Cochlear Implant Insertion Depth Prediction: A Temporal Bone Accuracy Study

Hampshire Sheep as a Large-Animal Model for Cochlear Implantation

BACKGROUND

Sheep have been proposed as a large-animal model for studying cochlear implantation. However, prior sheep studies report that the facial nerve (FN) obscures the round window membrane (RWM), requiring FN sacrifice or a retrofacial opening to access the middle-ear cavity posterior to the FN for cochlear implantation. We investigated surgical access to the RWM in Hampshire sheep compared to Suffolk-Dorset sheep and the feasibility of Hampshire sheep for cochlear implantation via a facial recess approach.

METHODS

Sixteen temporal bones from cadaveric sheep heads (ten Hampshire and six Suffolk-Dorset) were dissected to gain surgical access to the RWM via an extended facial recess approach. RWM visibility was graded using St. Thomas' Hospital (STH) classification. Cochlear implant (CI) electrode array insertion was performed in two Hampshire specimens. Micro-CT scans were obtained for each temporal bone, with confirmation of appropriate electrode array placement and segmentation of the inner ear structures.

RESULTS

Visibility of the RWM on average was 83% in Hampshire specimens and 59% in Suffolk-Dorset specimens (p = 0.0262). Hampshire RWM visibility was Type I (100% visibility) for three specimens and Type IIa (> 50% visibility) for seven specimens. Suffolk-Dorset RWM visibility was Type IIa for four specimens and Type IIb (< 50% visibility) for two specimens. FN appeared to course more anterolaterally in Suffolk-Dorset specimens. Micro-CT confirmed appropriate CI electrode array placement in the scala tympani without apparent basilar membrane rupture.

CONCLUSIONS

Hampshire sheep appear to be a suitable large-animal model for CI electrode insertion via an extended facial recess approach without sacrificing the FN. In this small sample, Hampshire specimens had improved RWM visibility compared to Suffolk-Dorset. Thus, Hampshire sheep may be superior to other breeds for ease of cochlear implantation, with FN and facial recess anatomy more similar to humans.

Estimation of Cochlear Implant Insertion Depth Using 2D-3D Registration of Postoperative X-Ray and Preoperative CT Images

OBJECTIVE

To improve estimation of cochlear implant (CI) insertion depth in postoperative skull x-rays using synthesized information from preoperative CT scans.

STUDY DESIGN

Retrospective cohort.

SETTING

Tertiary referral center.

PATIENTS

Ten adult cochlear implant recipients with preoperative and postoperative temporal bone computed tomography (CT)scans and postoperative skull x-ray imaging.

INTERVENTIONS

Postoperative x-rays and digitally reconstructed radiographs (DRR) from preoperative CTs were registered using 3D Slicer and MATLAB to enhance localization of the round window and modiolus. Angular insertion depth (AID) was estimated in unmodified and registration-enhanced x-rays and DRRs in the cochlear view. Linear insertion depth (LID) was estimated in registered images by two methods that localized the proximal CI electrode or segmented the cochlea. Ground truth assessments were made in postoperative CTs.

MAIN OUTCOME MEASURES

Errors of insertion depth estimates were calculated relative to ground truth measurements and compared with paired t t ests. Pearson correlation coefficient was used to assess inter-rater reliability of two reviewer's measurements of AID in unmodified x-rays.

RESULTS

In postoperative x-rays, AID estimation errors were similar with and without registration enhancement (-1.3 ± 20.7° and -4.8 ± 24.9°, respectively; mean ± SD; p = 0.6). AID estimation in unmodified x-rays demonstrated strong interrater agreement (ρ = 0.79, p < 0.05) and interrater differences (-15.0 ± 35.3°) comparable to estimate errors. Registering images allowed measurement of AID in the cochlear view with estimation errors of 14.6 ± 30.6° and measurement of LID, with estimate errors that were similar between proximal electrode localization and cochlear segmentation methods (-0.9 ± 2.2 mm and -2.1 ± 2.7 mm, respectively; p = 0.3).

CONCLUSIONS

2D-3D image registration allows measurement of AID in the cochlear view and LID using postoperative x-rays and preoperative CT imaging. The use of this technique may reduce the need for postimplantation CT studies to assess these metrics of CI electrode position. Further work is needed to improve the accuracy of AID assessment in the postoperative x-ray view with registered images compared with established methods.

Comparing linear and non-linear models to estimate the appropriate cochlear implant electrode array length-are current methods precise enough?

PURPOSE

In cochlear implantation with flexible lateral wall electrode arrays, a cochlear coverage (CC) range between 70% and 80% is considered ideal for optimal speech perception. To achieve this CC, the cochlear implant (CI) electrode array has to be chosen according to the individual cochlear duct length (CDL). Here, we mathematically analyzed the suitability of different flexible lateral wall electrode array lengths covering between 70% and 80% of the CDL.

METHODS

In a retrospective cross-sectional study preoperative high-resolution computed tomography (HRCT) from patients undergoing cochlear implantation was investigated. The CDL was estimated using an otosurgical planning software and the CI electrode array lengths covering 70-80% of the CDL was calculated using (i) linear and (ii) non-linear models.

RESULTS

The analysis of 120 HRCT data sets showed significantly different model-dependent CDL. Significant differences between the CC of 70% assessed from linear and non-linear models (mean difference: 2.5 mm, p < 0.001) and the CC of 80% assessed from linear and non-linear models (mean difference: 1.5 mm, p < 0.001) were found. In up to 25% of the patients none of the existing flexible lateral wall electrode arrays fit into this range. In 59 cases (49,2%) the models did not agree on the suitable electrode arrays.

CONCLUSIONS

The CC varies depending on the underlying CDL approximation, which critically influences electrode array choice. Based on the literature, we hypothesize that the non-linear method systematically overestimates the CC and may lead to rather too short electrode array choices. Future studies need to assess the accuracy of the individual mathematical models.

Postoperative Impedance-Based Estimation of Cochlear Implant Electrode Insertion Depth

OBJECTIVES

Reliable determination of cochlear implant electrode positions shows promise for clinical applications, including anatomy-based fitting of audio processors or monitoring of electrode migration during follow-up. Currently, electrode positioning is measured using radiography. The primary objective of this study is to extend and validate an impedance-based method for estimating electrode insertion depths, which could serve as a radiation-free and cost-effective alternative to radiography. The secondary objective is to evaluate the reliability of the estimation method in the postoperative follow-up over several months.

DESIGN

The ground truth insertion depths were measured from postoperative computed tomography scans obtained from the records of 56 cases with an identical lateral wall electrode array. For each of these cases, impedance telemetry records were retrieved starting from the day of implantation up to a maximum observation period of 60 mo. Based on these recordings, the linear and angular electrode insertion depths were estimated using a phenomenological model. The estimates obtained were compared with the ground truth values to calculate the accuracy of the model.

RESULTS

Analysis of the long-term recordings using a linear mixed-effects model showed that postoperative tissue resistances remained stable throughout the follow-up period, except for the two most basal electrodes, which increased significantly over time (electrode 11: ~10 Ω/year, electrode 12: ~30 Ω/year). Inferred phenomenological models from early and late impedance telemetry recordings were not different. The insertion depth of all electrodes was estimated with an absolute error of 0.9 mm ± 0.6 mm or 22° ± 18° angle (mean ± SD).

CONCLUSIONS

Insertion depth estimations of the model were reliable over time when comparing two postoperative computed tomography scans of the same ear. Our results confirm that the impedance-based position estimation method can be applied to postoperative impedance telemetry recordings. Future work needs to address extracochlear electrode detection to increase the performance of the method.

Accuracy of Preoperative Cochlear Duct Length Estimation and Angular Insertion Depth Prediction

OBJECTIVE

In cochlear implantation with flexible lateral wall electrodes, a cochlear coverage of 70% to 80% is assumed to yield an optimal speech perception. Therefore, fitting the cochlear implant (CI) to the patient's individual anatomy has gained importance in recent years. For these reasons, the optimal angular insertion depth (AID) has to be calculated before cochlear implantation. One CI manufacturer offers a software that allows to visualize the AID of different electrode arrays. Here, it is hypothesized that these preoperative AID models overestimate the postoperatively measured insertion angle. This study aims to investigate the agreement between preoperatively estimated and postoperatively measured AID.

STUDY DESIGN

Retrospective cross-sectional study.

SETTING

Single-center tertiary referral center.

PATIENTS

Patients undergoing cochlear implantation.

INTERVENTION

Preoperative and postoperative high-resolution computed tomography (HRCT).

MAIN OUTCOME MEASURES

The cochlear duct length was estimated by determining cochlear parameters ( A value and B value), and the AID for the chosen electrode was (i) estimated by elliptic circular approximation by the software and (ii) measured manually postoperatively by detecting the electrode contacts after insertion.

RESULTS

A total of 80 HRCT imaging data sets from 69 patients were analyzed. The mean preoperative AID estimation was 662.0° (standard deviation [SD], 61.5°), and the mean postoperatively measured AID was 583.9° (SD, 73.6°). In all cases (100%), preoperative AID estimation significantly overestimated the postoperative determined insertion angle (mean difference, 38.1°). A correcting factor of 5% on preoperative AID estimation dissolves these differences.

CONCLUSIONS

The use of an electrode visualization tool may lead to shorter electrode array choices because of an overestimation of the insertion angle. Applying a correction factor of 0.95 on preoperative AID estimation is recommended.

Cochlear implant electrode impedance subcomponents as biomarker for residual hearing

Introduction and objectives

Maintaining the structural integrity of the cochlea and preserving residual hearing is crucial for patients, especially for those for whom electric acoustic stimulation is intended. Impedances could reflect trauma due to electrode array insertion and therefore could serve as a biomarker for residual hearing. The aim of this study is to evaluate the association between residual hearing and estimated impedance subcomponents in a known collective from an exploratory study.

Methods

A total of 42 patients with lateral wall electrode arrays from the same manufacturer were included in the study. For each patient, we used data from audiological measurements to compute residual hearing, impedance telemetry recordings to estimate near and far-field impedances using an approximation model, and computed tomography scans to extract anatomical information about the cochlea. We assessed the association between residual hearing and impedance subcomponent data using linear mixed-effects models.

Results

The progression of impedance subcomponents showed that far-field impedance was stable over time compared to near-field impedance. Low-frequency residual hearing demonstrated the progressive nature of hearing loss, with 48% of patients showing full or partial hearing preservation after 6 months of follow-up. Analysis revealed a statistically significant negative effect of near-field impedance on residual hearing (-3.81 dB HL per kΩ; p < 0.001). No significant effect of far-field impedance was found.

Conclusion

Our findings suggest that near-field impedance offers higher specificity for residual hearing monitoring, while far-field impedance was not significantly associated with residual hearing. These results highlight the potential of impedance subcomponents as objective biomarkers for outcome monitoring in cochlear implantation.

An intracochlear electrocochleography dataset - from raw data to objective analysis using deep learning

Electrocochleography (ECochG) measures electrophysiological inner ear potentials in response to acoustic stimulation. These potentials reflect the state of the inner ear and provide important information about its residual function. For cochlear implant (CI) recipients, we can measure ECochG signals directly within the cochlea using the implant electrode. We are able to perform these recordings during and at any point after implantation. However, the analysis and interpretation of ECochG signals are not trivial. To assist the scientific community, we provide our intracochlear ECochG data set, which consists of 4,924 signals recorded from 46 ears with a cochlear implant. We collected data either immediately after electrode insertion or postoperatively in subjects with residual acoustic hearing. This data descriptor aims to provide the research community access to our comprehensive electrophysiological data set and algorithms. It includes all steps from raw data acquisition to signal processing and objective analysis using Deep Learning. In addition, we collected subject demographic data, hearing thresholds, subjective loudness levels, impedance telemetry, radiographic findings, and classification of ECochG signals.

Virtual cochlear implantation for personalized rehabilitation of profound hearing loss

In cochlear implantation, current preoperative planning procedures allow for estimating how far a specific implant will reach into the inner ear of the patient, which is important to optimize hearing preservation and speech perception outcomes. Here we report on the development of a methodology that goes beyond current planning approaches: the proposed model does not only estimate specific outcome parameters but allows for entire, three-dimensional virtual implantations of patient-specific cochlear anatomies with different types of electrode arrays. The model was trained based on imaging datasets of 186 human cochleae, which contained 171 clinical computer tomographies (CTs) of actual cochlear implant patients as well as 15 high-resolution micro-CTs of cadaver cochleae to also reconstruct the refined intracochlear structures not visible in clinical imaging. The model was validated on an independent dataset of 141 preoperative and postoperative clinical CTs of cochlear implant recipients and outperformed all currently available planning approaches, not only in terms of accuracy but also regarding the amount of information that is available prior to the actual implantation.

Cochlear base length as predictor for angular insertion depth in incomplete partition type 2 malformations

INTRODUCTION

The preoperative determination of suitable electrode array lengths for cochlear implantation in inner ear malformations is a matter of debate. The choice is usually based on individual experience and the use of intraoperative probe electrodes. The purpose of this case series was to evaluate the applicability and precision of an angular insertion depth (AID) prediction method, based on a single measurement of the cochlear base length (CBL).

METHODS

We retrospectively measured the CBL in preoperative computed tomography (CT) images in 10 ears (8 patients) with incomplete partition type 2 malformation. With the known electrode length (linear insertion depth, LID) the AID at full insertion was retrospectively predicted for each ear with a heuristic equation derived from non-malformed cochleae. Using the intra- or post-implantation cone beam CT images, the actual AID was assessed and compared. The deviations of the predicted from the actual insertion angles were quantified (clinical prediction error) to assess the precision of this single-measure estimation.

RESULTS

Electrode arrays with 15 mm (n = 3), 19 mm (n = 2), 24 mm (n = 3), and 26 mm (n = 2) length were implanted. Postoperative AIDs ranged from 211° to 625°. Clinical AID prediction errors from -64° to 62° were observed with a mean of 0° (SD of 44°). In two ears with partial insertion of the electrode, the predicted AID was overestimated. The probe electrode was intraoperatively used in 9/10 cases.

CONCLUSION

The analyzed method provides good predictions of the AID based on LID and CBL. It does not account for incomplete insertions, which lead to an overestimation of the AID. The probe electrode is useful and well established in clinical practice. The investigated method could be used for patient-specific electrode length selection in future patients.

Robotics, automation, active electrode arrays, and new devices for cochlear implantation: A contemporary review

In the last two decades, cochlear implant surgery has evolved into a minimally invasive, hearing preservation surgical technique. The devices used during surgery have benefited from technological advances that have allowed modification and possible improvement of the surgical technique. Robotics has recently gained popularity in otology as an effective tool to overcome the surgeon's limitations such as tremor, drift and accurate force control feedback in laboratory testing. Cochlear implantation benefits from robotic assistance in several steps during the surgical procedure: (i) during the approach to the middle ear by automated mastoidectomy and posterior tympanotomy or through a tunnel from the postauricular skin to the middle ear (i.e. direct cochlear access); (ii) a minimally invasive cochleostomy by a robot-assisted drilling tool; (iii) alignment of the correct insertion axis on the basal cochlear turn; (iv) insertion of the electrode array with a motorized insertion tool. In recent years, the development of bone-attached parallel robots and image-guided surgical robotic systems has allowed the first successful cochlear implantation procedures in patients via a single hole drilled tunnel. Several other robotic systems, new materials, sensing technologies applied to the electrodes, and smart devices have been developed, tested in experimental models and finally some have been used in patients with the aim of reducing trauma in cochleostomy, and permitting slow and more accurate insertion of the electrodes. Despite the promising results in laboratory tests in terms of minimal invasiveness, reduced trauma and better hearing preservation, so far, no clinical benefits on residual hearing preservation or better speech performance have been demonstrated. Before these devices can become the standard approach for cochlear implantation, several points still need to be addressed, primarily cost and duration of the procedure. One can hope that improvement in the cost/benefit ratio will expand the technology to every cochlear implantation procedure. Laboratory research and clinical studies on patients should continue with the aim of making intracochlear implant insertion an atraumatic and reversible gesture for total preservation of the inner ear structure and physiology.

In-Vitro Study of Speed and Alignment Angle in Cochlear Implant Electrode Array Insertions

OBJECTIVE

The insertion of the electrode array is a critical step in cochlear implantation. Herein we comprehensively investigate the impact of the alignment angle and feed-forward speed on deep insertions in artificial scala tympani models with accurate macro-anatomy and controlled frictional properties.

METHODS

Motorized insertions (n=1033) were performed in six scala tympani models with varying speeds and alignment angles. We evaluated reaction forces and micrographs of the insertion process and developed a mathematical model to estimate the normal force distribution along the electrode arrays.

RESULTS

Insertions parallel to the cochlear base significantly reduce insertion energies and lead to smoother array movement. Non-constant insertion speeds allow to reduce insertion forces for a fixed total insertion time compared to a constant feed rate.

CONCLUSION

In cochlear implantation, smoothness and peak forces can be reduced with alignment angles parallel to the scala tympani centerline and with non-constant feed-forward speed profiles.

SIGNIFICANCE

Our results may help to provide clinical guidelines and improve surgical tools for manual and automated cochlear implantation.

Fabrication of human anatomy-based scala tympani models with a hydrophilic coating for cochlear implant insertion experiments

Electrode array insertion into the inner ear is a critical step in cochlear implantation, and artificial scala tympani models can be a valuable tool for studying the dynamics of this process. This technical note describes the fabrication of electrode array dummies and scala tympani models that address shortcomings of previously published cochlear models. In particular, we improve the reproduction of frictional properties with an easy-to-apply polymer brush coating that creates hydrophilic surfaces, and produce geometries with accurate macro-anatomy based on microtomographic scans. The presented methods rely only on commonly available materials and tools and are based on publicly available data. Our validation shows very good agreement of insertion forces both in terms of linear insertion depth and insertion speed compared to previously published measurements of insertions in cadaveric temporal bones.

Intraoperative Impedance-Based Estimation of Cochlear Implant Electrode Array Insertion Depth

OBJECTIVE

Cochlear implant impedances are influenced by the intracochlear position of the electrodes. Herein, we present an intuitive approach to calculate tissue resistances from transimpedance recordings, ultimately enabling to estimate the insertion depth of cochlear implant electrodes.

METHODS

Electrode positions were measured in computed-tomography images of 20 subjects implanted with the same lateral wall cochlear implant model. The tissue resistances were estimated from intraoperative telemetry data using bivariate spline extrapolation from the transimpedance recordings. Using a phenomenological model, the electrode insertion depths were estimated.

RESULTS

The proposed method enabled the linear insertion depth of all electrodes to be estimated with an average error of 0.76 ± 0.53 mm.

CONCLUSION

Intraoperative telemetry recordings correlate with the linear and angular depth of electrode insertion, enabling estimations with an accuracy that can be useful for clinical applications.

SIGNIFICANCE

The proposed method can be used to objectively assess surgical outcomes during and after cochlear implantation based on non-invasive and readily available telemetry recordings.

Preoperative prediction of angular insertion depth of lateral wall cochlear implant electrode arrays

Purpose: Cochlear implants (CIs) use an array of electrodes surgically threaded into the cochlea to restore hearing sensation. Techniques for predicting the insertion depth of the array into the cochlea could guide surgeons toward more optimal placement of the array to reduce trauma and preserve the residual hearing. In addition to the electrode array geometry, the base insertion depth (BID) and the cochlear size could impact the overall array insertion depth. Approach: We investigated using these measurements to develop a linear regression model that can make preoperative or intraoperative predictions of the insertion depth of lateral wall CI electrodes. Computed tomography (CT) images of 86 CI recipients were analyzed. Using previously developed automated algorithms, the relative electrode position inside the cochlea was measured from the CT images. Results: A linear regression model is proposed for insertion depth prediction based on cochlea size, array geometry, and BID. The model is able to accurately predict angular insertion depths with a standard deviation of 41 deg and absolute deviation error of 32 deg. Conclusions: Surgeons may use this model for patient-customized selection of electrode array and/or to plan a BID for a given array that minimizes the likelihood of causing trauma to regions of the cochlea where residual hearing exists.

Research software in cochlear duct length estimation, Greenwood frequency mapping and CI electrode array length simulation

Background and objective

The size of the cochlea varies a lot among the human population bringing the necessity for electrode arrays to be available in various lengths irrespective of the cochlear implant (CI) brand. This research software helps in the estimation of the patient's cochlear duct length (CDL) which is then used for the simulation of the correct length electrode array matching the patient's cochlear size and as well in getting the patient specific cochlear frequency map.

Methods

Visual Studio Express 2012 for Windows Desktop is used in the architecture of this research software. The basal turn diameter of the cochlea (“A” value) needs to be measured from the pre-operative computed tomography (CT) image of the patient's temporal bone. This “A” will be taken as the input for the CDL equations proposed by Alexiades et al for estimating the CDL along the basilar membrane for various insertion depths. Greenwood's equation is then used in combination with the CDL for the full length of the cochlea in getting the patient specific frequency map.

Results

The research software with the help of the “A” value as input, with few button clicks, gives the patient specific CDL for various insertion depths and the Greenwood's frequency map. The users have the choice to select any electrode array of their choice and place it under the frequency map to see how good it fits to that particular patient's cochlea. Also, given the possibility to drag and move the electrode array picture to mimic the post-operative actual electrode insertion depth.

Conclusions

This research software simplifies the overall process of CDL estimation and in getting the patient specific cochlear frequency map. The clinicians get the chance to simulate placing the various electrode array lengths in patient cochlea in identifying the best fit electrode. This could help in pushing the CI field into the concept of individualized CI electrode array solution that ultimately benefits the patients.

Clinical Applicability of a Preoperative Angular Insertion Depth Prediction Method for Cochlear Implantation

OBJECTIVE

Evaluation of the accuracy and clinical applicability of a single measure cochlear implant angular insertion depth prediction method.

BACKGROUND

Cochlear implantation outcomes still vary extensively between patients. One of the possible reasons could be variability in intracochlear electrode array placement. For this reason, single measure methods were suggested to preoperatively predict angular insertion depths. Based on a previously performed accuracy study in human temporal bones, we were interested in determining the extent to which the method could be applied in a clinical setting.

METHODS

A retrospective analysis was performed on pre- and postoperative radiographic images of 50 cochlear implant recipients. Preoperatively predicted angular insertion depths were compared with angular insertion depths measured on postoperative ground truth. The theoretical prediction error was computed under the assumption that all achieved insertions were matching the preoperatively assumed linear insertion depth. More importantly, the clinical prediction error was assessed using two different software tools performed by three experienced surgeons.

RESULTS

Using the proposed method we found a theoretical prediction error of 5 degrees (SD = 41 degrees). The clinical prediction error including the cases with extracochlear electrodes was 70 degrees (SD = 96 degrees).

CONCLUSIONS

The presented angular insertion depth prediction method is a first practical approach to support the preoperative selection of cochlear implant electrode arrays. However, the presented procedure is limited in that it is unable to predict the occurrence of insertion results with extracochlear electrodes and requires user training.

Human bony labyrinth dataset: Co-registered CT and micro-CT images, surface models and anatomical landmarks

The presented data set consists of images, labels and surface models of 23 human bony labyrinths. For each specimen clinical computed tomography (CT) and co-registered high-resolution micro-CT images were acquired. Using the images, the bony labyrinth was segmented and 3D surface models were generated. Each specimen is accompanied by a description file containing the coordinates of anatomical landmarks and the corresponding cochlear coordinate system. The data set can be used to study the morphology of the inner ear or to evaluate segmentation algorithm as used for the preoperative planning of surgical procedures such as cochlear implantation.

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

BACKGROUND

Endoscopic ear surgery is gaining increasing popularity and has an important impact on teaching middle ear anatomy and basic surgical skills among residents and fellows. Due to the wide-angled views offered, the approach significantly differs from the established microscopic technique. This randomized study compares the acquisition of basic ear-surgery skills using the endoscopic and microscopic technique under standardized conditions. We aim to investigate the required surgical times, attempts and accidental damages to surrounding structures (errors) in surgeons with different training levels.

METHODS

Final-year medical students (n = 9), residents (n = 14) and consultants (n = 10) from the Department of Otorhinolaryngology, Head and Neck Surgery at the University Hospital of Bern, Switzerland were enrolled in the present study. After randomization every participant had to complete a standard set of grasping and dissecting surgical tasks in a temporal bone model. After the first session the participants were crossed over to the other technique.

RESULTS

Time required for completion of the surgical tasks was similar for both techniques, but highly dependent on the training status. A significant increase in the number of damages to the ossicular chain was observed with the microscopic as compared to the endoscopic technique (p < 0.001). Moreover, students beginning with the endoscopic technique showed an overall significantly lower amount of time to complete the tasks (p = 0.04). From the subjective feedback a preference towards the endoscopic technique mainly in medical students was observed.

CONCLUSIONS

The endoscopic approach is useful and beneficial for teaching basic surgical skills, mainly by providing a reduction of damage to surrounding tissues with similar operating times for both techniques. Moreover, medical students performed significantly faster, when first taught in the endoscopic technique. Especially for young surgeons without previous training in ear surgery, the endoscope should be considered to improve surgical skills in the middle ear.

Robotic middle ear access for cochlear implantation: First in man

To demonstrate the feasibility of robotic middle ear access in a clinical setting, nine adult patients with severe-to-profound hearing loss indicated for cochlear implantation were included in this clinical trial. A keyhole access tunnel to the tympanic cavity and targeting the round window was planned based on preoperatively acquired computed tomography image data and robotically drilled to the level of the facial recess. Intraoperative imaging was performed to confirm sufficient distance of the drilling trajectory to relevant anatomy. Robotic drilling continued toward the round window. The cochlear access was manually created by the surgeon. Electrode arrays were inserted through the keyhole tunnel under microscopic supervision via a tympanomeatal flap. All patients were successfully implanted with a cochlear implant. In 9 of 9 patients the robotic drilling was planned and performed to the level of the facial recess. In 3 patients, the procedure was reverted to a conventional approach for safety reasons. No change in facial nerve function compared to baseline measurements was observed. Robotic keyhole access for cochlear implantation is feasible. Further improvements to workflow complexity, duration of surgery, and usability including safety assessments are required to enable wider adoption of the procedure.

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

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