Intraoperative Neuromonitoring of Motor-Evoked Potentials in Infants Undergoing Surgery of the Spine and Spinal Cord

Impact of low-dose sevoflurane with propofol-based anesthesia on motor-evoked potentials in infants: a single-arm crossover pilot study

PURPOSE

The influence of anesthetic interactions on motor-evoked potentials in infants has rarely been reported. In infants, adding a small dose of sevoflurane to propofol-based total intravenous anesthesia is reasonable for reducing propofol administration. We collected preliminary data regarding the effect of low-dose sevoflurane in propofol-based total intravenous anesthesia on motor-evoked potentials in infants.

METHODS

This pilot interventional study included 10 consecutive infants requiring motor-evoked potentials between January 2023 and March 2024. The motor-evoked potential amplitudes in the upper and lower extremities were recorded twice when general anesthesia was maintained using (1) propofol-based total intravenous anesthesia and (2) 0.1-0.15 age-adjusted minimum alveolar concentration sevoflurane + propofol-based total intravenous anesthesia.

RESULTS

The motor-evoked potential amplitude in the right upper extremity was not significantly different after the addition of a small dose of sevoflurane [192 (75.3-398) μV, 121 (57.7-304) μV, P = 0.19]. All the motor-evoked potential amplitudes in the right lower extremity (quadriceps femoris, anterior tibialis, and gastrocnemius muscles) were significantly attenuated by adding a small dose of sevoflurane (median [interquartile range]: 47.9 [35.4-200] μV, 25.2 [12.4-55.3] μV, P = 0.014; 74.2 [51.9-232] μV, 31.2 [2.7-64] μV, P = 0.0039; 29.8 [20-194] μV, 9.9 [3.8-92.4] μV, P = 0.0039, respectively). Similar results were observed in the left lower extremities.

CONCLUSION

Adding even 0.1-0.15 age-adjusted minimum alveolar concentration sevoflurane to propofol-based total intravenous anesthesia attenuated the motor-evoked potential amplitudes in the lower extremities. A further prospective interventional study with an appropriate sample size is required to investigate the study hypothesis.

Transcranial electrical evoked muscle potentials for pediatric neurosurgery: scoping review of stimulation techniques and success rates

PURPOSE

The background of this scoping review is that pediatric neurosurgery in the vicinity of motor pathways is associated with the risk of motor tract damage. By measuring transcranial electrical evoked potentials in muscles (electromyogram) or from the spinal cord (epidural D-wave) functional disorders and impending damage can be detected during surgery and countermeasures can be initiated. The objective was to summarize stimulation techniques of transcranial electrical stimulation and the success rate of motor evoked potentials exclusively in children undergoing neurosurgery.

METHODS

The data source was a literature search for reports meeting the suitability criteria (original articles and case series including motor evoked potentials and pediatric neurosurgery).

RESULTS

Twenty-four articles meeting suitability criteria were retrieved. The most common primary electrode positions for electrical stimulation were at C3 vs. C4 and C1 vs. C2 according to the 10-20-system of EEG. Single trains of 1 to 9 pulses with voltages from 160 to 900 V and pulse durations from 50 to 500 µs were applied for voltage-controlled stimulation. Interstimulus intervals ranged from 0.1 to 9.9 ms. Signals were filtered with high-pass filters between 1.5 and 300 Hz and low-pass filters between 500 and 5000 Hz. The overall rate of successful stimulation and measurement was 90.5% (N = 769).

CONCLUSION

A broad range of stimulation parameters was used for transcranial electrical evoked potentials. Measurable potentials were obtained in most patients. Consideration of safety precautions is an important implication to avoid adverse events by application of high voltage to the motor cortex.

Pediatric Intraoperative Neurophysiological Monitoring and Long-Term Outcomes in a Developing Country

PURPOSE

Pediatric intraoperative neurophysiological monitoring (IONM) has been shown to be effective in preventing and reversing postoperative neurological deficits in developed countries. There are currently no published studies from developing countries that describe neurophysiological findings and postoperative outcomes. Our study aims to address these gaps in children undergoing neurosurgical procedures in a single center.

METHODS

We conducted a retrospective study of case series of children who underwent IONM (2014-2020) in the State of Mexico, Mexico. Sociodemographic characteristics, IONM modalities, changes during procedures, and short-term and long-term postoperative results were recorded. Descriptive statistics were used.

RESULTS

We included 35 patients (≤18 years of age), 57% (20/35) boys. A relative increase of up to 5 times in the use of IONM is observed from 2014 (5.7%) to 2020 (25.7%) in our center. The most frequent preoperative pathologies were located at the infratentorial cranium (40%), followed by the spine and spinal cord (37.1%). The IONM modalities were as follows: free-running EMG 94.3%, transcranial electrical stimulation motor-evoked potentials 91.4%, somatosensory-evoked potentials 85.7%, triggered EMG 28.6%, EEG 25.7%, and visual-evoked potentials 5.7%. Only in 8.3%, we did not obtain sufficient evoked potential baseline signals. At 24 hours postoperatively true negatives were 100%. Long-term follow-up was completed in 22/35 (63%) at 3 months, 12/35 (34.2%) at 6 months, and 5/35 (14.3%) at 12 months with progressive motor and sensory improvement.

CONCLUSIONS

Pediatric multimodal IONM in neurosurgeries from a single center in a developing country is mainly used in pathologies of the posterior fossa, spine, and spinal cord, with true negatives in 100% of those monitored, preventing and avoiding postoperative sequelae.

Impact of low-dose sevoflurane with propofol-based anaesthesia on motor-evoked potentials in infants: protocol for a single-centre randomised controlled study

INTRODUCTION

Motor-evoked potentials (MEP) are widely used to mitigate the risk of nerve injury resulting from surgical manipulation. Infants are more susceptible to anaesthetics that suppress MEP because of the immaturity of their nervous structures. Current evidence of the impact of the interaction between a small dose of sevoflurane and propofol-based total intravenous anaesthesia (TIVA) on MEP in infants is controversial. This current study aims to evaluate the impact of the coadministration of low-dose sevoflurane with propofol-based TIVA on MEP in infants.

METHODS AND ANALYSIS

A randomised controlled study will be conducted at a single tertiary care children's hospital in Japan between July 2024 and June 2029. Children between 35 and 87 weeks of postconceptual age undergoing spinal surgery requiring MEP under general anaesthesia will be enrolled in this study. The participants will be randomly allocated into two groups: propofol+remifentanil with (intervention group) or without (control group) low-dose sevoflurane (0.10-0.15 age-adjusted minimum alveolar concentration). MEP top-to-bottom amplitudes will be measured at two chronological points: T1 (first transcranial MEP (TcMEP) recording), T2 (second TcMEP recording) in the same patient. The primary and secondary endpoints will be a reduction in MEP amplitudes (T1-T2) in the right upper and lower extremities between the control and intervention groups, respectively. The sample size was calculated to be a total of 40 based on the preliminary data of 10 infants, which showed a 35% reduction in mean values of MEP amplitudes in the right adductor muscle (SD=31) with a 10% assumed dropout rate.

ETHICS AND DISSEMINATION

The study protocol was approved by the Institutional Review Board of the Aichi Children's Health and Medical Center (2022058). The results will be reported in a peer-reviewed journal at the relevant academic conference.

TRIAL REGISTRATION NUMBER

jRCT1041230094.

Impact of various anesthetic regimens on motor-evoked potentials in infants undergoing spinal surgery: A case series

Motor-evoked potential (MEP) monitoring is commonly used in children. MEP monitoring in infants is difficult due to smaller signals requiring higher stimulation voltages. There is limited information on the effect of different anesthetics on MEP monitoring in this age group. This case series describes the effect of different anesthetic regimens on MEP monitoring in infants. Patients <1 year of age who underwent spinal surgery with MEP monitoring between February 2022 and July 2023 at a single tertiary care children hospital were reviewed. The motor-evoked potential amplitudes were classified into 4 levels based on the voltage in the upper and lower limbs (none, responded, acceptable, sufficient). "Acceptable" or "sufficient" levels were defined as successful monitoring. A total of 19 infants were identified, involving 3 anesthesia regimens: 4/19 (21.1%) cases were anesthetized with propofol/remifentanil total intravenous anesthesia (TIVA), 3/19 (15.8%) with propofol/remifentanil/low-dose sevoflurane and another 12/19 (63.2%) cases who initially received propofol/remifentanil/sevoflurane and were converted to propofol/remifentanil anesthesia intraoperatively. The 4 cases with propofol/remifentanil showed 20/32 (62.5%) successful monitoring points. In contrast, 6/24 (25%) successful points were achieved with propofol/remifentanil intravenous anesthesia/0.5 age-adjusted minimum alveolar concentration sevoflurane. In 12 cases converted from propofol/remifentanil/low-dose inhalational anesthetics to TIVA alone, successful MEP monitoring points increased from 46/96 (47.9%) to 81/96 (84.4%). Adding low-dose inhalation anesthetic to propofol-based TIVA suppresses MEP amplitudes in infants. The optimal anesthetic regimen for infants requires further investigation.

Low-dose sevoflurane co-administered with propofol-based general anaesthesia obliterates intra-operative neurophysiological monitoring in an infant

The influence of general anaesthetic agents on intra-operative neurophysiological monitoring in neonates and infants has rarely been reported. Propofol-based anaesthesia is recommended to avoid suppression of neurophysiological monitoring. However, the administration of propofol in children undergoing prolonged procedures, especially those younger than six months, should be carefully controlled due to the potential risk of propofol infusion syndrome. Adding a small dose of inhalational anaesthetic can be an option to reduce propofol requirements. Recent guidelines in Japan suggest limiting inhalational anaesthetics to less than 0.5 minimum alveolar concentrations when co-administered with low-dose propofol during intra-operative neuromonitoring. However, there is still insufficient evidence regarding the impact of sevoflurane on neurophysiological monitoring when co-administered with propofol in infants. This report describes a case of a three-month-old infant undergoing spinal lipoma resection in which there was a dramatic suppression of neurophysiological monitoring with the addition of 0.35-0.45% sevoflurane to propofol-based anaesthesia.

Anesthesia management of neonates and infants requiring intraoperative neurophysiological monitoring: A concise review

Intraoperative neurophysiological monitoring is currently used to prevent intraoperative spinal cord and nerve injuries during neonatal and infant surgeries. However, its use is associated with some issues in these young children. The developing nervous system of infants and neonates requires higher stimulation voltage than adults to ensure adequate signals, thereby necessitating reduced anesthesia dose to avoid suppressing motor and somatosensory-evoked potentials. Excessive dose reduction, however, increases the risk of unexpected body movement when used without neuromuscular blocking drugs. Most recent guidelines for older children and adults recommend total intravenous anesthesia with propofol and remifentanil. However, the measurement of anesthetic depth is less well understood in infants and neonates. Size factors and physiological maturation cause pharmacokinetics differences compared with adults. These issues make neurophysiological monitoring in this young population a challenge for anesthesiologists. Furthermore, monitoring errors such as false-negative results immediately affect the prognosis of motor and bladder-rectal functions in patients. Therefore, anesthesiologists need to be familiar with the effects of anesthetics and age-specific neurophysiological monitoring challenges. This review provides an update regarding available anesthetic options and their target concentration in neonates and infants requiring intraoperative neurophysiological monitoring.

Successful Neonatal, Intraoperative Neuromonitoring in the Surgical Correction of a Thoracic Dermal Sinus Tract: Technical Note

INTRODUCTION

Intraoperative neuromonitoring (IONM) is commonly used during surgery of the spine and spinal cord for early surveillance of iatrogenic injury to the central and peripheral nervous system. However, for infants and young children under 3 years of age, the use of IONM is challenging due to incomplete central and peripheral myelination.

CASE PRESENTATION

We report a case of a T4-T6 dermal sinus tract (DST) that was resected on day of life 23, with the successful use of IONM.

CONCLUSION

To our knowledge, this is the youngest reported case of the use of IONM in the surgical correction of a DST in a neonatal patient. This case demonstrates the potential efficacy of IONM in neonatal spine surgery and the techniques used to adapt the technology to an immature nervous system.

Feasibility and diagnostic accuracy of intra-operative monitoring of motor evoked potentials in children <2 years of age undergoing tethered cord surgery: results in 100 children

OBJECTIVE

This study documents the monitorability using different anesthesia regimes and accuracy of muscle motor evoked potentials (mMEPs) in children ≤2 years of age undergoing tethered cord surgery (TCS).

METHODS

Intraoperative mMEP monitoring was attempted in 100 consecutive children, ≤2 years of age, undergoing TCS. MEP monitoring was done under 4 different anesthetic regimes: (Total intravenous anesthesia (TIVA); balanced anesthesia with sevoflurane and ketamine; balanced anesthesia with isoflurane and ketamine; and balanced anesthesia with sevoflurane). Factors analyzed for their effect on monitorability were: age, neurological deficits, type of anesthesia, and the number of pulses used for stimulation.

RESULTS

Baseline mMEPs were obtained in 87% children. Monitorability of mMEPs was similar in children ≤1 year and 1-2 years of age (85.7% and 87.5%). In multivariate analysis, anesthesia regime was the only significant factor predicting presence of baseline mMEPs. Children undergoing TIVA (p=0.02) or balanced anesthesia with a combination of propofol, sevoflurane, and ketamine (p=0.05) were most likely to have baseline mMEPs. mMEPs had a sensitivity of 97.4%, specificity of 96.4%, negative predictive value of 98.2% and accuracy of 96.8%.

CONCLUSIONS

Baseline mMEPs were obtained in >85% of children ≤2 years of age including those who had motor deficits. TIVA and balanced anesthesia with sevoflurane and ketamine are ideal for mMEP monitoring. mMEPs have a high accuracy although, false positive and false negative results can occasionally be experienced.

Anesthesia management during meningomyelocele repair alongside motor-evoked potentials in a newborn and a small infant

Intraoperative neuromonitoring has become an increasingly commonly applied practice during surgical operations for preventing formation of neurological damage. Although it has been used on adults for a long time, the benefits and techniques of applying it in small children are not clear. We applied two different anesthesia protocols during meningomyelocele repair alongside motor-evoked potentials in a newborn and a small infant. We discussed our anesthesia management method and the effects of anesthesia on intraoperative neuromonitoring in our two very young cases in only one of which we obtained significant records.

Extramuscular Recording of Spontaneous EMG Activity and Transcranial Electrical Elicited Motor Potentials in Horses: Characteristics of Different Subcutaneous and Surface Electrode Types and Practical Guidelines

Introduction

Adhesive surface electrodes are worthwhile to explore in detail as alternative to subcutaneous needle electrodes to assess myogenic evoked potentials (MEP) in human and horses. Extramuscular characteristics of both electrode types and different brands are compared in simultaneous recordings by also considering electrode impedances and background noise under not mechanically secured (not taped) and taped conditions.

Methods

In five ataxic and one non-ataxic horses, transcranial electrical MEPs, myographic activity, and noise were simultaneously recorded from subcutaneous needle (three brands) together with pre-gelled surface electrodes (five brands) on four extremities. In three horses, the impedances of four adjacent-placed surface-electrode pairs of different brands were measured and compared. The similarity between needle and surface EMGs was assessed by cross-correlation functions, pairwise comparison of motor latency times (MLT), and amplitudes. The influence of electrode noise and impedance on the signal quality was assessed by a failure rate (FR) function. Geometric means and impedance ranges under not taped and taped conditions were derived for each brand.

Results

High coherencies between EMGs of needle-surface pairs degraded to 0.7 at moderate and disappeared at strong noise. MLTs showed sub-millisecond simultaneous differences while sequential variations were several milliseconds. Subcutaneous MEP amplitudes were somewhat lower than epidermal. The impedances of subcutaneous needle electrodes were below 900 Ω and FR = 0. For four brands, the FR for surface electrodes was between 0 and 80% and declined to below 25% after taping. A remaining brand (27G DSN2260 Medtronic) revealed impedances over 100 kΩ and FR = 100% under not taped and taped conditions.

Conclusion

Subcutaneous needle and surface electrodes yield highly coherent EMGs and TES-MEP signals. When taped and allowing sufficient settling time, adhesive surface-electrode signals may approach the signal quality of subcutaneous needle electrodes but still depend on unpredictable conditions of the skin. The study provides a new valuable practical guidance for selection of extramuscular EMG electrodes. This study on horses shares common principles for the choice of adhesive surface or sc needle electrodes in human applications such as in intraoperative neurophysiological monitoring of motor functions of the brain and spinal cord.

Neonatal intraoperative neuromonitoring in thoracic myelocystocele: a case report

Thoracic myelocystocele are extremely rare, non-terminal, closed neural tube defects. Intraoperative neuromonitoring (IONM) is a mainstay of pediatric spinal surgery. However, in neonates and infants, incomplete myelination of the corticospinal tract presents unique challenges to successful use of IONM in this vulnerable patient population. Surgery can often be delayed until patients are older, but there are circumstances in which early intervention is necessary. We report a case of T6 myelocystocele resection and wound closure in an infant on day of life 15 with the use of IONM. To our knowledge, this is the youngest reported patient to undergo successful IONM in the spinal cord. Given that the majority of thoracic myelocystoceles present without any neurological deficits, early intervention for this rare closed spinal dysraphism is sometimes necessary. This case study reports the possibility of IONM use in neonatal patients and also highlights the techniques that make its use more possible.