Andreas Buechner

Hearing Conservation Surgery Using the Hybrid-L Electrode

Patients with high-frequency deafness and/or substantial residual hearing across frequencies might benefit from combined electro-acoustic stimulation. The Hybrid-L electrode was designed to address the issues of both hearing conservation and effective electrical stimulation in those recipients. The electrode with 22 contacts should be inserted through the round window membrane, and covers approximately 270° of the basal turn of the cochlear. This insertion length is equivalent to the one seen in many patients using the former Nucleus straight electrode. Twenty-four patients with low-frequency thresholds of 60 dB or better, up to 500 Hz, were implanted with a Hybrid-L device in a clinical trial at the Medical University of Hannover. Another group of 8 recipients with less residual hearing was included under extended inclusion criteria. Residual hearing was conserved in the majority of cases. One patient had a loss of more than 30 dB, but hearing partially recovered after 9 months. The median loss in all patients was 10 dB in both the Hybrid group and the extended group. Patients were able to use the residual hearing postoperatively to the same extent as preoperatively. In the Hybrid mode (cochlear implant + ipsilateral hearing aid), patients showed a significant improvement of 21% (p = 0.002) in speech understanding in quiet using the Freiburger Monosyllabic Word Test compared to the preoperative scores under aided conditions with their hearing aid. The Oldenburg Sentence Test in noise showed a remarkable average improvement of 10.2 dB (p < 0.001) compared to the preoperative hearing aid only mode. An additional improvement could be seen in the combined mode using an additional contralateral hearing aid. Recipients with a shorter duration of high-frequency hearing loss showed a larger benefit than those with a longer duration of hearing loss. Hearing conservation using the Hybrid-L electrode and a given surgical technique is possible with high probability in patients with high-frequency deafness or pantonal hearing loss. The use of the residual acoustic hearing offers specific advantages, especially for understanding speech in noise and for spatial hearing.

Temporal Bone Results and Hearing Preservation with a New Straight Electrode

Due to improved technology, cochlear implant (CI) candidacy has been widened towards patients with usable residual hearing in the low frequency range. These patients might benefit from additional acoustic amplification provided that residual hearing can be preserved with cochlear implantation. To provide a high probability of hearing preservation, a new electrode array was designed and developed at the Medizinische Hochschule Hannover. This ‘Hybrid-L’ electrode array has 22 electrodes spread over 15 mm with an overall insertion depth of 16 mm. The straight electrode with modiolus facing contacts is designed for a round window insertion. It shall provide the full range of the currently most advanced Nucleus CI system. A temporal bone study demonstrated the favorable insertion characteristics and minimized trauma to intracochlear structures. Compared to standard CI electrodes especially no basilar membrane perforation could be found. So far, 4 patients have been implanted and residual hearing could be preserved. One patient was fitted and showed a marked additional benefit from the electroacoustic stimulation compared to either acoustic or electrical stimulation alone. These results are very encouraging towards a concept of reliable hearing preservation with cochlear implantation.

Cochlear Implantation in Unilateral Deaf Subjects Associated With Ipsilateral Tinnitus

Objective: In subjects who are deaf and who also have tinnitus in the affected ear, tinnitus treatments based on acoustic input are impossible. On the other hand, tinnitus suppression using electric stimulation has been reported to be successful. Therefore, a study was initiated to investigate the potential of cochlear implantation (CI) in unilateral deaf subjects regarding tinnitus suppression, device acceptance, and restoration of spatial hearing. Method: Five subjects with severe to profound unilateral deafness having also ipsilateral tinnitus were enrolled. In monthly visits, the speech processor program was optimized, and the hearing performance as well as tinnitus were monitored. In addition, it was investigated whether the CI improves hearing in adverse listening situations when combined with the normal hearing side. Results: In 3 participants, the tinnitus was significantly suppressed while wearing the device. In the other 2 participants, the tinnitus could be reduced in certain situations. Speech perception tests revealed a significant benefit with the CI in combination with the normal-hearing side for 3 participants. All participants accepted the device in a clinical setting; adaptation of the frequency allocation was not required. Conclusion: Improvements were found regarding the hearing and the tinnitus. Not all participants benefit from the CI to the same degree and in the same situations. The results indicate that cochlear implantation in subjects with unilateral severe to profound hearing loss and ipsilateral tinnitus may be beneficial on a case-to-case basis. Further work needs to be performed to define the appropriate indication criteria.

Performance groups in adult cochlear implant users: speech perception results from 1984 until today.

Introduction: More than 3,000 patients have received a cochlear implant in Hannover. Methods: A group of 864 patients was selected from the main group for the analysis of speech perception development. Depending on the term of introduction of new implant technology, the viewed group was divided into 5 subgroups. Results: The test battery during regular clinical checkups included speech perception tests. Those tests changed during 20 years; only speech tracking and monosyllable word test remained and were the bases for forming performance classes shown in this study. Three performance classes can be specified for all 5 subgroups by mean values and standard deviations. Conclusion: In all subgroups, an improvement of speech perception can be observed over time. The current patient group showed significant better performing results than those of the first group.

Advanced beamformers for cochlear implant users: acute measurement of speech perception in challenging listening conditions.

Objective To investigate the performance of monaural and binaural beamforming technology with an additional noise reduction algorithm, in cochlear implant recipients. Method This experimental study was conducted as a single subject repeated measures design within a large German cochlear implant centre. Twelve experienced users of an Advanced Bionics HiRes90K or CII implant with a Harmony speech processor were enrolled. The cochlear implant processor of each subject was connected to one of two bilaterally placed state-of-the-art hearing aids (Phonak Ambra) providing three alternative directional processing options: an omnidirectional setting, an adaptive monaural beamformer, and a binaural beamformer. A further noise reduction algorithm (ClearVoice) was applied to the signal on the cochlear implant processor itself. The speech signal was presented from 0° and speech shaped noise presented from loudspeakers placed at ±70°, ±135° and 180°. The Oldenburg sentence test was used to determine the signal-to-noise ratio at which subjects scored 50% correct. Results Both the adaptive and binaural beamformer were significantly better than the omnidirectional condition (5.3 dB±1.2 dB and 7.1 dB±1.6 dB (p<0.001) respectively). The best score was achieved with the binaural beamformer in combination with the ClearVoice noise reduction algorithm, with a significant improvement in SRT of 7.9 dB±2.4 dB (p<0.001) over the omnidirectional alone condition. Conclusions The study showed that the binaural beamformer implemented in the Phonak Ambra hearing aid could be used in conjunction with a Harmony speech processor to produce substantial average improvements in SRT of 7.1 dB. The monaural, adaptive beamformer provided an averaged SRT improvement of 5.3 dB.

Results of a pilot study with a signal enhancement algorithm for HiRes 120 cochlear implant users.

Objective: Cochlear implant users still experience severe limitations regarding sound quality, music appreciation, and speech perception in adverse listening situation. To improve hearing in noisy environments, the incorporation of signal enhancement algorithms was initiated. Method: The study group consisted of 13 postlingually deafened adults using HiRes 120. Participants were fitted with 2 versions of the noise reduction algorithm: a moderate and a strong setting. In an immediate session, the HSM sentence test in speech-shaped noise was administered using the clinical program as well as both noise reduction programs. Participants were asked to try all 3 programs in everyday listening situations at home and provide a rating of sound quality and speech perception via a questionnaire (Abbreviated Profile of Hearing Aid Benefit). Results: During the fitting, no difficulties were encountered, and all participants accepted the noise reduction programs without any acclimatization. All participants achieved better results with both noise reduction programs in the HSM sentence test in noise compared with the clinical program. Group mean speech perception scores were highly significantly better for the ClearVoice settings compared with the clinical program score. The majority preferred one of the ClearVoice conditions, with 4 participants for the strong and 3 for the moderate setting. Conclusion: Our results demonstrate a real potential benefit for noise reduction algorithms in cochlear implant processors. Although algorithm parameters were not optimized individually, a significant improvement could still be achieved. Further investigation is required to develop fitting guidelines and achieve parameter optimization.

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 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.

Clinical evaluation of cochlear implant sound coding taking into account conjectural masking functions, MP3000™

Abstract Efficacy of the SPEAK and ACE coding strategies was compared with that of a new strategy, MP3000™, by 37 European implant centers including 221 subjects. The SPEAK and ACE strategies are based on selection of 8–10 spectral components with the highest levels, while MP3000 is based on the selection of only 4–6 components, with the highest levels relative to an estimate of the spread of masking. The pulse rate per component was fixed. No significant difference was found for the speech scores and for coding preference between the SPEAK/ACE and MP3000 strategies. Battery life was 24% longer for the MP3000 strategy. With MP3000 the best results were found for a selection of six components. In addition, the best results were found for a masking function with a low-frequency slope of 50 dB/Bark and a high-frequency slope of 37 dB/Bark (50/37) as compared to the other combinations examined of 40/30 and 20/15 dB/Bark. The best results found for the steepest slopes do not seem to agree with current estimates of the spread of masking in electrical stimulation. Future research might reveal if performance with respect to SPEAK/ACE can be enhanced by increasing the number of channels in MP3000 beyond 4–6 and it should shed more light on the optimum steepness of the slopes of the masking functions applied in MP3000.

Deeper Cochlear Implant Electrode Insertion Angle Improves Detection of Musical Sound Quality Deterioration Related to Bass Frequency Removal.

Background: Cochlear implant (CI) electrode arrays typically do not reach the most apical regions of the cochlea that intrinsically encode low frequencies. This may contribute to diminished implant-mediated musical sound quality perception. The objective of this study was to assess the effect of varying degrees of apical cochlear stimulation (measured by angular insertion depth) on musical sound quality discrimination. Hypothesis: Increased apical cochlear stimulation will improve low-frequency perception and musical sound quality discrimination. Methods: Standard (31.5 mm, n = 17) and medium (24 mm, n = 8) array Med-EL CI users, and normal hearing (NH) listeners (n = 16) participated. Imaging confirmed angular insertion depth. Participants completed a musical discrimination task in which they listened to a real-world musical stimulus (labeled reference) and provided sound quality ratings to versions of the reference, which included a hidden reference and test stimuli with increasing amounts of low-frequency removal. Scores for each CI users were calculated on the basis of how much their ratings differed from NH listeners for each stimulus version. Results: Medium array and standard users had significantly different insertion depths (389.4±64.5 and 583.9 ± 78.5 degrees, respectively; p < 0.001). A significant Pearsons correlation was observed between angular insertion depth and the hidden reference scores (p < 0.05). Conclusion: CI users with greater apical stimulation made sound quality discriminations that more closely resembled those of NH controls for stimuli that contained low frequencies (<200 Hz of information). These findings suggest that increased apical cochlear stimulation improves musical low-frequency perception, which may provide a more satisfactory music listening experience for CI users.