Changes In Somatosensory Evoked Potentials Research Articles

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...

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

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 (≤ 21years). 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. 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. Intraoperative SSEP monitoring can predict perioperative neurological injury and improve surgical outcomes in pediatric scoliosis fusion surgery. 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 .

Multimodal Intraoperative Neurophysiological Monitoring in Cranial and Spinal Tumour Surgeries: A Descriptive Observational Study.

Intraoperative neurophysiological monitoring (IONM) involves monitoring the functional integrity of critical brain regions and pathways as well as identifying and preserving functionally viable neural tissues (mapping) during surgery using electrophysiological techniques. Multimodality combines various neurophysiological techniques to optimise diagnostic effectiveness and to improve the outcomes of the surgeries. The present study is a case series with comprehensive and illustrative descriptions of the neurophysiological changes in five neuromonitored cases of cranial and spinal cord tumour surgeries conducted with a multimodal approach. The cases were monitored with somatosensory evoked potentials (SSEP), transcranial motor evoked potentials (TcMEP), and both free run and triggered electromyography (fEMG and tEMG). No false negative outcomes were identified in the cases studied as there was an association of absence of change in SSEP and TcMEP both, with no neurological deficit postoperatively.Two cases were identified as having true positive neuromonitoring alerts.No false positive alerts were found in any case. Multimodal monitoring using SSEP, TcMEP, and EMG (fEMG and tEMG) in cranial and spinal tumour surgeries can improve performance with fewer false-negative and false-positive results. Neuromonitoring approaches used in combination can provide reliable information regarding postoperative neurological outcomes.

Abstract 036: Diagnostic Accuracy of IONM for Perioperative Strokes during Endovascular Treatment of Ruptured Intracranial Aneurysms

Introduction Ruptured aneurysmal SAH accounts up to 80% of nontraumatic SAH, with more than 80% located in the anterior circulation and a mortality rate upwards of 50%.1‐3 Endovascular treatment (EVT) of ruptured intracranial aneurysms (rIA) is increasingly being recognized as a standard treatment that may result in better early outcomes and independency when compared with open neurosurgical clipping in cases of appropriate equipoise.1,2,4–6 Despite this, EVT of intracranial aneurysms has its own risk of complications including intraoperative rupture and thromboembolic events.7 The complication rate is found to be higher in cases of rIA than that seen in cases of unruptured intracranial aneurysms.8 The use of somatosensory evoked potentials (SSEP) and electroencephalography (EEG) intraoperative neuromonitoring (IONM) have proven their efficacy in identifying iatrogenic neurological complications in vascular surgeries including carotid endarterectomy 9–11, EVT and microsurgical treatment of intracranial aneurysms. 11,12 rIA have their own unique challenges due to preoperative neurological deficits and perioperative vasospasm making it more difficult to identify new neurological deficits after the procedure. They are also associated with decreased vasoreactivity secondary to bleeding, and a higher rate of procedural complications that can alter the IONM signals.13,14 IONM in the form of SSEP and EEG can be utilized in anesthetized patients to indirectly monitor intraoperative cerebral perfusion as well as central and peripheral neuronal integrity.15,16 Changes in one or both modalities indicate a change in cerebral perfusion that can be related to EVT directly, for example, aneurysm perforation or coil herniation and embolism, or indirectly secondary to anesthesia and hemodynamic changes.17 (Figure1) Methods We reviewed the medical records of 323 patients who underwent EVT of ruptured aneurysms with IONM utilizing SSEP and EEG. We included all patients who had endovascular management of ruptured aneurysm and completed IONM records until the end of the procedure and excluded those with no IONM records or incomplete records. Patients were divided into 2 groups, one group with postprocedural neurological deficits (PPND) and one group without PPND. Results Total of 323 patients undergoing EVT, significant IONM changes were noted in 71 patients (21.98%) and 46 (14.24%) who experienced PPND. 22 out of 71 (30.98%) patients who had significant IONM changes experienced PPND. Univariable analysis demonstrated that persistent changes in SSEP and EEG were associated with PPND (p‐values: <0.001 and <0.001). Multivariable analysis showed that persistent IONM changes were significantly associated with PPND (OR: 8.28 (95%CI:2.92‐24.66, p‐value: <0.001). Simultaneous changes in both modalities had a specificity of 95% (95% CI: 0.92, 0.97%) and sensitivity of 48% (95% CI: 0.33, 0.63) to predict PPND when either modality had a change. Out of 46 patients with PPND, 29 (63.04%) experienced periprocedural complications. PPND was associated with periprocedural complications with a p‐value <0.001. Also, multivariable analysis showed an association between IONM changes and persistent IONM changes with PPND with OR of 7.35 (95% CI; 3.68, 15.03) and 7.25 (95% CI; 3.58, 15.00), respectively. Conclusion Significant IONM changes during EVT for rIA are associated with an increased risk of PPND.

A Novel Paired Somatosensory-Cerebellar Stimulation Induces Plasticity on Cerebellar-Brain Connectivity

The cerebellum receives and integrates a large amount of sensory information that is important for motor coordination and learning. The aim of the present work was to investigate whether peripheral nerve and cerebellum paired associative stimulation (cPAS) could induce plasticity in both the cerebellum and the cortex. In a cross-over design, we delivered right median nerve electrical stimulation 25 or 10 ms before applying transcranial magnetic stimulation over the cerebellum. We assessed changes in motor evoked potentials (MEP), somatosensory evoked potentials (SEP), short-afferent inhibition (SAI), and cerebellum-brain inhibition (CBI) immediately, and 30 min after cPAS. Our results showed a significant reduction in CBI 30 minutes after cPAS, with no discernible changes in MEP, SEP, and SAI. Notably, cPAS10 did not produce any modulatory effects on these parameters. In summary, cPAS25 demonstrated the capacity to induce plasticity effects in the cerebellar cortex, leading to a reduction in CBI. This novel intervention may be used to modulate plasticity mechanisms and motor learning in healthy individuals and patients with neurological conditions.

Diagnostic Accuracy of Somatosensory Evoked Potential monitoring during Scoliosis correction surgery in the pediatric population: A Systematic Review (P7-4.002)

<h3>Objective:</h3> To evaluate the diagnostic accuracy of intraoperative somatosensory evoked potential (SSEP) monitoring in predicting the risk of perioperative neurological outcomes during scoliosis fusion surgery for idiopathic scoliosis (IS) in the pediatric age group (≤ 21 years). <h3>Background:</h3> Scoliosis correction surgery is the most effective treatment for pediatric IS. However, new neurological deficits during the surgery can potentially affect the outcomes of this surgery. Intraoperative neuromonitoring techniques like SSEP provide real-time information about the spinal cord and nerve roots and can be used as a reliable indicator to predict perioperative neurological deficits. <h3>Design/Methods:</h3> A systematic review of various databases to find literature on pediatric IS patients who underwent scoliosis correction with intraoperative neuromonitoring. Data collection included study design, patient demographics, procedure, neuromonitoring modalities, SSEP alarm criteria, SSEP changes (including reversible and irreversible changes), and perioperative neurological deficit. We calculated the sensitivity, specificity, and diagnostic odds ratio (DOR) of SSEP changes (total, transient, and persistent) and SSEP loss for predicting perioperative neurological deficits. <h3>Results:</h3> We included eighteen studies for our final analysis, with a total cohort of 4674 children. The incidence of a significant SSEP change was 3.1% (145/4674), while the incidence of a new neurological deficit was 1.01% (47/4674). The incidence of new neurological deficits in children with an intraoperative SSEP change was 28.28% (41/145), while it was 0.13% (6/4529) in children without an SSEP change. SSEP changes had a sensitivity of 72%, specificity of 97%, and DOR of 98.64, while SSEP loss had a sensitivity of 42%, specificity of 99.3%, and a DOR of 143.76 for predicting new neurologic deficit. Transient and Persistent SSEP changes had sensitivities of 37% and 39%, specificities of 97% and 99.2%, and DORs of 18.09 and 75.43, respectively. <h3>Conclusions:</h3> Intraoperative SSEP monitoring can predict perioperative neurological injury and help improve the surgical outcomes in pediatric scoliosis fusion surgery. <b>Disclosure:</b> Dr. Gorijala has nothing to disclose. Dr. Shaik has nothing to disclose. The institution of Dr. Thirumala has received research support from University of Pittsburgh. Dr. Anetakis has nothing to disclose. Jeffery Balzer has nothing to disclose. Donald Crammond has nothing to disclose. Dr. Shandal has nothing to disclose. Dr. Lee has nothing to disclose. The institution of Dr. Shaw has received research support from LSRS. The institution of Dr. Shaw has received research support from CSRS. The institution of Dr. Shaw has received research support from AO Spine. Dr. Shaw has received intellectual property interests from a discovery or technology relating to health care. Mr. Reddy has nothing to disclose.

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

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

Intraoperative neuromonitoring in spine surgery: Does it reduce neural complications? Current evidence

The objectives were to review the evidence on whether intraoperative neurophysiological monitoring (IONM) sensitively and specifically detects intraoperative neurologic injury during spine surgery and whether it reduces neurological complications in spine surgery. A systematic literature review and meta-analysis were conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and studies spanning 1990–2022 were searched. The diagnostic accuracy of somatosensory evoked potentials (SSEPs) and motor-evoked potential (MEP) in predicting postoperative neurologic outcomes in spine surgery was assessed. We also analyzed clinical comparative studies that compared patients who underwent spine surgery with and without IONM to determine the rate of new neurologic events. Fifty studies that provided exact SSEP or MEP changes and postoperative neurological outcomes were analyzed. The features of SSEP changes included low sensitivity (67.7%), high specificity (94.1%), and strong negative predictive value (NPV) (92.1%). For the assessed alarm criteria of a 50% reduction, a 65% reduction, an 80% reduction in amplitude, and a total signal loss, the sensitivity and specificity values for MEP were 87.4%, 100%, 100%, and 100%, and 94.8%, 97%, 94.5%, and 90.5%, respectively. A random effects model was used to assess six research that compared neurological events with and without the use of IONM. The pooled Odds ratio was 0.5746 (confidence interval = 0.48; 0.67), z = 6.637, and the P value was 0.0001. The usefulness of IONM in detecting neurological events during spine surgery is well demonstrated by a growing body of research. However, prospective trials with high-level data are lacking to establish its efficacy in preventing new neurological deficits.

Efficacy of functional electrical stimulation in rehabilitating patients with foot drop symptoms after stroke and its correlation with somatosensory evoked potentials—a crossover randomised controlled trial

ObjectiveThe connectivity between somatosensory evoked potentials (SEPs) and cortical plasticity remains elusive due to a lack of supporting data. This study investigates changes in pathological latencies and amplitudes of SEPs caused by an acute stroke after 2 weeks of rehabilitation with functional electrical stimulation (FES). Furthermore, changes in SEPs and the efficacy of FES against foot drop (FD) stroke symptoms were correlated using the 10-m walk test and foot–ankle strength.MethodsA randomised controlled two-period crossover design plus a control group (group C) was designed. Group A (n = 16) was directly treated with FES, while group B (n = 16) was treated after 2 weeks. The untreated control group of 20 healthy adults underwent repeated SEP measurements for evaluation only.ResultsThe repeated-measures ANOVA showed a decrease in tibial nerve (TN) P40 and N50 latencies in group A after the intervention, followed by a decline in non-paretic TN SEP in latency N50 (p < 0.05). Moreover, compared to groups B and C from baseline to 4 weeks, group A showed a decrease in paretic TN latency P40 and N50 (p < 0.05). An increase in FD strength and a reduction in step cadence in group B (p < 0.05) and a positive tendency in FD strength (p = 0.12) and step cadence (p = 0.08) in group A were observed after the treatment time. The data showed a moderate (r = 0.50–0.70) correlation between non-paretic TN latency N50 and step cadence in groups A and B after the intervention time.ConclusionThe FES intervention modified the pathological gait in association with improved SEP afferent feedback.Registered on 25 February 2021 on ClinicalTrials.gov under identifier number: NCT04767360.

Effect of whole-hand water flow stimulation on the neural balance between excitation and inhibition in the primary somatosensory cortex.

Sustained peripheral somatosensory stimulations, such as high-frequency repetitive somatosensory stimulation (HF-RSS) and vibrated stimulation, are effective in altering the balance between excitation and inhibition in the somatosensory cortex (S1) and motor cortex (M1). A recent study reported that whole-hand water flow (WF) stimulation induced neural disinhibition in the M1. Based on previous results, we hypothesized that whole-hand WF stimulation would lead to neural disinhibition in the S1 because there is a strong neural connection between M1 and S1 and aimed to examine whether whole-hand WF stimulation would change the neural balance between excitation and inhibition in the S1. Nineteen healthy volunteers were studied by measuring excitation and inhibition in the S1 before and after each of the four 15-min interventions. The excitation and inhibition in the S1 were assessed using somatosensory evoked potentials (SEPs) and paired-pulse inhibition (PPI) induced by single- and paired-pulse stimulations, respectively. The four interventions were as follows: control, whole-hand water immersion, whole-hand WF, and HF-RSS. The results showed no significant changes in SEPs and PPI following any intervention. However, changes in PPI with an interstimulus interval (ISI) of 30 ms were significantly correlated with the baseline value before whole-hand WF. Thus, the present findings indicated that the whole-hand WF stimulation had a greater decreased neural inhibition in participants with higher neural inhibition in the S1 at baseline. Considering previous results on M1, the present results possibly show that S1 has lower plasticity than M1 and that the duration (15 min) of each intervention may not have been enough to alter the balance of excitation and inhibition in the S1.

Therapeutic benefits of noninvasive somatosensory cortex stimulation on cortical plasticity and somatosensory function: A systematic review.

Optimal limb coordination requires efficient transmission of somatosensory information to the sensorimotor cortex. The primary somatosensory cortex (S1) is frequently damaged by stroke, resulting in both somatosensory and motor impairments. Noninvasive brain stimulation (NIBS) to the primary motor cortex is thought to induce neural plasticity that facilitates neurorehabilitation. Several studies have also examined if NIBS to the S1 can enhance somatosensory processing as assessed by somatosensory-evoked potentials (SEPs) and improve behavioural task performance, but it remains uncertain if NIBS can reliably modulate S1 plasticity or even whether SEPs can reflect this plasticity. This systematic review revealed that NIBS has relatively minor effects on SEPs or somatosensory task performance, but larger early SEP changes after NIBS can still predict improved performance. Similarly, decreased paired-pulse inhibition in S1 post-NIBS is associated with improved somatosensory performance. However, several studies still debate the role of inhibitory function in somatosensory performance after NIBS in terms of the direction of the change (i.e., disinhibition or inhibition). Altogether, early SEP and paired-pulse inhibition (particularly inter-stimulus intervals of 30-100 ms) may become useful biomarkers for somatosensory deficits, but improved NIBS protocols are required for therapeutic applications.

Intraoperative neurophysiological monitoring during urgent surgical extracranial internal carotid artery recanalization

ObjectiveThe clinical outcome of surgical extracranial internal carotid artery (eICA) recanalization may be adversely affected by intraoperative ischemia. Median nerve somatosensory evoked potential (SEP) amplitude correlates well with cerebral blood flow.Our study presents the value of intraoperative SEP and selective shunting in the prevention of intraoperative ischemia development during urgent eICA recanalization. MethodsProspective recruitment of patients with acute unilateral eICA occlusion. All underwent surgical recanalization with intraoperative monitoring of scalp median SEPs. Preoperative clinical findings, cerebral collaterals, and 3 month functional outcome were evaluated. ResultsThe cohort consisted of 33 patients. Intraoperative SEP amplitude decreased significantly in 6 (18.2%). An intraluminal shunt was inserted twice (6.1%), surgical complications occurred in 6 (18.2%), intracerebral hemorrhage was not found.Favorable outcome 3 months after surgery according to the modified Rankin scale (mRS 0–2) was achieved in 28 (84.8%), 3 patients died (9.1%). ConclusionsIntraoperative SEP during urgent eICA recanalization seems to be beneficial.Thanks to the effective measure based on the intraoperative SEP changes, the clinical outcome in four(12.1%) could be positively affected. SignificanceThe results suggest that selective shunting based on intraoperative median SEPs may prevent intraoperative ischemia and may improve overall outcome of urgent eICA recanalization.

Abstract TP83: Benefit Of Multimodal Intraoperative Neuromonitoring Techniques During Carotid Procedures

Background: Carotid intervention is done for reduction of stroke risk. Intraoperative neuromonitoring (IOM), including electroencephalography (EEG), somatosensory evoked potential (SSEP), and cerebral oximetry/near-infrared spectroscopy (NIRS) may be used to guide operative decision-making and minimize the risk of perioperative complications. The utility of combining IOM methods is unclear. Therefore, we sought to investigate the value of multimodal IOM for carotid interventions. Methods: A retrospective review of all patients undergoing carotid intervention from January 1, 2012 to December 31, 2019 at a single academic medical center was done. Patients with acute stroke undergoing catheter directed thrombectomy were excluded. Data collected included: patient demographics, IOM parameters, surgical intervention with endpoints of 30-day post-operative complications. Surrogate end-points of IOM change and intraoperative hemodynamic interventions were also assessed. Efficacy and diagnostic value of each IOM modality alone, and in combination, were assessed using multivariable logistic regression. Results: 409 carotid interventions in 311 patients meeting inclusion criteria were identified. Patients were 63.3% male, 36.7% female, 83.4% white, 7.1% Hispanic, and 5.9% other. 162(39.6%) interventions were performed for ipsilateral symptoms including 111(27.1%) ipsilateral stroke, 91(22.3%) TIA. Use of a single versus multiple IOM modalities was not associated with a reduction in post-operative neurologic events. Changes in SSEP demonstrated a 2.97 odds ratio for predicting neurologic adverse events (AE), though this was not statistically significant. Conclusion: IOM changes were associated with an increase in AEs but IOM impact on intraoperative changes in surgical plans were infrequent. It is unclear whether IOM had a significant impact on procedural modifications though this may reflect an underpowered sample size. The low impact of IOM on outcome raises the question of cost-effectiveness of these techniques in reducing intraoperative complications from carotid procedures.

Predictive Value of Multimodality Intraoperative Neurophysiological Monitoring During Cardiac Surgery.

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. 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. 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. 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.

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

Intraoperative neurophysiologic monitoring during aortic arch surgery

ObjectiveTo 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. MethodsThis 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. ResultsA 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). ConclusionsAbnormal 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.

Effect of thoracic spinal cord injury on forelimb somatosensory evoked potential

In this paper, we investigate the forelimbs somatosensory evoked potential (SSEP) signals, which are representative of the integrity of ascending sensory pathways and their stability as well as function, recorded from corresponding cortices, post thoracic spinal cord injury (SCI). We designed a series of distinctive transection SCI to investigate whether forelimbs SSEPs change after right T10 hemi-transection, T8 and T10 double hemi-transection and T8 complete transection in rat model of SCI. We used electrical stimuli to stimulate median nerves and recorded SSEPs from left and right somatosensory areas of both cortices. We monitored pre-injury baseline and verified changes in forelimbs SSEP signals on Days 4, 7, 14, and 21 post-injury. We previously characterized hindlimb SSEP changes for the abovementioned transection injuries. The focus of this article is to investigate the quality and quantity of changes that may occur in the forelimb somatosensory pathways post-thoracic transection SCI. It is important to test the stability of forelimb SSEPs following thoracic SCI because of their potential utility as a proxy baseline for the traumatic SCIs in clinical cases wherein there is no opportunity to gather baseline of the lower extremities. We observed that the forelimb SSEP amplitudes increased following thoracic SCI but gradually returned to the baseline. Despite changes found in the raw signals, statistical analysis found forelimb SSEP signals become stable relatively soon. In summary, though there are changes in value (with p > 0.05), they are not statistically significant. Therefore, the null hypothesis that the mean of the forelimb SSEP signals are the same across multiple days after injury onset cannot be rejected during the acute phase.

A novel approach of using brachial plexus blockade as an experimental model for diagnosis of intraoperative nerve dysfunction with somatosensory evoked potentials: a blinded proof-of-concept study.

Intraoperative nerve dysfunction has been difficult to investigate because of its rarity and unpredictable occurrence. The diagnostic test attributes of nerve function monitors have not been clearly defined. This proof-of-concept study aimed to assess the feasibility of using brachial plexus blockade (BPB) in awake patients as an experimental model for nerve dysfunction to characterize the diagnostic test attributes of somatosensory evoked potentials (SSEPs). We obtained baseline SSEPs and neurologic function in patients and subsequently placed BPBs (experimental model) to generate progressive states of nerve dysfunction. We monitored SSEP changes (index test) and neurologic symptoms (reference standard) simultaneously during the onset of BPB to determine the temporal relationships and diagnostic test attributes of SSEPs. Brachial plexus blockade produced differential motor and sensory dysfunction that allowed simultaneous clinical and neurophysiologic assessment. One hundred and fifty-seven pairs of multiple data points from 14 patients were included for final analysis. The onset of abnormal SSEP signals almost always preceded the onset of neurologic symptoms. The sensitivities and specificities of SSEP to detect the impairment of power (motor rating score ≤ 4/5), cold sensation, and two-point discrimination were 100% and 67%, 99% and 55%, and 100% and 46%, respectively. This study found that BPB can produce sufficient differential nerve dysfunction to allow adequate evaluation of the diagnostic test attributes of SSEPs as a nerve monitor. The results of this study may stimulate further work on refining intraoperative nerve dysfunction models and diagnostic nerve function monitors. www.clinicaltrials.gov (NCT03409536); registered 24 January 2018.

Efficacy of evoked potential monitoring for predicting postoperative motor status in internal carotid artery aneurysm surgeries.

This study aimed to investigate the efficacy of intraoperative motor evoked potential (MEP) and somatosensory evoked potential (SSEP) monitoring for predicting postoperative motor deficits (PMDs) in patients with internal carotid artery (ICA) aneurysms. The data for 138 patients with ICA aneurysms who underwent surgical clipping as well as their intraoperative neuromonitoring data were retrospectively reviewed. The efficacy of MEP/SSEP changes for predicting PMDs was assessed using binary logistic regression analysis. Subsequently, receiver operating characteristic curve analysis was used to obtain a supplementary critical value of the MEP/SSEP deterioration duration. The sensitivity and specificity of MEP changes for predicting PMDs were 0.824 and 0.843, respectively. For SSEP changes, the sensitivity and specificity were 0.529 and 0.959, respectively. MEP and SSEP changes were identified as independent predictors for short-term (p = 0.002 and 0.011, respectively) and long-term PMDs (p = 0.040 and 0.006, respectively). The supplementary critical value for MEP deterioration duration for predicting PMDs was 14min (p = 0.007, AUC = 0.805). For SSEP, the value was 14.5min (p = 0.042, AUC = 0.875). The MEP/SSEP changes adjusted by those optimal values were also identified as independent predictors for short-term (p < 0.001 and p = 0.005, respectively) and long-term PMDs (p = 0.019 and 0.003, respectively). Intraoperative MEP and SSEP deterioration durations are effective in predicting PMDs in patients with ICA aneurysms.

Comparison of Intraoperative Neuromonitoring Outcome in Treating Thoracic Ossification of the Ligamentum Flavum Through En Bloc Versus Piecemeal Laminectomy.

A retrospective cohort analysis. The aim of this study was to investigate the impact of piecemeal versus en bloc laminectomies on spinal cord in thoracic ossification of ligamentum flavum (TOLF) through intraoperative changes of motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SEPs). Surgical treatment is indicated for symptomatic TOLF, and both piecemeal and en bloc laminectomies are commonly used methods. However, few studies compared both intraoperative interference and prognostic impact of these two laminectomies on spinal cord in TOLF patients. MEPs were recorded from abductor hallucis (AH) and tibialis anterior, and SEPs were performed on tibial nerve in 55 TOLF patients (piecemeal vs. en bloc: 23 vs. 32). Patients were categorized based on MEP/SEP improvement, deterioration, and no change, and MEP/SEP improvement rates were measured in the improvement group. Additionally, all patients were assessed by American Spinal Injury Association (ASIA) scores, Ashworth scores, and modified Japanese Orthopedic association (mJOA) scores before and after operation. The incidences of both MEP/SEP improvement and deterioration were similar between the two laminectomy groups (P > 0.05), and no significant difference is noted in both MEP and SEP amplitudes between the baseline and different critical manipulations in both laminectomy groups (P > 0.05). In the improvement group, patients receiving en bloc laminectomy exhibited increased improvement rates of both MEPs in bilateral AH and left-side SEPs compared to piecemeal laminectomy (P < 0.05). Clinically, all functional scales clearly improved in both laminectomy groups after operation (P < 0.05), and postoperative 1-year mJOA improvement rates were highly correlated with MEP improvement rates (P < 0.05). Intraoperative changes of MEPs and SEPs potentially provide a valid method for quantitatively evaluating the safety of different intraoperative manipulations and their prognostic impacts on spinal cord. Both laminectomies are safe and effective methods to treat TOLF, and en bloc laminectomy may cause relatively better spinal cord functional recovery.Level of Evidence: 3.