Recurrent laryngeal nerve (RLN) injury during neck surgery can cause significant morbidity related to vocal cord (VC) dysfunction. VC electromyography (EMG) is used to aid in the identification of the RLN and can reduce the probability of inadvertent surgical injury. Errors in the placement of specialized EMG endotracheal tubes (ETT) can result in unreliable signals, false-negative responses, or no response when stimulating the RLN. We describe a novel educational protocol developed to optimize uniformity in the placement of ETTs to improve the reliability of RLN monitoring. An intraoperative neuromonitoring database was queried for all neck surgeries requiring RLN monitoring. Data points extracted for all cases requiring EMG monitoring for neck procedures. Free running and stimulated EMG were monitored and continuously recorded by a certified technologist. Alerts were compared between 2013-14 and 2015-18 using a two-sample test of proportions. Significant reductions in alerts were demonstrated after protocol implementation (7.5% pre-implementation to 2.1% post). Alerts were compared between 2013-14 (overall alert rate of 1.8%, pre-implementation period) and 2015-18 (overall alert rate of 2.8%, post-implementation period). Protocolization for placement of EMG-ETT improved accuracy in EMG monitoring. In the follow-up cohort of 1,080 patients, use of this protocol continued to reduce the rate of alerts related to ETT malposition, confirming the sustainability of this intervention through routine education. The risk of nerve injury is reduced when the rate of alerts is minimized. Scheduled or continuous protocol education of anesthesia personnel should continue to ensure compliance with protocol.

The recent article \"Clinical characteristics and outcomes after trigeminal schwannoma resection: a multi-institutional experience\" by Nandoliya et al. offers critical insights into the management of trigeminal schwannomas (TS). This multi-institutional study, encompassing 30 patients over 18 years, highlights various surgical approaches, achieving gross-total resection in 53% of cases, and emphasizes the balance between resection and neurological preservation. The use of intraoperative neuromonitoring in 77% of cases is noted for minimizing morbidity. Despite a 13% complication rate, most were transient. Long-term follow-up data show a low recurrence rate, advocating for ongoing surveillance. The study underscores the importance of tailored surgical strategies, and the discussion of classification systems aids in contextual understanding. While the findings are robust, further research into adjuvant therapies and emerging technologies is warranted. This comprehensive overview advances our understanding of TS, promoting a patient-centered approach to surgical management.

BACKGROUND: The aim of this study is to describe the management and associated follow-up strategies adopted by thyroid surgeons with different surgical volumes when loss of signal (LOS) occurred on the first side of planned bilateral thyroid surgery, and to further define the consensus on intraoperative neuromonitoring (IONM) applications.
METHODS: The International Neural Monitoring Study Group (INMSG) web-based survey was sent to 950 thyroid surgeons worldwide. The survey included information on the participants, IONM team/equipment/procedure, intraoperative/postoperative management of LOS, and management of LOS on the first side of thyroidectomy for benign and malignant disease.
RESULTS: Out of 950, 318 (33.5%) respondents completed the survey. Subgroup analyses were performed based on thyroid surgery volume: <50 cases/year (n = 108, 34%); 50 to 100 cases/year (n = 69, 22%); and >100 cases/year (n = 141, 44.3%). High-volume surgeons were significantly (P < .05) more likely to perform the standard procedures (L1-V1-R1-S1-S2-R2-V2-L2), to differentiate true/false LOS, and to verify the LOS lesion/injury type. When LOS occurs, most surgeons arrange otolaryngologists or speech consultation. When first-side LOS occurs, not all respondents decided to perform stage contralateral surgery, especially for malignant patients with severe disease (eg, extrathyroid invasion and poorly differentiated thyroid cancer).
CONCLUSIONS: Respondents felt that IONM was optimized when conducted under a collaborative team-based approach, and completed IONM standard procedures and management algorithm for LOS, especially those with high volume. In cases of first-site LOS, surgeons can determine the optimal management of disease-related, patient-related, and surgical factors. Surgeons need additional education on LOS management standards and guidelines to master their decision-making process involving the application of IONM.

OBJECTIVE: We assessed the Transcranial Electrical Stimulation (TES)-induced Corticobulbar-Motor Evoked Potentials (Cb-MEPs) evoked from Orbicularis Oculi (Oc) and Orbicularis Oris (Or) muscles with FCC5h/FCC6h-Mz, C3/C4-Cz and C5/C6/-Cz stimulation, during IntraOperative NeuroMonitoring (IONM) in 30 patients who underwent skull-base surgery.
METHODS: before (T0) and after (T1) the surgery, we compared the peak-to-peak amplitudes of Cb-MEPs obtained from TES with C3/C4-Cz, C5/C6-Cz and FCC5h/FCC6h-Mz. Then, we compared the response category (present, absent and peripheral) related to different montages. Finally, we classified the Cb-MEPs data from each patient for concordance with clinical outcome and we assessed the diagnostic measures for Cb-MEPs data obtained from FCC5h/FCC6h-Mz, C3/C4-Cz and C5/C6-Cz TES stimulation.
RESULTS: Both at T0 and T1, FCC5h/FCC6h-Mz stimulation evoked larger Cb-MEPs than C3/C4-Cz, less peripheral responses from direct activation of facial nerve than C5/C6-Cz. FCC5h/FCC6h-Mz stimulation showed the best accuracy and specificity of Cb-MEPs for clinical outcomes.
CONCLUSIONS: FCC5h/FCC6h-Mz stimulation showed the best performances for monitoring the facial nerve functioning, maintaining excellent diagnostic measures even at low stimulus voltages.
CONCLUSIONS: We demonstrated that FCC5h/FCC6h-Mz TES montage for Cb-MEPs in IONM has good accuracy in predicting the post-surgery outcome of facial nerve functioning.

Somatosensory evoked potentials (SEPs) are used to assess the functional status of somatosensory pathways during surgical procedures and can help protect patients\' neurological integrity intraoperatively. This is a position statement on intraoperative SEP monitoring from the American Society of Neurophysiological Monitoring (ASNM) and updates prior ASNM position statements on SEPs from the years 2005 and 2010. This position statement is endorsed by ASNM and serves as an educational service to the neurophysiological community on the recommended use of SEPs as a neurophysiological monitoring tool. It presents the rationale for SEP utilization and its clinical applications. It also covers the relevant anatomy, technical methodology for setup and signal acquisition, signal interpretation, anesthesia and physiological considerations, and documentation and credentialing requirements to optimize SEP monitoring to aid in protecting the nervous system during surgery.

BACKGROUND: Surgery for lesions of the posterior fossa is associated with significant postoperative pain in pediatric patients related to extensive manipulation of the suboccipital musculature and bone. In this study, we assess the preliminary safety, effect on neuromonitoring, and analgesic efficacy of applying a cervical paraspinal interfascial plane block in pediatric patients undergoing posterior fossa surgery.
METHODS: In this prospective case series, we enrolled five patients aged 2-18 years undergoing surgery for symptomatic Chiari type I malformation. An ultrasound-guided cervical cervicis plane (CCeP) block was performed prior to the incision. A local anesthetic agent (bupivacaine) and a steroid adjuvant (dexamethasone) were injected into the fascial planes between the cervical semispinalis capitis and cervical semispinalis cervicis muscles at the level of the planned suboccipital decompression and C1 laminectomy. Motor-evoked and somatosensory-evoked potentials were monitored before and after the block. Patients were assessed for complications from the local injection in the intraoperative period and for pain in the postoperative period.
RESULTS: No adverse events were noted intraoperatively, and there were no changes in neuromonitoring signals. Pain scores were low in the immediate postoperative period, and rescue medications were minimal. No complaints of incisional pain or need for narcotics were noted at the time of the 3-month postsurgical follow-up.
CONCLUSIONS: In this study, we demonstrate the preliminary safety and analgesic efficacy of a novel application of a CCeP block to pediatric patients undergoing suboccipital surgery. Larger studies are needed to further validate the use of this block in children.

Traumatic peripheral nerve injuries (PNI), present with symptoms ranging from pain to loss of motor and sensory function. Difficulties in intraoperative visual assessment of nerve functional status necessitate intraoperative nerve conduction studies (INCSs) by neurosurgeons and neurologists to determine the presence of functioning axons in the zone of a PNI. This process, also referred to as nerve \"inching\", uses a set of stimulating and recording electrode hooks to lift the injured nerve from the surrounding surgical field and to determine whether an electrical stimulus can travel through the zone of injury. However, confounding electrical signal artifacts can arise from the current workflow and electrode design, particularly from the mandatory lifting of the nerve, complicating the definitive assessment of nerve function and neurosurgical treatment decision-making. The objective of this study is to describe the design process and verification testing of our group\'s newly designed stimulating and recording electrodes that do not require the lifting or displacement of the injured nerve during INCSs. Ergonomic in vivo analysis of the device within a porcine model demonstrated successful intraoperative manipulation of the device, while quantitative nerve action potential (NAP) signal analysis with an ex vivo simulated \"inching\" procedure on healthy non-human primate nerve tissue demonstrated excellent reproducible recorded NAP fidelity and the absence of NAP signal artifacts at all points of recording. Lastly, electrode pullout force testing determined maximum forces of 0.43 N, 1.57 N, and 3.61 N required to remove the device from 2 mm, 5 mm, and 1 cm nerve models, respectively, which are well within established thresholds for nerve safety. These results suggest that these new electrodes can safely and successfully perform accurate PNI assessment without the presence of artifacts, with the potential to improve the INCS standard of care while remaining compatible with currently used neurosurgical technology, infrastructure, and clinical workflows.

OBJECTIVE: To demonstrate the utility of intraoperative neuromonitoring (IONM) as an effective method of passive thermoprotection against cryogenic injury to neural structures during musculoskeletal and lymph node cryoablation.
METHODS: Twenty-nine patients (16 men; mean age among men, 68.6 years [range, 45-90 years]; mean age among women, 62.6 years [range, 28-88 years]) underwent 33 cryoablations of musculoskeletal and lymph node lesions. Transcranial electrical motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SSEPs) of target nerves were recorded throughout the ablations. Significant change was defined as waveform amplitude reduction greater than 30% (MEP) and 50% (SSEP). The primary outcomes of this study were immediate postprocedural neurologic deficits and frequency of significant MEP and SSEP amplitude reductions.
RESULTS: Significant amplitude reductions were detected in 54.5% (18/33) of MEP tracings and 0% (0/33) of SSEP tracings. Following each occurrence of significant amplitude reductions, freeze cycles were promptly terminated. Intraprocedurally, 13 patients had full recovery of amplitudes to baseline, 11 of whom had additional freeze cycles completed. In 5 of 33 (15.2%) cryoablations, there were immediate postprocedural neurologic deficits (moderate adverse events). Unrecovered MEPs conferred a relative risk for neurologic sequela of 23.2 (95% CI, 3.22-167.21; P < .001) versus those with recovered MEPs. All 5 patients had complete neurologic recovery by 12 months.
CONCLUSIONS: IONM (with MEP but not SSEP) is a reliable and safe method of passive thermoprotection of neurologic structures during cryoablation. It provides early detection of changes in nerve conduction, which when addressed quickly, may result in complete restoration of MEP signals within the procedure and minimize risk of cryogenic neural injury.

Surgery for spinal cord tumors poses a significant challenge due to the inherent risk of neurological deterioration. Despite being performed at numerous centers, there is an ongoing debate regarding the efficacy of pre- and intraoperative neurophysiological investigations in detecting and preventing neurological lesions. This study begins by providing a comprehensive review of the neurophysiological techniques commonly employed in this context. Subsequently, we present findings from a cohort of 67 patients who underwent surgery for intradural tumors. These patients underwent preoperative and intraoperative multimodal somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs), with clinical evaluation conducted three months postoperatively. The study aimed to evaluate the neurophysiological, clinical, and radiological factors associated with neurological outcomes. In univariate analysis, preoperative and intraoperative potential alterations, tumor size, and ependymoma-type histology were linked to the risk of worsening neurological condition. In multivariate analysis, only preoperative and intraoperative neurophysiological abnormalities remained significantly associated with such neurological deterioration. Interestingly, transient alterations in intraoperative MEPs and SSEPs did not pose a risk of neurological deterioration. The machine learning model we utilized demonstrated the possibility of predicting clinical outcome, achieving 84% accuracy.

OBJECTIVE: Despite the benefits of anterior temporal lobectomy with amygdalohippocampectomy in patients with temporal lobe epilepsy (TLE), approximately up to 5% may have hemiparesis as its postoperative complication. This paper aims to describe which step/s of the anterior temporal lobectomy with amygdalohippocampectomy have the highest probability of having the greatest decrease in motor evoked potential (MEP) amplitude.
METHODS: This study used a cross-sectional design of obtaining data from TLE patients who underwent anterior temporal lobectomy with amygdalohippocampectomy with transcranial MEP monitoring. Each of the following steps were evaluated for reduction in MEP amplitude: 1) dural opening, 2) opening the inferior horn, 2) vertical temporal lobe resection 3) subpial dissection, 4) temporal lobe stem resection, 5) lateral temporal lobe resection, 6) hippocampal resection, 7) amygdala resection, 8) uncus resection, and 9) dural closure.
RESULTS: Nineteen patients were included in the study. Based on the Friedman Test, 1 or more steps had significantly different average MEP amplitude reductions (Friedman = 50.7, P = 0.0001). When compared with baseline (100%, cutoff P = 0.005), hippocampal resection (z = -3.81, P < 0.0001), T1 subpial dissection (z = -3.2, P = 0.0010), uncus resection (z = -3.48, P = 0.0002), temporal stem resection (z = -3.26, P = 0.001), lateral temporal lobe resection (z = -3.13, P = 0.002), and amygdalectomy (-z = -3.37, P = 0.0005) were significantly lower. Of these, hippocampal resection, uncus resection, and amygdalectomy were deemed highly significant.
CONCLUSIONS: MEP amplitude tends to decrease during amygdala, hippocampal, and uncal resection because of surgical manipulation of anterior choroidal arteries, which can potentially cause hemiparesis. Careful attention should be paid to changes in MEP during these steps.