Application of Intraoperative Contrast-Enhanced Ultrasound in the Resection of Brain Tumors.

OBJECTIVE: To investigate the value of routine intraoperative ultrasound (IU) and intraoperative contrast-enhanced ultrasound (ICEUS) in the surgical treatment of brain tumors, and to explore the utilization of ICEUS for the removal of the remnants surrounding the resection cavity. METHODS: In total, 51 patients who underwent operations from 2012 to 2018 due to different tumors in the brain were included in this study. The clinical data were evaluated retrospectively. IU was performed in all patients, among which 28 patients underwent ICEUS. The effects of IU and ICEUS on tumor resection and recurrence were evaluated. Semiquantitative analysis was performed to compare ICEUS parameters of the brain tumor with those of the surrounding tissue. RESULTS: In total, 36 male and 15 female patients were included in this study. The average age was 43 years (range: 14-68 years). The follow-up period was from 7 to 74 months (mean follow-up 32 months). IU was used in all patients, and no lesion was missed. Among them, 28 patients underwent ICEUS. The rate of total removal of the ICEUS group (23/28, 82%) was significantly higher than that of the IU group (11/23, 48%) (P<0.05). The recurrence rate of ICEUS and IU was 18% (5/23), and 22% (5/28), respectively, and the difference did not reach statistical significance (P>0.05). The semiquantitative analysis showed that the intensity and the transit time of microbubbles reaching the lesions were significantly different from the intensity and the transit time of microbubbles reaching the surrounding tissue (P<0.05) and reflected indirectly the volume and the speed of blood perfusion in the lesions was higher than those in the surrounding tissue. CONCLUSION: ICEUS is a useful tool in localizing and outlining brain lesions, especially for the resection of the hypervascular lesions in the brain. ICEUS could be more beneficial for identifying the remnants and improving the rate of total removal of these lesions than routine intraoperative ultrasound.

Misconceptions in IONM Part I: Interleaved Intraoperative Somatosensory Evoked Potential Stimulation.

A misconception in the field of intraoperative neurophysiological monitoring (IONM) is that continuous, multi-nerve (four-limb), interleaved somatosensory evoked potential (SSEP) stimulation, while advantageous, is not universally utilized due to variety of misunderstandings regarding this approach to SSEP stimulation. This article addresses the rationale for this misconception. We find that continuous, multi-nerve, interleaved SSEP stimulation is superior to all other stimulation paradigms in most operative scenarios, allowing the fastest acquisition of SSEPs at low stimulation repetition rates, which generate the highest amplitude cortical responses.

The utility of intraoperative ECoG in tumor-related epilepsy: Systematic review.

OBJECT: Epilepsy is one of the most common clinical manifestations of primary brain tumors. Intraoperative electrocorticography (ECoG) has been widely used in tumor resection. We aim to describe the indication and utility of ECoG during brain tumor surgery. METHODS: We performed a systematic review of the literature on the prognosis of tumor-related epilepsy surgery guided by intraoperative ECoG. The published studies were searched in PubMed, Embase, and Web of Science using the keyword 'seizure' or 'epilepsy' and 'electrocorticography' or 'ECoG'. Two reviewer authors screened studies and extracted data independently. RESULTS: Thirteen studies included 569 patients were finally selected, of which eight investigated medically intractable epilepsy. Three publications described temporal tumor-related epilepsy. All included studies were retrospective, and the age of all patients ranged from 1 to 71 years. The duration of epilepsy ranged from 1 month to 30 years. Patients with tumor-related epilepsy underwent surgical treatment with Engel I outcomes ranging from 56.5%-100%. CONCLUSION: Intraoperative ECoG is generally considered a useful technique in delineating epileptogenic areas and improving the prognosis of surgical treatment of tumor-related epilepsy. However, large-scale randomized control trials are still needed to verify these findings and formulate appropriate surgical strategies.

Intraoperative lateral rectus electromyographic recordings optimized by deep intraorbital needle electrodes.

OBJECTIVE: We demonstrate the advantages and safety of long, intraorbitally-placed needle electrodes, compared to standard-length subdermal electrodes, when recording lateral rectus electromyography (EMG) during intracranial surgeries. METHODS: Insulated 25 mm and uninsulated 13 mm needle electrodes, aimed at the lateral rectus muscle, were placed in parallel during 10 intracranial surgeries, examining spontaneous and stimulation-induced EMG activities. Postoperative complications in these patients were reviewed, alongside additional patients who underwent long electrode placement in the lateral rectus. RESULTS: In 40 stimulation-induced recordings from 10 patients, the 25 mm electrodes recorded 6- to 26-fold greater amplitude EMG waveforms than the 13 mm electrodes. The 13 mm electrodes detected greater unwanted volume conduction upon facial nerve stimulation, typically exceeding the amplitude of abducens nerve stimulation. Except for one case with lateral canthus ecchymosis, no clinical or radiographic complications occurred in 36 patients (41 lateral rectus muscles) following needle placement. CONCLUSIONS: Intramuscular recordings from long electrode in the lateral rectus offers more reliable EMG monitoring than 13 mm needles, with excellent discrimination between abducens and facial nerve stimulations, and without significant complications from needle placement. SIGNIFICANCE: Long intramuscular electrode within the orbit for lateral rectus EMG recording is practical and reliable for abducens nerve monitoring.

Continuous Intraoperative Nerve Monitoring in Thyroid Surgery: Can Amplitude Be a Standardized Parameter?

The objective of this study is to evaluate electromyographic waveforms related to vagus monitoring. We collected data from patients undergoing thyroidectomy with CIONM, regardless of vocal cord response amplitude initially measured. We divided data of 193 nerves into three groups, according to initial amplitude value: ≥500 µV (Group 1,110 pt.), between 100 and 500 µV (Group 2, 79 pt.), and <100 µV (Group 3, 4 pt.). ROC curve showed a high diagnostic accuracy of final amplitude absolute value in vocal cord paralysis detection in both groups (89 and 86%). An increase of vocal cord paralysis risk was associated with progressive amplitude reduction (Group 1: OR=1.05, CI=1.02-1.09, p=0.001; Group 2: OR=1.05, CI=1.02-1.08, p=0.002). Cut-off values for amplitude reduction with optimal sensitivity and specificity were -77% in Group 1 and -15% in Group 2. In Group 3 signals showed an amplitude <100 µV for all monitoring, with no loss of a recognizable signal and normal postoperative cordal functionality. The use of a strict amplitude signal cut-off value ≥500 µV could be too restrictive. Also, signal with baseline amplitude <500 µV may be considered equally adequate. Setting the alarm for a reduction of 77% in patients with initial amplitude ≥500 µV and of 15% for those <500 µV could make monitoring safe and an effective aid for surgeons. In conclusion, there are cases in which initial amplitude is lower than that considered as adequate by current literature but with well recognizable and stable EMG waveforms. How those cases should be approached and what should the surgeon's attitude be are a matter of discussion.

Ipsilateral and Simultaneous Comparison of Responses from Acceleromyography- and Electromyography-based Neuromuscular Monitors.

BACKGROUND: The paucity of easy-to-use, reliable objective neuromuscular monitors is an obstacle to universal adoption of routine neuromuscular monitoring. Electromyography (EMG) has been proposed as the optimal neuromuscular monitoring technology since it addresses several acceleromyography limitations. This clinical study compared simultaneous neuromuscular responses recorded from induction of neuromuscular block until recovery using the acceleromyography-based TOF-Watch SX and EMG-based TetraGraph. METHODS: Fifty consenting patients participated. The acceleromyography and EMG devices analyzed simultaneous contractions (acceleromyography) and muscle action potentials (EMG) from the adductor pollicis muscle by synchronization via fiber optic cable link. Bland-Altman analysis described the agreement between devices during distinct phases of neuromuscular block. The primary endpoint was agreement of acceleromyography- and EMG-derived normalized train-of-four ratios greater than or equal to 80%. Secondary endpoints were agreement in the recovery train-of-four ratio range less than 80% and agreement of baseline train-of-four ratios between the devices. RESULTS: Acceleromyography showed normalized train-of-four ratio greater than or equal to 80% earlier than EMG. When acceleromyography showed train-of-four ratio greater than or equal to 80% (n = 2,929), the bias was 1.3 toward acceleromyography (limits of agreement, -14.0 to 16.6). When EMG showed train-of-four ratio greater than or equal to 80% (n = 2,284), the bias was -0.5 toward EMG (-14.7 to 13.6). In the acceleromyography range train-of-four ratio less than 80% (n = 2,802), the bias was 2.1 (-16.1 to 20.2), and in the EMG range train-of-four ratio less than 80% (n = 3,447), it was 2.6 (-14.4 to 19.6). Baseline train-of-four ratios were higher and more variable with acceleromyography than with EMG. CONCLUSIONS: Bias was lower than in previous studies. Limits of agreement were wider than expected because acceleromyography readings varied more than EMG both at baseline and during recovery. The EMG-based monitor had higher precision and greater repeatability than acceleromyography. This difference between monitors was even greater when EMG data were compared to raw (nonnormalized) acceleromyography measurements. The EMG monitor is a better indicator of adequate recovery from neuromuscular block and readiness for safe tracheal extubation than the acceleromyography monitor.

Artificial Intelligence-enabled, Real-time Intraoperative Ultrasound Imaging of Neural Structures Within the Psoas: Validation in a Porcine Spine Model.

STUDY DESIGN: Experimental in-vivo animal study. OBJECTIVE: The aim of this study was to evaluate an Artificial Intelligence (AI)-enabled ultrasound imaging system's ability to detect, segment, classify, and display neural and other structures during trans-psoas spine surgery. SUMMARY OF BACKGROUND DATA: Current methodologies for intraoperatively localizing and visualizing neural structures within the psoas are limited and can impact the safety of lateral lumbar interbody fusion (LLIF). Ultrasound technology, enhanced with AI-derived neural detection algorithms, could prove useful for this task. METHODS: The study was conducted using an in vivo porcine model (50 subjects). Image processing and machine learning algorithms were developed to detect neural and other anatomic structures within and adjacent to the psoas muscle while using an ultrasound imaging system during lateral lumbar spine surgery (SonoVision,™ Tissue Differentiation Intelligence, USA). The imaging system's ability to detect and classify the anatomic structures was assessed with subsequent tissue dissection. Dice coefficients were calculated to quantify the performance of the image segmentation. RESULTS: The AI-trained ultrasound system detected, segmented, classified, and displayed nerve, psoas muscle, and vertebral body surface with high sensitivity and specificity. The mean Dice coefficient score for each tissue type was >80%, indicating that the detected region and ground truth were >80% similar to each other. The mean specificity of nerve detection was 92%; for bone and muscle, it was >95%. The accuracy of nerve detection was >95%. CONCLUSION: This study demonstrates that a combination of AI-derived image processing and machine learning algorithms can be developed to enable real-time ultrasonic detection, segmentation, classification, and display of critical anatomic structures, including neural tissue, during spine surgery. AI-enhanced ultrasound imaging can provide a visual map of important anatomy in and adjacent to the psoas, thereby providing the surgeon with critical information intended to increase the safety of LLIF surgery.Level of Evidence: N/A.

Sensitivity and Negative Predictive Value of Motor Evoked Potentials of the Facial Nerve.

OBJECTIVE: The objective of this study was to determine the performance of the standard alarm criterion of motor evoked potentials (MEPs) of the facial nerve in surgeries performed for resections of vestibular schwannomas or of other lesions of the cerebellopontine angle. METHODS: This retrospective study included 33 patients (16 with vestibular schwannomas and 17 with other lesions) who underwent the resection surgery with transcranial MEPs of the facial nerve. A reproducible 50% decrease in MEP amplitude, resistant to a 10% increase in stimulation intensity, was applied as the alarm criterion during surgery. Facial muscular function was clinically evaluated with the House-Brackmann score (HBS), pre- and postsurgery at 3 months. RESULTS: In the patient group with vestibular schwannoma, postoperatively, the highest sensitivity and negative predictive values were found for a 30% decrease in MEP amplitude, that is, a criterion stricter than the 50% decrease in MEP amplitude criterion, prone to trigger more warnings, used intraoperatively. With this new criterion, the sensitivity would be 88.9% and the negative predictive value would be 85.7%. In the patient group with other lesions of the cerebellopontine angle, the highest sensitivity and negative predictive values were found equally for 50, 60, or 70% decrease in MEP amplitude. With these criteria, the sensitivities and the negative predictive values would be 100.0%. CONCLUSION: Different alarm criteria were found for surgeries for vestibular schwannomas and for other lesions of the cerebellopontine angle. The study consolidates the stricter alarm criterion, that is, a criterion prone to trigger early warnings, as found previously by others for vestibular schwannoma surgeries (30% decrease in MEP amplitude).

Predictive Value of Transcranial Evoked Potential Monitoring for Intramedullary Spinal Cord Tumors.

BACKGROUND: Intraoperative neurophysiologic monitoring (IONM) has increased patient safety and extent of resection in patients with eloquent brain tumors. Despite its comprehensive capability for the resection of intramedullary spinal cord tumors (ISCTs), the application during the resection of these tumors is controversial. METHODS: We retrospectively analyzed the resection of ISCTs in 83 consecutive cases. IONM was performed in all cases. Each patient's motor status and the McCormick scale was determined preoperatively, directly after surgery, at the day of discharge, and at long-term follow-up. RESULTS: IONM was feasible in 71 cases (85.5%). Gross total resection was performed in 75 cases (90.4%). Postoperatively, patients showed new transient deficits in 12 cases (14.5%) and new permanent deficits in 12 cases (14.5%). The mean McCormick variance between baseline and long-term follow-up was - 0.08 ± 0.54. IONM's sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for the patient's motor status at the day of discharge was 75.0%, 64.7%, 45.5%, and 86.8%. It was 88.9%, 59.7%, 24.2%, and 97.4% for the motor outcome at long-term follow-up. Patients experienced postoperative complications in 15 cases (18.1%). CONCLUSION: IONM, as performed in the present study, shows a high sensitivity and NPV but low specificity and PPV, particularly for the patient's motor status at the long-term follow-up. As far as practicable by a retrospective study on IONM, our results confirm IONM's usefulness for its application during the resection of ISCTs. However, these results must be approved by a prospective study.

Reliability of Intraoperative Monitoring in Patients with a Preexisting Motor Deficit: Case Report and Literature Review.

BACKGROUND: The use of intraoperative monitoring (IOM) in glioma surgery is a widely adopted and clinically validated adjunct to define safe zones of resection for the neurosurgeon. However, the role of IOM in cases of a significant preexisting motor deficit is questionable. CASE DESCRIPTION: We describe a case of a 25-year-old with a recurrent presentation of a left paracentral glioblastoma, admitted with intratumoral hemorrhage and subsequent acute severe right-sided weakness. The patient underwent a redo left parietal craniotomy and 5-aminolevulinic acid-guided resection with IOM. The severity of the weakness was not reflected by the pre- and intraoperative cortical motor evoked potentials (MEPs) that were reassuring. The patient's hemiparesis recovered to full power postoperatively. CONCLUSIONS: Preoperative weakness is traditionally accepted as a relative contraindication to IOM and therefore its usefulness is questioned in this context. Our case challenges this assumption. We present the clinical course, review the cranial and spinal literature including the reliability of IOM in cases of preoperative motor deficit, and discuss the need for tailor-made IOM strategies.

Comparison of Ultrasonography and Conventional Fluoroscopy Guided Caudal Epidural Injection in Chronic Low Back Pain.

AIM: To compare the efficacies of fluoroscopy- and ultrasound (US)-guided caudal epidural steroid injections (CESIs) in patients with chronic low back pain (LBP). MATERIAL AND METHODS: This study included patients with chronic LBP who underwent US- (Group U; n = 90) or fluoroscopyguided (Group F; n = 90) CESI. The procedure time, successful injection rate on the first attempt, complication rate, Oswestry Disability Index (ODI) score, and Numeric Rating Scale (NRS) score before CESI and after 3 weeks and 3 months of CESI were analyzed. RESULTS: NRS and ODI scores improved at 3 weeks (p < 0.001) and 3 months (p < 0.001) after CESIs. No significant differences were noted between the two groups for the NRS (p=0.22 and p=0.47) and ODI (p=0.58, p=0.22) scores. Moreover, the CESI procedure time was significantly shorter (p < 0.001) and the successful injection rate on the first attempt was significantly higher (p=0.002) in Group U than in Group F. The complication rate difference was statistically insignificant between the two groups (p > 0.05). CONCLUSION: Outcomes of US-guided CESI were superior than those of fluoroscopy-guided CESI considering the successful injection rate on the first attempt and procedure time. In addition, US-guided CESI was as effective as fluoroscopy-guided CESI and did not expose patients and practitioners to radiation.

Consenso sobre guías de tratamiento de los glioblastomas elaborado por el Grupo de Trabajo de Neurooncología (GTNO) de la SENEC / Glioblastoma treatment guidelines: Consensus by the Spanish Society of Neurosurgery Tumor Section

INTRODUCCIÓN: El tratamiento de los glioblastomas (GMB) comienza en la mayor parte de los pacientes con una cirugía, ya sea para la extirpación tumoral, ya sea para la obtención de tejido con el que determinar un diagnóstico histológico. Con el fin de obtener el máximo beneficio de estos tratamientos cada paciente debe ser valorado de forma individualizada por un equipo multidisciplinar, constituido por aquellas especialidades involucradas tanto en el diagnóstico como en el tratamiento. MATERIAL Y MÉTODOS: El objetivo de este trabajo es elaborar unas recomendaciones de tratamiento para los pacientes con GBM, para lo cual un experto en cada campo ha descrito lo más relevante de dicha área basado tanto en su experiencia como en la literatura. RESULTADOS: Se han desarrollado los distintos apartados sobre el tratamiento de los GBM y al final de cada apartado se concluye la recomendación del GTNO. CONCLUSIONES: A pesar de que los GBM son tumores agresivos y el pronóstico es malo, los pacientes se pueden beneficiar de tratamientos que mejoren no solo la supervivencia global sino también la calidad de vida. El neurocirujano debe conocer las distintas opciones de tratamientos, sus indicaciones y riesgos para poder participar activamente en la toma de decisiones y ofrecer un tratamiento neuroquirúrgico oportuno a cada situación

INTRODUCTION: Glioblastoma (GBM) treatment starts in most patients with surgery, either resection surgery or biopsy, to reach a histology diagnose. Multidisciplinar team, including specialists in brain tumors diagnose and treatment, must make an individualize assessment to get the maximum benefit of the available treatments. MATERIAL AND METHODS: Experts in each GBM treatment field have briefly described it based in their experience and the reviewed of the literature. RESULTS: Each area has been summarized and the consensus of the brain tumor group has been included at the end. CONCLUSIONS: GBM are aggressive tumors with a dismal prognosis, however accurate treatments can improve overall survival and quality of life. Neurosurgeons must know treatment options, indications and risks to participate actively in the decision making and to offer the best surgical treatment in every case

Optimizing pre-, intra-, and postoperative management of patients with sellar pathology undergoing transsphenoidal surgery.

OBJECTIVE: Perioperative management of patients with sellar lesions is complex, requiring input from a multidisciplinary team of specialists for ongoing management of both endocrinological and neurosurgical issues. Here, the authors reviewed the experience of a single multidisciplinary center over 10 years to identify key postoperative practices that ensure positive outcomes for patients with sellar lesions who undergo transsphenoidal surgery. METHODS: The authors performed a retrospective review of all transsphenoidal operations carried out by the senior author at a single center from April 2008 through November 2018. They included only adult patients and recorded perioperative management. They also reviewed the evolution of clinical practices for perioperative care at their institution to identify strategies for ensuring positive patient outcomes, and they reviewed the literature on select related topics. RESULTS: In total, 1023 operations in 928 patients were reviewed. Of these, 712 operations were for pituitary adenomas (69.6%), and 122 were for Rathke cleft cysts (11.9%). The remainder included operations for craniopharyngiomas (3.6%), arachnoid cysts (1.7%), pituitary tumor apoplexy (1.0%), and other sellar pathologies (12.2%). Among the reviewed operations, the median hospital stay was 3 days (IQR 2-3). Patient management details during the pre-, intra-, and postoperative periods were identified, including both shared characteristics of all patients undergoing transsphenoidal surgery and unique characteristics that are specific to certain lesion types or patient populations. CONCLUSIONS: Patients with sellar lesions who undergo transsphenoidal surgery require complex, multidisciplinary perioperative care to monitor for common adverse events and to improve outcomes, but there is a dearth of high-quality evidence guiding most perioperative practices. Here, the authors reviewed practices at their institution across more than 1000 transsphenoidal operations that may help ensure successful patient outcomes.

Neuroanesthesia Guidelines for Optimizing Transcranial Motor Evoked Potential Neuromonitoring During Deformity and Complex Spinal Surgery: A Delphi Consensus Study.

STUDY DESIGN: Expert opinion-modified Delphi study. OBJECTIVE: We used a modified Delphi approach to obtain consensus among leading spinal deformity surgeons and their neuroanesthesiology teams regarding optimal practices for obtaining reliable motor evoked potential (MEP) signals. SUMMARY OF BACKGROUND DATA: Intraoperative neurophysiological monitoring of transcranial MEPs provides the best method for assessing spinal cord integrity during complex spinal surgeries. MEPs are affected by pharmacological and physiological parameters. It is the responsibility of the spine surgeon and neuroanesthesia team to understand how they can best maintain high-quality MEP signals throughout surgery. Nevertheless, varying approaches to neuroanesthesia are seen in clinical practice. METHODS: We identified 19 international expert spinal deformity treatment teams. A modified Delphi process with two rounds of surveying was performed. Greater than 50% agreement on the final statements was considered "agreement"; >75% agreement was considered "consensus." RESULTS: Anesthesia regimens and protocols were obtained from the expert centers. There was a large amount of variability among centers. Two rounds of consensus surveying were performed, and all centers participated in both rounds of surveying. Consensus was obtained for 12 of 15 statements, and majority agreement was obtained for two of the remaining statements. Total intravenous anesthesia was identified as the preferred method of maintenance, with few centers allowing for low mean alveolar concentration of inhaled anesthetic. Most centers advocated for <150 µg/kg/min of propofol with titration to the lowest dose that maintains appropriate anesthesia depth based on awareness monitoring. Use of adjuvant intravenous anesthetics, including ketamine, low-dose dexmedetomidine, and lidocaine, may help to reduce propofol requirements without negatively effecting MEP signals. CONCLUSION: Spine surgeons and neuroanesthesia teams should be familiar with methods for optimizing MEPs during deformity and complex spinal cases. Although variability in practices exists, there is consensus among international spinal deformity treatment centers regarding best practices. LEVEL OF EVIDENCE: 5.

Diagnostic accuracy of various EEG changes during carotid endarterectomy to detect 30-day perioperative stroke: A systematic review.

OBJECTIVES: We assessed whether significant intraoperative electroencephalography (EEG) changes have predictive value for perioperative stroke within 30 days after carotid endarterectomy (CEA) procedures for carotid stenosis (CS) patients. We also assessed the diagnostic accuracy of various EEG changes in predicting perioperative stroke. METHODS: We searched databases for reports with outcomes of CS patients who underwent CEA with intraoperative EEG monitoring. We calculated the sensitivity, specificity, and diagnostic odds ratio (DOR) of EEG changes for predicting perioperative stroke. Sensitivity and specificity were presented with forest plots and a summary receiver operating characteristic (ROC) curve. RESULTS: The meta-analysis included 10,672 patients. Intraoperative EEG changes predicted 30-day stroke with a sensitivity of 46% (95% CI, 38-54%) and specificity of 86% (95% CI, 83-88%). The estimated DOR was 5.79 (95% CI, 3.86-8.69). The estimated DOR for reversible and irreversible EEG changes were 8.25 (95% CI, 3.34-20.34) and 70.84 (95% CI, 36.01-139.37), respectively. CONCLUSION: Intraoperative EEG changes have high specificity but modest sensitivity for predicting perioperative stroke following CEA. Patients with irreversible EEG changes are at high risk for perioperative stroke. SIGNIFICANCE: Intraoperative EEG changes can help surgeons predict the risk of perioperative stroke for CS patients following CEA.

Neurophysiological monitoring of spinal cord function during spinal deformity surgery: 2020 SRS neuromonitoring information statement.

The Scoliosis Research Society has developed an updated information statement on intraoperative neurophysiological monitoring of spinal cord function during spinal deformity surgery. The statement reviews the risks of spinal cord compromise associated with spinal deformity surgery; the statement then discusses the various modalities that are available to monitor the spinal cord, including somatosensory-evoked potentials, motor-evoked potentials, and electromyographic (EMG) options. Anesthesia considerations, the importance of a thoughtful team approach to successful monitoring, and the utility of checklists are also discussed. Finally, the statement expresses the opinion that utilization of intraoperative neurophysiological spinal cord monitoring in spinal deformity surgery is the standard of care when the spinal cord is at risk.

Thalamic Deep Brain Stimulation for tremor: The critical role of intraoperative testing.

INTRODUCTION: Optimal placement of Deep Brain Stimulation (DBS) lead is critical to ensure an adequate therapeutic benefit and minimize stimulation-induced side effects. METHODS: We reviewed data from 2004 to 2018 of all cases of essential tremor treated with thalamic DBS at the University of Cincinnati. All procedures were performed with the patient awake. Change in parallel trajectory was classified as major repositioning, whereas a change in depth of electrode classified as minor repositioning. The following data were compared between groups (no vs. minor vs. major repositioning): age at surgery, sex, AC-PC length, third ventricle width, cerebral atrophy, small vessel disease burden, and intraoperative tremor control. Univariate and multivariate analyses were conducted to identify factors associated with intraoperative repositioning. RESULTS: Of the 127 encounters with essential tremor, 71 required repositioning (33 major and 38 minor). Comparing procedures with major, minor, and no repositioning, mean number of changes per procedure (4 vs. 1.2 vs 0; p < 0.001) and AC-PC length (26 vs. 27 vs. 27.2 mm; p = 0.021) differed between the three groups. Older age at surgery (OR 1.04, p = 0.042), left side (OR 2.56, p = 0.04) and decrease in AC-PC length (OR 1.33, p = 0.026) were associated with greater odds of any (minor or major) repositioning. A decrease in AC-PC length was associated with greater odds of major repositioning (OR 1.37, p = 0.009). CONCLUSION: Intraoperative functional testing may be critical to ensure the accuracy of thalamic DBS targeting based on neuroimaging data, particularly in patients with reduced AC-PC length.

Use of the train-of-five bipolar technique to provide reliable, spatially accurate motor cortex identification in asleep patients.

OBJECTIVE: Intraoperative cortical and subcortical mapping techniques have become integral for achieving a maximal safe resection of tumors that are in or near regions of eloquent brain. The recent literature has demonstrated successful motor/language mapping with lower rates of stimulation-induced seizures when using monopolar high-frequency stimulation compared to traditional low-frequency bipolar stimulation mapping. However, monopolar stimulation carries with it disadvantages that include more radiant spread of electrical stimulation and a theoretically higher potential for tissue damage. The authors report on the successful use of bipolar stimulation with a high-frequency train-of-five (TOF) pulse physiology for motor mapping. METHODS: Between 2018 and 2019, 13 patients underwent motor mapping with phase-reversal and both low-frequency and high-frequency bipolar stimulation. A retrospective chart review was conducted to determine the success rate of motor mapping and to acquire intraoperative details. RESULTS: Thirteen patients underwent both high- and low-frequency bipolar motor mapping to aid in tumor resection. Of the lesions treated, 69% were gliomas, and the remainder were metastases. The motor cortex was identified at a significantly greater rate when using high-frequency TOF bipolar stimulation (n = 13) compared to the low-frequency bipolar stimulation (n = 4) (100% vs 31%, respectively; p = 0.0005). Intraoperative seizures and afterdischarges occurred only in the group of patients who underwent low-frequency bipolar stimulation, and none occurred in the TOF group (31% vs 0%, respectively; p = 0.09). CONCLUSIONS: Using a bipolar wand with high-frequency TOF stimulation, the authors achieved a significantly higher rate of successful motor mapping and a low rate of intraoperative seizure compared to traditional low-frequency bipolar stimulation. This preliminary study suggests that high-frequency TOF stimulation provides a reliable additional tool for motor cortex identification in asleep patients.