Computational evaluation of cochlear implant surgery outcomes accounting for uncertainty and parameter variability

Cochlear implantation (CI) is a complex surgical procedure that restores hearing in patients with severe deafness. The successful outcome of the implanted device relies on a group of factors, some of them unpredictable or difficult to control. Uncertainties on the electrode array position and the electrical properties of the bone make it difficult to accurately compute the current propagation delivered by the implant and the resulting neural activation. In this context, we use uncertainty quantification methods to explore how these uncertainties propagate through all the stages of CI computational simulations. To this end, we employ an automatic framework, encompassing from the finite element generation of CI models to the assessment of the neural response induced by the implant stimulation. To estimate the confidence intervals of the simulated neural response, we propose two approaches. First, we encode the variability of the cochlear morphology among the population through a statistical shape model. This allows us to generate a population of virtual patients using Monte Carlo sampling and to assign to each of them a set of parameter values according to a statistical distribution. The framework is implemented and parallelized in a High Throughput Computing environment that enables to maximize the available computing resources. Secondly, we perform a patient-specific study to evaluate the computed neural response to seek the optimal post-implantation stimulus levels. Considering a single cochlear morphology, the uncertainty in tissue electrical resistivity and surgical insertion parameters is propagated using the Probabilistic Collocation method, which reduces the number of samples to evaluate. Results show that bone resistivity has the highest influence on CI outcomes. In conjunction with the variability of the cochlear length, worst outcomes are obtained for small cochleae with high resistivity values. However, the effect of the surgical insertion length on the CI outcomes could not be clearly observed, since its impact may be concealed by the other considered parameters. Whereas the Monte Carlo approach implies a high computational cost, Probabilistic Collocation presents a suitable trade-off between precision and computational time. Results suggest that the proposed framework has a great potential to help in both surgical planning decisions and in the audiological setting process

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

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

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

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

Quality-assured training in the evaluation of cochlear implant electrode position: a prospective experimental study

Background The objective of this study was to demonstrate the utility of an approach in training predoctoral medical students, to enable them to measure electrode-to-modiolus distances (EMDs) and insertion-depth angles (aDOIs) in cochlear implant (CI) imaging at the performance level of a single senior rater. Methods This prospective experimental study was conducted on a clinical training dataset comprising patients undergoing cochlear implantation with a Nucleus® CI532 Slim Modiolar electrode (N = 20) or a CI512 Contour Advance electrode (N = 10). To assess the learning curves of a single medical student in measuring EMD and aDOI, interrater differences (senior-student) were compared with the intrarater differences of a single senior rater (test-retest). The interrater and intrarater range were both calculated as the distance between the 0.1th and 99.9th percentiles. A "deliberate practice" training approach was used to teach knowledge and skills, while correctives were applied to minimize faulty data-gathering and data synthesis. Results Intrarater differences of the senior rater ranged from - 0.5 to 0.5 mm for EMD and - 14° to 16° for aDOI (respective medians: 0 mm and 0°). Use of the training approach led to interrater differences that matched this after the 4th (EMD) and 3rd (aDOI) feedback/measurement series had been provided to the student. Conclusions The training approach enabled the student to evaluate the CI electrode position at the performance level of a senior rater. This finding may offer a basis for ongoing clinical quality assurance for the assessment of CI electrode position

Elektrophysiologische Effekte der slim straight intracochlearen Elektrodenposition

Introduction: Cochlear implantation is the treatment of choice for patients with profound-to-severe sensorineural hearing loss who retain residual hearing. The electrical current distribution of a cochlear implant electrode array is essential for an optimal postoperative hearing benefit. Placement of an electrode contact in a lateral or medial direction to the modiolus is possible with a slim straight electrode design. The electrophysiological effect of this different contact position appears to be unknown. Objective: Our goal is to investigate the electrophysiological effects with different intracochlear electrode contact positions. Study design: Retrospective clinical and descriptive experimental Setting: Tertiary referral center. Material and Methods: A slim straight electrode was inserted into the cochleae of five patients (two female and three male) and the neural response thresholds (NRT’s) were measured in a lateral and medial directed contact position. Additionally, the cochleae in five temporal cadaveric bones were de-capped to allow for in-vitro direct observation of the inserted slim straight electrode contact position, either in a lateral versus medial position. Results: There was no significant difference in NRT’s between lateral versus medial contact position. While the in-vitro temporal bone study indicated no intracochlear torsion behaviour within the lateral or medial electrode contact position. Conclusion: Our results suggest that the intracochlear positioning of a slim straight electrode does not affect NRT’s.Einleitung: Cochleaimplantate ist die Behandlung der Wahl für Patienten mit hoch bis schwergradiger Innenohrschwerhörigkeit, die noch Resthörvermögen haben. Die elektrische Stromverteilung innerhalb der Cochlea durch eine Cochlea- Implantatelektrode ist für eine optimale postoperative Hörleistung entscheidend. Eine Slim Straight Elektrode ermöglicht die Platzierung der Elektrodenkontakte in lateraler oder medialer Richtung zum Modiolus. Die elektrophysiologische Wirkung dieser unterschiedlichen Kontaktrichtungen erscheint bisher unbekannt. Studienziel: Das Ziel dieser Studie war es, den Einfluss der intracochlearen lateralen oder medialen Elektrodenplatzierung auf das elektrophysiologische Verhalten zu untersuchen. Studiendesign: Retrospektive klinisch und deskriptiv experimentelle Studienort: überregionales Krankenhaus der Maximalversorgung. Material und Methoden: Eine slim-straight Elektrode wurde in die Cochlea von fünf Patienten (zwei weibliche und drei männliche) eingeführt und die daraus resultierende Neural Response Thresholds (NRT’s) in lateral sowie medial ausgerichteter Kontaktposition gemessen. Außerdem erfolgte einer in-vitro Untersuchung der Cochlea (de-capping) aus dem Felsenbein von insgesamt fünf Spendern. So konnte die Insertionsverhalten der jeweiligen Elektrodenkontaktposition (lateral gegenüber medial) beobachtet / ausgewertet werden. Ergebnisse: Es zeigten sich keine signifikante Unterschiede in den NRT‘s zwischen der lateralen und der medialen Position der Elektrodenkontakte. Die in-vitro Felsenbeinstudie konnte kein intracochleares Torsionsverhalten der Elektrode innerhalb der lateralen oder medialen Positionierung nachweisen. Fazit: Die Ergebnisse deuten darauf hin, dass die intracochleare Position von Slim Straight Elektroden die NRT‘s nicht beeinflusst

Development and significance of the spatial auditory change complex in adult cochlear implant users

Despite their great success, cochlear implants (CIs) are associated with a wide range in speech perception outcomes. Interactions of electrode contacts on the CI array, resulting in impaired transmission of the auditory signal, may contribute to poor outcome in certain individuals. The aim of this thesis was to determine whether the spatial auditory change complex (ACC), an electrophysiological measure of electrode discrimination, could be used to objectively assess electrode independence, with a view to using this as a clinical tool for patient assessment. In a series of experiments, the spatial ACC and behavioural electrode discrimination were measured in adult CI users. It was found that it is feasible to measure the spatial ACC in CI devices from different manufacturers and during the early period after switch-on. There was a strong relationship between objective and behavioural measures of electrode discrimination and in several cases, the development of the spatial ACC preceded accurate behavioural discrimination. Longitudinal measurements revealed that the amplitude of the spatial ACC and behavioural discrimination scores increased significantly over the first 6 to 12 months of CI use, providing evidence for auditory plasticity. The time course of adaptation varied substantially, and was slower and more limited in certain individuals. Speech perception was found to be more consistently related to behavioural measures of electrode discrimination than to the spatial ACC. Increasing stimulus intensity led to a significant increase in the spatial ACC amplitude and behavioural discrimination scores. By altering the recording setup and stimulus characteristics, the efficiency and sensitivity of spatial ACC measurements could be improved. These findings show that the spatial ACC provides a useful measure of electrode independence. It is proposed that these measurements could be used to guide clinical interventions that lead to improved hearing outcome in CI users

Three-dimensional models of cochlear implants : a review of their development and how they could support management and maintenance of cochlear implant performance

Three-dimensional (3D) computational modelling of the auditory periphery forms an integral part of modern-day research in cochlear implants (CIs). These models consist of a volume conduction description of implanted stimulation electrodes and the current distribution around these, coupled to auditory nerve fibre models. Cochlear neural activation patterns can then be predicted for a given input stimulus. The objective of this article is to present the context of 3D modelling within the field of CIs, the different models and approaches to models that have been developed over the years, as well as the applications and potential applications of these models. The process of development of 3D models is discussed, and the article places specific emphasis on the complementary roles of generic models and user-specific models, as the latter is important for translation of these models into clinical application.http://tandfonline.com/toc/inet202017-05-31hb2016Electrical, Electronic and Computer Engineerin

The Human Auditory System

This book presents the latest findings in clinical audiology with a strong emphasis on new emerging technologies that facilitate and optimize a better assessment of the patient. The book has been edited with a strong educational perspective (all chapters include an introduction to their corresponding topic and a glossary of terms). The book contains material suitable for graduate students in audiology, ENT, hearing science and neuroscience