Key points for protecting the external branch of the superior laryngeal nerve in open thyroidectomy: A possible exploration technique.

OBJECTIVE: Injury of the external branch of the superior laryngeal nerve (EBSLN) is easily overlooked in thyroidectomy, and voice changes caused by the injury have a negative effect on an increasing number of patients. This study aimed to reduce the injury rate of EBSLN by expanding the sternothyroid-laryngeal triangle and standardizing the exploration procedure. METHODS: A total of 520 patients who had undergone thyroidectomy at the First Affiliated Hospital of Nanchang University between September 2021 and April 2022 were analyzed. During the operation, the exposure rate of the EBSLN before and after sternothyroid-laryngeal triangle expansion was compared, and all EBSLNs were anatomically classified. RESULTS: The exposure rate of EBSLN after sternothyroid-laryngeal triangle expansion reached 82.7%, which is much higher than that before sternothyroid-laryngeal triangle expansion (33.7%), and voice change caused by injury of the EBSLN was reported in one case (the injury rate was 0.2%). The classification and proportion of the EBSLN were as follows: Type 1 (55.3%), the nerve ran within 1 cm above the STP, but no coincidence or crossover with blood vessels was observed in this region; Type 2 (14.7%), the nerve travelled within 1 cm above the STP and overlapped or intersected with blood vessels in this region; Type 3 (12.7%), the EBSLN ran below the level of the STP; and Type 4 (17.3%), no EBSLN was observed within 1 cm above the STP. CONCLUSION: In thyroidectomy, injury to the EBSLN can be effectively reduced by expanding the sternothyroid-laryngeal triangle and exploring the upper pole area of the thyroid as far as possible, which has great clinical significance in reducing postoperative voice box injury.

The weepy cry - short neural signal bursts in intraoperative neuromonitoring.

PURPOSE: This study aimed to establish an in-vitro alternative to existing in-vivo systems to analyze nerve dysfunction using continuous neuromonitoring (C-IONM). METHODS: Three hundred sixty-three recurrent laryngeal nerves (RLN) (N(pigs) = 304, N(cattle) = 59) from food industry cadavers were exposed by microsurgical dissection following euthanasia. After rinsing with Ringer's lactate, they were tempered at 22 °C. Signal evaluation using C-IONM was performed for 10 min at 2 min intervals, and traction forces of up to 2N were applied for a median time of 60 s. Based on their post-traumatic electrophysiological response, RLNs were classified into four groups: Group A: Amplitude ≥ 100%, Group B: loss of function (LOS) 0-25%, Group C: ≥ 25-50%, and Group D: > 50%. RESULTS: A viable in-vitro neuromonitoring system was established. The median post-traumatic amplitudes were 112%, 88%, 59%, and 9% in groups A, B, C, and D, respectively. A time-dependent further dynamic LOS was observed during the 10 min after cessation of strain. Surprisingly, following initial post-traumatic hyperconductivity, complete LOS occurred in up to 20% of the nerves in group A. The critical threshold for triggering LOS was 2N in all four groups, resulting in immediate paralysis of up to 51.4% of the nerves studied. CONCLUSION: Consistent with in-vivo studies, RLN exhibit significant intrinsic electrophysiological variability in response to tensile forces. Moreover, nerve damage progresses even after the complete cessation of strain. Up to 20% of nerves with transiently increased post-traumatic amplitudes above 100% developed complete LOS, which we termed the "weepy cry." This time-delayed response must be considered during the interpretation of C-IONM signals.

A novel method of neurophysiological brainstem mapping in neurosurgery.

BACKGROUND: Brainstem mapping with electrical stimulation allows functional identification of neural structures during resection of deep lesions. Single pulses or train of pulses are delivered to map cranial nerves and corticospinal tracts, respectively. NEW METHOD: We introduce a hybrid stimulation technique for mapping the brainstem. The stimulus consists of an electrical single pulse followed by a short train of 3-5 pulses at 500 Hz, at an interval of 60-75 ms. The responses to this stimulation pattern are recorded from appropriate cranial and limb muscles. RESULTS: Both the single pulse and the short train elicit electromyographic responses when motor fibers or motor nuclei of the cranial nerves are stimulated. Responses to the train but not to the preceding single pulse indicate activation of the descending motor tracts, in the mesencephalon and the pons. Conversely, in the medulla, limb responses to stimulation of the corticospinal tracts are elicited by a single pulse. Identification of the extra and intra-axial courses of the trigeminal motor and sensory fibers is possible by recording responses from the masseter and the tongue muscles. COMPARISON WITH EXISTING METHOD(S): To date, either a pulse or a train is delivered during brainstem mapping, switching from one to the other modality according to the expected target structure. This procedure can be time-consuming and may even lead to false negative responses to the stimulation, eventually leading to inaccurate neurosurgical procedures. CONCLUSIONS: The novel hybrid pulse-train technique enhances the advantage of brainstem mapping procedure, minimizing pitfalls and improving patient safety.

Intraoperative EEG-based monitors: are we looking under the lamppost?

PURPOSE OF REVIEW: While electroencephalogram (EEG)-based depth of anesthesia monitors have been in use clinically for decades, there is still a major debate concerning their efficacy for detecting awareness under anesthesia (AUA). Further utilization of these monitors has also been discussed vividly, for example, reduction of postoperative delirium (POD).It seems that with regard to reducing AUA and POD, these monitors might be applicable, under specific anesthetic protocols. But in other settings, such monitoring might be less contributive and may have a 'built-it glass ceiling'.Recent advances in other venues of electrophysiological monitoring might have a strong theoretical rationale, and early supporting results, to offer a breakthrough out of this metaphorical glass ceiling. The purpose of this review is to present this possibility. RECENT FINDINGS: Following previous findings, it might be concluded that for some anesthesia protocols, the prevailing depth of anesthesia monitors may prevent incidences of AUA and POD. However, in other settings, which may involve other anesthesia protocols, or specifically for POD - other perioperative causes, they may not. Attention-related processes measured by easy-to-use real-time electrophysiological markers are becoming feasible, also under anesthesia, and might be applicable for more comprehensive prevention of AUA, POD and possibly other perioperative complications. SUMMARY: Attention-related monitoring might have a strong theoretical basis for the prevention of AUA, POD, and potentially other distressing postoperative outcomes, such as stroke and postoperative neurocognitive disorder. There seems to be already some initial supporting evidence in this regard.

"Non-Eloquent" brain regions predict neuropsychological outcome in tumor patients undergoing awake craniotomy.

Supratotal resection of primary brain tumors is being advocated especially when involving "non-eloquent" tissue. However, there is extensive neuropsychological data implicating functions critical to higher cognition in areas considered "non-eloquent" by most surgeons. The goal of the study was to determine pre-surgical brain regions that would be predictive of cognitive outcome at 4-6 months post-surgery. Cortical reconstruction and volumetric segmentation were performed with the FreeSurfer-v6.0 image analysis suite. Linear regression models were used to regress cortical volumes from both hemispheres, against the total cognitive z-score to determine the relationship between brain structure and broad cognitive functioning while controlling for age, sex, and total segmented brain volume. We identified 62 consecutive patients who underwent planned awake resections of primary (n = 55, 88%) and metastatic at the University of New Mexico Hospital between 2015 and 2019. Of those, 42 (23 males, 25 left hemispheric lesions) had complete pre and post-op neuropsychological data available and were included in this study. Overall, total neuropsychological functioning was somewhat worse (p = 0.09) at post-operative neuropsychological outcome (Mean = -.20) than at baseline (Mean = .00). Patients with radiation following resection (n = 32) performed marginally worse (p = .036). We found that several discrete brain volumes obtained pre-surgery predicted neuropsychological outcome post-resection. For the total sample, these volumes included: left fusiform, right lateral orbital frontal, right post central, and right paracentral regions. Regardless of lesion lateralization, volumes within the right frontal lobe, and specifically right orbitofrontal cortex, predicted neuropsychological difference scores. The current study highlights the gaps in our current understanding of brain eloquence. We hypothesize that the volume of tissue within the right lateral orbital frontal lobe represents important cognitive reserve capacity in patients undergoing tumor surgery. Our data also cautions the neurosurgeon when considering supratotal resections of tumors that do not extend into areas considered "non-eloquent" by current standards.

[A sampling survey of intraoperative facial nerve monitoring in China].

Objective: This study aims to investigate the current application and the level of knowledge of intraoperative facial nerve monitoring among medical staff in China. Methods: A comprehensive online questionnaire was conducted among medical professionals across different regions in China from October 2022 to February 2023. The survey exclusively targeted departments specializing in otolaryngology, head and neck surgery, neurosurgery, and oral and maxillofacial surgery. The questionnaire covered various aspects including general information, intraoperative facial nerve monitoring practices, training history, indications for monitoring, parameters used during monitoring procedures, as well as factors influencing its implementation. Results: A total of 417 participants from 31 provincial, municipal, and autonomous regions were included. Intraoperative facial nerve monitoring was found to be implemented in 227 (54.4%,227/417) repondents of 53 institutions (24.9%, 53/213). The top three indications for implementing this technique were acoustic neuroma, parotid gland surgery, and modified middle ear surgery (mastoidectomy). Herein 81.1%(184/227) medical staff involved in intraoperative facial nerve monitoring had received relevant training, 57.3%(130/227)-92.1%(209/227) reported a lack of clear description regarding recording thresholds, stimulation currents/frequencies/wave widths. Conclusion: The majority of the institutions surveyed have not yet adopted intraoperative facial nerve monitoring. Furthermore, significant gaps concerning the procedure exist. It is imperative to establish standards or guidelines to promote its better development and application.

Consistency analysis of consciousness index and bispectral index in monitoring the depth of sevoflurane anesthesia in laparoscopic surgery.

Background: The Index of Consciousness (IoC) is a new monitoring index of anesthesia depth reflecting the state of consciousness of the brain independently developed by China. The research on monitoring the depth of anesthesia mainly focuses on propofol, and bispectral index (BIS) is a sensitive and accurate objective index to evaluate the state of consciousness at home and abroad. This study mainly analyzed the effect of IoC on monitoring the depth of sevoflurane anesthesia and the consistency and accuracy with BIS when monitoring sevoflurane maintenance anesthesia. Objective: To investigate the monitoring value of the Index of Consciousness (IoC) for the depth of sevoflurane anesthesia in laparoscopic surgery. Methods: The study population consisted of 108 patients who experienced elective whole-body anesthesia procedures within the timeframe of April 2020 to June 2023 at our hospital. Throughout the anesthesia process, which encompassed induction and maintenance using inhaled sevoflurane, all patients were diligently monitored for both the Bispectral Index (BIS) and the Index of Consciousness (IoC). We conducted an analysis to assess the correlation between IoC and BIS throughout the anesthesia induction process and from the maintenance phase to the regaining of consciousness. To evaluate the predictive accuracy of IoC and BIS for the onset of unconsciousness during induction and the return of consciousness during emergence, we employed receiver operating characteristic (ROC) curve analysis. Results: The mean difference between BIS and IoC, spanning from the pre-anesthesia induction phase to the completion of propofol induction, was 1.3 (95% Limits of Agreement [-53.4 to 56.0]). Similarly, during the interval from the initiation of sevoflurane inhalation to the point of consciousness restoration, the average difference between BIS and IoC was 0.3 (95% LOA [-10.8 to 11.4]). No statistically significant disparities were observed in the data acquired from the two measurement methodologies during both the anesthesia induction process and the journey from maintenance to the regaining of consciousness (P > 0.05). The outcomes of the ROC curve analysis disclosed that the areas under the curve (AUC) for prognosticating the occurrence of loss of consciousness were 0.967 (95% CI [0.935-0.999]) for BIS and 0.959 (95% CI [0.924-0.993]) for IoC, with optimal threshold values set at 81 (sensitivity: 88.10%, specificity: 92.16%) and 77 (sensitivity: 79.55%, specificity: 95.45%) correspondingly. For the prediction of recovery of consciousness, the AUCs were 0.995 (95% CI [0.987-1.000]) for BIS and 0.963 (95% CI [0.916-1.000]) for IoC, each associated with optimal cutoff values of 76 (sensitivity: 92.86%, specificity: 100.00%) and 72 (sensitivity: 86.36%, specificity: 100.00%) respectively. Conclusion: The monitoring of sevoflurane anesthesia maintenance using IoC demonstrates a level of comparability to BIS, and its alignment with BIS during the maintenance phase of sevoflurane anesthesia is robust. IoC displays promising potential for effectively monitoring the depth of anesthesia.

[Surgical treatment of brain tumors adjacent to corticospinal tract in children]. / Aktual'nye voprosy khirurgicheskogo lecheniya opukholei golovnogo mozga, prilegayushchikh k kortikospinal'nomu traktu u detei.

An urgent problem in modern neurosurgery is resection of brain tumors adjacent to corticospinal tract (CST) due to high risk of its damage and subsequent disability. The main methods for prevention of intraoperative damage to CST are preoperative MR tractography and intraoperative electrophysiological monitoring. Both methods are used in pediatric neurosurgery. We reviewed the PubMed database since 2000 using the following keywords: «tumors of the hemispheres in children¼, «corticospinal tract¼, «MR tractography¼, «intraoperative electrophysiological monitoring¼. We present available literature data on preoperative MR tractography and intraoperative electrophysiological monitoring in children with supratentorial tumors near CST. Algorithm of intraoperative electrophysiological monitoring is often missing or insufficiently described. MR tractography is usually presented in case reports. Researchers do not compare the effectiveness of MR tractography and intraoperative electrophysiological monitoring. In case of MR tractography, a limitation is impossible CST reconstruction in children 2-3 years old. This may be due to unformed pyramidal system in these children. CONCLUSION: Preoperative MR tractography and intraoperative electrophysiological monitoring are valid methods for assessment of CST. Optimal research parameters in children require careful study that will allow objective planning of each stage of preoperative management and increase resection quality for gliomas near CST in children without neurological deterioration.

The Edwards Acumen IQ system using peripheral arterial catheter-based waveforms to estimate cardiac output is not accurate as compared to thermodilution in dogs.

OBJECTIVE: To assess the agreement between cardiac output (CO) estimated via evaluation of the arterial pressure waveform by a novel monitoring system (Edwards Acumen IQ sensor and HemoSphere Advanced Monitor Platform [HS-IQ]; Edwards LifeSciences) and measured by thermodilution (TD) in anesthetized, normovolemic, and hypovolemic dogs. To assess the agreement between the HS-IQ CO measurements in the radial artery and dorsal metatarsal artery. ANIMALS: 8 purpose-bred Beagles. METHODS: Dogs were placed under general anesthesia. CO was measured via TD and via the HS-IQ at radial and dorsal metatarsal arterial catheters. CO measurements were obtained at 4 time points including normovolemic and multiple hypovolemic states. Paired measurements of CO were evaluated via the method of Bland and Altman with acceptable limits of agreement (LOA) defined as < 30%. RESULTS: A total of 24 (dorsal metatarsal) and 21 (radial) paired measurements were collected in 8 dogs. The overall bias (CI) for comparison of TD to radial arterial HS-IQ CO measurements was -0.09 L/min. LOA and proportional LOA were -2.66 to 2.49 L/min and -140.72% to 104.94%. The overall bias (CI) for comparison of TD to dorsal metatarsal arterial HS-IQ CO measurements was -0.26 L/min. LOA and proportional LOA were -2.76 to 2.24 L/min and -135.96% to 93.25%. The overall proportional error for radial arterial was -17.9% and for dorsal metatarsal was -21.4%. CLINICAL RELEVANCE: CO measurements with the HS-IQ were easy to obtain but did not produce results within a clinically acceptable range for either measurement site, with a very wide LOA. The CO estimations from the HS-IQ are not appropriate for clinical use at this time.

Effect of high-field iMRI guided resection in cerebral glioma surgery: A randomized clinical trial.

BACKGROUND: Extent of resection (EOR) in glioma contributes to longer survival. The purpose of NCT01479686 was to prove whether intraoperative magnetic resonance imaging (iMRI) increases EOR in glioma surgery and benefit survival. METHODS: Patients were randomized (1:1) to receive the iMRI (n = 161) or the conventional neuronavigation (n = 160). The primary endpoint was gross total resection (GTR); secondary outcomes reported were progression-free survival (PFS), overall survival (OS), and safety. RESULTS: 188 high-grade gliomas (HGGs) and 133 low-grade gliomas (LGGs) were enrolled. GTR was 83.85% in the iMRI group vs. 50.00% in the control group (P < 0.0001). In 321 patients, the median PFS (mPFS) was 65.12 months in the iMRI group and 61.01 months in the control group (P = 0.0202). For HGGs, mPFS was improved in the iMRI group (19.32 vs. 13.34 months, P = 0.0015), and a trend of superior OS compared with control was observed (29.73 vs. 25.33 months, P = 0.1233). In the predefined eloquent area HGG subgroup, mPFS, and mOS were 20.47 months and 33.58 months in the iMRI vs. 12.21 months and 21.16 months in the control group (P = 0.0098; P = 0.0375, respectively). From the exploratory analyses of HGGs, residual tumor volume (TV) < 1.0 cm3 decreased the risk of survival (mPFS: 18.99 vs. 9.43 months, P = 0.0055; mOS: 29.77 vs. 18.10 months, P = 0.0042). LGGs with preoperative (pre-OP) TV > 43.1 cm3 and postoperative (post-OP) TV > 4.6 cm3 showed worse OS (P= 0.0117) CONCLUSIONS: It showed that iMRI significantly increased EOR and indicated survival benefits for HGGs, particularly eloquent HGGs. Residual TV in either HGGs or LGGs is a prognostic factor for survival.

Predictive value of facial motor-evoked potential and electromyography for facial motor function in vestibular schwannoma surgery.

PURPOSE: Intraoperative neuromonitoring (IONM) aims to preserve facial nerve (FN) function during vestibular schwannoma (VS) surgery. However, current techniques such as facial nerve motor evoked potentials (FNMEP) or electromyography (fEMG) alone are limited in predicting postoperative facial palsy (FP). The objective of this study was to analyze a compound fEMG/FNMEP approach. METHODS: Intraoperative FNMEP amplitude and the occurrence of fEMG-based A-trains were prospectively determined for the orbicularis oris (ORI) and oculi (OCU) muscle in 322 VS patients. Sensitivity and specificity of techniques to predict postoperative FN function were calculated. Confounding factors as tumor size, volume of intracranial air, or IONM duration were analyzed. RESULTS: A relevant immediate postoperative FP was captured in 105/322 patients with a significant higher risk in large VS. While fEMG demonstrated a high sensitivity (77% and 86% immediately and 15 month postoperative, respectively) for identifying relevant FP, specificity was low. In contrast, FNMEP have a significantly higher specificity of 80.8% for predicting postoperative FP, whereas the sensitivity is low. A retrospective combination of techniques demonstrated still an incorrect prediction of FP in ~ 1/3 of patients. CONCLUSIONS: FNMEP and fEMG differ in sensitivity and specificity to predict postoperative FP. Although a combination of IONM techniques during VS surgery may improve prediction of FN function, current techniques are still inaccurate. Further development is necessary to improve IONM approaches for FP prediction.

Agreement of zero-heat-flux thermometry with the oesophageal and tympanic core temperature measurement in patient receiving major surgery.

To identify and prevent perioperative hypothermia, most surgical patients require a non-invasive, accurate, convenient, and continuous core temperature method, especially for patients undergoing major surgery. This study validated the precision and accuracy of a cutaneous zero-heat-flux thermometer and its performance in detecting intraoperative hypothermia. Adults undergoing major non-cardiac surgeries with general anaesthesia were enrolled in the study. Core temperatures were measured with a zero-heat-flux thermometer, infrared tympanic membrane thermometer, and oesophagal monitoring at 15-minute intervals. Taking the average value of temperature measured in the tympanic membrane and oesophagus as a reference, we assessed the agreement using the Bland-Altman analysis and linear regression methods. Sensitivity, specificity, and predictive values of detecting hypothermia were estimated. 103 patients and one thousand sixty-eight sets of paired temperatures were analyzed. The mean difference between zero-heat-flux and the referenced measurements was -0.03 ± 0.25 °C, with 95% limits of agreement (-0.52 °C, 0.47 °C) was narrow, with 94.5% of the differences within 0.5 °C. Lin's concordance correlation coefficient was 0.90 (95%CI 0.89-0.92). The zero-heat-flux thermometry detected hypothermia with a sensitivity of 82% and a specificity of 90%. The zero-heat-flux thermometer is in good agreement with the reference core temperature based on tympanic and oesophagal temperature monitoring in patients undergoing major surgeries, and appears high performance in detecting hypothermia.

Neuromonitoring for spine surgery in children.

Neuromonitoring or electrophysiologic monitoring is now an essential component of pediatric spine surgery due to the high number of spinal deformity indications in asymptomatic patients, for whom any neurological complication would be disastrous. Technological advances have led to the development of compact monitors that allow surgeons themselves to monitor the motor evoked potentials (MEP) perioperatively. This shift happened because it was difficult to always have a neurophysiologist in the operating room. Unfortunately, this also means that multimodal monitoring (sensory, mixed, D-wave, electromyography, pedicle screws) is much more difficult to implement. There are absolute indications, such as any spinal deformity without neurological deficit and relative indications, which are more difficult to interpret. Technical incidents frequently occur before the start of the surgery. If no replacement device is available, the procedure must be cancelled unless the patient's life or function are at risk. At least two monitoring systems should be available at every facility to avoid having to cancel surgery for purely technological reasons. Once the surgical procedure has started, the absence of MEP recruitment curves in the upper and lower limbs is likely due to the anesthesia depth; the surgery should be stopped until this problem is corrected. When there is a true intraoperative alert (MEPs disappear in the lower limbs only), we propose taking the following steps, depending on whether the spine is stable or unstable: remove the causal implant, remove all hardware, preserve any stabilization devices, initiate an intraoperative wake-up test, verify conditions under which the intervention should continue. Level of evidence: V.

Noninvasive hemoglobin monitoring for maintaining hemoglobin concentration within the target range during major noncardiac surgery: A randomized controlled trial.

STUDY OBJECTIVE: The effect of noninvasive CO-oximetry hemoglobin (SpHb) monitoring on the clinical outcomes of patients undergoing surgery remains unclear. This trial aimed to evaluate whether SpHb monitoring helps maintain hemoglobin levels within a predefined target range during major noncardiac surgeries with a potential risk of intraoperative hemorrhage. DESIGN: A single-center, prospective, randomized controlled trial. SETTING: University hospital. PATIENTS: One hundred and thirty patients undergoing elective noncardiac surgery with a potential risk of hemorrhage. INTERVENTIONS: Patients were randomly allocated to undergo either SpHb-guided management (SpHb group) or usual care (control group). MEASUREMENTS: The primary outcome was the rate of deviation of the total hemoglobin concentration (determined from laboratory testing) from a pre-specified target range (8-14 g/dL). This was defined as the number of laboratory tests revealing such deviations divided by the total number of laboratory tests performed during the surgery. MAIN RESULTS: The primary outcome occurred significantly less frequently in the SpHb group as compared to that in the control group (15/555 [2.7%]) vs. 68/598 [11.4%]; relative risk, 0.24; 95% confidence interval, 0.13-0.41; P < 0.001). Fewer point-of-care blood tests were performed in the SpHb group than in the control group (median [interquartile range], 2 [1-4] vs. 4 [2-5]; P < 0.001). There were no significant intergroup differences in the number of patients who received red blood cell transfusions during surgery (SpHb vs. control, 33.8% vs. 46.2%; P = 0.201). The incidence of unnecessary red blood cell preparation (>2 units) was lower in the SpHb group than in the control group (3.1% vs. 16.9%; P = 0.024). CONCLUSIONS: Compared with routine care, SpHb-guided management resulted in significantly lower rates of hemoglobin deviation outside the target range intraoperatively in patients undergoing major noncardiac surgeries with a potential risk of hemorrhage. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov (identifier: NCT03816514).

Intraoperative motor-evoked potential with tetanic stimulation changes pre- and post-hemispherotomy.

BACKGROUND: Careful examination of motor-evoked potential (MEP) findings is critical to the safety of intraoperative neuromonitoring during neurosurgery. We reviewed the intraoperative MEP findings in a pediatric patient who had undergone hemispherotomy for refractory epilepsy. CASE DESCRIPTION: The patient was a 4-year-and-2-month-old boy with extensive right cerebral hemisphere, drug-resistant epilepsy, left upper and lower extremity paralysis, and cognitive impairment. We examined intraoperative MEP results both before and after hemispherotomy. Post-hemispherotomy and MEPs were successfully elicited through transcranial electrical stimulation (TES) but not via direct cortical stimulation on the right side. Furthermore, TES on the right side, following hemispherotomy, led to a reduction in the MEP amplification effect resulting from tetanic stimulation of the left unilateral median and tibial nerves. Conversely, we observed the effects of MEP amplification during TES on the left side after tetanic stimulation of these nerves. Postoperatively, the patient underwent magnetic resonance imaging and electroencephalogram examinations, confirming the anatomical and electrophysiological completeness of the dissection. Notably, the seizures disappeared, and no apparent complications were observed. CONCLUSION: Collectively, our findings suggest that TES can still activate deep structures and elicit MEPs, even in cases where the corticospinal connections to the posterior limb of the internal capsule are entirely severed. Thalamo-cortical interactions may affect the MEP amplification, observed during tetanic stimulation. Injury to the corticospinal tracts of the white matter may be obscured on conventional MEP findings; however, it may be identified by MEP changes in tetanic stimulation.

Updated review on the use of neuromuscular blockade during intraoperative motor-evoked potential monitoring in the modern anesthesia era.

Transcranial electrical stimulation motor-evoked potentials (Tc-MEP) monitoring is a common practice in neurosurgery to prevent postoperative neurological damage. However, the use of neuromuscular blocking agents (NMBAs) during Tc-MEP monitoring is a subject of controversy. In addition, the effectiveness of sugammadex, a selective reversal agent, in the context of Tc-MEP monitoring requires further investigation. This review aimed to clarify the considerations involved in achieving optimal Tc-MEP monitoring while ensuring patient safety. Preoperative patient selection, comorbidity assessment, motor power evaluation, and the nature of the planned surgery are critical factors. Accurate paralysis assessment, continuous NMBA infusion, and post-tetanic stimulation techniques are essential for achieving optimal partial NMB. The decision to administer an NMB during Tc-MEP monitoring necessitates a careful evaluation of the balance between accuracy and potential complications. This review emphasizes the challenges associated with NMB administration during Tc-MEP monitoring and highlights the need for personalized patient assessment.

Clinical validation of NerveTrend versus conventional i-IONM mode of NIM Vital in prevention of recurrent laryngeal nerve events during bilateral thyroid surgery: A randomized controlled trial.

BACKGROUND: The aim of this study was to test the hypothesis that use of NerveTrend™ mode of intermittent neuromonitoring (i-IONM) during thyroidectomy may identify and prevent impending recurrent laryngeal nerve (RLN) injury. METHODS: A randomized clinical trial. The primary outcome was prevalence of RLN injury on postoperative day 1. In NerveTrend™ group the i-IONM stimulator was used for trending of amplitude and latency changes from initial vagal electromyographic baseline to tailor surgical strategy. RESULTS: Some 264 patients were randomized into the intervention versus the control group, 132 patients each. RLN injury was found on postoperative day 1 in 5/264 (1.89%) nerves at risk (NAR) versus 12/258 (4.65%) NAR whereas staged thyroidectomy was used in 0/132 (0.00%) versus 6/132 (4.54%) patients (p = 0.067 and p = 0.029, respectively). CONCLUSION: The use of NerveTrend™ mode resulted in tendency towards reduced RLN injury on postoperative day 1 and significant decrease of need for a staged thyroidectomy.

Intraoperative monitoring of the central and peripheral nervous systems: a narrative review.

The central and peripheral nervous systems are the primary target organs during anaesthesia. At the time of the inception of the British Journal of Anaesthesia, monitoring of the central nervous system comprised clinical observation, which provided only limited information. During the 100 yr since then, and particularly in the past few decades, significant progress has been made, providing anaesthetists with tools to obtain real-time assessments of cerebral neurophysiology during surgical procedures. In this narrative review article, we discuss the rationale and uses of electroencephalography, evoked potentials, near-infrared spectroscopy, and transcranial Doppler ultrasonography for intraoperative monitoring of the central and peripheral nervous systems.

Optimal method for reliable lateral spread response monitoring during microvascular decompression surgery for hemifacial spasm.

In this study, we propose an optimal method for monitoring the key electrophysiological sign, the Lateral Spread Response (LSR), during microvascular decompression (MVD) surgery for hemifacial spasm (HFS). Current monitoring methods and interpretations of LSR remain unclear, leading to potential misinterpretations and undesirable outcomes." We prospectively collected data from patients undergoing MVD for HFS, including basic demographics, clinical characteristics, and surgical outcomes. Stimulation intensity was escalated by 1 mA increments to identify the optimal range for effective LSR. We designated the threshold at which we can observe LSR as THR1 and THR2 for when LSR disappears, with high-intensity stimulation (30 mA) designated as THR30. Subsequently, we compared abnormal muscle responses (AMR) between the optimal range (between THR1 and THR2) and THR30. Additionally, we conducted an analysis to identify and assess factors associated with artifacts and their potential impact on clinical outcomes. As stimulation intensity increases, the onset latency to detect AMR was shortened. The first finding of the study was high intensity stimulation caused artifact that mimic the wave of LSR. Those artifacts were observed even after decompression thus interfere interpretation of disappearance of LSR. Analyzing the factors related to the artifact, we found the AMR detected at onset latency below 9.6 ms would be the lateral spreading artifact (LSA) rather than true LSR. To avoid false positive LSR from LSA, we should stepwise increase stimulation intensity and not to surpass the intensity that cause LSR onset latency below 10 ms.

Intraoperative cricothyroid muscle electromyography may contribute to the monitorization of the external branch of the superior laryngeal nerve during thyroidectomy.

Background: In thyroid surgery, both the recurrent laryngeal nerve (RLN) and external branch of the superior laryngeal nerve (EBSLN) should be preserved for maintaining the vocal cord functions. We aimed to evaluate whether EMG of the CTM applied after the superior pole dissection provided additional informative data to the IONM via ETT or not, regarding the EBSLN function. Methods: The prospectively collected data of the patients, who have undergone thyroidectomy with the use of IONM for the exploration of both the RLN and EBSLN between October 2016 and March 2017, were evaluated retrospectively. Patients over 18 years of age with primary thyroid surgery for malignant or benign thyroid disease, and whom were applied CTM EMG with a needle electrode after the completion of thyroidectomy were included in the study. In the study, each neck side was evaluated as a separate entity considering the EBSLN at risk. Results: The data of 41 patients (32 female, 9 male) (mean age, 46.7 + 9.1; range, 22-71) were evaluated. Sixty seven EBSLNs out of 26 bilateral and 15 unilateral interventions were evaluated. With EBSLN stimulation after the superior pole dissection, positive glottic EMG waveforms via ETT were obtained in 45 (67.2%) out of 67, and the mean glottic amplitude value was 261 + 191 µV (min-max: 116-1086 µV). Positive EMG responses via the CTM EMG were achieved from all of the 67 EBSLNs (100%) with stimulation using a monopolar probe at the most cranial portion above the area of divided superior pole vessels. The mean value of CTM amplitudes via CTM EMG obtained with EBSLN stimulation was 5268 + 3916 µV (min-max:1215 -19726 µV). With EBSLN stimulation, the mean CTM EMG amplitude was detected significantly higher than the mean vocal cord amplitude (p<0.0001). The CTM EMG provided more objective quantifiable data regarding the EBSLN function (100% vs 67,2%, p<0.001). Conclusion: In addition to the IONM via ETT, intraoperative post-dissection CTM EMG via needle electrode is a safe, simple and applicable method that may provide significant additional informative data to IONM with ETT by obtaining and recording objective quantitative data related to the EBSLN function.