Goals:
Direct Drive Stimulation (DDS) was developed to enable preoperative subjective evaluation of the Vibrant Soundbridge (MEDEL, Austria). The system consists of a Floating Mass Transducer (FMT) inside a silicon tube with a silicone membrane at the distal end for direct contact with the tympanic membrane optionally using castor oil for adhesive contact. The advantage of the DDS lies in providing a subjective impression of postoperative stimulation. The aim was to compare the conventional FMT to the DDS.
Materials and Methods:
Laser Doppler vibrometry measurements were performed on 10 human temporal bones. The FMT (VORP503) was coupled to the short process (SP) of the incus using the SP coupler. The DDS was placed in contact to the tympanic membrane either with or without castor oil. Another parameter was the holding position of the DDS along the silicon tube. The stimulation level was set to 68 mV for the FMT while 68 mV and 1500 mV for the DDS. The transfer function (mm/s/V) was recorded in the frequency range from 100 to 10,000 Hz. The indication range of the DDS was determined by adjusting the indication range for FMT forward stimulation using the difference between FMT SP and DDS stimulation.
Results and Discussion:
The transfer function of the DDS could be measured with a signal above the 6 dB noise level for frequencies between 500 Hz and 4680 Hz when the DDS was operated at a stimulation level of 1500 mV. The transfer function of the DDS is 20–30 dB lower than the transfer function of the SP coupler for most frequencies. The application of castor oil resulted in no significant change in the transfer function. Similar magnitudes of the DDS transfer function were observed when the DDS was driven with 1500 mV, while the FMT was driven with 68 mV, which corresponds to approximately 100 dB SPL at 1000 Hz. Based on the frequency specific differences between the FMT SP and DDS temporal bone measurements, the maximal hearing loss for the use of the DDS is approximately 40 dB at 500 Hz and rises to 60 dB at 6000 Hz.

Conclusion:
DDS offers a complementary subjective tool for preoperative testing of the implant, but with a reduced indication range compared to the implanted FMT. It provides therefore, like headband testing with bone conductive devices in an outbound clinic setup, a conservative prognosis of the postoperative hearing.

Goals: The maximum output (MO) and the dynamic range (DR) of an active middle ear implant are key parameters that determine the achieved aided word recognition score (WRS) in quiet. Previously, the MO and DR were successfully determined for reverse stimulation in patients implanted with the Vibrant Soundbridge (VSB) with the floating mass transducer positioned in the round window niche (Maier et al. 2024/ Busch et al. 2024). The aim of this study was to investigate if the method can be used in all VSB implantations, independently of the stimulation direction (forward/reverse), coupling type, processor and implant.
Methods: Data of patients implanted with the VSB (MED-EL, Austria) with different forward and reverse stimulation modes were analyzed in a retrospective study. In total 202 ears with forward (incus n=138, oval window n=40, stapes head n=24) and 66 ears with reverse stimulation (without coupler n=28, spherical coupler n=19, soft coupler n=10, *Hannover coupler” n=11) were included and analyzed. Following the method of Busch et al. 2024 and Maier et al. 2024, the frequency-dependent MO and covered DR for each patient was determined from clinical routine data. Subsequently, a Chapman logistic function was fitted to the individual DR vs WRS, separately for forward and reverse stimulation and statistically compared.
Results: The MO frequency dependency was similar for most coupling types with a maximum found at 1.5 kHz. Both relationships between WRS and DR were well described by the logistic growth function (forward, reverse R²=0.59/0.64) with no obvious differences. The quantitative comparison between WRS in 10 dB DR bin groups from 0 – 60 dB DR, revealed no statistically significant differences (p < 0.05) between stimulation directions. Hence, the method can be equally applied for forward and reverse stimulation, all VSB processor/implant combinations and a broad range of coupling options.
Conclusion: The individual MO and DR can be determined from patients’ clinical data and this approach can be equally applied to forward and backward stimulation. This supports the hypothesis that the proposed method to determine the DR can be generally used to predict patient outcomes and definition of evidence-based indication criteria.

Goals
Adults and children that do not benefit from hearing aids can be treated with the Vibrant Soundbridge (VSB; MED-EL), an active middle ear implant indicated for sensorineural, conductive, and mixed hearing loss. Auditory brainstem responses (ABR) have been established as a reliable method to assess the coupling efficiency intraoperatively. Additional frequency-specific information could be obtained from measurements of auditory steady state responses (ASSR). This study focuses on the correlations and differences between intraoperative and audiological thresholds.

Material and Methods
ABR and ASSR measurements were performed intraoperatively using a standard AEP system (Eclipse, Interacoustics) and a wired adapter (AcoustiAP, MED-EL). ASSR responses were recorded using scalp electrodes. The system allows largely automated determination of frequency-specific thresholds at 500, 1000, 2000, and 4000 Hz. Intraoperative ASSR thresholds were compared with preoperative bone conduction and postoperative vibrogram thresholds.

Results
Intraoperative ASSR measurements were conducted in more than 80 patients, and frequency-specific thresholds could be reliably obtained in all cases. A significant correlation was observed between intraoperative ASSR and preoperative bone conduction thresholds at 1000, 2000, and 4000 Hz, whereas the correlation at 500 Hz was weaker. In addition, intraoperative ASSR thresholds showed significant correlations with postoperative vibrogram thresholds across all tested frequencies.
When comparing threshold levels, intraoperative ASSR thresholds were generally higher than preoperative bone conduction thresholds, with larger differences at low frequencies and smaller differences at higher frequencies. On average, the overall pure-tone average difference was in the range of approximately 25 dB. In contrast, the difference between intraoperative ASSR thresholds and postoperative vibrogram thresholds was considerably smaller, typically within 10 dB on average.

Conclusion
The findings demonstrate that frequency-specific ASSR measurements can be reliably obtained intraoperatively. The consistent relationship with both preoperative bone conduction and postoperative vibrogram thresholds suggests that these measurements provide meaningful information about coupling efficiency. Intraoperative ASSR measurements may therefore support the assessment of coupling quality during surgery and contribute to optimizing postoperative hearing outcomes.

Introduction
The Vibrant Soundbridge (VSB, MED-EL) is one of the most widely used active middle ear implants. Optimal coupling between the Floating Mass Transducer (FMT) and the inner ear is essential for achieving favorable postoperative hearing outcomes. However, reliable objective methods for intraoperative assessment of FMT coupling remain limited.
The recently introduced AcoustiAP system (MED-EL) enables direct stimulation of the implant during surgery and allows recording of auditory brainstem responses (ABRs) through the implanted system. This technology may provide a novel approach for objective intraoperative evaluation of implant coupling.
The aim of this study was to investigate the feasibility and clinical relevance of intraoperative ABR monitoring using the AcoustiAP system during VSB implantation.
Methods
Fifteen patients undergoing VSB implantation were enrolled in this study, including three pediatric and two adult cases.
Following placement of the FMT, the AcoustiAP device was positioned on the receiver coil of the implant to deliver stimulation. The initial stimulus level was set at 30 dB above the bone-conduction threshold to confirm the presence of a response, defined by clear identification of wave V. Stimulus intensity was then decreased in 10-dB steps until wave V disappeared to determine the ABR threshold.
The intraoperative ABR thresholds obtained using AcoustiAP were compared with three audiological parameters:
• mean bone-conduction thresholds
• mean vibrogram values
• postoperative VSB-aided hearing thresholds
Correlation analyses were performed to evaluate the relationships between these parameters.
Results
The mean intraoperative ABR threshold measured using AcoustiAP was 44 dB, while the mean preoperative bone-conduction threshold was 20 dB.
ABR thresholds obtained with AcoustiAP demonstrated correlations with all examined audiological parameters. Among these, the strongest correlation was observed between AcoustiAP-derived ABR thresholds and vibrogram values.
Conclusion
Intraoperative ABR monitoring using the AcoustiAP system was feasible and provided objective information regarding FMT coupling to the inner ear during VSB surgery. The strong correlation between AcoustiAP-derived ABR thresholds and vibrogram values suggests that this technique may serve as a valuable intraoperative tool for evaluating implant coupling and predicting postoperative auditory performance.

Background: Fitting of active middle ear implants can be difficult when patients are unable to cooperate, such as in young children, so an objective method for assessing hearing performance would be desirable. Analysis of Cortical Auditory-Evoked Potentials (CAEP) can be a helpful method for estimating the efficiency of such devices.

Methods: CAEP measurements were carried out with the active middle ear implant Vibrant Soundbridge (VSB, MED-EL, Austria). Speech-like narrowband stimuli (three frequency ranges) provided by a standard ABR system (Interacoustics, Denmark) were used. Stimuli were presented in free sound field at stimulation level 65 dBSpRefL in aided and unaided condition.

Results: Fifteen subjects implanted with a VSB participated in the study. In a total of 45 measurements 40% and 93.3% of the CAEP could be identified under unaided and aided conditions, respectively. Typical CAEP peak amplitudes (P1, N1, P2) were significantly higher at the aided condition than in the unaided condition. The latencies did not differ significantly.

Conclusion: The measurement method presented shows that CAEP can be reliably recorded via VSB to determine hearing performance. This allows an objective verification of the fitting when subjective procedures cannot be reliably performed for any reason.

Objectives: Cochlear hypoplasia (CH) demonstrates highly variable outcomes after cochlear implantation (CI), and morphologic subtype alone may not adequately predict neural function. This study investigated intracochlear neural responsiveness in children with CH, examined the role of MRI-defined cochlear nerve status, and evaluated associations between electrophysiologic measures and auditory performance.
Design: Twenty-nine children with CH (35 ears) and 16 children with normal cochlear anatomy (20 ears) underwent CI and postoperative electrically evoked compound action potential (eCAP) testing. Electrode-level measures included response presence, threshold, maximum amplitude, amplitude growth function (AGF) slope, recovery parameters (t₀ and τ), and model fit (R²). Cochlear nerve status was classified on MRI as normal or deficient (aplasia/hypoplasia). Linear mixed-effects models accounted for repeated electrode measures. Associations between averaged eCAP metrics and 1-year Categories of Auditory Performance (CAP) scores were analyzed controlling for implantation age.
Results: Compared with controls, CH ears showed elevated thresholds, reduced amplitudes and AGF slopes, prolonged t₀, and lower fitting R² (all p < 0.05). Compared to CH-Ⅲ, CH-Ⅳ demonstrated poorer neural responsiveness; however, these differences were no longer significant after adjusting for nerve status. Cochlear nerve deficiency was strongly associated with reduced response rates, higher thresholds, smaller amplitudes, flatter slopes, and prolonged t₀ (all p < 0.01). Measurable eCAPs were observed in several ears with MRI-reported nerve aplasia, though significantly attenuated. τ did not differ between groups; however, reduced R² and physiologically implausible estimates in CH suggested disrupted recovery dynamics. Averaged eCAP metrics significantly correlated with 1-year CAP scores independent of implantation age.
Conclusions: Cochlear nerve integrity, rather than CH subtype alone, primarily determines intracochlear neural responsiveness and auditory outcome following CI.

Objective: This study aimed to investigate cochlear nerve responsiveness to electrical stimulation in cochlear implant (CI) recipients with auditory neuropathy spectrum disorder (ANSD), focusing on genotype-specific differences in neural function. We examined whether ANSD subtypes, classified by genetic mutations (synaptic vs. neural), exhibit distinct cochlear nerve response profiles as measured by electrically evoked compound action potentials (eCAPs).
Participants and Methods: This retrospective study included 19 patients diagnosed with ANSD prior to CI, all of whom underwent genetic testing. Participants were classified into three groups based on genetic findings: the Synaptic group (mutations affecting synaptic transmission), the Neural group (mutations affecting cochlear nerve conduction or integrity), and the Unsolved group (patients with unknown genetic causes). eCAP amplitude growth functions (AGFs) were recorded at basal, mid-array, and apical cochlear electrodes under IPG 7 µs and IPG 42 µs. Refractory recovery functions (RRFs) were measured at the same sites under IPG 7 µs. Dependent variables (DVs) included AGF slope, maximum amplitude, threshold, N1 latency, refraction recovery time (t₀ and τ), and IPG effects on slope and amplitude. Linear mixed-effects models were used to compare DVs across genotype groups and cochlear regions.
Results: The Synaptic group included 9 patients, with 8 carrying OTOF mutations (9 ears) and 1 carrying SLC17A8 mutation (1 ear). The Neural group comprised 5 patients, 3 with ATP1A3 mutations (3 ears) and 2 with TWNK mutations (4 ears). The Unsolved group had 5 patients (6 ears). The Synaptic group demonstrated significantly lower thresholds, higher eCAP amplitudes, shorter N1 latencies, and steeper AGF slopes compared to the Neural group. The Neural group exhibited significantly prolonged refractory recovery time (t0). The IPG effect on both slope and amplitude was more pronounced in the Synaptic group than in the Neural group.
Conclusion: Synaptic mutations are associated with preserved cochlear nerve function, whereas Neural/Mito mutations result in impaired neural responsiveness and slower recovery. These findings underscore the potential for genotype-informed CI programming to optimize outcomes for ANSD patients and support personalized treatment strategies.

INRODUCTION:
Anomaly of the cochlea and cochlear nerve is always grey zone in decision making for cochlear implants versus auditory brainstem implants. Radiological imaging only prove the anatomical status of the nerve, however the functional status of the nerve is more important in decision making for candidacy. Trans tympani Electrically evoked Auditory Brainstem response is one of the objective measures for the nerve function in subjects with profound hearing loss. This study will highlight the role of TTEABR and its characteristics in subjects with anomaly of the inner ear and nerve.
NEED OF THE STUDY:
The current study is to profile the TT-EABR findings in cochlear and nerve anomalies and also to correlate the outcomes of subjects who underwent CI or ABI after TT-EABR.
OBJECTIVE OF THE STUDY:
- To profile the characteristics of TT-EABR.
- To correlate the TT-EABR findings with post-op audiological findings.
METHODS:
TTEABR was performed in 100 subjects with cochlea and nerve anomaly in OR under general anaesthesia. A golf club electrode was used to deliver electrical stimulus either on the round window niche or on the promontory depending on the anatomy. Electrical stimulus were delivered using Maestro software the responses were recorded via scalp electrodes using EP device. TTEABR responses were classified based on the morphology based on occurrence of peaks with respect to latency. Subjects who had good responses were recommended for CI and subjects with no responses were recommended for ABI. Post-op EABR and ECAP responses were measured on these subjects for correlation.
Results and Conclusion:
Responses were variable in morphology across subjects. Maximum of six peaks were recoded with varying latency. Peaks include both auditory response and also non-auditory responses which were usually late in latency. Subjects with good responses were recommended for CI and subjects with no responses were recommended for ABI. The scores of subjects with CI and ABI were correlated with pre-op responses. Subjects with good TTEABR responses correlated well with post-operative measures in subjects with CI. The post-implant EABR shows better morphology compared to pre-op TTEABR. This suggest TTEABR is a compliments in decision making for candidacy in subjects with anomalous cochlea and nerve.

Goal: The aim of this study was to evaluate the applicability of intracochlear electrocochleography (ECochG) and electrically evoked brainstem response (eABR) registration after cochlear implantation (CI) for revealing electrophysiological features of different forms of auditory neuropathy spectrum disorders (ANSD) and predicting rehabilitation outcomes.

Material and methods: 22 children with ANSD of different etiology were enrolled in the study. Intracochlear ECochG and eABR registration after CI were performed in 23 ears. Registration of eABR was performed using specific for certain CI system programming software and hardware and clinical system for the registration of evoked potentials.

Results: Cochlear microphonic was recordable in 21 cases. The summating and compound action potentials were recordable in 7 cochlear implant users. There was diversity in ECochG results within the group of children with the same etiology of ANSD. On the other hand, there were cases when ECochG results were almost identical even in patients with different etiology and pathophysiology of ANSD.
The eABRs were registered in 7 children with OTOF-related ANSD and in 9 children with perinatal risk factors. Presence of eABRs in OTOF-related cases matches the pathophysiology of auditory synaptopathy. In 3 ears with hypoplastic cochlear nerve, eABRs were absent or partially recordable only in bipolar mode of stimulation of basal turn. In children with unknown etiology, in 2 cases eABRs were recordable from all stimulated electrodes (auditory synaptopathy) and in other 2 cases were absent (auditory neuropathy). Rehabilitation outcomes after CI corresponded to the results of eABR registration and were better among children with eABRs.

Conclusions: Intracochlear ECochG does not provide a reliable differentiation of different types of ANSD. Registration of eABRs in monopolar stimulation mode is valuable for differentiating ANSD types and predicting outcomes of cochlear implantation in children with ANSD.

Goals
To evaluate the role of transtympanic electrically evoked auditory brainstem response (TT-eABR) within a structured protocol for guiding implant selection, validating neural responsiveness, and optimizing early outcomes in complex pediatric auditory implant candidates.
Material and Methods
Nineteen ears of pediatric cases (mean age 2.1 years) with severe-to-profound hearing loss and complex cochlear and/or neural anomalies were included. Indications comprised cochlear nerve hypoplasia, cochlear aperture stenosis, Incomplete Partition Type II malformations, auditory neuropathy spectrum disorder, and cases with inconclusive imaging, including those not meeting definitive criteria as per Sennaroglu classification. A predefined stepwise electrophysiological protocol was implemented. Transtympanic eABR was recorded using promontory stimulation with a MED-EL PromStim electrode and the Interacoustics EP25 system. Waveform presence and reproducibility were analyzed. Cases with preserved responses were selected for cochlear implantation. Following implantation, intraoperative impedance field telemetry and Auto ART were recorded. Prior to switch-on, intracochlear eABR was obtained using CI electrodes as stimulators. Initial MAP settings were guided by the eABR findings. Early outcomes were assessed using aided sound field thresholds and behavioral responses.
Results
TT-eABR recordings were successfully obtained in all 21 ears. Among these, 9 ears had cochlear nerve hypoplasia, of which 7 demonstrated preserved TT-eABR responses; 5 of these underwent cochlear implantation. In these 7 cases, intraoperative TT-eABR and post-implant intracochlear eABR demonstrated strong concordance in waveform morphology and latency. Three ears with auditory neuropathy spectrum disorder were evaluated; 2 with preserved TT-eABR responses underwent cochlear implantation with similar eABR concordance, while 1 is planned for CI. Absent TT-eABR responses were consistently associated with poor neural integrity and exclusion from cochlear implantation. Two patients underwent auditory brainstem implantation, with others in line for ABI. All cochlear implant recipients achieved aided thresholds within the speech range (≤ 35 dB HL), indicating effective early auditory access, and demonstrated consistent behavioral responses to soft sounds at early activation.
Conclusion
TT-eABR is a reliable preoperative tool that demonstrates strong concordance with intraoperative electrophysiology.

Background and Goals
Optimizing cochlear implant (CI) fitting in children requires precise and individualized adjustment. In very young patients, reliable behavioral feedback on auditory perception and speech understanding is often limited or unavailable. Consequently, clinicians lack objective markers indicating whether auditory input is processed at the cortical level.
This study evaluates the clinical implementation of the CORGEE system – an electroencephalography (EEG)-based approach originally developed for hearing aid users – within routine pediatric CI care. In addition, it investigates whether EEG can provide clinically applicable, real-time objective measures of auditory perception and early speech-related neural processing in pediatric CI users, focusing on neural markers that reflect prerequisites for speech understanding.

Materials and Methods
Pediatric CI users undergo EEG recordings during auditory stimulation with natural, continuous speech using a child-adapted EEG protocol integrated into routine CI appointments.
Neural speech envelope tracking during continuous speech stimulation serves as the primary electrophysiological marker. This method quantifies synchronization between cortical activity and the temporal envelope of speech and is considered an early neural correlate of speech processing. Feasibility is assessed based on integration into the clinical workflow and reliability of neural tracking metrics under routine conditions.

Results
Data collection is ongoing. Initial analyses include 10 pediatric CI users. EEG recordings were successfully integrated into routine CI appointments, and cortical responses to continuous speech were measurable in all patients. Interindividual variability in neural tracking strength was observed, potentially reflecting differences in auditory performance or developmental stage.

Conclusions
EEG-based neural speech tracking shows strong potential as an objective tool for assessing cortical speech processing in pediatric CI users. This approach may support optimization of CI stimulation parameters when behavioral feedback is limited and enable objective monitoring of auditory development during early rehabilitation.

Goals
Assessment of speech intelligibility in young or hard to test children with hearing aids (HA) or cochlear implants (CI) is challenging when behavioral testing is unreliable or infeasible. Neural Speech Tracking (NST), derived from EEG responses to natural speech, offers an objective measure of cortical speech processing. NST is quantified as the alignment between cortical responses and the temporal speech envelope. This clinical study evaluated the validity and clinical feasibility of real time NST, as implemented in the CORGEE system (Brainphonics, Leuven), in pediatric users of hearing devices.

Material and Methods
A multicenter cross sectional study was conducted in children with hearing impairment, including HA users (N = 88) and a subgroup of CI users (N = 11). Participants watched an animated movie while continuous speech was presented at different levels via a loudspeaker in free-field. EEG was recorded, and NST was computed in real time. Behavioral speech audiometry in quiet was conducted when feasible and compared with NST outcomes to assess clinical validity.

Results
NST could be obtained reliably across the full pediatric age range (7 months to 12 years) in both HA and CI users. NST increased with higher speech levels, demonstrating sensitivity to speech audibility. In HA users, NST captured aided benefit, with the strongest differences between aided and unaided conditions at lower presentation levels. Across participants, stronger NST responses were associated with higher behavioral speech intelligibility scores.

Conclusion
Real time NST provides an objective clinically applicable biomarker of cortical speech processing in children with hearing impairment. It reflects auditory access to speech and corresponds with behavioral outcomes, supporting its use as a complementary tool for evaluation, counseling, and device optimization, particularly in young or behaviorally hard-to-test patients.

Background: The Acoustic Change Complex (ACC), an auditory evoked potential triggered by a change in an ongoing stimulus, has shown promising results as an objective measure for frequency discrimination and speech perception. Although a wide variety of frequency change stimuli have been employed in previous studies, limited research has specifically investigated the ACC for both low- and high-frequency tones in cochlear implant (CI) users with full electrode coverage. Addressing this gap, the present study investigates the ACC in response to frequency changes along the CI electrode array. We aim to enhance our understanding of frequency-specific auditory processing in CI users and evaluate the clinical utility of the ACC as a marker for speech perception in this population.
Methods: This cross-sectional study utilizes a four-electrode EEG setup, with active electrodes positioned at Cz and Fz. Auditory stimuli consist of a 3000 ms pure tone base frequency, followed by an upward or downward frequency-modulated sweep. Participants complete speech perception tests in both quiet and noise, as well as spectral ripple discrimination tasks. Patient recruitment is ongoing, with 16 participants tested to date.
Results/conclusion: Data indicate that a distinct N1P2 waveform can be reliably elicited across all frequency change stimuli along the electrode array. In addition, N1P2 amplitudes are significantly smaller when the frequency transitions occur toward the ends of the array. Specifically, transitions from 188 Hz to 125 Hz produce smaller amplitudes compared to transitions from 125 Hz to 188 Hz, and similarly, transitions from 4000 Hz to 6000 Hz yield smaller responses than those from 6000 Hz to 4000 Hz. We observed moderate to strong positive correlations between the N1P2 amplitude elicited by a frequency shift from 2000Hz to 3000Hz and both spectral ripple performance and speech perception in quiet. Additionally, the N1P2 amplitude in response to a frequency change from 500Hz to 750Hz demonstrated moderate correlations with spectral ripple performance and speech perception in noisy conditions.
The effects of frequency change stimuli along the electrode array, as well as the impact of upward and downward frequency changes, will be discussed. In addition, the relation between the different frequency change stimuli and speech perception, including speech in quiet, speech in noise, and spectral ripple discrimination, will be discussed.

Goals
For assessment of the health of the auditory nerve in cochlear implant (CI) users electrically evoked compound action potentials (eCAPs) are often applied. Relative measures derived by comparing eCAPs to different inter-phase gaps (IPGs) seem appropriate since they are strongly correlated with neural survival (Ramekers et al., 2015). The presence of residual hair cells, which we assume is beneficial for neural health, can be assessed with electrocochleography (Giardina et al., 2019). In an ongoing trial, we record eCAPs and ECochG in CI users to examine the predictive value for hearing performance. In addition, we consider the relation between eCAPs and ECochG.

Material and Methods
Twenty-three subjects with severe sensorineural hearing loss, aged 34 to 82 years, received a CI (Flex28, MED-EL). Four months postoperatively, eCAPs were recorded at each electrode to biphasic current pulses with varying IPGs (2.1 to 30 µs). Outcome measures include amplitude and latency at maximum current levels, and the current level halfway the amplitude growth function, level50%. Relative measures were obtained by the difference between measures at IPG of 30 and 2.1 µs. ECochG was postoperatively performed to tones at 115 dB SPL at frequencies from 250 to 4000 Hz. Hearing performance was assessed by CVC in noise perception and the spectral-temporally modulated ripple test (SMRT; Aronoff and Landsberger, 2013).

Results
Within-subject analyses showed moderate to strong correlations between IPG measures and cochlear microphonic (CM) amplitudes in half of the participants. In a between-subjects analysis, neither absolute eCAP measures nor IPG measures correlated with CM amplitudes. The SMRT scores showed moderate correlations with eCAP latency and the IPG effect of latency. SMRT scores did not correlate with CM amplitude. Speech perception outcomes did not correlate with eCAP measures or CM amplitude.

Conclusion
The lack of correlations between eCAPs reflecting neural health and CM reflecting residual hair cells may be explained as follows. The CM mainly reflects surviving outer hair cells, while inner hair cells and/or supporting cells are more important for neurotrophic support of the SGCs. We conclude that CM and eCAP provide largely independent measures reflecting the health of different cochlear structures. eCAP measures seem more predictive than CM for hearing performance with CI.

Measures of auditory nerve function using cochlear-implant driven electrical stimulation can be used to characterise neural health following implantation, supporting outcome assessment, prognostication, and longitudinal monitoring with existing devices. In addition, these measures show promise as candidate endpoints for clinical trials of therapies targeting neural hearing loss. Yet the extent to which these measures remain stable over clinically relevant timescales following implantation is not well established.
Here, we integrated data from earlier studies with data from an ongoing longitudinal study to evaluate the stability and temporal evolution of standard clinical and advanced comparative neural health measures over periods extending to 40 weeks post-implantation. Specifically, assessments included daily measurements of electrically evoked compound action potentials (ECAPs) from six participants, allowing investigation of trajectory stability following implantation. Advanced tests included panoramic ECAPs (PECAPs), interphase gap (IPG) effects, and polarity effects, assessed twice in three participants at early and later post-implantation timepoints.
Findings indicate that ECAP thresholds and amplitudes measured at the maximum stimulation level exhibit early post-implantation variability, particularly during the first month and before cochlear implant is switched on, with mean within-participant trajectories generally stabilising over time. At the electrode level, cases of small but stable increases or decreases in excitability were observed, although no consistent pattern emerged across electrodes or participants. Completion of the ongoing study will enable further evaluation of the long‑term stability of all neural health measures. For the three advanced tests, systematic longitudinal change will be assessed relative to repeated-measurement variability that was estimated in an independent cohort.
Overall, our studies suggest that these neural health measures demonstrate sufficient post-implantation stability to support their suitability for longitudinal assessment and as candidate outcomes for evaluating therapeutic interventions for neural hearing loss. Inclusion of a variety of measures results in a more comprehensive test battery, with the potential to capture change across distinct and complementary aspects of neural health.

Goals: To investigate if and how the intra- and postoperative measures of cochlear implant electrode impedance are related to speech recognition and the duration of processor use per day.
Material and Methods: Our study comprised a consecutive set of patients with a lateral-wall electrode array. The postoperative total electrode impedances that corresponded in time to the speech recognition in quiet (106 ears) and in noise (101 ears) assessments were retrieved. The mean impedance and metrics denoting the variation in impedances were calculated across the electrode array and its regions, and patients were grouped based on their preferred stimulus presentation level during the speech recognition in quiet assessment. Relationships between the total electrode impedance metrics and speech recognition were then analyzed. Additionally, we evaluated how these metrics were related to the duration of processor use per day for a subset of 51 ears. In an earlier study, the spread of intracochlear electric field was measured intraoperatively for 82 ears through the transimpedance matrix.[1] These measurements underwent optimization to estimate effective transimpedances, from which their 50% widths were computed, and the exponential spread coefficients (ESCs[2]) were derived. We studied how these measures were related to the postoperative speech recognition in quiet (41 ears) and in noise (35 ears).
Results: Regarding the postoperative total electrode impedance metrics, the mean and the variation in impedances were statistically significant predictors of speech recognition in quiet and accounted for more variance when the stimulus presentation level was equal to or exceeded 65 dB SPL. Though statistically non-significant, increased duration of processor use per day tended to be associated with reduced variation in impedances in the middle region of the electrode array. Statistically significant weak to moderate correlations between the ESCs and speech recognition in quiet were revealed. The direction of these relationships varied with the region of the electrode array stimulated.
Conclusion: The total electrode impedance metrics and the ESCs are related to speech recognition in quiet. Although both the impedance magnitude and its variation are determinants of speech recognition, the strengths of these relationships increase at higher stimulus presentation levels, possibly implying the role of voltage compliance.

Background
This study investigated whether intracochlear voltage distribution derived from impedance field telemetry (IFT) in cochlear implant (CI) users with straight lateral wall electrodes were associated with electrically evoked cervical and ocular vestibular myogenic responses (e-cVEMPs and e-oVEMPs).
Methods
In adult MED-EL Synchrony CI users, e-cVEMPs and e-oVEMPs were recorded during stimulation of intracochlear electrodes E3, E6, E10, and E11. IFT was used to obtain voltage matrices representing intracochlear electric field distribution. Voltage data were adjusted for stimulation-level differences, and qualitative and quantitative analyses compared participants with and without e-VEMP responses and examined spatial associations between voltage profiles and vestibular activation.
Results
The study included 18 implanted ears from 17 participants. Qualitative inspection of difference matrices across all stimulation electrodes revealed local variations within individual stimulation sites, but no consistent group-related pattern that remained across electrodes for either e-cVEMPs or e-oVEMPs. Quantitative analysis of voltage line graphs demonstrated higher voltages and e-oVEMP thresholds at all sites in participants with e-oVEMPs, reaching significance only at E3. For e-cVEMPs, no significant group differences were observed. Detection rates indicated a spatial tendency, with e-cVEMPs mainly during basal stimulation and e-oVEMPs during apical stimulation.
Conclusion
The results suggest the presence of different current pathways for saccular and utricular co-stimulation. Intracochlear electric field distributions did not show a direct relationship with e-VEMP occurrence. Spatial dependencies and voltage decay characteristics indicate distinct mechanisms, possibly related to variations in local field orientation and tissue conductivity that should be further investigated using anatomical data.

Introduction: To preserve residual hearing during cochlear implant (CI) insertion, intraoperative cochlear monitoring is desirable. A promising approach is the measurement of cochlear micropotentials (CMs) using electrochleography (ECochG). Currently, this is primarily performed intracochlearly via the CI electrode. However, here the recording location changes during insertion, meaning that changes in signal amplitude do not necessarily correspond to impairments of residual hearing. For example, a previous study suggests that the course of preoperative residual hearing also influences the behavior of the measured signal amplitude (Haumann et al., 2025). This study used a 500 Hz tone burst, whereas multifrequency stimuli are now available. The aim of this study is the application of such a multifrequency stimulus (MFS) and the comparison of the results to the 500 Hz tone burst.

Method: During insertion of hearing preservation CI electrodes, ECochG was recorded intracochlearly via the CI electrode on contact 1. Depending on the preoperative audiogram, stimulation was done using the 500 Hz tone burst or the MFS. After insertion ECochG was recorded sequentially on all 12 contacts, applying both stimuli separately. Sequential recording on all contacts using both stimuli was repeated at the first fitting appointment (five weeks after surgery) and after 3 months of CI use. The MFS contains five frequencies (250, 500, 1000, 2000, and 4000 Hz). Up to now, n=7 patients are included in the study, receiving MED-EL Flex electrodes of different lengths and insertion depths, with n=4 having completed the first fitting appointment.

Results: Potentials can also be elicited with the MFS, which appear to correlate with the audiogram. However, measured amplitudes are lower than with single-stimulus stimulation. Effects such as phase shifts and additional peaks appear to be partially detectable with the MFS, although this seems to be hampered by superposition. Clearer effects seem to be evident with a pure tone burst. Especially in cases of pantonal hearing loss, effects appear to occur across different frequencies and in different areas of the cochlea.

Conclusion: The stimulus should be selected according to the application. If a more comprehensive picture of the cochlea is the primary focus, the MFS should be chosen. However, if effects of residual hearing are to be further investigated, 500 Hz tone bursts should probably be used.

Goal
Cochlear microphonics (CM) are bioelectrical potentials generated by hair cells in response to acoustic stimulation and can be recorded through cochlear implant electrodes. They provide an objective indicator of cochlear function and residual hearing. The aim of this study was to evaluate CM growth functions and to assess the relationship between CM-derived thresholds and behavioral audiometric thresholds.
Material and Methods
Eighteen cochlear implant recipients with Advanced Bionics devices and residual hearing were screened, and thirteen subjects were included in the analysis. CM responses were recorded using the Active Insertion Monitoring (AIM) system. Acoustic stimulation consisted of 50-ms tone bursts presented through insert earphones at levels between 100 and 115 dB HL in 5-dB steps. Responses were recorded between intracochlear electrodes and the implant case. CM signals were calculated by subtracting responses to condensation and rarefaction stimuli and analyzed using FFT at the stimulus frequency. Threshold estimates were obtained using AIM extrapolation and least-squares fits of CM growth functions.
Results
CM-derived thresholds showed similar ranges to audiometric thresholds, although differences greater than 20 dB were observed in some cases. The AIM extrapolation method on electrode contact 1 demonstrated the strongest correlation with audiometric thresholds. CM growth function slopes ranged from 0.6 to 1.2 (mean 0.84). Spatial analysis across the electrode array revealed frequency-dependent response patterns, with lower frequencies producing maximal responses on more apical electrodes and higher frequencies on basal contacts.
Conclusions
CM measurements obtained through cochlear implant electrodes provide useful information about cochlear function and may allow estimation of audiometric thresholds in cochlear implant recipients. However, variability between subjects indicates that additional factors influence the relationship between CM responses and behavioral hearing thresholds. Further studies are required to improve CM-based threshold estimation methods.

In cochlear implantation, several potential sites of damage have been identified that may result in residual hearing loss, including the approach to the cochlear lumen and insertion of the electrode. Promontory ECochG may be used to monitor cochlear functions throughout phases of surgery, including the opening of the cochlea and insertion of the sheath of the Slim Modiolar Electrode (SME) insertion tool. The goal current study is to use intra-operative promontory ECochG threshold measurements and pre- and postoperative audiometry to determine the stage of surgery at which the cochlear function is potentially compromised in patients implanted with the SME electrode.

In a prospective multicenter clinical trial, 48 adult patients with significant residual hearing at the lower frequencies (< 80 dB HL at 500 Hz) indicated for cochlear implantation are included. All participants will be implanted with a Nucleus 1032 with the SME. Intra-operative promontory ECochG is performed (acoustic broadband clicks) to assess thresholds at baseline, after the extended round window or cochleostomy approach, insertion of the sheath of the insertion tool, insertion of the electrode and positioning of the lead in the mastoid. Pure tone audiometry was performed after approximately 1 week and 3 months postoperatively.

Preliminary results will be presented of 20 patients. In 18 of the patients reliable promontory ECochG thresholds could be obtained. During the surgical steps as described above a significant intraoperative decline (> 5 dB loss) was rarely observed. The postoperative tone audiometry showed a (near) complete loss in approximately one third, partial loss in one third and (near) complete preservation (< 10 dB loss PTA low) of residual hearing in the remainder third of the patients.

Partial or complete loss of residual hearing using the SME is not uncommon and more often occurs in the period after implantation then during the implantation procedure itself.

Goals
To compare intraoperative multi-tone cochlear microphonic (CM) monitoring using Advanced Bionics AIM with postoperative CImago-based electrode position analysis in two cochlear implant recipients implanted with different electrode designs, and to explore the relationship between CM peak frequency, insertion depth, scalar location, and early hearing preservation.

Material and Methods
Two patients with residual hearing underwent left cochlear implantation with intraoperative multi-tone AIM monitoring. Case 1 (36-year-old female) received a HiFocus SlimJ. Case 2 (17-year-old male) received a HiFocus MidScala. The primary AIM time-series parameter was CM FFT amplitude during insertion. The AIM reports demonstrated the frequency-specific ECochG thresholds and response patterns. Postoperative electrode position, angular insertion depth, and scalar location were assessed using CImago research software. Hearing preservation (HP) at 1 month was calculated according to the HEARING group formula.

Results
In Case 1 (SlimJ), the largest CM FFT amplitude during insertion was observed at 500 Hz. In Case 2 (MidScala), the largest CM FFT amplitude was observed at 250 Hz. Postoperative CImago analysis demonstrated a greater angular insertion depth in Case 2 (apical contact C1: 450°) compared with Case 1 (apical contact C1: 417°). In both cases, most contacts were located in scala tympani; however, several contacts were classified as scalar location 1 (interaction with basilar membrane or osseous spiral lamina), without frank translocation. At 1 month postoperatively, Case 1 was categorized as Partial HP, whereas Case 2 achieved Complete HP according to HEARING group criteria.

Conclusion
In these two cases, the frequency showing the maximal intraoperative CM FFT amplitude corresponded to the apical extent of insertion estimated by CImago, with the deeper-inserted MidScala electrode demonstrating a lower-frequency CM peak. Despite limited scalar interactions, both patients achieved meaningful short-term hearing preservation, including Complete HP in the deeper insertion case. These findings support the complementary use of intraoperative multi-tone CM monitoring and quantitative postoperative imaging to understand frequency-place matching and structural correlates of hearing preservation in cochlear implantation.

Background: During cochlear implant (CI) surgery, it is our aim to minimize insertion trauma and preserve intracochlear structures and hearing as much as possible. New developments like CI insertion robots can be valuable to further optimize our surgical technique. To better understand the potential benefit on intracochlear structure preservation during implantation by robotic insertion, we conducted a case-control study comparing electrocochleography (ECochG) and electrode impedances during manual and Otodrive assisted surgery.

Methods: ECochG responses were recorded in more than 35 CI recipients undergoing either manual or Otodrive robot-assisted CI surgery led by two experienced surgeons in the same center. The acoustic stimulation to elicit this response was presented via Etymotic ER-3C insert earphones. The earphones were connected to an external acoustic stimulator which was programmed and triggered by Maestro 9.0.4 based Research software (MED-EL GmbH, Innsbruck, Austria). The recordings were performed during electrode insertion. Alternating-polarity ECochG measurements were made continuously as a response to a 12 ms long Chirp at 40 dB above the subject’s pre-operative hearing threshold at 500 Hz.

Results: An event-related categorization was performed to distinguish specific patterns within the continuous ECochG and impedance signal. The multifrequency Chirp stimulus allows us to follow the tonotopic arrangement throughout the electrode insertion, as seen by rise and subsequent falls in the single frequency components of the stimulus once the electrode contact passed the generator site. Drops in multiple ECochG frequency responses combined with significant impedance changes indicates the electrode array touching and/or impeding the basilar membrane. With this event-related ECochG and impedance categorization a comparison can be made in intracochlear changes between manual and robot assisted CI insertion.

Conclusion: The event-related approach using simultaneous multifrequency ECochG and impedance recording gives the surgeon a better insight in the induced intracochlear changes during insertion. Continuous monitoring can be of true value for optimizing both robot assisted and manual insertion trajectories and therewith minimizing intracochlear damage.

The round window (RW) and promontory represent attractive cochlear interfaces for inner ear stimulation and electrophysiological assessment. Due to its low electrical impedance and direct access to the scala tymani, the RW provides an efficient and minimally invasive pathway for electrical stimulation in patients with tinnitus, residual hearing, or borderline indications for cochlear implantation (CI). In addition, RW and promontory electrocochleography (ECochG) recordings enable reliable assessment of cochlear and neural function without intracochlear electrode insertion.

Compared with intracochlear ECochG measurements obtained during CI electrode insertion, RW or promontory ECochG offers several advantages: preservation of cochlear integrity, avoidance of insertion-related trauma, stable recording conditions independent of electrode position, and applicability in non-implanted ears. These extracochlear approaches may therefore provide a valuable tool for preoperative cochlear health assessment, patient selection, hearing preservation strategies, and monitoring of inner ear function in emerging electrotherapeutic indications.

Goals
Access to diagnostic testing for cochlear implant [CI] clinics, including integrity testing, has been limited by the difficulty of analysing relevant data. We introduced in-house Recording of Electrode Voltages [REVs] using surface electrodes six years ago and have collected data from > 200 Nucleus devices.
We aim to automate differential diagnosis of common CI issues, including electrode faults, insertion issues and anatomical differences by developing a REVs analysis app.
Material and Methods
Ethical approval for the study was granted by the University of Southampton (reference 79665) and National Research Ethics Service (reference 312360).
EV recordings were made in common ground mode for 215 CIs ranging from CI24M to CI600 series. Anatomy and electrode insertion details were found from pre- and post-operative radiological reports and surgeons’ notes.
An app was developed, offering visualisation and quality control of EV recordings. Traces are screened for noise and baseline drift is corrected. Electrode function is assessed by fitting a fifth order polynomial function to the average voltage during the first phase of stimulation for individual electrodes.
A machine learning model was developed with nine targets: normal, faulty electrodes, tip rollover, abnormal anatomy, partial insertion, fibrosis/ossification, combined faulty electrodes with abnormal anatomy/ossification, over-insertion, Nucleus double array. Together these form a pipeline for analysis.
Results
Cochlear implant recipients were 2.9-88.8 years old at the time of testing; devices ranged from 0.1-27.8 years old. 200/215 devices were normally inserted; anatomy was normal for 161 cochleae. EVs were a good fit to a 5th order polynomial (R2 > 0.995) for 105 devices, suggesting good electrode function. EVs for 12 devices were atypical due to abnormal anatomy.
EV data contains clear discriminative patterns for different clinical issues. The initial machine learning model shows good separation between issues.
Conclusion
The machine learning model would benefit from more data, especially for less common issues, and for this we would like to extend the study to include more centres.
Automated differential diagnosis of common CI issues is within our grasp. Introduction of this test into CI clinics in the future will empower clinicians and improve outcomes for recipients.

Objective:
This prospective study investigated the spread of excitation (SOE) and voltage matrix (VM) to evaluate their suitability for detecting intracochlear electrode malpositions in MED-EL cochlear implants (CI). In a subsequent retrospective study, intraoperatively measured voltage matrices were analyzed to develop an algorithm capable of identifying correct electrode positioning, tip fold-over, and basal kinking. The availability of such an algorithm would be valuable in clinical routine, as incorrect positioning of the electrode array could be recognized and corrected intraoperatively.

Methods:
In the prospective part of the study, SOE and VM were measured intraoperatively in 25 MED-EL CI recipients. In the subsequent retrospective study, intraoperative VMs from 525 MED-EL CI recipients were analyzed. In both studies, electrode position was assessed using postoperative digital volume tomography imaging. Based on these data, a VM-based algorithm was developed.

Results:
Both SOE and VM measurements are, in principle, suitable for assessing electrode position in MED-EL cochlear implants; however, VM offers several advantages. First, VM measurements can be performed more quickly. Second, in a significant number of cases, SOE measurements do not provide a complete ECAP profile, which is necessary for reliable position assessment.

Analysis of 525 postoperative images revealed seven incorrect electrode positions (1.3%; three cases of tip fold-over and four cases of basal kinking).

The VM-based algorithm yielded the following results: for detecting correct positioning, sensitivity was 99.6%, specificity 83.3%, and positive predictive value (PPV) 99.8%. For detecting tip fold-over, sensitivity was 100%, specificity 99.8%, and PPV 75%. For detecting basal kinking, sensitivity was 66%, specificity 99.8%, and PPV 66%.

Conclusion:
The VM-based algorithm proved to be an effective screening tool for detecting tip fold-over.

Goals:
This study addresses anatomic and conditional changes after cochlear implant (CI) surgery and their impact on peripheral sound transmission. We aimed to leverage deep learning to quantify post-operative effusion (PoE) from CT scans and evaluate its relationship with wideband acoustic immittance (WAI).

Methods:
We developed an automated pipeline using nnUNet-based neural networks to segment the middle ear (ME), ossicles, temporal bone (TB), and external auditory canal (EAC) on pre- and post-operative CT scans. Models were trained on 27 CI patients with 20% of data held out for cross validation. Preoperative scans and corresponding labels were then registered to postoperative scans. K-means clustering subsequently classified voxels within TB and ME regions on both scans into bone, effusion, or air, enabling quantification of PoE metrics. The regions surrounding the ossicles and tympanic membrane (TM), derived from EAC/ME segmentations, were also analyzed. For a subset of 16 CI participants, WAI was performed before surgery and within one week of the CT scan. The average absorbance was calculated across 0.25 - 8 kHz and split into 3 frequency bands (0.25 - 0.8 -low, 0.8 – 2 -mid, 2 - 8 kHz -high).

Results:
NN segmentation performance on cross-validation, assessed using Dice similarity coefficients (DSC), was strong (TB 0.96, ME 0.88, ossicles 0.97, EAC 0.92). Correlations with WAI demonstrated that increased ME effusion volume was associated with decreased absorbance, strongest at mid WAI frequencies (r ≈ –0.68, p < 0.001). Increased ME aeration, (volume and percent), was associated with higher absorbance, particularly in the mid-frequency range (r ≈ 0.69–0.71, p < 0.001). Similar trends were observed for aeration around TM and ossicles, which showed moderate positive correlations with absorbance (r ≈ 0.48–0.76, p < 0.05). Overall changes in effusion and aeration within the entire TB, including voxels aerated preoperatively that developed effusion postoperatively, showed weaker correlations with WAI.

Conclusion:
We developed an accurate, automated deep learning method for quantifying PoE-related metrics in CI patients. Correlation with WAI supports the importance of analyzing the ME environment in post-CI auditory outcomes, especially in mid frequency WAI ranges. This platform enables scalable, objective investigation of effusion-related hearing changes and may further our understanding of hearing preservation and inform CI programming timelines.

Goals: The improved recording electronics of Cochlear’s NEXA implant perform the measurement of impedances at 13 time samples during the stimulation pulse, a transimpedance matrix (TIM) and 4-point impedances between neighboring electrode contacts in less than half a minute. This allows one to systematically measure them at a range of current levels within an acceptable time. Fitting these measurements to an impedance model of the cochlea [1], the current dependence of the subcomponents of the impedance (polarization impedance, near-field and far-field resistance) can be studied, which is crucial to evaluate the consistency of the impedance measurements and the modeling.
Materials and Methods: Impedance data have been collected at surgery and at the clinical CI-programming visits up to at least 3 months post-implantation on 15 adult subjects with a NEXA implant. In addition, data have been recorded on 4 experienced NEXA users at a single postoperative visit (13–31 months). All implants had a Slim Modiolar electrode. Stimulation current was varied by a factor of 8 for measurements at surgery (80 CL–200 CL, step 20 CL). Postoperatively, the current range typically spanned a factor of 3 (80 CL–140 CL, step 10 CL), depending on the subject’s highest comfortable level.
Results: For the cases analyzed thus far, the far- and near-field resistance was independent of current within an accuracy of a few percent for both intra- and postoperative measurements. At surgery the Faradaic resistance (RF), associated with the electrode–tissue interface, strongly decreased (>3) with increasing current over the tested range, whereas the Warburg capacitance remained stable up to 140 CL and then rose by 50% towards 200 CL. However, data from cases more than 1 year after surgery showed electrode sections where RF strongly depends on current as for the intraoperative data, while at other sections it exhibits weaker or almost no current dependence. The location of the electrode sections with weaker and stronger current dependence appeared to be subject dependent. A systematic analysis of the whole data set is underway.
Conclusion: If in the analysis of the full data set a systematic postoperative evolution towards electrode regions with weak and strong current dependence for RF could be confirmed, this might be another potential parameter for monitoring clinical changes after cochlear implantation.

Goals:
Cochlear implants (CIs) have proven to be highly effective neural prostheses, widely used to restore hearing in individuals with sensorineural hearing loss. However, following implantation, CIs can trigger an immune response that leads to cell layer formation (fibrosis) in the cochlea causing low stimulation efficiency and suboptimal clinical outcomes. Electrochemical Impedance Spectroscopy (EIS) offers a powerful method for assessing the functionality of CI both during and after surgery. However, it’s full potential, particularly in analyzing the electrical properties of CIs, detecting the cell layer and distinguishing between different cell types, remains unutilized. This study aims to develop and validate an equivalent electrical circuit (EEC) model that accurately represents the electrical properties of CI electrodes and can reliably detect formation of cell layer on a CI electrode array.

Material and Methods:
The study involves four CI electrode arrays from different manufacturers (MED-EL, Advanced Bionics, Oticon, and Cochlear). Impedance measurements were conducted using an HP4192A impedance analyzer in a frequency range from 5 Hz to 13 MHz. The electrical equivalent circuit (EEC) of the CI electrodes was modelled, involving linear elements, as well as the electrode-electrolyte interface, using two non-linear bilayer models (Cole-Cole and Schwan-Faraday). A layer of human mesenchymal stromal cells (MSCs) was developed on the CI electrodes and impedance measurements were conducted to analyze changes in the impedance.

Results:
A general nonlinear electric element circuit model applicable to all types of CIs was derived that allows the determination of local impedances between neighboring CI array electrodes with an accuracy of < 10%. Our cell layer experiments demonstrated a clear increase in impedance across the frequency range when a layer of cells was present on the CI electrode. This increase was reversed after enzymatic cleaning, confirming that the observed impedance changes were due to the cell layer. These findings validate the use of impedance spectroscopy for detecting biological layers on cochlear implant electrodes.

Conclusion:
Our study developed and validated an EEC model to describe the electrical properties of CI electrode arrays along with its ability to detect presence of cell layer on CI electrodes using precision impedance spectroscopy.

Goals
This study investigated cervical and ocular vestibular-evoked myogenic potentials elicited by electrical stimulation from straight lateral wall cochlear implant (CI) electrodes (e-cVEMPs and e-oVEMPs). The focus was on comparing response rates, amplitudes, latencies, and thresholds across different CI stimulation electrodes.

Materials and Methods
E-VEMPs were recorded in 19 adult Synchrony (MED-EL, Austria) CI patients (20 ears) with straight lateral wall Flex electrodes, using electric pulse trains. Stimulation sites were varied between apical (E3), medial (E6), and basal (E10, E11) electrodes and stimulation levels were chosen according to the upper comfortable level of individually perceived loudness. E-VEMP thresholds were measured, if responses were present. Bone-conducted vibration (BCV) VEMPs served as a reference.

Results
E-VEMPs were successfully elicited in 95% of cases (18/20), compared to 60% for BCV-VEMPs. Basal stimulation (E10/E11) yielded significantly higher response rates than medial or apical stimulation. E-VEMP thresholds for basal electrodes were within clinical fitting ranges and, in some cases, even below the auditory threshold. E-VEMP amplitudes for basal stimulation were comparable to stimulation by BCV, e-VEMP latencies were shorter compared to VEMP latencies for BCV stimulation.

Conclusion
The study was limited to Synchrony CIs and Flex electrodes and did not include different types of straight lateral wall electrodes by other manufacturers. However, the high prevalence of e-VEMPs (95%) demonstrates frequent vestibular co-stimulation by lateral wall electrodes in this cohort, particularly at basal stimulation electrodes. Since this activation can occur even before stimuli become audible, vestibular co-stimulation is likely a common occurrence during daily CI use, though its functional impact remains to be determined.

Goals
Our understanding of the human ossicular chain’s 3D vibrations in response to acoustic stimuli relies on earlier work that assumes the middle ear ossicles to be rigid. However, this contrasts the conclusion of other work suggesting the ossicles have some degree of flexibility, especially in the higher frequencies. The recent introduction of Optical Coherence Tomography vibrometry (OCTv) in the field of hearing mechanics now enables spatially dense, spatially-resolved vibration measurements of the ossicular chain. The extension to 3D OCTv resolves all components of ossicular motion in 3D space, offering a means to directly test the assumption of ossicular rigidity.
Materials & Methods
We developed an experimental setup for 3D OCTv measurements in a human temporal bone using a single OCT scanning head, mounted on a 6 degrees of freedom robot arm that allows rotating the beam around a stationary specimen. Optically accessible regions of interest (ROI) were measured, with three measurements at each ROI along a slightly different optical axis. The relative orientations within ROIs and between ROIs were defined with a pose alignment algorithm on surface point clouds extracted from the OCT measurements and a μCT-scan segmentation, respectively.
Results
Ossicular rigidity was assessed by fitting a rigid body model to the 3D velocities at each stimulus frequency for each ossicle. The model was fitted in a least-squares sense to the surface velocities of all available ROIs, yielding a highly overdetermined system. A point-wise analysis of the model fit residuals yields a spatially resolved residual velocity field that allows a quantification of deviation from rigidity.
Conclusion
3D OCTv enables spatially dense, 3D-motion measurement of ossicular vibrations, enabling a rigorous and direct test of the rigid body assumption that underlies current models of middle ear mechanics. This framework has the sensitivity to detect localised, frequency-dependent ossicular flexibility — a question that has remained unresolved due to the limitations of conventional vibrometry approaches.

Goals
Intracochlear cochlear implant (CI) electrode array (EA) position has been known to impact post-operative hearing outcomes; serving as measure for CI trauma assessment. Current tools for CI trauma assessment have limitations including significant user input, restricted to proprietary EAs, and lack of distance metrics between EA and intracochlear structures. Our aim was to create an automated, manufacturer agnostic tool (ICAT) that segments the EA and cochlea within post-operative CT scans (poCT), and overlays labels for the scala-tympani (ST), scala vestibuli/media (SVM), lateral wall (LW), modiolus, and basilar membrane (BM) to compute EA position relative to these intracochlear structures.

Material and Methods:
The tool uses two pipelines: 1) Cochlea and EA segmentations derived from poCT; 2) Intracochlear segmentations (listed above) derived from pre-operative CT. Pipeline 1 was created by training a neural network (nnUNet) on 50 labeled poCTs from CI patients. Pipeline 2 was developed using five co-registered 3D-xray microscopy and CT pairs of the cochlea from cadaveric temporal bones, augmented synthetically to train a separate nnUNet. The result of pipeline 2 is registered to pipeline 1 for EA position analysis. Cochlear duct length (CDL) is estimated by computing a centerline through ST generated from pipeline 2. For both pipelines, using five-fold cross validation, 20% of the training data were randomly isolated to create a testing dataset. Both pipelines were integrated within the open-source platform, Slicer3D.

Results:
Pipeline 1 achieved Dice similarity coefficients (DSC) of 0.94 for cochlea segmentation and 0.87 for EA segmentation. Pipeline 2 achieved DSCs of 0.96, 0.95, 0.83, 0.86, and 0.91 for ST, SVM, BM, modiolus, and LW respectively. On a subset of LW CIs (N=6), ICAT found that, on average, 89.7% EA was in the ST, 6.3% in LW, and 3.4% SVM. Within this subset, mean EA distances to BM, LW, and modiolus were 0.50[-0.42-1.26] mm, 0.61[0.03-1.63] mm, and 1.26 [0.4-2.91]mm, respectively. Additionally, ICAT captures distance metrics as a function of percent of CDL (0% = base, 100%=apex); the average minimum distance to BM, LW, and modiolus occurred at 62%, 45%, 36% of the CDL.

Conclusion:
We created an accurate, fully automated CI trauma assessment tool that is EA-agnostic. This platform facilitates reproducible, large-scale analysis to guide surgical and programming strategies aimed at improving CI outcomes.

The study of sound transmission through the human middle ear is highly challenging due to the small size, deep location in the temporal bone, and subtle movements of its three ossicles. However, recent studies have shown the potential of dynamic synchrotron-based phase-contrast microtomography for investigating ossicular and tympanic membrane motion within healthy human ear samples. Here, we build on prior studies to investigate the biomechanics of the middle ear in its natural state, after footplate fixation and after stapedotomy.
Dynamic synchrotron-based X-ray phase-contrast microtomography was performed on a healthy human ear, after fixation of the footplate using histoacryl glue and after reconstructive surgery. Surgery was performed at the beamline by means of an endoscopic laser stapedotomy. Data were acquired using the GigaFRoST camera with a 2 kHz framerate, yielding a 2.75 μm voxel size. A post-gating algorithm was used for time-resolved analysis of micromotions during 128 Hz acoustic stimulation at 110 and 120 dB sound pressure level.
This approach enabled us to observe an ossicular chain fixation due to the application of histoacryl glue and restoration of ossicular chain movements after successful surgery. A volumetric, time-resolved approach is presented along with preliminary results of quantitative and a qualitative prosthesis movement. The 4D visualisation of sound transmission in healthy and reconstructed middle ears may help otologic surgeons better understand how surgical parameters affect ossicular chain movements and may guide future prosthesis design.