Objective: Mechanical stimulation of the cochlear round window (RW) extends the indication of active middle-ear implants to mixed and conductive hearing loss, yet outcomes vary considerably due to transducer-RW size mismatch and uncontrolled preload. The Hannover Coupler version 2 (HC2) addresses these issues with a small tip and a force indicator. This study further evaluates the effect of HC2 tip size on RW stimulation efficiency under controlled preload force. Methods: Stapes displacements were measured in six human temporal bones using laser Doppler vibrometry during acoustic and RW stimulation. The RW was stimulated by a floating mass transducer (FMT) with three HC2 tip diameters: small (0.5 mm), medium (0.7 mm), and large (1.0 mm). RW preload ranged from 4 to 60 mN. Results: The large HC2 tip produced the highest transfer function magnitude and average equivalent sound pressure level across speech-relevant frequencies (0.5-4 kHz), peaking at a preload of 30 mN-approximately 11 dB higher than the small tip. Differences between large and small tips were significant at nearly all preload, whereas medium and small tips showed no significant differences. Optimal preload for FMT depended on coupler tip size: 15 mN (small), 25 mN (medium), and 30 mN (large). Conclusion: RW stimulation efficiency increases with HC2 tip size. The large tip provides the highest output and lowest RW membrane stress, reducing penetration risk. FMT stimulation with different HC2 tip sizes has distinct optimal preload. These findings support the use of a larger HC2 tip to improve clinical outcomes in RW stimulation.

Cochlear implants (CIs) enable hearing via direct electrical stimulation of the spiral ganglion neurons (SGN). Outcomes with a CI depend, in part, on the number and excitability of the SGNs. In an animal model, we introduced the Failure Index (FI) as an electrically-evoked compound action potential (eCAP)-derived marker of cochlear health. The FI informs about the presence, site, and size of SGN lesions. Here, we translated the FI to clinical recordings from human MED-EL CI users. In this retrospective study, we included patient data recorded between 2016 and 2024 from 199 ears with postlingual hearing loss and 79 ears with prelingual hearing loss. The averaged FI values over all contacts of the array were stable within the analysis period (3 rd month to 1 st year postoperatively). The FI increased with age and was elevated in etiologies associated with higher SGN loss. Using 3D reconstruction from cone-beam computed tomography scans, we confirmed that the FI was independent of electrode-to-modiolus distance (0.1–2.5 mm). The FI showed individual patterns along the array, with maxima usually found at basal contacts, corresponding to reduced neural health at high-frequency cochlear regions. In a selected group of postlingual-deaf ears, we found higher correlation coefficients between speech-perception scores and the FI compared to other eCAP-derived markers (i.e., threshold, slope, and amplitude). These results were in line with the hypothesis that the FI may serve as a clinical tool to identify implanted ears with reduced neural health and to identify contacts stimulating areas of reduced SGN survival and integrity.

OBJECTIVES:Accurate identification of the specific inner ear malformations can assist the otologist in anticipating surgical challenges and potentially optimizing postoperative hearing outcomes. In this study, we explored the feasibility of applying similar cochlear morphology principles, that is, ones based on easily quantifiable measurements of the basal turn, to differentiate normal lateral wall geometry from malformed variants. DESIGN:We retrospectively collected 60 patients who underwent cochlear implantation in our center between 2005 and 2023 in the presence of a preoperatively recognized inner ear malformation. Of the 120 analyzed cochleae, 111 were eligible for segmentation, which included 8 cochlear hypoplasia type II, 15 cochlear hypoplasia type III, 2 cochlear hypoplasia type V, 38 Incomplete partition type I, 44 Incomplete partition type II, and 4 incomplete partition type III. A control cohort of 141 normal cochleae was selected. Using manual segmentation of the cochlea on preoperative cone beam computed tomography scans, three-dimensional lateral wall spirals were obtained. The spirals were then used to compute simple anatomical measures of the basal turn, namely the cochlear diameter A and width B, the basal turn length computed based on A and B using the elliptic circular approximation approach, the ratio B/A and the B ratio, and cochlear height (H). Initially, two-sided Mann-Whitney-Wilcoxon tests were conducted to derive statistical differences in the aforementioned geometrical parameters between normal and malformed anatomies. Second, logistic regression analyses were performed to define whether the derived geometrical parameters may be used to predict if a specific cochlear morphology is normal or malformed, and to subsequently investigate if such a model may even be capable of distinguishing between different malformation types. RESULTS:Four geometrical basal‑turn parameters easily assessable in clinical imaging, namely the basal turn length along the lateral wall, cochlear height (H), B/A ratio, and B‑ratio, provide enough information to reliably distinguish normal cochleae from malformed variants. The binary logistic model achieved 94% overall accuracy with precision and recall ≥0.92 across classes, with cochlear height H emerging as the dominant predictor. In our models, H and Bb/B were the strongest discriminants for normal versus malformed anatomies and for incomplete partitions versus cochlear hypoplasia, respectively. Moving beyond binary discrimination, the three‑class model (normal versus IP versus CH) retained 90% accuracy. In summary, the models reliably recognize normal versus malformed, incomplete partition versus cochlear hypoplasia, and CHIII among individual subtypes due to reduced height. They are less reliable for IPI versus IPII differentiation, where basal‑turn measures alone appear insufficient, and IPIII, CHII, CHIV, where very small sample sizes depress recall. CONCLUSIONS:Simple, basal‑turn measurements of the lateral wall were demonstrated to provide a fast, interpretable, and accurate means to detect cochlear malformations on clinical imaging and to differentiate IP from CH. The approach reliably flags abnormal cases, offers actionable preoperative information for patient‑tailored implantation, and identifies domains where additional features or larger cohorts are needed (IPI versus IPII; rare subtypes). Such a model could lay the groundwork for future automated recognition of cochlear malformations during preoperative planning.

The second generation of the Bonebridge (BB) bone conduction implant was shown to be a viable option even for younger children with conductive or mixed hearing loss. However, preoperative imaging often shows only small areas where the FMT (4.5 mm) or screws (4.0 mm) can be fully and safely inserted without the need to use lifts. Navigation systems allow precise placement of the device and prevent potential complications such as dural or vascular injuries. The latest version of the preoperative planning software Otoplan® allows to assess bone thickness and perform virtual implantation. Six children between 3 and 12 years of age underwent BB implantation using Otoplan® with export of the planned BB position to a navigation system. Prior to an intraoperative cone beam CT (CBCT), 3 marker screws were placed in the temporal bone. Images were loaded into Otoplan® to virtually define the optimal BB position and export the corresponding model. CBCT scan and model were then loaded into an electromagnetic navigation system. The screws were used to accurately register the system, and the planned BB placement was projected onto the patient. BB implantation was performed accordingly and finally the marker screws were removed. Possible complications were monitored and the audiological success was measured using an age-appropriate speech test. Bone thickness at the screw location was over 4.0 mm in every case, documenting the accuracy of the procedure. No medical complications occurred intraoperatively, during the immediate hospital stay, or up to and including the initial fitting 4–6 weeks after implantation. Speech test results were greater than or equal to 90

Introduction Direct piston-stimulation of the oval window with a middle ear implant, following a stapedotomy or stapedectomy, is one treatment option for patients with otosclerosis. Here, we experimentally investigated whether increasing the surface area of the actuated piston enhances transmission efficiency in oval window (OW) stimulation. Methods Fresh-frozen human cadaveric temporal bones (N = 14) were used to evaluate the output of different oval window couplers (OWCs) of A = 0.38 mm², 1.26 mm2, 3.06 mm2 by intracochlear pressure difference measurements between scala vestibuli (PSV) and scala tympani (PST). Following stapedectomy, a piezoelectric transducer was used for OWC actuation. Additionally, a numerical model was also developed to estimate the output of the floating mass transducer (FMT, MEDEL, Austria). Results Across frequencies, the average pressure difference was 18 and 8 dB higher for the large and medium OWC compared to the small OWC, respectively. Statistical analyses showed significant differences (p < 0.05) between piston diameters across most frequencies. Numerical simulation results using the volume displacement at the OW showed smaller output differences from 0.3 to 10 kHz, indicating that leakage at open gaps after stapedectomy has to be taken into account. Conclusion Our findings confirm that, for active stimulation with an actuator, increasing the surface area of the OWC enhances output efficiency proportionally. Nevertheless, volume leakage at open gaps to the OW may contribute additionally.

INTRODUCTION:Preoperative anatomical assessment is essential to optimize the outcome of individualized cochlear implantation. Algorithms based on cochlear diameters simplify this evaluation. The new version of a surgical planning platform is capable of performing this determination automatically. Our study evaluated the robustness of automated measurements and compared individual differences between automated and manual measurements, including predicting cochlear duct length and insertion angles. MATERIALS AND METHODS:The preoperative cone beam CT scans of 55 MED-EL cochlear implant patients were analyzed. Using the surgical planning platform, the anatomical diameters were measured automatically and manually. The values were compared, as well as the predictions of the insertion angles and prediction of cochlear duct length. RESULTS:The analyses showed good agreement between manual and automatic measurements of cochlear diameters, with the exception of cochlear height, where a significant difference was observed. Some discrepancies were noted for the prediction of the cochlear length duct without, however, a significant impact. Predictions of insertion angles based on automated measurements were comparable to the postoperative evaluations, with no significant difference from the manual ones. DISCUSSION:The robustness of automated assessments is essential for integration into clinical practice. Automated measurements of cochlear dimensions are comparable to manual ones. However, image quality and the presence of anatomical abnormalities may influence the results. In this study, the evaluation of the insertion angle prediction was strengthened by comparison with postoperative results taking into account the actual insertion depth.

HYPOTHESIS:In bone conduction implantation, the position of the implant influences the audiological benefit of the patient. BACKGROUND:One way of treating hearing loss is the implantation of bone conduction implants (BCIs), which effectively transmit vibrations through the skull bone to the cochlea given that the implant transducer is securely fixated. Laboratory research on the efficacy of bone conduction sound transmission found that a closer proximity of the transducer to the ipsilateral cochlea yields significantly higher cochlear promontory vibrations and hence, higher stimulation efficacy. Up to now, this finding has not been reproduced using clinical data such as the functional or effective gain. METHODS:The present, retrospective study was conducted on a cohort of 28 BCI patients to correlate the implantation site of the BC transducer, derived from clinical postoperative imaging and defined in a standardized coordinate system, with maximum output values that are exclusively based on a novel calculation method only employing clinical audiological data. RESULTS:It could be shown that the efficacy of BCI stimulation is in fact correlated with the transducer distance to the cochlea, and that this correlation is frequency dependent. Furthermore, the longitudinal distance of the transducer and the ipsilateral external auditory canal is negatively correlated with the maximal output while the sagittal distance is not. CONCLUSION:The present study is hence the first one to clinically demonstrate the significance of BCI placement for maximizing patient benefit, which should be considered during the preoperative planning of bone conduction implantation.

IntroductionThe natural, tonotopic frequency distribution of the inner ear is typically described by the Greenwood function, which logarithmically projects the audible frequency spectrum onto the intracochlear basilar membrane. Recent developments in cochlear implant (CI) programming aim to improve sound quality and music perception through consideration of the frequency distribution as described by the Greenwood function when assigning frequency bands to the individual contacts of the electrode array. This approach is commonly referred to as anatomy-based fitting (ABF). However, empirical validation of the Greenwood function to accurately describe pitch as perceived by CI users is lacking.MethodsTwelve CI patients with single-sided deafness (SSD) participated in the study. A pitch matching task was conducted at four different appointments and with two different fitting maps (standard and ABF). At each test appointment, participants were asked to set the frequency of a pure tone presented through a loudspeaker to the pitch perceived when stimulated with the single contacts of the CI electrode array. The cochlear anatomy of the patients was reconstructed based on clinical imaging to derive the location of the stimulating contacts relative to the basilar membrane, allowing for the comparison of the pitch perceived by the patients to the frequency suggested by the Greenwood function for each stimulating contact.ResultsIn general, subjective pitch percepts were found to agree well with the frequency suggested by the Greenwood function independent of subject, contact, or applied fitting map. Differences between pitch matches and Greenwood were found to be not statistically significant. At least part of the outcomes of previous studies reporting a basal frequency shift can be explained by the tonotopic mapping functions applied within these studies.DiscussionThe present results suggest that the Greenwood function is well-suited for representing the tonotopic frequency distribution not only for normal hearing subjects but for CI recipients as well. Further advances in frequency mapping should also take the neural health of the cochlea into account, allowing for additional individualization of frequency mapping in CIs.

OBJECTIVE:By estimating the length of the cochlear duct, commercial software algorithms intend to support CI teams by the selection of the suitable electrode array length prior to cochlear implant (CI) surgery. In the present study center, predominantly 31.5 mm flexible electrode arrays are used for patients with radiologically regular cochleae. Routinely performed postoperative Stenvers x-ray detects complete insertion in all cases. The aim of this study was to test the accuracy of the commercial software algorithm in predicting the angular insertion depths for this specific CI group with deeply inserted electrodes. STUDY DESIGN:Retrospective cohort study. SETTING:University medical center, tertiary academic referral center. PATIENTS:Patients undergoing a cochlear implant surgery MED-EL FLEXsoft electrode array (Synchrony2, MED-EL, Innsbruck, Austria) between January 2019 and December 2022. INTERVENTION:Preoperative CT images for 72 CI ears with 31.5 mm flexible electrode arrays were examined using OTOPLAN, and the maximum insertion depth (maxAID) was estimated. Postoperatively, the actual maxAID was determined through Stenvers x-ray images. MAIN OUTCOME MEASURES:The preoperatively estimated maxAID demonstrated a correlation with the postoperatively measured maxAID (R = 0.45, p < 0.001) but deviated by 44.8° ± 8.4°. There is a systematic overestimation by OTOPLAN of the insertion depths for estimated values exceeding 720°. To address this, an optimal offset of 2.4 mm is identified when considering this parameter in estimating maxAID for depths exceeding 720°. CONCLUSION:OTOPLAN predicts AID outcomes in CI patients but may deviate in small cochleae (CDL < 35 mm).

Cochlear implants (CIs) enable hearing with the deafened ear, via direct, electrical stimulation of the spiral ganglion neurons (SGN). Thus, the outcome depends on the number and excitability of the SGNs. We recently established the electrically-evoked compound action potential (eCAP)-derived Failure Index (FI) as cochlear-health marker in the animal model. The FI informs about the presence, site, and size of a SGN lesion. Here, we translated the FI to clinical recordings of MED-EL CI users. For the retrospective study, we selected patient data from the database of the German Hearing Center Hannover recorded 2017 to 2024. We included 199 post-lingually and 79 pre-lingually deafened ears. Averaged FIs over all contacts of a CI were stable within the analysis period (3 rd month to 1 st year postoperatively). The FI increased with age and was elevated for etiologies associated with higher SGN loss. Utilizing 3D information from cone beam-computed tomography scans, we confirmed that the FI was independent of distance (0.1-2.5 mm) to the modiolus. The FI showed individual patterns along the array with maxima usually at basal contacts, corresponding to elevated SGN loss at high frequencies. In a selected group of post-lingually deaf ears, we confirmed the correlation of the FI with speech perception in quiet and in noise (n=28, r 2 =0.12-0.55). Thus, we propose the FI as promising clinical tool to identify CI-implanted ears with reduced neural health and contacts close to areas of SGN loss. Thereby, it can serve to guide speech-processor fitting to optimize CI outcomes.

HYPOTHESIS:Machine learning models can assist with the selection of electrode arrays required for optimal insertion angles. BACKGROUND:Cochlea implantation is a successful therapy in patients with severe to profound hearing loss. The effectiveness of a cochlea implant depends on precise insertion and positioning of electrode array within the cochlea, which is known for its variability in shape and size. Preoperative imaging like CT or MRI plays a significant role in evaluating cochlear anatomy and planning the surgical approach to optimize outcomes. METHODS:In this study, preoperative and postoperative CT and CBCT data of 558 cochlea-implant patients were analyzed in terms of the influence of anatomical factors and insertion depth onto the resulting insertion angle. CONCLUSIONS:Machine learning models can predict insertion depths needed for optimal insertion angles, with performance improving by including cochlear dimensions in the models. A simple linear regression using just the insertion depth explained 88% of variability, whereas adding cochlear length or diameter and width further improved predictions up to 94%.

ObjectivesDespite the success of cochlear implant (CI) surgery for hearing restoration, reducing CI electrode insertion forces is an ongoing challenge with the goal to further reduce post-implantation hearing loss. While research in this field shows that both friction and quasistatic pressure forces occur during CI insertion, there is a lack of studies distinguishing between these origins. The present study was conducted to analyze the contribution of both force phenomena during automated CI insertion.MethodsFive MED-EL FLEX28 CI electrode arrays were inserted into both a regular and uncoiled version of the same average scala tympani (ST). Both ST models had a pressure release hole at the apical end, which was kept open or closed to quantify pressure forces. ST models were filled with different sodium dodecyl sulfate (SDS) lubricants (1, 5, and 10% SDS, water). The viscosity of lubricants was determined using a rheometer. Insertions were conducted with velocities ranging from v= 0.125 mm/s to 2.0 mm/s.ResultsViscosity of SDS lubricants at 20°C was 1.28, 1.96, and 2.51 mPas for 1, 5, and 10% SDS, respectively, which lies within the values reported for human perilymph. In the uncoiled ST model, forces remained within the noise floor (maximum: 0.049 × 10−3 N ± 1.5 × 10−3 N), indicating minimal contribution from quasistatic pressure. Conversely, forces using the regular, coiled ST model were at least an order of magnitude larger (minimum: Fmax = 28.95 × 10−3 N, v = 1 mm/s, 10% SDS), confirming that friction forces are the main contributor to total insertion forces. An N-way ANOVA revealed that both lubricant viscosity and insertion speed significantly reduce insertion forces (p < 0.001).ConclusionFor the first time, this study demonstrates that at realistic perilymph viscosities, quasistatic pressure forces minimally affect the total insertion force profile during insertion. Mixed friction is the main determinant, and significantly decreases with increaseing insertion speeds. This suggests that in clinical settings with similar ST geometries and surgical preparation, quasistatic pressure plays a subordinate role. Moreover, the findings indicate that managing the hydrodynamics of the cochlear environment, possibly through pre-surgical preparation or the use of specific lubricants, could effectively reduce insertion forces.

Background The second generation of the bonebridge (BB) is widely used even in younger children. Preoperative imaging often reveals only small areas in which the FMT (4.5mm) or screws (2.5mm) can be fully and safely inserted. The use of navigation systems can enable precise placement of the device and prevent potential complications such as dural or vascular injuries. The most recent release of the preoperative planning software Otoplan enables the user to not only assess the bone thickness, but also to virtually implant the patient and export models of the implanted BB.

Einführung Die chirurgische Planungsplattform OTOPLAN nähert sich der Größe der Cochlea innerhalb klinischer Bildgebung an, indem sie die basalen Cochleardurchmesser misst und Eintrittswinkel für Elektrodenarrays von Cochlea-Implantaten vorhersagt. Diese retrospektive Studie zielte darauf ab, die Genauigkeit dieser Vorhersagen zu bewerten, indem sie sie mit Messungen der Länge der Cochlea-Seitenwand mittels multiplanarer Rekonstruktion (MPR) und automatisierten Softwaremessungen verglich.

Objective Preservation of residual hearing is one of the main goals in cochlear implantation. There are many factors that can influence hearing preservation after cochlear implantation. The purpose of the present study was to develop an algorithm for validated preoperative cochlear volume analysis and to elucidate the role of cochlear volume in preservation of residual hearing preservation after atraumatic cochlear implantation. Study design Retrospective analysis. Setting Tertiary referral center. Patients A total of 166 cochlear implant recipients were analyzed. All patients were implanted with either a MED-EL (Innsbruck, Austria) FLEXSOFT (n = 3), FLEX28 (n = 72), FLEX26 (n = 1), FLEX24 (n = 41), FLEX20 (n = 38), or FLEX16 (n = 11, custom made device) electrode array through a round window approach. Main outcome measures: Cochlear volume as assessed after manual segmentation of cochlear cross-sections in cone beam computed tomography, and preservation of residual hearing 6 months after implantation were analyzed. The association between residual hearing preservation and cochlear volume was then assessed statistically. Results Rapid and valid cochlear volume analysis was possible using the individual cross-sections and a newly developed and validated algorithm. Cochlear volume had the tendency to be larger in patients with hearing preservation than in those with hearing loss. Significant correlations with hearing preservation could be observed for the basal width and length of the basal turn. Conclusions Preservation of residual hearing after cochlear implantation may depend on cochlear volume but appears to be influenced more strongly by other cochlear dimensions.

Einleitung Die partielle Insertion ist ein operatives Verfahren, das bei Hochtonschwerhörigkeit das Hörvermögen im Tieftonbereich bewahrt und Elektroakustische Stimulation in hohen Frequenzen nutzt. Bei Hörverlust kann die Elektrode tiefer eingesetzt werden, um eine Reimplantation zu umgehen. Präoperative Planung mit Bildgebung und Hörschwelle ist für den Erhalt des Restgehörs wichtig.

Hintergrund Die zweite Generation der Bonebridge (BB) wird auch bei jüngeren Kindern häufig eingesetzt. Die präoperative Bildgebung zeigt oft nur kleine Bereiche, in denen FMT (4,5 mm) oder Schrauben (2,5 mm) vollständig und sicher eingebracht werden können. Der Einsatz von Navigationssystemen kann eine präzise Platzierung ermöglichen und potenzielle durale oder vaskuläre Komplikationen verhindern.

OBJECTIVES:During the insertion of cochlear implant (CI) electrode arrays, forces occur which may cause trauma and poorer hearing outcomes. Unfortunately, research groups investigating factors influencing insertion forces come to contradicting results, especially regarding insertion speed. This study was conducted to investigate the origin of these contradicting results and to determine how different testing conditions influence experimental findings. METHODS:Repeated, automated insertions with three different FLEX28 CI electrode arrays (MED-EL, Innsbruck, Austria) were performed into a newly developed, anatomically correct and 3D-printed mean scala tympani phantom. The testing protocol for each electrode included variations in insertion speed (v = 0.1-2.0 mm/s) and lubrication (90%, 50%, and 10% liquid soap), resulting in 51 insertions per electrode array and a total of 153 insertions. RESULTS:The test setup and protocol allowed for repeatable insertions with only minimal change in the morphology of the insertion force profiles per testing condition. Strong but varying dependencies of the maximal insertion forces and work were found regarding both lubrication and speed: work-speed dependency is constant for the 10% lubricant, negative for the 50% lubricant and positive for the 90% lubricant. CONCLUSION:Our results can explain part of the contradicting results found within previous studies by translating interrelations known from lubricated rubber friction to the field of CI electrode array insertion. We show that the main driver behind measured bulk forces are most likely the generated friction forces, which are strongly dependent on insertion speed and lubrication. The employed test setup allows for conducting repeatable and comparable insertion studies, which can be recapitulated by other centers due to the detailed explanation of the test setup as well as the developed and freely available insertion phantom. This study hence represents another important step toward standardizing CI array insertion testing.

IntroductionConductive hearing loss describes an insufficient sound transfer of the middle ear, often caused by defects or absence of the ossicles. Depending on the specific middle ear dimensions and the kind of defect, surgeons can choose from a variety of passive implants to reconstruct the middle ear and hence restore sound transmission. However, the latter is only achieved if the optimal implant size is available and selected for each individual patient.MethodsAnatomical dimensions relevant for middle ear reconstruction were assessed within high-resolution clinical imaging data of 50 patients (100 ears). The ranges of these dimensions were then compared to implant types and sizes available from different manufacturers.ResultsIn general, total and partial prostheses seem to cover the whole range of anatomical variations. A lack of stapesplasty implants was found for particularly small anatomies. Various implant lengths of all types far exceed dimensions necessary for successful restoration of sound transmission. In some cases, implant lengths are not clearly specified by the manufacturer. Tympanic membrane and stapes axis were not in line for any of the investigated middle ears.ConclusionClear specifications of implant lengths are crucial to allow for successful hearing restoration, and clinics often need to have more than one implant type to cover the entire range of anatomical variations they may encounter. There appears to be an unmet clinical need for smaller stapesplasty implants. Devices which allow for an angular adjustment between distal and proximal end appear to mimic the orientation of the ossicles more naturally.

Introduction The OTOPLAN surgical planning platform approximates cochlear size within clinical imaging data by measuring basal cochlear diameters and predicts insertion angles for cochlear implant electrode arrays. This retrospective study aimed to evaluate the accuracy of these predictions, comparing them with cochlear side wall length measurements by multiplanar reconstruction (MPR) and automated software measurements.