Electrode Insertion Depth Research Articles

Observational study of left bundle branch area pacing: implantation of the solia S lead using the selectra 3D sheath at an inclined angle

BackgroundLeft Bundle Branch Area Pacing (LBBaP) is a cardiac pacing technique designed to mimic the natural conduction system of the heart. Traditional right ventricular apical pacing has been associated with increased risks of heart failure and atrial fibrillation. This study investigates the stability and safety of LBBaP using the Selectra 3D sheath (Biotronik) with an inclined angle for implanting the Solia S lead (Biotronik, SE & Co, KG).MethodsA single-center retrospective study was conducted on 25 patients who underwent LBBaP implantation using the Selectra 3D sheath at our hospital. The procedure involved inserting the Solia S lead into the interventricular septum at an inclined angle. Surgical and postoperative data were collected, including the success rate, depth and angle of electrode insertion, complications, and follow-up data.ResultsThe success rate of LBBaP implantation was 92%. The length of electrode insertion into the interventricular septum ranged from 12 to 23.0 mm, with an average of 18.1 ± 3.08 mm. The angle formed between the electrode and the septum ranged from 0° to 57.3°, with an average of 35.14°±14.31°. During the 3-month follow-up period, pacing parameters remained stable, and no complications were reported.ConclusionsLBBaP implantation using the Selectra 3D sheath with an inclined angle for the Solia S implantation demonstrates stability and safety. The procedure boasts a high success rate and offers an effective option for LBBaP implantation.

Effect of dispersive electrode position (anterior vs. posterior) in epicardial radiofrequency ablation of ventricular wall: A computer simulation study.

An epicardial approach is often used in radiofrequency (RF) catheter ablation to ablate ventricular tachycardia when an endocardial approach fails. Our objective was to analyze the effect of the position of the dispersive patch (DP) on lesion size using computer modeling during epicardial approach. We compared the posterior position (patient's back), commonly used in clinical practice, to the anterior position (patient's chest). The model considered ventricular wall thicknesses between 4 and 8 mm, and electrode insertion depths between .3 and .7 mm. RF pulses were simulated with 20 W of power for 30 s duration. Statistically significant differences (P < .001) were found between both DP positions in terms of baseline impedance, RF current (at 15 s) and thermal lesion size. The anterior position involved lower impedance (130.8 ± 4.7 vs. 146.2 ± 4.9 Ω) and a higher current (401.5 ± 5.6 vs. 377.5 ± 5.1 mA). The anterior position created lesion sizes larger than the posterior position: 8.9 ± 0.4 vs. 8.4 ± 0.4 mm in maximum width, 8.6 ± 0.4 vs. 8.1 ± 0.4 mm in surface width, and 4.5 ± 0.4 vs. 4.3 ± 0.4 mm in depth. Our results suggest that: (1) the redirection of the RF currents due to repositioning the PD has little impact on lesion size and only affects baseline impedance, and (2) the differences in lesion size are only 0.5 mm wider and 0.2 mm deeper for the anterior position, which does not seem to have a clinical impact in the context of VT ablation.

Cochlear implant electrode design for safe and effective treatment.

The optimal placement of a cochlear implant (CI) electrode inside the scala tympani compartment to create an effective electrode-neural interface is the base for a successful CI treatment. The characteristics of an effective electrode design include (a) electrode matching every possible variation in the inner ear size, shape, and anatomy, (b) electrically covering most of the neuronal elements, and (c) preserving intra-cochlear structures, even in non-hearing preservation surgeries. Flexible electrode arrays of various lengths are required to reach an angular insertion depth of 680° to which neuronal cell bodies are angularly distributed and to minimize the rate of electrode scalar deviation. At the time of writing this article, the current scientific evidence indicates that straight lateral wall electrode outperforms perimodiolar electrode by preventing electrode tip fold-over and scalar deviation. Most of the available literature on electrode insertion depth and hearing outcomes supports the practice of physically placing an electrode to cover both the basal and middle turns of the cochlea. This is only achievable with longer straight lateral wall electrodes as single-sized and pre-shaped perimodiolar electrodes have limitations in reaching beyond the basal turn of the cochlea and in offering consistent modiolar hugging placement in every cochlea. For malformed inner ear anatomies that lack a central modiolar trunk, the perimodiolar electrode is not an effective electrode choice. Most of the literature has failed to demonstrate superiority in hearing outcomes when comparing perimodiolar electrodes with straight lateral wall electrodes from single CI manufacturers. In summary, flexible and straight lateral wall electrode type is reported to be gentle to intra-cochlear structures and has the potential to electrically stimulate most of the neuronal elements, which are necessary in bringing full benefit of the CI device to recipients.

Comparison of depth of electrode insertion between cochleostomy and round window approach: a cadaveric study.

Round window approach and cochleostomy approach can have different depth of electrode insertion during cochlear implantation which itself can alter the audiological outcomes in cochlear implant. The current study was conducted to determine the difference in the depth of electrode insertion via cochleostomy and round widow approach when done serially in same temporal bone. This is a cross-sectional study conducted in the Department of Otorhinolaryngology in conjunction with Department of Anatomy and Department of Diagnostic and Interventional Radiology over a period of 1year. 12-electrode array insertion was performed via either approach (cochleostomy or round window) in the cadaveric temporal bone. HRCT temporal bone scan of the implanted temporal bone was done and depth of insertion and various cochlear parameters were calculated. A total of 12 temporal bones were included for imaging analysis. The mean cochlear duct length was 32.892mm; the alpha and beta angles were 58.175° and 8.350°, respectively. The mean angular depth of electrode insertion via round window was found to be 325.2° (SD = 150.5842) and via cochleostomy 327.350 (SD = 112.79) degree and the mean linear depth of electrode insertion via round window was found to be 18.80 (SD = 4.4962) mm via cochleostomy 19.650 (SD = 3.8087) mm, which was calculated using OTOPLAN 1.5.0 software. There was a statically significant difference in linear depth of insertion between round window and cochleostomy. Although the angular depth of insertion was higher in CS group, there was no statistically significant difference with round window type of insertion. The depth of electrode insertion is one of the parameters that influences the hearing outcome. Linear depth of electrode insertion was found to be more in case of cochleostomy compared to round window approach (p = 0.075) and difference in case of angular depth of electrode insertion existed but not significant (p = 0.529).

Numerical Simulation of Electromagnetic Field in Slab Electroslag Remelting Process with Double Electrode Series

In this paper, a mathematical model of an electromagnetic field during an electroslag remelting process of industrial-scale slab was established using a Maxwell 3D module in Ansys Electromagnetics Suite. The distribution characteristics of the magnetic field intensity, current density and Joule heat density during the electroslag remelting process were analyzed in detail. On this basis, the influence of the current frequency on the electroslag remelting process of an industrial scale is studied, and the influence of process parameters such as the slag pool depth, electrode insertion depth and ingot height on the electromagnetic field is also considered. The results show that the Joule heat generated in the slag pool is much greater than that of the electrode and the ingot. The maximum Joule heat is located at the contact between the electrode corner and the slag pool, and the Joule heat near the middle of the two electrodes is greater than the rest. With the increase in the current frequency, the current density distribution in the slag cell is basically unchanged. The current density inside the two electrodes increases obviously with the current frequency. When the current frequency increases from 10 Hz to 50 Hz, the maximum current density at the inner surface of the electrode increases by 14.7%. The current distribution at the lower side of the electrode in the slag pool is relatively uniform, and the current density in this region decreases with the increase in the height of the slag pool and the increase in the depth of the electrode inserted into the slag pool.

Perception of Specific Musical Attributes in Dependence of the Insertion Depth of Cochlear Implant Electrodes Using the Montreal Battery of Evaluation of Amusia.

The insertion angle of the electrode array has an influence on the perception of different musical features. A deeper insertion of the electrodes is associated with a greater coverage of the cochlea with possible stimulus locations. This could lead to an improved or extended perception of pitches and pitch changes as well as to a better perception of contours in musical pieces. A Montreal Battery of Evaluation of Amusia test battery was conducted with a collective of 19 cochlear implant (CI) users and 9 normal-hearing subjects. For the CI users, the insertion angles of the intracochlear electrode arrays were calculated using Otoplan software. Compared with normal-hearing users, CI users performed worse in the detection of melodic features of music. CI users performed better with temporal features than with melodic features. An influence of the insertion depth of the electrodes on the results of the Montreal Battery of Evaluation of Amusia could be proven neither for Cochlear nor for MED-EL CI users. Deeper insertion of electrode arrays may only better approximate the spatial-frequency map. Alone, it does not have an effect on better detection and identification of pitch and tonality and, consequently, better perception of musical attributes. Anatomy-based calculation of electrode locations and matching to characteristic frequencies will be sought in subsequent studies.

Cochlear Implantation in Children with Meningitis: A Multicenter Study on Auditory Performance and Speech Production Outcomes.

This study aims to evaluate speech production outcomes and auditory performance in children with post-meningitis deafness who were treated with cochlear implants. Additionally, the study assesses the impact of electrode insertion depth on surgical outcomes.". We conducted a study on 66 pediatric patients with bilateral postmeningitis hearing loss who were being prepared for cochlear implantation at four tertiary referral academic institutions. The speech intelligibility rating (SIR) and categories of auditory performance (CAP) were evaluated after the first and second years following implantation. The patients were divided into two groups based on electrode insertion depth: one group had full electrode insertion (more than two-thirds), while the other had partial electrode insertion (less than two-thirds). We compared the SIR and CAP scores between the two groups to assess the impact of electrode insertion depth on outcomes. Before implantation, the median CAP score was one, but it improved significantly to six within two years after the procedure (P-value < 0.001). Similarly, the median SIR score before implantation was one, but it improved significantly to three within two years after surgery (P-value < 0.001). However, there was no significant difference between the partial and full electrode insertion groups in terms of CAP and SIR scores during the follow-up evaluations conducted after the first and second years. The study found that cochlear implantation significantly improved speech production skills and auditory performance in children with postmeningitis deafness. Importantly, the amount of electrode insertion at the time of implantation did not have a significant impact on the outcomes.

Computed tomography in measuring electrode insertion angle and depth for cricopharyngeal muscle electromyography.

Electromyography of the cricopharyngeal muscle (CP-EMG) is one of many assessment tools for dysphagia. The key to performing EMG and BTX injections is to precisely locate the cricopharyngeal muscle with an electrode. One of the main difficulties of electrode insertion is the fact that the CP muscle is located deep within the neck. Since a neck computed tomography (CT) can clearly display the CP muscle, thyroid, and blood vessels in the neck, we speculate that a safe concentric needle electrode insertion path to the cricopharyngeal muscle can be simulated with the assistance of the patient's neck CT which clearly marks the angle and depth of concentric needle electrode insertion. The purpose of this study was to explore simulated electrode insertion angles and insertion depths for cricopharyngeal electromyography based on retrospective CT data and present a method of percutaneous localization of the cricopharyngeal muscle based on CT images of the neck. One hundred and forty-three neck CT scans performed between January 2019 and November 2020 were included in this study. With the assistance of the angle and straight-line tools found in the Advantage Workstation 4.4 (GE, HealthCare), simulated insertion angles and depths from the anterior border of the sternocleidomastoid muscle to the cricopharyngeal muscle were obtained. The 143 CT images originated from participants that included 63 males (44.1%) with an average age of 46.2±13.9 years old. The insertion angle, insertion depth, and neck thickness measured on the CT images were 53.2±10.7˚, 24.2±4.1 mm, and 130.1±17.7 mm, respectively. The insertion angle and depth were significantly greater in males than in females (P<0.05), and the insertion angle increased with the age of participants (P<0.05). A generalized linear model (GLM) showed that insertion angle was positively correlated with neck thickness (β=0.14; 95% CI: 0.03 to 0.25) and gender (β=5.08; 95% CI: 1.31 to 8.85), and negatively correlated with age (β=-5.88; 95% CI: -9.54 to -1.62). Insertion depth was only positively correlated with the neck thickness (β=0.11; 95% CI: 0.07 to 0.15). This study indicates that age, gender, and neck thickness are influencing factors for insertion angle, while neck thickness is the influencing factor for insertion depth. The simulated concentric needle electrode insertion method based on CT can assist clinical operation to ensure safety and effectiveness of cricopharyngeal electromyography.

Preclinical evaluation of a tool for insertion force measurements in cochlear implant surgery

PurposeTrauma that may be inflicted to the inner ear (cochlea) during the insertion of an electrode array (EA) in cochlear implant (CI) surgery can significantly decrease the hearing outcome of patients with residual hearing. Interaction forces between the EA and the cochlea are a promising indicator for the likelihood of intracochlear trauma. However, insertion forces have only been measured in laboratory setups. We recently developed a tool to measure the insertion force during CI surgery. Here, we present the first ex vivo evaluation of our tool with a focus on usability in the standard surgical workflow.MethodsTwo CI surgeons inserted commercially available EAs into three temporal bone specimens. The insertion force and the orientation of the tool were recorded together with camera footage. The surgeons answered a questionnaire after each insertion to evaluate the surgical workflow with respect to CI surgery.ResultsThe EA insertion using our tool was rated successful in all 18 trials. The surgical workflow was evaluated to be equivalent to standard CI surgery. Minor handling challenges can be overcome through surgeon training. The peak insertion forces were 62.4 mN ± 26.7 mN on average. Peak forces significantly correlated to the final electrode insertion depth, supporting the assumption that the measured forces mainly correspond to intracochlear events and not extracochlear friction. Gravity-induced forces of up to 28.8 mN were removed from the signal, illustrating the importance of the compensation of such forces in manual surgery.ConclusionThe results show that the tool is ready for intraoperative use. In vivo insertion force data will improve the interpretability of experimental results in laboratory settings. The implementation of live insertion force feedback to surgeons could further improve residual hearing preservation.

Postoperative Impedance-Based Estimation of Cochlear Implant Electrode Insertion Depth.

Reliable determination of cochlear implant electrode positions shows promise for clinical applications, including anatomy-based fitting of audio processors or monitoring of electrode migration during follow-up. Currently, electrode positioning is measured using radiography. The primary objective of this study is to extend and validate an impedance-based method for estimating electrode insertion depths, which could serve as a radiation-free and cost-effective alternative to radiography. The secondary objective is to evaluate the reliability of the estimation method in the postoperative follow-up over several months. The ground truth insertion depths were measured from postoperative computed tomography scans obtained from the records of 56 cases with an identical lateral wall electrode array. For each of these cases, impedance telemetry records were retrieved starting from the day of implantation up to a maximum observation period of 60 mo. Based on these recordings, the linear and angular electrode insertion depths were estimated using a phenomenological model. The estimates obtained were compared with the ground truth values to calculate the accuracy of the model. Analysis of the long-term recordings using a linear mixed-effects model showed that postoperative tissue resistances remained stable throughout the follow-up period, except for the two most basal electrodes, which increased significantly over time (electrode 11: ~10 Ω/year, electrode 12: ~30 Ω/year). Inferred phenomenological models from early and late impedance telemetry recordings were not different. The insertion depth of all electrodes was estimated with an absolute error of 0.9 mm ± 0.6 mm or 22° ± 18° angle (mean ± SD). Insertion depth estimations of the model were reliable over time when comparing two postoperative computed tomography scans of the same ear. Our results confirm that the impedance-based position estimation method can be applied to postoperative impedance telemetry recordings. Future work needs to address extracochlear electrode detection to increase the performance of the method.

Imaging-based frequency mapping for cochlear implants - Evaluated using a daily randomized controlled trial.

Due to variation in electrode design, insertion depth and cochlear morphology, patients with a cochlear implant (CI) often have to adapt to a substantial mismatch between the characteristic response frequencies of cochlear neurons and the stimulus frequencies assigned to electrode contacts. We introduce an imaging-based fitting intervention, which aimed to reduce frequency-to-place mismatch by aligning frequency mapping with the tonotopic position of electrodes. Results were evaluated in a novel trial set-up where subjects crossed over between intervention and control using a daily within-patient randomized approach, immediately from the start of CI rehabilitation. Fourteen adult participants were included in this single-blinded, daily randomized clinical trial. Based on a fusion of pre-operative imaging and a post-operative cone beam CT scan (CBCT), mapping of electrical input was aligned to natural place-pitch arrangement in the individual cochlea. That is, adjustments to the CI's frequency allocation table were made so electrical stimulation of frequencies matched as closely as possible with corresponding acoustic locations in the cochlea. For a period of three months, starting at first fit, a scheme was implemented whereby the blinded subject crossed over between the experimental and standard fitting program using a daily randomized wearing schedule, and thus effectively acted as their own control. Speech outcomes (such as speech intelligibility in quiet and noise, sound quality and listening effort) were measured with both settings throughout the study period. On a group level, standard fitting obtained subject preference and showed superior results in all outcome measures. In contrast, two out of fourteen subjects preferred the imaging-based fitting and correspondingly had better speech understanding with this setting compared to standard fitting. On average, cochlear implant fitting based on individual tonotopy did not elicit higher speech intelligibility but variability in individual results strengthen the potential for individualized frequency fitting. The novel trial design proved to be a suitable method for evaluation of experimental interventions in a prospective trial setup with cochlear implants.

Comparison of Perioperative Electrophysiological Measurements and Postoperative Results in Cochlear Implantation with a Slim Straight Electrode

This research aims to determine whether a neural response telemetry (NRT) threshold determines the success of surgery. Furthermore, we examined whether the patient’s age, the etiology of their hearing loss, the depth of the electrode insertion, and a slow electrode insertion affect the result of postoperative speech audiometry (PSA). A total of 23 patients that had operations in a tertiary medical centre were included in the research. All of them received a slim straight electrode that was inserted through the round window into the lateral part of scala tympani The duration of the insertion was consistently 2 min in 52.2% and less than 2 min in 47.8% of cases. Statistical analyses were performed in the IBM SPSSTM program. Patients that were diagnosed with sensorineural hearing loss (SNHL) had statistically lower average NRT threshold values in comparison to patients diagnosed with otosclerosis (t = 3.069; p = 0.034). The depth of electrode insertion is inversely proportional to the average of all NRT thresholds (r = −0.464; p = 0.026). No correlation was found between slow electrode insertion and postoperative average values of tone audiometry (U = 44.000; p = 0.300). No statistically significant correlation could be drawn between the average of all NRT thresholds and postoperative speech audiometry (rho = −0.070; p = 0.751).

Effect of interaural electrode insertion depth difference and independent band selection on sentence recognition in noise and spatial release from masking in simulated bilateral cochlear implant listening

PurposeInter-aural insertion depth difference (IEDD) in bilateral cochlear implant (BiCI) with continuous interleaved sampling (CIS) processing is known to reduce the recognition of speech in noise and spatial release from masking (SRM). However, the independent channel selection in the ‘n-of-m’ sound coding strategy might have a different effect on speech recognition and SRM when compared to the effects of IEDD in CIS-based findings. This study aimed to investigate the effect of bilateral ‘n-of-m’ processing strategy and interaural electrode insertion depth difference on speech recognition in noise and SRM under conditions that simulated bilateral cochlear implant listening.MethodsFive young adults with normal hearing sensitivity participated in the study. The target sentences were spatially filtered to originate from 0° and the masker was spatially filtered at 0°, 15°, 37.5°, and 90° using the Oldenburg head-related transfer function database for behind the ear microphone. A 22-channel sine wave vocoder processing based on ‘n-of-m’ processing was applied to the spatialized target-masker mixture, in each ear. The perceptual experiment involved a test of speech recognition in noise under one co-located condition (target and masker at 0°) and three spatially separated conditions (target at 0°, masker at 15°, 37.5°, or 90° to the right ear).ResultsThe results were analyzed using a three-way repeated measure analysis of variance (ANOVA). The effect of interaural insertion depth difference (F (2,8) = 3.145, p = 0.098, ɳ2 = 0.007) and spatial separation between target and masker (F (3,12) = 1.239, p = 0.339, ɳ2 = 0.004) on speech recognition in noise was not significant.ConclusionsSpeech recognition in noise and SRM were not affected by IEDD ≤ 3 mm. Bilateral ‘n-of-m’ processing resulted in reduced speech recognition in noise and SRM.

Cochlear Implantation in Children with Congenital Inner Ear Malformations

AbstractBackground: Cochlear Implantation has proven beneficial in patients with profound congenital hearing impairments. Performing cochlear implantation in patients with inner ear malformation has always been a matter of dispute as congenital deaf ears may have anatomical malformations and difficulties during operation, it is important to focus on problems and complications that may face the surgeon who is performing this operation.Objective: Evaluate the problems and surgical difficulties encountered in patients with congenital inner ear malformation, who underwent cochlear implantation.Patients and methods: A series of 21 pediatric cochlear implant (CI) patients with known inner ear malformations determined on computed tomography (CT) of the temporal bone who underwent cochlear implantation in the department of otolaryngology in Hospital Martyr Ghazi Al-Hariri and AL-Yarmouk Teaching Hospital, Baghdad, Iraq, during the period from January 2018 to January 2021 were the subjects of the study to determine intraoperative adverse effects of these anomalies regarding electrode array insertion depths, predisposition to cerebrospinal fluid (CSF) leak through the cochleostomy, and associated facial nerve anomalies that can create access problems for scala tympani.Results: The most common inner ear anomalies were wide vestibular aqueduct (15) patients with percentage of (71.4%), incomplete partitions (5) patients with percentage of (23.8%), and common cavity (1) patient with percentage of (4.8%). CSF leak, the most common was CSF ooze (11) patients with percentage of (52.4%), CSF gusher seen in (6) patients (28.6%), and no CSF leak in (4) patients (19%). Facial nerve anomalies, only one case has abnormal position (more superficial and not injured) with a percentage of (4.8%), while in 20 patients (95.2%) no anomaly was detected. Electrode insertion depth, full insertion was achieved in (17) patients with percentage of (81%), while incomplete insertion was occurred in (4) patients (19%).Conclusion: Cochlear implant can be successfully and safely done in patients with selected congenital inner ear anomalies. Surgery can be challenging in certain cases of gusher and facial nerve abnormalities, but proper radiology and good surgical technique will help avoid complications. Keywords: Cochlear Implantation, Congenital inner ear malformation, facial nerve anomalies.

How far the zone of heat-induced transient block extends beyond the lesion during RF catheter cardiac ablation

Purpose While radiofrequency catheter ablation (RFCA) creates a lesion consisting of the tissue points subjected to lethal heating, the sublethal heating (SH) undergone by the surrounding tissue can cause transient electrophysiological block. The size of the zone of heat-induced transient block (HiTB) has not been quantified to date. Our objective was to use computer modeling to provide an initial estimate. Methods and materials We used previous experimental data together with the Arrhenius damage index (Ω) to fix the Ω values that delineate this zone: a lower limit of 0.1–0.4 and upper limit of 1.0 (lesion boundary). An RFCA computer model was used with different power-duration settings, catheter positions and electrode insertion depths, together with dispersion of the tissue’s electrical and thermal characteristics. Results The HiTB zone extends in depth to a minimum and maximum distance of 0.5 mm and 2 mm beyond the lesion limit, respectively, while its maximum width varies with the energy delivered, extending to a minimum of 0.6 mm and a maximum of 2.5 mm beyond the lesion, reaching 3.5 mm when high energy settings are used (25 W–20s, 500 J). The dispersion of the tissue’s thermal and electrical characteristics affects the size of the HiTB zone by ±0.3 mm in depth and ±0.5 mm in maximum width. Conclusions Our results suggest that the size of the zone of heat-induced transient block during RFCA could extend beyond the lesion limit by a maximum of 2 mm in depth and approximately 2.5 mm in width.

Numerical Simulation of Multi-Physics Fields in Fused Magnesia Furnace

In this paper, a 3D transient multi-physical field model is developed to capture the complex processes inside a fused magnesia furnace. The multi-physics model integrates electromagnetism, thermodynamics, decomposition reactions, and flow. The three-phase submerged magnesia furnace includes an arc, magnesite ores, a melting pool, and a solidification ingot. For a more comprehensive analysis of the optimal design of industrial operations, the influence of the key index of electrode insertion depth on temperature and reaction is also discussed. The results show that the current density in the fused magnesia furnace is almost the same as the joule heat distribution, and there is an obvious area of low energy density affected by the skin effect, which leads to the waste of electric energy. The temperature at the center of the arc reaches 12,000 K, and the plasma areas formed at the end of the three electrodes are connected to each other to form a closed current path, which provides energy for the process of melting magnesia. The arc region is an ellipsoid with a length of ~30 mm and a diameter of ~49 mm. The decomposition reaction of magnesite mainly occurs in the arc area, and the radiation heat provided by the high-temperature arc is used as the heat source. There is almost no magnesite in the molten pool, and the molten pool only provides energy for the melting process of magnesia. When the electrode insertion depth is 0.4, 0.5, 0.6, and 0.7 m, the arc length is 0.049 m, 0.066 m, 0.068 m, and 0.059 m, respectively. According to the simulation results, there is an optimal electrode insertion depth.

Comorbidity associated with worse outcomes in a population of limited cochlear implant performers.

Most patients significantly benefit from cochlear implantation (CI). However, speech understanding varies widely, with a small proportion of patients demonstrating limited audiometric outcomes. While there are well-documented determinants of poor performance, there remains a cohort of patients that do not meet expected outcomes. Preoperative prognostication is desirable to manage expectations, ensure value of the intervention, and reduce risk. The objective of the study is to evaluate variables found within a single CI center's most limited functioning cohort following implantation. A retrospective review of a single CI program's cohort of (344 ears) patients implanted between 2011 and 2018 whose 1-year postimplantation AzBio scores fall 2 SDs below the mean was performed. Exclusion criteria includes skullbase pathology, pre/peri-lingual deafness, cochlear anatomic abnormalities, English as an additional language, and limited electrode insertion depth. Overall, 26 patients were identified. The study population's postimplantation net benefit AzBio score is 18% compared to the entire program's 47% (p< 0.05). This group is older (71.8 vs. 59.0 years, p< 0.05) with a longer duration of hearing loss (26.4 vs. 18.0 years, p< 0.05) and with a lower preoperative AzBio score [14% lower (p< 0.05)]. A host of medical conditions were identified in the subpopulation, with a trend towards significance in those suffering from either malignancy or cardiac condition. Escalating comorbid status was associated with worse performance (p< 0.05). Within a cohort of limited-performing CI users, benefit tended to decrease with escalating number of comorbid conditions. This information may serve to inform preoperative patient counseling. Level IV (evidence from a case control study).

Effects of tonotopic matching and spatial cues on segregation of competing speech in simulations of bilateral cochlear implants.

In the clinical fitting of cochlear implants (CIs), the lowest input acoustic frequency is typically much lower than the characteristic frequency associated with the most apical electrode position, due to the limited electrode insertion depth. For bilateral CI users, electrode positions may differ across ears. However, the same acoustic-to-electrode frequency allocation table (FAT) is typically assigned to both ears. As such, bilateral CI users may experience both intra-aural frequency mismatch within each ear and inter-aural mismatch across ears. This inter-aural mismatch may limit the ability of bilateral CI users to take advantage of spatial cues when attempting to segregate competing speech. Adjusting the FAT to tonotopically match the electrode position in each ear (i.e., increasing the low acoustic input frequency) is theorized to reduce this inter-aural mismatch. Unfortunately, this approach may also introduce the loss of acoustic information below the modified input acoustic frequency. The present study explored the trade-off between reduced inter-aural frequency mismatch and low-frequency information loss for segregation of competing speech. Normal-hearing participants were tested while listening to acoustic simulations of bilateral CIs. Speech reception thresholds (SRTs) were measured for target sentences produced by a male talker in the presence of two different male talkers. Masker speech was either co-located with or spatially separated from the target speech. The bilateral CI simulations were produced by 16-channel sinewave vocoders; the simulated insertion depth was fixed in one ear and varied in the other ear, resulting in an inter-aural mismatch of 0, 2, or 6 mm in terms of cochlear place. Two FAT conditions were compared: 1) clinical (200–8000 Hz in both ears), or 2) matched to the simulated insertion depth in each ear. Results showed that SRTs were significantly lower with the matched than with the clinical FAT, regardless of the insertion depth or spatial configuration of the masker speech. The largest improvement in SRTs with the matched FAT was observed when the inter-aural mismatch was largest (6 mm). These results suggest that minimizing inter-aural mismatch with tonotopically matched FATs may benefit bilateral CI users’ ability to segregate competing speech despite substantial low-frequency information loss in ears with shallow insertion depths.

Insertion Guidance Based on Impedance Measurements of a Cochlear Electrode Array.

The cochlear implantable neuromodulator provides substantial auditory perception to those with severe or profound impaired hearing. Correct electrode array positioning in the cochlea is one of the important factors for quality hearing, and misplacement may lead to additional injury to the cochlea. Visual inspection of the progress of electrode insertion is limited and mainly relies on the surgeon's tactile skills, and there is a need to detect in real-time the electrode array position in the cochlea during insertion. The available clinical measurement presently provides very limited information. Impedance measurement may be used to assist with the insertion of the electrode array. Using computational modeling of the cochlea, and its local tissue layers merging with the associated neuromodulator electrode array parameters, the impedance variations at different insertion depths and the proximities to the cochlea walls have been analyzed. In this study, an anatomical computational model of the temporal region of a patient is used to derive the relationship between impedance variations and the electrode proximity to the cochlea wall and electrode insertion depth. The aim was to examine whether the use of electrode impedance variations can be an effective marker of electrode proximity and electrode insertion depth. The proposed anatomical model simulates the quasi-static electrode impedance variations at different selected points but at considerable computation cost. A much less computationally intensive geometric model (~1/30) provided comparative impedance measurements with differences of <2%. Both use finite element analysis over the entire cross-section area of the scala tympani. It is shown that the magnitude of the impedance varies with both electrode insertion depth and electrode proximity to the adjacent anatomical layers (e.g., cochlea wall). In particular, there is a 1,400% increase when the electrode array is moved very close to the cochlea wall. This may help the surgeon to find the optimal electrode position within the scala tympani by observation of such impedance characteristics. The misplacement of the electrode array within the scala tympani may be eliminated by using the impedance variation metric during electrode array insertion if the results are validated with an experimental study.

Numerical simulation of the effect of electrode insertion depth on melting process of self‐supporting lining electric furnace

AbstractThis research is on the melting process of slag in non‐inner lining furnaces. In this electric furnace, slag is solidified into the lining of the inner wall during the melting process by means of water cooling of the outer wall. It is a self‐supporting lining electric furnace. In this study, the slag melting process was simulated using ANSYS software, and the electromagnetic field, temperature field, and furnace lining thickness of the self‐supporting lining were analyzed at different electrode insertion depths. The results show that the self‐supporting lining can be formed under the three insertion depth of the electrodes, and the thickness of the lining increases with the insertion depth of the electrode.