Intraoperative Motor Evoked Potential Research Articles

Intraoperative DBS targeting of the globus pallidus internus by using motor evoked potentials

ObjectivesTarget localization for deep brain stimulation (DBS) is a crucial step that influences the clinical benefit of the DBS procedure together with the reduction of side effects. In this work, we address the feasibility of DBS target localization in the globus pallidus internus (GPi) aided by intraoperative motor-evoked potentials with emphasis on the reduction of capsular side effects. Material and methodsMicro-macroelectrode recordings were performed intraoperatively on 20 patients that underwent DBS treatment of the GPi (GPi-DBS). Motor evoked potentials (MEP) were elicited intraoperatively by micro- and macroelectrode stimulation during stereotactic DBS surgery. We studied the relationship between MEP thresholds and the internal capsule (IC) proximity. ResultsWe found a significant correlation between intraoperative MEP thresholds and IC proximity for microelectrode stimulation. ConclusionsWe provide further evidence of the role of MEPs for DBS target localization in the GPi, which extends and confirms the usefulness of MEPs as previously reported by DBS target localization studies dealing with the subthalamic and thalamic nuclei. Our approach is advantageous in that it provides criteria to determine the DBS target without the need to rely on a patient's response while avoiding capsular effects.

Effectiveness of the Bilateral and Bilevel Erector Spinae Plane Block (ESPB) in Pediatric Idiopathic Scoliosis Surgery: A Randomized, Double-Blinded, Controlled Trial.

This study aimed to compare the effect of the ultrasound-guided bilateral and bilevel erector spinae plane block (ESPB) on pain scores, opioid requirement, intraoperative motor-evoked potentials (MEPs), and stress response to surgery expressed by the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) versus standard analgesia methods following idiopathic scoliosis surgery. This was a prospective, double-blinded, randomized controlled trial. Sixty patients aged 10 to 18 years and physical status ASA 1 or 2 were randomized into 2 equal groups, each receiving an ESPB or sham block. The primary outcome was the pain scores (Numerical Rating Scale, NRS) within 48 hours after spinal correction and fusion surgery for idiopathic thoracic scoliosis. The secondary outcomes were total opioid consumption, NLR, and PLR levels at 12 and 24 hours postoperatively and intraoperative MEPs. ESPB patients presented lower NRS scores, signifying less pain, at all time points (30, 60, 90, 120 min; and 6, 12, 24, and 48 h after surgery), all P<0.0001. The total opioid consumption, the incidence of nausea or vomiting, and the need for remifentanil and propofol during surgery were significantly lower in the ESPB group. The surgery-induced stress response expressed by NLR and PLR was considerably lower in the ESPB group. ESPB did not affect the intraoperative MEP's amplitude. ESPB is effective for postoperative analgesia, can reduce opioid consumption in patients undergoing scoliosis surgery, and reduces the stress response to surgery. ESPB does not interfere with neuromonitoring. Level I.

Utility of Motor Evoked Potentials in Contemporary Open Thoracoabdominal Aortic Repair

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). 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. 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± 16.2years. 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. 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.

Maximal Resection of Gliomas Adjacent to the Corticospinal Tract Using 3-T Intraoperative Magnetic Resonance Imaging

BackgroundGliomas adjacent to the corticospinal tract (CST) should be carefully resected to preserve motor function while achieving maximal surgical resection. Modern high-field intraoperative magnetic resonance imaging (iMRI) enables precise visualization of the residual tumor and intraoperative tractography. We prospectively evaluated the extent of resection and distance between the tumor resection cavity and CST using 3-T iMRI combined with motor evoked potentials (MEP) in glioma surgery. MethodParticipants comprised patients who underwent surgery for solitary supratentorial glioma located within 10 mm of the CST. All cases underwent surgery using neuronavigation with overlaid CST under MEP monitoring. The correlation between distance from CST and transcortical MEP amplitude was calculated using Spearman rank correlation. ResultsAmong the 63 patients who underwent surgery, 27 patients were enrolled in the study. Gross total resections were achieved in 26 of the 27 cases. Volumetric analysis showed the extent of resection was 98.6%. Motor function was stable or improved in 24 patients (Stable/Improved group) and deteriorated in 3 patients (Deteriorated group). All patients in the Deteriorated group showed motor deficit before surgery. Mean intraoperative minimal distance was significantly longer in the Stable/Improved group (7.3 mm) than in the Deteriorated group (1.1 mm; p < 0.05). MEP amplitude correlated with minimal distance between the resection cavity and CST (R=0.64). ConclusionsResection of gliomas adjacent to CST with a navigation system using 3-T iMRI could result in an ultimate EOR >98%. The combination of intraoperative tractography and MEP contributes to maximal removal of motor-eloquent gliomas.

Facilitation of motor evoked potentials after tetanic peripheral nerve stimulation

ObjectiveTetanic stimulation of a peripheral nerve prior to transcranial electrical stimulation (TES) may enhance motor evoked potential (MEP) amplitudes. The purpose of this study was to investigate the post-tetanic MEP (p-MEP) technique in improving MEP amplitudes. MethodsConventional TES MEPs (c-MEP) and p-MEPs with left upper limb stimulation (p-MEPUL) or left lower limb stimulation (p-MEPLL) were performed in 26 patients. Bilateral hand and foot MEP amplitudes obtained with each protocol were compared. Subgroup comparisons were performed for myelopathy and peripheral neuropathy patients. Within-subject amplitude differences between c-MEP and each p-MEP technique were compared using a Wilcoxon test. ResultsThe mean age of the patients was 52.7 years (range, 12–79 years). Overall, p-MEPUL resulted in MEP improvement in 25 of 26 (96%) patients, and p-MEPLL improved MEPs in 19 of 26 (73%) patients. The increase in MEP amplitudes were statistically significant in all muscle groups except left foot. Similar improvements were seen in the myelopathy group; in the neuropathy group, p-MEPUL produced similar results, but p-MEPLL did not. ConclusionsThe p-MEP technique can improve MEP amplitudes, including in patients with myelopathy. In patients with peripheral neuropathy, the results were mixed. SignificanceTetanic stimulation can enhance intraoperative MEP amplitudes.

Effectiveness of MEP and SSEP Monitoring in the Diagnosis of Neurological Dysfunction Immediately After Craniotomy Aneurysm Clipping.

To explore the diagnostic accuracy of motor-evoked potential (MEP) and somatosensory-evoked potential (SSEP) monitoring in predicting immediate neurological dysfunction after craniotomy aneurysm clipping. A total of 184 patients with neurosurgery aneurysms in the Affiliated Hospital of Qingdao University from April 2019 to December 2021 were retrospectively included. All patients underwent craniotomy aneurysm clipping, and MEP and SSEP were used to monitor during the operation. Receiver operating characteristic (ROC) curve analysis was used to determine the optimal cutoff value for early warning of MEP and SSEP amplitude decline and to evaluate the effectiveness of MEP and SSEP changes in predicting immediate postoperative neurological dysfunction. Among the 184 patients with intracranial aneurysms, the incidences of immediate postoperative neurological dysfunction were 44.4% (12/27) and 3.2% (5/157) in patients with intraoperative MEP changes and without changes, respectively. For SSEP, The incidence rates were 52.6% (10/19) and 4.2% (7/165), respectively, and the differences were statistically significant ( P <0.001). Significant changes in intraoperative MEP and SSEP were significantly associated with the development of immediate postoperative neurological deficits ( P <0.05). The critical values for early warning of MEP and SSEP amplitude decrease were: 61.6% ( P < 0.001, area under the curve 0.803) for MEP amplitude decrease and 54.6% ( P <0.001, area under the curve 0.770) for SSEP amplitude decrease. The sensitivity and specificity of MEP amplitude change in predicting immediate postoperative neurological dysfunction were 70.6% and 91.0%, respectively. For SSEP amplitude changes, the sensitivity and specificity were 58.8% and 95.8%, respectively. Motor-evoked potential and SSEP monitoring have moderate sensitivity and high specificity for immediate postoperative neurological dysfunction after craniotomy aneurysm clipping. Motor-evoked potential is more accurate than SSEP. Patients with changes in MEP and SSEP are at greatly increased risk of immediate postoperative neurologic deficits.

Intraoperative motor-evoked potential with tetanic stimulation changes pre- and post-hemispherotomy.

Careful examination of motor-evoked potential (MEP) findings is critical to the safety of intraoperative neuromonitoring during neurosurgery. We reviewed the intraoperative MEP findings in a pediatric patient who had undergone hemispherotomy for refractory epilepsy. The patient was a 4-year-and-2-month-old boy with extensive right cerebral hemisphere, drug-resistant epilepsy, left upper and lower extremity paralysis, and cognitive impairment. We examined intraoperative MEP results both before and after hemispherotomy. Post-hemispherotomy and MEPs were successfully elicited through transcranial electrical stimulation (TES) but not via direct cortical stimulation on the right side. Furthermore, TES on the right side, following hemispherotomy, led to a reduction in the MEP amplification effect resulting from tetanic stimulation of the left unilateral median and tibial nerves. Conversely, we observed the effects of MEP amplification during TES on the left side after tetanic stimulation of these nerves. Postoperatively, the patient underwent magnetic resonance imaging and electroencephalogram examinations, confirming the anatomical and electrophysiological completeness of the dissection. Notably, the seizures disappeared, and no apparent complications were observed. Collectively, our findings suggest that TES can still activate deep structures and elicit MEPs, even in cases where the corticospinal connections to the posterior limb of the internal capsule are entirely severed. Thalamo-cortical interactions may affect the MEP amplification, observed during tetanic stimulation. Injury to the corticospinal tracts of the white matter may be obscured on conventional MEP findings; however, it may be identified by MEP changes in tetanic stimulation.

Opportunities and challenges of supervised machine learning for the classification of motor evoked potentials according to muscles

BackgroundEven for an experienced neurophysiologist, it is challenging to look at a single graph of an unlabeled motor evoked potential (MEP) and identify the corresponding muscle. We demonstrate that supervised machine learning (ML) can successfully perform this task.MethodsIntraoperative MEP data from supratentorial surgery on 36 patients was included for the classification task with 4 muscles: Extensor digitorum (EXT), abductor pollicis brevis (APB), tibialis anterior (TA) and abductor hallucis (AH). Three different supervised ML classifiers (random forest (RF), k-nearest neighbors (kNN) and logistic regression (LogReg)) were trained and tested on either raw or compressed data. Patient data was classified considering either all 4 muscles simultaneously, 2 muscles within the same extremity (EXT versus APB), or 2 muscles from different extremities (EXT versus TA).ResultsIn all cases, RF classifiers performed best and kNN second best. The highest performances were achieved on raw data (4 muscles 83%, EXT versus APB 89%, EXT versus TA 97% accuracy).ConclusionsStandard ML methods show surprisingly high performance on a classification task with intraoperative MEP signals. This study illustrates the power and challenges of standard ML algorithms when handling intraoperative signals and may lead to intraoperative safety improvements.

Total Intravenous Anesthesia Protocol for Decreasing Unacceptable Movements during Cerebral Aneurysm Clipping with Motor-Evoked Potential Monitoring: A Historical Control Study and Meta-Analysis.

Injury can occur during intraoperative transcranial motor-evoked potential (MEP) monitoring caused by patient movement related to insufficient neuromuscular blocking agent use. Here, we evaluated the incidence of unacceptable movements in patients undergoing intraoperative MEP monitoring following our anesthetic protocol. We reviewed the anesthesia records of 419 patients who underwent unruptured cerebral aneurysm clipping with intraoperative MEP monitoring. The anesthetic protocol included target-controlled infusion with a fixed effect-site propofol concentration of 3 μg/mL and an adjustable effect-site remifentanil concentration of 10-12 ng/mL. We compared our findings of the intraoperative parameters and incidence of spontaneous movement and respiration with those of published meta-analysis studies. Spontaneous movement and respiration occurred in one (0.2%) patient each. The meta-analysis included six studies. The pooled proportions of spontaneous movement and respiration were 6.9% (95% confidence interval [CI], 1.3-16.5%) and 4.1% (95% CI, 0.5-14.1%), respectively. The proportion of spontaneous movement in our study was significantly lower than that in previous studies (p = 0.013), with no significant difference in spontaneous respiration (p = 0.097). Following our center's anesthesia protocol during cerebral aneurysm clipping resulted in a low incidence of spontaneous respiration and movement, indicating its safety for patients undergoing intraoperative MEP monitoring.

Motor Evoked Potential

Motor evoked potential(MEP)is the most widely used intraoperative neurophysiological monitoring measure. It includes cortical direct stimulation MEP(dMEP), which directly stimulates the primary motor cortex of the frontal lobe identified by short-latency somatosensory evoked potentials, and transcranial MEP(tcMEP), which involves high-current or high-voltage transcranial stimulation using cork-screw electrodes installed in the scalp. dMEP is performed in brain tumor surgery close to the motor area. tcMEP is simple, safe, and widely used in spinal and cerebral aneurysm surgeries. The increase in sensitivity and specificity with compound muscle action potential(CMAP)after peripheral nerve stimulation normalization performed in MEP to remove the effect of muscle relaxants is unclear. However, tcMEP for decompression in compressive spinal and spinal nerve diseases may predict the recovery of postoperative neurological symptoms with CMAP normalization. The anesthetic fade phenomenon can be avoided with CMAP normalization. The cutoff rate of loss of amplitude that causes postoperative motor paralysis in intraoperative MEP monitoring is 70%-80%, and setting an alarm at each facility based on this is necessary.

A Diffusion Tensor Imaging-Based Prognostic Classification for Surgery of Intrinsic Lesions Involving the Motor Pathways.

The critical role of different adjuncts in improving the neurological outcome in intrinsic brain lesions affecting eloquent areas is demonstrated by their more diffuse utilization. Neurosurgeons often rely on preoperative and intraoperative diffusion tensor imaging tractography to improve the operative strategy and prognosis. We aimed to identify and validate a diffusion tensor imaging-based classification considering the relationship between the brain lesion and the corticospinal tract to predict a >50% reduction of motor evoked potentials (MEPs) during surgical excision of lesions involving the motor pathways. We included patients consecutively enrolled at our institution between April 2020 and September 2022 with 3 patterns of increasing complexity according to the relationship between the lesion and the corticospinal tract as identified on preoperative diffusion tensor imaging. Outcome measures were >50% reduction in intraoperative MEPs and neurological outcome defined as unchanged, improved, or worsened. The study included 83 patients. A statistically significant linear trend between higher rates of reduction of MEPs and higher classification grades was observed (P= 0.001), with sensitivity 0.60, specificity 0.88, accuracy 0.83, and area under the curve 0.75. Higher grades were associated with worse neurological outcomes (P= 0.02). The classification proved reliable in anticipating reduction in intraoperative MEPs and in predicting neurological outcome. Using this classification in patients undergoing surgery for lesions involving the motor pathways could help in counseling the patient, surgical planning, enhancing teamwork of operating room personnel, and improving the patient's prognosis.

Association between Postoperative Neck Pain and Intraoperative Transcranial Motor-Evoked Potential Waveforms of the Trapezius Muscles in Patients with Cervical Myelopathy Who Underwent Cervical Laminoplasty.

Retrospective study. Cervical laminoplasty is safe and effective for treating cervical myelopathy but has a higher frequency of postoperative axial pain compared to other methods. Several studies have reported on the causes of postoperative axial pain, but none have fully elucidated them. This study aimed to investigate the association between postoperative neck pain and intraoperative transcranial motor-evoked potential (MEP) waveforms of the trapezius muscles using transcranial MEPs. Few studies have investigated the association between postoperative neck pain and intraoperative transcranial MEP waveforms of the trapezius muscles in patients with cervical laminoplasty. A total of 79 patients with cervical myelopathy who underwent cervical laminoplasty at our facility between June 2010 and March 2013 were included in this study. Intraoperative control and final waveform were evaluated based on the trapezius muscle MEPs by measuring the latency and amplitude. A neck pain group comprised patients with higher neck pain Visual Analog Scale scores from preoperative value to 1 year postoperatively. The cross-sectional areas of the trapezius muscles and the MEP latencies and amplitudes were compared between patients with and without neck pain. The latency and amplitude of the control waveforms were not significantly different between groups. The neck pain group had a significantly shorter final waveform latency (neck pain: 23.6±2.5, no neck pain: 25.8±4.5; p =0.019) and significantly larger amplitude (neck pain: 2,125±1,077, no neck pain: 1,630±966; p =0.041) than the no neck pain group. Postoperative neck pain was associated with the final waveform latency and amplitude of the trapezius muscle MEPs during cervical laminoplasty. Intraoperative electrophysiological trapezius muscle abnormalities could cause postoperative neck pain.

Effects of intraoperative motor evoked potential amplification following tetanic stimulation of the pudendal nerve in pediatric craniotomy.

Monitoring the intraoperative motor evoked potentials (MEPs) in pediatric craniotomy is challenging because of its low detection rate, which makes it unreliable. Tetanic stimulation of the peripheral nerves of the extremities and pudendal nerves prior to transcranial electrical stimulation (TES) or direct cortical stimulation (DCS) amplifies the MEPs. The authors investigated the effects of MEP amplification following tetanic stimulation of the median and tibial nerve or the pudendal nerve in pediatric patients undergoing craniotomy. This prospective observational study included 15 patients ≤ 15 years of age (mean age 8.9 ± 4.9 years) undergoing craniotomy. MEPs were obtained with TES (15 cases) or DCS (8 cases)-conventional MEP without tetanic stimulation (c-MEP) and MEP following tetanic stimulation of the unilateral median and tibial nerves (mt-MEP) or following tetanic stimulation of the pudendal nerve (p-MEP) were used. Compound muscle action potentials were elicited from the abductor pollicis brevis, gastrocnemius, tibialis anterior, and abductor hallucis longus muscles. The authors compared the identification rate and the rate of amplitude increase of each MEP. For both TES and DCS, the identification and amplitude increase rates were significantly higher in cases without preoperative hemiparesis for p-MEPs than in those for c-MEPs and mt-MEPs. In comparison to patients with preoperative hemiparesis, p-MEPs displayed a higher identification rate, with fewer false negatives in DCS cases. In pediatric craniotomy, the authors observed the amplification effect of MEPs with pudendal nerve tetanic stimulation and the amplification effect of DCS on MEPs without increasing false negatives. These findings suggested the likelihood of more reliable intraoperative MEP monitoring in pediatric cases.

Predictive Value of Motor Evoked Potentials in the Resection of Intradural Extramedullary Spinal Tumors in Children.

This study aimed to evaluate the predictive value of motor evoked potentials (MEP) in the resection of pediatric intradural extramedullary (IDEM) tumors. Additionally, we aimed to assess the impact of MEP alerts on the extent of tumor resection. Medical records of pediatric patients who underwent resection of IDEM tumors with the assistance of MEP between March 2011 and October 2020 were reviewed. The occurrence of postoperative motor deficits was correlated with intraoperative MEP alerts. Sixteen patients were included. MEP alerts appeared in 2 patients (12.5%), being reflective of new postoperative motor deficits. Among the remaining 14 patients without any intraoperative MEP alerts, no motor decline was found. Accordingly, MEP significantly predicted postoperative motor deficits, reaching sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 100% (p < 0.001). In the absence of MEP alerts, 11 out of 14 patients (78.6%) underwent GTR, while no patient with intraoperative IONM alerts underwent GTR (p = 0.025). Although MEP alerts limit the extent of tumor resection, the high sensitivity and PPV of MEP underline its importance in avoiding iatrogenic motor deficits. Concurrently, high specificity and NPV ensure safer tumor excision. Therefore, MEP can reliably support surgical decisions in pediatric patients with IDEM tumors.

Risk Factors for Cerebral Infarction After Microsurgical Clipping of Hunt-Hess Grade 0–2 Single Intracranial Aneurysm: A Retrospective Study

The study aimed to explore risk factors for cerebral infarction after microsurgical clipping in patients with Hunt-Hess grade 0-2 single intracranial aneurysms. A total of 137 patients with Hunt-Hess grade 0-2 single intracranial aneurysms treated with microsurgical clipping between March 2017 and December 2020 were retrospectively enrolled. Patients were divided into 2 groups on the basis of the occurrence of cerebral infarction after surgery. Of 137 enrolled patients, 14 (10.22%) showed cerebral infarction symptoms after surgery. Univariate analysis indicated that ruptured aneurysm status, aneurysm rupture during surgery, history of transient ischemic attack (TIA)/stroke, aneurysm size ≥7 mm, temporary clipping, intraoperative systolic hypotension (IOH), and occurrences of intraoperative motor-evoked potentials change were significantly related to postoperative cerebral infarction (PCI). However, using multivariate regression, only history of TIA/stroke (odds ratio= 0.124; 95% confidence interval [CI]= 0.021-0.748, P= 0.023) and IOH (odds ratio= 0.032; 95% CI= 0.005-0.210, P < 0.001) were independent predictors for PCI. Receiver operating characteristic curve analysis showed that the critical duration of temporary clipping and IOH that minimized the risk of PCI was 5.5 minutes and 7.5 minutes, respectively. Our study identified history of TIA/stroke and IOH as independent risk factors for cerebral infarction after microsurgical clipping.

The intraoperative motor-evoked potential when propofol was changed to remimazolam during general anesthesia: a case series.

Remimazolam is a short-acting benzodiazepine that was approved for clinical use in 2020. We report three patients who underwent surgery for cerebral and spinal cord tumors, in whom transcranial electrical stimulation-motor-evoked potential (TES-MEP) was successfully monitored under general anesthesia with remimazolam. During total intravenous anesthesia with propofol at a target concentration of 2.7 - 3.5µg/mL and 0.1 - 0.35µg/kg/min of remifentanil, delayed awakening, bradycardia, and hypotension during propofol anesthesia were expected in all three cases. With patient safety as the top priority, we considered changing the anesthetic agent. Propofol was replaced with remimazolam at a loading dose of 12mg/kg/h for a few seconds (case 3), followed by 1mg/kg/h for maintenance (cases 1-3). TES-MEP was recorded during propofol and remimazolam administration in all three patients. Amplitudes of TES-MEP during anesthesia with propofol and remimazolam were 461.5 ± 150µV and 590.5 ± 100.9µV, 1542 ± 127µV and 1698 ± 211µV, and 581.5 ± 91.3µV and 634 ± 82.7µV sequentially from Case 1. Our findings suggest that intraoperative TES-MEP could be measured when anesthesia was managed with remimazolam at 1mg/kg/h.

Incidence of ischemic complications and technical nuances of arteries preservation for insular gliomas resection.

IntroductionInsular gliomas have complex anatomy and microvascular supply that make resection difficult. Furthermore, resection of insular glioma is associated with a significant risk of postoperative ischemic complications. Thus, this study aimed to assess the incidence of ischemic complications related to insular glioma resection, determine its risk factors, and describe a single surgeon’s experience of artery-preserving tumor resection.MethodsWe enrolled 75 consecutive patients with insular gliomas who underwent transcortical tumor resection. Preoperative and postoperative demographic, clinical, radiological [including diffusion-weighted imaging (DWI)], intraoperative neurophysiological data, and functional outcomes were analyzed. Motor evoked potentials (MEPs) and radiological characteristics like the relationship between the proximal segment of the lateral lenticulostriate arteries (LLSAs) and the tumor, the flat inner edge sign (the inner edge of the insular glioma is well-defined) or obscure inner edge sign, the distance between the lesion and posterior limb of the internal capsule and the invasion of the superior limiting sulcus by the tumor were analyzed. Strategies such as “residual triangle,” “basal ganglia outline reappearance,” and “sculpting” technique were used to preserve the LLSAs and the main branches of M2 for maximal tumor resection according to the Berger–Sinai classification.ResultsPostoperative DWI showed acute ischemia in 44 patients (58.7%). Moreover, nine patients (12%) had developed new motor deficits, as determined by the treating neurosurgeons. The flat inner edge sign [odds ratio (OR), 0.144; 95% confidence interval (CI), 0.024–0.876) and MEPs (>50%) (OR, 18.182; 95% CI, 3.311–100.00) were significantly associated with postoperative core ischemia, which affected the posterior limb of the internal capsule or corona radiata.ConclusionsInsular glioma resection was associated with a high incidence of ischemia, as detected by DWI, as well as new motor deficits that were determined by the treating neurosurgeons. Insular glioma patients with obscure inner edge signs and intraoperative MEPs decline >50% had a higher risk of developing core ischemia. With our strategies, maximal safe resection of insular gliomas may be achieved.

Successful recording of direct cortical motor-evoked potential from a pediatric patient under remimazolam anesthesia: a case report

BackgroundIntraoperative motor-evoked potential (MEP) monitoring reduces postoperative motor deficits. Propofol-based total intravenous anesthesia is the gold standard for intraoperative myogenic MEPs. Although there is no contraindication to administering propofol in adults with peanut, soy, or egg allergies, its safety in children with these allergies remains unclear.Case presentationA 12-year-old girl required general anesthesia under intraoperative direct cortical MEP (dc-MEP) monitoring due to supratentorial glioma. Remimazolam-based anesthesia was selected, instead of propofol, due to the patient’s egg hypersensitivity. Stable myogenic MEPs were recorded throughout the surgery with remimazolam at 0.9 mg/kg/h and remifentanil at 0.35 μg/kg/min, following adjustments of stimulation intensity and titration of remimazolam infusion. Neither intraoperative memory nor motor deficits were present after surgery.ConclusionsWe present a pediatric case whose dc-MEP was recorded under remimazolam anesthesia. The cardiovascular stability and avoidance of propofol infusion syndrome with remimazolam were superior to propofol.

Intraoperative motor and somatosensory evoked potential monitoring during surgical clipping of ruptured and unruptured intracranial aneurysms: a comparative study.

The current study investigated the correlation between intraoperative motor evoked potential (MEP) and somatosensory evoked potential (SSEP) monitoring and both short-term and long-term motor outcomes in aneurysm patients treated with surgical clipping. Moreover, the authors provide a relatively optimal neurophysiological predictor of postoperative motor deficits (PMDs) in patients with ruptured and unruptured aneurysms. A total of 1017 patients (216 with ruptured aneurysms and 801 with unruptured aneurysms) were included. Patient demographic characteristics, clinical features, intraoperative monitoring data, and follow-up data were retrospectively reviewed. The efficacy of using changes in MEP/SSEP to predict PMDs was assessed using binary logistic regression analysis. Subsequently, receiver operating characteristic curve analysis was performed to determine the optimal critical value for duration of MEP/SSEP deterioration. Both intraoperative MEP and SSEP monitoring were significantly effective for predicting short-term (p < 0.001 for both) and long-term (p < 0.001 for both) PMDs in aneurysm patients. The critical values for predicting short-term PMDs were amplitude decrease rates of 57.30% for MEP (p < 0.001 and area under the curve [AUC] 0.732) and 64.10% for SSEP (p < 0.001 and AUC 0.653). In patients with an unruptured aneurysm, the optimal critical values for predicting short-term PMDs were durations of deterioration of 17 minutes for MEP (p < 0.001 and AUC 0.768) and 21 minutes for SSEP (p < 0.001 and AUC 0.843). In patients with a ruptured aneurysm, the optimal critical values for predicting short-term PMDs were durations of deterioration of 12.5 minutes for MEP (p = 0.028 and AUC 0.706) and 11 minutes for SSEP (p = 0.043 and AUC 0.813). The authors found that both intraoperative MEP and SSEP monitoring are useful for predicting short-term and long-term PMDs in patients with unruptured and ruptured aneurysms. The optimal intraoperative neuromonitoring method for predicting PMDs varies depending on whether the aneurysm has ruptured or not.

Motor evoked potentials versus Macrostimulation in predicting the postoperative motor threshold in STN Deep brain stimulation

IntroductionAccuracy is crucial in Deep Brain Stimulation (DBS). Electrophysiological and image-based techniques are used to avoid suboptimal positioning. Macrostimulation is the gold standard to delineate the therapeutic window intraoperatively. Despite this, electrode revision rates due to malpositioning are as high as 17%. The goal was to compare motor evoked potentials (MEPs) with the gold standard of Macrostimulation. We assessed accuracy and precision as well as the correlation in predicting motor side effects at the initial mapping 4 weeks postoperatively. MethodsIn this prospective study intraoperative MEPs from 94 contacts in 16 patients undergoing STN DBS under local anesthesia were correlated to the postoperative threshold for stimulation-induced motor side effects and compared to intraoperative Macrostimulation. Analysis of accuracy, precision and correlation (Pearson) was performed. ResultsMEPs of the upper extremity had a mean percentage error of 25% (SD 38.8%) and correlated significantly with the motor threshold at postoperative mapping (R=0.235). Macrostimulation was less accurate and precise with a mean percentage error of − 68% (SD 78.8%) but had a higher correlation (R=0.388). MEPs rarely (3%) overestimated the threshold by maximally 1 mA. In contrast, Macrostimulation overestimated the threshold by over 1 mA in 69% leading to a false sense of security. ConclusionMEPs are feasible in an awake setting during Deep Brain Stimulation in the STN for PD patients. MEPs of the upper extremity are more accurate and precise predicting the motor threshold and avoid a false sense of security in comparison to the gold standard of Macrostimulation.