Bite injuries caused by transcranial electrical stimulation motor-evoked potentials' monitoring: incidence, associated factors, and clinical course

Variability of somatosensory evoked potential and motor evoked potential change criteria in thoracic spinal decompression surgery based on preoperative motor status

BACKGROUND CONTEXT

Combined somatosensory- and motor-evoked potential (SSEP and MEP) changes for predicting prognosis in thoracic spinal surgery have been variably reported.

PURPOSE

We aimed to explore the validity of combined SSEP and MEP for predicting postoperative motor deficits (PMDs) in thoracic spinal decompression surgery (TSDS) and identify a relatively optimal neurophysiological predictor of PMDs in patients based on preoperative motor status.

STUDY SETTING

Retrospective study.

PATIENT SAMPLE

A total of 475 patients were analyzed.

OUTCOME MEASURES

A reduction in muscle strength by more than or equal to one manual muscle testing (MMT) grade postoperatively compared with the preoperative MMT grade was identified as PMDs. Postoperative motor deficits were detected by comparing the preoperative and postoperative physical examination findings in short- and long-term follow-up visits.

METHODS

All patients were divided into two subgroups according to preoperative motor status. The following data were collected: (1) demographic data; (2) IONM (intraoperative neuromonitoring) data; and (3) postoperative motor outcomes. Binary logistic regression analysis was performed to assess the efficacy of IONM change to predict PMDs. A receiver operating characteristic curve (ROC) was used to establish optimal IONM warning criteria.

RESULTS

Ninety-eight patients had severe preoperative motor deficits (Group S), and 377 patients did not (Group N). MEP and SSEP change was effective for predicting PMDs in the short term (p<.01) and long term (p<.01) for TSDS patients. In Group N, the cutoff values for predicting PMDs in the short term were a decrease of 65% in SSEP amplitude and 89.5% in MEP amplitude of the baseline value. Furthermore, the cutoff values for predicting PMDs in the short term were durations of change of 24.5 minutes for SSEP and 32.5 minutes for MEP. In Group S, however, the cutoff values for predicting PMDs in the short term were a decrease of 36.5% in SSEP amplitude and 59.5% in MEP amplitude of the baseline value. Moreover, the critical values for predicting short-term PMDs were durations of change of 16.5 minutes for SSEP and 17.5 minutes for MEP.

CONCLUSIONS

The optimal IONM changes for prediction vary depending on preoperative motor status. Combined SSEP and MEP are excellent for predicting PMDs in TSDS.

Effects of Anesthetic Choice on the Incidence of Transcranial-Motor Potential-Induced Oral Trauma

Transcranial motor-evoked potentials (TcMEPs) play an integral role in assessing motor tract function in surgical procedures where motor function is at risk. However, transcranial stimulation creates a risk for oral trauma. Several studies have reported on distinct factors that can influence the rate of TcMEP-induced oral trauma, but little is known about how an anesthetic regimen can influence this rate. In this retrospective review, we investigated the incidence of oral injury under total intravenous anesthesia (TIVA) and balanced anesthesia in 66,166 cases from 2019 to 2021. There were 295 oral injuries in our sample, yielding an incidence of 0.45%, which is in line with ranges reported in the literature. A total of 222 of the injured patients were sedated with balanced anesthesia, while the remaining 73 were under TIVA anesthetics. This difference in distribution was statistically significant (p < 0.0002). Our findings suggest TIVA is associated with lower risk of oral trauma when TcMEPs are monitored, thereby improving patient safety.

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.

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.

Factors Affecting Transcranial Motor-Evoked Potential Measurements Using Single-Train Stimulation with an Increased Number of Pulses during Adolescent Scoliosis Surgery: A Prospective Observational Study

Measurement of transcranial motor-evoked potentials (TcMEPs) during scoliosis surgery helps detect postoperative new neurological defects. However, TcMEP interpretation is difficult owing to the influence of intraoperative physiological, pharmacological, and time-related factors as well as stimulation conditions. In this study, we aimed to investigate the effect of the abovementioned factors on TcMEP amplitude using single-train stimulation with an increased number of pulses (STS-INP) during adolescent scoliosis surgery; moreover, we evaluated the complications of TcMEP measurement. We included 50 patients and 706 TcMEP measurements. A total of 1412 TcMEP waveforms were analyzed, each on the bilateral abductor pollicis brevis, tibialis anterior, and abductor hallucis muscles. We estimated the mean difference (95% confidence interval (CI)) and predicted mean difference (95% CI) evaluated using the interquartile range of each factor, based on a mixed-effect model with random intercepts for TcMEP amplitude. The predicted mean differences in TcMEP amplitude were clinically small compared with the actual TcMEP amplitude, suggesting that each factor had a limited effect on TcMEP amplitude. No intraoperative bite injuries or seizures were observed. Using STS-INP during adolescent scoliosis surgery may enable accurate measurement of TcMEP amplitude with neither complications nor the influence of various intraoperative factors.

Tongue laceration in a patient taking antiplatelet agents during transcranial motor-evoked potential monitoring: a case report

BACKGROUND

Transcranial motor-evoked potential (Tc-MEP) monitoring is usually performed during surgeries involving a risk of damaging brain motor areas. However, it involves a risk of bite injuries. We report a case of severe tongue laceration from Tc-MEP stimulation during carotid endarterectomy (CEA) in a patient taking antiplatelet agents.

CASE PRESENTATION

A 74-year-old man on antiplatelet therapy was scheduled for CEA under general anesthesia with intraoperative Tc-MEP monitoring. Bite blocks were not inserted. Postoperatively, we observed a tongue laceration with severe bleeding, which was sutured. The difficulties in tongue movement persisted for ≥ 1 month postoperatively.

CONCLUSIONS

Bite injuries during Tc-MEP may induce severe bleeding in patients on antiplatelets. The complications of tongue bite injuries may persist, decreasing the patients' quality of life. Hence, during Tc-MEP monitoring, it is important to use soft bite blocks and to check the patient's face and the position of the tracheal tube intraoperatively.

Novel use of transesophageal echocardiography to optimize hemodynamics and patient positioning during prone scoliosis surgery and safety considerations in the setting of intraoperative neuromonitoring: a case report

PURPOSE

The prone position can lead to anatomical compression of the thoracic cavity resulting in reduced cardiac output, especially in the context of chest wall deformities commonly present in patients with scoliosis. There are no protocols for using transesophageal echocardiography (TEE) to optimize prone positioning and for safe use of TEE during cases requiring neuromonitoring.

CLINICAL FEATURES

We present a case of a 23-yr-old male with Cornelia de Lange syndrome undergoing elective posterior spinal fusion for syndromic scoliosis who developed severe refractory hypotension and cardiac arrest in the prone position. After hemodynamic stabilization in the intensive care unit, the patient returned to the operating room on postoperative day 2 for completion of his spinal fusion. Transesophageal echocardiography determined the optimal position of longitudinal bolster placements associated with minimal left ventricular compression in the supine position. The patient was then proned and intraoperative hemodynamics during the second surgery remained stable. Owing to the special considerations of using TEE in the prone position with neuromonitoring, we describe technical aspects to consider to protect the equipment and patient.

CONCLUSION

Patients with compliant chest walls or thoracic deformities are at risk of hemodynamic instability in the prone position. Intraoperative TEE can be used in the supine patient prior to proning to determine optimal longitudinal bolster positioning to minimize cardiac compression. Transesophageal echocardiography used during spine surgery in the prone position with neuromonitoring and motor-evoked potentials requires special considerations for patient safety.

Transcranial electric stimulation motor evoked potentials for cervical spine intraoperative monitoring complications: systematic review and illustrative case of cardiac arrest

PURPOSE

We show a systematic review of known complications during intraoperative neuromonitoring (IONM) using transcranial electric stimulation motor evoked potentials (TES-MEP) on cervical spine surgery, which provides a summary of the main findings. A rare complication during this procedure, cardiac arrest by cardioinhibitory reflex, is also described.

METHODS

Findings of 523 scientific papers published from 1995 onwards were reviewed in the following databases: CENTRAL, Cochrane Library, Embase, Google Scholar, Ovid, LILACS, PubMed, and Web of Science. This study evaluated only complications on cervical spine surgery undergoing TES-MEP IONM.

RESULTS

The review of the literature yielded 13 studies on the complications of TES-MEP IONM, from which three were excluded. Five studies are case series; the rest are case reports. Overall, 169 complications on 167 patients were reported in a total of 38,915 patients, a global prevalence of 0.43%. The most common complication was tongue-bite in 129 cases, (76.3% of all complication events). Tongue-bite had a prevalence of 0.33% (CI 95%, 0.28-0.39%) in all patients on TES-MEP IONM. A relatively low prevalence of severe complications was found: cardiac-arrhythmia, bradycardia and seizure, the prevalence of this complications represents only one case in all the sample. Alongside, we report the occurrence of cardiac arrest attributable to TES-MEP IONM.

CONCLUSIONS

This systematic review shows that TES-MEP is a safe procedure with a very low prevalence of complications. To our best knowledge, asystole is reported for the first time as a complication during TES-MEP IONM.

Safety issues during surgical monitoring

While intra-operative neuro-physiologic assessment and monitoring improve the safety of patients, its use may also introduce new risks of injuries. This chapter looks at the electric safety of equipment and the potential hazards during the set-up of the monitoring. The physical and functional physiologic effects of electric shocks and stimulation currents, standards for safety limits, and conditions for tissue damage are described from basic physical principles. Considered are the electrode-tissue interface in relation to electrode dimensions and stimulation parameters as applied in various modalities of evoked sensory and motor potentials as to-date used in intra-operative monitoring, mapping of neuro-physiologic functions. A background is given on circumstances for electric tissue heating and heat drainage, thermal toxicity, protection against thermal injuries and side effects of unintended activation of neural and cardiac tissues, adverse effects of physiologic amplifiers from transcranial stimulation (TES) and excitotoxicity of direct cortical stimulation. Addressed are safety issues of TES and measures for prevention. Safety issues include bite and movement-induced injuries, seizures, and after discharges, interaction with implanted devices as cardiac pacemaker and deep brain stimulators. Further discussed are safety issues of equipment leakage currents, protection against electric shocks, and maintenance.

How to Make a Do-It-Yourself, Disposable Bite Guard Using Easily Available Materials, to Prevent Tongue and Lip Injuries, During Motor Evoked Potential Monitoring in Neurosurgery

We describe a do-it-yourself method of making a bite guard, using pairs of Foley catheters and surgical gloves to prevent tongue, lip, and other injuries during the monitoring of transcranially elicited motor evoked potential. We have used it in five cases, and have found that the hack is particularly cost-effective and reliable. We describe the technique here using multiple photographs.