Multimodal Intraoperative Spinal Cord Monitoring during Spinal Deformity Surgery: Efficacy, Diagnostic Characteristics, and Algorithm Development

Pediatric Intraoperative Neurophysiological Monitoring and Long-Term Outcomes in a Developing Country

PURPOSE

Pediatric intraoperative neurophysiological monitoring (IONM) has been shown to be effective in preventing and reversing postoperative neurological deficits in developed countries. There are currently no published studies from developing countries that describe neurophysiological findings and postoperative outcomes. Our study aims to address these gaps in children undergoing neurosurgical procedures in a single center.

METHODS

We conducted a retrospective study of case series of children who underwent IONM (2014-2020) in the State of Mexico, Mexico. Sociodemographic characteristics, IONM modalities, changes during procedures, and short-term and long-term postoperative results were recorded. Descriptive statistics were used.

RESULTS

We included 35 patients (≤18 years of age), 57% (20/35) boys. A relative increase of up to 5 times in the use of IONM is observed from 2014 (5.7%) to 2020 (25.7%) in our center. The most frequent preoperative pathologies were located at the infratentorial cranium (40%), followed by the spine and spinal cord (37.1%). The IONM modalities were as follows: free-running EMG 94.3%, transcranial electrical stimulation motor-evoked potentials 91.4%, somatosensory-evoked potentials 85.7%, triggered EMG 28.6%, EEG 25.7%, and visual-evoked potentials 5.7%. Only in 8.3%, we did not obtain sufficient evoked potential baseline signals. At 24 hours postoperatively true negatives were 100%. Long-term follow-up was completed in 22/35 (63%) at 3 months, 12/35 (34.2%) at 6 months, and 5/35 (14.3%) at 12 months with progressive motor and sensory improvement.

CONCLUSIONS

Pediatric multimodal IONM in neurosurgeries from a single center in a developing country is mainly used in pathologies of the posterior fossa, spine, and spinal cord, with true negatives in 100% of those monitored, preventing and avoiding postoperative sequelae.

Management Principles in a Case of True-positive Loss of Neuromonitoring Signals during Scoliosis Surgery: A Case Report

Introduction

Multimodal intraoperative neuromonitoring (IOM) is essential in scoliosis surgery. This is affected by misplaced instrumentation, cord trauma, hemodynamic instability, and anesthesia. We present an irreversible loss of IOM without identifiable intra-operative cause to highlight its occurrence and discuss post-operative investigations and management.

Case Report

A 14-year-old girl with adolescent idiopathic scoliosis, no co-morbidities, and normal spinal magnetic resonance imaging (MRI) underwent posterior spinal fusion. During screw placement, bilateral motor evoked potentials (MEPs) and right somatosensory evoked potentials (SSEPs) were lost in the legs. All screws were removed with no evidence of cortical breach. Left leg responses gradually improved, but there was no recovery of right leg SSEPs or MEPs. Subsequently, the procedure was abandoned. The patient had reduced right leg strength (3/5) and sensation with the left leg was normal. Immediate post-operative spinal MRI identified no abnormality. Computed tomography (CT) showed no cortical breach with satisfactory pedicle screw tracts. Repeat MRI (day 7) showed high T2-signal within the cord at T11 indicating ischemia. Gradual neurological recovery occurred and on day 15, repeat neurophysiology found reproducible SSEPs and MagStim MEPs. The patient underwent revision posterior fusion with single rod correction without complication and IOM was maintained. By day 24, the patient had 5/5 power and normal sensation in both legs. Good scoliosis correction was achieved and maintained at 3-year follow-up.

Conclusion

This patient represents a vascular event affecting the lower spinal cord and highlights the role of sequential imaging and pre-operative neurophysiology including MagStim in deciding when to proceed with revision surgery while reducing risk using conservative techniques.

The Management of Intraoperative Spinal Cord Injury - A Scoping Review

STUDY DESIGN

Scoping Review.

OBJECTIVE

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).

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Accuracy of Intraoperative Neuromonitoring in the Diagnosis of Intraoperative Neurological Decline in the Setting of Spinal Surgery-A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVES

In an effort to prevent intraoperative neurological injury during spine surgery, the use of intraoperative neurophysiological monitoring (IONM) has increased significantly in recent years. Using IONM, spinal cord function can be evaluated intraoperatively by recording signals from specific nerve roots, motor tracts, and sensory tracts. We performed a systematic review and meta-analysis of diagnostic test accuracy (DTA) studies to evaluate the efficacy of IONM among patients undergoing spine surgery for any indication.

METHODS

The current systematic review and meta-analysis was performed using the Preferred Reporting Items for a Systematic Review and Meta-analysis statement for Diagnostic Test Accuracy Studies (PRISMA-DTA) and was registered on PROSPERO. A comprehensive search was performed using MEDLINE, EMBASE and SCOPUS for all studies assessing the diagnostic accuracy of neuromonitoring, including somatosensory evoked potential (SSEP), motor evoked potential (MEP) and electromyography (EMG), either on their own or in combination (multimodal). Studies were included if they reported raw numbers for True Positives (TP), False Negatives (FN), False Positives (FP) and True Negative (TN) either in a 2 × 2 contingency table or in text, and if they used postoperative neurologic exam as a reference standard. Pooled sensitivity and specificity were calculated to evaluate the overall efficacy of each modality type using a bivariate model adapted by Reitsma et al, for all spine surgeries and for individual disease groups and regions of spine. The risk of bias (ROB) of included studies was assessed using the quality assessment tool for diagnostic accuracy studies (QUADAS-2).

RESULTS

A total of 163 studies were included; 52 of these studies with 16,310 patients reported data for SSEP, 68 studies with 71,144 patients reported data for MEP, 16 studies with 7888 patients reported data for EMG and 69 studies with 17,968 patients reported data for multimodal monitoring. The overall sensitivity, specificity, DOR and AUC for SSEP were 71.4% (95% CI 54.8-83.7), 97.1% (95% CI 95.3-98.3), 41.9 (95% CI 24.1-73.1) and .899, respectively; for MEP, these were 90.2% (95% CI 86.2-93.1), 96% (95% CI 94.3-97.2), 103.25 (95% CI 69.98-152.34) and .927; for EMG, these were 48.3% (95% CI 31.4-65.6), 92.9% (95% CI 84.4-96.9), 11.2 (95% CI 4.84-25.97) and .773; for multimodal, these were found to be 83.5% (95% CI 81-85.7), 93.8% (95% CI 90.6-95.9), 60 (95% CI 35.6-101.3) and .895, respectively. Using the QUADAS-2 ROB analysis, of the 52 studies reporting on SSEP, 13 (25%) were high-risk, 10 (19.2%) had some concerns and 29 (55.8%) were low-risk; for MEP, 8 (11.7%) were high-risk, 21 had some concerns and 39 (57.3%) were low-risk; for EMG, 4 (25%) were high-risk, 3 (18.75%) had some concerns and 9 (56.25%) were low-risk; for multimodal, 14 (20.3%) were high-risk, 13 (18.8%) had some concerns and 42 (60.7%) were low-risk.

CONCLUSIONS

These results indicate that all neuromonitoring modalities have diagnostic utility in successfully detecting impending or incident intraoperative neurologic injuries among patients undergoing spine surgery for any condition, although it is clear that the accuracy of each modality differs.PROSPERO Registration Number: CRD42023384158.

Intraoperative neuromonitoring predicts postoperative deficits in severe pediatric spinal deformity patients

PURPOSE

To evaluate intraoperative monitoring (IOM) alerts and neurologic deficits during severe pediatric spinal deformity surgery.

METHODS

Patients with a minimum Cobb angle of 100° in any plane or a scheduled vertebral column resection (VCR) with minimum 2-year follow-up were prospectively evaluated (n = 243). Preoperative, immediate postoperative, and 2-year postoperative neurologic status were reported. Radiographic data included preoperative and 2-year postoperative coronal and sagittal Cobb angles and deformity angular ratios (DAR). IOM alert type and triggering event were recorded. SRS-22r scores were collected preoperatively and 2-years postoperatively.

RESULTS

IOM alerts occurred in 37% of procedures with three-column osteotomy (n = 36) and correction maneuver (n = 32) as most common triggering events. Patients with IOM alerts had greater maximum kyphosis (101.4° vs. 87.5°) and sagittal DAR (16.8 vs. 12.7) (p < 0.01). Multivariate regression demonstrated that sagittal DAR independently predicted IOM alerts (OR 1.05, 95% CI 1.02-1.08) with moderate sensitivity (60.2%) and specificity (64.8%) using a threshold value of 14.3 (p < 0.01). IOM alerts occurred more frequently in procedures with new postoperative neurologic deficits (17/24), and alerts with both SSEP and TCeMEP signals were associated with new postoperative deficits (p < 0.01). Most patients with new deficits experienced resolution at 2 years (16/20) and had equivalent postoperative SRS-22r scores. However, patients with persistent deficits had worse SRS-22r total score (3.8 vs. 4.2), self-image subscore (3.5 vs. 4.1), and function subscore (3.8 vs. 4.3) (p ≤ 0.04).

CONCLUSION

Multimodal IOM alerts are associated with sagittal kyphosis, and predict postoperative neurologic deficits. Most patients with new deficits experience resolution of their symptoms and have equivalent 2-year outcomes.

LEVEL OF EVIDENCE

II.

Feasibility, Safety and Reliability of Surgeon-Directed Transcranial Motor Evoked Potentials Monitoring in Scoliosis Surgery

(1) Background: Neuromonitoring is essential in corrective surgery for scoliosis. Our aim was to assess the feasibility, safety and reliability of "surgeon-directed" intraoperative monitoring transcranial motor evoked potentials (MEP) of patients. (2) Methods: A retrospective single-center study of a cohort of 190 scoliosis surgeries, monitored by NIM ECLIPSE (Medtronic), between 2017 and 2021. Girls (144) and boys (46) (mean age of 15 years) were included. There were 149 idiopathic and 41 secondary scoliosis. The monitoring consisted of stimulating the primary motor cortex to record the MEP with muscular recording on the thenar, vastus lateralis, tibialis anterior and adductor hallucis muscles. (3) Results: The monitoring data was usable in 180 cases (94.7%), with 178 true negatives, no false negatives and one false positive. There was one true positive case. The predictive negative value was 100%. The monitoring data was unusable in 10 cases (i.e., three idiopathic and seven secondary scoliosis). (4) Conclusions: Simplified transcranial MEP monitoring known as "surgeon-directed module" is usable, safety and reliable in surgery for moderate scoliosis. It is feasible in 95% of cases with a negative predictive value of 100%.

Consensus for management of sacral fractures: from the diagnosis to the treatment, with a focus on the role of decompression in sacral fractures

BACKGROUND

There is no evidence in the current literature about the best treatment option in sacral fracture with or without neurological impairment.

MATERIALS AND METHODS

The Italian Pelvic Trauma Association (A.I.P.) decided to organize a consensus to define the best treatment for traumatic and insufficiency fractures according to neurological impairment.

RESULTS

Consensus has been reached for the following statements: When complete neurological examination cannot be performed, pelvic X-rays, CT scan, hip and pelvis MRI, lumbosacral MRI, and lower extremities evoked potentials are useful. Lower extremities EMG should not be used in an acute setting; a patient with cauda equina syndrome associated with a sacral fracture represents an absolute indication for sacral reduction and the correct timing for reduction is "as early as possible". An isolated and incomplete radicular neurological deficit of the lower limbs does not represent an indication for laminectomy after reduction in the case of a displaced sacral fracture in a high-energy trauma, while a worsening and progressive radicular neurological deficit represents an indication. In the case of a displaced sacral fracture and neurological deficit with imaging showing no evidence of nerve root compression, a laminectomy after reduction is not indicated. In a patient who was not initially investigated from a neurological point of view, if a clinical investigation conducted after 72 h identifies a neurological deficit in the presence of a displaced sacral fracture with nerve compression on MRI, a laminectomy after reduction may be indicated. In the case of an indication to perform a sacral decompression, a first attempt with closed reduction through external manoeuvres is not mandatory. Transcondylar traction does not represent a valid method for performing a closed decompression. Following a sacral decompression, a sacral fixation (e.g. sacroiliac screw, triangular osteosynthesis, lumbopelvic fixation) should be performed. An isolated and complete radicular neurological deficit of the lower limbs represents an indication for laminectomy after reduction in the case of a displaced sacral fracture in a low-energy trauma associated with imaging suggestive of root compression. An isolated and incomplete radicular neurological deficit of the lower limbs does not represent an absolute indication. A worsening and progressive radicular neurological deficit of the lower limbs represents an indication for laminectomy after reduction in the case of a displaced sacral fracture in a low-energy trauma associated with imaging suggestive of root compression. In the case of a displaced sacral fracture and neurological deficit in a low-energy trauma, sacral decompression followed by surgical fixation is indicated.

CONCLUSIONS

This consensus collects expert opinion about this topic and may guide the surgeon in choosing the best treatment for these patients.

LEVEL OF EVIDENCE

IV.

TRIAL REGISTRATION

not applicable (consensus paper).

Paediatric Spinal Deformity Surgery: Complications and Their Management

Surgical correction of paediatric spinal deformity is associated with risks, adverse events, and complications that must be preoperatively discussed with patients and their families to inform treatment decisions, expectations, and long-term outcomes. The incidence of complications varies in relation to the underlying aetiology of spinal deformity and surgical procedure. Intraoperative complications include bleeding, neurological injury, and those related to positioning. Postoperative complications include persistent pain, surgical site infection, venous thromboembolism, pulmonary complications, superior mesenteric artery syndrome, and also pseudarthrosis and implant failure, proximal junctional kyphosis, crankshaft phenomenon, and adding-on deformity, which may necessitate revision surgery. Interventions included in enhanced recovery after surgery protocols may reduce the incidence of complications. Complications must be diagnosed, investigated and managed expeditiously to prevent further deterioration and to ensure optimal outcomes. This review summarises the complications associated with paediatric spinal deformity surgery and their management.

Multimodal Neuroelectrophysiological Monitoring Combined with Robot-Assisted Placement of a Transiliac–Transsacral Screw for the Treatment of Transforaminal Sacral Fractures

Objective

This study aimed to evaluate the safety and efficacy of the fixation of transforaminal sacral fractures using TiRobot-assisted transiliac-transsacral (TITS) screws under multimodal neuroelectrophysiological monitoring (MNM).

Methods

From January 2019 to May 2021, 22 patients (17 male and 5 female patients) with transforaminal sacral fractures who were treated with closed reduction and placement of TiRobot-assisted TITS screws under MNM were retrospectively evaluated. The average age of the patients was 43.32 ± 11.40 years (range: 19–63). The patients received MNM, including somatosensory-evoked potentials (SEPs), motor-evoked potentials (MEPs), and electromyographic monitoring (EMG), prior to surgery, during closed reduction and the placement of the guidewire and TITS screw, and at the end of surgery. The operation was adjusted according to the MNM results.

Results

Overall, 22 TITS screws were inserted in 22 patients, including 5 TITS screws in the S1 body and 17 TITS screws in the S2 body. The average time needed for screw placement was 27.95 ± 6.84 mins, and the average frequency of X-ray fluoroscopy exposures was 31.00 ± 5.56 for each patient. Anterior ring fixation was performed in 4 patients using an external fixator, in 5 patients using cannulated screws, and in 13 patients using reconstruction plates. The mean follow-up time was 14.46 ± 2.46 months (12–20 months). Tornetta and Matta radiographic outcomes were excellent in 10 patients, good in 9 patients, fair in 2 patients, and poor in 1 patient. The proportion of excellent and good ratings was 86.36%. At the final follow-up, the average Majeed score was 82.18 ± 14.52, with clinical outcomes that were excellent in 9 patients, good in 9 patients, fair in 1 patient, and poor in 3 patients. The proportion of excellent and good ratings was 82.82%. Preoperatively, the amplitude of the SEP on the injured side was lower than that on the contralateral side before reduction in 9 patients (>50%). In this study, no screw was mistakenly inserted into the sacral canal, and no surgical site infection occurred.

Conclusion

MNM combined with TiRobot assistance can safely implant TITS screws and can effectively identify the neurological function of patients under anesthesia and reduce iatrogenic nerve injury.

Enhanced Safety of Pedicle Subtraction Osteotomy Using Intraoperative Ultrasound

BACKGROUND

Pedicle subtraction osteotomy (PSO) can improve sagittal alignment but carries risks, including iatrogenic spinal cord and nerve root injury. Critically, during the reduction phase of the technique, medullary kinking or neural element compression can lead to neurologic deficits.

METHODS

We describe 3 cases of thoracic PSO and evaluate the feasibility, findings, and utility of intraoperative ultrasound in this setting.

RESULTS

Intraoperative ultrasound can provide a visual assessment of spinal cord morphology before and after PSO reduction and influences surgical decision making with regard to the final amount of sagittal plane correction. This modality is particularly useful for confirming ventral decompression of disc-osteophyte complex before reduction and also after reduction maneuvers when there is kinking of the thecal sac but uncertainty about the underlying status of the spinal cord. Intraoperative ultrasound is a reliable modality that fits well into the technical sequence of PSO, adds a minimal amount of operative time, and has few limitations.

CONCLUSIONS

We propose that intraoperative ultrasound is a useful supplement to standard neuromonitoring modalities for ensuring safe PSO reduction and decompression of neural elements.

Intraoperative neuromonitoring practice patterns in spinal deformity surgery: a global survey of the Scoliosis Research Society

PURPOSE

Although multimodal IONM has reached a widespread use, several unresolved issues have remained in clinical practice. The aim was to determine differences in approaches to form a basis for taking actions to improve patient safety globally.

METHODS

A survey comprising 19 questions in four sections (demographics, setup, routine practices and reaction to alerts) was distributed to the membership of the SRS.

RESULTS

Of the estimated 1300 members, 205 (~ 15%) completed the survey. Respondent demographics reflected SRS member distribution. Most of the respondents had > 10 years of experience. TcMEP and SSEP were available to > 95%. Less than 5% reported that a MD/PhD with neurophysiology background routinely examines patients preoperatively, while 19% would consult if requested. After an uneventful case, 36% reported that they would decrease sedation and check motor function if the patient was to be transferred to ICU intubated. Reactions to dropped signals that recovered or did not fully recover varied between attempting the same correction to aborting the surgery with no rods and returning another day, with or without implant removal. After a decrease of signals, 85.7% use steroids of varied doses. Of the respondents, 53.7% reported using the consensus-created checklist by Vitale et al. Approximately, 14% reported never using the wake-up test while others use it for various conditions.

CONCLUSION

The responses of 205 experienced SRS members from different regions of the world showed that surgeons had different approaches in their routine IONM practices and in the handling of alerts. This survey indicates the need for additional studies to identify best practices.

The surgical treatment of severe Scheuermann's kyphosis

AIMS

To report the surgical outcome of patients with severe Scheuermann's kyphosis treated using a consistent technique and perioperative management.

METHODS

We reviewed 88 consecutive patients with a severe Scheuermann's kyphosis who had undergone posterior spinal fusion with closing wedge osteotomies and hybrid instrumentation. There were 55 males and 33 females with a mean age of 15.9 years (12.0 to 24.7) at the time of surgery. We recorded their demographics, spinopelvic parameters, surgical correction, and perioperative data, and assessed the impact of surgical complications on outcome using the Scoliosis Research Society (SRS)-22 questionnaire.

RESULTS

The mean follow-up was 8.4 years (2 to 14.9). There were 85 patients (96.6%) with a thoracic deformity. Posterior spinal fusion with closing-wedge osteotomies and hybrid instrumentation was used in 86 patients; two patients underwent combined anterior and posterior spinal fusion. The mean kyphosis was corrected from 94.5° to 47.5° (p < 0.001). Coronal and sagittal balance returned to normal. The rate of complications was 12.5%: there were no neurological deficits, implant failure, or revision surgery. SRS-22 scores improved from a mean 3.6 (1.3 to 4.1) to 4.6 (4.2 to 5.0) at two years (p < 0.001) with a high rate of patient satisfaction. Non-smokers and patients with lower preoperative SRS-22 scores showed greater improvement in their quality of life. Sagittal pelvic balance did not change after correction of the kyphosis and correlated with lumbar lordosis but not with thoracic or thoracolumbar kyphosis.

CONCLUSION

Posterior spinal fusion using hybrid instrumentation, closing-wedge osteotomies, and iliac bone grafting achieves satisfactory correction of a severe kyphosis resulting in improvements in physical and mental health and a high degree of patient-reported satisfaction. Cite this article: Bone Joint J 2021;103-B(1):148-156.

Neurophysiological monitoring of spinal cord function during spinal deformity surgery: 2020 SRS neuromonitoring information statement

The Scoliosis Research Society has developed an updated information statement on intraoperative neurophysiological monitoring of spinal cord function during spinal deformity surgery. The statement reviews the risks of spinal cord compromise associated with spinal deformity surgery; the statement then discusses the various modalities that are available to monitor the spinal cord, including somatosensory-evoked potentials, motor-evoked potentials, and electromyographic (EMG) options. Anesthesia considerations, the importance of a thoughtful team approach to successful monitoring, and the utility of checklists are also discussed. Finally, the statement expresses the opinion that utilization of intraoperative neurophysiological spinal cord monitoring in spinal deformity surgery is the standard of care when the spinal cord is at risk.