Intraindividual Comparison of Psychophysical Parameters Between Perimodiolar and Lateral-type Electrode Arrays in Patients With Bilateral Cochlear Implants
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Perimodiolar electrode arrays were developed to improve stimulation of specific neuronal populations and to decrease power consumption; however, they can damage the cochlear structure. We examined and compared psychophysical parameters of perimodiolar and lateral-type electrode arrays in patients who received a different type of bilateral cochlear implant (CI) in each ear.Retrospective analysis.Tertiary referral center.Eight child patients (three males, five females) received a different CI in each ear (perimodiolar array and lateral array). They received the CIs sequentially (n = 7) or simultaneously (n = 1).Diagnostic, therapeutic, and rehabilitative.Electrically evoked compound action potential, threshold level, comfort level, and dynamic range (DR) of the basal, mid, and apical electrodes were compared. We also surveyed battery consumption for each device.Electrically evoked compound action potential threshold, threshold level, and comfort level were lower for the perimodiolar-type electrode array than for the lateral-type electrode array in most patients. However, the DR for the perimodiolar array was narrower than for the lateral array. For most patients, there was little difference in battery life.Although the level of electrical energy required for auditory stimulation seems to be lower for the perimodiolar electrode array than for the laterally placed array, the DR was wider and the amount of battery consumption was similar. The electrode array should be chosen by considering various patient factors, such as residual hearing.Keywords:
Electrode array
Pitch perception for different modes of stimulation using the Cochlear multiple-electrode prosthesis
Numerical estimations of pitch were obtained from nine postlinguistically deafened adults using the 22-electrode cochlear implant manufactured by Cochlear Pty. Limited. A series of electrodes on the array were stimulated using three modes of stimulation: Bipolar (BP), common ground (CG), and monopolar (MONO). In BP stimulation, an electric current was passed between two electrodes separated by one electrode for eight patients and two electrodes for one patient. In CG stimulation, a single electrode was activated and the other electrodes on the array were connected together to serve as the return path for the current. In MONO stimulation, an electric current was passed between a single electrode and the most basal electrode on the array. Pitch estimations were generally consistent with the tonotopic organization of the cochlea. There was a marked reversal in pitch for electrodes in the middle of the array using CG stimulation for three patients. A reduced range of pitch using MONO stimulation was recorded for patients where the most basal electrode was internal to the cochlea. There were also individual differences in pitch estimations between the three modes of stimulation for most patients. The current levels required to elicit threshold (T) and comfortable listening (C) levels were, in general, higher for BP stimulation than for CG stimulation and were lowest for MONO stimulation. For CG stimulation, there was a tendency for T and C levels to be higher for electrodes in the middle of the array than at the basal or apical ends. For MONO stimulation, T and C levels uniformly increased in an apical to basal direction for the majority of patients. There was no consistent pattern in T and C levels for BP stimulation. The size of the range of usable hearing using CG stimulation tended to be similar to that using BP stimulation and was usually higher than that using MONO stimulation.
Tonotopy
Pitch perception
Basal (medicine)
Electrode array
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Cochlear implantation is the most successful approach for people with profound sensorineural hearing loss. Manual insertion of the electrode array may result in damaging the soft tissue structures and basilar membrane. An automated electrode array insertion device is reported to be less traumatic in cochlear implant surgery. Objectives The present work develops a simple, reliable, and compact device for automatically inserting the electrode array during cochlear implantation and test the device to observe intracochlear pressure during simulated electrode insertion. Methods The device actuates the electrode array by a roller mechanism. For testing the automated device, a straight cochlea having the dimension of the scala tympani and a model electrode is developed using a 3D printer. A pressure sensor is utilized to observe the pressure change at different insertional conditions. Results The electrode is inserted into a prototype cochlea at different speeds without any pause, and it is noticed that the pressure is increased with the depth of insertion of the electrode irrespective of the speed of electrode insertion. The rate of pressure change is observed to be increased exponentially with the speed of insertion. Conclusion At an insertion speed of 0.15 mm/s, the peak pressure is observed to be 133 Pa, which can be further evaluated in anatomical models for clinical scenarios. Level of Evidence N/A Laryngoscope , 134:1388–1395, 2024
Electrode array
Basilar membrane
Cochlear Implantation
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The intracochlear electrode array of cochlear implants is used to electrically stimulate the residual hearing auditory nerve of profound sensorineural hearing loss. The present products used to implant possess configuration with the different contact style and different separation between the contacts. This study investigated the effects of electrode configuration on the auditory nerve compound action potentials in response to electric stimulation. We also investigated the channel interaction of the different electrode configuration. Adult guinea pigs were used in acute experimental sessions. We implanted three kinds of electrode array either (1) a narrow spacing banded array consisting of a tapered silicone elastomer carrier with a linear series of banding contacts; or (2) two wider spacing arrays consisting of a tapered silicone elastomer carrier with oval-shaped contacts. The electrically evoked compound action potential (ECAP) was recorded from the intracochlear. ECAP latency functions indicated that the electrode array with narrow spacing and banded contacts generated shorter latency than the electrode array with wider spacing and oval-shaped contacts. We also observed that the electrode array with banded contacts had greater ECAP amplitude than the electrode with oval-shaped contacts.
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Cochlear nerve
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Electrode design and insertional depth-dependent intra-cochlear pressure changes: a model experiment
Abstract Background: Preservation of residual hearing is one of the major goals in modern cochlear implant surgery. Intra-cochlear fluid pressure changes influence residual hearing, and should be kept low before, during and after cochlear implant insertion. Methods: Experiments were performed in an artificial cochlear model. A pressure sensor was inserted in the apical part. Five insertions were performed on two electrode arrays. Each insertion was divided into three parts, and statistically evaluated in terms of pressure peak frequency and pressure peak amplitude. Results: The peak frequency over each third part of the electrode increased in both electrode arrays. A slight increase was seen in peak amplitude in the lateral wall electrode array, but not in the midscalar electrode array. Significant differences were found in the first third of both electrode arrays. Conclusion: The midscalar and lateral wall electrode arrays have different intra-cochlear fluid pressure changes associated with intra-cochlear placement, electrode characteristics and insertion.
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Cochlear implants provide functional hearing to people who are profoundly deaf or hearing impaired by replacing the function of missing inner hair cells with an array of stimulating electrodes. Previous studies developed a modeling framework for predicting the optimal number of electrodes, as well as the optimal locations and usage probabilities of electrodes, from an information theoretic perspective. However, the information theoretic method does not quantify the performance of electrode place discrimination. In this paper, we apply a so-called 'extreme-learning machine' to the cochlear implant model to calculate the electrode classification error rates. We also investigate the locations along the electrode array where errors are most likely to occur. We conclude based on our model that i) the classification error rate increases with increasing number of electrodes and the classification errors occur predominantly between adjacent electrodes, ii) by inserting the electrode array deeper into the cochlea, more electrode locations can be distinguished and the electrodes for which most errors occur are determined by the distance and spiral twirling angle between adjacent electrodes.
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Conclusion. The image quality of 64-MDCT provided excellent definition of the fine osseous structures and individual electrode contacts. Evaluation of electrode distances revealed a more focused stimulation for the Helix contacts, with better optimization of pulse width and frequency of stimulation. Objectives. A multi-slice CT scan was performed postoperatively to evaluate electrode distance from the modiolus and variability of fitting parameters (M level) for two different types of cochlear implant electrode carriers, CII and 90K implants with 1J and Helix electrode carriers. Materials and methods. The electrode's position in different cochlear implant (CI) electrodes, Advanced Bionics 90K 1J and Helix, was assessed postoperatively in 20 adult patients by means of a 64-MDCT scanner. Axial, coronal, and oblique 0.3 mm multiplanar reconstructions (MPRs) were obtained and datasets were analyzed to assess the intracochlear position and distance from the surface of the electrodes to the bony edge of the modiolus. Patients’ fitting characteristics were gathered at the time the CT was performed and correlated to intracochlear measurements. Results. Determination of contact distances confirmed smaller average values for the Helix at the apex and medial segments. Helix electrodes were closer to the modiolus in all segments. Likewise, M level determination showed lower values for the Helix carrier, confirming a more focused stimulation and better optimization of pulse width and frequency of stimulation.
Modiolus (cochlea)
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The degree of overlap among cochlear nerve fibers stimulated by different electrodes results in electrode interaction, which has been shown to have a significantly deleterious effect on speech recognition performance in multi-electrode cochlear implant users. The Nucleus CI24R(CS) Contour array, which lies substantially closer to the modiolus than the CI24M straight array, is expected to exhibit narrower excitation patterns. The neural response telemetry (NRT) 3.0 software provides a method of measuring the spread of neural excitation by presenting the masker and probe pulses on different intra-cochlear electrode bands. Nine pairs of children, using Nucleus CI24M/CI24R(CS) cochlear implants with a similar etiology and duration of deafness, insertion depth, age of implantation and loudest acceptable presentation level (LAPL) in NRT sessions, participated in the study. Profiles of the spread of neural excitation stimulated at the LAPL at 3 probe locations were examined for each pair of the 2 types of electrode array. The spread of neural excitation with respect to array type and location revealed significant effects (p < 0.001; p = 0.002) and no interaction between array type and probe location (p = 0.559). The results demonstrated that the Contour array improved electrode discrimination, especially for the electrodes at the basal end of the cochlea. The findings have implications for future electrode array design and current implant mapping strategies.
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Modiolus (cochlea)
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A cochlear implant is a surgically implanted device that helps to restore hearing for most severe hearing impaired patients. During the first 2–3 weeks after implantation of a cochlear implant electrode array, the electrical impedance at the electrode contacts increases. This increase is typically explained by the formation of fibrous tissue around the electrode array. To improve the electrode nerve interface in these patients, it is aimed at a reduction of tissue formation around the electrode array after implantation. Previously we have demonstrated that nanostructuring of platinum surfaces can inhibit fibroblast growth in vitro . In the current study we generated nanostructures directly on the surfaces of cochlear implant electrodes and tested their potential to reduce connective tissue formation around the electrode array in vivo by means of electrophysiological measurements. Guinea pigs were implanted with unstructured control or surface structured electrode arrays for 4 weeks. Impedance measurements were performed during the first 2 weeks daily, later weekly. Recorded impedances were typically lower for surface functionalized electrodes. Nanostructuring of the surface of the stimulating contacts of CI electrodes additionally resulted in a delayed increase in impedance showing that this modification has the potential for in vivo applications.
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Abstract: The stimulation electrodes of cochlear implants are covered by a lymph liquid with high electrical conductivity, which causes the transmitted information to be reduced by channel interaction. Even if this problem were solved, the stimulation regions may be discrete; therefore, there may be regions in which the electrode array cannot stimulate selectively. To solve these problems, we proposed a new auditory nerve stimulation method which we call the tripolar electrode stimulation method for cochlear implants. Our method stimulates using 3 adjacent electrodes selected from among the electrodes of the electrode array. The center electrode receives the currents emitted from the electrodes on both sides. We conducted animal experiments using this method. On the basis of the results we obtained, we concluded that our method may succeed in narrowing the stimulation region and continuously moving the stimulation site.
Cochlear Implantation
Neural Prosthesis
Nerve stimulation
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Electrode array
Multielectrode array
Bidomain model
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