Diagnostic utility of different types of somatosensory evoked potential changes in pediatric idiopathic scoliosis correction surgery

PURPOSE

To evaluate the diagnostic accuracy of intraoperative somatosensory evoked potential (SSEP) monitoring and types of SSEP changes in predicting the risk of postoperative neurological outcomes during correction surgery for idiopathic scoliosis (IS) in the pediatric age group (≤ 21 years).

METHODS

Database review was performed to identify literature on pediatric patients with IS who underwent correction with intraoperative neuromonitoring. The sensitivity, specificity, and diagnostic odds ratio (DOR) of transient and persistent SSEP changes and complete SSEP loss in predicting postoperative neurological deficits were calculated.

RESULTS

Final analysis included 3778 patients. SSEP changes had a sensitivity of 72.9%, specificity of 96.8%, and DOR of 102.3, while SSEP loss had a sensitivity of 41.8%, specificity of 99.3%, and DOR of 133.2 for predicting new neurologic deficits. Transient and persistent SSEP changes had specificities of 96.8% and 99.1%, and DORs of 16.6 and 59, respectively.

CONCLUSION

Intraoperative SSEP monitoring can predict perioperative neurological injury and improve surgical outcomes in pediatric scoliosis fusion surgery.

LEVEL OF EVIDENCE

Level 2. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Tethered cord release in patients after open fetal myelomeningocele closure: intraoperative neuromonitoring data and patient outcomes

PURPOSE

The purpose of the study was to better understand the clinical course and impact of tethered cord release surgery on patients who have previously undergone open spinal dysraphism closure in utero.

METHODS

This is a single-center retrospective observational study on patients undergoing tethered cord release after having previously had open fetal myelomeningocele (MMC) closure. All patients underwent tethered cord release surgery with a single neurosurgeon. A detailed analysis of the patients' preoperative presentation, intraoperative neuromonitoring (IONM) data, and postoperative course was performed.

RESULTS

From 2009 to 2021, 51 patients who had previously undergone fetal MMC closure had tethered cord release surgery performed. On both preoperative and postoperative manual motor testing, patients were found to have on average 2 levels better than would be expected from the determined anatomic level from fetal imaging. The electrophysiologic functional level was found on average to be 2.5 levels better than the anatomical fetal level. Postoperative motor levels when tested on average at 4 months were largely unchanged when compared to preoperative levels. Unlike the motor signals, 46 (90%) of patients had unreliable or undetectable lower extremity somatosensory evoked potentials (SSEPs) prior to the tethered cord release.

CONCLUSION

Tethered cord surgery can be safely performed in patients after open fetal MMC closure without clinical decline in manual motor testing. Patients often have functional nerve roots below the anatomic level. Sensory function appears to be more severely affected in patients leading to a consistent motor-sensory imbalance.

The effect of hydroxyapatite on titanium pedicle screw resistance: an electrical model

BACKGROUND CONTEXT

Intraoperative detection of a pedicle wall breach implicitly reduces surgical risk, but the reliability of intraoperative neuromonitoring has been contested. Hydroxyapatite (HA) has been promulgated to increase pedicle screw resistance and negatively influence the accuracy of electromyography.

PURPOSE

The primary purpose of this experiment is to evaluate the effect of HA on pedicle screw electrical resistance using a controlled laboratory model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Stimulation of pedicle screws was performed in normal saline (0.9% NaCl). The experimental group included 8 HA coated (HAC) pedicle screws and matched manufacturer control pedicle screws without HAC (Ti6Al4V). All screws were stimulated at 5, 10-, 15-, 20-, and 25-mm submersion depths. Circuit current return was recorded, and pedicle screw electrical resistance was calculated according to Ohm's Law. Data were assessed for normality and variance. Mann-Whitney U and Kruskal-Wallis tests compared groups with Bonferroni correction for multiple testing. Effect size is reported with 95% confidence intervals (95CI). p values <.05 were considered significant.

RESULTS

Current return was detected for all screws (N=24) following subclinical 8.5 µA stimulation at 5, 10-, 15-, 20-, and 25-mm submersion depths (N=144). The effect estimate of HA on pedicle screw electrical resistance is -0.07 (-0.17 to 0.01 95CI). The estimated effect of HA on pedicle screw electrical resistance did not differ across manufacturers. Electrical resistance values were inversely related to submersion depth. Electrical resistance values were lower in the experimental group at 10 mm (p=.04), 15 mm (p=.04), and 25 mm (p=.02) submersion depths. The HA effect ranged from -0.03 to -0.08 as submersion depth varied.

CONCLUSIONS

We found no evidence that HA increased pedicle screw electrical resistance in a matched manufacturer control laboratory model. Electrical stimulation of pedicle screws may be reliable for pedicle breach detection in the presence of HA. Future research should investigate if laboratory findings translate to clinical practice and confirm that electrical stimulation of pedicle screws is a reliable method to detect pedicle breach in the presence of HA.

Intraoperative lateral rectus electromyographic recordings optimized by deep intraorbital needle electrodes

OBJECTIVE

We demonstrate the advantages and safety of long, intraorbitally-placed needle electrodes, compared to standard-length subdermal electrodes, when recording lateral rectus electromyography (EMG) during intracranial surgeries.

METHODS

Insulated 25 mm and uninsulated 13 mm needle electrodes, aimed at the lateral rectus muscle, were placed in parallel during 10 intracranial surgeries, examining spontaneous and stimulation-induced EMG activities. Postoperative complications in these patients were reviewed, alongside additional patients who underwent long electrode placement in the lateral rectus.

RESULTS

In 40 stimulation-induced recordings from 10 patients, the 25 mm electrodes recorded 6- to 26-fold greater amplitude EMG waveforms than the 13 mm electrodes. The 13 mm electrodes detected greater unwanted volume conduction upon facial nerve stimulation, typically exceeding the amplitude of abducens nerve stimulation. Except for one case with lateral canthus ecchymosis, no clinical or radiographic complications occurred in 36 patients (41 lateral rectus muscles) following needle placement.

CONCLUSIONS

Intramuscular recordings from long electrode in the lateral rectus offers more reliable EMG monitoring than 13 mm needles, with excellent discrimination between abducens and facial nerve stimulations, and without significant complications from needle placement.

SIGNIFICANCE

Long intramuscular electrode within the orbit for lateral rectus EMG recording is practical and reliable for abducens nerve monitoring.

Dosage effect of cisatracurium on intubation and intraoperative neuromonitoring during thyroidectomy: a randomized controlled trial

Background

Intraoperative neuromonitoring (IONM) reduces the risk of recurrent laryngeal nerve (RLN) injury during thyroid surgery. However, the use of neuromuscular blocking agents (NMBAs), which are essential to improve intubation conditions, may hinder the electromyographic response during IONM. The aim of this prospective, double-blind, randomized controlled trial was to explore the optimal dosage of cisatracurium to produce adequate muscle relaxation for tracheal intubation without significantly affecting evoked potentials of IONM during thyroidectomy.

Methods

Patients undergoing thyroidectomy with IONM in our institution, with an American Society of Anesthesiologists grade of I-II, aged 18-75 years, and with a body mass index below 32 kg/m² were enrolled and randomly assigned (by random numbers) to receive 1× (group C1) or 2× (group C2) the effective dose (ED₉₅) of cisatracurium for tracheal intubation. The patients, surgeons, and anesthesiologists in charge were blinded to group assignment. Anesthesia was induced with sufentanil, propofol, and cisatracurium (0.05 mg/kgin group C1, 0.1 mg/kg in group C2). Ease of intubation was evaluated with the intubation condition score (Cooper score) and the intubation difficulty scale (IDS). Amplitudes of evoked potentials during intermittent IONM were compared between groups. The primary outcomes were the Cooper score, the IDS score, and the evoked potentials of IONM.

Results

Fifty-three patients were randomized from October 2019 to November 2020, and 52 were analyzed (with 26 patients in each group). The Cooper score was significantly lower in group C1 [median, 8.0 (interquartile range, 7.0-8.3)] than in group C2 [9.0 (9.0-9.0), P<0.001]. The rate of difficult laryngoscopy without external laryngeal pressure was significantly higher in group C1 than in group C2 (61.5% vs. 11.5%, P<0.001). More patients in group C1 required assistance to complete tracheal intubation (16 vs. 4, P=0.001). The IDS score was significantly higher in group C1 [3.0 (0.0-4.0) vs. 1.0 (0.0-1.0), P=0.045]. There were no significant differences between groups in amplitudes of evoked potentials. No serious adverse events were observed.

Conclusions

A dose of 2× ED₉₅ of cisatracurium provided better intubation conditions and easier tracheal intubation than 1× ED₉₅, without disturbing IONM.

Trial Protocol

Chinese Clinical Trial Registry (No. ChiCTR1900022884).

IONM Troubleshooting in Spinal Procedures

A useful reference for practitioners of neuromonitoring that explains how to anticipate, avoid, and properly attend to technical problems that may arise while providing intraoperative neuromonitoring (IONM) in spinal procedures.

Spinal Cord Tumor Surgery

A spinal cord tumor is any tumor involving the spinal cord or immediate surrounding area. Tumors typically are classified as extradural, intradural extramedullary, or intramedullary intradural. Many spinal cord tumor resections attempt to balance tumor removal with preservation of neurologic function. It is important that anesthesiologists be familiar with the common perioperative risks involved in resection of spinal cord tumors as well as how to form an anesthetic plan that takes intraoperative neuromonitoring and patient comorbidities into consideration. Other risks of prolonged spinal tumor resection include postoperative visual loss, acute on chronic pain, and delayed awakening.

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.

Intraoperative neuromonitoring loss in abnormal magnetic resonance imaging signal intensity from patients with cervical compressive myelopathy

PURPOSE

Our objective of this study was to evaluate if cervical compressive myelopathy (CCM) patients with preoperative abnormal magnetic resonance imaging (MRI) might easily lead to intraoperative neuromonitoring (IONM) loss.

METHOD

A consecutive series of 152 CCM patients who underwent cervical cord decompression were enrolled in this study between December 2013 and February 2017. All patients with abnormal MRI signal intensity were divided into 2 groups (group 1: T2-WIs hyperintensity; group 2: both T2-WIs hyperintensity and T1-WIs hypointensity). Relevant IONM changes were identified as significant transcranial motor evoked potentials (MEP) loss associated with surgical decompression of cervical cord.

RESULTS

There were 121 patients in group 1, and then 6 cases showed IONM degeneration; 31 patients in group 2, and then 13 cases showed IONM degeneration (6/121 versus 13/31, p=0.000). Moreover, one case presented transient new spinal deficits after surgery, no permanent spinal deficit in group 1; 5 cases presented transient new spinal deficits, 2 cases showed permanent spinal deficit in group 2. And in group 2 the MEP amplitude before and after decompression had significant difference (134μV±30.2 versus 65μV±26.2, *p<0.05).

CONCLUSION

Our results suggest that the IONM degenerations or postoperative spinal deficits are more likely to appear on patients with abnormal T2-WIs and T1-WIs. Appropriate and timely interventions are probably useful for IONM recovery.

Opportunities and challenges of intermittent and continuous intraoperative neural monitoring in thyroid surgery

The number of thyroid operations and there radically continues to rise in the western hemisphere, bringing prevention of recurrent laryngeal nerve (RLN) palsy to the fore. Overall, the incidence of RLN palsy is fairly low but continues to prompt litigation for malpractice. In an effort to diminish transient, and more importantly permanent, RLN palsy rates, intraoperative neuromonitoring (IONM) has been advocated as a risk minimization tool. Recent meta-analyses of studies, many of which were limited by poor study design and the sole use of intermittent nerve stimulation, were unable to demonstrate superiority of IONM over mere anatomic RLN dissection. This is where continuous IONM (CIONM) comes into play: this technology enables the surgeon to (I) identify impending nerve injury as it unfolds; (II) release distressed nerves by reversing causative surgical maneuvers; and (III) verify functional nerve recovery after intraoperative loss of the electromyographic signal. Despite this superiority, CIONM is not devoid of methodological limitations, which need to be accounted for. This review summarizes the current key achievements of IONM; outlines opportunities for improvement regarding clinical implementation; and suggests areas of future research in this rapidly evolving field.

Intermittent neural monitoring of the recurrent laryngeal nerve in surgery for recurrent goiter

Reoperative thyroid surgery is still challenging even for skilled surgeons, and is associated with a higher incidence of complications, such as hypoparathyroidism and recurrent laryngeal nerve (RLN) palsy. Displacement of the RLN, scar tissue from previous neck surgery and difficulty in maintaining good hemostasis are risk factors in reoperations. The prevalence of RLN injury in reoperative thyroid surgery ranges as high as 12.5% for transient injury and up to 3.8% for permanent injury. Bilateral paresis can also occur during reoperations, and is a dangerous complication influencing the quality of life, sometimes requiring tracheostomy. RLN identification is the gold standard during thyroidectomy, and the use of intraoperative neuromonitoring (IONM) can be a valuable adjunct to visual identification. This technique can be used to identify the RLN and the external branch of the superior laryngeal nerve (EBSLN), both of which are standardized procedures. The aim of this review was to evaluate the use of intermittent neural monitoring of the RLN in surgery for recurrent goiter, and to assess the prevalence of RLN injury while using IONM reported in the current literature.