Bart Vaerenberg

Cochlear Implant Programming: A Global Survey on the State of the Art

The programming of CIs is essential for good performance. However, no Good Clinical Practice guidelines exist. This paper reports on the results of an inventory of the current practice worldwide. A questionnaire was distributed to 47 CI centers. They follow 47600 recipients in 17 countries and 5 continents. The results were discussed during a debate. Sixty-two percent of the results were verified through individual interviews during the following months. Most centers (72%) participated in a cross-sectional study logging 5 consecutive fitting sessions in 5 different recipients. Data indicate that general practice starts with a single switch-on session, followed by three monthly sessions, three quarterly sessions, and then annual sessions, all containing one hour of programming and testing. The main focus lies on setting maximum and, to a lesser extent, minimum current levels per electrode. These levels are often determined on a few electrodes and then extrapolated. They are mainly based on subjective loudness perception by the CI user and, to a lesser extent, on pure tone and speech audiometry. Objective measures play a small role as indication of the global MAP profile. Other MAP parameters are rarely modified. Measurable targets are only defined for pure tone audiometry. Huge variation exists between centers on all aspects of the fitting practice.

Development of a Software Tool Using Deterministic Logic for the Optimization of Cochlear Implant Processor Programming

Objective: An intelligent agent, Fitting to Outcomes eXpert, was developed to optimize and automate Cochlear implant (CI) programming. The current article describes the rationale, development, and features of this tool. Background: Cochlear implant fitting is a time-consuming procedure to define the value of a subset of the available electric parameters based primarily on behavioral responses. It is comfort-driven with high intraindividual and interindividual variability both with respect to the patient and to the clinician. Its validity in terms of process control can be questioned. Good clinical practice would require an outcome-driven approach. An intelligent agent may help solve the complexity of addressing more electric parameters based on a range of outcome measures. Methods: A software application was developed that consists of deterministic rules that analyze the map settings in the processor together with psychoacoustic test results (audiogram, A§E phoneme discrimination, A§E loudness scaling, speech audiogram) obtained with that map. The rules were based on the daily clinical practice and the expertise of the CI programmers. The data transfer to and from this agent is either manual or through seamless digital communication with the CI fitting database and the psychoacoustic test suite. It recommends and executes modifications to the map settings to improve the outcome. Results: Fitting to Outcomes eXpert is an operational intelligent agent, the principles of which are described. Its development and modes of operation are outlined, and a case example is given. Fitting to Outcomes eXpert is in use for more than a year now and seems to be capable to improve the measured outcome. Conclusion: It is argued that this novel tool allows a systematic approach focusing on outcome, reducing the fitting time, and improving the quality of fitting. It introduces principles of artificial intelligence in the process of CI fitting.

Clinical assessment of pitch perception.

Objective: The perception of pitch has recently gained attention. At present, clinical audiologic tests to assess this are hardly available. This article reports on the development of a clinical test using harmonic intonation (HI) and disharmonic intonation (DI). Study Design: Prospective collection of normative data and pilot study in hearing-impaired subjects. Setting: Tertiary referral center. Patients: Normative data were collected from 90 normal-hearing subjects recruited from 3 different language backgrounds. The pilot study was conducted on 18 hearing-impaired individuals who were selected into 3 pathologic groups: high-frequency hearing loss (HF), low-frequency hearing loss (LF), and cochlear implant users (CI). Intervention(s): Normative data collection and exploratory diagnostics by means of the newly constructed HI/DI tests using intonation patterns to find the just noticeable difference (JND) for pitch discrimination in low-frequency harmonic complex sounds presented in a same-different task. Main Outcome Measure(s): JND for pitch discrimination using HI/DI tests in the hearing population and pathologic groups. Results: Normative data are presented in 5 parameter statistics and box-and-whisker plots showing median JNDs of 2 (HI) and 3 Hz (DI). The results on both tests are statistically abnormal in LF and CI subjects, whereas they are not significantly abnormal in the HF group. Conclusion: The HI and DI tests allow the clinical assessment of low-frequency pitch perception. The data obtained in this study define the normal zone for both tests. Preliminary results indicate possible abnormal TFS perception in some hearing-impaired subjects.

Experiences of the use of FOX, an intelligent agent, for programming cochlear implant sound processors in new users.

Abstract Objective. This report describes the application of the software tool “Fitting to Outcomes eXpert” (FOX) in programming the cochlear implant (CI) processor in new users. FOX is an intelligent agent to assist in the programming of CI processors. The concept of FOX is to modify maps on the basis of specific outcome measures, achieved using heuristic logic and based on a set of deterministic “rules”. Design. A prospective study was conducted on eight consecutive CI-users with a follow-up of three months. Study Sample. Eight adult subjects with postlingual deafness were implanted with the Advanced Bionics HiRes90k device. The implants were programmed using FOX, running a set of rules known as Eargroups EG0910 advice, which features a set of “automaps”. The protocol employed for the initial 3 months is presented, with description of the map modifications generated by FOX and the corresponding psychoacoustic test results. Results. The 3 month median results show 25 dBHL as PTA, 77% (55 dBSPL) and 71% (70 dBSPL) phoneme score at speech audiometry and loudness scaling in or near to the normal zone at different frequencies. Conclusions. It is concluded that this approach is feasible to start up CI fitting and yields good outcome. Sumario Objetivo: Este reporte describe la aplicación del programa-herramienta “Fitting to Outcomes eXpert” (“eXperto en adaptación por resultados”) (FOX) en la programación de procesadores de implante coclear (IC) para usuarios nuevos. El concepto de FOX es modificar los mapas sobre la base de medidas específicas de resultados, logradas usando una lógica heurística y basado en un grupo de “reglas” determinísticas. DiseÑo: Se condujo un estudio prospectivo en ocho usuarios consecutivos de CI con un seguimiento de tres meses. Muestra Del Estudio: Ocho sujetos adultos con sordera post-lingüística fueron implantados con el dispositivo Advanced Bionics HiRes90k. Los implantes fueron programados usando el FOX, usando un grupo de reglas conocidas como consejo EG910 del EarGroup, que presenta un grupo de “automapas”. Se presenta el protocolo empleado para los primeros 3 meses, con descripción de las modificaciones de los mapas generados con FOX y los resultados de las pruebas psicoacústicas correspondientes. Resultados: La mediana de los resultados a 3 meses muestra un PTA de 25 dB HL, puntajes de fonemas en la logoaudiometría de 77% (55 dB SPL) y 71% (70 dB SPL), y una escala de intensidad subjetiva dentro o cercana a la zona normal en diferentes frecuencias. Conclusiones: Se concluye que este enfoque es factible para iniciar la programación de un CI y que brinda buenos resultados.

A uniform graphical representation of intensity coding in current-generation cochlear implant systems.

Objectives: Understanding and predicting the impact of MAP changes on the electrical current delivered at the level of cochlear implant (CI) electrodes is challenging. However, it is an important prerequisite for effectively programming these devices in clinical practice. This article describes a graphical representation to illustrate the intensity-coding behavior of four CI systems (Cochlear, MED-EL, Advanced Bionics, and Neurelec). Design: For this the authors have broken down the intensity coding into two separate transformations: (1) from broadband acoustical input to band limited channel amplitude and (2) the mapping function within a single channel. These functions have been synthesized and presented in a uniform plot across brands. Results: The plot describes the output of a CI channel in response to different input signals. This has been incorporated in an interactive software application that illustrates the different stages of intensity coding and the impact of the relevant fitting parameters for each CI brand. Conclusions: The plot provides the clinician with an assistive tool to better understand and predict the behavior of CIs, which may lead to more knowledgeable interpretation and CI programming.

Evaluation of the ‘Fitting to Outcomes eXpert’ (FOX®) with established cochlear implant users

Abstract Objectives To evaluate the possible impact of ‘Fitting to Outcomes eXpert (FOX®)’ on cochlear implant (CI) fitting in a clinic with extensive experience of fitting a range of CI systems, as a way to assess whether a software tool such as FOX is able to complement standard clinical procedures. Methods Ten adult post-lingually deafened and unilateral long-term users of the Advanced BionicsTM CI system (Clarion CII or HiRes 90KTM) underwent speech perception assessment with their current clinical program. One cycle ‘iteration’ of FOX optimization was performed and the program adjusted accordingly. After a month of using both clinical and FOX programs, a second iteration of FOX optimization was performed. Following this, the assessments were repeated without further acclimatization. Results FOX prescribed programming modifications in all subjects. Soundfield-aided thresholds were significantly lower for FOX than the clinical program. Group speech scores in noise were not significantly different between the two programs but three individual subjects had improved speech scores with the FOX MAP, two had worse speech scores, and five were the same. Conclusion FOX provided a standardized approach to fitting based on outcome measures rather than comfort alone. The results indicated that for this group of well-fitted patients, FOX improved outcomes in some individuals. There were significant changes, both better and worse, in individual speech perception scores but median scores remained unchanged. Soundfield-aided thresholds were significantly improved for the FOX group.

Combined electric and acoustic hearing performance with Zebra® speech processor: Speech reception, place, and temporal coding evaluation

Abstract Objective To assess the auditory performance of Digisonic® cochlear implant users with electric stimulation (ES) and electro-acoustic stimulation (EAS) with special attention to the processing of low-frequency temporal fine structure. Method Six patients implanted with a Digisonic® SP implant and showing low-frequency residual hearing were fitted with the Zebra® speech processor providing both electric and acoustic stimulation. Assessment consisted of monosyllabic speech identification tests in quiet and in noise at different presentation levels, and a pitch discrimination task using harmonic and disharmonic intonating complex sounds ( ). These tests investigate place and time coding through pitch discrimination. All tasks were performed with ES only and with EAS. Results Speech results in noise showed significant improvement with EAS when compared to ES. Whereas EAS did not yield better results in the harmonic intonation test, the improvements in the disharmonic intonation test were remarkable, suggesting better coding of pitch cues requiring phase locking. Discussion These results suggest that patients with residual hearing in the low-frequency range still have good phase-locking capacities, allowing them to process fine temporal information. ES relies mainly on place coding but provides poor low-frequency temporal coding, whereas EAS also provides temporal coding in the low-frequency range. Patients with residual phase-locking capacities can make use of these cues.

Perception of Pitch Changes in Hearing-Impaired Adults with Aided and Unaided Hearing Loss

Background: Pitch relates to the low frequency temporal content of sound, which mainly depends on phase coding at the level of the auditory nerve. In this study, we aim to assess the detectibility of pitch changes in different populations of hearingimpaired subjects suffering from sensorineural hearing loss in order to identify possible poor temporal coding. Material and Methods: A number of tests – part of the A§E (ASSE or Auditory Speech Sounds Evaluation) psychoacoustic test suite – were used to assess the perception of pitch changes in adults with a hearing loss (a) in the high frequencies with or without classical hearing aids, (b) in the low frequencies, and (c) in a group of cochlear implant users. All test stimuli were controlled for their fundamental frequency (F0), which either remained stable during the stimulus presentation or which, simulating intonation, glided from F0 to F0+∆. Isolated synthetic complexes were used as well as pseudo-words or pseudosentences mimicking linguistically relevant contexts. The subjects were asked to distinguish these sounds in either identification or discrimination tasks. Results: Hearing-impaired subjects, and particularly those with low-frequency hearing loss, performed significantly worse in comparison to hearing adults on all tests. The use of a hearing aid did not yield significant improvements. The cochlear implant users experienced great difficulty in performing the tests. Conclusion: The intonation tests of A§E2009 are a useful diagnostic tool to distinguish hearing-impaired subjects based on their capacity to process low-frequency information. The tests may be of particular use in the evaluation of the impact of auditory rehabilitation, hearing aids, or electro-acoustic stimulation.

A Probabilistic Graphical Model for Tuning Cochlear Implants

Severe and profound hearing losses can be treated with cochlear implants (CI). Given that a CI may have up to 150 tunable parameters, adjusting them is a highly complex task. For this reason, we decided to build a decision support system based on a new type of probabilistic graphical model (PGM) that we call tuning networks. Given the results of a set of audiological tests and the current status of the parameter set, the system looks for the set of changes in the parameters of the CI that will lead to the biggest improvement in the user’s hearing ability. Because of the high number of variables involved in the problem we have used an object-oriented approach to build the network. The prototype has been informally evaluated comparing its advice with those of the expert and of a previous decision support system based on deterministic rules. Tuning networks can be used to adjust other electrical or mechanical devices, not only in medicine.

Managed estimation of psychophysical thresholds

Objective: The estimation of perceptive thresholds is a basic element of psychoacoustics. One of the drawbacks of commonly used adaptive algorithms is the lack of reliability when the behavioral response is not robust. To address this issue an adaptive algorithm, TEMA (Threshold Estimation by Managed Algorithm), has been developed. Design: TEMA seeks the 50% point on the psychometric curve based on an up-down staircase procedure. Internal controls and stochastic processes aim at enhancing the reliability. The development of TEMA is described, together with its validations with reference to common adaptive procedures. Both Monte Carlo simulations and real subject testing were performed to assess the psychoacoustic threshold in intonation perception tests and the number of stimulus presentations needed. Study sample: A total of 29 adult listeners participated in the within-subjects comparison; 19 listeners had normal-hearing, the other 10 were hearing impaired (5 aided, 5 unaided). Results: The results show that TEMA outperformed commonly used algorithms in non-robust responders, with a minimal cost in terms of test duration. Conclusions: TEMA’s adaptive algorithm was shown to be significantly more resistant to gambling or cheating behavior and threshold drift than traditional, reversal-based algorithms. TEMA increases the accuracy of threshold estimation and the test reliability in non-robust responders. This makes TEMA applicable for automated threshold measurements in clinical settings. EVALUACION CONTROLADA DE LOS UMBRALES PSICOFISICOS