Median nerve somatosensory evoked potential alarm related to head and neck positioning for carotid surgery.

Head positioning in carotid surgery represents an often overlooked but sensitive period in the surgical plan. A 53-year-old male presented a significant decrement in median nerve somatosensory evoked potential (mSEP) following head and neck positioning for carotid pseudoaneurysm repair before skin incision.Neurophysiological monitoring was performed with mSEP and electroencephalography early during the patient's preparation and surgery. Within five minutes after rotation and extension of the head to properly expose the surgical field, the contralateral m-SEP significantly decreased in both cortical (N20/P25) and subcortical (P14/N18) components. Partial neck correction led to m-SEP improvement, allowing to proceed with the carotid repair. We discuss possible underlying pathophysiological mechanisms responsible for these changes and highlight the relevance of an early start on monitoring to avoid neurological deficits.

Unexpected median SEPs fluctuations during brain cavernous malformation resection with no post-operative deficit.

Median nerve somatosensory evoked potentials (SEPs) may present changes during cavernous malformation (CM) resection unrelated to new post-operative sensory deficits. We performed intraoperative neurophysiological monitoring of median SEPs (m-SEPs) in three patients who underwent CM resection (surgery) near the sensory-motor cortex. The only preoperative clinical manifestations in all patients were seizures. All patients presented m-SEPs alterations on the side of the lesion during the procedure. Two patients presented permanent changes in the cortical potentials. In the third patient, the cortical and subcortical components suffered temporal fluctuations to return to baselines at the end of the surgery. None of these patients developed new post-operative clinical deficits. During brain cavernous malformation resection, significant fluctuations in the amplitude of different components of m-SEPs may occur. These changes may be due to excitability variations on m-SEP generators and do not translate into new post-operative neurological deficits.

Optimizing the methodology for saphenous nerve somatosensory evoked potentials for monitoring upper lumbar roots and femoral nerve during lumbar spine surgery: technical note.

The demand for intraoperative monitoring (IOM) of lumbar spine surgeries has escalated to accommodate more challenging surgical approaches to prevent perioperative neurologic deficits. Identifying impending injury of individual lumbar roots can be done by assessing free-running EMG and by monitoring the integrity of sensory and motor fibers within the roots by eliciting somatosensory (SEP), and motor evoked potentials. However, the common nerves for eliciting lower limb SEP do not monitor the entire lumbar plexus, excluding fibers from L1 to L4 roots. We aimed to technically optimize the methodology for saphenous nerve SEP (Sap-SEP) proposed for monitoring upper lumbar roots in the operating room. In the first group, the saphenous nerve was consecutively stimulated in two different locations: proximal in the thigh and distal close to the tibia. In the second group, three different recording derivations (10-20 International system) to distal saphenous stimulation were tested. Distal stimulation yielded a higher Sap-SEP amplitude (mean ± SD) than proximal: 1.36 ± 0.9 µV versus 0.62 ± 0.6 µV, (p < 0.0001). Distal stimulation evoked either higher (73%) or similar (12%) Sap-SEP amplitude compared to proximal in most of the nerves. The recording derivation CPz-cCP showed the highest amplitude in 65% of the nerves, followed by CPz-Fz (24%). Distal stimulation for Sap-SEP has advantages over proximal stimulation, including simplicity, lack of movement and higher amplitude responses. The use of two derivations (CPz-cCP, CPz-Fz) optimizes Sap-SEP recording.

Correction to: Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary.

The article Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary, written by Stanley A. Skinner, Elif Ilgaz Aydinlar, Lawrence F. Borges, Bob S. Carter, Bradford L. Currier, Vedran Deletis, Charles Dong, John Paul Dormans, Gea Drost, Isabel Fernandez­Conejero, E. Matthew Hoffman, Robert N. Holdefer, Paulo Andre Teixeira Kimaid, Antoun Koht, Karl F. Kothbauer, David B. MacDonald, John J. McAuliffe III, David E. Morledge, Susan H. Morris, Jonathan Norton, Klaus Novak, Kyung Seok Park, Joseph H. Perra, Julian Prell, David M. Rippe, Francesco Sala, Daniel M. Schwartz, Martín J. Segura, Kathleen Seidel, Christoph Seubert, Mirela V. Simon, Francisco Soto, Jeffrey A. Strommen, Andrea Szelenyi, Armando Tello, Sedat Ulkatan, Javier Urriza and Marshall Wilkinson, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 05 January 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on 30 January 2019 to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The original article has been corrected.

Intraoperative multimodal evoked potential monitoring during carotid endarterectomy: a retrospective study of 264 patients.

BACKGROUND: Methods for detecting intraoperative cerebral ischemia arising from internal carotid artery (ICA) cross-clamping during carotid endarterectomy (CEA) should be sensitive, specific, and rapid to prevent intraoperative stroke. We had 3 objectives pertaining to this: (1) investigation of the rates of success of multimodal evoked potential (mEP) monitoring using a combination of median nerve (m) somatosensory (SS) EPs, tibial nerve SSEPs (tSSEPs), and transcranial electrical stimulated motor EPs (tcMEPs); (2) evaluation of the rates of false-negative mEP results; and (3) analysis of the relationship between different time periods associated with ICA cross-clamping and the postoperative outcome of motor function in patients with significant changes in mEP monitoring. METHODS: Two hundred sixty-four patients undergoing CEA using general anesthesia with monitoring of bilateral mSSEPs, tSSEPs, and tcMEPs were retrospectively reviewed between 2009 and 2012. The rates of successful assessment of mEPs were investigated, and the rate of false-negative mEP results was analyzed. Different time periods (T1--time of clamping, T2--clamping to significant mEP changes, T3--significant mEP change to intervention, and T4--intervention to recovery of EP) were tested using Welch t test for significant association with postoperative motor deficit. RESULTS: (1) Multimodal EP monitoring was achieved in 241 patients (91.3%, point estimate [PE] 0.91, confidence interval [CI] 0.87 to 0.94), whereas none of the modalities were recordable in one case (PE 0.0038, CI 0.0002 to 0.019). Additionally, tSSEP was not recordable in 21 patients (PE 0.08, CI 0.05 to 0.12), and we found one case of isolated failure of tcMEP recording (PE 0.0038, CI 0.0002 to 0.019). (2) False-negative mEP results were found in 1 patient (0.4%; PE 0.0038, CI 0.0002 to 0.019). Significant mEP changes occurred in 32 patients (12.1%), and thus, arterioarterial shunt was performed in 17 (6.4%) patients. Eleven patients (4.2%) showed transient and 1 showed permanent postoperative motor deficit. (3) There was no significant difference regarding any of the time periods associated with ICA cross-clamping and postoperative alteration of motor function (T1: P = 0.19, CI -30.1 to 6.8 minutes; T2: P = 0.38, CI -23 to 9.5 minutes; T3: P = 0.25, -9.7 to 2.8 minutes; T4: P = 0.42, CI to -15.5 to 7.0 minutes). CONCLUSIONS: Multimodal EP monitoring is applicable during CEA. The 0.4% false-negative rate suggests an advantage of mEP monitoring when compared with isolated mSSEP monitoring. Our data suggest that periods of time during cross-clamping were not significantly associated with postoperative motor deficit. However, the small number of patients limits the conclusiveness of these findings. mEP monitoring could not prevent a postoperative motor deficit in all patients, but our results suggest that it is a useful adjunct to mSSEP monitoring.

Outcomes of combined somatosensory evoked potential, motor evoked potential, and electroencephalography monitoring during carotid endarterectomy.

BACKGROUND: While much has been written about multiple methods of neuromonitoring during carotid endarterectomy (CEA), there has been relatively little discussion of the use of triple monitoring via somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in conjunction with electroencephalography (EEG). Our objective was to evaluate the rate of detection and prevention of neurologic events by multinerve SEP, MEP, and EEG in patients undergoing CEA while under general anesthesia. METHODS: A prospective study of 181 consecutive patients undergoing CEA between June 2005 and September 2010 was reviewed. Intraoperative changes, including a 50% reduction in the amplitude of SEP waveforms, loss of MEP, and/or a 50% change in EEG frequency were noted as indications for shunting. This was correlated with the actual use of intraoperative shunting and postoperative neurologic sequelae at both 24 hours and 30 days. Median and tibial nerve SEPs and MEPs were also correlated. RESULTS: Eleven patients (6%) experienced intraoperative monitoring changes (SEP: 11/11; MEP: 6/11). Five of 11 patients with MEP/SEP changes underwent shunting, while the other 6 had normalization with the elevation of their blood pressure. Of the 11 patients that had neurophysiologic changes, 54% (6/11) were patients with symptomatic disease. No patients had significant EEG changes. The total shunt rate was 2.7% (5/181). No postoperative neurologic sequelae were noted. CONCLUSION: The ratio of shunting at 2.7% is equal to the lowest rates reported in the awake patient literature. Interestingly, the predicted synergy of multimodality monitoring cannot be directly attributed to an increased specificity resulting from the addition of SEP and MEP to EEG, because no patients had EEG changes. In addition, in today's cost-conscious world of health care, our results do not justify implementing this particular technique of neuromonitoring across the board-but it is apparent that the combination of these 3 modalities is both safe and effective with potential applications in symptomatic patients.

Use of NEedle Versus suRFACE Recording Electrodes for Detection of Intraoperative Motor Warnings: A Non-Inferiority Trial. The NERFACE Study Part II.

In the NERFACE study part I, the characteristics of muscle transcranial electrical stimulation motor evoked potentials (mTc-MEPs) recorded from the tibialis anterior (TA) muscles with surface and subcutaneous needle electrodes were compared. The aim of this study (NERFACE part II) was to investigate whether the use of surface electrodes was non-inferior to the use of subcutaneous needle electrodes in detecting mTc-MEP warnings during spinal cord monitoring. mTc-MEPs were simultaneously recorded from TA muscles with surface and subcutaneous needle electrodes. Monitoring outcomes (no warning, reversible warning, irreversible warning, complete loss of mTc-MEP amplitude) and neurological outcomes (no, transient, or permanent new motor deficits) were collected. The non-inferiority margin was 5%. In total, 210 (86.8%) out of 242 consecutive patients were included. There was a perfect agreement between both recording electrode types for the detection of mTc-MEP warnings. For both electrode types, the proportion of patients with a warning was 0.12 (25/210) (difference, 0.0% (one-sided 95% CI, 0.014)), indicating non-inferiority of the surface electrode. Moreover, reversible warnings for both electrode types were never followed by permanent new motor deficits, whereas among the 10 patients with irreversible warnings or complete loss of amplitude, more than half developed transient or permanent new motor deficits. In conclusion, the use of surface electrodes was non-inferior to the use of subcutaneous needle electrodes for the detection of mTc-MEP warnings recorded over the TA muscles.

Monitoring cerebellopontine angle and skull base surgeries.

Cerebellopontine angle (CPA) surgery represents a challenge for neurosurgeons due to the high risk of iatrogenic injury of vital neurological structures. Therefore, important efforts in improving the surgical techniques and intraoperative neurophysiology have been made in the last decades. We present a description and review of the available methodologies for intraoperative neuromonitoring and mapping during CPA surgeries. There are three main groups of techniques to assess the functional integrity of the nervous structures in danger during these surgical procedures: (1) Electrical identification or mapping of motor cranial nerves (CNs), which is essential in order to locate the nerve in their different parts during the tumor resection; (2) Monitoring, which provides real-time information about functional integrity of the nervous tissue; and (3) Brainstem reflexes including blink reflex, masseteric reflex, and laryngeal adductor reflex. All these methods facilitate the removal of lesions and contribute to notable improvement in functional outcome and permit on the investigation of their physiopathology in certain neurosurgically treated diseases. Such is the case of hemifacial spasm (HFS). We describe the methodology to evaluate the efficacy of microvascular decompression for HFS treatment at the end of this chapter.

Monitoring in carotid endarterectomy.

Cerebral ischemia during carotid endarterectomy occurs via several mechanisms: inadequate collateral blood flow during carotid cross-clamping, thromboembolism due to carotid manipulation, and/or rethrombosis at the surgical site. Perioperative strokes increase not only the morbidity of endarterectomy but also its short- and long-term mortality. However, while several predictors of cerebral ischemia have been identified, precise individual risk is hard to assess. Since nonselective shunting during carotid cross-clamping is neither risk-free nor eliminates perioperative stroke, it is advisable to apply intraoperative monitoring techniques for detection and reversal of cerebral ischemia, which may occur at various stages of the procedure. This chapter addresses the methods available for monitoring, with an emphasis on neurophysiologic techniques, which are preferable given their direct assessment of how a decrease in cerebral blood flow impacts brain function. These include electroencephalography, somatosensory evoked potentials, and transcranial motor evoked potentials. Details regarding the methodology, advantages, disadvantages, and interpretation of these tests will be discussed within the anatomic, physiologic, surgical, and anesthetic contexts.

Intraoperative monitoring of facial corticobulbar motor evoked potentials: Methodological improvement and analysis of 100 patients.

OBJECTIVE: A) To describe an improved methodology for continuously monitoring the functional integrity of facial nerve by eliciting facial corticobulbar motor-evoked potentials (FCoMEP) and B) To establish the prognosis of facial nerve function based on changes in FCoMEP during skull base surgery. METHODS: Intraoperative monitoring of FCoMEP performed in 100 patients. Previously published methodology has been improved upon by a) doing preoperative mapping of the facial nerve, b) facilitating the corticobulbar tract (CBT) by continuous transcranial electrical stimulation (TES) at 2 Hz repetition rate, c) recording from multiple facial nerve innervated muscles, and d) eliciting blink reflex (BR). We analyzed changes in FCoMEP, comparing them with the clinical facial nerve outcome scored with the House-Brackman (HB) scale. RESULTS: The monitorability rate was 100%. Out of 100 patients, nine presented a new facial deficit after surgery. Eight of these showed significant changes in FCoMEP. In four patients FCoMEPs were lost; they presented a complete facial paralysis from which they did not recover. To discriminate the prognosis of patients, ROC analysis identified a cut-off at 65% for FCoMEPs amplitude decrease with a sensitivity of 89% and specificity of 99%. In four patients FCoMEP showed a decrease in amplitude greater than 65%, and they presented mild/moderate facial paresis that was transient. One patient did not present changes in FCoMEP but had a mild facial paresis from which the patient recovered. CONCLUSIONS: The improved methodology allows the maximum rate of monitorability and minimizes false positive and false negative results. This study shows that prognosis of facial nerve may be reliably established based on FCoMEP parameters. SIGNIFICANCE: We improved the previously described methodology for continuously monitoring the functional integrity of the facial nerve by increasing the monitorability rate, and we describe the impact of FCoMEP intraoperative management of facial nerve. This method may permit establishing the short-term and long-term prognosis of facial nerve function in skull base surgery.

Methodology for eliciting the brainstem trigeminal-hypoglossal reflex in humans under general anesthesia.

OBJECTIVE: Brainstem trigeminal-hypoglossal reflexes (THRs), also known as the jaw-tongue reflexes, coordinate the position of the tongue in the mouth in relation to the jaw movement during oromotor behaviors such as mastication, swallowing, vocalization, and breathing. Their use in brainstem surgery however, has never been assessed in spite of its potential benefit possibly due to the lack of a methodology to elicit these reflexes under general anesthesia. METHODS: We proposed a technique to elicit the THRs during total intravenous anesthesia (TIVA) consisting on a V3 infrazygomatic train stimulation paradigm and recording from the Styloglossus (31 patients) and the Genioglossus (21 patients) muscles to elicit long latency responses. RESULTS: The THR was successfully recorded using the V3 stimulation point in 82.1% of patients, of which 96.9% presented a response on the Styloglossus muscle (Jaw-opening reflex) while 0.06% presented a response on the Genioglossus muscle instead (Jaw-closing reflex). CONCLUSIONS: The THRs can be successfully recorded in surgery under general anaesthesia with the predominant reflex seen being the jaw-opening reflex. SIGNIFICANCE: We provide a novel method to elicit the THRs during general anesthesia, which could be of aid in brainstem surgery.

Continuous Laryngeal Adductor Reflex Versus Intermittent Nerve Monitoring in Neck Endocrine Surgery.

OBJECTIVE: Intraoperative neuromonitoring (IONM) techniques aim to identify and potentially prevent nerve injury during surgeries. Prior studies into the efficacy of recurrent laryngeal nerve (RLN) IONM convey mixed results, with some claiming equivalence between IONM and no monitoring at all. The goal of the current study was to compare continuous RLN monitoring using the laryngeal adductor reflex (LAR) to intermittent RLN monitoring (intermittent IONM) to determine whether continuous monitoring reduces the incidence of intraoperative RLN injury during neck endocrine surgeries. METHODS: In this observational, historical case-control study, a historical cohort of patients monitored with intermittent-IONM (group 1, n = 130) were compared to prospectively collected data from consecutive nerves-at-risk monitored continuously with the LAR (LAR-CIONM, group 2, n = 205), at a single center by a single surgeon. The test benefit ratio and relative risk reduction (RRR) for LAR-CIONM over intermittent IONM were calculated. RESULTS: For group 1, nine nerves at risk exhibited intraoperative LOS with transient postoperative vocal fold (VF) hypomobility (n = 2) or immobility (VFI, n = 7). For group 2, two nerves at risk (0.98%) had sudden intraoperative LAR LOS following bipolar cautery, resulting in postoperative transient VFI (P = .004). In each group, there was one case of permanent postoperative VFI. The test benefit rate ratio for LAR-CIONM demonstrated a dramatic effect at 5.23, with an RRR of 81.0%. CONCLUSION: LAR-CIONM significantly decreased rates of postoperative transient VF paralysis and paresis over intermittent IONM alone (P = .004). Surgeons should be aware of the benefits and limitations of intermittent IONM versus CIONM. Intermittent IONM, although useful in nerve mapping and intraoperative decision making, has minimal benefit for the prevention of nerve injury, whereas CIONM can potentially reduce nerve injury rates and improve patient outcomes. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:230-236, 2021.

The short-latency R1 response of the electrical laryngeal adductor reflex contributes to airway protection by initiating glottic closure.

OBJECTIVE: The fundamental role of the short-latency (R1) laryngeal adductor reflex (LAR) response remains unclear with conflicting reports in the literature. This study's primary aim was to objectively determine whether the bilateral R1 response, which was elicited by electrical stimulation of the supraglottic mucosa, triggered bilateral glottis closure. METHODS: Video recording of the LAR in a prospective case series of patients undergoing trans-oral rigid laryngoscopy. The LAR was elicited by electrical stimulation of supraglottic mucosa. The LAR R1 and long-latency (R2) responses in laryngeal adductor musculature were correlated with mechanical vocal fold (VF) adduction in a time-locked manner. A high-speed camera recording 1057 frames per second was used to determine where in the LAR contractile closure the electrical R1 component occurred. RESULTS: Five patients were prospectively enrolled. The R1 response was present in all trials for all patients. The R2 response was recorded in four patients (80%). As assessed by the latency of the R1 response, electrical activation of the adductor muscles always preceded the mechanical onset of VF movement. VF adduction began near the middle of the R1 response in all trials for all patients. The R2 response of the LAR began after visible VF adduction for all patients. CONCLUSIONS: This study provides the first objective evidence that the bilateral R1 response of the electrically elicited LAR is the electrical event that initiates reflex airway closure. SIGNIFICANCE: These results suggest that under total intravenous anesthesia, the larynx preserves its capacity to elicit a LAR, thereby maintaining some protective functions that can prevent airway penetration.

Intraoperative Neurophysiologic Monitoring Correlates with Neurologic Outcome After Endovascular and Surgical Treatment of a Cervical Arteriovenous Malformation.

BACKGROUND: The treatment of spinal intramedullary arteriovenous malformations (AVMs) presents the risk of spinal cord ischemia because of the vascular nidus and their feeding arteries involving and supplying the spinal cord parenchyma. The multimodal approach includes endovascular embolization and microsurgical excision, both benefiting from intraoperative neurophysiologic monitoring. We present a case study of a patient who underwent several staged embolizations and open surgery for microsurgical excision. PATIENT: A 32-year-old man who presented with a recurrent glomus-type intramedullary AVM in the cervical spinal cord, located at the C5-C6 segment, with progressive neurologic deterioration. METHODS: Somatosensory evoked potentials (SEPs) and transcranial motor evoked potentials (MEPs) were performed during three embolizations, a provocative test, and surgery, in addition to D-wave during microsurgical excision. RESULTS: Abolished hand MEP and drop in SEP during a provocative test guided the surgeon to embolize from a safer vessel with no acute neurologic deficit after three embolizations. Before surgery, an angiography showed the left posterior spinal artery supplying the AVM. After resecting the vascular nidus from the spinal parenchyma, left-hand MEP decreased in amplitude and later abolished, and SEP decreased. Interestingly, no D-wave or distal MEPs were affected. Weakness in the left hand immediately and 2 weeks postoperatively advocates for metameric spinal cord ischemia with preservation of long spinal cord pathways. CONCLUSIONS: Intraoperative neurophysiologic monitoring correlates with neurologic outcome after endovascular and surgical treatment of a cervical AVM. Intraoperative monitoring provides continuous functional information of long and metameric spinal cord pathways, which is critical when deciding on the vessel to be embolized and during microsurgical excision where the surgeon is in less control of the AVM hemodynamic flow.

Continuous neuromonitoring during radiofrequency ablation of benign thyroid nodules provides objective evidence of laryngeal nerve safety.

INTRODUCTION: The recurrent laryngeal nerves(RLN) run immediately posterior to the thyroid capsule and could be injured during thyroid radiofrequency ablation(RFA). This study assesses whether RLN functional integrity is altered during RFA using continuous intraoperative neuromonitoring(CIONM). METHODS: Prospective case series of twenty nodules treated with RFA under general anesthesia utilizing the laryngeal adductor reflex(LAR) for CIONM. RESULTS: Thirteen nodules abutted the posterior thyroid capsule and 'danger triangle' for RLN injury. The ablative field did not breach the posterior capsule; 40 W was the maximal power used adjacent to the capsule. No patient experienced significant LAR amplitude alterations. Pre and postoperative laryngoscopy and voice assessments were comparable. At 12 months' median follow-up, no patient displayed posterior nodule regrowth. CONCLUSIONS: This prospective case series supports the premise that benign nodule RFA is safe with regards to RLN functional integrity provided the posterior capsule is not breached by the ablation zone and posterior power is ≤ 40 W.

Quadriplegia, an Unusual Outcome After Anterior Cervical Discectomy and Fusion: A Case Report.

CASE: A 68-year-old woman who underwent a C5 to C6 anterior cervical discectomy and fusion (ACDF) surgery presented with new-onset postoperative quadriplegia. During discectomy, intraoperative neurophysiological monitoring alerted of a spinal cord (SC) dysfunction. The surgery was halted, and measures to ensure adequate SC perfusion were initiated. In the next 2-week follow-up, patient's motor deficit progressively improved. CONCLUSIONS: We report an unusual and devastating outcome of new-onset quadriplegia after an elective ACDF and highlight the relevance of intraoperative monitoring during cervical spine surgery to early recognize and treat SC impending injury.

Neurophysiological monitoring of the laryngeal adductor reflex during cerebellar-pontine angle and brainstem surgery.

OBJECTIVE: To correlate intraoperative changes of the laryngeal adductor reflex (LAR), alone or in combination with corticobulbar motor evoked potential of vocal muscles (vocal-CoMEPs), with postoperative laryngeal function after posterior fossa and brainstem surgery. METHODS: We monitored 53 patients during cerebellar-pontine angle and brainstem surgeries. Vocal-CoMEPs and LAR were recorded from an endotracheal tube with imbedded electrodes or hook-wires electrodes. A LAR significant change (LAR-SC) defined as ≥ 50% amplitude decrement or loss, was classified as either transient or permanent injury to the vagus or medullary pathways by the end of the surgery. RESULTS: All patients with permanent LAR loss (n = 5) or LAR-SC (n = 3), developed postoperative laryngeal dysfunction such as aspiration/pneumonia and permanent swallowing deficits (5.6%). Vocal-CoMEP findings refined postoperative vocal motor dysfunction. All seven patients with transient LAR-SC or loss, reverted by changing the surgical approach, did not present permanent deficits. CONCLUSIONS: Permanent LAR-SCs or loss correlated with postoperative laryngeal dysfunction and predicted motor and sensory dysfunction of the vagus nerve and reflexive medullary pathways. In contrast, a LAR-SC or loss, averted by a timely surgical adjustment, prevented irreversible damage. SIGNIFICANCE: Monitoring of the LAR, with vocal-CoMEPs, may enhance safety to resect complex posterior fossa and brainstem lesions.

Laryngeal adductor reflex hyperexcitability may predict permanent vocal fold paralysis.

Laryngeal adductor reflex-continuous intraoperative neuromonitoring (LAR-CIONM) is a novel method of continuous intraoperative neuromonitoring. In contrast to other vagal nerve monitoring techniques, which elicit a laryngeal compound muscle action potential, LAR-CIONM elicits a laryngeal reflex response (LAR). In 300 nerves at risk monitored with LAR-CIONM, two patients have had postoperative permanent vocal fold immobility (VFI). Both patients exhibited a significant LAR amplitude increase prior to complete loss of signal. No other patients have exhibited LAR hyperexcitability. If confirmed in a larger sample, this represents the first time that a vagal intraoperative neuromonitoring technique can distinguish transient from permanent VFI, which could improve patient outcomes. Laryngoscope, 2019 Laryngoscope, 130:E625-E627, 2020.

Application of different thresholds for instrumentation device testing in minimally invasive lumbosacral spine fixation.

The main aim of this study was evaluating the reliability of stimulus-evoked electromyography (using different thresholds for stimulation of the instrumentation devices) for minimally invasive pedicle screw placement in the lumbosacral spine. A threshold of 5 mA was applied for the pedicle access needle. 7 mA was applied for the tapscrew and pedicle screw stimulation. The existence of threshold differences between vertebral levels was also assessed. All patients underwent postoperative computed tomography (CT) to determine the accuracy of pedicle screw placement. A total of 172 percutaneous pedicle screws were placed in 52 patients. 94.1% of screws were placed at L4, L5 and S1 vertebral levels. No statistically significant differences existed in thresholds of the pedicle access needles, tapscrews and pedicle screws between vertebral levels. In four instances, the pedicle access needle stimulation had a threshold of 5 mA (no breaches were associated). In the rest of occasions, the pedicle access needles had stimulation thresholds above 5 mA. In all instances, tapscrew and pedicle screw thresholds were above 7 mA; the tapscrews and pedicle screws had significantly greater thresholds than the pedicle access needles. No statistically significant differences existed in thresholds between tapscrews and pedicle screws. Postoperative CT imaging revealed one lateral pedicle violation. Both breach rate and false negative rate were 0.5%. No false positive cases were observed. No patients experienced postoperative pedicle screw-related neurologic deficits. A threshold of 5 mA for the pedicle access needle stimulation seems to be safe. Greater than 7 mA should be used for the tapscrew and pedicle screw stimulation.