Intra-Operative Neurophysiological Monitoring in Patients with Intraspinal Abnormalities Undergoing Posterior Spinal Fusion

Effect of Spinal Cord Compression and Deformation on Postoperative Neurological Deficits During Spinal Deformity Correction Surgery

Study DesignRetrospective comparative analysis.ObjectiveTo evaluate the impact of the spinal cord deformation rate (SCDR) on postoperative neurological deficits (PNDs) in spinal deformity surgery and to determine the optimal SCDR threshold for risk stratification.MethodsPatients undergoing corrective surgery between October 2010 and March 2022 were included. Spinal cord morphology at the apex was assessed using axial T2-weighted magnetic resonance imaging, categorizing spinal cords into type-A and type-B. Differences between the two groups were analyzed and the odds ratio (OR) for PNDs in patients with type-B was calculated. For patients classified as type-B, univariate analysis was conducted to identify variables, including SCDR, that may influence PNDs risk. Statistically significant variables were further analyzed using multivariate analysis. The receiver operating characteristic (ROC) curve and area under the curve (AUC) analyses were performed to evaluate the discriminative ability of risk factors and determine the optimal cut-off value.ResultsAmong 200 patients included, PNDs occurred in 17 cases (8.5%), predominantly in type-B (15/82 in type-B vs 2/118 in type-A, P < 0.001). Multivariate analysis revealed SCDR as an independent predictor of PNDs (OR = 1.076, P = 0.001). ROC analysis determined an optimal SCDR cutoff of 42.15% (AUC: 0.867), with 82.4% sensitivity, 88.5% specificity, and 98.2% negative predictive value (NPV). SCDR demonstrated superior predictive performance compared to the major Cobb angle (AUC: 0.776) and T-DAR (AUC: 0.769).ConclusionsFor patients undergoing corrective surgery, an SCDR of ≥42.15% serves as a strong predictor of PNDs. Its high NPV effectively excludes low-risk patients, offering improved risk stratification.

Deformity angular distance ratio independently predicts intraoperative neuromonitoring alerts in spinal deformity correction

BACKGROUND

Intraoperative neuromonitoring (IONM) alerts are critical concerns for surgeons performing spinal deformity corrective surgeries, as they indicate a heighteded risk of postoperative neurological deficits. Previous studies have demonstrated that patients with large Cobb angle or elevated deformity angular ratio (DAR) are at an increased risk of IONM alerts. However, spinal curves with similar Cobb angles and DARs may exhibit significantly different risks of IONM alerts during surgery. Current methods for evaluating spinal deformity fail to comprehensively and accurately reflect its severity. The purpose of this study was to investigate whether the deformity angular distance ratio (DADR) serves as an independent predictor of IONM alerts during corrective surgery for spinal deformity.

METHODS

This study analyzed a consecutive series of 404 patients undergoing corrective surgery at a single academic center. Preoperative radiographs were used to calculate the DAR and DADR. Twelve clinically relevant candidate variables were selected for univariable analysis. Multivariable logistic regression analysis was then conducted to identify independent predictors of IONM alerts.

RESULTS

The incidence of IONM alerts in this cohort was 25.2%. Univariable analysis identified several factors potentially associated with IONM alerts, including older age, type-III spinal cord morphology, location of apex, etiological diagnosis, preoperative sagittal Cobb angle, sagittal DAR, sagittal DADR, coronal DADR, total DAR, total DADR, three-column osteotomy, and preoperative neurological deficits. Multivariable analysis revealed that an apex location at C7-T4, preoperative neurological deficits, sagittal DADR, and total DADR were independent predictors of IONM alerts.

CONCLUSIONS

Among patients undergoing corrective surgeries for spinal deformities, the DADR is a robust measure of spinal deformity severity and is strongly correlated with the risk of IONM alerts. Compared to other deformity parameters, DADR is an independent predictor of IONM alerts. Additional independent predictors include the location of the apex and the presence of preoperative neurological deficits.

Assessing Neurological Complications in Thoracic Three-Column Osteotomy: A Clinical Application of a Novel MRI-Based Classification Approach

STUDY DESIGN

Retrospective comparative study.

OBJECTIVE

To investigate the occurrence of neurological complications in patients undergoing thoracic three-column osteotomy (3CO) utilizing an magnetic resonance imaging (MRI)-based classification that assesses spinal cord shape and the presence of cerebrospinal fluid at the curve apex and evaluate its prognostic capacity for postoperative neurological deficits.

SUMMARY OF BACKGROUND DATA

Recent advancements in correction techniques have improved outcomes for severe spinal deformity patients undergoing 3CO. A novel MRI-based spinal cord classification system was introduced, but its validation and association with postoperative complications remain unexplored.

MATERIALS AND METHODS

Between September 2012 and September 2018, a retrospective analysis was conducted on 158 adult patients with spinal deformities undergoing 3CO. Radiographic parameters were measured. T2-weighted axial MRI was used to describe spinal cord morphology at the apex. Intraoperative neurophysiological monitoring alerts were recorded, and preoperative and postoperative neurological functions were assessed using the Frankel score. Categorical data were compared using the χ 2 or the Fisher exact test. The paired t test was utilized to assess the mean difference between preoperative and postoperative measurements, while the one-way analysis of variance and independent t test were used for comparative analyses among the different spinal cord types.

RESULTS

Patients were categorized into three groups: type 1, type 2, and type 3, consisting of 12, 85, and 61 patients. Patients with type 3 morphology exhibited larger Cobb angles of the main curve ( P <0.001). This disparity persisted both postoperatively and during follow-up ( P <0.05). Intraoperative neurophysiological monitoring alerts were triggered in 32 patients (20.3%), with a distribution of one case in type 1, six cases in type 2, and 22 cases in type 3 morphologies ( P <0.001). New neurological deficits were observed in 15 patients (9.5%), with 1, 3, and 11 cases in type 1, 2, and 3 morphologies, respectively.

CONCLUSIONS

Patients with type 3 morphology exhibited greater spinal deformity severity, a higher likelihood of preoperative neurological deficits, and an elevated risk of postoperative neurological complications. This underscores the utility of the classification as a tool for predicting postoperative neurological complications in patients undergoing thoracic 3CO.

LEVEL OF EVIDENCE

4.

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.

Intra-operative Neurophysiological Monitoring in Patients Undergoing Posterior Spinal Correction Surgery with Pre-operative Neurological Deficit: Its Feasibility and High-risk Factors for Failed Monitoring

OBJECTIVE

Considering spinal deformity patients with pre-operative neurological deficit were associated with more intra-operative iatrogenic neurological complications than those without, intra-operative neurophysiological monitoring (IONM) has been used for detecting possible iatrogenic injury timely. However, the IONM waveforms are often unreliable. To analyze the performance of intra-operative neurophysiological monitoring (IONM) including somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) in patients with pre-operative neurological deficit undergoing posterior spinal correction surgery, and to identify the high-risk factors for failed IONM.

METHODS

Patients with pre-operative neurological deficit undergoing posterior spinal correction surgery between October 2017 and January 2022 were retrospectively reviewed. The presence or absence of SEP and MEP of target muscles were separately recorded. The P37/N50 latency and amplitude of SEP, and the MEP amplitude were measured. Any IONM alerts were also recorded. The IONM performance was compared among patients with different etiologies, levels responsible for neurological deficit, and strength of IONM-target muscles. Patients' demographics were analyzed using the descriptive statistics and were presented with mean ± standard deviation. Comparison analysis was performed using χ2 -test and statistically significant difference was defined as p < 0.05.

RESULTS

A total of 270 patients (147 males, 123 females) with an average age of 48.4 ± 36.7 years were involved. The SEP records were available in 371 (68.7%) lower extremities while MEP records were available in 418 (77.4%). SEP alerts were reported in 31 lower extremities and MEP alerts in 22, and new neurological deficit at post-operation was observed in 11. The etiologies of neuromuscular and syndromic indicated relatively lower success rates of IONM, which were 44.1% and 40.5% for SEP, and 58.8% and 59.5% for MEP (p < 0.001). In addition, patients with pre-operative neurological deficit caused by cervical spine and muscle strength lower than grade 4 suffered from higher risk of failed IONM waveforms (p < 0.001).

CONCLUSION

Patients with pre-operative neurological deficit suffered from a higher incidence of failed IONM results. The high-risk for failed IONM waveforms included the neuromuscular and syndromic etiologies, neurological deficit caused by cervical spine, muscle strength lower than grade 4 in patients with pre-operative neurological deficit undergoing posterior spinal correction surgery.