Utility of motor-evoked potentials in contemporary open thoracoabdominal aortic repair.

OBJECTIVE: Paraplegia remains one of the major complications of contemporary open thoracoabdominal aortic aneurysm (TAAA) repair. Intraoperative motor-evoked potentials (MEPs) act as a surrogate measure for spinal cord homeostasis. The purpose of this study was to evaluate the results of intraoperative neuromonitoring in contemporary TAAA repair and its association with postoperative spinal cord ischemia (SCI). METHODS: Patients who underwent open type 2 or 3 TAAA or completion aortic repair using intraoperative neuromonitoring were identified between May 2006 and November 2023. Patient demographics, comorbidities, indication for the procedure, procedural details, and outcomes were recorded. The groups were divided based on type of repair, and univariate statistics were then used to evaluate the association of these metrics vs the type of repair. RESULTS: Seventy-nine patients underwent open type 2 (N = 41) and 3 (N = 23) TAAA and completion aortic (N = 15; open in 14 and endovascular in 1) repairs by a single surgeon. The cohort was predominantly male (N = 48, 60.8%) with a mean age of 52.5 ± 16.2 years. There was a high incidence of hypertension (N = 53, 67.1%), smoking history (N = 42, 53.1%), and connective tissue disorders (N = 37, 46.8%). Operative indications included dissection-related (N = 50, 63.3%) and degenerative (N = 26, 32.9%) TAAA and dissection-related malperfusion (N = 3, 3.8%). Left heart bypass was often (N = 73, 92.4%) used for distal aortic perfusion, and cerebrospinal fluid drainage (N = 77, 97.5%) was a common adjunct. MEPs were classified as no change (N = 43, 54.4%), reversible change (N = 26, 32.9%), irreversible change (N = 4, 5.1%), and unreliable (N = 6, 7.6%). MEP changes were predominantly bilateral (N = 70, 88.6%) and occurred most often during repair of the abdominal aortic segment (N = 13, 16.5%). The median number of replaced vertebral levels was associated with MEP changes (P = .013). SCI was only observed in repairs greater than 6 replaced vertebral levels with an overall frequency of 17.7%. It was most prevalent in completion aortic repairs (26.7%). Immediate and delayed SCI occurred in 10.1% and 7.6% of patients, respectively; it was most commonly (71.8%) reversible. Permanent paraplegia occurred in four patients (5.1%), with equal immediate and delayed onsets. MEPs demonstrated poor sensitivity (53.9%) and specificity (62.3%) for SCI; however, there was a high negative predictive value (86.4%) in this population. In-hospital mortality occurred in five (6.3%) patients. CONCLUSIONS: No changes in intraoperative MEPs are highly predictive of spinal cord homeostasis. The number of replaced vertebral levels and previous aortic repair should guide intraoperative neuroprotective measures including intercostal reimplantation and should take precedence over intraoperative monitoring, especially when MEP changes occur.

The diagnostic accuracy of neuromonitoring for detecting postoperative bowel and bladder dysfunction in spinal oncology surgery: a case series.

PURPOSE: Postoperative bowel and bladder dysfunction (BBD) poses a significant risk following surgery of the sacral spinal segments and sacral nerve roots, particularly in neuro-oncology cases. The need for more reliable neuromonitoring techniques to enhance the safety of spine surgery is evident. METHODS: We conducted a case series comprising 60 procedures involving 56 patients, spanning from September 2022 to January 2024. We assessed the diagnostic accuracy of sacral reflexes (bulbocavernosus and external urethral sphincter reflexes) and compared them with transcranial motor evoked potentials (TCMEP) incorporating anal sphincter (AS) and external urethral sphincter (EUS) recordings, as well as spontaneous electromyography (s-EMG) with AS and EUS recordings. RESULTS: Sacral reflexes demonstrated a specificity of 100% in predicting postoperative BBD, with a sensitivity of 73.33%. While sensitivity slightly decreased to 64.71% at the 1-month follow-up, it remained consistently high overall. TCMEP with AS/EUS recordings did not identify any instances of postoperative BBD, whereas s-EMG with AS/EUS recordings showed a sensitivity of 14.29% and a specificity of 97.14%. CONCLUSION: Sacral reflex monitoring emerges as a robust adjunct to routine neuromonitoring, offering surgeons valuable predictive insights to potentially mitigate the occurrence of postoperative BBD.

Usefulness of Motor Evoked Potential Measurement and Analysis of Risk Factors for Spinal Cord Ischaemia from 300 Cases of Thoracic Endovascular Aortic Repair.

OBJECTIVE: This study investigated the usefulness of motor evoked potentials (MEPs) for intra-operative monitoring to detect the risk of spinal cord ischaemia (SCI) during thoracic endovascular aortic repair (TEVAR). Risk factors for SCI in TEVAR were also analysed. METHODS: Among 330 TEVARs performed from February 2009 to October 2018, 300 patients underwent intra-operative MEP monitoring. SCI risk groups were extracted based on MEP amplitude changes using a cutoff value of 50%. When the amplitude decreased to < 50% of the pre-operative value, intra-operative mean arterial pressure (MAP) was increased by about 20 mmHg using noradrenaline, whereas MAP was usually controlled to about 80 mmHg during surgery. Other efforts were also made to increase MEP amplitude by increasing cardiac output, correcting anaemia, and finishing the surgery promptly. Based on MEP amplitude data, SCI risk groups were extracted and risk factors for SCI in TEVAR were analysed. RESULTS: A total of 283 non-SCI risk patients and 17 SCI risk patients by MEP monitoring were extracted; only 1.0% developed immediate paraplegia and none developed delayed paraplegia. Bivariable analysis showed significant differences in chronic kidney disease, haemodialysis, artery of Adamkiewicz closure, and stent graft (SG) covered length ≥ 8 vertebral bodies. Logistic regression analysis showed hyperlipidaemia (odds ratio [OR] 3.55, 95% confidence interval [CI] 1.08 - 11.67; p = .037), SG covered length ≥ 8 vertebral bodies (OR 1.35, 95% CI 1.02 - 1.78; p = .034), and haemodialysis (OR 27.78, 95% CI 6.02 - 128.22; p < .001) were the most influential risk factors for SCI in TEVAR. CONCLUSION: MEPs might be a useful monitoring tool to predict SCI in TEVAR. In addition, hyperlipidaemia, SG covered length ≥ 8 vertebral bodies, and haemodialysis represent key risk factors for SCI during TEVAR.

The Association of Physiological and Pharmacological Anesthetic Parameters With Motor-Evoked Potentials: A Multivariable Longitudinal Mixed Model Analysis.

BACKGROUND: During spinal surgery, the motor tracts can be monitored using muscle-recorded transcranial electrical stimulation motor-evoked potentials (mTc-MEPs). We aimed to investigate the association of anesthetic and physiological parameters with mTc-MEPs. METHODS: Intraoperative mTc-MEP amplitudes, mTc-MEP area under the curves (AUC), and anesthetic and physiological measurements were collected retrospectively from the records of 108 consecutive patients undergoing elective spinal surgery. Pharmacological parameters of interest included propofol and opioid concentration, ketamine and noradrenaline infusion rates. Physiological parameters recorded included mean arterial pressure (MAP), bispectral index (BIS), heart rate, hemoglobin O 2 saturation, temperature, and Et co2 . A forward selection procedure was performed using multivariable mixed model analysis. RESULTS: Data from 75 (69.4%) patients were included. MAP and BIS were significantly associated with mTc-MEP amplitude ( P < .001). mTc-MEP amplitudes increased by 6.6% (95% confidence interval [CI], 2.7%-10.4%) per 10 mm Hg increase in MAP and by 2.79% (CI, 2.26%-3.32%) for every unit increase in BIS. MAP ( P < .001), BIS ( P < .001), heart rate ( P = .01), and temperature ( P = .02) were significantly associated with mTc-MEP AUC. The AUC increased by 7.5% (CI, 3.3%-11.7%) per 10 mm Hg increase of MAP, by 2.98% (CI, 2.41%-3.54%) per unit increase in BIS, and by 0.68% (CI, 0.13%-1.23%) per beat per minute increase in heart rate. mTc-MEP AUC decreased by 21.4% (CI, -38.11% to -3.98%) per degree increase in temperature. CONCLUSIONS: MAP, BIS, heart rate, and temperature were significantly associated with mTc-MEP amplitude and/or AUC. Maintenance of BIS and MAP at the high normal values may attenuate anesthetic effects on mTc-MEPs.

Intraoperative mapping and preservation of executive functions in awake craniotomy: a systematic review.

Awake craniotomy (AC) allows intraoperative brain mapping (ioBM) for maximum lesion resection while monitoring and preserving neurological function. Conventionally, language, visuospatial assessment, and motor functions are mapped, while the assessment of executive functions (EF) is uncommon. Impaired EF may lead to occupational, personal, and social limitations, thus, a compromised quality of life. A comprehensive literature search was conducted through Scopus, Medline, and Cochrane Library using a pre-defined search strategy. Articles were selected after duplicate removal, initial screening, and full-text assessment. The demographic details, ioBM techniques, intraoperative tasks, and their assessments, the extent of resection (EOR), post-op EF and neurocognitive status, and feasibility and potential adverse effects of the procedure were reviewed. The correlations of tumor locations with intraoperative EF deficits were also assessed. A total of 13 studies with intraoperative EF assessment of 351 patients were reviewed. Awake-asleep-awake protocol was most commonly used. Most studies performed ioBM using bipolar stimulation, with a frequency of 60 Hz, pulse durations ranging 1-2 ms, and intensity ranging 2-6 mA. Cognitive function was monitored with the Stroop task, spatial-2-back test, line-bisection test, trail-making-task, and digit-span tests. All studies reported similar or better EOR in patients with ioBM for EF. When comparing the neuropsychological outcomes of patients with ioBM of EF to those without it, all studies reported significantly better EF preservation in ioBM groups. Most authors reported EF mapping as a feasible tool to obtain satisfactory outcomes. Adverse effects included intraoperative seizures which were easily controlled. AC with ioBM of EF is a safe, effective, and feasible technique that allows satisfactory EOR and improved neurocognitive outcomes with minimal adverse effects.

Intraoperative pelvic neuromonitoring based on bioimpedance signals: a new method analyzed on 30 patients.

PURPOSE: Increasing importance has been attributed in recent years to the preservation of the pelvic autonomic nerves during rectal resection to achieve better functional results. In addition to improved surgical techniques, intraoperative neuromonitoring may be useful. METHODS: This single-arm prospective study included 30 patients who underwent rectal resection performed with intraoperative neuromonitoring by recording the change in the tissue impedance of the urinary bladder and rectum after stimulation of the pelvic autonomic nerves. The International Prostate Symptom Score, the post-void residual urine volume and the Low Anterior Resection Syndrome Score (LARS score) were assessed during the 12-month follow-up period. RESULTS: A stimulation-induced change in tissue impedance was observed in 28/30 patients (93.3%). In the presence of risk factors such as low anastomosis, neoadjuvant radiotherapy and a deviation stoma, an average increase of the LARS score by 9 points was observed 12 months after surgery (p = 0,04). The function of the urinary bladder remained unaffected in the first week (p = 0,7) as well as 12 months after the procedure (p = 0,93). CONCLUSION: The clinical feasibility of the new method for pelvic intraoperative neuromonitoring could be verified. The benefits of intraoperative pelvic neuromonitoring were particularly evident in difficult intraoperative situations with challenging visualization of the pelvic nerves.

Mapping of Capsular Side Effects by using Intraoperative Motor-Evoked Potentials during Asleep Deep Brain Stimulation Surgery of the Subthalamic Nucleus for Parkinson's Disease.

INTRODUCTION: The aim of this study was to present a novel technique for subthalamic nucleus (STN) deep brain stimulation (DBS) implantation under general anesthesia by using intraoperative motor-evoked potentials (MEPs) through direct lead stimulation and determining their correlation to the thresholds of postoperative stimulation-induced side effects. METHODS: This study included 22 consecutive patients with advanced Parkinson's disease who underwent surgery in our institution between January 2021 and September 2023. All patients underwent bilateral implantation in the STN (44 leads) under general anesthesia without microelectrode recordings (MERs) by using MEPs with electrostimulation directly through the DBS lead. No cortical stimulation was performed during this process. Intraoperative fluoroscopic guidance and immediate postoperative computed tomography were used to verify the electrode's position. The lowest MEP thresholds were recorded and were correlated to the postoperative stimulation-induced side-effect threshold. The predictive values of the MEPs were analyzed. Five DBS leads were repositioned intraoperatively due to the MEP results. RESULTS: A moderately strong positive correlation was found between the MEP threshold and the capsular side-effect threshold (RS = 0.425, 95% CI, 0.17-0.67, p = 0.004). The highest sensitivity and specificity for predicting a side-effect threshold of 5 mA were found to be at 2.4 mA MEP threshold (sensitivity 97%, specificity 87.5%, positive predictive value 97%, and negative predictive value 87.5%). We also found high sensitivity and specificity (100%) at 1.15 mA MEP threshold and 3 mA side-effect threshold. Out of the total 44 leads, 5 (11.3%) leads were repositioned intraoperatively due to MEP thresholds lower than 1 mA (4 leads) or higher than 5 mA (1 lead). The mean accuracy on postoperative CT was 1.05 mm, and there were no postoperative side-effects under 2.8 mA. CONCLUSION: Intraoperative MEPs with electrostimulation directly through the contacts of the DBS lead correlate with the stimulation-induced capsular side effects. The lead reposition based on intraoperative MEP may enlarge the therapeutic window of DBS stimulation.

Application of neurophysiological monitoring during tethered cord release in children.

OBJECTIVE: The objective of this study was to explore the effect of intraoperative neurophysiological monitoring (IONM) on tethered spinal cord release in children. METHODS: The clinical data of 454 children with tethered cord syndrome who underwent surgery for tethered cord release were retrospectively analyzed. The children were divided into two groups: the non-IONM group and the IONM group. SPSS 26.0 software was used for statistical analysis. The evaluation indices included the effective rate and incidence of new neurological dysfunction. RESULTS: The short-term results showed that the effective rate of the non-IONM group was 14.8%, while that of the IONM group was 15.2%. Additionally, the incidence of new neurological dysfunction was 7.8% in the non-IONM group and 5.6% in the IONM group. However, there was no significant difference between the two groups (P > 0.05). The medium- to long-term follow-up had significant difference (P < 0.05), the response rate was 32.1% in the IONM group and 23.7% in the non-IONM group, and deterioration rates regarding neurological dysfunction were 3.3% in the IONM group and 8.5% in the non-IONM group. CONCLUSION: This study revealed that the use of IONM does not significantly improve the short-term treatment effect of patients undergoing surgery for tethered cord release or reduce the short-term incidence of postoperative new neurological dysfunction. However, the medium- to long-term prognoses of patients in the IONM group were better than those of patients in the non-IONM group.

Pediatric craniopharyngioma with significantly increased intraoperative visual evoked potential amplitude and postoperative visual acuity improvement: a case report.

Visual evoked potential (VEP) is an established modality that allows safe brain tumor resection and preservation of optical function. We herein present a case of a pediatric craniopharyngioma with significant improvement in the VEP amplitude detected during endoscopic transsphenoidal surgery (ETS) and obvious postoperative improvement in visual acuity. A 13-year-old boy presented with visual acuity disturbance in his right eye and was followed up for 5 months by an ophthalmologist. His visual acuity rapidly worsened, and a suprasellar lesion with calcification was found on brain computed tomography. The patient underwent tumor resection during ETS with intraoperative transcranial VEP monitoring. Gross total tumor resection was achieved without injury to the perforators, including the superior hypophyseal arteries. The VEP amplitude was unstable, and significant waves were not detectable before tumor resection; however, a positive wave was detected after removing most of the tumor and exposing the bilateral optic nerves and optic chiasm. Subsequently, negative and positive VEP waves were continuously detected. Visual acuity improved remarkably on postoperative day 10. This case demonstrated both a significant increase in the intraoperative VEP amplitude and rapid postoperative improvement in visual acuity. We surmised that the preoperative rapid worsening of visual dysfunction, intraoperative increase in the VEP amplitude, and significant postoperative improvement in visual acuity were associated with the compression of the optic nerves by the internal carotid artery, anterior cerebral artery, and tumor.

Intraoperative microelectrode recording during asleep deep brain stimulation of subthalamic nucleus for Parkinson Disease. A case series with systematic review of the literature.

The use of microelectrode recording (MER) during deep brain stimulation (DBS) for Parkinson Disease is controversial. Furthermore, in asleep DBS anesthesia can impair the ability to record single-cell electric activity.The purpose of this study was to describe our surgical and anesthesiologic protocol for MER assessment during asleep subthalamic nucleus (STN) DBS and to put our findings in the context of a systematic review of the literature. Sixty-three STN electrodes were implanted in 32 patients under general anesthesia. A frameless technique using O-Arm scanning was adopted in all cases. Total intravenous anesthesia, monitored with bispectral index, was administered using a target controlled infusion of both propofol and remifentanil. A systematic review of the literature with metanalysis on MER in asleep vs awake STN DBS for Parkinson Disease was performed. In our series, MER could be reliably recorded in all cases, impacting profoundly on electrode positioning: the final position was located within 2 mm from the planned target only in 42.9% cases. Depth modification > 2 mm was necessary in 21 cases (33.3%), while in 15 cases (23.8%) a different track was used. At 1-year follow-up we observed a significant reduction in LEDD, UPDRS Part III score off-medications, and UPDRS Part III score on medications, as compared to baseline. The systematic review of the literature yielded 23 papers; adding the cases here reported, overall 1258 asleep DBS cases using MER are described. This technique was safe and effective: metanalysis showed similar, if not better, outcome of asleep vs awake patients operated using MER. MER are a useful and reliable tool during asleep STN DBS, leading to a fine tuning of electrode position in the majority of cases. Collaboration between neurosurgeon, neurophysiologist and neuroanesthesiologist is crucial, since slight modifications of sedation level can impact profoundly on MER reliability.

Intraoperative neuromonitoring in Chiari I malformation surgery: a systematic review and meta-analysis.

Chiari Malformation Type I (CMI) is a prevalent neurosurgical condition characterized by the descent of cerebellar tonsils below the foramen magnum. Surgery, aimed at reducing symptomatology and syrinx size, presents risks, making intraoperative neuromonitoring (IONM) a potentially vital tool. Despite its widespread use in cervical spine surgery, the utility of IONM in CMI surgery remains controversial, with concerns over increased operative time, cost, restricted anesthetic techniques and tongue lacerations. This systematic review and meta-analysis followed the Cochrane Group standards and PRISMA framework. It encompassed an extensive search through PubMed, Embase, and Web of Science up to December 2023, focusing on clinical and surgical outcomes of IONM in CMI surgery. Primary outcomes included the use of various IONM techniques, complication rates, clinical improvement, reoperation, and mortality. The review, registered at PROSPERO (CRD42024498996), included both prospective and retrospective studies, with rigorous selection and data extraction processes. Statistical analysis was conducted using R software. The review included 16 studies, comprising 1358 patients. It revealed that IONM techniques predominantly involved somatosensory evoked potentials (SSEPs), followed by motor evoked potentials (MEPs) and Brainstem auditory evoked potentials (BAEPs). The estimated risk of complications with IONM was 6% (95% CI: 2-11%; I2 = 89%), lower than previously reported rates without IONM. Notably, the clinical improvement rate post-surgery was high at 99% (95% CI: 98-100%; I2 = 56%). The analysis also showed lower reoperation rates in surgeries with IONM compared to those without. Interestingly, no mortality was observed in the included studies. This systematic review and meta-analysis indicate that intraoperative neuromonitoring in Chiari I malformation surgery is associated with favorable clinical outcomes, including lower complication and reoperation rates, and high rates of clinical improvement.

Role of Intraoperative Neuromonitoring to Predict Postoperative Delirium in Cardiovascular Surgery.

OBJECTIVE: Postoperative delirium (POD) can occur in up to 50% of older patients undergoing cardiovascular surgery, resulting in hospitalization and significant morbidity and mortality. This study aimed to determine whether intraoperative neurophysiologic monitoring (IONM) modalities can be used to predict delirium in patients undergoing cardiovascular surgery. DESIGN: Adult patients undergoing cardiovascular surgery with IONM between 2019 and 2021 were reviewed retrospectively. Delirium was assessed multiple times using the Intensive Care Delirium Screening Checklist (ICDSC). Patients with an ICDSC score ≥4 were considered to have POD. Significant IONM changes were evaluated based on a visual review of electroencephalography (EEG) and somatosensory evoked potentials data and documentation of significant changes during surgery. SETTING: University of Pittsburgh Medical Center hospitals. PARTICIPANTS: Patients 18 years old and older undergoing cardiovascular surgery with IONM monitoring. MEASUREMENTS AND MAIN RESULTS: Of the 578 patients undergoing cardiovascular surgery with IONM, 126 had POD (21.8%). Significant IONM changes were noted in 134 patients, of whom 49 patients had delirium (36.6%). In contrast, 444 patients had no IONM changes during surgery, of whom 77 (17.3%) patients had POD. Upon multivariate analysis, IONM changes were associated with POD (odds ratio 2.12; 95% CI 1.31-3.44; p < 0.001). Additionally, baseline EEG abnormalities were associated with POD (p = 0.002). CONCLUSION: Significant IONM changes are associated with an increased risk of POD in patients undergoing cardiovascular surgery. These findings offer a basis for future research and analysis of EEG and somatosensory evoked potential monitoring to predict, detect, and prevent POD.

A critical event frequent lead to reversible spinal cord injury during vertebral column resection surgery.

OBJECTIVE: To report a "critical phase" (between osteotomy completion and correction beginning) that will frequently lead to the reversible intraoperative neurophysiological monitoring (IOM) change during posterior vertebral column resection (PVCR) surgery. METHODS: The study sample consisted of 120 patients with severe spine deformity who underwent PVCR and deformity correction surgeries. Those patients were recruited consecutively from 2010 to 2018 January in our spine center. The detailed IOM data (the amplitude of MEP & SEP) and its corresponding surgical points were collected prospectively. Early and long-term postoperative neurologic outcomes were assessed for the following functions: motor, sensory, and pain at immediate postoperative and 1-year post-operation in this cases series. RESULTS: A total of 105 (105/120) patients presented varying degrees of IOM reduction in the critical phase; the mean IOM amplitude retention vs rescue rate was 27% ± 11.2 versus 58% ± 16.9, P < 0.01 (MEP) & 34% ± 8.3 versus 66% ± 12.4 P < 0.01 (SEP). Patients with postoperative spinal deficits often had a significantly longer IOM-alerting duration than the patients without (p < 0.01, Mann-Whitney U-test), and IOM-alerting duration greater than 39.5 min was identified as an independent predictor of the risk of postoperative spinal deficits. CONCLUSIONS: The reversible IOM events probably often appear in the critical phase during PVCR surgery. The new postoperative spinal deficits are possible for patients without satisfied IOM recovery or alerting duration greater than 39.5 min. Timely and suitable surgical interventions are useful for rescuing the IOM alerts.

The effects of dexmedetomidine on intraoperative neurophysiologic monitoring modalities during corrective scoliosis surgery in pediatric patients: A systematic review.

BACKGROUND: During scoliosis surgery, motor evoked potentials (MEP), and somatosensory evoked potentials (SSEP) have been reported to be affected by the use of higher doses of anesthetic agents. Dexmedetomidine, a sympatholytic agent, an alpha-2 receptor agonist, has been used as an adjunctive agent to lower anesthetic dose. However, there is conflicting evidence regarding the effects of dexmedetomidine on the intraoperative neurophysiological monitoring of MEP and SSEP during surgery, particularly among pediatric patients. OBJECTIVES: This systematic review aimed to determine whether, during spinal fusion surgery in pediatric patients with scoliosis, dexmedetomidine alters MEP amplitude or SSEP latency and amplitude and, if so, whether different doses of dexmedetomidine display different effects (PROSPERO registration number CRD42022300562). METHODS: We searched PubMed, Scopus, and Cochrane Library on January 1, 2022 and included randomized controlled trials, observational cohort and case-control studies and case series investigating dexmedetomidine in the population of interest and comparing against a standardized anesthesia regimen without dexmedetomidine or comparing multiple doses of dexmedetomidine. Animal and in vitro studies and conference abstracts were excluded. RESULTS: We found substantial heterogeneity in the risk of bias (per Cochrane-preferred tools) of the included articles (n = 5); results are summarized without meta-analysis. Articles with the lowest risk of bias indicated that dexmedetomidine was associated with MEP loss and that higher doses of dexmedetomidine increased risk. In contrast, articles reporting no association between dexmedetomidine and MEP loss suffered from higher risk of bias, including suspected or confirmed problems with confounding, outcome measurement, participant selection, results reporting, and lack of statistical transparency and power. CONCLUSION: Given the limitations of the studies available in the literature, it would be advisable to conduct rigorous randomized controlled trials with larger sample sizes to assess the effects of dexmedetomidine use of in scoliosis surgery in pediatric patients.

An update on tests used for intraoperative monitoring of cognition during awake craniotomy.

PURPOSE: Mapping higher-order cognitive functions during awake brain surgery is important for cognitive preservation which is related to postoperative quality of life. A systematic review from 2018 about neuropsychological tests used during awake craniotomy made clear that until 2017 language was most often monitored and that the other cognitive domains were underexposed (Ruis, J Clin Exp Neuropsychol 40(10):1081-1104, 218). The field of awake craniotomy and cognitive monitoring is however developing rapidly. The aim of the current review is therefore, to investigate whether there is a change in the field towards incorporation of new tests and more complete mapping of (higher-order) cognitive functions. METHODS: We replicated the systematic search of the study from 2018 in PubMed and Embase from February 2017 to November 2023, yielding 5130 potentially relevant articles. We used the artificial machine learning tool ASReview for screening and included 272 papers that gave a detailed description of the neuropsychological tests used during awake craniotomy. RESULTS: Comparable to the previous study of 2018, the majority of studies (90.4%) reported tests for assessing language functions (Ruis, J Clin Exp Neuropsychol 40(10):1081-1104, 218). Nevertheless, an increasing number of studies now also describe tests for monitoring visuospatial functions, social cognition, and executive functions. CONCLUSIONS: Language remains the most extensively tested cognitive domain. However, a broader range of tests are now implemented during awake craniotomy and there are (new developed) tests which received more attention. The rapid development in the field is reflected in the included studies in this review. Nevertheless, for some cognitive domains (e.g., executive functions and memory), there is still a need for developing tests that can be used during awake surgery.

Dorsal root entry zone lesioning for brachial plexus avulsion - technical evolution and long-term follow-up.

BACKGROUND: Brachial plexus avulsion (BPA) injuries can cause severe deafferentation pain. This has been successfully treated with dorsal root entry zone (DREZ) lesioning. Distortions in anatomy following a BPA injury can make identifying neural structures challenging. We describe a modification to the operative technique that improves the surgical view and the advanced intraoperative neuromonitoring (IONM) employed to identify DREZ. We have analysed the long-term outcomes for pain, quality of life, and complications in patients undergoing DREZ lesioning. METHODS: This is a single-centre retrospective case series including patients who underwent DREZ lesioning with IONM for brachial plexus avulsion between 2012 and 2022. Analysed data included pre- and postoperative pain (VAS), quality of life score for chronic pain, and complications. The evolution of the surgical approach is discussed. RESULTS: 44 consecutive patients underwent a DREZ lesioning procedure with intraoperative monitoring and mapping. In these patients the mean VAS score improved from 8.9 (7-10) to 1.87 (0-6) (p < 0.0001) at the time of discharge. 31 patients were followed-up for more than 12 months with a mean duration of follow-up of 41 months and their results were as follows: the mean VAS improved from 9.0 (7-10) to 4.1 (0-9) (p < 0.0001) at the last follow-up and the mean QOL values improved from 3.7 (2-6) to 7.4 (4-10) (p < 0.0001). The long-term outcomes were 'good' in 39%, 'fair' in 29% and 'poor' in 32% of patients. 55% of the patients were able to stop or reduce pain medications. CONCLUSIONS: Modifications of surgical technique provide better exposure of DREZ, and IONM aids in identifying DREZ in the presence of severe intra-dural changes. Long-term outcomes of DREZ lesioning indicate not only a reduction in pain but also a significant improvement in quality of life.

Intraoperative Neuromonitoring for Spines at Risk During Nonspine Surgery: A 9-Year Review.

BACKGROUND: Patients with certain spinal anomalies are at risk for rare but devastating spinal cord injuries under anesthesia. We created a Spine at Risk (SAR) program to evaluate and recommend precautions for such patients, including intraoperative neuromonitoring (IONM) use for the highest-risk patients. We aimed to review all monitored nonspine procedures to determine rate of potential spinal cord injuries avoided in those who would otherwise have been unmonitored. METHODS: We performed a retrospective review of our institutional SAR program from 2011 to 2019 to analyze the number of nonspine anesthetized procedures that were done under IONM, the characteristics of those that had an IONM alert; and the clinical outcomes. RESULTS: Of the 3,453 patients flagged for SAR review, 1121 (33%) received a precaution recommendation, and 359 (10% of all flagged) were given IONM recommendations. Of those, 57 patients (16% of recommendations, 2% of all flagged) had a total of 102 nonspine anesthetized procedures done under IONM. Seven patients had a total of 10 cases with IONM alerts. Two cases were aborted when improved signals could not be obtained after working through a checklist; one of these patients woke with transient neurological deficits. Signals improved to baseline in 7 cases by working through a signal loss checklist. One case was aborted preoperatively when monitorable baseline signals could not be obtained. CONCLUSIONS: In the highest-risk spinal anomaly patients, we monitored an average of 11.7 nonspine cases per year, with a 10% rate of IONM alerts, and no permanent neurological deficits. Although the majority of patients remain safe during procedures, in the most critical patients IONM allowed the team to identify and react to alerts that may have otherwise led to permanent neurological injury. This is the largest series of spinal cord-monitored nonspine pediatric cases. It is important for pediatric orthopedic surgeons to evaluate at-risk patients and recommend IONM where appropriate, to protect both patients and our procedural colleagues. LEVEL OF EVIDENCE: Case series, level IV.

Optimizing donor fascicle selection in Oberlin's procedure: A retrospective review of anatomical variability using intraoperative neuromonitoring.

BACKGROUND: Transfer of the fascicle carrying the flexor carpi ulnaris (FCU) branch of the ulnar nerve (UN) to the biceps/brachialis muscle branch of the musculocutaneous nerve (Oberlin's procedure), is a mainstay technique for elbow flexion restoration in patients with upper brachial plexus injury. Despite its widespread use, there are few studies regarding the anatomic location of the donor fascicle for Oberlin's procedure. Our report aims to analyze the anatomical variability of this fascicle within the UN, while obtaining quantifiable, objective data with intraoperative neuromonitoring (IONM) for donor fascicle selection. METHODS: We performed a retrospective review of patients at our institution who underwent an Oberlin's procedure from September 2019 to July 2023. We used IONM for donor fascicle selection (greatest FCU muscle and least intrinsic hand muscle activation). We prospectively obtained demographic and electrophysiological data, as well as anatomical location of donor fascicles and post-surgical morbidities. Surgeon's perception of FCU/intrinsic muscle contraction was compared to objective muscle amplitude during IONM. RESULTS: Eight patients were included, with a mean age of 30.5 years and an injury-to-surgery interval of 4 months. Donor fascicle was located anterior in two cases, posterior in two, radial in two and ulnar in two patients. Correlation between surgeon's perception and IONM findings were consistent in six (75%) cases. No long term motor or sensory deficits were registered. CONCLUSIONS: Fascicle anatomy within the UN at the proximal arm is highly variable. The use of IONM can aid in optimizing donor fascicle selection for Oberlin's procedure.

Intraoperative somatosensory evoked potential (SEP) monitoring: an updated position statement by the American Society of Neurophysiological Monitoring.

Somatosensory evoked potentials (SEPs) are used to assess the functional status of somatosensory pathways during surgical procedures and can help protect patients' neurological integrity intraoperatively. This is a position statement on intraoperative SEP monitoring from the American Society of Neurophysiological Monitoring (ASNM) and updates prior ASNM position statements on SEPs from the years 2005 and 2010. This position statement is endorsed by ASNM and serves as an educational service to the neurophysiological community on the recommended use of SEPs as a neurophysiological monitoring tool. It presents the rationale for SEP utilization and its clinical applications. It also covers the relevant anatomy, technical methodology for setup and signal acquisition, signal interpretation, anesthesia and physiological considerations, and documentation and credentialing requirements to optimize SEP monitoring to aid in protecting the nervous system during surgery.

Changes in motor evoked potentials after erector spinae block in scoliosis surgery-when to take pre-incision baseline recordings?

Multimodal intraoperative neurophysiological monitoring (IONM) is highly valuable in scoliosis surgeries for monitoring spinal cord function, particularly during instrumentation. Accurate timing of baseline recordings of TcMEP and SSEP is crucial, as any changes observed during surgery and instrumentation are compared to these baseline recordings. However, the impact of ultrasound-guided erector spinae block (USG-ESPB) on SSEP and TcMEP is not well-studied in scoliosis surgery. In this report, we present two cases of scoliosis surgery where bilateral two-level USG-ESPB using different concentrations of ropivacaine (0.375% and 0.2%) resulted in a transient and significant deterioration of TcMEP, occurring 3 minutes after the block and lasting for 20 minutes. Remarkably, SSEPs remained unchanged during this period. These findings suggest that USG-ESPB may produce TcMEP changes, highlighting the importance of carefully considering the timing of baseline TcMEP acquisition in scoliosis surgery.