Effect of dexmedetomidine on somatosensory- and motor-evoked potentials in patients receiving craniotomy under propofol-sevoflurane combined anesthesia.

Introduction: Dexmedetomidine is often used as an adjunct to total intravenous anesthesia (TIVA) for procedures requiring intraoperative neurophysiologic monitoring (IONM). However, it has been reported that dexmedetomidine might mask the warning of a neurological deficit on intraoperative monitoring. Methods: We reviewed the intraoperative neurophysiological monitoring data of 47 patients who underwent surgery and IONM from March 2019 to March 2021 at the Department of Neurosurgery, Renmin Hospital of Wuhan University. Pre- and postoperative motor function scores were recorded and analyzed. Dexmedetomidine was administered intravenously at 0.5 µg/kg/h 40 min after anesthesia and discontinued after 1 h in the dexmedetomidine group. Results: We found that the amplitude of transcranial motor-evoked potentials (Tce-MEPs) was significantly lower in the dexmedetomidine group than in the negative control group (P < 0.0001). There was no statistically significant difference in the somatosensory-evoked potentials (SSEPs) amplitude or the Tce-MEPs or SSEPs latency. There was no significant decrease in postoperative motor function in the dexmedetomidine group compared with the preoperative group, suggesting that there is no evidence that dexmedetomidine affects patient prognosis. In addition, we noticed a synchronized bilateral decrease in the Tce-MEPs amplitude in the dexmedetomidine group and a mostly unilateral decrease on the side of the brain injury in the positive control group (P = 0.001). Discussion: Although dexmedetomidine does not affect the prognosis of patients undergoing craniotomy, the potential risks and benefits of applying it as an adjunctive medication during craniotomy should be carefully evaluated. When dexmedetomidine is administered, Tce-MEPs should be monitored. When a decrease in the Tce-MEPs amplitude is detected, the cause of the decrease in the MEPs amplitude can be indirectly determined by whether the decrease is bilateral.

Diagnostic Accuracy of Somatosensory Evoked Potential and Transcranial Motor Evoked Potential in Detection of Neurological Injury in Intradural Extramedullary Spinal Cord Tumor Surgeries: A Short-Term Follow-Up Prospective Interventional Study Experience from Tertiary Care Center of India.

Objective Intraoperative neuromonitoring (IONM) is an acknowledged tool for real-time neuraxis assessment during surgery. Somatosensory evoked potential (SSEP) and transcranial motor evoked potential (MEP) are commonest deployed modalities of IONM. Role of SSEP and MEP in intradural extramedullary spinal cord tumor (IDEMSCT) surgery is not well established. The aim of this study was to evaluate sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and transcranial MEP, in detection of intraoperative neurological injury in IDEMSCT patients as well as their postoperative limb-specific neurological improvement assessment at fixed intervals till 30 days. Materials and Methods Symptomatic patients with IDEMSCTs were selected according to the inclusion criteria of study protocol. On modified McCormick (mMC) scale, their sensory-motor deficit was assessed both preoperatively and postoperatively. Surgery was done under SSEP and MEP (transcranial) monitoring using appropriate anesthetic agents. Gross total/subtotal resection of tumor was achieved as per IONM warning alarms. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and MEP were calculated considering postoperative neurological changes as "reference standard." Patients were followed up at postoperative day (POD) 0, 1, 7, and 30 for convalescence. Statistical Analysis With appropriate tests of significance, statistical analysis was carried out. Receiver-operating characteristic curve was used to find cutoff point of mMC for SSEP being recordable in patients with higher neurological deficit along with calculation of sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and MEP for prediction of intraoperative neurological injury. Results Study included 32 patients. Baseline mean mMC value was 2.59. Under neuromonitoring, gross total resection of IDEMSCT was achieved in 87.5% patients. SSEP was recordable in subset of patients with mMC value less than or equal to 2 with diagnostic accuracy of 100%. MEP was recordable in all patients and it had 96.88% diagnostic accuracy. Statistically significant neurological improvement was noted at POD-7 and POD-30 follow-up. Conclusion SSEP and MEP individually carry high diagnostic accuracy in detection of intraoperative neurological injuries in patients undergoing IDEMSCT surgery. MEP continues to monitor the neuraxis, even in those subsets of patients where SSEP fails to record.

The Role of Spinal Cord Compression in Predicting Intraoperative Neurophysiological Monitoring Events in Patients With Kyphotic Deformity: A Magnetic Resonance Imaging-Based Study.

OBJECTIVE: To establish a novel classification system for predicting the risk of intraoperative neurophysiological monitoring (IONM) events in surgically-treated patients with kyphotic deformity. METHODS: Patients with kyphotic deformity who underwent surgical correction of cervicothoracic, thoracic, or thoracolumbar kyphosis in our center from July 2005 to December 2020 were recruited. We proposed a classification system to describe the morphology of the spinal cord on T2-weighted sagittal magnetic resonance imaging: type A, circular/symmetric cord with visible cerebrospinal fluid (CSF) between the cord and vertebral body; type B, circular/oval/symmetric cord with no visible CSF between the cord and vertebral body; type C, spinal cord that is fattened/deformed by the vertebral body, with no visible CSF between the cord and vertebral body. Furthermore, based on type C, the spinal cord compression ratio (CR) < 50% was defined as the subtype C-, while the spinal cord CR ≥ 50% was defined as the subtype C+. IONM event was documented, and a comparative analysis was made to evaluate the prevalence of IONM events among patients with diverse spinal cord types. RESULTS: A total of 294 patients were reviewed, including 73 in type A; 153 in type B; 53 in subtype C- and 15 in subtype C+. Lower extremity transcranial motor-evoked potentials and/or somatosensory evoked potentials were lost intraoperatively in 41 cases (13.9%), among which 4 patients with type C showed no return of spinal cord monitoring data. The 14 subtype C+ patients (93.3%) had IONM events. Univariate logistic regression analysis showed that patients with a type C spinal cord (subtype C-: odds ratio [OR], 10.390; 95% confidence interval [CI], 2.215-48.735; p = 0.003; subtype C+, OR, 497.000; 95% CI, 42.126- 5,863.611; p < 0.001) are at significantly higher risk of a positive IONM event during deformity correction compared to those with a type A. In further multiple logistic regression analysis, the spinal cord classification (OR, 5.371; 95% CI, 2.966-9.727; p < 0.001) was confirmed as an independent risk factor for IONM events. CONCLUSION: We presented a new spinal cord classification system based on the relative position of the spinal cord and vertebrae to predict the risk of IONM events in patients with kyphotic deformity. In patients with type C spinal cord, especially those in C+ cases, it is essential to be aware of potential IONM events, and adopt standard operating procedures to facilitate neurological recovery.

Role of Intraoperative Electroencephalography in Predicting Postoperative Delirium in Patients Undergoing Cardiovascular Surgeries.

OBJECTIVE: To determine the utility of electroencephalography (EEG) in predicting postoperative delirium (POD) in patients who underwent cardiovascular surgeries with EEG monitoring. METHODS: A total of 1161 patients who underwent cardiovascular surgeries with EEG monitoring were included in the study, and their data were retrospectively reviewed. POD assessment was done utilizing Intensive Care Delirium Screening Checklist (ICDSC). Patients with a score of > 4 on ICDSC were diagnosed with POD. RESULTS: Of 1161 patients, 131 patients had EEG changes and 56 (42.74%) of 131 patients experienced POD. Of 1030 patients without EEG changes, 219 (21.26%) experienced POD. EEG showed specificity of 91.5% and negative predictive value of 78.7% in detecting POD. On multivariable analysis, EEG changes showed a strong association with POD (ORadj 1.97 CI (1.30-2.99), p = 0.001) with persistent EEG changes showing even a higher risk of developing POD (ORadj 2.65 (1.43-4.92), p = 0.002). CONCLUSION: EEG change has specificity of 91.5% emphasizing the need for its implementation as a diagnostic tool for predicting POD. Patients with POD are two times more likely to experience significant EEG changes, especially persistent EEG changes when undergoing cardiovascular surgeries. SIGNIFICANCE: Intraoperative EEG can detect POD, and EEG changes based therapeutic interventions can mitigate POD.

An updated protocol for mandibular reconstruction in nongrowing patients with craniofacial microsomia with temporomandibular joint total prosthesis.

The authors aim to present an updated protocol for mandibular reconstruction in nongrowing patients with Pruzansky/Kaban type IIb/III congenital craniofacial microsomia with customized temporomandibular joint (TMJ) prosthesis to reduce facial nerve (FN) damage and improve surgical accuracy. This is illustrated (using 3 cases) and is based on preoperative mapping of the FN using MRI for better virtual surgical planning of custom-made TMJ prosthesis. Intraoperative FN mapping and monitoring, as well as verification of the final result with intraoperative cone-beam computed tomography (CBCT) and 3D-reconstructed images is also achieved. All 3 patients presented mild transient postoperative facial palsy due to surgical soft tissue stretching which resolved within 2 months of surgery. All patients presented proper occlusion and mouth opening without pain, with an average incisal opening of 38.8 mm (range 35.5-42 mm) at two months of follow-up. Moreover, superposition of intraoperative and preoperative 3D reconstruction images ensured surgical accuracy and avoided the need for a potential reintervention. In conclusion, the proposed surgical protocol for mandibular reconstruction with customized alloplastic TMJ prosthesis in nongrowing patients with type IIb/III Pruzansky-Kaban congenital mandibular hypoplasia may reduce FN morbidity, improve surgical accuracy and final outcomes.

A Prospective Look at the Prevalence of Setup Electrode-Swap Errors Across Over 450 Intraoperative Neuromonitoring Cases.

Intraoperative neurophysiological monitoring (IONM) is shown to be useful in surgeries when the nervous system is at risk. Its success in part relies upon proper setup of often dozens of electrodes correctly placed and secured upon patients and inserted in specific stimulating and recording receptacles. Given the complicated setups and the demanding operating room environment, errors in setup are bound to occur. These have led to false negatives associated with new patient morbidities including, at times, paralysis. No studies quantify the prevalence of these types of setup errors. Approximately 800,000 operations annually utilize intraoperative neuromonitoring in the US alone, so even a small percentage of errors suggests clinical significance. In addition, these types of errors hinder the overall effectiveness of IONM and may result in lower reported sensitivities and lower cost-effectiveness of this important service. We sought to discover through a prospective study and verification through chart review the prevalence of "electrode-swap" errors (when recording and/or stimulating electrodes are incorrectly placed on the patient or in the IONM equipment during setup) across all procedures monitored. We found recording and/or stimulating electrode set up errors in 24 of 454 cases (5.3%). These data and examples of how errors were discovered intraoperatively are reported. We also offer techniques to help reduce this error rate. This study demonstrates a significant potential avoidable error in IONM diagnostic utility, patient outcome, and sensitivity/specificity of alert criteria. The value of identifying and correcting these errors is consequential, multifaceted, and far-reaching.

An institutional experience of intraoperative neurophysiological monitoring application in robotic thyroidectomy: a retrospective case-control study.

Purpose: Intraoperative neurophysiological monitoring (IONM) has been introduced in thyroid surgery to prevent injury of the recurrent laryngeal nerve (RLN). However, its effectiveness remains controversial in robotic thyroidectomy (RT). This study aimed to compare the surgical outcome of RT in patients with and without the application of IONM. Methods: This retrospective case-control study included 100 patients who underwent total thyroidectomy via robotic bilateral axillo-breast approach in a tertiary center. A study group of 50 patients who had IONM during RT was compared to a control group of 50 patients who underwent RT with nerve visualization alone. Results: The sex ratio (4:45 vs. 7:43, P = 0.538), mean age (39.3 ± 7.1 years vs. 37.5 ± 10.4 years, P = 0.304), and body mass index (23.1 ± 2.6 kg/m2 vs. 22.2 ± 3.9 kg/m2, P = 0.215) were comparable between the IONM and control groups. Pathologic features including tumor size (0.8 cm vs. 0.9 cm, P = 0.283), extrathyroidal extension (58.0% vs. 24.0%, P = 0.316), lymph node metastasis (30% vs. 34%, P = 0.668), and number of lymph nodes (5.3 vs. 5.3, P = 0.668) showed no differences. There was no permanent RLN palsy, postoperative bleeding, and wound complications. Transient hypoparathyroidism was observed in 12 (24.0%) and 14 (28.0%), permanent hypoparathyroidism in 0 (0%) and 1 (2.0%), and transient RLN palsy was observed in 3 (6.0%) and 3 (6.0%), respectively. Conclusion: We did not demonstrate a clear advantage of IONM in RT. Controversies regarding the effectiveness of IONM is not closed.

Intraoperative Neurophysiological Monitoring in Neurosurgery.

Intraoperative neurophysiological monitoring (IONM) is a crucial advancement in neurosurgery, enhancing procedural safety and precision. This technique involves continuous real-time assessment of neurophysiological signals, aiding surgeons in timely interventions to protect neural structures. In addition to inherent limitations, IONM necessitates a detailed anesthetic plan for accurate signal recording. Given the growing importance of IONM in neurosurgery, we conducted a narrative review including the most relevant studies about the modalities and their application in different fields of neurosurgery. In particular, this review provides insights for all physicians and healthcare professionals unfamiliar with IONM, elucidating commonly used techniques in neurosurgery. In particular, it discusses the roles of IONM in various neurosurgical settings such as tumoral brain resection, neurovascular surgery, epilepsy surgery, spinal surgery, and peripheral nerve surgery. Furthermore, it offers an overview of the anesthesiologic strategies and limitations of techniques essential for the effective implementation of IONM.

There's No "I" in "Team": Recommendations for Effective Teamwork and Communication in IONM.

Effective teamwork is essential in almost every job, and can even mean life, death, or disability in some jobs. Intraoperative neurophysiological monitoring (IONM) is a career in which effective teamwork and accurate communication are of utmost importance, yet it comes with a unique set of challenges in which to achieve those goals. Operating rooms can be very stressful environments, even if a surgical neurophysiologist (SNP) works in the same hospital every day. Often an SNP is required to travel from hospital to hospital and work with different teams each day. In addition, communication with the IONM oversight professional (IONM-P) can be challenging by nature of the telemedicine model which is becoming the most commonly applied IONM model in the United States. It is unfortunate that such critical skills are assumed and are rarely formally trained. In this article, we present evidence-based recommendations for establishing effective team function. We also provide several tools designed to help create effective and efficient teams. Teams cannot function at their best without outstanding communication, so improving teamwork also means improving communication. This article also provides several techniques for excellent communication, regardless of the situation or context.

The application value and improved warning criterion of D-wave monitoring in intramedullary spinal cord tumor surgery.

BACKGROUND CONTEXT: The primary treatment method for intramedullary spinal cord tumor (IMSCT) is surgical resection, but this procedure carries a significant risk of neurological damage. Intraoperative neurophysiological monitoring (IONM) has become a necessary adjunctive tool for IMSCT resection. PURPOSE: The current study aimed to explore the application value of D-wave monitoring in IMSCT surgery, and tried to investigate a tailored criterion for its early warning. STUDY DESIGN: A retrospective clinical study. PATIENT SAMPLE: A retrospective analysis was conducted based on the data of patients who underwent IMSCT surgeries performed by the same neurosurgical team at our hospital. IONM was applied in all surgeries. According to inclusion and exclusion criteria, ultimately 90 patients were enrolled in the study. OUTCOME MEASURES: The McCormick Scale (MMS) was applied to assess the functional outcome through outpatient visits or telephone follow-up at one month and six months postoperatively. Patients with an MMS grade over II one month after surgery were considered to have newly developed postoperative motor dysfunction (PMD). If the MMS grade could be restored to I or II six months after surgery, it was defined as a short-term PMD. Otherwise, it was defined as a long-term PMD. METHODS: The predictive value of different IONM modalities, including somatosensory evoked potential (SEP), muscle motor evoked potential (MEP), and D-wave for PMD, was assessed with sensitivity, specificity, positive predictive value, negative predictive value, and subsequent logistic regression analysis. At last, the cut-off value of the D-wave amplitude reduction ratio for predicting PMD was obtained through the receiver operating characteristic (ROC) curve analysis. RESULTS: SEP showed the worst performance in predicting short-term and long-term PMD. Significant MEP changes were indicated as an independent predictive factor for short-term PMD (OR 5.062, 95% CI 1.947-13.166, p=.001), while D-wave changes were demonstrated as an independent predictor for long-term PMD (OR 339.433, 95% CI 11.337-10770.311, p=.001). The optimum cut-off value of the D-wave amplitude reduction ratio for predicting long-term PMD was 42.18%, with a sensitivity of 100% and a specificity of 93.8% (AUC=0.981, p<.001). CONCLUSIONS: D-wave monitoring showed extremely high specificity in predicting PMD compared to SEP and MEP monitoring. Moreover, the authors suggested that a D-wave amplitude reduction of over 40% during IMSCT surgery generally indicates long-term PMD for patients.

Application value of intraoperative electrophysiological monitoring in cerebral eloquent area glioma surgery: a retrospective cohort study.

INTRODUCTION: Surgery for gliomas involving eloquent areas is a very challenging microsurgical procedure. Maximizing both the extent of resection (EOR) and preservation of neurological function have always been the focus of attention. Intraoperative neurophysiological monitoring (IONM) is widely used in this kind of surgery. The purpose of this study was to evaluate the efficacy of IONM in eloquent area glioma surgery. METHODS: Sixty-eight glioma patients who underwent surgical treatment from 2014 to 2019 were included in this retrospective cohort study, which focused on eloquent areas. Clinical indicators and IONM data were analysed preoperatively, two weeks after surgery, and at the final follow-up. Logistic regression, Cox regression, and Kaplan‒Meier analyses were performed, and nomograms were then established for predicting prognosis. The diagnostic value of the IONM indicator was evaluated by the receiver operating characteristic (ROC) curve. RESULTS: IONM had no effect on the postoperative outcomes, including EOR, intraoperative bleeding volume, duration of surgery, length of hospital stay, and neurological function status. However, at the three-month follow-up, the percentage of patients who had deteriorated function in the monitored group was significantly lower than that in the unmonitored group (23.3% vs. 52.6%; P < 0.05). Logistic regression analysis showed that IONM was a significant factor in long-term neurological function (OR = 0.23, 95% CI (0.07-0.70). In the survival analysis, long-term neurological deterioration indicated worsened overall survival (OS) and progression-free survival (PFS). A prognostic nomogram was established through Cox regression model analysis, which could predict the probability 3-year survival rate. The concordance index was 0.761 (95% CI 0.734-0.788). The sensitivity and specificity of IONM evoked potential (SSEP and TCeMEP) were 0.875 and 0.909, respectively. In the ROC curve analysis, the area under the curve (AUC) for the SSEP and TCeMEP curves was 0.892 (P < 0.05). CONCLUSIONS: The application of IONM could improve long-term neurological function, which is closely related to prognosis and can be used as an independent prognostic factor. IONM is practical and widely available for predicting postoperative functional deficits in patients with eloquent area glioma.

Quality of Postoperative Recovery in Total Intravenous Anesthesia between Remimazolam and Propofol for Intraoperative Neurophysiological Monitoring: A Prospective Double-Blind Randomized Controlled Trial.

This study compared the overall postoperative recovery of patients who underwent total intravenous anesthesia with remimazolam or propofol, using the Quality of Recovery-15 questionnaire (QoR-15). Seventy-two patients who underwent spine surgery with intraoperative neurophysiological monitoring (IONM) were randomly categorized into the remimazolam group (group R) or propofol group (group P). On the first postoperative day, the QoR-15 scores for groups P and R were 114 and 112, respectively, indicating no significant difference (p = 0.691). Similarly, group-time interaction effects on QoR-15 scores were not significantly different. In the post-anesthesia care unit, the pain intensity at rest was notably higher in group P than in group R (3.0 [0.0] vs. 2.8 [0.5], respectively, p = 0.009). Although the intraoperative consumption of remifentanil was higher in group R (1452.4 µg vs. 2066.8 µg, respectively, p < 0.001), the intraoperative use of vasopressors was lower in group R (1705.6 µg vs. 286.1 µg, respectively, p < 0.001) compared to group P. Group R exhibited significantly lower variability in mean blood pressure over time compared to group P. Remimazolam was viewed as a promising intravenous agent for general anesthesia, showing potential to replace propofol in spine surgery with IONM, considering both recovery quality and intraoperative hemodynamic stability.

Advancing Intraoperative Neurophysiological Monitoring With Human Reflexes.

Human reflexes are simple motor responses that are automatically elicited by various sensory inputs. These reflexes can provide valuable insights into the functioning of the nervous system, particularly the brainstem and spinal cord. Reflexes involving the brainstem, such as the blink reflex, laryngeal adductor reflex, trigeminal hypoglossal reflex, and masseter H reflex, offer immediate information about the cranial-nerve functionality and the overall state of the brainstem. Similarly, spinal reflexes such as the H reflex of the soleus muscle, posterior root muscle reflexes, and sacral reflexes provide crucial information about the functionality of the spinal cord and peripheral nerves. One of the critical benefits of reflex monitoring is that it can provide continuous feedback without disrupting the surgical process due to no movement being induced in the surgical field. These reflexes can be monitored in real time during surgical procedures to assess the integrity of the nervous system and detect potential neurological damage. It is particularly noteworthy that the reflexes provide motor and sensory information on the functional integrity of nerve fibers and nuclei. This article describes the current techniques used for monitoring various human reflexes and their clinical significance in surgery. We also address important methodological considerations and their impact on surgical safety and patient outcomes. Utilizing these methodologies has the potential to advance or even revolutionize the field of intraoperative continuous monitoring, ultimately leading to improved surgical outcomes and enhanced patient care.

Aborted AIS spinal fusion due to persistent loss of IONM: which patients are at greatest risk?

PURPOSE: Determine peri-operative risk factors predictive for prematurely stopping surgery prior to completion of deformity correction due to intra-operative neuromonitoring changes. METHODS: A single institution retrospective review of adolescent idiopathic scoliosis (AIS) patients that underwent spinal fusion for curves greater than 70°. Cases aborted due to persistent loss of IONM were compared to completed cases. Demographic, radiographic, neurologic, and surgical information was reviewed. RESULTS: There were 453 total cases. Nine (9/453: (2%)) cases were aborted due to persistent loss of IONM, and 4 (4/453; (0.88%)) awoke with a neurologic deficit. Comparing to the 444 completed cases, pre-operative risk factors associated with case abortion were older age (15.3 vs. 13.8 years; p = 0.02), sex (male) (66.7% vs. 20.3%, p = 0.004), and larger cobb angles (87.6° vs. 79.2°; p = 0.01). Being male increased the risk of case abortion: 7.9X. Intraoperative risk factors associated with case abortion were combined anterior/posterior approach (ASF/PSF) (44.4% vs. 7.2%; p = 0.003) and increased index procedure EBL (1127 vs. 769 mL; p = 0.043). ASF/PSF increased the risk: 10.3X. Four (4/9;44%) of the aborted cases awoke with neurologic deficit. Motor strength returned at 2.3 days (0-18). Aborted cases returned to the OR after 12.6 ± 7.0 days (1-23) which was related to time to regain motor strength. CONCLUSION: Pre-operative risk factors for AIS case abortion due to persistent loss of IOMN are older age, males, with larger Cobb angles. Intraoperative risk factors are combined ASF/PSF and increased index procedure EBL. Independent risk factors were sex (male) and ASF/PSF which increased the risk 7.9X and 10.3X, respectively.

The feasibility and technical aspects of trigemino-cervical reflex elicitation in humans under general anesthesia.

OBJECTIVE: To analyze the feasibility, neurophysiological aspects, stimulation patterns, and topographic distribution of trigemino-cervical reflex (TCR) components in humans under general anesthesia. METHODS: This prospective observational study enrolled 20 participants who underwent posterior fossa surgery, surgical proceduresin thecraniovertebral junction,or spinal cord surgery. TCR responses were simultaneously recorded in the sternocleidomastoid (SCM) and trapezius muscles after electrical stimulation of the supraorbital and infraorbital nerves. TCR responses were recorded preoperatively and intraoperatively using single-pulse and multipulse (trains of 2-7 electrical stimuli) stimulation, respectively. Two stimulus duration patterns were evaluated: 0.2-0.5 ms and 0.5-1.0 ms. RESULTS: Intraoperatively, short- and long-latency TCR components were obtained in the SCM ipsilateral to the stimulation with variable recordability. Short-latency responses were the most commonly recorded components. A longer stimulus duration (0.5-1.0 ms) seems to favor the elicitation of TCR responses under general anesthesia. CONCLUSIONS: Short-latency components recorded in the SCM ipsilateral to the stimulation could be regularly elicited under general anesthesia when a larger stimulus duration (0.5-1.0 ms) was applied. SIGNIFICANCE: This is the first study to demonstrate the elicitation of TCR components in humans under general anesthesia. This neurophysiological technique can potentially optimize intraoperative neurophysiological monitoring during brainstem surgery.

Cortico-cortical evoked potentials of language tracts in minimally invasive glioma surgery guided by Penfield stimulation.

OBJECTIVE: We investigated the feasibility of recording cortico-cortical evoked potentials (CCEPs) in patients with low- and high-grade glioma. We compared CCEPs during awake and asleep surgery, as well as those stimulated from the functional Broca area and recorded from the functional Wernicke area (BtW), and vice versa (WtB). We also analyzed CCEP properties according to tumor location, histopathology, and aphasia. METHODS: We included 20 patients who underwent minimally invasive surgery in an asleep-awake-asleep setting. Strip electrode placement was guided by classical Penfield stimulation of positive language sites and fiber tracking of the arcuate fascicle. CCEPs were elicited with alternating monophasic single pulses of 1.1 Hz frequency and recorded as averaged signals. Intraoperatively, there was no post-processing of the signal. RESULTS: Ninety-seven CCEPs from 19 patients were analyzed. There was no significant difference in CCEP properties when comparing awake versus asleep, nor BtW versus WtB. CCEP amplitude and latency were affected by tumor location and histopathology. CCEP features after tumor resection correlated with short- and long-term postoperative aphasia. CONCLUSION: CCEP recordings are feasible during minimally invasive surgery. CCEPs might be surrogate markers for altered connectivity of the language tracts. SIGNIFICANCE: This study may guide the incorporation of CCEPs into intraoperative neurophysiological monitoring.

Motor-Evoked Potential Monitoring With Multi-train Electrical Stimulation During Thoracoabdominal Aortic Aneurysm Surgery: A Case Report.

Intraoperative motor-evoked potentials (MEPs) are measured for assessing motor function during surgery. MEP monitoring is often performed in thoracoabdominal aortic aneurysm (TAAA) surgery, but false positives are common and amplification methods are needed to obtain waveforms under severe conditions to assess proper spinal cord function. One method of amplitude amplification in transcranial-stimulated MEP monitoring is multitrain stimulation. There are few reports on multitrain-stimulated MEP monitoring for this surgery. A 57-year-old woman underwent open repair of the thoracoabdominal aorta due to a dissecting aortic aneurysm. After opening the chest, the aneurysm was incised proximally, and anastomosis with an artificial vessel was initiated. The lumbar artery leading to the Adam-Kiewicz artery was reconstructed at a body temperature of 25 °C. However, the single-train stimulation did not produce MEPs. When the measurement was switched to multitrain stimulation, MEPs were elicited in the lower extremity muscle groups and the waveforms were maintained until the end of the measurement. This case illustrates that MEP monitoring using multitrain stimulation during descending thoracic aortic aneurysm surgery can effectively elicit MEPs under challenging conditions, in which conventional single-train stimulation may be insufficient.

Application of Intraoperative Neurophysiological Monitoring (IONM) for Preventing Dysphagia After Anterior Cervical Surgery: A Prospective Study.

OBJECTIVE: To evaluate the clinical value of intraoperative nerve monitoring (IONM) for dysphagia after anterior cervical surgery with and without IONM. METHODS: A prospective, randomized, controlled study was conducted on 46 patients who underwent anterior cervical spine surgery by an experienced orthopaedic surgeon. Twenty-three patients who underwent anterior cervical surgery did not undergo IONM (non-IONM group), while the other 23 patients who underwent anterior cervical surgery did ("IONM group"). The swallowing function of patients was evaluated using the EAT-10 and endoscopic evaluation of swallowing (FEES) after surgery. RESULTS: There was no difference in the incidence of swallowing difficulties between the intervention group and the control group on the third day or sixth week after surgery. At the 12th week after surgery, the incidence of swallowing difficulties in the intervention group and the control group was significantly different (43.5% vs. 13.0%, P = 0.024). CONCLUSIONS: IONM is a promising tool for identifying and protecting the spinal cord and nerves during anterior cervical surgery. Our research revealed that IONM significantly reduced the occurrence of swallowing disorders 12 weeks after surgery, but the effect was not significant at the third or sixth week after surgery.

Temporal Analysis of Postoperative Outcomes With or Without Intraoperative Motor Evoked Potentials and Somatosensory Evoked Potentials Monitoring for Intracranial Meningioma Surgery.

BACKGROUND: This study aimed to retrospectively assess results of intracranial meningioma surgery with or without intraoperative neuromonitoring (IONM) in a single institution. METHODS: Two cohorts (a historical cohort and a monitoring cohort) were collected for the analysis. Before IONM was introduced, a total of 107 patients underwent intracranial meningioma operation without IONM from January 2000 to December 2008 by one neurosurgeon (historical cohort). After IONM was introduced, a total of 99 patients with intracranial meningioma were operated under IONM between November 2018 and February 2023 by two neurosurgeons (monitoring cohort). A retrospective comparison was made on the complications from meningioma surgery between the two groups. RESULTS: In the monitoring cohort, warning signals of motor evoked potential (MEPs) or somatosensory evoked potential (SSEPs) were alarmed in 10 patients. Two of these 10 patients aborted the operation and eight of these 10 patients with warning signals underwent tumor resection. Of these eight patients, five showed postoperative morbidity. Five of 89 patients without warning signals developed neurological deficits. In the historical cohort, 14 of 107 patients showed postoperative morbidity or mortality. CONCLUSION: Even after successful resection of intracranial meningiomas prior to the advent of IONM, integration of MEPs and SSEPs monitoring yielded valuable insights for surgical teams during operative procedures.