Improving successful rate of transcranial electrical motor-evoked potentials monitoring during spinal surgery in young children

Are there beneficial effects to hybrid anesthesia*?

As the COVID-19 pandemic increased the use of propofol in the intensive care unit for the management of respiratory sequelae and supply had become a major issue. Indeed, most hospitals in Japan were forced to use propofol only for induction of anesthesia with inhalational maintenance. Large amounts of propofol remain in the syringe which exacerbates the problems by increased waste. I propose that use of low dose propofol in combination with a low concentration inhaled anesthetic as an alternative and call this hybrid anesthesia. Several advantages of hybrid anesthesia are evident in the literature. Volatile anesthesia has several disadvantages such as cancer progression, emergence agitation, marked reduction in motor evoked potentials (MEP), laryngospasm with desflurane and postoperative nausea and vomiting (PONV). Volatile anesthesia exerts some beneficial actions such as myocardial protection and fast emergence with desflurane. In contrast, total intravenous anesthesia (TIVA) provides better survival in patients undergoing radical cancer surgery, reduction in emergence agitation, laryngospasm, PONV and better MEP trace Intraoperative awareness occurs more often during TIVA. When intravenous and volatile anesthesia are combined (hybrid anesthesia), the disadvantages of both methods may be offset by clear advantages. Thus, hybrid anesthesia may, therefore, be a viable anesthetic choice.

A practical guide for anesthetic management during intraoperative motor evoked potential monitoring

Postoperative motor dysfunction can develop after spinal surgery, neurosurgery and aortic surgery, in which there is a risk of injury of motor pathway. In order to prevent such devastating complication, intraoperative monitoring of motor evoked potentials (MEP) has been conducted. However, to prevent postoperative motor dysfunction, proper understanding of MEP monitoring and proper anesthetic managements are required. Especially, a variety of anesthetics and neuromuscular blocking agent are known to attenuate MEP responses. In addition to the selection of anesthetic regime to record the baseline and control MEP, the measures to keep the level of hypnosis and muscular relaxation at constant are crucial to detect the changes of MEP responses after the surgical manipulation. Once the changes of MEP are observed based on the institutional alarm criteria, multidisciplinary team members should share the results of MEP monitoring and respond to check the status of monitoring and recover the possible motor nerve injury. Prevention of MEP-related adverse effects is also important to be considered. The Working Group of Japanese Society of Anesthesiologists (JSA) developed this practical guide aimed to help ensure safe and successful surgery through appropriate anesthetic management during intraoperative MEP monitoring.

Threshold variation of transcranial motor evoked potential with threshold criterion in frontotemporal craniotomy

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Motor threshold can be variable during surgery in TES-MEP.

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The motor threshold in TES-MEP was influenced by intraoperative environmental changes.

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The threshold change was greater on the affected side than on the unaffected side.

Objective

Motor threshold usually varies in the intraoperative motor evoked potential (MEP) by transcranial evoked stimulation (TES). This study investigated the degree of change in the motor threshold before and after surgery in TES-MEP monitoring with threshold criterion. This study aimed to evaluate the threshold change and discuss the factors influencing the motor threshold.

Methods

We retrospectively analyzed TES-MEP monitoring during supratentorial surgery with frontotemporal craniotomy in 72 patients without pre- and postoperative motor weakness. We analyzed the percentage changes between the affected and the unaffected sides, correlating the changes on the two sides.

Results

The percentage change on the affected and the unaffected side was 4.4 ± 15.1% and 0.4 ± 6.5%, respectively. The percentage change on the affected side was significantly larger than that on the unaffected side. A significantly positive correlation between the percentage change on the affected and the unaffected sides was detected.

Conclusion

The threshold for the TES-MEP varied significantly more than that on the unaffected side.

Significance

It is important to understand the characteristics of threshold variation for the evaluation of TES-MEP.

Minimally invasive surgery for resection of ossification of the ligamentum flavum in the thoracic spine

Introduction

Thoracic ossification of the ligamentum flavum (TOLF) is a common cause of progressive thoracic myelopathy. Surgical decompression is commonly used to treat TOLF.

Aim

To evaluate the clinical outcomes of microsurgical decompression of TOLF via a paraspinal approach, using a percutaneous tubular retractor system.

Material and methods

First, three-dimensional (3D) image reconstruction and printed models were made from thin computed tomography scans for each patient. Then, 3D computer-assisted virtual surgery was performed using the 3D reconstruction to calculate the precise location and sizes of the bone window and the angle of insertion of the percutaneous tubular retractor system. In total, 13 patients underwent the surgery through the percutaneous micro channel unilateral vertebral approach under electrophysiological monitoring. Five days after the surgery, increased creatine phosphokinase levels returned to preoperative levels. The Japanese Orthopedic Association (JOA) score was improved and computed tomography reconstruction and magnetic resonance imaging of the thoracic spine showed that decompression was achieved without injuries to the spinal cord or nerve root. The stability of the spine was not affected, nor were any deformities of the spine detected. Finally, nerve functional recovery was achieved with minimal injury to the paraspinal muscle, articulum, spinous process and ligament.

Results

The mean operative time was 98.23 ±19.10 min, and mean blood loss was 19.77 ±5.97 ml. At a mean follow-up of 13.3 months (median: 12 months), the mean JOA score was 7.54 ±1.13 at the final follow-up, yielding a mean RR of 49.10 ±15.71%. Using The recovery rate, 7 (53.85%) patients had good outcomes, 5 (38.46%) patients had a fair outcome, and 1 (7.69%) patient had poor outcomes, indicating significant improvement by the final follow-up examination (p < 0.05).

Conclusions

The 3D printed patient model-based microsurgical resection of TOLF via the paraspinal approach can achieve decompression of the spinal canal with minimal complications, faster recovery and improved stability of the vertebral body.

Comparison of multimodal intraoperative neurophysiological monitoring efficacy in early childhood and school aged children undergoing spinal surgery

OBJECTIVE

The aim of this study was to compare the performance of multimodal intraoperative neurophysiological monitoring (MIONM) in children below and over 6 years of age.

METHODS

43 children, diagnosed with spinal pathologies were divided into two cohorts according to their age and enrolled in the study. Those under the age of 6 consisted group A, whereas those between the age of 6 and 11 consisted group B. All patients underwent spinal surgical procedures according to their diagnosis. A standard anesthesia protocol was given to both groups. Baseline somatosensory evoked potentials (SSEPs) and transcranial electrical motor evoked potentials (tcMEPs) were recorded and evaluated at specific time points for each patient.

RESULTS

Except for the SSEPs in three cases, tcMEPs and SSEPs were recorded for all patients. There was no false-negative whereas 9 false positive recordings due to physiological conditions that all recovered intraoperatively. In 10 patients, MIOMN recorded more than %50 decrement, in which 8 had the kyphosis component. The tcMEPs fully recovered by the end of the operation except for the patient with post-tuberculosis kyphosis. There was no statistically significant difference in the mean threshold values with regard to transcranial stimulus intensity for the tcMEPs between the two groups.

CONCLUSION

Compared to school aged children, both SSEPs, tcMEPs recordings are feasible and MIONM is effective for early childhood patients undergoing spinal surgery.

LEVEL OF EVIDENCE

Level III, Diagnostic Study.

Rare true-positive outcome of spinal cord monitoring in patients under age 4 years

BACKGROUND CONTEXT

Intraoperative monitoring (IOM) is becoming an essential component in spinal surgery, but there are many different viewpoints about it in patients under age 4 years.

PURPOSE

This study aims to report some IOM features in children under age 4 years.

DESIGN/SETTING

This is a retrospective cases study.

PATIENT SAMPLE

A total of 37 children (35.76 months±1.47) and 120 patients with adolescent idiopathic scoliosis (AIS, 14.2 years) were recruited between September 2012 and December 2014.

OUTCOME MEASURES

Relevant monitoring changes were identified as transcranial motor evoked potentials (MEP) or somatosensory evoked potentials (SEP) loss associated with high-risk surgical maneuvers.

METHODS

Motor evoked potential, SEP, and free-run electromyography (free-run EMG) were used for IOM. The IOM parameters (amplitude, latency, and waveform) and monitoring outcomes (signal changes, true positive, and false positive) were mainly analyzed in the patients under age 4 years.

RESULTS

All young patients presented stable MEP (90.6 µV±20.3) and SEP (1.01 µV±0.3) baseline. The baseline success rate (100%) was the same as that in patients with AIS; however, the MEP amplitude of young patients was significantly lower than that of patients with AIS (90.6 µV±20.3 vs. 312.1 µV±25.2, n=120; **p<.01) under the same stimulus parameters. Moreover, children under age 4 years have more monitoring changes (18.9%, 7 of 37), but true-positive findings are rare (0%) in our population.

CONCLUSIONS

Intraoperative monitoring baseline can be obtained satisfactorily in children under age 4 years, but true-positive findings are rare; meanwhile, low MEP amplitude and poor waveforms are common.

Microendoscopic posterior decompression for the treatment of thoracic myelopathy caused by ossification of the ligamentum flavum: a technical report

PURPOSE

Ossification of the ligamentum flavum (OLF) is a common cause of progressive thoracic myelopathy in East Asia. Good surgical results are expected for patients who already show myelopathy. Surgical decompression using a posterior approach is commonly used to treat OLF. This study investigated the use of microendoscopic posterior decompression for the treatment of thoracic OLF.

METHODS

Microendoscopic posterior decompression was performed on 9 patients with myelopathy. Patients had a mean age of 59.8 years and single-level involvement, mostly at the T10-11 and T11-12 vertebrae. Computed tomography and magnetic resonance imaging were used to classify the OLF. A tubular retractor and endoscopic system were used for microendoscopic posterior decompression. Midline and unilateral paramedian approaches were performed in 2 and 7 patients, respectively. Intraoperative motor evoked potentials (MEPs) of 7 patients were monitored. Pre- and postoperative neurological status was evaluated using the modified Japanese Orthopaedic Association (mJOA) score.

RESULTS

Thoracic OLF for all patients were classed as bilateral type with a round morphology. Improvement of MEPs at least one muscle area was recorded in all patients following posterior decompression. A dural tear in one patient was the only observed complication. The mean recovery rate was 44.9 %, as calculated from mJOA scores at a mean follow-up period of 20 months.

CONCLUSIONS

Microendoscopic posterior decompression combined with MEP monitoring can be used to treat patients with thoracic OLF. The optimal surgical indication is OLF at a single vertebral level and of a unilateral or bilateral nature, without comma and tram track signs, and a round morphology.

Neuromonitoring for scoliosis surgery

The use of intraoperative neuromonitoring (IONM) during pediatric scoliosis repair has become commonplace to reduce the risk of potentially devastating postoperative neurologic deficits. IONM techniques include somatosensory evoked potentials, motor evoked potentials, electromyography, and intraoperative wake-up tests. Special considerations for scoliosis repair in pediatric patients include preexisting neurologic deficits and young patients with immature neural pathways in whom neurophysiologic monitoring may prove difficult or unreliable.

Improving safety in spinal deformity surgery: advances in navigation and neurologic monitoring

INTRODUCTION

The treatment of spinal deformities has rapidly changed during the past decade. The advent of new surgical techniques, particularly thoracic pedicle screws and spinal osteotomies, allow more aggressive deformity correction, and require an increased focus on safety.

MATERIALS AND METHODS

Review of the navigation systems and neuromonitoring techniques currently available.

CONCLUSION

Navigation systems today are where intraoperative neuromonitoring was 20 years ago: new, under investigation, not widely accepted, with concerns for cost, safety and efficiency. Navigation enhances the accuracy of pedicle screws placement in deformed spines, reducing the rate of misplaced screws and potential complications. With further use and investigation, navigation, like neuromonitoring, will soon become standard at major spine centers throughout the world.