Precise Electrode Placement Research Articles

Treating Treatment-Resistant Obsessive-Compulsive Disorder (OCD) via Deep Brain Stimulation (DBS)

Obsessive-Compulsive Disorder (OCD) is a prevalent and challenging mental health condition characterized by persistent, unwanted thoughts (obsessions) and repetitive behaviors (compulsions). Traditional treatment modalities, including pharmacotherapy and cognitive-behavioral therapies, fail to alleviate symptoms in around half of the patients, necessitating the exploration of alternative therapeutic options. Deep Brain Stimulation (DBS) has emerged as a promising intervention for treatment-resistant OCD, with recent studies reporting a success rate of about 60%. This innovative treatment involves the precise placement of electrodes in specific brain regions such as the Nucleus Accumbens (NAcc), Bed Nucleus of the Stria Terminalis (BNST), and Subthalamic Nucleus (STN) to modulate dysfunctional neural circuits. This paper reviews the effectiveness of DBS in reducing OCD symptoms, evaluates its safety, and discusses the neurobiological mechanisms underlying its therapeutic effects. It also explores future research directions, including the optimization of electrode placement, the integration of DBS with other treatment modalities, and the development of personalized medicine approaches. Furthermore, the paper addresses ongoing challenges such as the need for a clearer understanding of DBS mechanisms, the refinement of patient selection criteria, and the management of long-term outcomes. By providing a comprehensive overview of current knowledge and potential developments, this study aims to highlight the role of DBS as a transformative tool for managing severe, refractory OCD.

Application of Augmented Reality for Accurate Punctures During Stage 1 Sacral Neuromodulation.

Precise electrode placement is crucial for the success of sacral neuromodulation (SNM). The aim of this study was to explore a more accurate and convenient method for positioning punctures during the first stage of SNM. This retrospective study compared preoperative baseline values, intraoperative indicators, postoperative scores, and other clinical data from 130 patients who underwent SNM electrode implantation at our department between 2018 and 2023. The patients were divided into an experimental group and a control group to assess the advantages and feasibility of augmented reality (AR)-guided sacral nerve electrode implantation. The experimental group experienced fewer intraoperative puncture attempts and achieved more accurate AR-guided localization punctures. Additionally, there were more responsive electrode contact points (2.74±0.51 vs. 2.46±0.74) and a lower initial voltage postimplantation (1.09±0.39 V vs. 1.69±0.43 V). The number of intraoperative x-ray fluoroscopies was significantly lower in the experimental group than in the control group (5.94±1.46 vs. 9.22±1.93), leading to a shorter overall operation time (61.32±11.27 minutes vs. 83.49±15.84 minutes). Furthermore, there was no need for additional local anesthetic drugs during the surgery in the experimental group. Comparative observations revealed no significant differences in intraoperative blood loss or the sacral hole location for electrode implantation between the 2 groups. Although the incidence of wound infection and the rate of permanent implantation in stage 2 were similar in both groups, the pain score on the first day postoperation was significantly lower in the experimental group than in the control group (2.62±0.697 vs. 2.83±0.816). AR-guided sacral nerve modulation implantation can reduce both the number of punctures and the duration of the operation while ensuring safety and effectiveness. This technique can enhance the contact points of the response electrode, effectively lower the initial response voltage, and stabilize the electrode.

Electrical stimulation of the vestibular nerve: evaluating effects and potential starting points for optimization in vestibular implants.

Oscillopsia and unsteadiness are common and highly debilitating symptoms in individuals with bilateral vestibulopathy. A lack of adequate treatment options encouraged the investigation of vestibular implants, which aim to restore vestibular function with motion-modulated electrical stimulation. This review aims to outline the ocular and postural responses that can be evoked with electrical prosthetic stimulation of the semicircular canals and discuss potential approaches to further optimize evoked responses. Particular focus is given to the stimulation paradigm. Feasibility studies in animals paved the way for vestibular implantation in human patients with bilateral vestibulopathy. Recent human trials demonstrated prosthetic electrical stimulation to partially restore vestibular reflexes, enhance dynamic visual acuity, and generate controlled postural responses. To further optimize prosthetic performance, studies predominantly targeted eye responses elicited by the vestibulo-ocular reflex, aiming to minimize misalignments and asymmetries while maximizing the response. Changes of stimulation parameters are shown to hold promise to increase prosthetic efficacy, together with surgical refinements and neuroplastic effects. Optimization of the stimulation paradigm, in combination with a more precise electrode placement, holds great potential to enhance the clinical benefit of vestibular implants.

Asleep surgery for deep brain stimulation of the globus pallidus internus in pediatric dystonia associated with KMT2B mutation

Abstract Pediatric dystonia refers to the onset of dystonia before the age of 21 years. Accurate diagnosis through genetic testing and precise electrode placement may significantly improve motor symptoms and quality of life of patients with gene-associated dystonia. This report presents a rare KMT2B-related dystonia case managed with bilateral pallidal deep brain stimulation (DBS) in an 8-year-old girl. The patient presented with muscle contractions on the distal parts of the lower limbs, speech impairment, and myoclonic jerking movements. Genomic sequencing identified a heterozygous mutation in the KMT2B gene (617284 on chromosome 19p13). In this case, DBS of the globus pallidus internus was performed under general anesthesia. Six months post-surgery, the Burke–Fahn–Marsden scale scores indicated a 46% improvement, and the scores for the Unified Dystonia Rating Scale and Global Dystonia Severity Rating Scale showed 50% and 28% improvements, respectively. Accurate diagnosis of KMT2B-related dystonia holds significant value in terms of guiding appropriate treatment as the disease is responsive to DBS surgery targeting the globus pallidus internus. This case illustrates the benefits of DBS in pediatric patients and its role in advancing surgical interventions for dystonia.

Subthalamic deep brain stimulation in advanced Parkinson’s disease using the STarFix system

BackgroundDeep brain stimulation (DBS) is a well-established and highly effective treatment for patients with medically uncontrolled Parkinson’s disease (PD). This study presents the outcome of patients with PD after subthalamic deep brain stimulation (STN DBS) using the microtargeting the platform (MTP) stereotactic system (the STarFixSystem, FHC Inc., Bowdoin, Me., USA) for accurate localization of the target and precise placement of DBs electrodes. Patients were evaluated preoperatively and the follow up period was 1 year utilizing the Unified Parkinson’s Disease Rating Scale (UPDRS II and III) in on and off medication-stimulation conditions. It included 18 STN DBS procedures in 10 patients over a 2-year period. The technical features and the practical application of the STarFix system and the clinical outcome are reported. Also lead location analysis is done by doing postoperative CT to evaluate the clinical accuracy of the stereotactic system.ResultsThe mean age of PD patients was 67.7 years. Six patients were males (60%) and 4 patients were females (40%). The mean postoperative improvement in ADL was 83.47 ± 2.39 over Dopa therapy alone. The mean postoperative improvement in UPDRs motor score was 78.96 ± 7.74 over Dopa therapy alone. The STarFix system showed high accuracy with target error 1.89 mm (SD 0.8) without accounting for brain shift.ConclusionDeep brain stimulation (DBS) targeting the subthalamic nucleus (STN) offers fundamental benefits for patients with advanced Parkinson’s disease (PD). The usage of the STarFix system for implanting DBS electrodes in the STN provides an accurate, safe, and effective alternative to traditional stereotactic techniques. This approach simplifies the surgical procedure, boosts patient comfort, and minimizes the duration of the operation.Clinical trial registration ClinicalTrials.gov identifier: NCT03562403. Registered 19 June 2018, https://classic.clinicaltrials.gov/ct2/show/NCT03562403.

Deep brain stimulation of the subthalamic nucleus for primary Meige syndrome: clinical outcomes and predictive factors.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has demonstrated efficacy against multiple types of dystonia, but only a few case reports and small-sample studies have investigated the clinical utility of STN-DBS for Meige syndrome, a rare but distressing form of craniofacial dystonia. Furthermore, the effects of DBS on critical neuropsychological sequelae, such as depression and anxiety, are rarely examined. In this study, the authors investigated the therapeutic efficacy of STN-DBS for both motor and psychiatric symptoms of Meige syndrome. The authors retrospectively reviewed consecutive patients with Meige syndrome receiving bilateral STN-DBS at their institution from January 2016 to June 2023. Motor performance and nonmotor features including mood, cognitive function, and quality of life (QOL) were evaluated using standardized rating scales at baseline and at final postoperative follow-up. Clinical and demographic factors influencing postoperative motor outcome were evaluated by uni- and multivariable linear regression models. Fifty-one patients were ultimately included, with a mean ± SD follow-up duration of 27.3 ± 18.0 months. The mean Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) movement score improved from 12.9 ± 5.2 before surgery to 5.3 ± 4.2 at the last follow-up (mean improvement 58.9%, p < 0.001) and the mean BFMDRS disability score improved from 5.6 ± 3.3 to 2.9 ± 2.9 (mean improvement 44.6%, p < 0.001). Hamilton Depression and Anxiety Rating Scale scores also improved by 35.3% and 34.2%, respectively, and the postoperative 36-item Short-Form Health Survey score indicated substantial QOL enhancement. Global cognition remained stable after treatment. Multiple linear regression analysis identified disease duration (β = -0.241, p = 0.027), preoperative anxiety severity (β = -0.386, p = 0.001), and volume of activated tissue within the dorsolateral (sensorimotor) STN (β = 0.483, p < 0.001) as independent predictors of motor outcome. These findings support STN-DBS as an effective and promising therapy for both motor and nonmotor symptoms of Meige syndrome. Timely diagnosis, treatment of preoperative anxiety, and precise electrode placement within the dorsolateral STN are essential for optimal clinical outcome.

Temporal evolution of His bundle pacing thresholds: a sub-study of the PACE-CONDUCT trial

Abstract Background His bundle pacing (HBP) has become a valuable alternative for cardiac resynchronization therapy, offering physiological pacing. This substudy of the PACE-CONDUCT trial aimed to explore the influence selective and non-selective HBP on threshold height. We assessed these parameters in patients with both normal conduction and bundle branch block conduction. Methods Our study included 61 consecutive patients with a median age of 73 years, who underwent a successful HBP implantation for indications such as sick sinus syndrome, AV Block 2 type 2, binodal disease, and ablate and pace therapy prior to AV-node ablation. Among these patients, 18 exhibited QRS durations exceeding 150 ms, indicating a complete and broad bundle branch block which made them candidates for cardiac resynchronization therapy (CRT). All patients received HBP implantation with the assistance of a 3D electroanatomical system. This system allowed for low-fluoroscopic, atraumatic evaluation of the His bundle (HB) area, presenting the His voltage as a color-coded map for precise electrode placement. Results The feasibility of bundle branch correction is generally accepted in selective HBP distal to the site of block, albeit associated with higher threshold values and potentially lower battery duration. Our analysis encompassed 61 patients who underwent HBP implantation, with 23 patients (37,7%) exhibiting selective HBP and 38 (62,3%) non-selective HBP. Remarkably, 10 out of the 23 patients with selective HBP demonstrated a complete bundle branch block correction after HBP implantation even with a basal QRS durations exceeding 150 ms. We evaluated HBP thresholds at implantation, one day post-implantation, and one month post-implantation, correlating these data with selective and non-selective HBP. Threshold values were converted to volts per millisecond (volts × milliseconds) for analysis. Statistical analysis conducted with IBM SPSS 29.0 revealed a significant difference at the day of implantation, indicating higher threshold capture in selective HBP compared to non-selective HBP (one-sided p-value: &amp;lt; 0.01, two sided p value 0.01). However, this difference could not be sustained at the one-day and one-month threshold follow-ups, suggesting normalization of the selective HBP threshold. Conclusion In our study, the initially higher threshold in selective HBP normalized within 24 hours compared to non-selective HBP. Additionally, our study demonstrated the feasibility of selective His pacing in patients with complete bundle branch block and broad QRS durations. These findings provide insights into HBP optimization and encourage further investigations with larger patient cohorts to validate our observations and enhance patient care in the realm of cardiac pacing.Threshold trend

Investigation on self-rectifying properties of Pt/HfO2/Ti with rivet-like structure based on ALD conformal technology

This work explores an architecture for nonvolatile resistive random-access memory (RRAM) systems. The study proposes a self-rectifying RRAM device utilizing a two-terminal 1R selector that harmonizes the gate control efficacy of transistors with the inherent simplicity of diode structures. A rivet-like HfO2-based RRAM array is meticulously constructed through atomic layer deposition (ALD), aiming to enhance device performance and retention stability. The conformal fabrication technique of ALD method is critical in achieving uniform coverage of isolation layers and precise electrode placement, which is instrumental in the fabrication of high-performance memory cells. Empirical analyses indicate significant improvements in rectification and ON/OFF ratios compared to existing RRAM models, bolstered by compatibility with established CMOS processes. It reveals that these advances are conducive to scalable, high-density memory integration, positioning the RRAM as a viable contender for future computational applications that require high efficiency and neuromorphic computing capabilities.

Evaluation of an impedance-based method to monitor the insertion of the electrode array during cochlear implantation

PurposeCochlear implantation is a prevalent remedy for severe-to-profound hearing loss. Optimising outcomes and hearing preservation, and minimising insertion trauma, require precise electrode placement. Objective monitoring during the insertion process can provide valuable insights and enhance surgical precision. This study assesses the feasibility and performance of an impedance-based method for monitoring electrode insertion, compared to the surgeon’s feedback.MethodsThe study utilised the Insertion Monitoring Tool (IMT) research software, allowing for real-time measurement of impedance and evoked compound action potential (eCAP) during electrode insertion in 20 patient implantations. This enabled an impedance-based method to continuously assess the status of each electrode during the insertion process. The feasibility and performance was evaluated and compared to the surgeon’s feedback approach. eCAP measurements focused merely on feasibility without searching specific responses.ResultsThe IMT demonstrated feasibility in measuring real-time impedances and eCAP during the insertion of the electrode array. The impedance-based method exhibited potential for accurately monitoring the insertion depth with a high success rate. However, further development is needed to improve the number of usable contacts.ConclusionsObjective monitoring with the impedance-based method shows promise as a valuable tool to enhance the precision of cochlear implant electrode insertion respecting insertion distance estimation. The IMT research software proved feasible in recording real-time impedances and eCAP during electrode insertion. While this impedance-based method exhibits high success rates, further improvements are required to optimise the number of usable contacts. This study highlights the potential of objective monitoring techniques to enhance cochlear implantation outcomes.

Robotic-Assisted Stereoelectroencephalography: A Systematic Review and Meta-Analysis of Safety, Outcomes, and Precision in Refractory Epilepsy Patients.

Robotic assistance in stereoelectroencephalography (SEEG) holds promising potential for enhancing accuracy, efficiency, and safety during electrode placement and surgical procedures. This systematic review and meta-analysis, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and International Prospective Register of Systematic Reviews (PROSPERO) registration, delves into the latest advancements and implications of robotic systems in SEEG, while meticulously evaluating outcomes and safety measures. Among 855 patients suffering from medication-refractory epilepsy who underwent SEEG in 29 studies, averaging 24.6 years in age, the most prevalent robots employed were robotic surgical assistant (ROSA) (450 patients), Neuromate (207), Sinovation (140), and ISys1 (58). A total of 8,184 electrodes were successfully implanted, with an average operative time of 157.2 minutes per procedure and 15.1 minutes per electrode, resulting in an overall mean operative time of 157.7 minutes across all studies. Notably, the mean target point error (TPE) stood at 2.13 mm, the mean entry point error (EPE) at 1.48 mm, and postoperative complications occurred in 7.69% of robotically assisted (RA) SEEG cases (60), with 85% of these complications being asymptomatic. This comprehensive analysis underscores the safety and efficacy of RA-SEEG in patients with medication-refractory epilepsy, characterized by low complication rates, reduced operative time, and precise electrode placement, supporting its widespread adoption in clinical practice, with no discernible differences noted among the various robotic systems.

Spatially selective stimulation of the pig vagus nerve to modulate target effect versus side effect

Electrical stimulation of the cervical vagus nerve using implanted electrodes (VNS) is FDA-approved for the treatment of drug-resistant epilepsy, treatment-resistant depression, and most recently, chronic ischemic stroke rehabilitation. However, VNS is critically limited by the unwanted stimulation of nearby neck muscles—a result of non-specific stimulation activating motor nerve fibers within the vagus. Prior studies suggested that precise placement of small epineural electrodes can modify VNS therapeutic effects, such as cardiac responses. However, it remains unclear if placement can alter the balance between intended effect and limiting side effect. We used an FDA investigational device exemption approved six-contact epineural cuff to deliver VNS in pigs and quantified how epineural electrode location impacts on- and off-target VNS activation. Detailed post-mortem histology was conducted to understand how the underlying neuroanatomy impacts observed functional responses. Here we report the discovery and characterization of clear neuroanatomy-dependent differences in threshold and saturation for responses related to both effect (change in heart rate) and side effect (neck muscle contractions). The histological and electrophysiological data were used to develop and validate subject-specific computation models of VNS, creating a well-grounded quantitative framework to optimize electrode location-specific activation of nerve fibers governing intended effect versus unwanted side effect.

Deep Brain Stimulation Surgery Using a Mobile Intraoperative CT Scanner.

IntroductionDeep brain stimulation (DBS) is widely used for the treatment of movement disorders. Precise placement of electrodes is critical for treatment success. The aim of this study was to analyze the accuracy of the intraoperative computer tomography (CT) images compared to that of a traditional fixed CT for patients undergoing DBS procedures.MethodsWe retrospectively analyzed the charts from 30 patients who underwent DBS. In group 1, 10 patients underwent electrode implantation surgery using a fixed CT scanner for pre- and post-operative (OP) images. In group 2, 20 patients underwent surgery using an intraoperative CT scanner for pre- and post-operative images, as well as a fixed CT scanner for post-operative images. We compared the average pre-operative localizer box registration error acquired in these two groups. We also analyzed, in group 2, the final electrode position given on each post-operative CT images. We compared the average Euclidean distances between each set of cartesian coordinates to assess target accuracy between both scanning methodologies.ResultsThirty patients had ages ranging from 40 to 88 years, with a median of 69 years old. In the 20 patients who utilized an intraoperative CT scanner pre-operatively in group 2, the mean error, given by the Medtronic software (Medtronic Minimally Invasive Therapies, Minneapolis, MN) with the Leksell frame on, was 0.37. For the 10 pre-operative scans with the stealth fixed CT scanner in group 1, the mean error was 0.44 (p = 0.13). In group 2, the average of the 20 Euclidean distances for each target, in those 20 patients who had post-operative images with both scanners, was 0.36.ConclusionWe concluded that the accuracy of the intraoperative CT scanner is comparable to the gold standard fixed CT scanner for DBS electrode planning and placement, as well as for positioning confirmation after the electrodes are in place.

Recording Gap Junction Current from Xenopus Oocytes.

Heterologous expression of connexins and innexins in Xenopus oocytes is a powerful approach for studying the biophysical properties of gap junctions (GJs). However, this approach is technically challenging because it requires a differential voltage clamp of two opposed oocytes sharing a common ground. Although a small number of labs have succeeded in performing this technique, essentially all of them have used either homemade amplifiers or commercial amplifiers that were designed for single-oocyte recordings. It is often challenging for other labs to implement this technique. Although a high side current measuring mode has been incorporated into a commercial amplifier for dual oocyte voltage-clamp recordings, there had been no report for its application until our recent study. We have made the high side current measuring approach more practical and convenient by introducing several technical modifications, including the construction of a magnetically based recording platform that allows precise placement of oocytes and various electrodes, use of the bath solution as a conductor in voltage differential electrodes, adoption of a commercial low-leakage KCl electrode as the reference electrode, fabrication of current and voltage electrodes from thin-wall glass capillaries, and positioning of all the electrodes using magnetically based devices. The method described here allows convenient and robust recordings of junctional current (Ij) between two opposed Xenopus oocytes.

Adapting the listening time for micro-electrode recordings in deep brain stimulation interventions.

Deep brain stimulation (DBS) is a common treatment for a variety of neurological disorders which involves the precise placement of electrodes at particular subcortical locations such as the subthalamic nucleus. This placement is often guided by auditory analysis of micro-electrode recordings (MERs) which informs the clinical team as to the anatomic region in which the electrode is currently positioned. Recent automation attempts have lacked flexibility in terms of the amount of signal recorded, not allowing them to collect more signal when higher certainty is needed or less when the anatomy is unambiguous. We have addressed this problem by evaluating a simple algorithm that allows for MER signal collection to terminate once the underlying model has sufficient confidence. We have parameterized this approach and explored its performance using three underlying models composed of one neural network and two Bayesian extensions of said network. We have shown that one particular configuration, a Bayesian model of the underlying network's certainty, outperforms the others and is relatively insensitive to parameterization. Further investigation shows that this model also allows for signals to be classified earlier without increasing the error rate. We have presented a simple algorithm that records the confidence of an underlying neural network, thus allowing for MER data collection to be terminated early when sufficient confidence is reached. This has the potential to improve the efficiency of DBS electrode implantation by reducing the time required to identify anatomical structures using MERs.

Novel intraoperative online functional mapping of somatosensory finger representations for targeted stimulating electrode placement: technical note.

Defining eloquent cortex intraoperatively, traditionally performed by neurosurgeons to preserve patient function, can now help target electrode implantation for restoring function. Brain-machine interfaces (BMIs) have the potential to restore upper-limb motor control to paralyzed patients but require accurate placement of recording and stimulating electrodes to enable functional control of a prosthetic limb. Beyond motor decoding from recording arrays, precise placement of stimulating electrodes in cortical areas associated with finger and fingertip sensations allows for the delivery of sensory feedback that could improve dexterous control of prosthetic hands. In this study, the authors demonstrated the use of a novel intraoperative online functional mapping (OFM) technique with high-density electrocorticography to localize finger representations in human primary somatosensory cortex. In conjunction with traditional pre- and intraoperative targeting approaches, this technique enabled accurate implantation of stimulating microelectrodes, which was confirmed by postimplantation intracortical stimulation of finger and fingertip sensations. This work demonstrates the utility of intraoperative OFM and will inform future studies of closed-loop BMIs in humans.

Pneumocephalus in subthalamic deep brain stimulation for Parkinson's disease: a comparison of two different surgical techniques considering factors conditioning brain shift and target precision.

Precise placement of electrodes in deep brain stimulation (DBS) may be influenced by brain shift caused by cerebrospinal fluid leaking or air inflow. We compared accuracy and treatment outcomes between a standard technique and one aiming at reducing brain shift. We retrospectively reviewed 46 patients (92 targets) treated with bilateral subthalamic-DBS for Parkinson's disease. The patients were divided into two groups: group A surgery was performed in supine position with standard burr hole, dural opening, fibrin glue and gelfoam plugging. Group B patients were operated in a semi-sitting position with direct dural puncture to reduce CSF loss. We analysed target deviation on head CT performed immediately after surgery and at 1 month merged with preoperative MRI planning. We recorded pneumocephalus volume, brain atrophy and target correction by intraoperative neurophysiology (ION). In group A, the mean pneumocephalus volume was 10.55 cm3, mean brain volume 1116 cm3, mean target deviation 1.09 mm and ION corrected 70% of targets. In group B, mean pneumocephalus was 7.60 cm3 (p = 0.3048), mean brain volume 1132 cm3 (p = 0.6526), mean target deviation 0.64 mm (p = 0.0074) and ION corrected 50% of targets (p = 0.4886). Most leads' deviations realigned to the planned target after pneumocephalus reabsorbtion suggesting a deviation caused by displacement of anatomical structures due to brain shift. Definitive lead position was always decided with ION. The modified DBS technique significantly reduced errors of electrode placement, though such difference was clinically irrelevant. ION corrected a high amount of trajectories in both groups (70% vs 50%). The choice of either strategy is acceptable.

A Novel 3D-Printed Multi-Drive System for Synchronous Electrophysiological Recording in Multiple Brain Regions.

Extracellular electrophysiology has been widely applied in neural network studies. Local field potentials and single-unit activities can be recorded with high-density electrodes, which facilitate the decoding of neural codes. However, the chronic multi-regional recording is still a challenging task for achieving high placement accuracy and long-term stability. Here, we present a novel electrode design with low-cost 3D-printed parts and custom printed circuits boards. This new design could facilitate precise electrode placement in multiple brain regions simultaneously and reduce the working time for surgical procedures as well. In this paper, the design and fabrication of the 3D printed multi-channel microdrive are explained in detail. We also show the result of high-quality electrophysiological recordings in eight pain-related areas from rats and the electrode placement accuracy. This novel 3D-printed multi-drive system could achieve synchronous electrophysiological recording in multiple brain regions and facilitate future neural network research.

Videolaryngoscope-Aided Electrode Placement for Lower Cranial Nerve Monitoring in a Child with Tonsillar Enlargement

AbstractIntraoperative neuromonitoring for tumor resection near brain stem consists of monitoring the lower cranial nerves (CNs) and motor evoked potentials to check for integrity of CN and corticospinal pathway. Usually CN mapping of CN VII (orbicularis oris/oculi and frontalis bilaterally), CN IX, CN X (posterior pharyngeal wall and soft palate bilaterally, vocal cords), CN XI (sternomastoid bilaterally), and CN XII (tongue bilaterally) is done. An intraoral pathology such as tonsillar enlargement especially in pediatric patients can pose a challenge to placement of the electrodes for CN monitoring. Videolaryngoscope will aid in better visualization and safe and precise placement of electrodes in the posterior pharyngeal wall, soft palate, vocal cords, and tongue. Thus, integration of different technologies aims to provide a safer and scientifically sound anesthetic technique and improves the outcome even in challenging situations.

Precision implantation with positional confirmation of fine-wire EMG electrodes in the deep posterior neck muscles

Precise electrode placement is essential for obtaining useful electromyographic (EMG) recordings. Our aim was to develop a protocol for computerized-tomography (CT) guided fine-wire (FW) electrode placement that permits confirmation of the final electrode position in the deep posterior cervical multifidus (CM). FW-EMG electrodes were custom-made from three 50-µm diameter Teflon-insulated platinum/iridium wires. The electrodes were inserted bilaterally in the CM in 15 healthy adult subjects through a 45-mm cannula under CT guidance. The final position of the electrode placement was confirmed in reconstructed 2D and 3D images. Electrode placement was within the fascial boundaries of the CM for 21 of the 25 successfully inserted FW-EMG electrodes. The distance from the electrode to the middle of the CM did not increase significantly with target depth until a breakpoint at 63.2 mm (95%CI 59.1–65.3), from where it increased by an additional 2.9 mm per mm increase in target depth (95%CI 1.3–6.6). Viable EMG was obtained from 21 electrodes. CT guided implantation provided excellent visual documentation in three dimensions of the final placement of the tip of the electrode bundle. The technique affords confidence in studies of motoneuron activity in CM.

On the importance of precise electrode placement for targeted transcranial electric stimulation

Transcranial electric stimulation (TES) is an increasingly popular method for non-invasive modulation of brain activity and a potential treatment for neuropsychiatric disorders. However, there are concerns about the reliability of its application because of variability in TES-induced intracranial electric fields across individuals. While realistic computational models offer can help to alleviate these concerns, their direct empirical validation is sparse, and their practical implications are not always clear. In this study, we combine direct intracranial measurements of electric fields generated by TES in surgical epilepsy patients with computational modeling. First, we directly validate the computational models and identify key parameters needed for accurate model predictions. Second, we derive practical guidelines for a reliable application of TES in terms of the precision of electrode placement needed to achieve a desired electric field distribution. Based on our results, we recommend electrode placement accuracy to be < 1 cm for a reliable application of TES across sessions.