Intraoperative neuromonitoring as real-time diagnostic for cerebral ischemia in endovascular treatment of ruptured brain aneurysms.

OBJECTIVE: To evaluate the diagnostic accuracy of intraoperative neurophysiological monitoring (IONM) during endovascular treatment (EVT) of ruptured intracranial aneurysms (rIA). METHODS: IONM and clinical data from 323 patients who underwent EVT for rIA from 2014-2019 were retrospectively reviewed. Significant IONM changes and outcomes were evaluated based on visual review of data and clinical documentation. RESULTS: Of the 323 patients undergoing EVT, significant IONM changes were noted in 30 patients (9.29%) and 46 (14.24%) experienced postprocedural neurological deficits (PPND). 22 out of 30 (73.33%) patients who had significant IONM changes experienced PPND. Univariable analysis showed changes in somatosensory evoked potential (SSEP) and electroencephalogram (EEG) were associated with PPND (p-values: <0.001 and <0.001, retrospectively). Multivariable analysis showed that IONM changes were significantly associated with PPND (Odd ratio (OR) 20.18 (95%CI:7.40-55.03, p-value: <0.001)). Simultaneous changes in both IONM modalities had specificity of 98.9% (95% CI: 97.1%-99.7%). While sensitivity when either modality had a change was 47.8% (95% CI: 33.9%-62.0%) to predict PPND. CONCLUSIONS: Significant IONM changes during EVT for rIA are associated with an increased risk of PPND. SIGNIFICANCE: IONM can be used confidently as a real time neurophysiological diagnostic guide for impending neurological deficits during EVT treatment of rIA.

Diagnostic utility of different types of somatosensory evoked potential changes in pediatric idiopathic scoliosis correction surgery.

PURPOSE: To evaluate the diagnostic accuracy of intraoperative somatosensory evoked potential (SSEP) monitoring and types of SSEP changes in predicting the risk of postoperative neurological outcomes during correction surgery for idiopathic scoliosis (IS) in the pediatric age group (≤ 21 years). METHODS: Database review was performed to identify literature on pediatric patients with IS who underwent correction with intraoperative neuromonitoring. The sensitivity, specificity, and diagnostic odds ratio (DOR) of transient and persistent SSEP changes and complete SSEP loss in predicting postoperative neurological deficits were calculated. RESULTS: Final analysis included 3778 patients. SSEP changes had a sensitivity of 72.9%, specificity of 96.8%, and DOR of 102.3, while SSEP loss had a sensitivity of 41.8%, specificity of 99.3%, and DOR of 133.2 for predicting new neurologic deficits. Transient and persistent SSEP changes had specificities of 96.8% and 99.1%, and DORs of 16.6 and 59, respectively. CONCLUSION: Intraoperative SSEP monitoring can predict perioperative neurological injury and improve surgical outcomes in pediatric scoliosis fusion surgery. LEVEL OF EVIDENCE: Level 2. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Role of Intraoperative Neuromonitoring to Predict Postoperative Delirium in Cardiovascular Surgery.

OBJECTIVE: Postoperative delirium (POD) can occur in up to 50% of older patients undergoing cardiovascular surgery, resulting in hospitalization and significant morbidity and mortality. This study aimed to determine whether intraoperative neurophysiologic monitoring (IONM) modalities can be used to predict delirium in patients undergoing cardiovascular surgery. DESIGN: Adult patients undergoing cardiovascular surgery with IONM between 2019 and 2021 were reviewed retrospectively. Delirium was assessed multiple times using the Intensive Care Delirium Screening Checklist (ICDSC). Patients with an ICDSC score ≥4 were considered to have POD. Significant IONM changes were evaluated based on a visual review of electroencephalography (EEG) and somatosensory evoked potentials data and documentation of significant changes during surgery. SETTING: University of Pittsburgh Medical Center hospitals. PARTICIPANTS: Patients 18 years old and older undergoing cardiovascular surgery with IONM monitoring. MEASUREMENTS AND MAIN RESULTS: Of the 578 patients undergoing cardiovascular surgery with IONM, 126 had POD (21.8%). Significant IONM changes were noted in 134 patients, of whom 49 patients had delirium (36.6%). In contrast, 444 patients had no IONM changes during surgery, of whom 77 (17.3%) patients had POD. Upon multivariate analysis, IONM changes were associated with POD (odds ratio 2.12; 95% CI 1.31-3.44; p < 0.001). Additionally, baseline EEG abnormalities were associated with POD (p = 0.002). CONCLUSION: Significant IONM changes are associated with an increased risk of POD in patients undergoing cardiovascular surgery. These findings offer a basis for future research and analysis of EEG and somatosensory evoked potential monitoring to predict, detect, and prevent POD.

Transcranial Motor Evoked Potentials as a Predictive Modality for Postoperative Deficit in Cervical Spine Decompression Surgery - A Systematic Review and Meta-Analysis.

STUDY DESIGN: Systematic Review and Meta-analysis. OBJECTIVE: The purpose of this study was to evaluate whether transcranial motor evoked potential (TcMEP) alarms can predict postoperative neurologic complications in patients undergoing cervical spine decompression surgery. METHODS: A meta-analysis of the literature was performed using PubMed, Web of Science, and Embase to retrieve published reports on intraoperative TcMEP monitoring for patients undergoing cervical spine decompression surgery. The sensitivity, specificity, and diagnostic odds ratio (DOR), of overall, reversible, and irreversible TcMEP changes for predicting postoperative neurological deficit were calculated. A subgroup analysis was performed to compare anterior vs posterior approaches. RESULTS: Nineteen studies consisting of 4608 patients were analyzed. The overall incidence of postoperative neurological deficits was 2.58% (119/4608). Overall TcMEP changes had a sensitivity of 56%, specificity of 94%, and DOR of 19.26 for predicting deficit. Reversible and irreversible changes had sensitivities of 16% and 49%, specificities of 95% and 98%, and DORs of 3.54 and 71.74, respectively. In anterior procedures, TcMEP changes had a DOR of 17.57, sensitivity of 49%, and specificity of 94%. In posterior procedures, TcMEP changes had a DOR of 21.01, sensitivity of 55%, and specificity of 94%. CONCLUSION: TcMEP monitoring has high specificity but low sensitivity for predicting postoperative neurological deficit in cervical spine decompression surgery. Patients with new postoperative neurological deficits were 19 times more likely to have experienced intraoperative TcMEP changes than those without new deficits, with irreversible TcMEP changes indicating a much higher risk of deficit than reversible TcMEP changes.

Electromyographic predictors of abducens nerve palsy after endoscopic skull base surgery.

OBJECTIVE: Recovery of abducens nerve palsy (ANP) after endoscopic endonasal skull base surgery (ESBS) has been shown to be potentially predicted by postoperative ophthalmological examination. Triggered electromyography (t-EMG) and free-run electromyography (f-EMG) activity provide an intraoperative assessment of abducens nerve function, but associations with long-term ANP outcomes have not been explored. The objective of this study was to describe intraoperative abducens EMG characteristics and determine whether these electrophysiological profiles are associated with immediately postoperative and long-term ANP outcomes after ESBS. METHODS: The authors conducted a 5-year (2011-2016) retrospective case-control study of patients who underwent ESBS in whom the abducens nerve was stimulated (t-EMG). Electrophysiological metrics were compared between patients with a new postoperative ANP (cases) and those without ANP (controls). Pathologies included chordoma, pituitary adenoma, meningioma, cholesterol granuloma, and chondrosarcoma. Electrophysiological data included the presence of abnormal f-EMG activity, t-EMG stimulation voltage, stimulation threshold, evoked compound muscle action potential (CMAP) amplitude, onset latency, peak latency, and CMAP duration at various stages of the dissection. Controls were selected such that pathologies were similarly distributed between cases and controls. RESULTS: Fifty-six patients were included, 26 with new postoperative ANP and 30 controls without ANP. Abnormal f-EMG activity (28.0% vs 3.3%, p = 0.02) and lack of response to stimulation (27% vs 0%, p = 0.006) were more frequent in patients with immediately postoperative ANP than in controls. Patients with immediately postoperative ANP also had a lower median CMAP amplitude (35.0 vs 71.2 µV, p = 0.02) and longer onset latency (5.2 vs 2.8 msec, p = 0.04). Comparing patients with transient versus persistent ANP on follow-up, those with persistent ANP tended to have a lower CMAP amplitude (12.8 vs 57 µV, p = 0.07) and higher likelihood of not responding to stimulation at the end of the case (45.5% vs 7.1%, p = 0.06). Abnormal f-EMG was not associated with long-term ANP outcomes. CONCLUSIONS: The presence of f-EMG activity, lack of CMAP response to stimulation, decreased CMAP amplitude, and increased CMAP onset latency were associated with immediately postoperative ANP. Long-term ANP outcomes may be associated with t-EMG parameters, including whether the nerve is able to be stimulated once identified and CMAP amplitude. Future prospective studies may be designed to standardize abducens nerve electrophysiological monitoring protocols to further refine operative and prognostic utility.

Utility of transcranial motor-evoked potential changes in predicting postoperative deficit in lumbar decompression and fusion surgery: a systematic review and meta-analysis.

PURPOSE: The primary aim of this study was to evaluate whether TcMEP alarms can predict the occurrence of postoperative neurological deficit in patients undergoing lumbar spine surgery. The secondary aim was to determine whether the various types of TcMEP alarms including transient and persistent changes portend varying degrees of injury risk. METHODS: This was a systematic review and meta-analysis of the literature from PubMed, Web of Science, and Embase regarding outcomes of transcranial motor-evoked potential (TcMEP) monitoring during lumbar decompression and fusion surgery. The sensitivity, specificity, and diagnostic odds ratio (DOR) of TcMEP alarms for predicting postoperative deficit were calculated and presented with forest plots and a summary receiver operating characteristic curve. RESULTS: Eight studies were included, consisting of 4923 patients. The incidence of postoperative neurological deficit was 0.73% (36/4923). The incidence of deficits in patients with significant TcMEP changes was 11.79% (27/229), while the incidence in those without changes was 0.19% (9/4694). All TcMEP alarms had a pooled sensitivity and specificity of 63 and 95% with a DOR of 34.92 (95% CI 7.95-153.42). Transient and persistent changes had sensitivities of 29% and 47%, specificities of 96% and 98%, and DORs of 8.04 and 66.06, respectively. CONCLUSION: TcMEP monitoring has high specificity but low sensitivity for predicting postoperative neurological deficit in lumbar decompression and fusion surgery. Patients who awoke with new postoperative deficits were 35 times more likely to have experienced TcMEP changes intraoperatively, with persistent changes indicating higher risk of deficit than transient changes. LEVEL OF EVIDENCE II: Diagnostic Systematic Review.

Diagnostic Accuracy of Somatosensory Evoked Potentials and Electroencephalography During Endovascular Treatment of Unruptured Cerebral Aneurysms.

OBJECTIVE: Endovascular treatment (EVT) of unruptured cerebral aneurysms (UCA) offers a safer alternative to clipping. However, it is still associated with an increased risk for Postprocedural Neurological deficit (PPND). Prompt recognition using intraoperative neurophysiologic monitoring (IONM) and intervention can reduce the incidence and impact of new postoperative neurological complications. We aim to evaluate the diagnostic accuracy of IONM in predicting PPND after EVT of UCA. METHODS: We included 414 patients who underwent EVT for UCA from 2014 to 2019. The sensitivities, specificities, and diagnostic odds ratio of somatosensory evoked potentials and electroencephalography monitoring methods were calculated. We also determined their diagnostic accuracy using receiver operating characteristic plots. RESULTS: The highest sensitivity of 67.7% (95% confidence interval {CI}, 34.9%-90.1%) was obtained when either modality had a change. Simultaneous changes in both modalities have the highest specificity of 97.8% (95% CI, 95.8%-99.0%). The area under the receiver operating characteristic curve was 0.795 (95% CI, 0.655-0.935) for changes in either modality. CONCLUSIONS: IONM with somatosensory evoked potentials alone or in combination with electroencephalography has high diagnostic accuracy in detecting periprocedural complications and resultant PPND during EVT of UCA.

POTENTIATION OF CORTICO-SPINAL OUTPUT VIA TARGETED ELECTRICAL STIMULATION OF THE MOTOR THALAMUS.

Cerebral white matter lesions prevent cortico-spinal descending inputs from effectively activating spinal motoneurons, leading to loss of motor control. However, in most cases, the damage to cortico-spinal axons is incomplete offering a potential target for new therapies aimed at improving volitional muscle activation. Here we hypothesized that, by engaging direct excitatory connections to cortico-spinal motoneurons, stimulation of the motor thalamus could facilitate activation of surviving cortico-spinal fibers thereby potentiating motor output. To test this hypothesis, we identified optimal thalamic targets and stimulation parameters that enhanced upper-limb motor evoked potentials and grip forces in anesthetized monkeys. This potentiation persisted after white matter lesions. We replicated these results in humans during intra-operative testing. We then designed a stimulation protocol that immediately improved voluntary grip force control in a patient with a chronic white matter lesion. Our results show that electrical stimulation targeting surviving neural pathways can improve motor control after white matter lesions.

Minimally invasive extraocular cranial nerve electromyography.

OBJECTIVE: A reluctance to monitor extraocular cranial nerve (EOCN) function has restricted skull base surgery worldwide. Spontaneous and triggered electromyography (EMG) monitoring can be recorded intraoperatively to identify and assess potential cranial nerve injury. Determining the conductive function of EOCNs requires the collection of clear, reliable, and repeatable compound muscle action potentials (CMAPs) secondary to stimulation. EOCN EMG needle electrodes can, although infrequently, cause ocular morbidity including hematoma, edema, and scleral laceration. The aim of this study was to ascertain if minimally invasive 7-mm superficial needle electrodes would record CMAPs as well as standard 13-mm intraorbital electrodes. METHODS: Conventionally, the authors have monitored EOCN function with intraorbital placement of paired 13-mm needle electrodes into three extraocular muscles: medial rectus, superior oblique, and lateral rectus. A prospective case-control study was performed using shorter (7-mm) needle electrodes. A single minimally invasive electrode was placed superficially near each extraocular muscle and coupled with a common reference. CMAPs were recorded from the minimally invasive electrodes and compared with CMAPs recorded from the paired intraorbital electrodes. The presence or absence of CMAPs was analyzed and compared among EMG recording techniques. RESULTS: A total of 429 CMAPs were analyzed from 71 EOCNs in 25 patients. The experimental setup yielded 167 true-positive (39%), 106 false-positive (25%), 17 false-negative (4%), and 139 true-negative (32%) responses. These values were used to calculate the sensitivity (91%), specificity (57%), positive predictive value (61%), and negative predictive value (89%). EOCN electrodes were placed in 82 total eyes in 58 patients (CMAPs were obtained in 25 patients). Twenty-six eyes showed some degree of edema, bruising, or bleeding, which was transient and self-resolving. Three eyes in different patients had complications from needle placement or extraction including conjunctival hemorrhage, periorbital ecchymosis, and corneal abrasion, ptosis, and upper eyelid edema. CONCLUSIONS: Because of artifact contamination, 106 false-positive responses (25%), and 17 false-negative responses (4%), the minimally invasive EMG technique cannot reliably record CMAP responses intraoperatively as well as the intraorbital technique. Less-invasive techniques can lead to an inaccurate EOCN assessment and potential postoperative morbidity. EOCN palsies can be debilitating and lifelong; therefore, the benefits of preserving EOCN function outweigh the potential risks of morbidity from electrode placement. EMG monitoring with intraorbital electrodes remains the most reliable method of intraoperative EOCN assessment.

Role of Intraoperative Neurophysiological Monitoring in Preventing Stroke After Cardiac Surgery.

BACKGROUND: Perioperative stroke after cardiac surgical procedures carries significant morbidity. Dual intraoperative neurophysiological monitoring with electroencephalography (EEG) and somatosensory-evoked potentials detects cerebral hypoperfusion and predicts postoperative stroke in noncardiac procedures. We further evaluated preoperative risk factors and intraoperative neuromonitoring ability to predict postoperative stroke after cardiac operations. METHODS: All patients who underwent cardiac operations with intraoperative neurophysiological monitoring from 2009 to 2020 at a single academic medical center were retrospectively analyzed. Patients with circulatory arrest were excluded. Risks factors analyzed were sex, age, tobacco use, hypertension, diabetes mellitus, dyslipidemia, atrial fibrillation, prior cerebrovascular accident, cerebrovascular disease, antiplatelet/anticoagulant use, abnormal somatosensory-evoked potentials and EEG baselines, and significant somatosensory-evoked potentials and EEG change as well as their permanence. Patients were divided into 2 groups by 30-day postoperative stroke occurrence. Univariate and multivariate logistical regressions were used for postoperative stroke significant predictors, and Kaplan-Meier curves estimated survival. RESULTS: The study included 620 patients (67.6% men), mean age 65.1 ± 14.1 years, with stroke in 5.32%. In univariate analysis, diabetes (odds ratio [OR], 2.62) and permanence of EEG change (OR, 5.35) were each associated with increased postoperative stroke odds. In multivariate analysis, diabetes (OR, 2.64) and permanent EEG change (OR, 4.22) were independently significantly associated with postoperative stroke. Overall survival was significantly better for patients with no intraoperative neurophysiological monitoring changes (P < .005). CONCLUSIONS: Permanent EEG change and diabetes were significant postoperative stroke predictors in cardiac operations. Furthermore, overall survival out to 10 years postoperatively was significantly higher in the group without intraoperative neurophysiological monitoring changes, emphasizing its important predictive role.

Predictive Value of Multimodality Intraoperative Neurophysiological Monitoring During Cardiac Surgery.

INTRODUCTION: This study aimed to determine the ability of multimodality intraoperative neurophysiologic monitoring, including somatosensory evoked potentials (SSEP) and EEG, to predict perioperative clinical stroke and stroke-related mortality after open-heart surgery in high-risk patients. METHODS: The records of all consecutive patients who underwent coronary artery bypass grafting, and cardiac valve repair/replacement with high risk for stroke who underwent both SSEP and EEG recording at the University of Pittsburgh Medical Center between 2009 and 2015 were reviewed. Sensitivity and specificity of these modalities to predict in-hospital clinical strokes and stroke-related mortality were calculated. RESULTS: A total of 531 patients underwent open cardiac procedures monitored using SSEP and EEG. One hundred thirty-one patients (24.67%) experienced significant changes in either modality. Fourteen patients (2.64%) suffered clinical strokes within 24 hours after surgery, and eight patients (1.50%) died during their hospitalization. The incidence of in-hospital clinical stroke and stroke-related mortality among patients who experienced a significant change in monitoring compared with those with no significant change was 11.45% versus 1.75%. The sensitivity and specificity of significant changes in either SSEP or EEG to predict in-hospital major stroke and stroke-related mortality were 0.93 and 0.77, respectively. CONCLUSIONS: Intraoperative neurophysiologic monitoring with SSEP and EEG has high sensitivity and specificity in predicting perioperative stroke and stroke-related mortality after open cardiac procedures. These results support the benefits of multimodality neuromonitoring during cardiac surgery.

Intraoperative neurophysiologic monitoring during aortic arch surgery.

OBJECTIVE: To evaluate the ability of intraoperative neurophysiologic monitoring (IONM) during aortic arch reconstruction with hypothermic circulatory arrest (HCA) to predict early (<48 hours) adverse neurologic events (ANE; stroke or transient ischemic attack) and operative mortality. METHODS: This was an observational study of aortic arch surgeries requiring HCA from 2010 to 2018. Patients were monitored with electroencephalogram (EEG) and somatosensory evoked potentials (SSEP). Baseline characteristics and postoperative outcomes were compared according to presence or absence of IONM changes, which were defined as any acute variation in SSEP or EEG, compared with baseline. Multivariable logistic regression analysis was used to assess the association of IONM changes with operative mortality and early ANE. RESULTS: A total of 563 patients underwent aortic arch reconstruction with HCA and IONM. Of these, 119 (21.1%) patients had an IONM change, whereas 444 (78.9%) did not. Patients with IONM changes had increased operative mortality (22.7% vs 4.3%) and increased early ANE (10.9% vs 2.9%). In multivariable analysis, SSEP changes were correlated with early ANE (odds ratio [OR], 4.68; 95% confidence interval [CI], 1.51-14.56; P = .008), whereas EEG changes were not (P = .532). Permanent SSEP changes were correlated with early ANE (OR, 4.56; 95% CI, 1.51-13.77; P = .007), whereas temperature-related SSEP changes were not (P = .997). Finally, any IONM change (either SSEP or EEG) was correlated with operative mortality (OR, 5.82; 95% CI, 2.72-12.49; P < .001). CONCLUSIONS: Abnormal IONM events during aortic arch reconstruction with HCA portend worse neurologic outcomes and operative mortality and have a negative predictive value of 97.1%. SSEP might be more sensitive than EEG for predicting early ANE, especially when SSEP changes are permanent.

Cardiovascular-related mortality after intraoperative neurophysiologic monitoring changes during carotid endarterectomy.

OBJECTIVE: We examined significant intraoperative neurophysiologic monitoring (IONM) changes and perioperative stroke as independent risk factors of long-term cardiovascular-related mortality in patients who have undergone carotid endarterectomy (CEA). METHODS: Records of patients who underwent CEA with IONM at the University of Pittsburgh Medical Center between January 1, 2009 and December 31, 2019 were analyzed retrospectively. Cardiovascular-related mortality was compared between the significant IONM change group and no IONM change group and between the perioperative stroke group and no perioperative stroke group. RESULTS: Our final cohort consisted of 2,090 patients. Patients with significant IONM changes showed nearly twice the rate of cardiovascular-related mortality up to 10 years post-CEA (hazard ratio (HR) = 1.98; 95% confidence interval (CI) [1.20 - 3.26]). Patients with perioperative stroke were four times more likely than patients without perioperative stroke to experience cardiovascular-related mortality (HR = 4.09; 95% CI [2.13 - 7.86]). CONCLUSIONS: Among CEA patients who underwent CEA and who experienced significant IONM changes or perioperative stroke, we observed long-term increased and sustained risk of cardiovascular-related mortality. SIGNIFICANCE: Significant IONM changes are valuable in predicting the risk of long-term outcomes following CEA.

Hyperdirect connectivity of opercular speech network to the subthalamic nucleus.

How the basal ganglia participate in the uniquely human behavior of speech is poorly understood, despite their known role in modulating critical aspects of cognitive and motor behavior. The subthalamic nucleus (STN) is well positioned to facilitate basal ganglia functions critical for speech. Using electrocorticography in patients undergoing awake deep brain stimulation (DBS) surgery, evidence is reported for a left opercular hyperdirect pathway in humans via stimulating the STN and examining antidromic-evoked activity in the left temporal, parietal, and frontal opercular cortex. These high-resolution cortical and subcortical mapping data provide evidence for hyperdirect connectivity between the inferior frontal gyrus and the STN. In addition, evoked potential data are consistent with the presence of monosynaptic projections from areas of the opercular speech cortex that are primarily sensory, including the auditory cortex, to the STN. These connections may be unique to humans, evolving alongside the ability for speech.

Triggered Electromyography is a Useful Intraoperative Adjunct to Predict Postoperative Neurological Deficit Following Lumbar Pedicle Screw Instrumentation.

STUDY DESIGN: Systematic review and meta-analysis. OBJECTIVES: Malposition of pedicle screws during instrumentation in the lumbar spine is associated with complications secondary to spinal cord or nerve root injury. Intraoperative triggered electromyographic monitoring (t-EMG) may be used during instrumentation for early detection of malposition. The association between lumbar pedicle screws stimulated at low EMG thresholds and postoperative neurological deficits, however, remains unknown. The purpose of this study is to assess whether a low threshold t-EMG response to lumbar pedicle screw stimulation can serve as a predictive tool for postoperative neurological deficit. METHODS: The present study is a meta-analysis of the literature from PubMed, Web of Science, and Embase identifying prospective/retrospective studies with outcomes of patients who underwent lumbar spinal fusion with t-EMG testing. RESULTS: The total study cohort consisted of 2,236 patients and the total postoperative neurological deficit rate was 3.04%. 10.78% of the patients incurred at least 1 pedicle screw that was stimulated below the respective EMG alarm threshold intraoperatively. The incidence of postoperative neurological deficits in patients with a lumbar pedicle screw stimulated below EMG alarm threshold during placement was 13.28%, while only 1.80% in the patients without. The pooled DOR was 10.14. Sensitivity was 49% while specificity was 88%. CONCLUSIONS: Electrically activated lumbar pedicle screws resulting in low t-EMG alarm thresholds are highly specific but weakly sensitive for new postoperative neurological deficits. Patients with new postoperative neurological deficits after lumbar spine surgery were 10 times more likely to have had a lumbar pedicle screw stimulated at a low EMG threshold.

Neurophysiological Characteristics of Cranial Nerves V- and VII-Triggered EMG in Endoscopic Endonasal Approach Skull Base Surgery.

Objective This study proposes to present reference parameters for trigeminal (V) and facial (VII) cranial nerves (CNs)-triggered electromyography (tEMG) during endoscopic endonasal approach (EEA) skull base surgeries to allow more precise and accurate mapping of these CNs. Study Design We retrospectively reviewed EEA procedures performed at the University of Pittsburgh Medical Center between 2009 and 2015. tEMG recorded in response to stimulation of CN V and VII was analyzed. Analysis of tEMG waveforms included latencies and amplitudes. Medical records were reviewed to determine the presence of perioperative neurologic deficits. Results A total of 28 patients were included. tEMG from 34 CNs (22 V and 12 VII) were analyzed. For CN V, the average onset latency was 2.9 ± 1.1 ms and peak-to-peak amplitude was 525 ± 436.94 µV ( n = 22). For CN VII, the average onset latency and peak-to-peak amplitude were 5.1 ± 1.43 ms and 315 ± 352.58 µV for the orbicularis oculi distribution ( n = 09), 5.9 ± 0.67 ms and 517 ± 489.07 µV on orbicularis oris ( n = 08), and 5.3 ± 0.98 ms 303.1 ± 215.3 µV on mentalis ( n = 07), respectively. Conclusion Our data support the notion that onset latency may be a feasible parameter in the differentiation between the CN V and VII during the crosstalk phenomenon in EEA surgeries but the particularities of this type of procedure should be taken into consideration. A prospective analysis with a larger data set is necessary.

Diagnostic Accuracy of SSEP Changes During Lumbar Spine Surgery for Predicting Postoperative Neurological Deficit: A Systematic Review and Meta-Analysis.

STUDY DESIGN: This study is a meta-analysis of prospective and retrospective studies identified in PubMed, Web of Science, and Embase with outcomes of patients who received intraoperative somatosensory-evoked potential (SSEP) monitoring during lumbar spine surgery. OBJECTIVE: The objective of this study is to determine the diagnostic accuracy of intraoperative lower extremity SSEP changes for predicting postoperative neurological deficit. As a secondary analysis, we evaluated three subtypes of intraoperative SSEP changes: reversible, irreversible, and total signal loss. SUMMARY OF BACKGROUND DATA: Lumbar decompression and fusion surgery can treat lumbar spinal stenosis and spondylolisthesis but carry a risk for nerve root injury. Published neurophysiological monitoring guidelines provide no conclusive evidence for the clinical utility of intraoperative SSEP monitoring during lumbar spine surgery. METHODS: A systematic review was conducted to identify studies with outcomes of patients who underwent lumbar spine surgeries with intraoperative SSEP monitoring. The sensitivity, specificity, and diagnostic odds ratio (DOR) were calculated and presented with forest plots and a summary receiver operating characteristic curve. RESULTS: The study cohort consisted of 5607 patients. All significant intraoperative SSEP changes had a sensitivity of 44% and specificity of 97% with a DOR of 22.13 (95% CI, 11.30-43.34). Reversible and irreversible SSEP changes had sensitivities of 28% and 33% and specificities of 97% and 97%, respectively. The DORs for reversible and irreversible SSEP changes were 13.93 (95% CI, 4.60-40.44) and 57.84 (95% CI, 15.95-209.84), respectively. Total loss of SSEPs had a sensitivity of 9% and specificity of 99% with a DOR of 23.91 (95% CI, 7.18-79.65). CONCLUSION: SSEP changes during lumbar spine surgery are highly specific but moderately sensitive for new postoperative neurological deficits. Patients who had postoperative neurological deficit were 22 times more likely to have exhibited intraoperative SSEP changes.Level of Evidence: 2.

Optimal "Low" Pedicle Screw Stimulation Threshold to Predict New Postoperative Lower-Extremity Neurologic Deficits During Lumbar Spinal Fusions.

OBJECTIVE: Previous studies have shown that pedicle screw stimulation thresholds ≤6-8 mA yield a high diagnostic accuracy of detecting misplaced screws. Our objective was to determine the optimal "low" stimulation threshold to predict new postoperative neurologic deficits and identify additional risk factors associated with deficits. METHODS: We included patients with complete pedicle screw stimulation testing who underwent posterior lumbar spinal fusion surgeries from 2010-2012. We calculated the diagnostic accuracy of pedicle screw responses of ≤4 mA, ≤6 mA, ≤8 mA, ≤10 mA, ≤12 mA, and ≤20 mA to predict new postoperative lower-extremity (LE) neurologic deficits. We used multivariate modeling to determine the best logistic regression model to predict LE deficits and identify additional risk factors. Statistics software packages used were Python3.8.5, NumPy 1.19.1, Pandas 1.1.1, and SPSS26. RESULTS: We studied 1179 patients who underwent 8584 pedicle screw stimulations with somatosensory evoked potential and free-run electromyographic monitoring for posterior lumbar spinal fusion. Twenty-five (2.1%) patients had new LE neurologic deficits. A stimulation threshold of ≤8 mA had a sensitivity/specificity of 32%/90% and a diagnostic odds ratio/area under the curve of 4.34 [95% confidence interval: 1.83, 10.27]/0.61 [0.49, 0.74] in predicting postoperative deficit. Multivariate analysis showed that patients who had pedicle screws with stimulation thresholds ≤8 mA are 3.15 [1.26, 7.83]× more likely to have postoperative LE deficits while patients who have undergone a revision lumbar spinal fusion surgery are 3.64 [1.38, 9.61]× more likely. CONCLUSIONS: Our results show that low thresholds are indicative of not only screw proximity to the nerve but also an increased likelihood of postoperative neurologic deficit. Thresholds ≤8 mA prove to be the optimal "low" threshold to help guide a correctly positioned pedicle screw placement and detect postoperative deficits.

What is the predictive value of intraoperative somatosensory evoked potential monitoring for postoperative neurological deficit in cervical spine surgery?-a meta-analysis.

BACKGROUND CONTEXT: Cervical decompression and fusion surgery remains a mainstay of treatment for a variety of cervical pathologies. Potential intraoperative injury to the spinal cord and nerve roots poses nontrivial risk for consequent postoperative neurologic deficits. Although neuromonitoring with intraoperative somatosensory evoked potentials (SSEPs) is often used in cervical spine surgery, its therapeutic value remains controversial. PURPOSE: The purpose of the present study was to evaluate whether significant SSEP changes can predict postoperative neurologic complications in cervical spine surgery. A subgroup analysis was performed to compare the predictive power of SSEP changes in both anterior and posterior approaches. STUDY DESIGN: The present study was a meta-analysis of the literature from PubMed, Web of Science, and Embase to identify prospective/retrospective studies with outcomes of patients who underwent cervical spine surgeries with intraoperative SSEP monitoring. PATIENT SAMPLE: The total cohort consisted of 7,747 patients who underwent cervical spine surgery with intraoperative SSEP monitoring. METHODS: Inclusion criteria for study selection were as follows: (1) prospective or retrospective cohort studies, (2) studies conducted in patients undergoing elective cervical spine surgery not due to aneurysm, tumor, or trauma with intraoperative SSEP monitoring, (3) studies that reported postoperative neurologic outcomes, (4) studies conducted with a sample size ≥20 patients, (5) studies with only adult patients ≥18 years of age, (6) studies published in English, (7) studies inclusive of an abstract. OUTCOME MEASURES: The sensitivity, specificity, diagnostic odds ratio (DOR), and likelihood ratios of overall SSEP changes, reversible SSEP changes, irreversible SSEP changes, and SSEP loss for predicting postoperative neurological deficit were calculated. RESULTS: The total rate of postoperative neurological deficits was 2.50% (194/7,747) and the total rate of SSEP changes was 7.36% (570/7,747). The incidence of postoperative neurological deficit in patients with intraoperative SSEP changes was 16.49% (94/570) while only 1.39% (100/7,177) in patients without. All significant intraoperative SSEP changes had a sensitivity of 46.0% and specificity of 96.7% with a DOR of 27.32. Reversible and irreversible SSEP changes had sensitivities of 17.7% and 37.1% and specificities of 97.5% and 99.5%, respectively. The DORs for reversible and irreversible SSEP changes were 9.01 and 167.90, respectively. SSEP loss had a DOR of 51.39, sensitivity of 17.3% and specificity 99.6%. In anterior procedures, SSEP changes had a DOR of 9.60, sensitivity of 34.2%, and specificity of 94.7%. In posterior procedures, SSEP changes had a DOR of 13.27, sensitivity of 42.6%, and specificity of 94.0%. CONCLUSIONS: SSEP monitoring is highly specific but weakly sensitive for postoperative neurological deficit following cervical spine surgery. The analysis found that patients with new postoperative neurological deficits were nearly 27 times more likely to have had significant intraoperative SSEP change. Loss of SSEP signals and irreversible SSEP changes seem to indicate a much higher risk of injury than reversible SSEP changes.

Diagnostic Accuracy of Thresholds Less Than or Equal to 8 mA in Pedicle Screw Testing During Lumbar Spine Procedures to Predict New Postoperative Lower Extremity Neurological Deficits.

STUDY DESIGN: Retrospective observational study. OBJECTIVE: It has been shown that pedicle screw stimulation thresholds less than or equal to 8 mA yield a very high diagnostic accuracy of detecting misplaced screws in spinal surgery. In our study, we determined clinical implications of low stimulation thresholds. SUMMARY OF BACKGROUND DATA: Posterior lumbar spinal fusions (PSF), using pedicle screws, are performed to treat many spinal pathologies, but misplaced pedicle screws can result in new postoperative neurological deficits. METHODS: Patients with pedicle screw stimulation testing who underwent PSF between 2010 and 2012 at the University of Pittsburgh Medical Center (UPMC) were included in the study. We evaluated the sensitivity, specificity, and diagnostic odds ratio (DOR) to determine how effectively low pedicle screw responses predict new postoperative lower extremity neurological deficits. RESULTS: One thousand one hundred seventy nine eligible patients underwent 8584 pedicle screw stimulations with lower extremity somatosensory evoked potentials (LE SSEP) monitoring for lumbar fusion surgery. One hundred twenty one of these patients had 187 pedicle screws with a stimulation response at a threshold less than or equal to 8 mA. Smoking had a significant correlation to pedicle screw stimulation less than or equal to 8 mA (P = 0.012). A threshold of less than or equal to 8 mA had a sensitivity/specificity of 0.32/0.90 with DOR of 4.34 [1.83, 10.27] and an area under the ROC curve (AUC) of 0.61 [0.49, 0.74]. Patients with screw thresholds less than or equal to 8 mA and abnormal baselines had a DOR of 9.8 [95% CI: 2.13-45.17] and an AUC of 0.73 [95% CI: 0.50-0.95]. CONCLUSION: Patients with pedicle screw stimulation thresholds less than or equal to 8 mA are 4.34 times more likely to have neurological clinical manifestations. Smoking and LE deficits were shown to be significantly correlated with pedicle screw stimulation thresholds less than or equal to 8 mA. Low stimulation thresholds result in a high specificity of 90%. Pedicle screw stimulation less than or equal to 8 mA can serve as an accurate rule in test for postoperative neurological deficit, warranting reevaluation of screw placement and/or replacement intraoperatively.Level of Evidence: 3.