In this retrospective cohort study, we evaluated 463 adult patients who underwent a total of 502 procedures. The procedures performed included total thyroidectomy, right or left hemithyroidectomy, and parathyroidectomy. Vagus nerve and recurrent laryngeal nerve (RLN) latency and amplitude measurements were analyzed intra-operatively. The distances between the vagus nerve and the trachea were measured via ultrasound during transaxillary procedures. Compared to the transcervical approach, the right vagus nerve latency was significantly decreased in the transaxillary approach. Transaxillary surgery was not associated with increased latency or decreased amplitude on IONM. The distance between the vagus nerve and trachea was significantly decreased post-positioning during transaxillary approaches. Despite differences in patient positioning, a transaxillary approach was not associated with increased stress on the vagus nerve or RLN, according to IONM data. The decreased right vagus nerve latency associated with a transaxillary approach highlights the importance of considering patient positioning and laterality while interpreting IONM data.

Resection of congenital hemivertebra in pediatric scoliosis: the experience of a two-specialty surgical team.

Institutions investigating value and quality emphasize utilization of two attending surgeons with different areas of technical expertise to treat complex surgical cases and to minimize complications. Here, the authors chronicle the 12-year experience of using a two-attending surgeon, two-specialty model to perform hemivertebra resection in the pediatric population. Retrospective cohort data from 2008 to 2019 were obtained from the NewYork-Presbyterian Morgan Stanley Children's Hospital operative database. This database included all consecutive pediatric patients < 21 years old who underwent hemivertebra resection performed with the two-attending surgeon (neurosurgeon and orthopedic surgeon) model. Demographic information was extracted. Intraoperative complications, including durotomy and direct neurological injury, were queried from the clinical records. Intraoperative neuromonitoring data were evaluated. Postoperative complications were queried, and length of follow-up was determined from the clinical records. From 2008 to 2019, 22 patients with a median (range) age of 9.1 (2.0-19.3) years underwent hemivertebra resection with the two-attending surgeon, two-specialty model. The median (range) number of levels fused was 2 (0-16). The mean (range) operative time was 5 hours and 14 minutes (2 hours and 59 minutes to 8 hours and 30 minutes), and the median (range) estimated blood loss was 325 (80-2700) ml. Navigation was used in 14% (n = 3) of patients. Neither Gardner-Wells tongs nor halo traction was used in any operation. Neuromonitoring signals significantly decreased or were lost in 14% (n = 3) of patients. At a mean ± SD (range) follow-up of 4.6 ± 3.4 (1.0-11.6) years, 31% (n = 7) of patients had a postoperative complication, including 2 instances of proximal junctional kyphosis, 2 instances of distal junctional kyphosis, 2 wound complications, 1 instance of pseudoarthrosis with hardware failure, and 1 instance of screw pullout. The return to the operating room (OR) rate was 27% (n = 6), which included patients with the abovementioned wound complications, distal junctional kyphosis, pseudoarthrosis, and screw pullout, as well as a patient who required spinal fusion after loss of motor evoked potentials during index surgery. Twenty-two patients underwent hemivertebra resection with a two-attending surgeon, two-specialty model over a 12-year period at a specialized children's hospital, with a 14% rate of change in neuromonitoring, 32% rate of nonneurological complications, and a 27% rate of unplanned return to the OR.

Prognostication of the neurological outcome of tethered cord based on intraoperative neuromonitoring findings: how close can we get?

Purpose To evaluate the correlation of intraoperative neuromonitoring (IONM) data in surgery for tethered cord syndrome (TCS) in children to the neurological outcome at 1-year follow-up. Methods 208 consecutive patients operated on for TCS, between January 2011 to February 2020, under electrophysiological monitoring in the Division of Paediatric Neurosurgery, AIMS, Kochi, India, were included. Their preoperative neurological, urological and orthopaedic status were compared with the postoperative status at 1 year follow-up. Results Our study prospectively collected the IONM data and retrospectively correlated it to the children's neurological outcome on follow-up. Out of 208 children, 28% (n = 59/208) had motor, 35% (n = 73/208) had bladder and 26% (n = 54/208) had bowel disturbances. Postsurgery, at one-year follow-up, 91% (n = 52/57) of the patients who had motor deficits had improvement, 82.3% (n = 51/62) of patients who had bladder deficits showed an improvement, and 88.8% (n = 48/54) with bowel deficits showed improvement. The monitorability for motor and sphincter potentials were 99.4% and 89.3%, respectively. Except for four patients (3 with bladder and 1 with motor worsening), all the patients who were monitorable with no deficits remained intact except for four patients, all the patients who had deficits and were monitorable improved after detethering (at 1 year). Clinical worsening corresponded to those who had a drop in amplitude of baseline TcMEP (n = 4). 18 events showed an increase in amplitude compared to the baseline TcMEP. These patients improved clinically on follow-up (at 1 year). Conclusions IONM complements the preoperative clinical details in predicting immediate and long-term outcomes.