Motor Evoked Potential Monitoring Research Articles

Does persistent crossover (ipsilateral) motor evoked potential (MEP) responses represent a technical failure for intracranial motor tract monitoring? A case example and practical solution.

Attention to motor evoked potential (MEP) stimulation intensity is necessary to avoid false negative MEP results during intracranial procedures. Observing ipsilateral (crossover) MEP responses has been hypothesized to indicate inappropriately strong stimulation intensity. We describe a case where persistent crossover MEP responses falsely suggested that stimulus intensity was too high and describe an alternative method to guide the selection of MEP stimulation intensity. A patient undergoing a suboccipital craniotomy for tumor resection had bilateral transcranial electrical MEP monitoring under total intravenous anesthesia. MEP results were obtained from left and right hand using C4-Cz and C3-Cz stimulation montages respectively. Selection of an appropriately superficial stimulus intensity was guided using MEP onset latencies. MEP acquisition proceeded normally for contralateral left hand (C4-Cz montage). However, using the C3-Cz montage, persistent crossover responses were noted at stimulation intensities as low as threshold for contralateral right hand MEP (94V/166mA). Appropriate MEP stimulus intensity for subsequent monitoring (approximately 96V/172mA) was determined utilizing onset latency measurements from contralateral hand MEP responses. The stimulus intensity chosen was predicated on onset latency being ≥ 2 ms longer than latency at maximal stimulus level (shortest latency). A stimulus intensity-latency plot was generated offline to illustrate this important relationship for intracranial MEP use. MEP acquisition proceeded without incident and gross total resection was achieved without postoperative motor deficits. Despite crossover appearance contralateral hand MEP were quantitatively validated for intraoperative application using onset latency guidance.

Evaluation of post-tetanic motor evoked potential as an augmentation technique under partial neuromuscular blockade during craniotomy

ObjectiveIn craniotomies requiring motor evoked potential (MEP) monitoring, avoiding neuromuscular blockade (NMB) is preferable, but its complete avoidance poses risks of unexpected movement. This retrospective study investigates the application of a post-tetanic MEP augmentation technique to enhance baseline recording of transcranial stimulation MEP (Tc-MEP) under partial NMB during craniotomy. MethodsTwenty-six patients were included. The level of partial NMB was maintained at a train-of-four ratio of approximately 40 %. Monophasic constant-current stimulation was applied on the craniotomy side with + 20 % of the threshold intensity. Post-tetanic Tc-MEP, involving tetanic stimulation of the median nerve 1 s before transcranial stimulation, was performed on patients who failed to record using conventional baseline recording. ResultsThe post-tetanic Tc-MEP technique successfully improved the success rate of baseline recording from 61.5 % to 100 %. Application of post-tetanic Tc-MEP significantly increased amplitudes in both the upper (p = 0.04) and lower limbs (p < 0.01) compared to before post-tetanic Tc-MEP. No patients had unexpected movements. ConclusionsThis study indicates that post-tetanic Tc-MEP enhanced the success rate of baseline recording during craniotomy under partial NMB. SignificanceThe combination of partial NMB and post-tetanic Tc-MEP could be a useful regimen for craniotomy with MEP monitoring, addressing both safety concerns and successful baseline recording.

Visualizing Intraoperative Transcranial Motor-Evoked Potentials During Glioma Surgery for Predicting Postoperative Paralysis Prognosis

The primary goals of glioma surgery are maximal tumor resection and preservation of brain function. Intraoperative motor-evoked potential (MEP) monitoring is commonly used to predict and minimize postoperative paralysis. However, studies on intraoperative MEP trends and postoperative paralysis are scarce. This study aimed to determine the relationship between intraoperative MEP trends and postoperative paralysis. This retrospective study evaluated 229 patients with supratentorial glioma without preoperative paralysis who underwent tumor resection surgery under general anesthesia at our institution between October 2019 and December 2022. Intraoperative transcranial MEP monitoring was performed, and the entire MEP trends on affected and unaffected sides was visualized. Postoperative paralysis and patient-related factors were analyzed. Postoperative paralysis occurred in 36 patients, with the paralysis improving over time and being permanent in 30 and 6 patients, respectively. In the improvement group, the temporary decrease in transcranial MEP rapidly improved. Even when the MEPs were <50% of the control value, fluctuations indicating improvement were observed after the decrease. However, in the permanent paralysis group, transcranial MEP remained consistently <50% of the control value until the end of surgery, after its initial decrease. The significant factors contributing to permanent paralysis were tumor localization close to the pyramidal tract (p = 0.0304) and postoperative cerebral infarction in the pyramidal tract (p = 0.0009). The overall intraoperative MEP trend can reflect the risk of postoperative paralysis during glioma surgery. Thus, visualizing this trend can provide a better understanding of the prognosis of postoperative paralysis.

The Improvement of Intraoperative Motor Evoked Potential after Decompression in Cervical Compressive Myelopathy: Its Significance and Related Factors

Objective: This study investigated the relationship between intraoperative motor evoked potential (MEP) improvement after decompression surgery for cervical compressive myelopathy (CCM) and postoperative neurological outcomes, and preoperative factors influencing MEP improvement.Methods: MEP amplitudes were measured prospectively before and after decompression in 38 patients with CCM. The patients were categorized into three groups according to whether the intraoperative MEP slightly decreased, slightly increased, or significantly increased. Functional outcomes were assessed using the recovery rate (RR) and absolute improvement (AI) of the modified Japanese Orthopaedic Association score on postoperative days (PODs) 7 and 28. The preoperative characteristics and intraoperative MEP changes among the three groups were compared. Additionally, the correlation between the increase in MEP amplitude during surgery and the extent of improvement in functional outcomes was investigated.Results: The significantly increased MEP group had a lower baseline MEP amplitude (152.46 µV; p=0.009). In the slightly decreased MEP group, the RR was 27.98 ± 32.29% at POD 7 (p=0.010) and 11.61 ± 69.84% at POD 28 (p=0.200); the AI was 0.79 ± 0.80 at POD 7 (p=0.010) and 0.79 ± 1.42 at POD 28 (p=0.100). In the slightly increased MEP group, the RR was 23.75 ± 28.36% at POD 7 (p=0.040) and 28.47 ± 43.38% at POD 28 (p=0.070); the AI was 1.00 ± 1.21 at POD 7 (p=0.030) and 1.08±1.88 at POD 28 (p=0.100). In the significantly increased MEP group, the RR was 41.06 ± 32.01% at POD 7 (p=0.009) and 59.78 ± 34.52% at POD 28 (p=0.006); the AI was 3.08 ± 2.07 at POD 7 (p=0.009) and 4.33 ± 2.54 at POD 28 (p=0.006). Greater intraoperative MEP improvement correlated with better postoperative recovery at 1 month (RR, p=0.010; AI, p&lt;0.001).Conclusion: Intraoperative MEP monitoring is valuable for predicting postoperative neurological outcomes in CCM patients, particularly those with lower baseline MEP amplitudes. Significant intraoperative MEP improvements are associated with better functional recovery. These findings underscore the importance of MEP monitoring in optimizing surgical strategies and predicting neurological recovery.

Novel technique of switching TIVA and sevoflurane during epilepsy surgery for combined intraoperative motor evoked potentials monitoring and electrocorticography: an illustrative case report

BackgroundDuring epilepsy surgery, it is equally important to record electrocorticography (ECoG) for detecting epileptogenic activity and guiding brain resection, and to evaluate neuromonitoring data, particularly motor evoked potentials (MEP), for avoidance of postoperative neurological complications. However, sevoflurane, which is commonly used during recording of ECoG, may attenuate the MEP response. It enforces anesthesiologists and neurosurgeons to select one anesthetic agent over another, facilitating either ECoG or MEP monitoring.Case presentationIn the presented case of a 20-year-old man, who underwent surgery for temporal lobe epilepsy, a novel technique of neuroanesthesia was introduced, integrating initial induction of the total intravenous anesthesia (TIVA) with propofol (effect-site concentration, 2.3–3.0 μg/ml), its subsequent switching to sevoflurane (end-tidal concentration, 2.5%) for ECoG recording, and further change back to TIVA for MEP monitoring during brain resection.ConclusionsIntraoperative switch of anesthetic agents according to specific intraoperative requirements may be useful for cases of brain surgery requiring both ECoG recordings and MEP monitoring.

Transcranial Corticospinal Motor-Evoked Potentials in Cases of Ventral and Ventrolateral Intradural Extramedullary Cervical Spinal Cord Tumors.

Background and Objectives: We studied the clinical significance of an amplitude decrement and disappearance alarm criteria in transcranial motor-evoked potential (MEP) monitoring during surgeries on extramedullary tumors at the cervical spine with reference to postoperative morbidity. Material and Methods: We diagnosed and surgically treated fourteen patients with intradural extramedullary ventral or ventrolateral lesions to the cervical spinal cord in the Clinic of Neurosurgery at the University Hospital St Ivan Rilski from January 2018 to July 2022. Eight cases were diagnosed with schwannoma, and the remaining six had meningiomas. The follow-up period for neurological assessment was six months. Results: A decrease in the intraoperative transcranial MEPs of 50% or more compared to baseline in two cases (14.3%) resulted in an immediate postoperative motor deficit. One patient demonstrated full neurological recovery within six months, while the other exhibited only partial improvement. In six cases (42.9%) with preoperative motor deficits, tumor resection and decompression of the cervical spinal cord led directly to an increment of the transcranial MEPs by more than 20%. Postoperatively and at the 6-month follow-up, these patients showed recovery from the preoperative deficits. In the remaining cases, MEPs were stable during surgery with no clinical deterioration of the motor function. Conclusions: The decremented MEP criteria corresponded to postoperative motor deficit, whereas the improvement of the same parameters after decompression implied future recovery of preoperative motor deficits. The combination of different MEP criteria is likely to be helpful when tailored to a specific case of ventral or ventrolateral extramedullary lesions in the cervical spine.

Effect of propofol infusion vs ketamine plus dexmedetomidine infusion on the amplitude of motor evoked potential in pediatric patients undergoing tethered spinal cord surgeries; a randomized, double blind controlled study

Background &amp; objective: The use of intraoperative neurophysiologic monitoring (IOM) has increased over the past two decades for the detection and prevention of iatrogenic neurologic injuries. Motor evoked potentials (MEP) are extremely sensitive to changes in physiological variables and inhalational agents reduce MEPs in a dose dependent manner. So IV anesthetics (propofol or ketamine) and opioids (fentanyl or remifentanil), are frequently used in spinal surgeries under MEPs monitoring. We compared the effects of propofol and fentanyl to those of ketamine, dexmedetomidine, and fentanyl in terms of minimizing their effects on MEP amplitude and hemodynamic stability during surgery Methodology: This double blind, randomized, prospective study was conducted on 46 children, who were randomly allocated into 2 groups Ketamine–dexmedetomidine group: (n = 23) Maintenance throughout the procedure, by infusing Dexmedetomidine (0.4 -0.6 μg/.kg /.hr) ketamine, (1 -2m/.kg/.hr.) and giving bolus of fentanyl, (1-2μg/.kg/ ). Propofol-group:(n = 23) Maintenance throughout the procedure, By infusing propofol (100 ug L/kg/min) and giving bolus of fentanyl, (1-2μg/.kg/ ), with keeping mean arterial blood pressure changes within 25% of the baseline in both groups. Results: Right and left quadriceps muscle measurements were insignificantly different between both groups at base line and were significantly higher in Group KD than Group P at skin incision, surgical manipulation and surgical closure. Right and left adductor hallucis muscle measurements were insignificantly different between both groups at base line and were significantly higher in Group KD than Group P at 5 mins, 10 mins, 15 mins, skin incision, surgical manipulation and surgical closure (P value &lt;0.001). Intraoperative fentanyl consumption was significantly lower in Group KD than Group P. Conclusion: The combination of dexmedetomidine and ketamine infusion is efficacious, safe, and has minimal effect on evoked potentials compared with the propofol-based TIVA group during spine pediatrics surgery. In addition, this combination increases the reliability and accuracy of MEP monitoring with hemodynamic stability and adequate post-operative pain relief. Using dexmedetomidine and ketamine infusions during pediatric spine surgery might successfully replace the typical propofol-based TIVA, although more studies are required . Registration: ClinicalTrials.gov registration number NCT05591001. Keywords: Motor evoked potential, dexmedetomidine, ketamine, propofol. Citation: Saleh AH, Hammad SH, Hassan PF. Effect of propofol infusion vs ketamine plus dexmedetomidine infusion on the amplitude of motor evoked potential in pediatric patients undergoing tethered spinal cord surgeries; a randomized, double blind controlled study. Anaesth. pain intensive care 2024;28(4):692−699; DOI: 10.35975/apic.v28i4.2218 Received: May 08, 2023; Reviewed: February 02, 2024; Accepted: July 03, 2924

Novel Use of Motor-Evoked Potential Monitoring During Magnetic Resonance Imaging-Guided Soft-Tissue Cryoablation: A Case Report

Motor-evoked potential (MEP) monitoring is an electrophysiologic technique useful for testing peripheral motor nerve integrity during cryoablation cases with risk of nerve injury. Previously, neuromonitoring within the magnetic resonance imaging (MRI) suite for cryoablation has not been performed as magnetic needles are used which could cause magnetic field interactions with neuromonitoring leads. We present the first report of a patient who underwent MEP monitoring during MRI-guided cryoablation of a vascular malformation adjacent to the brachial plexus. We demonstrate that MEPs may be safely and accurately performed by interleaving MRI and MEPs during treatment, reducing the risk of postprocedural complications.

Intraoperative Neuromonitoring for the Lower-Extremity Region Using Motor-Evoked Potential With Direct Cortical Stimulation in Brain Tumor Surgeries.

To evaluate the motor function of the lower extremity (LE), we used direct cortical stimulation motor-evoked potential (D-MEP) monitoring with a single six-contact subdural strip electrode placed in the interhemispheric fissure. Intraoperative neuromonitoring using D-MEPs in the LE was performed in 18 cases (16 patients) for brain tumor surgery from December 2018 to April 2023 with a follow-up period of at least 3 months. After dural opening, a single six-contact subdural strip electrode was placed inside the interhemispheric fissure. To identify the central sulcus, phase reversal was recorded using somatosensory evoked potentials. Next, direct cortical stimulation was applied to the primary motor cortex. The baseline waveform was defined as a reproducible waveform of 30 µV or higher, and a significant decrease of ≥50% in the amplitude resulted in a warning during surgery. The success rate of central sulcus identification in the LE was 66.7% (12/18 cases). Direct cortical stimulation motor-evoked potential monitoring could record stable contralateral motor-evoked potentials of the tibialis anterior, gastrocnemius, and abductor hallucis in 16 of 18 cases (88.9%). The mean intensity of stimulation for D-MEPs was 20.5 ± 9.9 mA, and the 16 cases showed no significant reduction in amplitude. Seventeen cases showed no deterioration of motor function of the LE at 1 and 3 months postoperatively. In the remaining case with unsuccessful D-MEP, paralysis of the LE worsened at 1 and 3 months postoperatively. The placement of electrodes in the interhemispheric fissure on the primary motor cortex of the LE enabled motor-function monitoring in the LE with D-MEPs, suggesting that D-MEP-based monitoring may be a reliable approach.

Diagnostic Accuracy of Somatosensory Evoked Potential and Transcranial Motor Evoked Potential in Detection of Neurological Injury in Intradural Extramedullary Spinal Cord Tumor Surgeries: A Short-Term Follow-Up Prospective Interventional Study Experience from Tertiary Care Center of India.

Objective Intraoperative neuromonitoring (IONM) is an acknowledged tool for real-time neuraxis assessment during surgery. Somatosensory evoked potential (SSEP) and transcranial motor evoked potential (MEP) are commonest deployed modalities of IONM. Role of SSEP and MEP in intradural extramedullary spinal cord tumor (IDEMSCT) surgery is not well established. The aim of this study was to evaluate sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and transcranial MEP, in detection of intraoperative neurological injury in IDEMSCT patients as well as their postoperative limb-specific neurological improvement assessment at fixed intervals till 30 days. Materials and Methods Symptomatic patients with IDEMSCTs were selected according to the inclusion criteria of study protocol. On modified McCormick (mMC) scale, their sensory-motor deficit was assessed both preoperatively and postoperatively. Surgery was done under SSEP and MEP (transcranial) monitoring using appropriate anesthetic agents. Gross total/subtotal resection of tumor was achieved as per IONM warning alarms. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and MEP were calculated considering postoperative neurological changes as "reference standard." Patients were followed up at postoperative day (POD) 0, 1, 7, and 30 for convalescence. Statistical Analysis With appropriate tests of significance, statistical analysis was carried out. Receiver-operating characteristic curve was used to find cutoff point of mMC for SSEP being recordable in patients with higher neurological deficit along with calculation of sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and MEP for prediction of intraoperative neurological injury. Results Study included 32 patients. Baseline mean mMC value was 2.59. Under neuromonitoring, gross total resection of IDEMSCT was achieved in 87.5% patients. SSEP was recordable in subset of patients with mMC value less than or equal to 2 with diagnostic accuracy of 100%. MEP was recordable in all patients and it had 96.88% diagnostic accuracy. Statistically significant neurological improvement was noted at POD-7 and POD-30 follow-up. Conclusion SSEP and MEP individually carry high diagnostic accuracy in detection of intraoperative neurological injuries in patients undergoing IDEMSCT surgery. MEP continues to monitor the neuraxis, even in those subsets of patients where SSEP fails to record.

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

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

Unilateral abnormality of initial motor-evoked potential in the upper limb detected during lumbar spine surgery: a case report

BackgroundWe present a case with abnormal findings of initial motor-evoked potential (MEP) in the left upper limb after prone positioning during lumbar spine surgery.Case presentationA 71-year-old man with bilateral lower extremity numbness without a history of preexisting motor weakness underwent L3–5 spinal fenestration. Initial MEP monitoring after prone positioning revealed markedly prolonged latency and lower amplitude in the left abductor pollicis brevis (APB). Because the left upper limb somatosensory-evoked potentials had normal values, a position-related impending peripheral nerve injury located between the neck and the forearm was excluded. Postoperative examination revealed that MEP abnormality in the left APB was caused by carpal tunnel syndrome.ConclusionsAbnormal initial MEP from the upper limb was unexpectedly detected after prone positioning during lumbar spine surgery. The condition was caused by preexisting carpal tunnel syndrome.

Anesthesia Considerations in Patients Undergoing Spine Surgery with Evoked Potential Monitoring

Intra-operative neuromonitoring (IONM) facilitates monitoring of the functional integrity of neural structures under general anesthesia. It aids in early detection of injury and minimizes postoperative neurologic deficit. IONM may be used during spine surgery, where either the blood supply to the spinal cord could be compromised or the surgical procedures where there is manipulation of the spinal cord. Somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) are used to monitor the sensory and motor tracts in the spinal cord, respectively. Preoperatively, a team of surgeons, anesthetists, and neurophysiologists must discuss about modalities of IONM to be used, expected changes, and alarm criteria. Anesthesia drugs need to be appropriately selected to facilitate IONM, as they affect the SSEP and MEP response obtained. Both total intravenous anesthesia and balanced anesthesia technique may be used, with appropriate titration of drugs. False-positive changes in evoked potentials (EPs) must be prevented by a steady anesthesia state and physiologic parameters. It is preferable to have a checklist to follow whenever changes in EP response are observed to rule out surgical, anesthetic, and monitoring-related causes for change in response. Risk–benefit must be assessed before the selection of a patient for EP monitoring as it may be rarely associated with complications such as burns, seizures, and bite injuries to lips, tongue, and endotracheal tube. Teamwork with meticulous planning, preparation, and multidisciplinary communication is essential for the safe conduct of spine surgeries with SSEP and MEP monitoring. In this review, we discuss various considerations for anesthesia management in patients with intraoperative EP monitoring.

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.

Treatment Outcomes in Patients with Unruptured Anterior Choroidal Artery Aneurysms: A Single-Center Experience.

Treatment of anterior choroidal artery (AChA) aneurysms is frequently associated with ischemic complications. This study aimed to report the outcomes of treatment of unruptured AChA aneurysms in our hospital. Between January 2015 and March 2022, 40 patients were treated for an unruptured AChA aneurysm in our hospital. Age, sex, aneurysm size, AChA branching type, treatment, occlusion rate, complications, modified Rankin Scale (mRS) score before surgery and after 90 days, and recurrence were investigated. The branching type was classified as internal carotid artery (ICA), neck, or dome type based on the location of the AChA origin. The mean age was 61.1 ± 1.9 years; 15 patients were men and 25 were women. The mean aneurysm diameter was 4.4 ± 0.3 mm. The branching type was ICA in four patients, neck in 35, and dome in one. Treatment was surgical clipping in 22 patients and endovascular coil embolization in 18 (14 with stent assistance). Motor-evoked potential (MEP) monitoring was used in all patients of the clipping group and 9 cases of the coiling group. Treatment complications occurred in eight patients (20%). mRS score worsened by more than one point 90 days after treatment in four patients (10%); however, the proportion of patients who experienced this did not significantly differ between the clipping and coiling groups. Although the odds of a thrombotic complication were higher with coiling than clipping, the difference was not significant (odds ratio: 10.2; P = 0.08). The rate of complete occlusion was lower in the coiling group (72.2% vs. 95.3%), but the difference was not significant. The median follow-up was 696 days (range: 99-2053). No aneurysm recurrence or rupture occurred. AChA branching type is important for treatment decision-making in patients with AChA aneurysms. Rates of complications and occlusion do not significantly differ between clipping and coiling of AChA aneurysms. MEP monitoring may be useful in preventing thrombotic complications during coil embolization.

Multimodal Intraoperative Neurophysiological Monitoring in Intramedullary Spinal Cord Tumors: A 10-Year Single Center Experience.

The study aimed at evaluating the efficacy and the ability of D-wave monitoring combined with somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) to predict functional outcomes in intramedullary spinal cord tumor (IMSCT) surgery. Between December 2011 and December 2020, all patients harboring IMSCT who underwent surgery at our institution were prospectively collected in a surgical spinal registry and retrospectively analyzed. Patient charts and surgical and histological reports were analyzed. The multimodal IONM included SSEPs, MEPs, and-whenever possible-D-waves. All patients were evaluated using the modified McCormick and Frankel grade at admission and 3, 6, and 12 months of follow-up. Sixty-four patients were enrolled in the study. SSEP and MEP monitoring was performed in all patients. The D-wave was not recordable in seven patients (11%). Significant IONM changes (at least one evoked potential modality) were registered in 26 (41%) of the 64 patients. In five cases (8%) where the SSEPs and MEPs lost and the D-wave permanently dropped by about 50%, patients experienced a permanent deterioration of their neurological status. Multimodal IONM (SSEP, MEP, and D-wave neuromonitoring) significantly predicted postoperative deficits (p = 0.0001), with a sensitivity of 100.00% and a specificity of 95.65%. However, D-waves demonstrated significantly higher sensitivity (100%) than MEPs (62.5%) and SSEPs (71.42%) alone. These tests' specificities were 85.10%, 13.89%, and 17.39%, respectively. Comparing the area under ROC curves (AUCs) of these evoked potentials in 53 patients (where all three modalities of IONM were registered) using the pairwise t-test, D-wave monitoring appeared to have higher accuracy and ability to predict postoperative deficits with strong statistical significance compared with MEP and SSEP alone (0.992 vs. 0.798 vs. 0.542; p = 0.018 and p < 0.001). The use of multimodal IONM showed a statistically significant greater ability to predict postoperative deficits compared with SSEP, MEP, and D-wave monitoring alone. D-wave recording significantly increased the accuracy and clinical value of neurophysiological monitoring in IMSCT tumor resection.

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.

Comparison Between Cz-C3/C4 and C3-C4 Montages to Protect Against Peripheral Stimulation in Transcranial Facial Motor-Evoked Potential Monitoring.

In facial motor-evoked potential monitoring, efforts to reduce peripheral stimulation are necessary because it can cause false-negatives. The effects of peripheral stimulation on Cz-C3/C4 and C3-C4 montages were compared. Facial motor-evoked potentials were recorded from bilateral orbicularis oculi (Oculi) and oris (Oris) muscles. The double-train approach combining single-pulse and five-train pulse stimulation was used to determine the effect of peripheral stimulation. If the five-train pulse produced a significant waveform, it was defined as "total success." In total success cases, "true success" was defined as a case in which no waveform appeared after the single pulse at the threshold level of the five-train pulse. The total and true success rates and the threshold value of Oculi and Oris were compared between Cz-C3/C4 and C3-C4 montages. Thirty-six muscles each of Oculi and Oris of 18 patients were used for the analysis. True success was more likely to be obtained by the Cz-C3/C4 montage than the C3-C4 montage in Oculi (42% vs. 22%, p = 0.039). Both Oculi and Oris had higher thresholds to elicit facial motor-evoked potentials with the Cz-C3/C4 montage (Oculi: 101.7 vs. 71.4 mA, p = 0.038; Oris: 94.8 vs. 73.1 mA, p = 0.016). Cz-C3/4 montage is more effective at reducing peripheral stimulation compared with the C3-4 montage. This effect was primarily seen in the orbicularis oculi muscle. It should be noted that the Cz-C3/C4 montage has a higher threshold than the C3-C4 montage in facial muscles. In facial motor-evoked potential monitoring, the Cz-C3/C4 montage may be more suitable to eliminate peripheral stimulation.

Neurophysiologic cut off values for safe resection of patients with supratentorial gliomas.

Gliomas have infiltrative nature and tumor volume has direct prognostic value. Optimal resection limits delineated by high-frequency monopolar stimulation with multipulse short train technique is still a matter of debate for safe surgery without (or with acceptable) neurological deficits. It is also an enigma whether the same cut-off values are valid for high and low grades. We aimed to analyze the value of motor mapping/monitoring findings on postoperative motor outcome in diffuse glioma surgery. Patients who were operated on due to glioma with intraoperative neuromonitorization at our institution between 2017 and 2021 were analyzed. Demographic information, pre- and post-operative neurological deficit, magnetic resonance images, resection rates, and motor evoked potential (MEP) findings were analyzed. Eighty-seven patients of whom 55 had high-grade tumors were included in the study. Total/near-total resection was achieved in 85%. Subcortical motor threshold (ScMTh) from resection cavity to the corticospinal tract was ≤ 2mA in 17; 3 mA in 14; 4 mA in 6; 5 mA in 7, and ≥5mA in 50 patients. On the 6th month examination, six patients (5 with high-grade tumor) had motor deficits. These patients had changes in MEP that exceeded critical threshold during monitoring. Receiver operating characteristic analysis revealed 2.5 mA ScMTh as the cut-off point for limb paresis after awakening and 6 months for the groups. Subcortical mapping with MEP monitoring helps to achieve safe wider resection. The optimal safe limit for SCMTh was determined as 2.5 mA. Provided that safe threshold values are maintained in MEP, surgeon may force the functional limits by lowering the SCMTh to 1 mA, especially in low-grade gliomas.

A bispectral index guided comparative evaluation of dexmedetomidine as an adjuvant to propofol-based total intravenous anaesthesia in spine surgeries done under motor-evoked potential monitoring

BackgroundThe anaesthetic agents can affect the quality of motor-evoked potential intraoperatively as they inhibit synaptic transmission. Intravenous anaesthetics suppress motor-evoked potential lesser than inhalational agents, so total intravenous anaesthesia or a combination of intravenous with minimal inhalational anaesthetic supplementation is used when motor-evoked potential is monitored. Motor-evoked potential can get depressed at high doses of propofol required to maintain surgical depth, hence, adjuvant agents like dexmedetomidine that maintain anaesthetic depth without affecting the motor-evoked potential are often required. This study was a prospective non-randomized and comparative study (quasi-experimental) assigned into two groups of 64 each, labelled as the propofol group (group P) and Propofol + dexmedetomidine group (group PD). The primary objective of our study was to compare the total dose reduction of propofol with the addition of dexmedetomidine and their interference with motor-evoked potential readings. The secondary objective was to assess the hemodynamic changes, changes in amplitude and latency of motor-evoked potential, and complications if any.ResultsThe mean total dose of propofol consumed in our study was 502.81 ± 71.01 mg in group propofol( P) and 392.18 ± 59.00 mg in group propofol + dexmedetomidine (PD). Moreover, the mean total dose of propofol (mg) was significantly less used in group PD. Intraoperative hemodynamic stability, no difference in amplitude and latency for motor-evoked potential, and only significant bradycardia in group propofol + dexmedetomidine (PD).ConclusionsDexmedetomidine can be successfully used in propofol-based total intravenous anaesthesia for motor-evoked potential monitoring in spine surgeries, but it is better to maintain stable hemodynamics with a significant reduction of the mean dose of propofol.