Final Electrode Position Research Articles

Intraoperative 3D fluoroscopy accurately predicts final electrode position in deep brain stimulation surgery

PurposeIn the absence of an intraoperative CT or MRI setup, post-implantation confirmation of electrode position in deep brain stimulation (DBS) requires patient transportation to the radiology unit, prolonging surgery time. This project aims to validate intraoperative 3D fluoroscopy (3DF), a widely available tool in Neurosurgical units, as a method to determine final electrode position.MethodsWe performed a retrospective study including 64 patients (124 electrodes) who underwent DBS at our institution. Intraoperative 3DF after electrode implantation and postoperative volumetric CT were acquired. The Euclidean coordinates of the electrode tip displayed in both imaging modalities were determined and inter-method deviations were assessed. Pneumocephalus was quantified and its potential impact in determining the electrode position analyzed. Finally, 3DF and CT-imposed exposure to radiation was compared.ResultsThe difference between the electrode tip estimated by 3DF and CT was 0.85 ± 0.03 mm, and not significantly different (p = 0.11 for the distance to MCP assessed by both methods), but was, instead, highly correlated (p = 0.91; p < 0.0001). Even though pneumocephalus was larger in 3DF (6.89 ± 1.76 vs 5.18 ± 1.37 mm3 in the CT group, p < 0.001), it was not correlated with the difference in electrode position measured by both techniques (p = 0.17; p = 0.06). Radiation exposure from 3DF is significantly lower than CT (0.36 ± 0.03 vs 2.08 ± 0.05 mSv; p < 0.0001).ConclusionsIntraoperative 3DF is comparable to CT in determining the final DBS electrode position. Being a method with fewer radiation exposure, less expensive, faster and that avoids patient transportation outside the operation room, it is a valid tool to replace postoperative CT.

Review of the targeting accuracy of frameless and frame-based robot-assisted deep brain stimulation electrode implantation in pediatric patients using the Neurolocate module.

The Neurolocate module is a 3D frameless patient registration module that is designed for use with the Neuromate stereotactic robot. Long-term electrical stimulation of the globus pallidus internus (GPi) and subthalamic nucleus (STN) via deep brain electrode implantation is particularly successful in a select group of movement disorders in pediatric patients. This study aimed to review the targeting accuracy of deep brain stimulation (DBS) electrode implantation in a single center, comparing standard frame-based techniques to the frameless Neurolocate module. Twenty-four pediatric patients underwent implantation of bilateral DBS electrodes under general anesthesia during the period of August 2018-August 2022. All patients underwent robot-assisted stereotactic implantation of DBS electrodes using an intraoperative O-arm 3D scanner to confirm the final electrode position. These coordinates were compared with the planned entry and target, with attention to depth, radial, directional, and absolute errors, in addition to Euclidean distance (ED). The primary outcome evaluated the accuracy and safety of the Neurolocate frameless technology compared with standard frame-based techniques. Of the 24 bilateral DBS electrode implantations performed, 62.5% used Neurolocate technology: 87.5% were delivered to the GPi and the remaining 12.5% to the STN. The mean patient age was 11.0 (range 4-18) years and 70.8% were male. The median absolute errors in x-, y-, and z-axes were 0.35, 0.75, and 0.9 mm, respectively, using the Neurolocate module compared with 0.30, 0.95, and 1.1 mm using the standard frame-based technique. The median ED from the planned target to the actual electrode position with the Neurolocate module was 1.28 mm versus 1.69 mm using standard frame-based techniques. No major perioperative complications occurred. Stereotactic robot-assisted DBS implantation with the frameless Neurolocate module is safe for use in the pediatric population, showing good surgical accuracy and no inferiority to standard frame-based techniques. The Neurolocate module for robotic DBS surgery has the potential to improve surgical targeting accuracy, surgical time, patient comfort, and safety.

Susceptibility-Weighted MRI Approximates Intraoperative Microelectrode Recording During Deep Brain Stimulation of the Subthalamic Nucleus for Parkinson's Disease

Deep brain stimulation of the subthalamic nucleus (STN-DBS) for Parkinson's disease can be performed with intraoperative neurophysiological and radiographic guidance. Conventional T2-weighted magnetic resonance imaging sequences, however, often fail to provide definitive borders of the STN. Novel magnetic resonance imaging sequences, such as susceptibility-weighted imaging (SWI), might better localize the STN borders and facilitate radiographic targeting. We compared the radiographic location of the dorsal and ventral borders of the STN using SWI with intraoperative microelectrode recording (MER) during awake STN-DBS for Parkinson's disease. Thirteen consecutive patients who underwent placement of 24 STN-DBS leads for Parkinson's disease were analyzed retrospectively. Preoperative targeting was performed with SWI, and MER data were obtained from intraoperative electrophysiology records. The boundaries of the STN on SWI were identified by a blinded investigator. The final electrode position differed significantly from the planned coordinates in depth but not in length or width, indicating that MER guided the final electrode depth. When we compared the boundaries of the STN by MER and SWI, SWI accurately predicted the entry into the STN but underestimated the length and ventral boundary of the STN by 1.2 mm. This extent of error approximates the span of a DBS contact and could affect the placement of directional contacts within the STN. MER might continue to have a role in STN-DBS. This could potentially be mitigated by further refinement of imaging protocols to better image the ventral boundary of the STN.

Cochlear implantation in advanced otosclerosis: utility of pre-operative radiological assessment in predicting intra-operative difficulty and final electrode position.

This study aimed to determine if pre-operative radiological scoring can reliably predict intra-operative difficulty and final cochlear electrode position in patients with advanced otosclerosis. A retrospective cohort study of advanced otosclerosis patients who underwent cochlear implantation (n = 48, 52 ears) was compared with a larger cohort of post-lingually deaf adult patients (n = 1414) with bilateral hearing loss and normal cochlear anatomy. Pre-operative imaging for advanced otosclerosis patients and final electrode position were scored and correlated with intra-operative difficulty and speech outcomes. Advanced otosclerosis patients benefit significantly from cochlear implantation. Mean duration of deafness was longer in the advanced otosclerosis group (19.5 vs 14.3 years; p < 0.05). Anatomical changes in advanced otosclerosis can result in increased difficulty of surgery. Evidence of pre-operative cochlear luminal changes was associated with intra-operative difficult insertion and final non-scala tympani position. Nearly all electrodes implanted in the advanced otosclerosis cohort were peri-modiolar. No reports of facial nerve stimulation were observed.

105 Value of Atlas-Based Data and Intraoperative Testing in Deep Brain Stimulation

INTRODUCTION: Deep brain stimulation (DBS) is commonly performed awake to collect intraoperative microelectrode recordings (MER) and macrostimulation to optimize efficacy and minimize side effects (Bour et al, 2010). With supplementary information from an atlas-based database (CranialVault), efficacy heat maps guide initial targeting, intraoperative final electrode position (FEP) selection and post-operative programming (D’Haese et al, 2012). A better understanding of how this data is integrated to inform all stages of DBS can assist in reducing OR time, optimizing electrode position, expediting programming, and enhancing patient outcomes. METHODS: 451 individual patients who underwent DBS for Parkinson’s Disease, Essential Tremor or Dystonia, treated with 822 individual leads, at Vanderbilt University Medical Center between 2011-2021 were included. Intraoperative testing data including MER firing rate, macrostimulation efficacy and coordinates of FEP were retrieved from the CranialVault database. Average coordinates of planned target, midpoint and bottom of FEP, active contact and centroid of heat maps per target in patient space were calculated and visualized. Medical charts were reviewed for 1-year post-operative outcomes. RESULTS: The distribution of FEPs per target include 55.2% of leads placed in center track. Average coordinates in patient space of planned target, centroid of heatmap, midpoint and bottom of FEP and active contact were recorded. MER data demonstrates how multiunit activity changes at different depths relative to target, per target. Patients who achieve 4th quartile efficacy intraoperatively are more likely to achieve maximal benefit at 1-year post-op (p = 0.003, chi-squared). CONCLUSIONS: Atlas-based data and intraoperative testing is valuable, often leads to changes in FEP and can predict post-operative outcomes.

Bilateral deep brain stimulation of the subthalamic nucleus: Targeting differences between the first and second side

Introduction and objectivesDeep brain stimulation (DBS) of the subthalamic nucleus (STN) is a recognized treatment for drug-refractory Parkinson's disease (PD). However, the therapeutic success depends on the accuracy of targeting. This study aimed to evaluate potential accuracy differences in the placement of the first and second electrodes implanted, by comparing chosen electrode trajectories, STN activity detected during microelectrode recording (MER), and the mismatch between the initially planned and final electrode positions on each side. Materials and methodsIn this retrospective cohort study, we analyzed data from 30 patients who underwent one-stage bilateral DBS. For most patients, three arrays of microelectrodes were used to determine the physiological location of the STN. Final target location depended also on the results of intraoperative stimulation. The choice of central versus non-central channels was compared. The Euclidean vector deviation was calculated using the initially planned coordinates and the final position of the tip of the electrode according to a CT scan taken at least a month after the surgery. ResultsThe central channel was chosen in 70% of cases on the first side and 40% of cases on the second side. The mean length of high-quality STN activity recorded in the central channel was longer on the first side than the second (3.07±1.85mm vs. 2.75±1.94mm), while in the anterior channel there were better MER recordings on the second side (1.59±2.07mm on the first side vs. 2.78±2.14mm on the second). Regarding the mismatch between planned versus final electrode position, electrodes on the first side were placed on average 0.178±0.917mm lateral, 0.126±1.10mm posterior and 1.48±1.64mm inferior to the planned target, while the electrodes placed on the second side were 0.251±1.08mm medial, 0.355±1.29mm anterior and 2.26±1.47mm inferior to the planned target. ConclusionThere was a tendency for the anterior trajectory to be chosen more frequently than the central on the second side. There was also a statistically significant deviation of the second electrodes in the anterior and inferior directions, when compared to the electrodes on the first side, suggesting that another cause other than brain shift may be responsible. We should therefore factor this during planning for the second implanted side. It might be useful to plan the second side more anteriorly, possibly reducing the number of MER trajectories tested and the duration of surgery.

Bilateral deep brain stimulation of the subthalamic nucleus: Targeting differences between the first and second side

Introduction and objectivesDeep brain stimulation (DBS) of the subthalamic nucleus (STN) is a recognized treatment for drug-refractory Parkinson's disease (PD). However, the therapeutic success depends on the accuracy of targeting. This study aimed to evaluate potential accuracy differences in the placement of the first and second electrodes implanted, by comparing chosen electrode trajectories, STN activity detected during microelectrode recording (MER), and the mismatch between the initially planned and final electrode positions on each side. Materials and methodsIn this retrospective cohort study, we analyzed data from 30 patients who underwent one-stage bilateral DBS. For most patients, three arrays of microelectrodes were used to determine the physiological location of the STN. Final target location depended also on the results of intraoperative stimulation. The choice of central versus non-central channels was compared. The Euclidean vector deviation was calculated using the initially planned coordinates and the final position of the tip of the electrode according to a CT scan taken at least a month after the surgery. ResultsThe central channel was chosen in 70% of cases on the first side and 40% of cases on the second side. The mean length of high-quality STN activity recorded in the central channel was longer on the first side than the second (3.07±1.85mm vs. 2.75±1.94mm), while in the anterior channel there were better MER recordings on the second side (1.59±2.07mm on the first side vs. 2.78±2.14mm on the second). Regarding the mismatch between planned versus final electrode position, electrodes on the first side were placed on average 0.178±0.917mm lateral, 0.126±1.10mm posterior and 1.48±1.64mm inferior to the planned target, while the electrodes placed on the second side were 0.251±1.08mm medial, 0.355±1.29mm anterior and 2.26±1.47mm inferior to the planned target. ConclusionThere was a tendency for the anterior trajectory to be chosen more frequently than the central on the second side. There was also a statistically significant deviation of the second electrodes in the anterior and inferior directions, when compared to the electrodes on the first side, suggesting that another cause other than brain shift may be responsible. We should therefore factor this during planning for the second implanted side. It might be useful to plan the second side more anteriorly, possibly reducing the number of MER trajectories tested and the duration of surgery.

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.

Prospective analysis of gross and fine electrode position and motor manifestations after STN-DBS and their correlation with electrode position.

Deep brain stimulation (DBS) has been proven to be a safe, reversible, cost-effective procedure for treatment of Parkinson's disease. Final electrode position remains a significant factor determining the outcomes of subthalamic nucleus DBS (STN-DBS). This study aims to analyze the final lead position in three-dimensional plane and its effect on gross and fine motor outcomes in cases of advanced Parkinson's disease operated for STN-DBS. Patients who underwent bilateral STN-DBS were prospectively followed for improvement in gross motor outcomes at 6 months. Improvement in dysgraphia was analyzed by Fahn-Tolosa-Marin Tremor Rating Scale Part B Score. Postoperative outcomes were correlated with final electrode position. A total of 64 Patients (128 leads) were analyzed. Patients who were less than 65 years of age at time of surgery had more significant reduction in UPDRS III (P=0.02). Cases with deviation of left x less than 3 mm had significant reduction in UPDRS III (P=0.05) and speech sub-scores (P=0.05). Deviation less than 2 mm in left x was associated with reduction in gait sub-scores (P=0.04). Optimal placement of right y electrode was associated with reduction in UPDRS III (P=0.02). Significant reduction in Fahn-Tolosa-Marin Tremor Rating Scale Part B Score was noted after DBS (P=0.001). Subthalamic nucleus DBS thus results in significantly improved functional outcome particularly in patients with age less than 65 years. Accurate final electrode position is associated with maximum clinical benefit and improvement in dysgraphia.

Prospective analysis of motor manifestations following STN-DBS and their correlation with electrode position

Deep brain stimulation (DBS) has been proven to be a safe, reversible, cost effective procedure for treatment of Parkinson's disease Final electrode position remains a significant factor determining the outcomes of STN-DBS. This study aims to analyze the final lead position in three-dimensional plane and its effect on motor outcomes in cases operated for STN-DBS.

The Accuracy of Direct Targeting Using Fusion of MR and CT Imaging for Deep Brain Stimulation of the Subthalamic Nucleus in Patients with Parkinson's Disease.

In 33 consecutive patients with Parkinson's disease (PD) undergoing awake deep brain stimulation (DBS) without microelectrode recording (MER), we assessed and validated the precision and accuracy of direct targeting of the subthalamic nucleus (STN) using preoperative magnetic resonance imaging (MRI) and stereotactic computed tomography (CT) image fusion combined with immediate postoperative stereotactic CT and postoperative MRI, and we report on the side effects and clinical results up to 6 months' follow-up. Preoperative nonstereotactic MRI and stereotactic CT images were merged and used for planning the trajectory and final lead position. Immediate postoperative stereotactic CT and postoperative nonstereotactic MRI provided the validation of the final electrode position. Changes in the Unified Parkinson's Disease Rating Scale III (UPDRS III) scores and the levodopa equivalent daily doses (LEDD) and appearance of adverse side effects were assessed. The mean Euclidian distance (ED) error between the planned position and the final position of the lead in the left STN was 1.69 ± 0.82 mm and that in the right STN was 2.12 ± 1.00. The individual differences between planned and final position in each of the three coordinates were less than 2 mm. The UPDRS III scores improved by 75% and LEDD decreased by 45%. Few patients experienced complications, such as postoperative infection (n = 1), or unwanted side effects, such as emotional instability (n = 1). Our results confirm that direct targeting of an STN on stereotactic CT merged with MRI could be a valid method for placement the DBS electrode. The magnitude of our targeting error is comparable with the reported errors when using MER and other direct targeting approaches.

Biplanar X-Ray Methods for Stereotactic Intraoperative Localization in Deep Brain Stimulation Surgery.

Efficacy in deep brain stimulation (DBS) is dependent on precise positioning of electrodes within the brain. Intraoperative fluoroscopy, computed tomography (CT), or magnetic resonance imaging are used for stereotactic intraoperative localization (StIL), but the utility of biplanar X-ray has not been evaluated in detail. To determine if analysis of orthogonal biplanar X-rays using graphical analysis (GA), ray tracing (RT), and/or perspective projection (PP) can be utilized for StIL. A review of electrode tip positions comparing postoperative CT to X-ray methods was performed for DBS operations containing orthogonal biplanar X-ray with referential spheres and pins. Euclidean (Re) errors for final DBS electrode position on intraoperative X-rays vs postoperative CT using GA, RT, and PP methods averaged 1.58 mm (±0.75), 0.74 mm (±0.45), and 1.07 mm (±0.64), respectively (n=56). GA was more accurate with a ventriculogram. RT and PP predicted positions that correlated with third ventricular structures on ventriculogram cases. RT was the most stable but required knowledge of the geometric setup. PP was more flexible than RT but required well-distributed reference points. A single case using the O-arm demonstrated Re errors of 0.43 mm and 0.28 mm for RT and PP, respectively. In addition, these techniques could also be used to calculate directional electrode rotation. GA, RT, and PP can be employed for precise StIL during DBS using orthogonal biplanar X-ray. These methods may be generalized to other stereotactic procedures or instances of biplanar imaging such as angiograms, radiosurgery, or injection therapeutics.

Awake Testing during Deep Brain Stimulation Surgery Predicts Postoperative Stimulation Side Effect Thresholds.

Despite substantial experience with deep brain stimulation for movement disorders and recent interest in electrode targeting under general anesthesia, little is known about whether awake macrostimulation during electrode targeting predicts postoperative side effects from stimulation. We hypothesized that intraoperative awake macrostimulation with the newly implanted DBS lead predicts dose-limiting side effects during device activation in clinic. We reviewed 384 electrode implants for movement disorders, characterized the presence or absence of stimulus amplitude thresholds for dose-limiting DBS side effects during surgery, and measured their predictive value for side effects during device activation in clinic with odds ratios ±95% confidence intervals. We also estimated associations between voltage thresholds for side effects within participants. Intraoperative clinical response to macrostimulation led to adjustments in DBS electrode position during surgery in 37.5% of cases (31.0% adjustment of lead depth, 18.2% new trajectory, or 11.7% both). Within and across targets and disease states, dose-limiting stimulation side effects from the final electrode position in surgery predict postoperative side effects, and side effect thresholds in clinic occur at lower stimulus amplitudes versus those encountered in surgery. In conclusion, awake clinical testing during DBS targeting impacts surgical decision-making and predicts dose-limiting side effects during subsequent device activation.

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.

Implantation of Depth Electrodes in Children Using VarioGuide® Frameless Navigation System: Technical Note.

Electrode placement in epilepsy surgery seeks to locate the sites of ictal onset and early propagation. An invasive diagnostic procedure, stereoelectroencephalography (SEEG) is usually implemented with frame-based methods that can be especially problematic in young children. To evaluate the feasibility and accuracy of a new technique for frameless SEEG in children using the VarioGuide® system (Brainlab AG, München, Germany). A frameless stereotactic navigation system was used to implant depth electrodes with percutaneous drilling and bolt insertion in pediatric patients with medically refractory epilepsy. Data on general demographic information of electrode implantation, duration, number, and complications were retrospectively collected. To determine the placement accuracy of the VarioGuide® frameless system, the mean Euclidean distances were calculated by comparing the preoperatively planned trajectories with the final electrode position observed on postoperative computed tomography scans. From May 2011 to December 2015, 15 patients (8 males, 7 females; mean age: 8 yr, range: 3-16 yr) underwent SEEG depth electrode implantation of a total of 111 electrodes. The mean error measured by the Euclidean distance from the center of the entry point to the intended entry point was 3.64 ± 1.78 mm (range: 0.58-7.59 mm) and the tip of the electrode to the intended target was 2.96 ± 1.49 mm (range: 0.58-7.82 mm). There were no significant complications. Depth electrodes can be placed safely and accurately in children using the VarioGuide® frameless stereotactic navigation system.

Intra- and Postoperative Electrocochleography May Be Predictive of Final Electrode Position and Postoperative Hearing Preservation.

Introduction: The objectives of the current study were to (1) determine the relationship between electrocochleography (ECochG), measured from the cochlear implant (CI) electrode array during and after implantation, and postoperative audiometric thresholds, (2) determine the relationship between ECochG amplitude and electrode scalar location determined by computerized tomography (CT); and (3) determine whether changes in cochlear microphonic (CM) amplitude during electrode insertion were associated with postoperative hearing.Materials and Methods: Eighteen subjects undergoing CI with an Advanced Bionics Mid-Scala device were prospectively studied. ECochG responses were recorded using the implant coupled to a custom signal recording unit. ECochG amplitude collected intraoperatively concurrent with CI insertion and at activation was compared with audiometric thresholds postoperatively. Sixteen patients also underwent postoperative CT to determine scalar location and the relationship to ECochG measures and residual hearing.Results: Mean low-frequency pure tone average (LFPTA) increased following surgery by an average of 28 dB (range 8–50). Threshold elevation was significantly greater for electrodes with scalar dislocation. No correlation was found between intraoperative ECochG and postoperative behavioral thresholds collapsed across frequency; however, mean differences in thresholds measured by intraoperative ECochG and postoperative audiometry were significantly smaller for electrodes inserted completely within scala tympani (ST) vs. those translocating from ST to scala vestibuli. A significant correlation was observed between postoperative ECochG thresholds and behavioral thresholds obtained at activation.Discussion: Postoperative audiometry currently serves as a marker for intracochlear trauma though thresholds are not obtained until device activation or later. When measured at the same time-point postoperatively, low-frequency ECochG thresholds correlated with behavioral thresholds. Intraoperative ECochG thresholds, however, did not correlate significantly with postoperative behavioral thresholds suggesting that changes in cochlear physiology occur between electrode insertion and activation. ECochG may hold clinical utility providing surgeons with feedback regarding insertion trauma due to scalar translocation, which may be predictive of postoperative hearing preservation.Conclusion: CI insertion trauma is generally not evident until postoperative audiometry when loss of residual hearing is confirmed. ECochG has potential to provide estimates of trauma during insertion as well as reliable information regarding degree of hearing preservation.

Shock efficacy of single and dual coil electrodes-new insights from the NORDIC ICD Trial.

Dual coil (DC) electrodes are preferred to single coil (SC) electrodes because of an assumed higher shock efficacy. However, DC-electrodes may be associated with an increased difficulty and risk of lead extraction. We aimed to compare SC- and DC-electrodes with respect to the first shock efficacy (FSE) after implantable cardioverter defibrillator (ICD) implantation. One thousand and seventy-seven patients of the NORDIC ICD trial were randomly assigned to first time ICD implantation with or without defibrillation (DF) testing. The electrode configuration was determined before randomization. One thousand and sixty-seven patients eventually received an ICD, 516 (48.4%) with a SC- and 551 (51.6%) with a DC-electrode. DC-electrodes were preferentially selected in older patients, renal failure, atrial fibrillation, dual chamber, Cardiac Resynchronization Therapy (CRT) devices, angiotensin-converting-enzyme (ACE) inhibitors/angiotensin (AT) receptor blockers and without Sotalol. However, the preference of the investigational site was dominant over clinical parameters. The DF energy at the final electrode position was higher in SC-electrodes (adjusted difference +1.15 J; P = 0.005; only patients tested). Less patients with DC-electrodes required intra-operative system reconfiguration (adjusted difference -3.9; P = 0.046; only patients tested). Using mixed logistic regression, the FSE was 92.6% in SC- and 97.8% in DC-electrodes (adjusted odds ratio 4.3 (95% confidence interval [1.9, 9.8]; P < 0.001)). Dual coil-electrode selection mainly depends on the preference of the investigational site and seems to be preferred in older patients, renal failure, atrial fibrillation, dual chamber, and CRT devices. Patients with DC-electrodes required less intraoperative system reconfigurations. Dual coil-electrodes provided a substantially higher FSE during follow-up. Mortality rates were not significantly different in patients with DC- and SC-electrodes.

Optimizing Final Electrode Placement Based on Intraoperative Neurophysiological Evaluation during Subthalamic Deep Brain Stimulation for Parkinson’s Disease

Background and purpose: Target point identification based solely on MRI and CT of subthalamic nucleus (STN) in deep brain stimulation procedures (DBS) for Parkinson’s disease (PD) might have suboptimal clinical effects. The authors analyse alterations of permanent electrode location depending on neurophysiological evaluation compared to an anatomically based calculated target. Materials and methods: The group comprised 66 patients (32 females and 34 males) aged 57.6 (38–76) years, in whom 131 electrodes were implanted. The patients were qualified for the surgery according to the CAPSIT-PD criteria. STN was identified using the direct and indirect methods, based on 1.5 T MRI and CT. The surgery was performed under local anesthesia. Two to 5 microelectrodes were used for microrecording and macrostimulation. Results: Anterior (49.2%), central (35.6%) and lateral (13.6%) trajectories were most frequently used for permanent electrode placement. The electrode was most frequently placed at a depth of +2/+3 (58.3%) or +1 and +5 mm (36.4%) with regard to the planned target point. Differences in selecting the trajectory and depth of the final electrode position were statistically significant (p<0.05). Conclusion: DBS implantation based only on anatomical identification of STN can lead to suboptimal results. Additional application of intrasurgical neurophysiological analysis may increase the effectiveness of the STN DBS therapy for PD.

Evaluation of a new mid-scala cochlear implant electrode using microcomputed tomography.

To investigate electrode position, depth of insertion, and electrode contact using an electrode array with a mid-scala design following round window (RW) and cochleostomy insertion. Eight fresh-frozen cadaveric bones were implanted; half via a RW approach and half through an anteroinferior cochleostomy using a styleted mid-scala electrode design. Microcomputed tomography was used to acquire oblique coronal and oblique axial reformations. Individual electrode positions along each array, insertional depth, and electrode contact were determined using National Institutes of Health Image J software. All electrodes were inserted without significant resistance. The average angular depth of insertion was 436.5° for the RW group and 422.7° for the cochleostomy group. All electrodes acquired a perimodiolar position in the proximal segment and a lateral wall position at the basal turn, regardless of approach. Electrodes distal to the basal turn demonstrated a variable location, with 78% mid scala. One cochleostomy array fractured through the interscalar partition (ISP), acquiring a scala vestibuli position. The odds ratio for either abutting the modiolus, ISP, lateral wall or floor, or fracturing through the ISP were 2.7 times more likely following a cochleostomy insertion (P = .032). The styleted mid-scala electrode design acquires a proximal perimodiolar position, a lateral wall location, as it traverses the basal turn, and most commonly a mid-scala position in the distal array. Interscalar excursion occurred in one of the cochleostomy insertions. Cochleostomy insertion is more likely to result in ultimate final electrode position adjacent to critical intracochlear structures. NA.

The surgical technique of occipital nerve stimulation.

Occipital nerve stimulation is increasingly used in the treatment of primary headache disorders. We describe a surgical technique applying preoperative fluoroscopy and intraoperative tactile orientation designed to reduce radiation exposure and provide reproducible results. Under general anesthesia and in the supine position, the C1-C2 transition is identified fluoroscopically and marked with an electrocardiogram (ECG) electrode prior to surgery. During electrode placement, the ECG electrodes are used for tactile orientation of electrode direction and depth. The use of tactile orientation solely during surgery reduces radiation exposure and decreases the duration of surgery. This technique allows reproducible results of final electrode position.