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Purpose: In cochlear implantation, a scala vestibuli (SV) insertion of an electrode array is a rare occurrence and is reported to be linked to poor hearing outcomes. Using the same electrode array, the auditory performance of patients with a complete SV location was compared with that of patients having a complete scala tympani (ST) location 1 year after implantation., Methods: Thirty-three patients were included in this retrospective case-control study (SV, n = 12; ST, n = 21). The matching criteria were electrode array type, age at implantation, and duration of severe or profound deafness. The array location was analyzed using 3D reconstruction of postoperative CT scans. Postoperative audiological evaluation of the implanted ear was performed using pure-tone audiometry, speech recognition of monosyllabic words in quiet, and words and sentences in noise., Results: On the preoperative CT scan, six patients in the SV group presented with both round window (RW) and ST ossification, three with RW ossification alone, and three with no RW ossification. Auditory performance did not differ between SV and ST groups 1 year after cochlear implantation. Speech recognition of words was 49 ± 7.6% and 56 ± 5.0% in quiet and 75 ± 9.5% and 66 ± 6.0% in noise in SV and ST groups, respectively., Conclusion: ST insertion is the gold standard that allows the three cochlear scalae to preserve scalar cochlear integrity. However, 1 year after implantation, a planned or unexpected SV insertion is not detrimental to hearing outcomes, providing similar auditory performance in quiet and noise to ST insertion., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: The main aim of this study was to estimate the volume of the Scala Tympani (ST) of our pediatric cochlear implant (CI) recipients from the computed tomography (CT) images. Then, to study the association between ST volume and both demographic characteristics and cochlear parameters., Methods: A retrospective study on the CT scans of pediatric CI patients at a tertiary referral CI center. Congenital or acquired cochlear defects were excluded. Two reviewers, with the same level of experience, blindly measured the main cochlear parameters and studied its anatomy. Then, the interrater reliability was tested to measure any differences between the two readings. After that, the ST volume of the included patients was calculated and analyzed. Furthermore, the correlations between the main cochlear parameters and ST volume were studied to propose a formula for estimating the ST volume from the cochlear duct length (CDL)., Results: The mean predicted ST volume among our pediatric CI recipients was 38.51 ± 5.54 μl (range; 24.47-52.57 μl). The statistical analysis revealed that all cochlear parameters (A, B, H, and CDL values) could be significant predictors of the ST volume (p=<0.0001)., Conclusion: The main cochlear parameters along with the CDL are positively linked to the ST volume. There are considerable differences in cochlear size and scala tympani volume among our pediatric population. These findings confirm the importance of pre-operative planning for proper electrode array selection., Competing Interests: Declaration of competing interest The authors declare they have no conflict of interest. This study did not receive any funding., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In cochlear implant surgery, insertion of perimodiolar electrode arrays into the scala tympani can be complicated by trauma or even accidental translocation of the electrode array within the cochlea. In patients with partial hearing loss, cochlear trauma can not only negatively affect implant performance, but also reduce residual hearing function. These events have been related to suboptimal positioning of the cochlear implant electrode array with respect to critical cochlear walls of the scala tympani (modiolar wall, osseous spiral lamina and basilar membrane). Currently, the position of the electrode array in relation to these walls cannot be assessed during the insertion and the surgeon depends on tactile feedback, which is unreliable and often comes too late. This study presents an image-guided cochlear implant device with an integrated, fiber-optic imaging probe that provides real-time feedback using optical coherence tomography during insertion into the human cochlea. This novel device enables the surgeon to accurately detect and identify the cochlear walls ahead and to adjust the insertion trajectory, avoiding collision and trauma. The functionality of this prototype has been demonstrated in a series of insertion experiments, conducted by experienced cochlear implant surgeons on fresh-frozen human cadaveric cochleae., (© 2022. The Author(s).)

Introduction: Electrode array translocation is an unpredictable event with all types of arrays, even using a teleoperated robot in a clinical scenario. We aimed to compare the intracochlear trauma produced by the HiFocus™ Mid-Scala (MS) electrode array (Advanced Bionics, Valencia, CA, USA) using a teleoperated robot, with an automated robot connected to a navigation system to align the pre-curved tip of the electrode array with the coiling direction of the scala tympani (ST)., Methods: Fifteen freshly frozen temporal bones were implanted with the MS array using the RobOtol® (Collin, Bagneux, France). In the first group (n = 10), the robot was teleoperated to insert the electrode array into the basal turn of the ST under stereomicroscopic vision, and then the array was driven by a slow-speed hydraulic insertion technique with an estimated placement of the pre-curved electrode tip. In the second group (n = 5), 3 points were obtained from the preoperative cone-beam computed tomography: the 2 first defining the ST insertion axis of the basal turn and a third one at the center of the ST at 270°. They provided the information to the automated system (RobOtol® connected with a navigation system) to automatically align the electrode array with the ST insertion axis and to aim the pre-curved tip toward the subsequent coiling of the ST. After this, the electrode array was manually advanced. Finally, the cochleae were obtained and fixed in a crystal resin, and the position of each electrode was determined by a micro-grinding technique., Results: In all cases, the electrode array was fully inserted into the cochlea and the depth of insertion was similar using both techniques. With the teleoperated robotic technique, translocations of the array were observed in 7/10 insertions (70%), but neither trauma nor array translocation occurred with automated robotic insertion., Conclusion: We have successfully tested an automated insertion system (robot + navigation) that could accurately align a pre-curved electrode array to the axis of the basal turn of the ST and its subsequent coiling, which reduced intracochlear insertion trauma and translocation., (© 2021 S. Karger AG, Basel.)

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.

Objectives: (1) To assess variations of the human intracochlear anatomy and quantify factors which might be relevant for cochlear implantation (CI) regarding surgical technique and electrode design. (2) Search for correlations of these factors with clinically assessable measurements., Design: Human temporal bone study with micro computed tomography (μCT) data and analysis of intracochlear geometrical variations: μCT data of 15 fresh human temporal bones was generated, and the intracochlear lumina scala tympani (ST) and scala vestibuli were manually segmented using custom software specifically designed for accurate cochlear segmentation. The corresponding datasets were processed yielding 15 detailed, three-dimensional cochlear models which were investigated in terms of the scalae height, cross-sectional size, and rotation as well as the interrelation of these factors and correlations to others., Results: The greatest anatomical variability was observed within the round window region of the cochlea (basal 45°), especially regarding the cross-sectional size of the ST and its orientation relative to the scala vestibuli, which were found to be correlated (p < 0.001). The cross-sectional height of the ST changes substantially for both increasing cochlear angles and lateral wall distances. Even small cochleae were found to contain enough space for all commercially available CI arrays. Significant correlations of individual intracochlear parameters to clinically assessable ones were found despite the small sample size., Conclusion: While there is generally enough space within the ST for CI, strong intracochlear anatomical variations could be observed highlighting the relevance of both soft surgical technique as well as a highly flexible and self-adapting cochlear implant electrode array design. Cochlear dimensions (especially at the round window) could potentially be used to indicate surgically challenging anatomies., Competing Interests: D.S. is a MED-EL employee. The other authors have no conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: Assessment of the cochlear implant (CI) electrode array position using flat-detector computed tomography (FDCT) to test dependence of postoperative outcome on intracochlear electrode position., Methods: A total of 102 patients implanted with 107 CIs underwent FDCT. Electrode position was rated as 1) scala tympani, 2) scala vestibuli, 3) scalar dislocation and 4) no deconvolution. Two independent neuroradiologists rated all image data sets twice and the scalar position was verified by a third neuroradiologist. Presurgical and postsurgical speech audiometry by the Freiburg monosyllabic test was used to evaluate auditory outcome after 6 months of speech rehabilitation., Results: Electrode array position was assessed by FDCT in 107 CIs. Of the electrodes 60 were detected in the scala tympani, 21 in the scala vestibuli, 24 electrode arrays showed scalar dislocation and 2 electrodes were not placed in an intracochlear position. There was no significant difference in rehabilitation outcomes between scala tympani and scala vestibuli inserted patients. Rehabilitation was also possible in patients with dislocated electrodes., Conclusion: The use of FDCT is a reliable diagnostic method to determine the position of the electrode array. In our study cohort, the electrode position had no significant impact on postoperative outcome except for non-deconvoluted electrode arrays.

Objectives/hypothesis: Two types of electrode arrays for cochlear implants (CIs) are distinguished: lateral wall and perimodiolar. Scalar translocation of the array can lead to intracochlear trauma by penetrating from the scala tympani into the scala vestibuli or scala media, potentially negatively affecting hearing performance of CI users. This systematic review compares the lateral wall and perimodiolar arrays with respect to scalar translocation., Study Design: Systematic review., Methods: PubMed, Embase, and Cochrane databases were reviewed for studies published within the last 11 years. No other limitations were set. All studies with original data that evaluated the occurrence of scalar translocation or tip fold-over (TF) with postoperative computed tomography (CT) following primary cochlear implantation in bilateral sensorineuronal hearing loss patients were considered to be eligible. Data were extracted independently by two reviewers., Results: We included 33 studies, of which none were randomized controlled trials. Meta-analysis of five cohort studies comparing scalar translocation between lateral wall and perimodiolar arrays showed that lateral wall arrays have significantly lower translocation rates (7% vs. 43%; pooled odds ratio = 0.12). Translocation was negatively associated with speech perception scores (weighted mean 41% vs. 55%). Tip fold-over of the array was more frequent with perimodiolar arrays (X 2  = 6.8, P < .01)., Conclusions: Scalar translocation and tip fold-overs occurred more frequently with perimodiolar arrays than with lateral wall arrays. In addition, translocation of the array negatively affects hearing with the cochlear implant. Therefore, if one aims to minimize clinically relevant intracochlear trauma, lateral wall arrays would be the preferred option for cochlear implantation. Laryngoscope, 131:1358-1368, 2021., (© 2020 The Authors. The Laryngoscope published by Wiley Periodicals LLC on behalf of American Laryngological, Rhinological and Otological Society Inc, "The Triological Society" and American Laryngological Association (ALA).)

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., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Introduction: Many individuals have some residual hearing which should be preserved with cochlear implantation. To achieve this goal electrode arrays must fulfil certain design requirements. A new thin lateral wall electrode array (HiFocus SlimJ) was systematically designed on the basis of μCT studies of human cochlea anatomy. The primary objective of this study was to report on initial retrospective hearing preservation results from a cohort of subjects consecutively implanted with this electrode. Secondary objectives were to report on insertion depth and speech perception results for this new array., Methods: Twenty subjects with considerable residual hearing in low frequencies were consecutively implanted with the SlimJ electrode array. The electrode was inserted slowly through the round window and the insertion process was controlled by intracochlear electrocochleography measuring cochlear microphonics through the cochlear implant.Postoperative cone beam computed tomography was conducted and precise scalar location and angular insertion depth was estimated following image fusion with the preoperative images., Results: Low frequency hearing at 1 month postsurgery was preserved within 30 dB HL in 85% of subjects and within 15 dB HL in 50% of subjects. Mean angular insertion depth was 393 degrees (SD 62 degrees) with a range from 294 to 520 degrees. All electrode contacts in all subjects were identified within scala tympani., Conclusion: The SlimJ electrode array is easy to handle for atraumatic insertion through the round window, adjusted insertion depth controlled by electrocochleography measurements, and reliable fixation at the posterior tympanotomy. Hearing preservation rates are encouraging on the short term. We aim to further report on larger data sets and long-term outcomes.

Background: Angular insertion depth (AID) of the electrode array provides valuable information regarding intracochlear positioning, which can be used to predict outcomes and optimize performance. While computed tomography (CT) offers high-resolution imaging, there is a need to develop technology to accurately determine AID from intraoperative x-rays acquired at unknown angles., Methods: An algorithm was developed using a three-dimensional model of the scala tympani to estimate AID from an x-ray acquired at an unknown angle. The model is manipulated over the x-ray until the projection angle is inferred and the location of the round window and individual electrode contacts are identified. Validation of the algorithm involved 1) assessing accuracy with deviation from cochlear view by comparing AID determined with simulated x-rays to those determined with CT in a temporal bone model, and 2) assessing reproducibility in the clinical setting, by comparing intra- and inter-rater reliability with intraoperative x-ray in cochlear implant (CI) recipients, which were subsequently compared to AID determined with postoperative CT., Results: Estimates of AID from x-rays were generally within 10 degrees of CT regardless of deviation from cochlear view. Excluding two outliers with poor imaging quality, the intraclass correlation coefficients for intra- and inter-rater reliability were excellent (0.991 and 0.980, respectively)., Conclusion: With intraoperative x-rays of sufficient quality, the helical scala tympani model can be used to accurately and reliably determine AID without the need to specify a preferred image angle. The application can therefore be used in most CI recipients when a postoperative CT is not available.

In this study, a new idea of the optimal path generation method was proposed and a path planning strategy for robotic cochlear implant of perimodiolar electrode was designed. The centerline of scala tympani channel was taken as the optimal implant path of the perimodiolar electrode, which aimed to reduce the damage of the electrode to the cochlea during implantation. First, the three-dimensional cochlear model was reconstructed based on the micro-computed tomography images of cochlea, and it was re-segmented to obtain the cross sections of the scala tympani at different angles. Then, the image processing method was used to determine the central point of the scala tympani cross sections. The cubic B-spline interpolation method was used to fit these discrete central points to generate the optimal path. Finally, the coordinate information of the optimal path was combined with the stylet extraction state of perimodiolar electrode to conduct the path planning for robotic cochlear implant, and the result was sent to the robot for kinematic inverse solution to obtain the robot motion trajectory. The robotic cochlear implant experiment was performed with the model of scala tympani. The results showed that the maximum implant force based on path planning was 0.084 N, and the maximum implant force without path planning was 0.134 N. The optimal path generation and the path planning method effectively help to reduce the damage of the electrode to the cochlea.

Objective: Studies suggest lateral wall (LW) scala tympani (ST) height decreases apically, which may limit insertion depth. No studies have investigated the relationship of LW ST height with translocation rate or location., Study Design: Retrospective review., Setting: Cochlear implant program at tertiary referral center., Subjects and Methods: LW ST height was measured in preoperative images for patients with straight electrodes. Scalar location, angle of insertion depth (AID), and translocation depth were measured in postoperative images. Audiologic outcomes were tracked., Results: In total, 177 ears were identified with 39 translocations (22%). Median AID was 443° (interquartile range [IQR], 367°-550°). Audiologic outcomes (126 ears) showed a small, significant correlation between consonant-nucleus-consonant (CNC) word score and AID ( r = 0.20, P = .027), although correlation was insignificant if translocation occurred ( r = 0.11, P = .553). Translocation did not affect CNC score ( P = .335). AID was higher for translocated electrodes (503° vs 445°, P = .004). Median translocation depth was 381° (IQR, 222°-399°). Median depth at which a 0.5-mm electrode would not fit within 0.1 mm of LW was 585° (IQR, 405°-585°). Median depth at which a 0.5-mm electrode would displace the basilar membrane by ≥0.1 mm was 585° (IQR, 518°-765°); this was defined as predicted translocation depth (PTD). Translocation rate was 39% for insertions deeper than PTD and 14% for insertions shallower than PTD ( P = .008)., Conclusion: AID and CNC are directly correlated for straight electrodes when not translocated. Translocations generally occur around 380° and are more common with deeper insertions due to decreasing LW ST height. Risk of translocation increases significantly after 580°.

Introduction: A modern cochlear implant electrode array design must combine: improved surgical ease of use, structure preservation, particularly important for pediatric application, stable position within the cochlea over time, and a meaningful balance between hearing preservation against addressing sufficient cochlear tissue to support electrical-only hearing. The aim of this study was to investigate a new lateral wall electrode array design from Advanced Bionics on human temporal bones (TBs)., Methods: Ten fresh-frozen TBs were implanted with the SlimJ electrode array via the round window. The electrode array is 23 mm long, with a cross-section varying from 0.25 × 0.55 mm at the most apical contact to 0.6 × 0.8 mm at the proximal marker contact. To assess location of the electrode array, the TBs were postoperatively scanned using cone beam computed tomography, and histology was performed to assess intracochlear trauma (Grades 0-4)., Results: All electrode arrays were considered easy to insert. The average insertion depth was 432 degrees measured from the round window with a range from 411 to 450 degrees azimuth. Nine out of 10 electrode arrays were inserted fully (<0.5 mm out of the cochlea), one electrode array was left 1.5 mm out of the cochlea. No translocations were observed in all 10 cochleae, slight touching of the basilar membrane at the distal portion of the array was observed in 50% of the cases., Conclusion: The results from the new thin lateral wall electrode array from Advanced Bionics provided consistent scala tympani locations. No translocations were observed and almost all electrode arrays were fully inserted. These results are promising and the new electrode array will be further studied in clinical practice investigating hearing preservation capabilities and speech performance.

Hypothesis: Using patient-customized cochlear measurements obtained from preoperative computed tomography (CT) scans to guide insertion of cochlear implant (CI) electrode arrays will lead to more optimal intracochlear positioning., Background: Cochlear duct length is highly variable ranging from 25.26 to 35.46 mm, yet CI electrode arrays are treated as one size fits most. We sought to investigate the impact of patient-customized insertion plans on final location of electrode arrays., Methods: Twenty cadaveric temporal bone specimens were CT scanned and randomly divided into groups A and B. Group A specimens had an optimal customized insertion plan generated including entry site (e.g., round window versus extended round window), entry vector based on anatomical landmarks (e.g., hug posterior aspect of facial recess and angle 1 mm inferior to stapes), depth to begin advancing off stylet, and final insertion depth. Suboptimal plans were chosen for group B by selecting an approach that was normal yet predicted to result in poor final electrode location. One surgeon, blinded as to group, carried out the CI insertions following which the electrode array was fixed using superglue and the specimen CT scanned to allow assessment of final electrode location., Results: Average perimodiolar distances for groups A and B were 0.51 and 0.60 mm, respectively. For group A, full scala tympani insertion was achieved in all specimens while in group B, 4 of 10 specimens had scalar translocation., Conclusion: Patient customized cochlear implant insertion techniques achieved better positioning of electrode arrays in this study and have potential for improving electrode positioning in patients.

Purpose: To evaluate the insertion characteristics and trauma of a new slim lateral wall electrode (SlimJ) in human temporal bones (TB)., Methods: Pre- and postoperative assessment was performed using cone beam computed tomography (CBCT) and image fusion in 11 human TB. The position of the array in each cochlea was analyzed and described using a vertical scaling factor, calculated by dividing the distance of the scala tympani floor to the centre of the electrode by the duct height. Insertion trauma was scaled according to the presumed localization of the basilar membrane, which was modeled from histologic sections of 20 TBs. The insertion trauma was described by the adaptation of the Eshragi trauma grading., Results: A full electrode insertion, via the round window, was achieved in all TBs. Surgical handling was good, with a favorable compromise between high flexibility but sufficient stiffness to facilitate smooth insertions. The median angular insertion depth was 368° (range 330°-430°). Scala tympani placement was achieved in ten out of eleven TBs; in one TB a scala translocation was observed, occurring at approximately 180°., Conclusions: The SlimJ showed atraumatic insertion characteristics. The CBCT fusion technique provides an accurate and reliable assessment of the electrode position and allows for grading insertion trauma without histology. The SlimJ true potential for structure and hearing preservation needs to be further assessed in vivo.

Objectives: To investigate the clinical usefulness and practicality of co-registration of Cone Beam CT (CBCT) with preoperative Magnetic Resonance Imaging (MRI) for intracochlear localization of electrodes after cochlear implantation., Methods: Images of 20 adult patients who underwent CBCT after implantation were co-registered with preoperative MRI scans. Time taken for co-registration was recorded. The images were analysed by clinicians of varying levels of expertise to determine electrode position and ease of interpretation., Results: After a short learning curve, the average co-registration time was 10.78 minutes (StdDev 2.37). All clinicians found the co-registered images easier to interpret than CBCT alone. The mean concordance of CBCT vs. co-registered image analysis between consultant otologists was 60% (17-100%) and 86% (60-100%), respectively. The sensitivity and specificity for CBCT to identify Scala Vestibuli insertion or translocation was 100 and 75%, respectively. The negative predictive value was 100%., Discussion: CBCT should be performed following adult cochlear implantation for audit and quality control of surgical technique. If SV insertion or translocation is suspected, co-registration with preoperative MRI should be performed to enable easier analysis. There will be a learning curve for this process in terms of both the co-registration and the interpretation of images by clinicians.

Cochlear size and morphology vary greatly and may influence the course of a cochlear implant electrode array during insertion and its final intra-cochlear position. Detailed insight into these variations is valuable for characterizing each cochlea and offers the opportunity to study possible correlations with surgical or speech perception outcomes. This study presents an automatic tracing method to assess individual cochlear duct shapes from clinical CT images. On pre-operative CT scans of 479 inner ears the cochlear walls were discriminated by interpolating voxel intensities along radial and perpendicular lines within multiplanar reconstructions at 1 degree intervals from the round window. In all 479 cochleas, the outer wall could be traced automatically up to 720 degrees. The inner wall and floor of the scala tympani in 192 cochleas. The shape of the cochlear walls were modelled using a logarithmic spiral function including an offset value. The vertical trajectories of the scala tympani exhibited a non-monotonous spiral slope with specific regions at risk for CI-related insertion trauma, and three slope categories could be distinguished. This presented automatic tracing method allows the detailed description of cochlear morphology and can be used for both individual and large cohort evaluation of cochlear implant patients.

Objectives: 1) Examine angular insertion depths (AID) and scalar location of Med-El (GmbH Innsbruck, Austria) electrodes; and 2) determine the relationship between AID and audiologic outcomes controlling for scalar position., Study Design: Retrospective review., Methods: Postlingually deafened adults undergoing cochlear implantation with Flex 24, Flex 28, and Standard electrode arrays (Med-El) were identified. Patients with preoperative and postoperative computed tomography scans were included so that electrode location and AID could be determined. Outcome measures were 1) speech perception in the cochlear implant (CI)-only condition, and 2) short-term hearing preservation., Results: Forty-eight implants were included; all electrodes (48 of 48) were positioned entirely within the scala tympani. The median AID was 408° (interquartile [IQ] range 373°-449°) for Flex 24, 575° (IQ range 465°-584°) for Flex 28, and 584° (IQ range 368°-643°) for Standard electrodes (Med-El). The mean postoperative CNC score was 43.7% ± 21.9. A positive correlation was observed between greater AID and better CNC performance (r = 0.48, P < 0.001). Excluding patients with postoperative residual hearing, a strong correlation between AID and CNC persisted (r = 0.57, P < 0.001). In patients with preoperative residual hearing, mean low-frequency pure-tone average (PTA) shift was 27 dB ± 14. A correlation between AID and low-frequency PTA shift at activation was noted (r = 0.41, P = 0.04)., Conclusion: Favorable rates of scala tympani insertion (100%) were observed. In the CI-only condition, a direct correlation between greater AID and CNC score was noted regardless of postoperative hearing status. Deeper insertions were, however, associated with worse short-term hearing preservation. When patients without postoperative residual hearing were analyzed independently, the relationship between greater insertion depth and better performance was strengthened., Level of Evidence: 4. Laryngoscope, 127:2352-2357, 2017., (© 2016 The American Laryngological, Rhinological and Otological Society, Inc.)

Introduction: Cochlear implantation (CI) has developed from its origins in the 1980s. Initially, CI was for profound bilateral hearing impairment. However, candidacy for CI have become more widespread in recent years with unilateral implantation and an emphasis on hearing preservation. Evidence supports full electrode insertion in an atraumatic fashion into the scala tympani (ST) provides optimal hearing outcomes. The main aim of this systematic review was to elucidate the degree of trauma associated with CI insertion., Methods: A systematic literature search was undertaken using PubMed Medline. A grading system described by Eshraghi was used to classify cochlear trauma. Both radiological and histological studies were included., Results: Twenty one papers were identified which were relevant to our search. In total, 653 implants were inserted and 115 (17.6%) showed evidence of trauma. The cochleas with trauma had basilar membrane elevation in 5.2%, ruptured in 5.2%, the electrode passed from the ST to the SV in 84.4% and there was grade 4 trauma in 5.2%. The studies used a variety of histological and radiological methods to assess for evidence of trauma in both cadaveric temporal bones and live recipients., Conclusions: Minimizing cochlear trauma during implant insertion is important to preserve residual hearing and optimize audiological performance. An overall 17.6% trauma rate suggests that CI insertion could be improved with more accurate and consistent electrode insertion such as in the form of robotic guidance. The correlation of cochlea trauma with post-operative hearing has yet to be determined.

Objectives: To assess the feasibility of using cone-beam computed tomography (CBCT) in young children with cochlear implants (CIs) and study the effect of intracochlear position on electrophysiological and behavioral measurements., Methods: A total of 40 children with either unilateral or bilateral cochlear implants were prospectively included in the study. Electrode placement and insertion angles were studied in 55 Cochlear ® implants (16 straight arrays and 39 perimodiolar arrays), using either CBCT or X-ray imaging. CBCT or X-ray imaging were scheduled when the children were leaving the recovery room. We recorded intraoperative and postoperative neural response telemetry threshold (T-NRT) values, intraoperative and postoperative electrode impedance values, as well as behavioral T (threshold) and C (comfort) levels on electrodes 1, 5, 10, 15 and 20., Results: CBCT imaging was feasible without any sedation in 24 children (60%). Accidental scala vestibuli insertion was observed in 3 out of 24 implants as assessed by CBCT. The mean insertion angle was 339.7°±35.8°. The use of a perimodiolar array led to higher angles of insertion, lower postoperative T-NRT, as well as decreased behavioral T and C levels. We found no significant effect of either electrode array position or angle of insertion on electrophysiological data., Conclusion: CBCT appears to be a reliable tool for anatomical assessment of young children with CIs. Intracochlear position had no significant effect on the electrically evoked compound action potential (ECAP) threshold. Our CBCT protocol must be improved to increase the rate of successful investigations., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

The position of the cochlear-implant electrode is important to audiological outcomes after cochlear implantation. The common technique to evaluate the intracochlear electrode's position involves the use of ionized radiation in MSCT, DVT, or flat-panel tomography (FPT). Recent advances in knowledge regarding the handling of MRI artifacts in cochlear implantees indicate that estimating the intracochlear electrode's position with an MRI could be possible. This study's aim was to evaluate the ipsilaterally position of electrodes using MRI at 1.5 T. In a retrospective study of 10 implantees with postoperative need for MRI scanning, we evaluated the intrascalar electrode's position using a T2-weighted sequence at 1.5 T. We compared the resulting estimate of the intracochlear position with the estimates from the postoperative FPT scan and the intraoperative NRT ratio. For each ear, the MRI-estimated scalar position corresponded with the estimated positions from the FPT and NRT ratio. For eight ears, a scala tympani's position was observed in the MRI. In one case, an electrode scalar translocation was found. In one case, the scala vestibuli's position was observed. Thus, MRI-based estimation of the scalar position of a cochlear-implant electrode is possible. Limitations to this method include implant-specific magnet and fixation configurations, which can cause complications.

Objective: The aim of this work was to describe the dimensions of the crista fenestra and determine its presence by means of high-resolution computed tomography (CT) for the purpose of cochlear implantation via the round window approach., Methods: A series of 10 adult human temporal bones underwent high-resolution CT scanning and were further dissected for microscopic study of the round window niche., Results: In all of the specimens, the round window membrane was fully visualized after the complete removal of bony overhangs. The crista fenestra was identified as a sharp bony crest located in the anterior and inferior borders of the niche; its area ranged from 0.28 to 0.80 mm2 (mean 0.51 ± 0.18). The proportion of the area occupied by the crista fenestra in the whole circumference of the round window ranged from 23 to 50% (mean 36%). We found a moderate positive correlation between the area of the niche and the dimensions of the crista fenestra (Spearman rho: 0.491). In every case, high-resolution CT scanning was unable to determine the presence of the crista fenestra., Conclusion: The crista fenestra occupies a variable but expressive area within the bony round window niche. Narrower round window niches tended to house smaller crests. The presence of the crista fenestra is an important obstacle to adequate access to the scala tympani. Nevertheless, a high-resolution CT scan provides no additional preoperative information with regard to its presence for the purpose of surgical access to the scala tympani via the round window niche., (© 2017 S. Karger AG, Basel.)

The aim of this study was to evaluate the insertion results and placement of the new Advanced Bionics HiFocus Mid-Scala (HFms) electrode array, inserted through the round window membrane, in eight fresh human temporal bones using cone beam computed tomography (CBCT). Pre- and post-insertion CBCT scans were registered to create a 3D reconstruction of the cochlea with the array inserted. With an image fusion technique both the bony edges of the cochlea and the electrode array in situ could accurately be determined, thus enabling to identify the exact position of the electrode array within the scala tympani. Vertical and horizontal scalar location was measured at four points along the cochlea base at an angular insertion depth of 90°, 180° and 270° and at electrode 16, the most basal electrode. Smooth insertion through the round window membrane was possible in all temporal bones. The imaging results showed that there were no dislocations from the scala tympani into the scala vestibule. The HFms electrode was positioned in the middle of the scala along the whole electrode array in three out of the eight bones and in 62 % of the individual locations measured along the base of the cochlea. In only one cochlea a close proximity of the electrode with the basilar membrane was observed, indicating possible contact with the basilar membrane. The results and assessments presented in this study appear to be highly accurate. Although a further validation including histopathology is needed, the image fusion technique described in this study represents currently the most accurate method for intracochlear electrode assessment obtainable with CBCT.

The mammalian cochlea has historically resisted attempts at high-resolution, non-invasive imaging due to its small size, complex three-dimensional structure, and embedded location within the temporal bone. As a result, little is known about the relationship between an individual's cochlear pathology and hearing function, and otologists must rely on physiological testing and imaging methods that offer limited resolution to obtain information about the inner ear prior to performing surgery. Micro-optical coherence tomography (μOCT) is a non-invasive, low-coherence interferometric imaging technique capable of resolving cellular-level anatomic structures. To determine whether μOCT is capable of resolving mammalian intracochlear anatomy, fixed guinea pig inner ears were imaged as whole temporal bones with cochlea in situ. Anatomical structures such as the tunnel of Corti, space of Nuel, modiolus, scalae, and cell groupings were visualized, in addition to individual cell types such as neuronal fibers, hair cells, and supporting cells. Visualization of these structures, via volumetrically-reconstructed image stacks and endoscopic perspective videos, represents an improvement over previous efforts using conventional OCT. These are the first μOCT images of mammalian cochlear anatomy, and they demonstrate μOCT's potential utility as an imaging tool in otology research.

Objectives: It has long been known that cochlear implantation may cause loss of residual hearing and vestibular function. Different insertion depths may cause varying degrees of intracochlear trauma in the apical region of the cochlea. The present study investigated the correlation between the insertion depth and postoperative loss of residual hearing and vestibular function., Design: Thirty-nine adults underwent unilateral cochlear implantation. One group received a Med-El +Flex electrode array (24 mm; n = 4), 1 group received a Med-El +Flex electrode array (28 mm; n = 18), and 1 group received a Med-El +Flex electrode array (31.5 mm; n = 17). Residual hearing, cervical vestibular-evoked myogenic potentials, videonystagmography, and subjective visual vertical/horizontal were explored before and after surgery. The electrode insertion depth and scalar position were examined with high-resolution rotational tomography after implantation in 29 subjects., Results: There was no observed relationship between the angular insertion depth (405° to 708°) and loss of low-frequency pure-tone average. Frequency-specific analysis revealed a weak relationship between the angular insertion depth and loss of hearing at 250 Hz (R= 0.20; p = 0.02). There was no statistically significant difference in the residual hearing and vestibular function between the +Flex and the +Flex electrode array. Eight percent of the cases had vertigo after surgery. The electrode arrays were positioned inside the scala tympani and not scala vestibuli in all subjects. In 18% of the cases, the +Flex electrode array was not fully inserted., Conclusions: The final outcome in residual hearing correlates very weakly with the angular insertion depth for depths above 405°. Postoperative loss of vestibular function did not correlate with the angular insertion depth or age at implantation. The surgical protocol used in this study seems to minimize the risk of postoperative vertigo symptoms.

Objective: The position of cochlear implant (CI) electrodes in the cochlea is fundamental for the interaction between the implant and the neurons of the spiral ganglion. The scalar position of the electrode in the cochlea is assumed to be an important parameter for the clinical outcome. In our study, the intraoperative electrophysiologic characteristics in dependence of the position of CI electrodes in the scala tympani or in the scala vestibuli after scalar change should be determined., Materials and Methods: The intraoperative impedances and neural response telemetry (NRT) data of 23 patients implanted with a Nucleus Advance Contour (Cochlear Pty, Sydney, Australia) electrode were recorded. One CI surgeon and two radiologists evaluated the electrode array's position independently radiologically by flat-panel tomography. Results from 17 patients with the electrode positioned in the scala tympani and six patients with the electrode changing intraoperatively from the tympanic into the vestibular scala were retrospectively analyzed., Results: We found a statistically significant difference with an NRT threshold-based ratio for the groups. An estimation of the (radiologically confirmed) scalar position based on the NRT ratio was possible retrospectively., Conclusion: The evaluation of specific intraoperative electrophysiologic data allowed separating between a regular and an irregular (i.e., scalar changing) position of CI electrodes. This noninvasive methodology can support the postoperative radiologic evaluation of the CI electrode array position.

Hypothesis: To evaluate the feasibility and the results of insertion of two types of electrode arrays in a robotically assisted surgical approach., Background: Recent publications demonstrated that robot-assisted surgery allows the implantation of free-fitting electrode arrays through a cochleostomy drilled via a narrow bony tunnel (DCA). We investigated if electrode arrays from different manufacturers could be used with this approach., Methods: Cone-beam CT imaging was performed on five-cadaveric heads after placement of fiducial screws. Relevant anatomical structures were segmented and the DCA trajectory, including the position of the cochleostomy, was defined to target the center of the scala tympani while reducing the risk of lesions to the facial nerve. Med-El Flex 28 and Cochlear CI422 electrodes were implanted on both sides, and their position was verified by cone-beam CT. Finally, temporal bones were dissected to assess the occurrence of damage to anatomical structures during DCA drilling., Results: The cochleostomy site was directed in the scala tympani in 9 of 10 cases. The insertion of electrode arrays was successful in 19 of 20 attempts. No facial nerve damage was observed. The average difference between the planned and the postoperative trajectory was 0.17 ± 0.19 mm at the level of the facial nerve. The average depth of insertion was 305.5 ± 55.2 and 243 ± 32.1 degrees with Med-El and Cochlear arrays, respectively., Conclusions: Robot-assisted surgery is a reliable tool to allow cochlear implantation through a cochleostomy. Technical solutions must be developed to improve the electrode array insertion using this approach.

Objective: To compare the incidence of dislocation of precurved versus straight flexible cochlear implant electrode arrays using cone-beam computed tomography (CBCT) image analyses., Study Design: Consecutive nonrandomized case-comparison study., Settings: Tertiary referral center., Patients: Analyses of patients' CBCT images after cochlear implant surgery., Intervention(s): Precurved and straight flexible electrode arrays from two different manufacturers were implanted. A round window insertion was performed in most cases. Two cases necessitated a cochleostomy. The patients' CBCT images were reconstructed in the coronal oblique, sagittal oblique, and axial oblique section., Main Outcome Measures: The insertion depth angle and the incidence of dislocation from the scala tympani to the scala vestibuli were determined., Results: The CBCT images and the incidence of dislocation were analyzed in 54 patients (61 electrode arrays). Thirty-one patients were implanted with a precurved perimodiolar electrode array and 30 patients with a straight flexible electrode array. A total of nine (15%) scalar dislocations were observed in both groups. Eight (26%) scalar dislocations were observed in the precurved array group and one (3%) in the straight array group. Dislocation occurred at an insertion depth angle between 170 and 190 degrees in the precurved array group and at approximately 370 degrees in the straight array group., Conclusion: With precurved arrays, dislocation usually occurs in the ascending part of the basal turn of the cochlea. With straight flexible electrode arrays, the incidence of dislocation was lower, and it seems that straight flexible arrays have a higher chance of a confined position within the scala tympani than perimodiolar precurved arrays.

Background and Purpose: Localization of the electrode after cochlear implantation seems to have an impact on auditory outcome, and conebeam CT has emerged as a reliable method for visualizing the electrode array position within the cochlea. The aim of this retrospective study was to evaluate the frequency and clinical impact of scalar dislocation of various electrodes and surgical approaches and to evaluate its influence on auditory outcome., Materials and Methods: This retrospective single-center study analyzed a consecutive series of 63 cochlear implantations with various straight electrodes. The placement of the electrode array was evaluated by using multiplanar reconstructed conebeam CT images. For the auditory outcome, we compared the aided hearing thresholds and the charge units of maximum comfortable loudness level at weeks 6, 12, and 24 after implantation., Results: In 7.9% of the cases, the electrode array showed scalar dislocation. In all cases, the electrode array penetrated the basal membrane within 45° of the electrode insertion. All 3 cases of cochleostomy were dislocated in the first 45° segment. No hearing differences were noted, but the charge units of maximum comfortable loudness level seemed to increase with time in patients with dislocations., Conclusions: The intracochlear dislocation rate of various straight electrodes detected by conebeam CT images is relatively low. Scalar dislocation may not negatively influence the hearing threshold but may require an increase of the necessary stimulus charge and should be reported by the radiologist., (© 2015 by American Journal of Neuroradiology.)

Animal models are the only means of assessing the effects of cochlear implantation (CI) at a cellular and molecular level. The range of naturally occurring and genetically-modified mouse strains which mimic human deafness provide excellent opportunities for auditory research. To date, there are very few studies of CI in mice. The main aims of this study were to develop a reproducible and viable technique to enable long term CI in the mouse and to assess the response of the mouse cochlea to implantation as a means of evaluating the success of the procedure. Electrode array implantation via the round window was performed in C57Bl/6 mice aged 3 and 6 months. The contralateral cochlea acted as a control. Auditory brainstem responses (ABR) were recorded prior to and following CI. Analysis showed greater threshold shifts in the implanted ear compared to the control ear post-implantation, but substantial preservation of hearing. There were no cases in which implantation caused a profound hearing loss across all frequencies. Cone beam computerised tomography and light microscopy confirmed correct placement of the electrode array within the scala tympani. Cochleae were prepared for histological examination. Initial analysis revealed encapsulation of the implant in tissue with morphological characteristics suggestive of fibrosis. Our results show that mouse CI via the round window offers a model for exploring tissue responses to implantation., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Postoperative imaging plays a growing role in clinical studies concerning prognostic factors in cochlear implantation. Indeed, intracochlear position of the cochlear implant has recently been identified as a contributor in functional outcomes and radiological tools must be accurate enough to determine the final placement of the electrode array. The aim of our study was to validate cone beam computed tomography as a reliable technique for scalar localization of the electrode array. We performed therefore a temporal bone study on ten specimens that were implanted with a perimodiolar implant prototype. Cone beam reconstructions were performed and images were analyzed by two physicians both experienced in cochlear implant imaging, who determined the scalar localization of the implant. Temporal bones then underwent histological control to document this scalar localization and hypothetical intracochlear lesions. In four cases, a dislocation from scala tympani to scala vestibuli was suspected on cone beam reconstructions of the ascending part of the basal turn. In three of these four specimens, dislocation in pars ascendens was confirmed histologically. In the remaining temporal bone, histological analysis revealed an elevation with rupture of the basilar membrane. Histological assessment revealed spiral ligament tearing in another bone. We conclude that cone beam is a reliable tool to assess scalar localization of the selectrode array and may be used in future clinical studies.

Objective: To evaluate the effect of the intracochlear electrode position on the residual hearing and VNG- and cVEMP responses., Design: Prospective pilot study., Study Sample: Thirteen adult patients who underwent unilateral cochlear implant surgery were examined with high-resolution rotational tomography after cochlear implantation. All subjects were also tested with VNG, and 12 of the subjects were tested with cVEMP and audiometry before and after surgery., Results: We found that although the electrode was originally planned to be positioned inside the scala tympani, only 8 of 13 had full insertion into the scala tympani. Loss of cVEMP response occurred to the same extent in the group with full scala tympani positioning and the group with scala vestibuli involvement. There was a non-significant difference in the loss of caloric response and residual hearing between the two groups. Interscalar dislocation of the electrode inside the cochlea was observed in two patients. A higher loss of residual hearing could be seen in the group with electrode dislocation between the scalae., Conclusions: Our findings indicate that intracochlear electrode dislocation is a possible cause to loss of residual hearing during cochlear implantation but cannot be the sole cause of postoperative vestibular loss.

Conclusions: The round window membrane (RWM)-intentioned approach is superior to the traditional bony cochleostomy (BC) approach in obtaining electrode placement within the scala tympani (ST)., Objective: Cochlear implant outcome is influenced by several factors, including optimal placement and retention of the electrode array within the ST. The present study aimed to assess whether the RWM route is superior to a traditional BC for placement and retention of the electrode array in the ST., Methods: This was a prospective consecutive non-randomized comparison study. All patients were implanted with the Advanced Bionics 1J electrode array. The RWM approach (n = 32) was compared with a traditional BC group (n = 33). The outcome measure was the electrode position as judged within the scalar chambers at four points along the basal turn using postoperative computed tomography (CT)., Results: When the mean position scores were compared, the RWM-intentioned group had significantly more electrodes directed towards the ST compartment than the BC group (p < 0.001). The RWM electrodes achieved 94% ST retention compared with 64% for the BC group (p < 0.05). All electrodes stayed in the ST in the RWM group, whereas in the BC group 9% crossed from the ST to the scala vestibuli.

The marmoset (Callithrix jacchus) is a valuable non-human primate model for studying behavioral and neural mechanisms related to vocal communication. It is also well suited for investigating neural mechanisms related to cochlear implants. The purpose of this study was to characterize marmoset temporal bone anatomy and investigate the feasibility of implanting a multi-channel intracochlear electrode into the marmoset scala tympani. Micro computed tomography (microCT) was used to create high-resolution images of marmoset temporal bones. Cochlear fluid spaces, middle ear ossicles, semicircular canals and the surrounding temporal bone were reconstructed in three-dimensional space. Our results show that the marmoset cochlea is ∼16.5 mm in length and has ∼2.8 turns. The cross-sectional area of the scala tympani is greatest (∼0.8 mm(2)) at ∼1.75 mm from the base of the scala, reduces to ∼0.4 mm(2) at 5 mm from the base, and decreases at a constant rate for the remaining length. Interestingly, this length-area profile, when scaled 2.5 times, is similar to the scala tympani of the human cochlea. Given these dimensions, a compatible multi-channel implant electrode was identified. In a cadaveric specimen, this electrode was inserted ¾ turn into the scala tympani through a cochleostomy at ∼1 mm apical to the round window. The depth of the most apical electrode band was ∼8 mm. Our study provides detailed structural anatomy data for the middle and inner ear of the marmoset, and suggests the potential of the marmoset as a new non-human primate model for cochlear implant research., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Objectives: This study aimed to evaluate the possibility of predicting radiologically the scalar localization of a 31.5-mm-long, free-fitting electrode carrier for cochlear implantation, using conventional planar computed tomography., Study Design: A cross-sectional human temporal bone study was conducted., Setting: Twenty human temporal bones were acquired postmortem and implanted with 31.5-mm-long electrode carriers. Ten of these were implanted into the scala tympani using the round window approach, whereas the other 10 electrodes were inserted into the scala vestibuli by cochleostomy. Computed tomography was then performed, and 2 experienced blinded radiologists evaluated the intracochlear position of the array., Main Outcome Measure: The estimated position of the electrode carrier was described using a 5-point scale. After sectioning and histologic investigation, the results of the radiologic and histologic investigations were compared., Results: In 17 of 20 cases, it was possible to estimate the correct position of the electrode carrier within the basal turn of the cochlea by means of computed tomography. As the insertion angles widened beyond 360 degrees, it became increasing difficult for the radiologists to correctly determine the position of the electrode carrier., Conclusion: The comparison of our temporal bone experiment results with the computed tomography results revealed the difficulty of assessing the correct position of intracochlear electrodes. Scalar localization of deeply inserted electrode carriers cannot be precisely determined by means of computed tomography.

Hypothesis: A midmodiolar reconstruction with multislice computed tomography could potentially be used clinically to determine the cochlear implant electrode array position if the technique was validated with a cadaveric temporal bone study., Background: Several radiologic studies using sophisticated techniques have been described. This study was designed to validate a standard multislice computed tomography scan technique to determine the electrode array position., Methods: This ex vivo study was conducted on 18 cadaveric temporal bones without malformation. Cochlear electrode dummies were implanted by a single experimented surgeon with the Advance Off-Stylet technique. After randomization, the placement was processed through an anteroinferior or superior cochleostomy for respective scala tympani or vestibuli positioning with direct location of the basilar membrane. Cadaveric temporal bones were then scanned (Philips Brilliance 40 computed tomographic scan) and reconstructed into the midmodiolar computed tomography scan plane (± 45 degrees, z-axis in the cochlear coordinate system). Two independent neuroradiologists, who were unaware of the implanted scala, evaluated the electrode array position on a computed tomographic scan through the midmodiolar reconstruction. In the end, the microanatomic study was the criterion standard to determine the exact scala localization of the electrode array., Results: Nine electrodes were inserted into the scala tympani, and 9 were inserted into the scala vestibuli. According to our anatomic criterion standard, the midmodiolar reconstruction sensitivity and the specificity for the scala tympani position were 0.875 (range, 0.722-1.0) and 1.0, respectively; the sensitivity and specificity for dislocation and the scala vestibuli position were both 1.0. The radioanatomic concordance was 0.94 (range, 0.89-0.98) for determining the electrode array position into scalae with midmodiolar reconstruction., Conclusion: Our cadaveric study validates midmodiolar reconstruction as a valuable tool to routinely determine the precise position of the cochlear implant electrode array. This study opens the field for further clinical studies.

Cochlear implant surgery is a procedure performed to treat profound hearing loss. Clinical results suggest that implanting the electrode in the scala tympani, one of the two principal cavities inside the cochlea, may result in better hearing restoration. Segmentation of intracochlear cavities could thus aid the surgeon to choose the point of entry and angle of approach that maximize the likelihood of successful implant insertion, which may lead to more substantial hearing restoration. However, because the membrane that separates the intracochlear cavities is too thin to be seen in conventional in vivo imaging, traditional segmentation techniques are inadequate. In this paper, we circumvent this problem by creating an active shape model with micro CT (μCT) scans of the cochlea acquired ex vivo. We then use this model to segment conventional CT scans. The model is fitted to the partial information available in the conventional scans and used to estimate the position of structures not visible in these images. Quantitative evaluation of our method, made possible by the set of μCTs, results in Dice similarity coefficients averaging 0.75. Mean and maximum surface errors average 0.21 and 0.80  mm.

Background: Detailed studies of cochlear morphology can guide our approach to cochleostomy and electrode insertion to optimize neuronal and hair cell preservation and ultimate electrode location., Methods: Normal developed cochleae from 124 cochlear implant candidates were studied. We performed morphometric analysis of the right cochleae in all subjects based on computed tomographic data. The length and width of the cochlear base, the angle between the first and second turn of the cochlea, and the cochlear orientation within the cranial base were measured and compared across age groups. In cochlear implant candidates with underdeveloped cochleae (n = 7), we performed similar measurements and assessed the modiolar inlet area on 3D volume rendered images., Results: The birth to 1 year and 1- to 2-year age groups showed insignificant differences in the lengths and widths of the cochlear base, although variability was considerable, and a significantly wider angle (from the midsagittal line) than that of the older age groupings (p < 0.05). For underdeveloped cochleae, the length and width of the cochlear base were significantly smaller and angled between the first and second turn differed from the normal developed group. The modiolar inlet also was significantly smaller in the underdeveloped cochleae compared with normal cochleae., Conclusion: We observed that perspective 3D-volume rendering of the cochlea enables the determination of key features of cochlear morphology and orientation that may escape detection with routine computed tomographic scanning. Infants and young toddler candidates demonstrate greater variability in the dimensions of the cochlear base and in the orientation of the cochlea within the cranium. As evolving surgical techniques and device design enhance the ability of the surgeon to avoid cochlear damage and optimize electrode location, refined morphometric information may assist the surgeon in tailoring strategies of scala tympani implantation.

Hypothesis: 1) To assess the insertion characteristics of a disposable intracochlear catheter; and 2) to assess radiologically cochlear trauma induced by delivery catheter and electrode arrays., Background: A catheter was designed to enter the scala tympani up to 15 mm and to acutely deliver pharmacological agents during cochlear implantation., Methods: A cadaveric study was conducted in accordance to national regulation. Thirteen fresh temporal bones were evaluated radiologically. The intracochlear catheter used in this experiment has the same outer dimensions and profile as a standard MED-EL cochlear implant electrode array. We performed sequentially the introduction of the catheter, the injection of an iodine solution into the scala tympani via the catheter, the removal of the catheter, and finally an electrode array insertion. Ten to 15 μl of an iodine solution was injected into the scala tympani at depth of 15 mm. Four CT scans were sequentially performed after each step., Results: The disposable intracochlear catheter could easily be inserted in all specimens. An insertion at depth of 15 mm was easily achieved every time. CT scans demonstrated that the iodine solution injected stayed in the scala tympani in all specimens. This was interpreted as indirect evidence of the integrity of the basilar membrane., Conclusion: Drug delivery during cochlear implantation using a flexible disposable intracochlear catheter has been demonstrated to be feasible and without radiological evidence of basilar membrane trauma to a distance of up to 15 mm, as demonstrated in 13 temporal bones.

Conclusion: The modified round window insertion enables reproducible insertion into the scala tympani as demonstrated by comparing the 64-CT scanning data and the surgeon's reports., Objective: To estimate the postoperative cochlear implant electrode position using a modified round window approach., Patients and Methods: In a prospective study, 82 patients were operated via a modified round window approach to insert primarily into the scala tympani. Surgery had been performed from 2005 to 2008, implanting a Nucleus Freedom RECA device (Cochlear Corp.) (n = 43) or 90 k Helix device (Advanced Bionics Corp.) (n = 39). The array localization within the cochlea was determined by axial scanning overview, digital reconstruction of a 64-slice CT and by evaluation of the surgeon's report., Results: In 78 (95.1%) patients, the array could be located in the scala tympani. In four cases, the position of the electrode was changed intracochlearly from the scala tympani to the scala vestibuli. In three additional cases, the scala vestibuli was inserted intentionally because the tympanic scale was found to be obstructed intraoperatively due to ossification. There were no significant differences between the intraoperative positioning and postoperative localization of the electrode arrays of the two manufacturers.

X-ray microtomography (micro-CT) is a new technique allowing for visualization of the internal structure of opaque specimens with a quasi-histological quality. Among multiple potential applications, the use of this technique in otology is very promising. Micro-CT appears to be ideally suited for in vitro visualization of the inner ear tissues as well as for evaluation of the electrode damage and/or surgical insertion trauma during implantation of the cochlear implant electrodes. This technique can greatly aid in design and development of new cochlear implant electrodes and is applicable for temporal bone studies. The main advantage of micro-CT is the practically artefact-free preparation of the samples and the possibility of evaluation of the interesting parameters along the whole insertion depth of the electrode. This paper presents the results of the first application of micro-CT for visualization of the inner ear structures in human temporal bones and for evaluation of the surgical positioning of the cochlear implant electrodes relative to the intracochlear soft tissues.

Objective: To investigate the intracochlear electrode position in using rotational tomography in adult cochlear implant patients., Study Design: Retrospective., Setting: Tertiary referral center., Patients: Eighteen adult patients being implanted either with a Nucleus straight electrode array or a Contour electrode with a total of 22 implanted ears. Preoperative computed tomography had been without evidence for obliteration, ossification, or malformation of the cochlea., Intervention: Rotational tomography., Main Outcome Measures: The intracochlear electrode position was evaluated with regard to scala tympani, scala vestibuli, and a dislocation from one scala to the other. The intraoperative procedure was compared with the electrode position by analyzing the operating reports., Results: Preliminary results indicate, respectively, that there is a higher incidence of intracochlear trauma in using the Contour electrode array than expected with a more frequent dislocation of electrode arrays from scala tympani to scala vestibuli and that there is a higher rate of scala vestibuli insertions., Conclusions: The impact of these findings may influence further developments of electrode arrays as well as surgical techniques for implantation.

Background and Purpose: Cochlear implantation requires introduction of a stimulating electrode array into the scala vestibuli or scala tympani. Although these structures can be separately identified on many high-resolution scans, it is often difficult to ascertain whether these channels are patent throughout their length. The aim of this study was to determine whether an optimized combination of an imaging protocol and a visualization technique allows routine 3D rendering of the scala vestibuli and scala tympani., Methods: A submillimeter T2 fast spin-echo imaging sequence was designed to optimize the performance of 3D visualization methods. The spatial resolution was determined experimentally using primary images and 3D surface and volume renderings from eight healthy subjects. These data were used to develop the imaging sequence and to compare the quality and signal-to-noise dependency of four data visualization algorithms: maximum intensity projection, ray casting with transparent voxels, ray casting with opaque voxels, and isosurface rendering. The ability of these methods to produce 3D renderings of the scala tympani and scala vestibuli was also examined. The imaging technique was used in five patients with sensorineural deafness., Results: Visualization techniques produced optimal results in combination with an isotropic volume imaging sequence. Clinicians preferred the isosurface-rendered images to other 3D visualizations. Both isosurface and ray casting displayed the scala vestibuli and scala tympani throughout their length. Abnormalities were shown in three patients, and in one of these, a focal occlusion of the scala tympani was confirmed at surgery., Conclusion: Three-dimensional images of the scala vestibuli and scala tympani can be routinely produced. The combination of an MR sequence optimized for use with isosurface rendering or ray-casting algorithms can produce 3D images with greater spatial resolution and anatomic detail than has been possible previously.

Multichannel cochlear implants are a proven method for the auditory rehabilitation of individuals who have severe-to-profound sensorineural hearing loss. These devices typically require insertion into the scala tympani of the cochlea to provide auditory stimulations. A patent scala provides the best chance for an adequate insertion of the electrode array. Preoperative high-resolution computed tomography imaging has traditionally been used to determine the patency of the scala tympani. Its ability to accurately predict the patency of the cochlea has been questioned in several retrospective studies. A prospective study was undertaken in 28 consecutive individuals undergoing cochlear implant surgery to compare the findings on high-resolution computed tomography with the surgical findings in an attempt to determine high-resolution computed tomography's accuracy. Cochlear obstruction caused by ossification was accurately predicted in six of six individuals but overestimated in the round window region in three individuals. High-resolution computed tomography accurately predicted patent cochleas in 19 individuals. No false-negative results were encountered. In this study sensitivity of high-resolution computed tomography was 100%, and specificity was 86%. High-resolution computed tomography appears to be more helpful than previously reported for determining cochlear patency.