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

OBJECTIVES: 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. DESIGN: 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. RESULTS: 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). CONCLUSIONS: 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.

Clinical impact of manual scoring of peripheral arterial tonometry in patients with sleep apnea.

PURPOSE: The objective was to analyze the clinical implications of manual scoring of sleep studies using peripheral arterial tonometry (PAT) and to compare the manual and automated scoring algorithms. METHODS: Patients with suspected sleep-disordered breathing underwent sleep studies using PAT. The recordings were analyzed using a validated automated computer-based scoring and a novel manual scoring algorithm. The two methods were compared regarding sleep stages and respiratory events. RESULTS: Recordings of 130 patients were compared. The sleep stages and time were not significantly different between the scoring methods. PAT-derived apnea-hypopnea index (pAHI) was on average 8.4 events/h lower in the manually scored data (27.5±17.4/h vs.19.1±15.2/h, p<0.001). The OSA severity classification decreased in 66 (51%) of 130 recordings. A similar effect was found for the PAT-derived respiratory disturbance index with a reduction from 31.2±16.5/h to 21.7±14.4/h (p<0.001), for automated and manual scoring, respectively. A lower pAHI for manual scoring was found in all body positions and sleep stages and was independent of gender and body mass index. The absolute difference of pAHI increased with sleep apnea severity, while the relative difference decreased. Pearson's correlation coefficient between pAHI and oxygen desaturation index (ODI) significantly improved from 0.89 to 0.94 with manual scoring (p<0.001). CONCLUSIONS: Manual scoring results in a lower pAHI while improving the correlation to ODI. With manual scoring, the OSA category decreases in a clinically relevant proportion of patients. Sleep stages and time do not change significantly with manual scoring. In the authors' opinion, manual oversight is recommended if clinical decisions are likely to change.

Performance with a new bone conduction implant audio processor in patients with single-sided deafness.

PURPOSE: The SAMBA 2 BB audio processor for the BONEBRIDGE bone conduction implant features a new automatic listening environment detection to focus on target speech and to reduce interfering speech and background noises. The aim of this study was to evaluate the audiological benefit of the SAMBA 2 BB (AP2) and to compare it with its predecessor SAMBA BB (AP1). METHODS: Prospective within-subject comparison study. We compared the aided sound field hearing thresholds, speech understanding in quiet (Freiburg monosyllables), and speech understanding in noise (Oldenburg sentence test) with the AP1 and AP2. Each audio processor was worn for 2 weeks before assessment and seven users with single-sided sensorineural deafness (SSD) participated in the study. For speech understanding in noise, two complex noise scenarios with multiple noise sources including single talker interfering speech were used. The first scenario included speech presented from the front (S0NMIX), while in the second scenario speech was presented from the side of the implanted ear (SIPSINMIX). In addition, subjective evaluation using the SSQ12, APSQ, and the BBSS questionnaires was performed. RESULTS: We found improved speech understanding in quiet with the AP2 compared to the AP1 aided condition (on average + 17%, p = 0.007). In both noise scenarios, the AP2 lead to improved speech reception thresholds by 1.2 dB (S0NMIX, p = 0.032) and 2.1 dB (SIPSINMIX, p = 0.048) compared to the AP1. The questionnaires revealed no statistically significant differences, except an improved APSQ usability score with the AP2. CONCLUSION: Clinicians can expect that patients with SSD will benefit from the SAMBA 2 BB by improved speech understanding in both quiet and in complex noise scenarios, when compared to the older SAMBA BB.

Assessment of jugular bulb variability based on 3D surface models: quantitative measurements and surgical implications.

PURPOSE: High-riding jugular bulbs (JBs) among other anatomical variations can limit surgical access during lateral skull base surgery or middle ear surgery and must be carefully assessed preoperatively. We reconstruct 3D surface models to evaluate recent JB classification systems and assess the variability in the JB and surrounding structures. METHODS: 3D surface models were reconstructed from 46 temporal bones from computed tomography scans. Two independent raters visually assessed the height of the JB in the 3D models. Distances between the round window and the JB dome were measured to evaluate the spacing of this area. Additional distances between landmarks on surrounding structures were measured and statistically analyzed to describe the anatomical variability between and within subjects. RESULTS: The visual classification revealed that 30% of the specimens had no JB, 63% a low JB, and 7% a high-riding JB. The measured mean distance from the round window to the jugular bulb ranges between 3.22 ± 0.97 mm and 10.34 ± 1.41 mm. The distance measurement (error rate 5%) was more accurate than the visual classification (error rate 15%). The variability of the JB was higher than for the surrounding structures. No systematic laterality was found for any structure. CONCLUSION: Qualitative analysis in 3D models can contribute to a better spatial orientation in the lateral skull base and, thereby, have important implications during planning of middle ear and lateral skull base surgery.

The effect of internet telephony and a cochlear implant accessory on mobile phone speech comprehension in cochlear implant users.

PURPOSE: In individuals with severe hearing loss, mobile phone communication is limited despite treatment with a cochlear implant (CI). The goal of this study is to identify the best communication practice for CI users by comparing speech comprehension of conventional mobile phone (GSM) calls, Voice over Internet Protocol (VoIP) calls, and the application of a wireless phone clip (WPC) accessory. METHODS: This study included 13 individuals (mean age 47.1  ± 17.3 years) with at least one CI. Frequency response and objective voice quality were tested for each device, transmission mode and the WPC. We measured speech comprehension using a smartphone for a GSM call with and without WPC as well as VoIP-calls with and without WPC at different levels of white background noise. RESULTS: Frequency responses of the WPC were limited (< 4 kHz); however, speech comprehension in a noisy environment was significantly improved compared to GSM. Speech comprehension was improved by 9-27% utilizing VoIP or WPC compared to GSM. WPC was superior in noisy environments (80 dB SPL broadband noise) compared to GSM. At lower background noise levels (50, 60, 70 dB SPL broadband noise), VoIP resulted in improved speech comprehension with and without WPC. Speech comprehension scores did not correlate with objective voice quality measurements. CONCLUSION: Speech comprehension was best with VoIP alone; however, accessories such as a WPC provide additional improvement in the presence of background noise. Mobile phone calls utilizing VoIP technology, with or without a WPC accessory, result in superior speech comprehension compared to GSM.

Using a cochlear implant processor as contralateral routing of signals device in unilateral cochlear implant recipients.

PURPOSE: In unilateral cochlear implant (CI) recipients, a contralateral routing of signals (CROS) device enables to receive auditory information from the unaided side. This study investigates the feasibility as well as subjective and objective benefits of using a CI processor as a CROS device in unilateral CI recipients. METHODS: This is a single-center, prospective cohort study. First, we tested the directionality of the CROS processor in an acoustic chamber. Second, we examined the difference of speech perception in quiet and in noise in ten unilateral CI recipients with and without the CROS processor. Third, subjective ratings with the CROS processor were evaluated according to the Client Oriented Scale of Improvement Questionnaire. RESULTS: There was a time delay between the two devices of 3 ms. Connection of the CROS processor led to a summation effect of 3 dB as well as a more constant amplification along all azimuths. Speech perception in quiet showed an increased word recognition score at 50 dB (mean improvement 7%). In noise, the head shadow effect could be mitigated with significant gain in speech perception (mean improvement 8.4 dB). This advantage was reversed in unfavorable listening situations, where the CROS device considerably amplified the noise (mean: - 4.8 dB). Subjectively, patients who did not normally wear a hearing aid on the non-CI side were satisfied with the CROS device. CONCLUSIONS: The connection and synchronization of a CI processor as a CROS device is technically feasible and the signal processing strategies of the device can be exploited. In contra-laterally unaided patients, a subjective benefit can be achieved when wearing the CROS processor.

Influence of head orientation and implantation site of a novel transcutaneous bone conduction implant on MRI metal artifact reduction sequence.

PURPOSE: The use of magnetic resonance imaging (MRI) is often limited in patients with auditory implants because of the presence of metallic components and magnets. The aim of this study was to evaluate the clinical usefulness of a customized MRI sequence for metal artifact suppression in patients with BONEBRIDGETM BCI 602 implants (MED-EL, Innsbruck, Austria), the successor of the BCI 601 model. METHODS: Using our in-house developed and customized metal artifact reduction sequence (SEMAC-VAT WARP), MRI artifacts were evaluated qualitatively and quantitatively. MRI sequences were performed with and without artifact reduction on two whole head specimens with and without the BCI 602 implant. In addition, the influence of two different implantation sites (mastoid versus retrosigmoid) and head orientation on artifact presence was investigated. RESULTS: Artifact volume was reduced by more than the 50%. Results were comparable with those obtained with the BCI 601, showing no significant differences in the dimensions of artifacts caused by the implant. CONCLUSION: SEMAC-VAT WARP was once more proved to be efficient at reducing metal artifacts on MR images. The dimensions of artifacts associated with the BCI 602 are not smaller than those caused by the BCI 601.

Pinna-Imitating Microphone Directionality Improves Sound Localization and Discrimination in Bilateral Cochlear Implant Users.

OBJECTIVES: To compare the sound-source localization, discrimination, and tracking performance of bilateral cochlear implant users with omnidirectional (OMNI) and pinna-imitating (PI) microphone directionality modes. DESIGN: Twelve experienced bilateral cochlear implant users participated in the study. Their audio processors were fitted with two different programs featuring either the OMNI or PI mode. Each subject performed static and dynamic sound field spatial hearing tests in the horizontal plane. The static tests consisted of an absolute sound localization test and a minimum audible angle test, which was measured at eight azimuth directions. Dynamic sound tracking ability was evaluated by the subject correctly indicating the direction of a moving stimulus along two circular paths around the subject. RESULTS: PI mode led to statistically significant sound localization and discrimination improvements. For static sound localization, the greatest benefit was a reduction in the number of front-back confusions. The front-back confusion rate was reduced from 47% with OMNI mode to 35% with PI mode (p = 0.03). The ability to discriminate sound sources straight to the sides (90° and 270° angle) was only possible with PI mode. The averaged minimum audible angle value for the 90° and 270° angle positions decreased from a 75.5° to a 37.7° angle when PI mode was used (p < 0.001). Furthermore, a non-significant trend towards an improvement in the ability to track moving sound sources was observed for both trajectories tested (p = 0.34 and p = 0.27). CONCLUSIONS: Our results demonstrate that PI mode can lead to improved spatial hearing performance in bilateral cochlear implant users, mainly as a consequence of improved front-back discrimination with PI mode.

Two-phase survey on the frequency of use and safety of MRI for hearing implant recipients.

PURPOSE: Magnetic resonance imaging (MRI) is often used to visualize and diagnose soft tissues. Hearing implant (HI) recipients are likely to require at least one MRI scan during their lifetime. However, the MRI scanner can interact with the implant magnet, resulting in complications for the HI recipient. This survey, which was conducted in two phases, aimed to evaluate the safety and performance of MRI scans for individuals with a HI manufactured by MED-EL (MED-EL GmbH, Innsbruck, Austria). METHODS: A survey was developed and distributed in two phases to HEARRING clinics to obtain information about the use of MRI for recipients of MED-EL devices. Phase 1 focused on how often MRI is used in diagnostic imaging of the head region of the cochlear implant (CI) recipients. Phase 2 collected safety information about MRI scans performed on HI recipients. RESULTS: 106 of the 126 MRI scans reported in this survey were performed at a field strength of 1.5 T, on HI recipients who wore the SYNCHRONY CI or SYNCHRONY ABI. The head and spine were the most frequently imaged regions. 123 of the 126 scans were performed without any complications; two HI recipients experienced discomfort/pain. One recipient required reimplantation after an MRI was performed using a scanner that had not been approved for that implant. There was only one case that required surgical removal of the implant to reduce the imaging artefact. CONCLUSION: Individuals with either a SYNCHRONY CI or SYNCHRONY ABI from MED-EL can safely undergo a 1.5 T MRI when it is performed according to the manufacturer's safety policies and procedures.

Adverse events associated with bone-conduction and middle-ear implants: a systematic review.

PURPOSE: To review types and frequencies of adverse events (AE) associated with bone-conduction hearing implants (BCHIs) and active middle-ear implants (aMEIs) as reported in the literature. METHODS: Cochrane, PubMed, and EMBASE libraries were searched for primary articles in English or German language that reported on adverse events following BCHI or aMEI implantation, included at least five patients and were published between 1996 and 2016. Study characteristics, demographics, and counts of adverse events were tabulated and analyzed within the R statistical programming environment. RESULTS: Following assessment of the reporting quality of adverse events, we present a brief guideline that potentially improves AE reporting in this field of research. For the full dataset, we summarize study-level adverse event frequencies in terms of ratio of events to ears (REE) by AE groups and by device. For a subset of studies, we also report cumulative incidence (risk) for minor- and major adverse-events by device and by device groups. CONCLUSIONS: Data analyzed in this review show that: (1) the reporting quality of adverse events associated with BCHI and aMEIs is often very low; (2) adverse events associated with BCHI and aMEIs are qualitatively different and not equally frequent among devices; (3) state-of-the-art implantable BCHIs and aMEIs are a safe treatment option for hearing loss.

MRI Metal Artifact Reduction Sequence for Auditory Implants: First Results with a Transcutaneous Bone Conduction Implant.

OBJECTIVE: Magnetic resonance imaging (MRI) is often limited in patients with auditory implants because of the presence of metallic components and magnets. The aim of this study was to evaluate the clinical usefulness of a customized MRI sequence for metal artifact suppression for patients with implants in the temporal bone region, specifically patients with a transcutaneous bone conduction implant. METHODS: Two whole head specimens were unilaterally implanted with a transcutaneous bone conduction implant. MRI examinations with and without a primarily self-build sequence (SEMAC-VAT WARP) for metal artifact suppression were performed. The diagnostic usefulness of the acquired MRI scans was rated independently by two neuroradiologists. The sequence was also used to acquire postimplantation follow-up MRI in a patient with a transcutaneous bone conduction implant. RESULTS: The customized SEMAC-VAT WARP sequence significantly improved the diagnostic usefulness of the postimplantation MRIs. The image acquisition time was 12 min and 20 s for the T1-weighted and 12 min and 12 s for the T2-weighted MRI. There was good agreement between the two blinded raters (Cohen's κ = 0.61, p < 0.001). CONCLUSION: The sequence for metal artifact reduction optimized in Bern enables MRI at 1.5 T in patients with active transcutaneous bone conduction implants without sacrificing diagnostic imaging quality. Particularly on the implanted side, imaging of intracranial and supra- and infratentorial brain pathologies is clinically more valuable than standard diagnostic MRI without any artifact reduction sequences.

Robotic cochlear implantation: feasibility of a multiport approach in an ex vivo model.

PURPOSE: A recent clinical trial has shown the feasibility of robotic cochlear implantation. The electrode was inserted through the robotically drilled tunnel and an additional access through the external auditory canal was created to provide for means of visualization and manipulation. To obviate the need for this additional access, the utilization of multiple robotically drilled tunnels targeting the round window has been proposed. The objective of this study was to assess the feasibility of electrode insertion through a robotic multiport approach. METHODS: In four ex vivo human head specimens (left side), four trajectories through the facial recess (2x) and the retrofacial and suprameatal region were planned and robotically drilled. Optimal three-port configurations were determined for each specimen by analyzing combinations of three of the four trajectories, where the three trajectories were used for the electrode, endoscopic visualization and manipulative assistance. Finally, electrode insertions were conducted through the optimal configurations. RESULTS: The electrodes could successfully be inserted, and the procedure sufficiently visualized through the facial recess drill tunnels in all specimens. Effective manipulative assistance for sealing the round window could be provided through the retrofacial tunnel. CONCLUSIONS: Electrode insertion through a robotic three-port approach is feasible. Drill tunnels through the facial recess for the electrode and endoscope allow for optimized insertion angles and sufficient visualization. Through a retrofacial tunnel effective manipulation for sealing is possible.

Acquisition of basic ear surgery skills: a randomized comparison between endoscopic and microscopic techniques.

BACKGROUND: Endoscopic ear surgery is gaining increasing popularity and has an important impact on teaching middle ear anatomy and basic surgical skills among residents and fellows. Due to the wide-angled views offered, the approach significantly differs from the established microscopic technique. This randomized study compares the acquisition of basic ear-surgery skills using the endoscopic and microscopic technique under standardized conditions. We aim to investigate the required surgical times, attempts and accidental damages to surrounding structures (errors) in surgeons with different training levels. METHODS: Final-year medical students (n = 9), residents (n = 14) and consultants (n = 10) from the Department of Otorhinolaryngology, Head and Neck Surgery at the University Hospital of Bern, Switzerland were enrolled in the present study. After randomization every participant had to complete a standard set of grasping and dissecting surgical tasks in a temporal bone model. After the first session the participants were crossed over to the other technique. RESULTS: Time required for completion of the surgical tasks was similar for both techniques, but highly dependent on the training status. A significant increase in the number of damages to the ossicular chain was observed with the microscopic as compared to the endoscopic technique (p < 0.001). Moreover, students beginning with the endoscopic technique showed an overall significantly lower amount of time to complete the tasks (p = 0.04). From the subjective feedback a preference towards the endoscopic technique mainly in medical students was observed. CONCLUSIONS: The endoscopic approach is useful and beneficial for teaching basic surgical skills, mainly by providing a reduction of damage to surrounding tissues with similar operating times for both techniques. Moreover, medical students performed significantly faster, when first taught in the endoscopic technique. Especially for young surgeons without previous training in ear surgery, the endoscope should be considered to improve surgical skills in the middle ear.

Directional Microphone Contralateral Routing of Signals in Cochlear Implant Users: A Within-Subjects Comparison.

OBJECTIVES: For medical or financial reasons, bilateral cochlear implantation is not always possible in bilaterally deafened patients. In such cases, a contralateral routing of signals (CROS) device could complement the monaural implant. The goal of our study was to compare the benefit of three different conditions: (1) unilateral cochlear implant (CI) alone, (2) unilateral CI complemented with a directional CROS microphone, and (3) bilateral CIs. DESIGN: Twelve bilateral experienced CI users were tested. Speech reception in noise and sound localization were measured in the three above-mentioned conditions. Patients evaluated which condition they presumed to be activated and the subjective benefit on a hearing scale. RESULTS: Compared with the unilateral CI condition, the additional CROS device provided significantly better speech intelligibility in noise when speech signals came from the front or side of the CROS microphone. Only small subjective improvement was observed. Bilateral-activated CIs further improved the hearing performance. This was the only condition where sound localization was possible. Subjective evaluation showed a clear preference for the bilateral CI treatment. CONCLUSIONS: In bilateral deafened patients, bilateral implantation is the most preferable form of treatment. However, patients with one implant only could benefit from an additional directional microphone CROS device.

Topographic bone thickness maps for Bonebridge implantations.

Bonebridge™ (BB) implantation relies on optimal anchoring of the bone-conduction implant in the temporal bone. Preoperative position planning has to account for the available bone thickness minimizing unwanted interference with underlying anatomical structures. This study describes the first clinical experience with a planning method based on topographic bone thickness maps (TBTM) for presigmoid BB implantations. The temporal bone was segmented enabling three-dimensional surface generation. Distances between the external and internal surface were color encoded and mapped to a TBTM. Suitable implant positions were planned with reference to the TBTM. Surgery was performed according to the standard procedure (n = 7). Computation of the TBTM and consecutive implant position planning took 70 min on average for a trained technician. Surgical time for implantations under passive TBTM image guidance was 60 min, on average. The sigmoid sinus (n = 5) and dura mater (n = 1) were exposed, as predicted with the TBTM. Feasibility of the TBTM method was shown for standard presigmoid BB implantations. The projection of three-dimensional bone thickness information into a single topographic map provides the surgeon with an intuitive display of the anatomical situation prior to implantation. Nevertheless, TBTM generation time has to be significantly reduced to simplify integration in clinical routine.

Cone beam and micro-computed tomography validation of manual array insertion for minimally invasive cochlear implantation.

Delivering cochlear implants through a minimally invasive tunnel (1.8 mm in diameter) from the mastoid surface to the inner ear is referred to as direct cochlear access (DCA). Based on cone beam as well as micro-computed tomography imaging, this in vitro study evaluates the feasibility and efficacy of manual cochlear electrode array insertions via DCA. Free-fitting electrode arrays were inserted in 8 temporal bone specimens with previously drilled DCA tunnels. The insertion depth angle, procedural time, tunnel alignment as well as the inserted scala and intracochlear trauma were assessed. Seven of the 8 insertions were full insertions, with insertion depth angles higher than 520°. Three cases of atraumatic scala tympani insertion, 3 cases of probable basilar membrane rupture and 1 case of dislocation into the scala vestibuli were observed (1 specimen was damaged during extraction). Manual electrode array insertion following a DCA procedure seems to be feasible and safe and is a further step toward clinical application of image-guided otological microsurgery.

Uncovering Vulnerable Phases in Cochlear Implant Electrode Array Insertion: Insights from an In Vitro Model.

OBJECTIVES: The aim of this study is to improve our understanding of the mechanics involved in the insertion of lateral wall cochlear implant electrode arrays. DESIGN: A series of 30 insertion experiments were conducted by three experienced surgeons. The experiments were carried out in a previously validated artificial temporal bone model according to established soft surgery guidelines. The use of an in vitro setup enabled us to comprehensively evaluate relevant parameters, such as insertion force, intracochlear pressure, and exact electrode array position in a controlled and repeatable environment. RESULTS: Our findings reveal that strong intracochlear pressure transients are more frequently caused during the second half of the insertion, and that regrasping the electrode array is a significant factor in this phenomenon. For choosing an optimal insertion speed, we show that it is crucial to balance slow movement to limit intracochlear stress with short duration to limit tremor-induced pressure spikes, challenging the common assumption that a slower insertion is inherently better. Furthermore, we found that intracochlear stress is affected by the order of execution of postinsertion steps, namely sealing the round window and posterior tympanotomy with autologous tissue and routing of the excess cable into the mastoid cavity. Finally, surgeons' subjective estimates of physical parameters such as speed, smoothness, and resistance did not correlate with objectively assessed measures, highlighting that a thorough understanding of intracochlear mechanics is essential for an atraumatic implantation. CONCLUSION: The results presented in this article allow us to formulate evidence-based surgical recommendations that may ultimately help to improve surgical outcome and hearing preservation in cochlear implant patients.

The human middle ear in motion: 3D visualization and quantification using dynamic synchrotron-based X-ray imaging.

The characterization of the vibrations of the middle ear ossicles during sound transmission is a focal point in clinical research. However, the small size of the structures, their micrometer-scale movement, and the deep-seated position of the middle ear within the temporal bone make these types of measurements extremely challenging. In this work, dynamic synchrotron-based X-ray phase-contrast microtomography is used on acoustically stimulated intact human ears, allowing for the three-dimensional visualization of entire human eardrums and ossicular chains in motion. A post-gating algorithm is used to temporally resolve the fast micromotions at 128 Hz, coupled with a high-throughput pipeline to process the large tomographic datasets. Seven ex-vivo fresh-frozen human temporal bones in healthy conditions are studied, and the rigid body motions of the ossicles are quantitatively delineated. Clinically relevant regions of the ossicular chain are tracked in 3D, and the amplitudes of their displacement are computed for two acoustic stimuli.

BPACE: A Bayesian, Patient-Centered Procedure for Matrix Speech Tests in Noise.

Matrix sentence tests in noise can be challenging to the listener and time-consuming. A trade-off should be found between testing time, listener's comfort and the precision of the results. Here, a novel test procedure based on an updated maximum likelihood method was developed and implemented in a German matrix sentence test. It determines the parameters of the psychometric function (threshold, slope, and lapse-rate) without constantly challenging the listener at the intelligibility threshold. A so-called "credible interval" was used as a mid-run estimate of reliability and can be used as a termination criterion for the test. The procedure was evaluated and compared to a STAIRCASE procedure in a study with 20 cochlear implant patients and 20 normal hearing participants. The proposed procedure offers comparable accuracy and reliability to the reference method, but with a lower listening effort, as rated by the listeners (-1.8 points on a 10-point scale). Test duration can be reduced by 1.3 min on average when a credible interval of 2 dB is used as the termination criterion instead of testing 30 sentences. Particularly, normal hearing listeners and well performing, cochlear implant users can benefit from shorter test duration. Although the novel procedure was developed for a German test, it can easily be applied to tests in any other language.

Objective evaluation of intracochlear electrocochleography: repeatability, thresholds, and tonotopic patterns.

Introduction: Intracochlear electrocochleography (ECochG) is increasingly being used to measure residual inner ear function in cochlear implant (CI) recipients. ECochG signals reflect the state of the inner ear and can be measured during implantation and post-operatively. The aim of our study was to apply an objective deep learning (DL)-based algorithm to assess the reproducibility of longitudinally recorded ECochG signals, compare them with audiometric hearing thresholds, and identify signal patterns and tonotopic behavior. Methods: We used a previously published objective DL-based algorithm to evaluate post-operative intracochlear ECochG signals collected from 21 ears. The same measurement protocol was repeated three times over 3 months. Additionally, we measured the pure-tone thresholds and subjective loudness estimates for correlation with the objectively detected ECochG signals. Recordings were made on at least four electrodes at three intensity levels. We extracted the electrode positions from computed tomography (CT) scans and used this information to evaluate the tonotopic characteristics of the ECochG responses. Results: The objectively detected ECochG signals exhibited substantial repeatability over a 3-month period (bias-adjusted kappa, 0.68; accuracy 83.8%). Additionally, we observed a moderate-to-strong dependence of the ECochG thresholds on audiometric and subjective hearing levels. Using radiographically determined tonotopic measurement positions, we observed a tendency for tonotopic allocation with a large variance. Furthermore, maximum ECochG amplitudes exhibited a substantial basal shift. Regarding maximal amplitude patterns, most subjects exhibited a flat pattern with amplitudes evenly distributed over the electrode carrier. At higher stimulation frequencies, we observed a shift in the maximum amplitudes toward the basal turn of the cochlea. Conclusions: We successfully implemented an objective DL-based algorithm for evaluating post-operative intracochlear ECochG recordings. We can only evaluate and compare ECochG recordings systematically and independently from experts with an objective analysis. Our results help to identify signal patterns and create a better understanding of the inner ear function with the electrode in place. In the next step, the algorithm can be applied to intra-operative measurements.