Rolf-Dieter Battmer

Impact of Low-Frequency Hearing

Today, cochlear implantation is the treatment of choice in the case of severe to profound hearing loss, but the speech perception abilities of many recipients in noisy conditions are still poor and the overall sound quality and ease of listening still require improvement. Residual low-frequency hearing has been associated with improved hearing performance in cochlear implant patients, especially in difficult listening environments (i.e. cocktail party effect). It seems that low-frequency information can enhance the segregation of competing voices, which leads to better speech understanding in noise. We investigated the effect of low-frequency hearing on speech perception performance in a group of subjects being implanted with the Nucleus Hybrid-L device. The Hybrid-L device is a modified Nucleus Freedom implant, which instead of the standard electrode carries a very delicate electrode array that allows preservation of residual hearing to a great extent. Sentence test results from 22 subjects are presented here. Additionally, for 8 subjects, the acoustically presented frequency range was limited to 300, 500 and 700 Hz, and speech perception tests with a single competing talker were conducted. The Hybrid-L study group achieved a speech reception threshold of 15.9 dB in the hearing aid alone condition, 10.8 dB in the cochlear implant alone condition, and 3.9 dB when using the combination of cochlear implant and hearing aid. Differences between the 3 conditions are statistically significant. Results from the additional experiment on the acoustically presented frequency range suggest that very limited residual hearing below 500 Hz is already sufficient to produce a significant improvement in speech perception performance in conjunction with a cochlear implant.

A multicenter study of device failure in European cochlear implant centers.

Objective: To evaluate the failure rate of cochlear implant systems across a range of European implant centers. Study Design: Retrospective review. Setting: Tertiary care cochlear implant centers in Europe. Material and Methods: A postal questionnaire was designed to assess the incidence and mode of total device failure and was sent to 34 European clinics. Results: Twenty seven (79%) centers replied providing data on 12,856 devices of which 488 (3.79%) had undergone total device failure. Of 8,581 Nucleus devices (Cochlear, Sydney, Australia), 169 had failed; of 1,761 Advanced Bionics systems (Advanced Bionics, Sylmar, USA), 123 had failed; of 1987 Med El devices (Med-El, Innsbruck, Austria), 179 had failed; and of 527 MXM devices (Laboratoires MXM, Vallauris, France), 17 had failed. Six (22%) centers never reported failures to competent authorities. Conclusions: The study suggests that the overall reliability of cochlear implant systems is satisfactory but that reliability varies considerably between individual systems. There is a compelling need for agreed international definitions of failure and for the adoption of uniform reporting protocols. A common database, independent of the industry, would offer greater transparency to users and clinics.

Elimination of facial nerve stimulation by reimplantation in cochlear implant subjects.

Hypothesis: Perimodiolar intracochlear electrodes with contacts facing towards the modiolus have limited current flow towards the outer wall of the cochlea and therefore, may reduce the occurence of facial nerve stimulation (FN) in cochlear implant subjects. Background: Facial nerve stimulation is a well-known complication in cochlear implant treatment especially in the group of subjects with otosclerosis. The possible explanation of this side effect is a change of the electrical properties of the otosclerotic bone leading to leakage current and resulting in facial nerve stimulation. Methods: Four CI subjects who had been implanted with a Nucleus Mini22 device with a Nucleus Straight electrode between 9 to 12 years ago suffered from severe FN stimulation. Electrode contacts had to be switched off so that they could only use 4, 11, 13, and 15 electrodes of their usual set of 22. The switch off resulted in deteriorating speech understanding over time. Therefore, all subjects were reimplanted with a Nucleus 24R device with a Contour electrode. Preoperatively, the threshold of FN stimulation was obtained on all electrodes subjectively. Intraoperatively, FN stimulation thresholds were measured objectively with both, the old and the new device and were compared. NRT and SRT thresholds were also obtained with the reimplanted device to assure effective electrical stimulation of the auditory nerve. Results: In all four cases the postoperative fitting demonstrated no FN stimulation on all electrodes up to maximum comfortable level. The insertion of the Contour electrode array was complete in three cases, in one case the array could only be inserted partially similarly to the situation before the reimplantation. Speech perception tests showed a significant improvement in all subjects with the new device. Conclusion: Electrodes with modiolar facing contacts and perimodiolar position like the Nucleus Contour electrode reduce the possibility of facial nerve stimulation significantly due to more focused electrical stimulation.

Multícentric Field Evaluation of a New Speech Coding Strategy for Cochlear Implants

In a multicentric study involving 4 European cochlear implant centers, the speech perception abilities of 20 native German-speaking individuals implanted with the Nucleus 22 Channel Cochlear Implant System when using a new spectral peak (SPEAK) speech coding strategy were investigated. This strategy continuously analyzes the speech signal using 20 digital programmable bandpass filters and presents up to 10 spectral maxima to the 22 implanted electrodes. Each subjects performance on a variety of auditory perceptual tasks was evaluated with the experimental encoder (SPEAK), relative to his or her performance in a reference condition. An ABAB experimental design was used whereby each strategy was reversed and replicated. The reference levels of auditory performance were established using the multipeak (MPEAK) speech-processing strategy of the Nucleus speech processor. Only subjects who achieved open-set monosyllable word recognition in the reference condition were included in this study. Significant differences in group mean scores for most speech recognition subtests were obtained for the SPEAK versus the MPEAK strategy. The largest overall improvements were observed for the sentence tests under noisy conditions.

Performance and preference for ACE stimulation rates obtained with nucleus RP 8 and freedom system.

Cochlear recently released the Nucleus® Freedom™ System which has been based on the Nucleus® Research Platform 8. Both systems make use of the same implant, the CI24RE, which includes expanded total stimulation rates up to 32 kHz. In this study the performance of the ACE strategy at 500, 1200 and 3500 pps/channel was investigated using an ABC-CBA design. At the end of each period speech tests were performed. In the CBA phase the patients completed a comparative questionnaire to determine the subjective rate preference. Preliminary results in 13 recipients indicate no differences in for the ACE strategy at rates ranging from 500 pps to 3500 pps/channel.

Evaluation of Advanced Bionics high resolution mode

The objective of this paper is to evaluate the advantages of the Advanced Bionic high resolution mode for speech perception, through a retrospective analysis. Forty-five adult subjects were selected who had a minimum experience of three months’ standard mode (mean of 10 months) before switching to high resolution mode. Speech perception was tested in standard mode immediately before fitting with high resolution mode, and again after a maximum of six months high resolution mode usage (mean of two months). A significant improvement was found, between 11 and 17%, depending on the test material. The standard mode preference does not give any indication about the improvement when switching to high resolution. Users who are converted within any study achieve a higher performance improvement than those converted in the clinical routine. This analysis proves the significant benefits of high resolution mode for users, and also indicates the need for guidelines for individual optimization of parameter settings in a high resolution mode program. Sumario El objetivo de este trabajo fue el de evaluar las ventajas del modo de alta resolución del Advanced Bionics en la percepción del lenguaje, a través de un análisis retrospectivo. Se seleccionaron 45 adultos con una experiencia mínima en el uso del modo estándar por tres meses (media de 10 meses) antes de activar el modo de alta resolución. Se evaluó la percepción del lenguaje en el modo estándar inmediatamente antes del uso del modo de alta resolución y de nuevo, después de un máximo de seis meses de experiencia con éste último modo (media de 2 meses). Se encontró una mejoría significativa entre el 11 y el 17%, dependiendo del material de prueba. La preferencia por el modo estándar no dio ninguna indicación acerca de la mejoría al cambiar al modo de alta resolución. Los usuarios que cambiaron sin ningún estudio, lograron un rendimiento más alto que aquellos que cambiaron en la rutina clínica. Este análisis prueba el beneficio significativo para los usuarios del modo de alta resolución e indica también la necesidad de guías para la optimización individual en el control de los parámetros del programa de modo de alta resolución.

A psychophysical forward masking comparison of longitudinal spread of neural excitation in the Contour™ and straight Nucleus® electrode arrays

The objective of the study was to compare the widths of forward masking profiles in subjects implanted with the Nucleus® 24 Contour™ or straight electrode array. The Contour array is typically positioned closer to the modiolus than the straight array. Subjects were fourteen postlingually hearing-impaired adults with severe-profound hearing loss, seven used the Contour array and seven used the straight array. Forward masking profiles were measured at three positions along the array (apical, mid, and basal) using maskers at the 15% loudness level. It was hypothesized that masking profile widths would be more sensitive to differences in distance from the neural structures using low-level maskers. Masking width was calculated at the 50% point of the masking peak amplitude. There were no significant differences in masking widths between Contour and straight array subject groups. Current levels for hearing thresholds and maximum comfortable listening levels were significantly lower for the Contour array subjects.

Results from a psychoacoustic model-based strategy for the nucleus-24 and freedom cochlear implants.

Objective: In normal-hearing listeners acoustic masking occurs depending on frequency, amplitude, and energy of specific signals. If the selection of stimulated channels in cochlear implant systems was based on psychoacoustic masking models, the bandwidth of the electrode/nerve interface could be used more effectively by concentrating on relevant signal components and neglecting those that are usually not perceived by normal hearing listeners. Subsequently, a new strategy called PACE (Psychoacoustic Advanced Combination Encoder) has been developed which uses a psychoacoustic model for the channel selection instead of the simple maxima selection algorithm of the ACE strategy. Study Design: Only subjects having at least 2 years experience with the ACE strategy were included. A counterbalanced cross-over design was used to compare the new speech coding strategy with the ACE strategy. Setting: The investigation was a prospective, within-subject, repeated-measures experiment. Patients: The study group consisted of 10 postlingually deafened adult subjects. Interventions: The following programs were evaluated: (1) ACE with 8 maxima selected; (2) PACE with 8 channels selected; and (3) PACE with 4 channels selected. Main Outcome Measures: Speech perception tests in quiet and noise, Quality Assessment Questionnaire. Results: Results indicate a trend towards better performance with PACE. Scores in the Freiburg monosyllabic word test increased by 8% while the SNR50 in the Oldenburger sentence test improved significantly by 1.3 dB. Conclusion: The use of psychoacoustic masking models in speech coding strategies has the potential to improve speech perception performance in cochlear implant subjects.

Performance benefits for adults using a cochlear implant with adaptive dynamic range optimization (ADRO): a comparative study

Abstract The aim of this study was to assess the qualitative and quantitative benefits for speech-recognition ability of a preprocessing strategy known as adaptive dynamic range optimization (ADRO), used in conjunction with the subjects standard MAP, in comparison with the subjects standard MAP alone, for a group of experienced Germanspeaking adults using the Nucleus® 24 Cochlear implant. In a prospective, single-subject, comparative study design, experienced adult CI-users were asked to trial and compare both their standard MAP and the newly fitted ADRO MAP (ADRO MAP fitting – week 0) following a take-home trial period of 5 weeks. Assessment of speech recognition ability performed in quiet (at 50, 60 and 70 dB SPL) and adaptively in noise was carried out repeatedly in two test sessions in weeks 5 and 7 (ADRO MAP postfitting) using both MAPs. The order of speech tests and MAPs tested was counterbalanced across the test sessions to control for potential learning effects during the study. Subjective assessments were performed at week 0 to assess details of current usage. Comparative subjective assessments were carried out at weeks 5 and 7 to obtain impressions of loudness of environmental sounds and speech understanding in a variety of conversational situations with both MAPs and finally MAP preference judgements. Fifteen adult, German-speaking, experienced implant users wearing their body-worn SPrint processor for a minimum of six hours and up to 16 hours per day were enrolled in the study across three university clinic hospitals in Germany. On average, speech-reception thresholds (SRT) were significantly improved with the ADRO MAP compared to using the standard MAP for all speech materials in quiet. The mean advantage for SRT values with the ADRO MAP was 2.9 dB, σ ± 2.8 dB (p = 0.002) for the Freiburger Numbers test and 3.3 dB, σ ± 3.2 dB (p = 0.008) for the Freiburger Monosyllabic Words test. In noise, the ADRO MAP led to a significant improvement for the group for the mean signal-to-noise ratio required for a 50% speech recognition score (SNR 50) for the Oldenburger sentences of 1.74 dB, σ ± 3.2 dB (p = 0.048). Comparison of subjective impressions of loudness of environmental sounds revealed no significant difference in the ratings observed with either MAP. For speech understanding in a variety of listening situations, 35% of subjects preferred the ADRO MAP, 29% preferred the standard MAP whereas 36% reported no difference. Statistically the MAP preferences for the groups were not significant, however a significant MAP preference was noted in four subjects for the ADRO MAP and in two subjects for the standard MAP. Our study results demonstrate significant benefits of ADRO for speech recognition ability in quiet and in noise for both soft and conversational levels of speech. For the majority of subjects, both the ADRO and standard MAPs were found to be useful on a daily basis. No reductions in performance were noted for speech recognition or loudness scaling judgements of environmental sounds when using the newly fitted ADRO MAP, suggesting a smooth transition to the use of the preprocessing algorithm. It is recommended that an ADRO MAP be provided for all CI users as an additional program option to offer potential added benefit in select environments. Copyright

A high rate n-of-m speech processing strategy for the first generation Clarion cochlear implant

Abstract An n-of-m speech coding strategy has been developed for the Clarion Cochlear Implant Series 1.x (1.0 & 1.2). The basic principle is to reduce the number of stimuli per cycle, by neglecting the less significant spectral components, and to concentrate on the more dominant frequency bands. In this study 20 subjects, implanted with a Clarion device, used an n-of-m strategy at 1666 pps per channel. The outcomes using this strategy were compared with the outcomes using conventional processing (CIS at 833 pps/channel). Eight of the 20 subjects underwent additional testing with the n-of-m strategy with the rate set at 833 pps/channel. Using the n-of-m strategy at 1666 pps showed statistically significant improvement in performance over the CIS strategy, with 16 of the 20 subjects achieving better results. However, there was no statistically meaningful difference in performance between n-of-m at 833 pps and the CIS strategy running at the same rate. Results therefore suggest that n-of-m strategy can be an alternative to CIS, particularly when the implant hardware limits the overall stimulation rate. Sumario Se ha desarrollado una estrategia n-of-m de codificación del lenguaje para el implante coclear Clarion en sus series 1 × (1.0 & 1.2). El principio básico es reducir el número de estímulos por ciclo, abandonando los componentes espectrales menos significativos y concentrándose en las bandas de frecuencia más dominantes. En este estudio 20 sujetos implantados con un Clarion, usaron una estrategia n-of-m a 1666 pps por canal. Los resultados con el uso de esta estrategia se compararon con los obtenidos al usar procesamiento convencional (CIS a 833 pps/ canal).Ocho de los 20 sujetos realizaron pruebas adicionales con la estrategia n-of-m a una tasa de 833 pps/canal. El uso de la estrategia n-of-m a 1666 pps mostró una mejoría estadísticamente significativa en el rendimiento, en comparación con la estrategia CIS, en 16 de los 20 sujetos que obtuvieron mejores resultados. No obstante, no hubo una diferencia estadísticamente significativa en el rendimiento entre la condición de 833 pps y la estrategia CIS, practicadas a la misma tasa. Los resultados sugieren por consiguiente que la estrategia n-of-m puede ser una alternativa de la CIS, particularmente cuando el equipo limita la tasa total de estimulación.