Paul Van de Heyning

Cochlear implantation in older adults: current routine and needs – a multi-centre scoping survey

HeyningFrontiers in Surgery

Towards a consensus on hearing and structure preservation in cochlear implantation surgery: results of the HEARRING international group survey

Background: To evaluate current clinical practices, attitudes, and considerations regarding hearing and structure preservation (HSP) in cochlear implant surgery among international experts. Methods: A cross-sectional online survey comprising 42 structured items was distributed to 75 HEARRING members, including surgeons, audiologists, and scientists. The questionnaire covered HSP indications and candidate evaluation, electrode array selection, surgical techniques, fitting strategies, and training. Results: Thirty-one experts from 16 countries completed the survey. Most respondents (87.1%) supported HSP surgery in all patients with normal cochlear anatomy, regardless of the severity of hearing loss, primarily to preserve cochlear structures and optimize long-term outcomes. Strong consensus emerged regarding atraumatic principles, including slow electrode array insertion, flexible electrode arrays, round window access, and routine intraoperative corticosteroid use. Image-based planning was unanimously endorsed for electrode array selection, and all experts favoured longer electrode arrays even in patients with functional low-frequency hearing. Variability persisted in the adoption of genetic testing, perioperative management, intraoperative monitoring, and fitting strategies, although anatomy-based fitting was most frequently selected. Training of surgeons and audiologists was universally regarded as essential. Conclusions: This survey demonstrates a clear evolution toward a shared expert framework for HSP-oriented cochlear implantation surgery, with several principles approaching consensus. Remaining variability highlights a) areas for future research and development and b) supports the continued international collaboration toward standardized HSP practice.

Five-year cognitive outcomes after cochlear implantation in older adults with severe-to-profound hearing loss

Effect of Mandibular Advancement Device Treatment on the Site-Specific Degree of Upper Airway Collapse During Drug-Induced Sleep Endoscopy

Background: Mandibular advancement device (MAD) therapy is a non-invasive treatment for obstructive sleep apnea (OSA). Although the effect of MAD on OSA outcomes is widely known, its effect on the upper airway collapse degree remains poorly understood. This study aimed to assess the impact of MAD therapy on site-specific airway collapse degree during drug-induced sleep endoscopy (DISE). Methods: One hundred participants were recruited and underwent a baseline polysomnography. Overall, 69 participants with OSA (AHI 5–50 events/h) underwent DISE at baseline and with MAD set to 75% of maximal mandibular protrusion. Collapse degree (none, partial, complete) was evaluated at the palate, oropharynx, tongue base, hypopharynx, and epiglottis without and with MAD. Ordinal logistic regression was used to analyze changes in degree of collapse. Results: MAD therapy reduced collapse degree at the palate (OR = 5.92 [3.28; 10.66], p < 0.001), oropharynx (OR = 2.70 [1.48; 4.92], p = 0.001), tongue base (OR = 1.83 [1.32; 2.53], p < 0.001), and hypopharynx (OR = 2.90 [1.53; 5.48, p = 0.001), with no effect at the epiglottis (OR = 0.65 [0.42; 1.02], p = 0.058). Conclusions: MAD therapy reduces upper airway collapse at most anatomical levels, except at the level of the epiglottis. These findings confirm its therapeutic efficacy while underscoring the importance of identifying patients with residual or worsening collapse who may benefit from combined or alternative treatments.

Health-Related Quality of Life Among People With Bilateral Vestibulopathy With and Without Hearing Loss: A Prospective Study Using Generic and Disease-Specific Instruments

Anatomical investigation of safety determining factors for keyhole drilling trajectories for robotic cochlear implant surgery

PURPOSE: Cochlear implants (CI) are the most successful bioprosthesis in medicine probably due to the tonotopic anatomy of the auditory pathway and of course the brain plasticity. Correct placement of the CI arrays, respecting the inner ear anatomy are therefore important. The ideal trajectory to insert a cochlear implant array is defined by an entrance through the round window membrane and continues as long as possible parallel to the basal turn of the cochlea. Image-guided surgery can directly drill with a robotic arm through the mastoid and execute an exact drilling of this precalculated most ideal trajectory. Here, we aim to identify critical anatomical structures determining the safest keyhole drilling trajectory by comparing easy and difficult CI surgeries performed with the HEARO Procedure: a robotic tool for image-guided surgery. METHODS: Cone-beam computed tomography images of patients who underwent robot-assisted cochlear implantation surgery (RACIS) were included. Three of 25 cases had to be converted to conventional surgery because of the current safety mitigations based on anatomical distance. Radiological images in DICOM format were transferred to dedicated software (OTOPLAN® Cascination GMHB Bern Switzerland) for analyses. Surgical segmentation and previously planned trajectories were analyzed for these 25 cases by comparing cochlear sizes, facial recess sizes, round window sizes, and trajectory angles. In addition, facial recess angle, and cochlear orientation angles were measured with RadiAnt DICOM Viewer (Medixant, Pozan, Poland). RESULTS: Facial recess size, facial recess angle, and distance between the facial nerve and safe trajectory were smaller in patient who converted from robotic surgery to conventional. A significant positive correlation existed between basal turn angle and in-plane angle (p = 0.001, r = 0.859). In addition, there was a significant negative correlation between the basal turn length and the last electrode insertion depth degree (p = 0.007, r = 0.545). CONCLUSION: In our robotic surgery cases, we demonstrate that the limiting factors of anatomical relationships are constituted by the dimensions of the facial recess and the cochlear orientation. The findings of this study are considered to be a reference for future studies in achieving collision-free trajectory planning in robotic-assisted cochlear implant surgery.

Next-generation Robotics in Otology: The HEARO Procedure

BACKGROUND: In a world that is globalizing and centered on rapid communication, hearing impairment is one of the most common disabilities. The most effective and successful neural prosthesis in humans for treating the dysfunction of a sensory organ is cochlear implantation. The minimally invasive placement of the array in the cochlea should warrant the rehabilitation of profound hearing loss over all frequencies. Some key factors for structure and hearing preservation consist of minimal invasive drilling in the temporal bone and tailored inner ear access. Next-generation Robotically Assisted Cochlear Implantation Surgery (RACIS) focuses on robotic inner ear access. The purpose of this cadaveric preclinical study was to assess the viability and precision of a novel technology (the HEARO method) for RACIS, or more particularly, personalized robotic inner ear access. METHODS: The external auditory canal, chorda tympani, ossicles, facial nerve, and other pertinent anatomical components were all 3-dimensional (3D)-reconstructed by the surgeon. The mean intended distance and drilling trajectory to the chorda tympani and facial nerve were, respectively, 0.44±0.13 and 0.35±0.27 mm. RESULTS: With a mean insertion percentage of 94%, the surgeon was able to complete the HEARO method in 9 out of 10 procedures. There was no evidence of a collision or damage to vital structures. CONCLUSION: Future iterations of RACIS will prioritize haptic feedback, automated segmentation and trajectory, robotic insertion with adjustable speed, and imaging mobile cone beam computed tomography.

Defining the ideal trajectory into the inner ear in image-guided cochlear implant surgery

The aim of robot-assisted cochlear implant surgery (RACIS) is to access the inner ear with minimal trauma. High-resolution imaging, empowered with a highly accurate navigation system can enable the planning of a direct keyhole drilling trajectory toward the inner ear. The time has come to (re)define the ideal trajectory into the inner ear with robot-assisted tools that can drill with the highest accuracy. The trajectories of past RACIS procedures were analysed to gain insight into how to calculate the most ideal trajectory and to determine which trajectory parameters influence the course of the procedure. Data-analysis was performed on three groups of previously performed RACIS-procedures. Group 1 included the RACIS-procedures with a round window (RW) approach. Group 2 included the RACIS-procedures with difficulty entering the inner ear. Group 3 included the converted cases to conventional CI surgery due to inadequate intra-operative safety margins. The RW diameter was significantly smaller and its orientation significantly less favourable in group 2 compared to group 1. A smaller surface size and an unfavourable orientation of the RW in relation to the drilling trajectory are thus associated with a more difficult electrode array insertion in RACIS. Both must be taken into account when planning a drilling trajectory into the inner ear.

Testing for genetic and viral etiologies in congenital hearing loss based on a survey of cochlear implant centers: proposed HEARRING group consensus and future directions

Background In cases of congenital sensorineural hearing loss, testing for genetic etiologies and congenital cytomegalovirus (cCMV) infection have become common practice.Aims/Objectives The purpose of this study is to determine which specific testing methodologies should be used and when.Material and methods We surveyed 20 practicing otolaryngologists across eighteen institutions in thirteen countries about their approach to cCMV, GJB2, and wider genetic testing.Results We found 90% of respondents employ all three tests, either in routine or special cases. cCMV testing is widely used, with 95% of respondents incorporating it into their clinical practice. GJB2 testing was employed by 90%. In cases with negative GJB2 test results, a majority of respondents proceeded to wider genetic screening. Test reimbursement was also examined for each test. For cCMV testing, 63.1% reported reimbursement, 68.4% reported reimbursement for GJB2 variant testing and 52.6% reported reimbursement for wider genetic screening.Conclusions and significance A common approach is to perform cCMV and GJB2 testing as the first tests, followed by wider genetic testing. This study offers insight into the prevalence, methodologies, and reimbursement status of these testing methodologies across multiple hearing centers and countries. Current consensus and future directions are described based on the current survey.

HEARRING group genetic marker study: genetic background of CI patients

BACKGROUND: While cochlear implantation (CI) and electric acoustic stimulation (EAS) have a positive outcome in most cases, their effectiveness varies depending on the etiology of the hearing loss. Among the various etiologies, genetic factors are the leading cause of hearing loss and may impact CI and EAS outcomes. AIMS/OBJECTIVES: To reveal the genetic background of the hearing loss in CI/EAS patients in each ethnic population, we undertook a multi-center study involving the genetic testing of hearing loss in CI/EAS patients from 10 centers. MATERIAL AND METHODS: Saliva samples and clinical information for the patients and their family members were obtained and next-generation sequencing analysis using a panel carrying 63 deafness genes was then performed. RESULTS: Genetic testing successfully identified the causative gene variants in 54.5% (48/88) of patients with pre-lingual onset hearing loss (onset under 6 years) and in 12% (12/95) of those with late-onset hearing loss (onset at 6 years or more). CONCLUSIONS AND SIGNIFICANCE: We clearly indicated that genetic factors are the most common cause of hearing loss regardless of ethnic background. Saliva-based genetic testing is a useful tool for multi-center studies seeking to clarify the genetic causes of hearing loss in CI or EAS patients between countries separated by distance.

Cognitive Changes Up to 4 Years After Cochlear Implantation in Older Adults: A Prospective Longitudinal Study Using the RBANS-H

Objectives: Hearing loss is a worldwide health problem that currently affects around 20% of the world’s population. Untreated hearing loss can have a significant impact on daily life, it can cause social isolation, loneliness, frustration, and higher anxiety and depression rates. Furthermore, older adults with hearing impairment have a higher risk for accelerated cognitive decline compared with normal-hearing individuals. Previous research indicated a positive effect of cochlear implantation on Health-related Quality of life (HRQoL) and cognitive functioning 1 year after cochlear implantation. The aim of this study was to evaluate the long-term effect of cochlear implantation on cognition and HRQoL in older adults with severe-to-profound hearing loss. Design: All included subjects were 55 years or older with postlingual, bilateral, severe-to-profound hearing loss, and received a unilateral cochlear implant. Cognition was evaluated using the Repeatable Battery for the Assessment of Neuropsychological Status for Hearing Impaired Individuals (RBANS-H), and HRQoL was evaluated using the following five questionnaires: Nijmegen Cochlear Implant Questionnaire (NCIQ); Hearing Implant Sound Quality Index (HISQUI); Speech, Spatial, and Qualities of Hearing Scale (SSQ12); Hospital Anxiety and Depression scale (HADS); and Type D questionnaire (DS14). Individuals were evaluated preoperatively, and annually up to 4 years after CI activation. Results: After cochlear implantation an improvement in hearing, cognition, and HRQoL was observed. When comparing preoperative and 12 months postoperative results a significant improvement was observed in the total RBANS-H score (mean [SD], 92.78 [±15.08] versus 98.35 [±14.18], p < 0.001) and the subdomain scores for “Immediate Memory” (94.13 [±18.75] versus 105.39 [±19.98], p = 0.005), “Attention” (86.17 [±19.02] versus 91.57 [±15.35], p = 0.048), and “Delayed memory” (97.91 [±14.51] versus 103.83 [±14.714], p = 0.017). When comparing preoperative results with 4 years postoperative results, a significant improvement was observed in “Immediate Memory” (94.13 [±18.75] versus 101.91 [±16.09], p = 0.020) and a significant decline was observed in “Visuospatial Memory” (97.04 [±17.47] versus 87.26 [±13.41], p = 0.013). Compared with the preoperative results, no significant improvement was observed in the total RBANS-H score 4 years after implantation. A significant improvement was observed for the HRQoL questionnaires, that is, NCIQ, HISQUI19, SSQ12, HADS, and DS14, 1 year after cochlear implantation. When comparing preoperative results with 4-year postoperative results, significant improvement was observed for the NCIQ and DS14 social inhibition scores. Long-term results of the SSQ12 and HISQUI19 were lacking. Conclusions: Unilateral cochlear implantation in an adult population with bilateral severe-to-profound sensorineural hearing loss has a positive effect on cognitive functioning and HRQoL 1 year after activation. This positive effect on cognitive functioning was no longer observed 4 years after cochlear implantation. Further research is needed to explain individual variation in the evolution of cognitive functioning.

Current status of pediatric auditory brainstem implantation in inner ear malformations; consensus statement of the Third International Pediatric ABI Meeting

OBJECTIVES: This study aims to synthesize current knowledge and outcomes related to pediatric auditory brainstem implantation (ABI) in children with severe inner ear malformations (IEMs). It highlights the clinical management practices, challenges, and potential future directions for consensus development in this field. METHODS: A systematic review of findings presented at the Third International Pediatric ABI Symposium organized by the Hacettepe Cochlear Implant team between 3 and 5 September 2020 was conducted, incorporating data from 41 departments across 19 countries. Relevant clinical outcomes, imaging techniques, surgical approaches, and rehabilitation strategies were analyzed to identify key trends and variability in practices. RESULTS: The review indicates that children receiving ABIs exhibit diverse auditory outcomes influenced by individual anatomical variations and developmental factors. Early implantation, particularly before the age of three, positively correlates with better auditory and language development. Multicenter experiences underscore the necessity of tailored decision-making, which considers both surgical candidacy and comprehensive rehabilitation resources. DISCUSSION: The variability in outcomes emphasizes the need for improved consensus and guidelines regarding eligibility, surgical techniques, and multidisciplinary rehabilitation approaches. Notable complications and the necessity for thorough imaging assessments were also identified as critical components affecting clinical decisions. CONCLUSION: A formal consensus statement is warranted to standardize best practices in ABI management. This will not only enhance patient outcomes but also guide future research efforts to address the remaining challenges in the treatment of children with severe IEMs. Enhanced collaboration among team members will be pivotal in achieving these objectives.

Metronome-guided cochlear implantation for slower and smoother insertions of lateral wall electrodes

Achieving a slow and smooth electrode array insertion is paramount for preserving structural and functional integrity during cochlear implantation. This controlled study evaluates the efficacy of a metronome-guided insertion technique in enhancing the smoothness and speed of electrode array insertions.

Electrically evoked compound action potentials are associated with the site of intracochlear stimulation

Objective measurements to predict the position of a cochlear electrode during cochlear implantation surgery may serve to improve the surgical technique and postoperative speech outcome. There is evidence that electrically evoked compound action potentials (ECAP) are a suitable approach to provide information about the site of stimulation. This study aims to contribute to the knowledge about the association between the intraoperative intracochlear ECAP characteristics and the site of stimulation.

Effect of Cochlear Implant Electrode Insertion Depth on Speech Perception Outcomes: A Systematic Review

Objective: The suitable electrode array choice is broadly discussed in cochlear implantation surgery. Whether to use a shorter electrode length under the aim of structure preservation versus choosing a longer array to achieve a greater cochlear coverage is a matter of debate. The aim of this review is to identify the impact of the insertion depth of a cochlear implant (CI) electrode array on CI users' speech perception outcomes. Databases Reviewed: PubMed was searched for English-language articles that were published in a peer-reviewed journal from 1997 to 2022. Methods: A systematic electronic search of the literature was carried out using PubMed to find relevant literature on the impact of insertion depth on speech perception. The review was conducted according to the preferred reporting items for systematic reviews and meta-analyses guidelines of reporting. Studies in both, children and adults with pre- or postlingual hearing loss, implanted with a CI were included in this study. Articles written in languages other than English, literature reviews, meta-analyses, animal studies, histopathological studies, or studies pertaining exclusively to imaging modalities without reporting correlations between insertion depth and speech outcomes were excluded. The risk of bias was determined using the "Risk of Bias in Nonrandomized Studies of Interventions" tool. Articles were extracted by 2 authors independently using predefined search terms. The titles and abstracts were screened manually to identify studies that potentially meet the inclusion criteria. The extracted information included: the study population, type of hearing loss, outcomes reported, devices used, speech perception outcomes, insertion depth (linear insertion depth and/or the angular insertion depth), and correlation between insertion depth and the speech perception outcomes. Results: A total of 215 relevant studies were assessed for eligibility. Twenty-three studies met the inclusion criteria and were analyzed further. Seven studies found no significant correlation between insertion depth and speech perception outcomes. Fifteen found either a significant positive correlation or a positive effect between insertion depth and speech perception. Only 1 study found a significant negative correlation between insertion depth and speech perception outcomes. Conclusion: Although most studies reported a positive effect of insertion depth on speech perception outcomes, one-third of the identified studies reported no correlation. Thus, the insertion depth must be considered as a contributing factor to speech perception rather than as a major decisive criterion. Registration: This review has been registered in PROSPERO, the international prospective register of systematic reviews (CRD42021257547), available at https://www.crd.york.ac.uk/PROSPERO/.

Etiologies and hearing status in bilateral vestibulopathy: a retrospective study of 315 patients

Importance The development of a vestibular implant has reached milestones and seems to be a promising therapeutic tool for bilateral vestibulopathy (BV). Given the former lack of therapeutic options for BV, the disease has received scant attention in the previous research literature. It is therefore of major importance to gain more insight into the underlying pathology of BV. Furthermore, as some research groups specifically use a combined vestibulo-cochlear implant, the size of the group of BV patients with associated hearing loss is of special interest. Objectives The study aimed to determine the definite and probable etiology in bilateral vestibulopathy (BV) patients and to report on their hearing status. Design This study involves multicenter retrospective study design. Setting The research setting is at tertiary referral centers. Participants Consecutive BV patients diagnosed at the Antwerp University Hospital between 2004 and 2018 at the Maastricht University Medical Center between 2002 and 2015 and at the Geneva University Hospital between 2013 and 2018, who met the BV diagnostic criteria of the Bárány Society. Main outcome measures Primary interests were the etiology and hearing status of BV patients. Moreover, the data of vestibular tests were examined (caloric irrigation, rotatory chair tests, and video-head impulse test). Results The authors identified 315 BV patients, of whom 56% were male patients. Mean age at diagnosis was 58.6 ± 15.1 (range 7–91) years. The definite cause was determined in 37% of the patients and the probable cause in 26% of the patients. No cause was identified in 37% of BV patients. The largest subgroup included patients with genetic etiology (31%), most frequently COCH mutation. Only 21% of patients (n = 61) had bilateral normal hearing. Almost half of the patients (45%, n = 134) had profound hearing loss in at least one ear. Conclusion BV is a heterogeneous condition, with over a third of cases remaining idiopathic, and nearly three-quarters affected by hearing loss. COCH mutation is the most common non-idiopathic cause of BV in our population. Only 21% of our BV patients presented with bilateral normal hearing.

QoL, CIs, QALYs, and Individualized Rehabilitation: The Clinical and Practical Benefits of Regularly Assessing the Quality of Life of Adult Cochlear Implant Recipients

This study aimed to report quality of life (QoL) scores in unilateral cochlear implant (CI) users and to generate guidance for clinicians on using QoL measures to individualize CI counselling and rehabilitation and to increase access to CIs as a mode of rehabilitation. Participants (n = 101) were unilateral CI users with single-sided deafness (SSD; n = 17), asymmetrical hearing loss (AHL; n = 26), or bilateral hearing loss (Uni; n = 58). Generic QoL was assessed via the Health Utilities Index (HUI-3), and disease-specific QoL was assessed via the Speech, Spatial, and Qualities of Hearing scale (SSQ12) and Nijmegen CI Questionnaire (NCIQ) at preimplantation and at 6 and 12 months of CI use. All groups had significantly increased HUI-3 scores at both intervals. The SSD group showed significant benefit on the SSQ12 at visit 3, the AHL group showed significant benefit on the SSQ12 and most NCIQ subdomains at both intervals, and the Uni group showed significant benefit with both tests at both intervals. Unilateral CI recipients demonstrate improved QoL within the first 12 months of device use. Regular assessment with generic and disease-specific questionnaires has the potential to play an important role in personalizing treatment and possibly in increasing access to CI provision.

Implementation of the International Classification of Functioning, Disability and Health model in cochlear implant recipients: a multi-center prospective follow-up cohort study

Introduction No standard protocol based on a multidisciplinary framework currently exists for the evaluation, follow-up and interpretation of Cochlear Implant (CI) outcomes in clinical routine. Therefore, this study aimed to develop and clinically implement a multidimensional Cochlear Implant (CI) outcome assessment protocol for adult CI users based on the International Classification of Functioning, Disability and Health (ICF). Methods An international multidisciplinary core group of CI experts selected the most relevant ICF categories and codes for adult CI users out of the existing ICF core set for hearing loss. A well-known, commonly used instrument or method was identified and assigned to each ICF category along with quantified ICF qualifiers. These qualifiers facilitate the interpretation of CI outcomes by categorizing the outcome on a rating scale between 0 and 4, based on the severity of participants' impairment/restriction/limitation/barrier. The ICF-based CI outcome assessment protocol was applied in clinical routine in a prospective longitudinal multicenter study assessing a consecutive sample of 72 adult CI candidates before and 6 months after implantation. For each relevant ICF category, the participants' improvement, stability or deterioration was specified in a descriptive approach using ICF qualifiers. Results Participants either showed improved or stable ICF qualifiers after cochlear implantation across all ICF domains (e.g., Body Functions and Structures, Activities, and Participation and Environmental factors). The ICF qualifiers for environmental sound tolerance ( n = 30 [45%]) and vestibular functions ( n = 21 [33%]) deteriorated most frequently after implantation. ICF qualifiers for falling ( n = 53 [83%]) and dizziness ( n = 40 [62%]) remained stable in most participants. Auditory perception-related and communication-related categories generally improved in most participants after cochlear implantation, with 46 to 73% ( n = 34 to n = 48) of CI users perceiving an improvement postoperatively. Conclusion This study is the first to propose and apply a ready-to-use CI outcome assessment protocol based on the ICF model, which provides a common language and comprehensive assessment protocol for the description and measurement of CI outcomes worldwide. Its straightforward outcome description and rating enables CI outcome interpretation by non-experts, enhancing multidisciplinary communication and knowledge on individual healthcare needs in CI users.

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.

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.