Robotic Milling of Electrode Lead Channels During Cochlear Implantation in an ex-vivo Model

Objective: Robotic cochlear implantation is an emerging surgical technique for patients with sensorineural hearing loss. Access to the middle and inner ear is provided through a small-diameter hole created by a robotic drilling process without a mastoidectomy. Using the same image-guided robotic system, we propose an electrode lead management technique using robotic milling that replaces the standard process of stowing excess electrode lead in the mastoidectomy cavity. Before accessing the middle ear, an electrode channel is milled robotically based on intraoperative planning. The goal is to further standardize cochlear implantation, minimize the risk of iatrogenic intracochlear damage, and to create optimal conditions for a long implant life through protection from external trauma and immobilization in a slight press fit to prevent mechanical fatigue and electrode migrations.Methods: The proposed workflow was executed on 12 ex-vivo temporal bones and evaluated for safety and efficacy. For safety, the difference between planned and resulting channels were measured postoperatively in micro-computed tomography, and the length outside the planned safety margin of 1.0 mm was determined. For efficacy, the channel width and depth were measured to assess the press fit immobilization and the protection from external trauma, respectively.Results: All 12 cases were completed with successful electrode fixations after cochlear insertions. The milled channels stayed within the planned safety margins and the probability of their violation was lower than one in 10,000 patients. Maximal deviations in lateral and depth directions of 0.35 and 0.29 mm were measured, respectively. The channels could be milled with a width that immobilized the electrode leads. The average channel depth was 2.20 mm, while the planned channel depth was 2.30 mm. The shallowest channel depth was 1.82 mm, still deep enough to contain the full 1.30 mm diameter of the electrode used for the experiments.Conclusion: This study proposes a robotic electrode lead management and fixation technique and verified its safety and efficacy in an ex-vivo study. The method of image-guided robotic bone removal presented here with average errors of 0.2 mm and maximal errors below 0.5 mm could be used for a variety of other otologic surgical procedures.

Surgical Management of Deep Brain Stimulator Infection without Electrode Removal: Report of Two Cases

Objective Stimulation of the subthalamic nucleus by implanted electrodes (deep brain stimulation [DBS]) is performed to suppress symptoms of Parkinson's disease. However, postoperative wound dehiscence and infection can require removal of the implanted electrode leads. This report describes treatment of intractable unilateral wound infection in two patients without removing the DBS device. Methods First, components of the DBS system were removed except for the electrode lead and thorough debridement of the infected wound was conducted. Second, the edges of the bone defect left by removal of DBS components were smoothed to eliminate dead space. Subsequently, the electrode lead was covered by using a pericranial-frontalis-muscle flap or a bi-pedicled-scalp flap with good blood supply. Closed intrawound continuous negative pressure and irrigation treatment was conducted for 1 week after the surgery, and then the drain was removed. Results We treated two patients with wound infection after implantation of DBS electrodes. Case 1 developed a cutaneous fistula and Case 2 had wound dehiscence. After treatment by the method described above, complete wound healing was achieved in both patients. Conclusion DBS is always associated with a risk of infection or exposure of components and treatment can be very difficult. We successfully managed intractable wound infection while leaving the electrode lead in situ, so that it was subsequently possible to continue DBS for Parkinson's disease.

Effect of Depth of Total Intravenous General Anesthesia on Intraoperative Electrically Evoked Compound Action Potentials in Cochlear Implantation Surgery

Purpose. This study aims to compare the effect of the depth of total intravenous anesthesia (TIVA) on intraoperative electrically evoked compound action potential (e-ECAP) thresholds in cochlear implant operations. Methods. Prospectively, a total of 39 patients aged between 1 and 48 years who were scheduled to undergo cochlear implantation surgeries were enrolled in this study. Every patient received both light and deep TIVA during the cochlear implant surgery. The e-ECAP thresholds were obtained during the light and deep TIVA. Results. After comparing the e-ECAP means for each electrode (lead) between the light and deep anesthesia, no significant differences were detected between the light and deep anesthesia. Conclusion. The depth of TIVA may have no significant influence on the e-ECAP thresholds as there was no statistical difference between the light and deep anesthesia.

Modeling radiofrequency responses of realistic multi-electrode leads containing helical and straight wires

Purpose To present a modeling workflow for the evaluation of a lead electromagnetic model (LEM) consisting of a transfer function (TF) and a calibration factor. The LEM represents an analytical relationship between the RF response of a lead and the incident electromagnetic field. The study also highlights the importance of including key geometric details of the lead and the electrode when modeling multi-electrode leads. Methods The electrical and thermal responses of multi-electrode leads with helical and straight wires were investigated using 3D electromagnetic (EM) and thermal co-simulations. The net dissipated power (P) around each lead electrode and the net temperature increase at the electrodes (ΔT) were obtained for a set of incident EM fields with different spatial distributions. A reciprocity approach was used to determine a TF for each electrode based on the results of the computational model. The evaluation of the calibration factors and the TF validation were performed using the linear regression of P versus the LEM predictions. Results P and ΔT were investigated for four multi-electrode leads and four single-electrode leads containing either helical or straight wires. All electrodes of the multi-electrode lead were found to be points of high power deposition and temperature rise. The LEMs for the individual electrodes varied substantially. A significant dependence of the calibration factors on the surrounding tissue medium was also found. Finally, the model showed that the TF, the calibration factor, P and ΔT for multi-electrode leads differ significantly from those for single-electrode leads. Conclusion These results highlight the need to evaluate a LEM for each electrode of a multi-electrode lead as well as for each possible surrounding medium. It is also shown that the results derived from simulations based on simplified single-electrode leads can significantly mislead multi-electrode lead analyses.

Behavior Modification of Nanostructured PbO2 Electrodes in Lead Acid Batteries Changing Electrolyte Concentration and Separator

Currently, lead acid battery is extensively investigated owing to its prevalent use as a startinglighting and ignition device. An essential role for electrochemical reactions is played by the surface area available for conversion reactions and a possible approach is the use of nanostructured electrodes. In this work, lead dioxide nanostructured electrodes were tested in order to investigate the dependence of the charge and discharge behaviour on some parameters such as electrolyte concentration, and a new type of thin separator. In this last case, it is possible to reduce the size of the cell by using a very thin separator comparable to the nanostructured electrode thickness. Besides, a low concentration of electrolyte was also tested for studying its influence on the performance of a nanostructured electrode. Lead dioxide electrodes were cycled at 1C-rate and discharged to a cutoff voltage of 1.2 V up to 90% of the gravimetric capacity. Electrodes were assembled in a zero gap configuration using a commercial negative plate as counter-electrode with a large excess of active mass in comparison to the nanostructured one. Tests were conducted in very stressful conditions, in order to compare the behaviour of this new type of battery with that of the commercial one.

Comparison of Two Transvenous Temporary Pacemaker Fixation Methods: FIX-IT Trial

Introduction: the necessity for a temporary pacemaker (TP) goes through several scenarios. Some patients require the device to complete an infection treatment, regain the pace after myocardial infarction, or while awaiting the release of the definitive device by the health care provider. Regardless of the TP passage technique, good electrode fixation is essential, avoiding dislocation and the necessity for repositioning, among other complications. Objective: to compare two forms of TP fixation, one under direct fixation to the skin and the other keeping the venous introducer connected to the plastic protection through the pacemaker electrode lead. Methods: Forty patients were randomized, 20 in each group. Data regarding the procedure time, electrode lead position, command thresholds, sensitivity, and complications were recorded. The primary outcome considered was the necessity for repositioning or exchange of transvenous TP and secondary any complication without the necessity to reposition it. Results: There were no significant differences in the total duration of the procedure between the groups in the initial position of the electrode and the access route used. The group with plastic protection had a higher primary outcome (60%) than the direct fixation group (20%; p = 0.0098). There were no differences regarding the secondary outcome (p = 1.0). The group with plastic protection also had more total complications compared to the other group (p = 0.0262). Conclusion: Direct fixation of the pacemaker electrode lead was safer concerning the fixation with plastic protection, reducing complications such as electrode dislocation requiring repositioning or replacement without increasing the procedure time.

Simultaneous Stimulation of the Globus Pallidus Interna and the Nucleus Basalis of Meynert in the Parkinson-Dementia Syndrome

Background/Aim: The prevalence of cognitive symptoms in recently diagnosed Parkinson’s disease (PD) patients may be as high as 60%. We report a novel deep brain stimulation (DBS) strategy targeting both motor and cognitive symptoms. Methods: A PD patient diagnosed with mild cognitive impairment underwent DBS surgery targeting the globus pallidus interna (GPi; to treat motor symptoms) and the nucleus basalis of Meynert (NBM; to treat cognitive symptoms) using a single electrode per hemisphere. Results: Compared to baseline, 2-month follow-up after GPi stimulation was associated with motor improvements, whereas partial improvements in cognitive functions were observed 3 months after the addition of NBM stimulation to GPi stimulation. Conclusion: This case explores an available alternative for complete DBS treatment in PD, stimulating 2 targets at different frequencies with a single electrode lead.

Garments for functional electrical stimulation: Design and proofs of concept

Introduction Repeated use of functional electrical stimulation can promote functional recovery in individuals with neurological paralysis. We designed garments able to deliver functional electrical stimulation. Methods Shirts and pants containing electrodes knitted with a conductive yarn were produced. Electrodes were moistened with water before use. Stimulation intensity at four thresholds levels (sensory, movement, full range of motion, and maximal), stimulation comfort, and electrical properties of the interface were tested in one able-bodied subject with garment electrodes and size-matched conventional gel electrodes. The pants and shirt were then used to explore usability and design limitations. Results Compared to gel electrodes, fabric electrodes had a lower sensory threshold (on forearm muscles) but they had a higher maximal stimulation threshold (for all tested muscles). The stimulation delivery was comfortable when the garment electrodes were recently moistened; however, as the electrodes dried (within 9 to 18 min) stimulation became unpleasant. Inconsistent water content in the fabric electrodes caused inconsistent intensity thresholds and inconsistent voltage necessary to apply a desired stimulation current. Garments’ tightness and impracticality of electrode lead necessitate further design improvement. Conclusions Fabric electrodes offer a promising alternative to gel electrodes. Further work involving people with paralysis is required to overcome the identified challenges.