Intraoperative Neuromonitoring Alerts Research Articles

The Management of Intraoperative Spinal Cord Injury - A Scoping Review.

Scoping Review. To review the literature and summarize information on checklists and algorithms for responding to intraoperative neuromonitoring (IONM) alerts and management of intraoperative spinal cord injuries (ISCIs). MEDLINE® was searched from inception through January 26, 2022 as were sources of grey literature. We attempted to obtain guidelines and/or consensus statements from the following sources: American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM), American Academy of Neurology (AAN), American Clinical Neurophysiology Society, NASS (North American Spine Society), and other spine surgery organizations. Of 16 studies reporting on management strategies for ISCIs, two were publications of consensus meetings which were conducted according to the Delphi method and eight were retrospective cohort studies. The remaining six studies were narrative reviews that proposed intraoperative checklists and management strategies for IONM alerts. Of note, 56% of included studies focused only on patients undergoing spinal deformity surgery. Intraoperative considerations and measures taken in the event of an ISCI are divided and reported in three categories of i) Anesthesiologic, ii) Neurophysiological/Technical, and iii) Surgical management strategies. There is a paucity of literature on comparative effectiveness and harms of management strategies in response to an IONM alert and possible ISCI. There is a pressing need to develop a standardized checklist and care pathway to avoid and minimize the risk of postoperative neurologic sequelae.

Does Spinal Cord Type Predict Intraoperative Neuro-Monitoring Alerts in Scoliosis Correction Surgery? A Systematic Review and Meta-Analysis of Operative and Radiologic Predictors.

Systematic literature review and meta-analysis. Predicting patient risk of intraoperative neuromonitoring (IONM) alerts preoperatively can aid patient counselling and surgical planning. Sielatycki et al established an axial-MRI-based spinal cord classification system to predict risk of IONM alerts in scoliosis correction surgery. We aim to systematically review the literature on operative and radiologic factors associated with IONM alerts, including a novel spinal cord classification. A systematic review and meta-analysis was performed as per the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) Guidelines. A literature search identifying all observational studies comparing patients with and without IONM alerts was conducted. Suitable studies were included. Patient demographics, radiological measures and operative factors were collected. 11 studies were included including 3040 patients. Relative to type 3 cords, type 1 (OR = .03, CI = .01-.08, P < .00001), type 2 (OR = .08, CI = .03, P <.00001) and all non-type 3 cords (OR = .05, CI = .02-.16, P < .00001) were associated with significantly lower odds of IONM alerts. Significant radiographic measures for IONM alerts included coronal Cobb angle (MD = 10.66, CI = 5.77-15.56, P < .00001), sagittal Cobb angle (MD = 9.27, CI = 3.28-14.73, P = .0009), sagittal deformity angle ratio (SDAR) (MD = 2.76, CI = 1.57-3.96, P < .00001) and total deformity angle ratio (TDAR) (MD = 3.44, CI = 2.27-4.462, P < .00001). Clinically, estimated blood loss (MD = 274.13, CI = -240.03-788.28, P = .30), operation duration (MD = 50.79, CI = 20.58-81.00, P = .0010), number of levels fused (MD = .92, CI = .43-1.41, P = .0002) and number of vertebral levels resected (MD = .43, CI = .01-.84, P = .05) were significantly greater in IONM alert patients. This study highlights the relationship of operative and radiologic factors with IONM alerts.

Diagnostic accuracy of intraoperative neuromonitoring in transcarotid artery revascularization

BackgroundIn recent years, transcarotid artery revascularization (TCAR) has emerged as a safe and effective alternative to carotid artery stenting. While intraoperative neuromonitoring (IONM) techniques such as electroencephalogram (EEG) and somatosensory...

Incidence of postoperative neurological deficit with the use of an intraoperative neuromonitoring protocol for lateral lumbar interbody fusion.

Intraoperative neuromonitoring (IONM) has become commonplace in assessing neurological integrity during lateral approaches to lumbar interbody fusion surgeries. Neuromonitoring is designed to aid surgeons in identifying the potential for intraoperative nerve injury and reducing associated postoperative complications. However, standardized protocols for neuromonitoring have not been provided, and outcomes are not well described. The purpose of this study was to provide a standardized protocol for IONM, and to describe clinical outcomes in a cohort of individuals who underwent lateral lumbar interbody fusion (LLIF) surgery. A retrospective review of 169 consecutive patients who underwent LLIF surgery at a single institution from October 2014 to October 2016 was performed. Patient characteristics, intraoperative details, clinical outcomes, and postoperative deficits (PODs) were compared between patients who did and did not trigger IONM alerts, and between patients who did and did not demonstrate a POD. A protocol for IONM decision-making was generated based on these observations. Most patients (91.7%) underwent surgery for a degenerative spine condition. Twenty-three patients (13.6%) triggered neuromonitoring alerts, and 16 patients (9.5%) demonstrated a POD. Leg pain, back pain, and disability improved significantly (p < 0.045), and 2 patients had both motor and sensory deficits at the 12-week postoperative time point. Patients with a POD demonstrated greater operating room time (p = 0.034) and a greater number of interbody fusion levels (p = 0.015) but were less likely to have triggered a neuromonitoring alert (p = 0.04). There was no association between retractor time and POD (p = 0.98). When an IONM protocol was followed, individuals who experienced a POD were less likely to trigger an alert than those who did not experience a POD (p = 0.04). This study provides a protocol algorithm for IONM alert responses in patients undergoing LLIF surgery. PODs are most associated with multilevel fusion, and patients with alerts had a low rate of persistent deficit. Future research is needed to validate these findings using a more rigorous comparative study design.

Utilization of pre-operative MRI to identify AIS patients at highest risk of intra-operative neuromonitoring alert.

Utility of pre-operative MRI for patients undergoing scoliosis correction has expanded to include an MRI classification for identifying patients at increased risk of experiencing intra-operative neuromonitoring (IONM) alerts based on the shape of the spinal cord and circumferential presence of CSF at the apex of the thoracic curve. In the present study, the authors explore the utility of this new MRI classification and multiple X-ray radiographic parameters in identifying the AIS sub-population at high risk of IONM alerts. AIS patients < 18years old who underwent posterior spinal fusion between 2018 and 2022 at a single institution. Imaging reviewed to determine main thoracic (MT) and thoraco-lumbar (TL) Cobb angles, major thoracic Apical Vertebral Translation (AVT) and lumbar/thoraco-lumbar AVT (TL AVT), thoracic kyphosis (TK), coronal main thoracic Deformity Angular Ratio (cDAR), sagittal DAR (sDAR), and MRI to determine the spinal cord type (1, 2, or 3). A total of 155 AIS patients who met the inclusion criteria between 2018 and 2022 were included. There was a trend to have an increased incidence of Type 3 spinal cord shape both with increase in the MT Cobb angle and MT AVT. There was also a shift toward more IONM alerts in patients with Type 3 (19.5%) spinal cords, AVT ≥ 5cm (18.9%), and Cobb angle ≥ 650 (28.2%). Higher magnitude of thoracic Cobb angle and AVT are associated with higher likelihood of type 3 spinal cord at the apex in MRI. Patients with Type 3 spinal cord, Cobb angle ≥ 650, AVT > 5cm, and cDAR > 10 have higher likelihood to have IONM alerts. Patient with a Type 3 spinal cord and a Cobb angle ≥ 650 (50.0%), cDAR > 10 (43.7%), and AVT > 5cm (35.2%) have the highest risk of having IONM alerts.

Treatment of Chiari Malformation and Concomitant Paediatric Scoliosis Long-Term Follow-Up in One Major Referral Centre in the UK.

Paediatric scoliosis (PS) and Chiari malformation type 1 (CM-1) have been reported to be associated with each other. Scoliosis curvature is a common finding among patients operated for CM-1, and curve development has been related to it. We report a cohort of PS and CM-1 patients managed with posterior fossa and upper cervical decompression (PFUCD) by a single surgeon, with an average of two years of follow-up. We present a retrospective cohort in a single referral centre for patients with CM-1 and PS. From 2011 to 2018, we identified fifteen patients with CM-1 and PS; eleven underwent PFUCD, ten had symptomatic CM-1, and one had asymptomatic CM-1 but showed curve progression. The remaining four CM-1 patients were asymptomatic and were hence treated conservatively. The average follow-up post-PFUCD was 26.2 months. Scoliosis surgery was performed in seven cases; six patients underwent PFUCD prior to the scoliosis correction. One scoliosis case underwent surgery in the presence of mild CM-1 treated conservatively. The remaining four cases were scheduled for scoliosis correction surgery, while three were managed conservatively, with one case lost to follow-up. The average time between PFUCD and scoliosis surgery was 11 months. None of the cases had intraoperative neuromonitoring alerts or perioperative neurological complications. CM-1 with concomitant scoliosis can be found. Symptomatic CM-1 might require surgery, but as we discovered, PFUCD had negligible effect on curve progression and the future need for scoliosis surgery.

Linking Patterns of Intraoperative Neuromonitoring (IONM) Alerts to the Odds of a New Postoperative Neurological Deficit: Analysis of 27,808 Cervical Spine Procedures From a National Multi-institutional Database.

Retrospective review of a national multi-institutional database of 27,808 extradural cervical spine procedures performed between January 2017 and May 2021. Characterize intraoperative neuromonitoring alerts by the patterns of modalities and nerves/muscles involved and quantify risk of new-onset neurological deficit for patients with a primary diagnosis of myelopathy, stenosis, or radiculopathy. Phenotyping alert patterns and linking those patterns with risk is needed to facilitate clinical decision-making. Cases with alerts were categorized by patterns of modalities or nerves/muscles involved, and alert status at closure. Unadjusted odds ratios (ORs) for new-onset neurological deficit were calculated. A mixed-effects logistic regression model controlling for demographic and operative factors, with random intercepts to account for clustering in outcomes by surgeon and surgical neurophysiologist was also used to calculate ORs and probabilities of neurological deficit. There was significantly increased risk of a new neurological deficit for procedures involving posterior compared with anterior approaches (OR: 1.82, P=0.001) and procedures involving three levels compared with one (OR: 2.17, P=0.001). Odds of a deficit were lower for patients with radiculopathy compared with myelopathy (OR: 0.69, P=0.058). Compared with cases with no alerts, those with unresolved Spinal Cord alerts were associated with the greatest elevation in risk (OR: 289.05) followed by unresolved C5-6 Nerve Root (OR: 172.7), C5-T1 Nerve Root/Arm (OR: 162.89), C7 Nerve Root (OR:84.2), and C8-T1 Nerve Root alerts (OR:75.49, all P<0.001). Significant reductions in risk were seen for resolved Spinal Cord, C5-6 Nerve Root, and C8-T1 nerve alerts. Overall, unresolved motor evoked potential and somatosensory evoked potential alerts were associated with the greatest elevation in risk (OR:340.92) followed by unresolved motor evoked potential-only (OR:140.6) and unresolved somatosensory evoked potential-Only alerts (OR:78.3, all P<0.001). These relationships were similar across diagnostic cohorts. Risk elevation and risk mitigation after an intraoperative neuromonitoring alert during surgery is dependent on the type and pattern of alert.

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.

Ponte osteotomies increase risk of intraoperative neuromonitoring alerts in adolescent idiopathic scoliosis surgery.

Background: Ponte osteotomies (PO) are commonly used in adolescent idiopathic scoliosis (AIS) surgeries to improve the coronal and sagittal deformity correction. Here, we compared the incidence of perioperative neurologic complications for patients undergoing AIS with versus without PO.Methods: In a retrospective cohort study of 80 consecutive AIS patients undergoing scoliosis correction, 40 underwent PO, while 40 did not. All operations were performed by one surgeon at one tertiary care center. Patients’ demographics, Lenke classifications, surgical data, and deformity characteristics were comparable in both groups. Perioperative neurologic complications, defined as spinal cord or nerve root injuries identified by the surgeon, were tracked for those undergoing AIS surgery with or without PO being performed.Results: The risk of IOM alerts was significantly higher in the PO patients (12.5%: 5 patients) versus those in the No-PO group (0%, P = 0.021). Despite these changes, no patient incurred an increased postoperative deficit. Nevertheless, PO group patients demonstrated a higher coronal deformity correction rate (PO: 71% ± 10.9 vs. NoPO: 64.2% ± 11.5, P = 0.008) and a greater kyphosis Cobb angle (PO: 25.2 ± 6 vs. No-PO: 17.5 ± 9.4, P = 0.0001) on postoperative follow-up.Conclusion: While PO improved 3D correction of AIS, it increased the risk of IOM alerts in 12.5% of cases.

Neuromonitoring for Proximal Fibular Osteochondroma Excision.

The peroneal nerve is at risk when excising tumors in the proximal fibula. The rate of nerve injuries during proximal fibular tumor resection varies from 3% to 20%. Our goal was to report our experience with resection of osteochondromas in the proximal fibula and describe the technique and utility of neuromonitoring during excision of proximal fibular osteochondromas (PFO). Patients with a diagnosis of symptomatic PFO who had undergone excision at one institution from 1994 to 2018 were included. An institutional review board-approved retrospective review was performed. Intraoperative neuromonitoring was provided from 2006 on by a single group utilizing a multimodality protocol. This study contains 29 patients who had excision of osteochondromas in the proximal fibula. Of these 29 consecutively monitored patients, there were 34 involved extremities. Intraoperative neuromonitoring alerts occurred in 10/29 (34.5%) procedures, which included 3 electromyography (EMG) (30%), 2 motor-evoked potential (20%), 1 somatosensory-evoked potential (10%), and 4 alerts with a combination of EMG/motor-evoked potential/somatosensory-evoked potential changes (40%). The interventions that were taken resulted in resolution of the neuromonitoring changes in all procedures. Postoperatively, we noted 2 (6.9%) new mild sensory deficits, which resolved during follow up. There were 3 patients in whom pre-existing sensory-motor deficits improved but not completely after surgery, 1 motor weakness, and 2 with residual paresthesia. In those initially presenting with paresis, there was improvement in 8 of the 8 extremities by the last follow-up visit. Pain as a symptom was resolved in all cases. There were no iatrogenic foot drop injuries. The average follow up was 32.2 months. Neuromonitoring during PFO excision demonstrated a high number of alerts, all of which resolved following timely corrective action. The use of neuromonitoring may help decrease the risk of iatrogenic postoperative neurological deficits following fibular osteochondroma surgery. Level IV.

Amplitude-reduction alert criteria and intervention during complex paediatric cervical spine surgery

ObjectiveTo determine the utility of widely used intraoperative neuromonitoring (IONM) alert criteria and intervention for predicting postoperative outcome following paediatric spinal surgery. MethodsRetrospective analysis of somatosensory evoked potentials (SSEP) and motor evoked potentials (MEP) in consecutive cervical spine fixations. An intervention protocol followed amplitude-reductions in SSEPs (≥50 %) and/or MEPs (≥80 %). Alert breaches were reversed when SSEP/MEP amplitude was restored to > 50 %/20 % of baseline. Sensorimotor function was assessed preoperatively and 3-months postoperatively via the Modified McCormick Scale score (MMS). We explored associations between postoperative outcome, demographic/surgical and IONM variables. ResultsForty-five procedures in 38 children (mean age:9 ± 4 years;55 % female) were monitored, 42 %of which breached alert criteria. Instrumentation (6/19,32 %) and hypotension (5/19,26 %) were common causes for alert and the majority (13/19,68 %) were reversed following intervention. There was an association between pre- and post-MMS and the type of breach (p = 0.002). All children with worse postoperative MMS (3/38,8%) had irreversible breaches. ConclusionsIONM in this small sample accurately detected neurological injury. The majority of breaches reversed following an intervention protocol. Irreversible breaches frequently led to worse postoperative sensorimotor function. SignificanceAn intervention protocol which reversed IONM alerts never resulted in postoperative worsening of sensorimotor function.

Combined Motor and Sensory Intraoperative Neuromonitoring for Cervical Spondylotic Myelopathy Surgery Causes Confusion: A Level-1 Diagnostic Study.

Level-1 diagnostic study. The purpose of this study was to evaluate the sensitivity and specificity of combined motor and sensory intraoperative neuromonitoring (IONM) for cervical spondylotic myelopathy (CSM). Intraoperative neuromonitoring during spine surgery began with sensory modalities with the goal of reducing neurological complications. Motor monitoring was later added and purported to further increase sensitivity and specificity when used in concert with sensory monitoring. Debate continues, however, as to whether neuromonitoring reliably detects reversible neurologic changes during surgery or simply adds set-up time, cost, or mere medicolegal reassurance. Neuromonitoring data using combined motor and sensory evoked potentials for 540 patients with CSM undergoing anterior or posterior decompressive surgery were collected prospectively. Patients were examined postoperatively to determine the clinical occurrence of new neurologic deficit which correlated with monitoring alerts recorded per established standard criteria. The overall incidence of positive IONM alerts was 1.3% (N = 7) all of which were motor alerts. All were false positives as no patient had clinical neurological deterioration post-operatively. The false-positive rate was 1.4% (N = 146) for anterior surgeries and 1.3% (N = 394) for posteriors with no statistical difference between them (P = 1.0, Fisher exact test). There were no false-negative alerts, and all negatives were true negatives (N = 533). The overall sensitivity of detecting a new neurologic deficit was 0%, overall specificity 98.7%. Combined motor and sensory neuromonitoring for CSM patients created a confusing choice between the motor or sensory data when in disagreement in 1.3% of surgical patients. Criterion standard clinical examinations confirmed all motor alerts were false positives. Surgical plan was negatively altered by following false motor alerts early on, but disregarded in later cases in favor of sensory data. Neuromonitoring added set-up time and cost, but without clear benefit in this series.Level of Evidence: 4.

240. Utility of intraoperative neuromonitoring alerts relating to adverse outcomes in spine surgery: a study of 289 patients

<h3>BACKGROUND CONTEXT</h3> Although rare, one of the most problematic complications during spine surgery is neurologic injury with subsequent deficit. The use of multimodal intraoperative neuromonitoring (MIOM) during spine surgery provides the surgical team with real-time assessment of the neurological physiology and function. MIOM is thought to be sensitive and specific for identifying perioperative neurological injury in spinal surgery especially deformity surgery. However, results from recent studies have cast doubt on the effectiveness of certain MIOM techniques in detecting neurological injury in spine surgery patients. <h3>PURPOSE</h3> The purpose of this study was to improve spine surgery patient safety and outcomes by minimizing the incidence of postoperative new neurological deficits correlated to intraoperative neuromonitoring alerts from two neuromonitoring signals: motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs). <h3>STUDY DESIGN/SETTING</h3> A multicenter, multisurgeon prospective quality improvement initiative that was performed in conjunction with neuro alert (NA) monitoring services. All data was retrospectively analyzed. <h3>PATIENT SAMPLE</h3> A total of 289 patients who (1) received nondeformity lumbar (45%), cervical (45%) or thoracic (10%) surgery between July 2018 and July 2019 and (2) underwent SSEP and MEP monitoring throughout the entire surgery. <h3>OUTCOME MEASURES</h3> This study investigated the incidence of immediate postoperative (≤ 48 hours) new neurological deficits. sensitivty, specificity, postive predictive value (PPV), and negative predictive value (NPV) was calculated for the SSEP and MEP signals. <h3>METHODS</h3> This study was a multicenter, multisurgeon prospective quality improvement initiative that was performed in conjunction with neuro alert (NA) monitoring services. All neuromonitoring was carried out in accordance with the guidelines set forth by the American Academy of Neurology and the American Board for Neurophysiological Monitoring Programs. Two commonly used MIOM signals were tracked: somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs). Intraoperative data were recorded using a paper data collection tool. SSEP and MEP signal changes were classified as alerts based on the following best practices guidelines outlined in the literature: 50% or greater decrease in signal amplitude and/or a 10% or greater increase in signal latency with no signal recovery. Immediate postoperative (≤ 48 hours) new neurological deficit status was assessed for all patients. Neurological deficit information was recorded via paper during a postoperative physical exam that all physicians conducted on the patient within 48 hours after surgery. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the SSEP and MEP signals were calculated. <h3>RESULTS</h3> SSEP and MEP neuromonitoring data was analyzed for 289 patients who (1) received non-deformity lumbar (45%), cervical (45%) or thoracic (10%) surgery between July 2018 and July 2019 and (2) underwent SSEP and MEP monitoring throughout the entire surgery. A total of 22 MEP and 16 SSEP alerts were triggered. Ninety percent (20) of MEP alerts occurred during anterior cervical discectomy and fusion (ACDF) procedures; one MEP alert was triggered during a posterior cervical fusion and one MEP alert was triggered during a lumbar laminectomy. 56% (9) of SSEP alerts occurred during transforaminal lumbar interbody fusion procedures while 25% (4) occurred during ACDFs and 19% (3) occurred during lumbar laminectomy surgeries. MEP and SSEP alerts were most frequently triggered during the decompression surgical step (45% and 25%, respectively). There were 6 instances (n = 6) of new neurological deficits that occurred within 48 hours postsurgery. These deficits were as follows: foot drop (n = 1), leg weakness (n = 1), arm weakness (n = 2), bilateral paraparesis (n = 1) and unilateral paraparesis (n = 1). The patient who developed unilateral paraparesis was myelopathic. All other patients with new neurological deficits did not have a history of myelopathy. The MEP alert should have been triggered for all 6 patients, however the signal was only alerted in the patient who developed bilateral paraparesis and in one patient who developed arm weakness. In 4/6 patients, MEP alerts were not triggered but a new neurological deficit occurred, resulting in a false negative rate of 67% and a sensitivity of 33%. In addition, MEPs had a specificity of 92.4%, PPV of 11% and NPV of 98.5%. The SSEP signal showed 100% sensitivity and displayed a specificity, PPV and NPV of 95.2%, 12.5% and 100%, respectively. <h3>CONCLUSIONS</h3> The MEP signal had a low sensitivity of 33%, which differed greatly from that of the SSEP signal (100%). The specificity, PPV and NPV were comparable between the SSEPs and MEPs. The PPV was low for both signals. Results indicate that the accuracy of SSEP and MEP alerts in detecting new neurological deficits in spine surgery patients immediately postsurgery is questionable. The effectiveness of these two intraoperative neuromonitoring techniques in identifying neurological injury seems uncertain and needs to be explored further. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs

Multicenter Retrospective Analysis of Dorsal Root Ganglion Stimulator Placement Using Intraoperative Neuromonitoring in Asleep Patients During Early Periods of Adoption

Intraoperative neuromonitoring (IONM) has been used in the implantation of spinal cord stimulation for both safety and confirmation of lead placement. It is less well defined in its use for dorsal root ganglion (DRG) stimulator placement. This is a retrospective analysis of 304 leads placed in 93 patients undergoing DRG stimulation therapy with its placement utilizing IONM in asleep patients by four implanting physicians in four separate centers. The first year, or early adoption period, of placements for each site was chosen as the included cases to evaluate. There were a total of 14 IONM alerts across the 304 lead placements. There were two complications, no permanent or severe adverse events, and no revisions. All alerts led to a change in approach as a corrective action. The two complications were a patient requiring a blood patch for an undetected CSF leak, while the other was a generator site seroma that resolved with conservative care. A single patient experienced transient calf paresthesia's in the post-operative period. This retrospective series demonstrates the utility and accuracy of IONM in not only confirming proper dorsal placement of a DRG electrode but also in maintaining a low adverse event profile. It further demonstrates that its utility in the real world with new users can be safe and accurate with an ease of integration.

Multimodality Intraoperative Neuromonitoring in Lateral Lumbar Interbody Fusion: A Review of Alerts in 628 Patients.

Retrospective review of private neuromonitoring databases. To review neuromonitoring alerts in a large series of patients undergoing lateral lumbar interbody fusion (LLIF) and determine whether alerts occurred more frequently when more lumbar levels were accessed or more frequently at particular lumbar levels. Intraoperative neuromonitoring (IONM) databases were reviewed and patients were identified undergoing LLIF between L1 and L5. All cases in which at least one IONM modality was used (motor evoked potentials (MEP), somatosensory evoked potentials (SSEP), evoked electromyography (EMG)) were included in this study. The type of IONM used and incidence of alerts were collected from each IONM report and analyzed. The incidence of alerts for each IONM modality based on number of levels at which at LLIF was performed and the specific level an LLIF was performed were compared. A total of 628 patients undergoing LLIF across 934 levels were reviewed. EMG was used in 611 (97%) cases, SSEP in 561 (89%), MEP in 144 (23%). The frequency of IONM alerts for EMG, SSEP and MEPs did not significantly increase as the number of LLIF levels accessed increased. No EMG, SSEP, or MEP alerts occurred at L1-L2. EMG alerts occurred in 2-5% of patients at L2-L3, L3-L4, and L4-L5 and did not significantly vary by level (P = .34). SSEP and MEP alerts occurred more frequently at L4-L5 versus L2-L3 and L3-L4 (P < .03). IONM may provide the greatest utility at L4-L5, particularly MEPs, and may not be necessary for more cephalad LLIF procedures such as at L1-L2.

227. Is the axial spinal cord classification predictive of intraoperative neurologic alert for pediatric scoliosis patients? A validation study

BACKGROUND CONTEXT Neurologic deficit is a devastating complication in pediatric spinal deformity surgery. Identification of high-risk patients may improve preoperative planning and assist in counseling of patients and families. PURPOSE We proposed to determine if the axial spinal cord classification as described by Sielatycki and Lenke would be associated with a high rate of intraoperative neuromonitoring alerts for pediatric scoliosis patients undergoing posterior spinal fusion surgery. STUDY DESIGN/SETTING Retrospective chart review study. PATIENT SAMPLE A total of 90 pediatric scoliosis patients. OUTCOME MEASURES n/a METHODS Pediatric scoliosis patients undergoing posterior spinal fusion were retrospectively reviewed at a single tertiary referral center. As MRI is not routinely obtained prior to surgery, only those patients with a preoperative MRI showing high quality axial imaging of the apex of the thoracic deformity were included. MRI was reviewed for spinal cord/ CSF architecture as described by Sielatycki and Lenke. Based on this classification there are 3 types of cords. Type 1: circular cord with visible CSF between the cord and the apical concave pedicle. Type 2: circular cord but no visible CSF at apical concavity. Type 3: cord deformed with no intervening CSF. Intraoperative neuromonitoring records and operative reports were reviewed to determine presence of a neurologic alert. Preoperative radiographs were used to measure Cobb angle, kyphosis and deformity angular ratio (total DAR = coronal DAR + sagittal DAR). RESULTS A total of 90 patients met inclusion criteria. Diagnoses included idiopathic scoliosis (74%), followed by congenital (9%), syndromic (7%), neuromuscular/other (10%). Rate of neurologic events was Type 1: 2% (1/41 patients), Type 2: 14.3% (4/28), Type 3: 52% (11/21, p CONCLUSIONS Although there may be bias in the cohort in that only patients considered to be higher risk have preoperative MRI imaging, the axial MRI spinal cord classification correlated with intraoperative neuromonitoring alerts in pediatric scoliosis patients. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Responding to Intraoperative Neuromonitoring Changes During Pediatric Coronal Spinal Deformity Surgery.

Study Design:Retrospective case study on prospectively collected data.Objectives:The purpose of this explorative study was: 1) to determine if patterns of spinal cord injury could be detected through intra-operative neuromonitoring (IONM) changes in pediatric patients undergoing spinal deformity corrections, 2) to identify if perfusion based or direct trauma causes of IONM changes could be distinguished, 3) to observe the effects of the interventions performed in response to these events, and 4) to attempt to identify different treatment algorithms for the different causes of IONM alerts.Methods:Prospectively collected neuromonitoring data in pre-established forms on consecutive pediatric patients undergoing coronal spinal deformity surgery at a single center was reviewed. Real-time data was collected on IONM alerts with >50% loss in signal. Patients with alerts were divided into 2 groups: unilateral changes (direct cord trauma), and bilateral MEP changes (cord perfusion deficits).Results:A total of 97 pediatric patients involving 71 females and 26 males with a mean age of 14.9 (11-18) years were included in this study. There were 39 alerts in 27 patients (27.8% overall incidence). All bilateral changes responded to a combination of transfusion, increasing blood pressure, and rod removal. Unilateral changes as a result of direct trauma, mainly during laminotomies for osteotomies, improved with removal of the causative agent. Following corrective actions in response to the alerts, all cases were completed as planned. Signal returned to near baseline in 20/27 patients at closure, with no new neurological deficits in this series.Conclusion:A high incidence of alerts occurred in this series of cases. Dividing IONM changes into perfusion-based vs direct trauma directed treatment to the offending cause, allowing for safe corrections of the deformities. Patients did not need to recover IONM signal to baseline to have a normal neurological examination.

Intraoperative Neuromonitoring (IONM): Is There a Role in Metastatic Spine Tumor Surgery?

A retrospective design. We aim to report our experience with multimodal intraoperative neuromonitoring (IONM) in metastatic spine tumor surgery (MSTS). IONM is considered as standard of care in spinal deformity surgeries. However, limited data exist about its role in MSTS. A total of 135 patients from 2010 to 2017, who underwent MSTS with IONM at our institute, were studied retrospectively. After excluding seven with no baseline signals, 128 patients were analyzed. The data collected comprised of demographics, pre and postoperative American Spinal Injury Association (ASIA) grades and neurological status, indications for surgery, type of surgical approach. Multimodal IONM included somatosensory-evoked potentials (SSEPs), transcranial electric motor-evoked potentials (tcMEP), and free running electromyography (EMG). The 128 patients included 61 males and 67 females with a mean age of 61 years. One hundred sixteen underwent posterior procedures; nine anterior and three both. The frequency of preoperative ASIA Grades were A = 0, B = 0, C = 10, D = 44, and E = 74 patients. In total, 54 underwent MSTS for neurological deficit, 66 for instability pain, and 8 for intractable pain.Of 128 patients, 13 (10.2%) had significant IONM alerts, representing true positives; 114 true negatives, one false negative, and no false positives. Among the 13 true positives, four (30%) underwent minimally invasive and nine (70%) open procedures. Eight (69.2%) patients had posterior approach. Seven (53.84%) true positive alerts were during decompression, which resolved to baseline upon completion of decompression, while five (38.46%) were during instrumentation, which recovered to baseline after adjusting/downsizing the instrumentation, and one (8.3%) during lateral approach, which reversed after changing the plane of dissection. Of the seven patients without baseline, five were ASIA-A and two were ASIA-C. The sensitivity, specificity, positive, and negative predictive values were 99.1%, 100%, 100%, and 92.9%, respectively. Multimodal IONM in MSTS helped in preventing postoperative neurological deficit in 9.4% of patients. Its high sensitivity and specificity to detect intraoperative neurological events envisage its use in ASIA-grade D/E patients requiring instrumented decompression. 3.

Ponte Osteotomies Increase the Risk of Neuromonitoring Alerts in Adolescent Idiopathic Scoliosis Correction Surgery.

Observational cohort study of prospective database registry. To determine the incidence of neurological complications in AIS patients undergoing surgical treatment with PO. Despite the widespread use of Ponte Osteotomies (PO) in adolescent idiopathic scoliosis (AIS) correction, outcomes and complications in patients treated with this technique have not been well characterized. A multicenter prospective registry of patients undergoing surgical correction of AIS was queried at 2-year follow-up for patient demographics, surgical data, deformity characteristics, and peri-operative complications. A neurological complication was defined as perioperative nerve root or spinal cord injury as identified by the surgeon. Patients were divided into those who underwent peri-apical PO and those without, and further stratified by Lenke curve classification into 3 groups (I-types 1 and 2, II-types 3, 4, 6, and III-type 5). Patients with- and without neurological complications were compared with respect to baseline demographics, surgical variables, curve types, fusion construct types (screws vs. hybrid), curve magnitude (coronal and sagittal Cobb), apical vertebral translation, and coronal-deformity angular ratios (C-DAR). Of 2210 patients included in the study, 1611 underwent PO. Peri-operative neurological complications occurred in 7 patients, with 6 in the PO group (0.37%) and 1 in non-PO group (0.17%) though this was not a statistically significant risk factor for peri-operative neurological injury (P = 0.45). Neuromonitoring alerts were recorded in 168 patients (7.6%: 9.3% PO group; 4.2% no-PO group (P < 0.001)). Multivariate logistic regression analysis found PO and curve magnitude to be independent risk factors for intraoperative neuromonitoring alerts (P < 0.01). PO and curve magnitude were independent risk factors for intraoperative neuromonitoring alerts in surgical AIS correction. The effect of Ponte osteotomy on neurological complications remains unknown due to the low incidence of these complications. 3.

Intraoperative Neuromonitoring During Adult Spinal Deformity Surgery: Alert-Positive Cases for Various Surgical Procedures

Study DesignRetrospective study. ObjectivesTo analyze intraoperative neuromonitoring (IONM) alerts in various surgical procedures and clarify incidences and causes of IONM alarms in consecutive adult spinal deformity (ASD) surgeries. Summary of Background DataASD surgery has a high neurologic complication rate. IONM may play a role in identifying and preventing neurologic complications. MethodsThis study included 275 consecutive ASD patients treated by posterior corrective fusion who had been followed up for more than two years. We divided the patients into 1) the PCO group: multiple posterior column osteotomies; and 2) the 3CO group: three-column osteotomy including pedicle subtraction osteotomy and vertebral column resection. We set a 70% amplitude reduction as the alarm point for transcranial electrical stimulation motor-evoked potentials (Tc-MEPs) using 32-channel IONM. ResultsThe PCO and 3CO groups included 162 and 113 cases, respectively. IONM revealed 32 cases (11.6%) of Tc-MEP alerts, 10.4% in the PCO group, and 13.2% in the 3CO group. Postoperative follow-ups revealed 15 cases (5.5%) of new neurologic deficits, 4.9% in the PCO group, and 6.2% in the 3CO group. Most IONM alarms in the PCO group appeared at the time of rod rotation maneuvers, and 88.9% of alarms were selective for MEP decrease. In contrast, IONM alarms in the 3CO group appeared at the time of spinal shortening, and 80% were global MEP decreases. Immediately after the alarm, neurologic deficits might be rescued by foraminal decompression after rod rotation and by adjusting the length of spinal shortening. Overall, more than 50% of cases with IONM alerts were rescued by intraoperative additional management. ConclusionIONM reduced the incidence of neurologic complications in ASD surgery. Spinal surgeons should recognize the type of muscle derivation and respond to such alerts by performing appropriate corrections reflecting the mechanism underlying the neural damage. Level of EvidenceLevel IV.