Development and Clinical Introduction of the Nurotron Cochlear Implant Electrode Array

Clinical experience with the Nurotron™ cochlear implant in a Spanish-speaking postlingual population: Clinical safety and audiological results

OBJECTIVE

to assess clinical safety and postoperative audiological outcomes in postlingual deafness Spanish speaking patients, who underwent surgery with Nurotron™ cochlear implant.

MATERIAL AND METHODS

Retrospective descriptive case series study. We performed follow-up of complications and audiological measurements before and after cochlear implantation. Patients with bilateral severe to profound sensorineural hearing loss or patients with unilateral deafness with/without tinnitus were included. Repeated-measures within-subjects for assess pure tone thresholds and speech performance (bilingual test) with a detailed monitoring to establish security or adverse effects were performed. Analysis of variance tests, repetitive measures, were used for statistical analysis.

RESULTS

31 patients were included, 17 (54.8%) men and 14 (45.2%) women. Mean age at the time of surgery was 49.82 ± 18.8 years. The mean follow-up of the group was 31.56 ± 9.57 months (minimum = 19.6 months and maximum = 52.50 months). As major complication one patient (3.23%) had a hard failure that required removal and re-implantation. 25.8% of the patients presented minor complications, the most frequent being vertigo/unsteadiness in 22.6%. The mean of language discrimination (free field at 65 dB SPL) was 62.19% ± 16.66; being 69.82% ± 7.35 in the group of severe to profound bilateral sensorineural hearing loss. A statistically significant reduction was observed in patients with tinnitus, assessed using the visual analogue scale, preoperative = 7.2 ± 1,6 vs postoperative (18months postoperative) = 1.7 ± 1.3 (p < .001).

CONCLUSIONS

The Nurotron™ cochlear implant shows satisfactory audiological results, in accordance with what has been reported in the literature. Minor complications were similar to previous studies, but the percentage of hard failure should continue to be observed, which was higher than other reports with comparable follow-up.

A 10-year in-depth follow-up of post-lingual hearing loss patients with Chinese domestic cochlear implants

BACKGROUND

Follow-up of cochlear implant effectiveness is mainly focused on 3 years postoperatively, and studies with more than 5 years of observation are rare, especially for local Chinese brands.

OBJECTIVES

Nurotron (Chinese domestic cochlear implant brand) CI recipients who participated in the clinical trial in 2009 were followed-up for 10 years prospectively, providing data to guide doctors and patients.

MATERIAL AND METHODS

From December 2009 to April 2010, 57 subjects underwent Nurotron Venus CI surgery at multiple-centers, and were continued to be followed up and assessed at 1, 2, 3, 4, 5, and 10 years after switch on.

RESULTS

All recipients were successfully implanted with CIs with no difficulty in subsequent use with one reported case of re-implantation at 9 years after implantation. The aided hearing thresholds were significantly improved at one month after switch on (p < 0.0001) and remained stable afterwards for 10 years. Speech recognition scores were significantly higher than pre-operative results (p < 0.05) and continued to improve till 3 years after switch on. At 10 years post-operation, most subjects had improved QOL scores in most sub-items.

CONCLUSIONS AND SIGNIFICANCE

Nurotron Venus CI System provides long-term, stable results in hearing speech assistance capabilities and can improve the quality of life of CI recipients.

Development of a miniaturized, reconnectable, and implantable multichannel connector

Objective. Connectors for implantable neural prosthetic systems provide several advantages such as simplification of surgery, safe replacement of implanted devices, and modular design of the implant systems. With the rapid advancement of technologies for neural implants, miniaturized multichannel implantable connectors are also required. In this study, we propose a reconnectable and area-efficient multichannel implantable connector.Approach. A female-to-female adapter was fabricated using the thermal-press bonding of micropatterned liquid crystal polymer films. A bump inside the adapter enabled a reliable electrical connection by increasing the contact pressure between the contact pads of the adapter and the inserted cable. After connection, the adapter is enclosed in a metal case sealed with silicone elastomer packing. With different sizes of the packings, leakage current tests were performed under accelerated conditions to determine the optimal design for long-term reliability. Repeated connection tests were performed to verify the durability and reconnectability of the fabricated connector. The connector was implanted in rats, and the leakage currents were monitored to evaluate the stability of the connectorin vivo. Main results. The fabricated four- and eight-channel implantable connectors, assembled with the metal cases, had a diameter and length of 6 and 17 mm, respectively. Further, the contact resistances of the four- and eight-channel connectors were 53.2 and 75.2 mΩ, respectively. The electrical contact remained stable during repeated connection tests (50 times). The fabricated connectors with packings having 125%, 137%, and 150% volume ratios to the internal space of the metal case failed after 14, 88, and 14 d, respectively, in a 75 °C saline environment. In animal tests with rats, the connector maintained low leakage current levels for up to 92 d.Significance. An implantable and reconnectable multichannel connector was developed and evaluated. The feasibility of the proposed connector was evaluated in terms of electrical and mechanical characteristics as well as sealing performance. The proposed connector is expected to have potential applications in implantable neural prosthetic systems.

Robot-Assisted Electrode Array Insertion Becomes Available in Pediatric Cochlear Implant Recipients: First Report and an Intra-Individual Study

Background: As an advanced surgical technique to reduce trauma to the inner ear, robot-assisted electrode array (EA) insertion has been applied in adult cochlear implantation (CI) and was approved as a safe surgical procedure that could result in better outcomes. As the mastoid and temporal bones are generally smaller in children, which would increase the difficulty for robot-assisted manipulation, the clinical application of these systems for CI in children has not been reported. Given that the pediatric candidate is the main population, we aim to investigate the safety and reliability of robot-assisted techniques in pediatric cochlear implantation.

Methods: Retrospective cohort study at a referral center in Shanghai including all patients of simultaneous bilateral CI with robotic assistance on one side (RobOtol® system, Collin ORL, Bagneux, France), and manual insertion on the other (same brand of EA and CI in both side), from December 2019 to June 2020. The surgical outcomes, radiological measurements (EA positioning, EA insertion depth, mastoidectomy size), and audiological outcomes (Behavior pure-tone audiometry) were evaluated.

Results: Five infants (17.8 ± 13.5 months, ranging from 10 to 42 months) and an adult (39 years old) were enrolled in this study. Both perimodiolar and lateral wall EAs were included. The robot-assisted EA insertion was successfully performed in all cases, although the surgical zone in infants was about half the size in adults, and no difference was observed in mastoidectomy size between robot-assisted and manual insertion sides (p = 0.219). The insertion depths of EA with two techniques were similar (P = 0.583). The robot-assisted technique showed no scalar deviation, but scalar deviation occurred for one manually inserted pre-curved EA (16%). Early auditory performance was similar to both techniques.

Conclusion: Robot-assisted technique for EA insertion is approved to be used safely and reliably in children, which is possible and potential for better scalar positioning and might improve long-term auditory outcome. Standard mastoidectomy size was enough for robot-assisted technique. This first study marks the arrival of the era of robotic CI for all ages.

A Cross-Language Comparison of Sentence Recognition Using American English and Mandarin Chinese HINT and AzBio Sentences

OBJECTIVES

The aim of this study was to perform a cross-language comparison of two commonly used sentence-recognition materials (i.e., Hearing in Noise Test [HINT] and AzBio) in American English (AE) and Mandarin Chinese (MC).

DESIGNS

Sixty normal-hearing, native English-speaking and 60 normal-hearing, native Chinese-speaking young adults were recruited to participate in three experiments. In each experiment, the subjects were tested in their native language. In experiments I and II, noise and tone vocoders were used to process the HINT and AzBio sentences, respectively. The number of channels varied from 1 to 9, with an envelope cutoff frequency of 160 Hz. In experiment III, the AE AzBio and the MC HINT sentences were tested in speech-shaped noise at various signal to noise ratios (i.e., -20, -15, -10, -5, and 0 dB). The performance-intensity functions of sentence recognition using the two sets of sentence materials were compared.

RESULTS

Results of experiments I and II using vocoder processing indicated that the AE and MC versions of HINT and AzBio sentences differed in level of difficulty. The AE version yielded higher recognition performance than the MC version for both HINT and AzBio sentences. The type of vocoder processing (i.e., tone and noise vocoders) produced little differences in sentence-recognition performance in both languages. Incidentally, the AE AzBio sentences and the MC HINT sentences had similar recognition performance under vocoder processing. Such similarity was further confirmed under noise conditions in experiment III, where the performance-intensity functions of the two sets of sentences were closely matched.

CONCLUSIONS

The HINT and AzBio sentence materials developed in AE and MC differ in level of difficulty. The AE AzBio and the MC HINT sentence materials are similar in level of difficulty. In cross-language comparative research, the MC HINT and the AE AzBio sentences should be chosen for the respective language as the target sentence-recognition test materials.

A New Approach for Noise Suppression in Cochlear Implants: A Single-Channel Noise Reduction Algorithm

The cochlea “translates” the in-air vibrational acoustic “language” into the spikes of neural “language” that are then transmitted to the brain for auditory understanding and/or perception. During this intracochlear “translation” process, high resolution in time–frequency–intensity domains guarantees the high quality of the input neural information for the brain, which is vital for our outstanding hearing abilities. However, cochlear implants (CIs) have coarse artificial coding and interfaces, and CI users experience more challenges in common acoustic environments than their normal-hearing (NH) peers. Noise from sound sources that a listener has no interest in may be neglected by NH listeners, but they may distract a CI user. We discuss the CI noise-suppression techniques and introduce noise management for a new implant system. The monaural signal-to-noise ratio estimation-based noise suppression algorithm “eVoice,” which is incorporated in the processors of Nurotron^® Enduro^TM, was evaluated in two speech perception experiments. The results show that speech intelligibility in stationary speech-shaped noise can be significantly improved with eVoice. Similar results have been observed in other CI devices with single-channel noise reduction techniques. Specifically, the mean speech reception threshold decrease in the present study was 2.2 dB. The Nurotron society already has more than 10,000 users, and eVoice is a start for noise management in the new system. Future steps on non-stationary-noise suppression, spatial-source separation, bilateral hearing, microphone configuration, and environment specification are warranted. The existing evidence, including our research, suggests that noise-suppression techniques should be applied in CI systems. The artificial hearing of CI listeners requires more advanced signal processing techniques to reduce brain effort and increase intelligibility in noisy settings.