Exploring the clinical approach to the bimodal fitting of hearing aids and cochlear implants: results of an international survey.

CONCLUSIONS: The results show that the fitting of a contralateral hearing aid (HA) in the non-implanted ear of cochlear implant (CI) recipients is now well established as standard clinical practice. However, there is a lack of experience in HA fitting within the CI centres and the use of published bimodal fitting procedures is poor. The HA is often not refitted after CI switch-on and this may contribute to rejection. Including a bimodal fitting prescription and process in the CI fitting software would make applying a balancing procedure easier and may increase its implementation in routine clinical practice. OBJECTIVE: This survey was designed to investigate and understand the current approach to bimodal fitting of HAs and CIs across different countries and the recommendations made to recipients. METHODS: Clinicians working with HAs and/or CIs were invited to participate in an international multicentre clinical survey, designed to obtain information on the various approaches towards bimodal hearing and CI and HA device fitting. Forty-one questions were presented to clinicians in experienced CI centres across a range of countries and answers were collected via an online survey. RESULTS: In all, 65 responses were obtained from 12 different countries. All clinicians said they would advise a CI user to wear a contralateral HA if indicated. However, a significant number (45%) had either never fitted HAs before or had less than 1 year of experience. In general, there were no specific criteria for selecting candidates to fit with an HA. A strategy to balance the HA with the CI was not used as a standard practice for any of the adults and was used in only 12% of the children. Only half the respondents were aware of the bimodal literature. The majority of professionals (18/30) did not refit the HA after CI switch-on. However, if users complained of sound quality or loudness issues or had poor test results, a follow-up session was provided. The main benefit reported by recipients was improvement in overall sound quality.

Measures of the electrically evoked compound action potential threshold and slope in HiRes 90K(TM) users.

OBJECTIVES: To investigate electrically evoked compound action potentials (eCAPs) measured with the neural response imaging (NRI) 'SmartNRI' algorithm. NRI thresholds and slopes were examined according to three aspects: (1) site along the cochlea, (2) development of responses over time, and (3) influence of age/duration of deafness. METHODS: Thirty-four individuals implanted with the Advanced Bionics HiRes 90K(TM) device were included. The eCAP recordings were made from four electrodes along the array at first fitting and at frequent intervals up to at least 2 years. Slope and threshold (tNRI) of the amplitude growth function were measured and a range of explanatory variables were tested for significant effects on these measures using multi-factorial analysis of variance. RESULTS: Electrode position emerged as a significant effect for the tNRI measure, with lowest thresholds at the apical end of the array. Mean slope was greatest for the most apical electrode, but not significantly. Slope was significantly influenced by onset of deafness, with congenital hearing loss associated with steeper slopes than acquired hearing loss. There was also a highly significant effect of duration of device use, with a gradual increase in slope over the 2 years following device activation. DISCUSSION: The observed effects of electrode position are consistent with a model in which eCAP threshold is governed primarily by an effect of distance between electrode and neural interface (which is shorter towards the apex of the cochlea) and in which slope is governed primarily by density of surviving neural elements.

Results of a multicenter clinical study evaluating a new Smart algorithm to measure neural response imaging.

OBJECTIVE: To evaluate the smart algorithm in speed and reliability of threshold estimation compared with the algorithm available in the standard fitting software and to evaluate the possibility of using programs based on the smart algorithm instead of programs derived from behavioral measures. PATIENTS: Twenty subjects unilaterally implanted with a CII Bionic Ear or HiRes90K device. INTERVENTIONS: Neural response imaging thresholds (tNRI) were measured using both the smart approach within the Research Studies Platform for Objective Measures and the SoundWave fitting software. Measurements were performed intraoperatively, at first fitting, and after 3 months of implant use. Each subject received a standard behavioral program and a SmartNRI program. Speech perception tests were conducted at 3 months, and subjective preferences were documented. MAIN OUTCOME MEASURES: Smart tNRI and SoundWave tNRI at each session; speech test results and subject preferences at the 3-month session. RESULTS: High correlations were found between smart tNRI and SoundWave tNRI. The time required to obtain NRI thresholds with the smart algorithm was a quarter of the time needed with SoundWave. Although most tested subjects preferred their behavioral programs, there were no significant differences in performance between SmartNRI and behavioral programs. CONCLUSION: Neural response imaging thresholds were obtained more rapidly with the smart algorithm than with SoundWave. Because no differences were observed between SmartNRI and behavioral programs, SmartNRI programs may be a useful alternative to behavioral programs in difficult to fit cases, where user feedback is sometimes difficult to obtain.

Multicentre investigation on electrically evoked compound action potential and stapedius reflex: how do these objective measures relate to implant programming parameters?

OBJECTIVES: The aims of this study were to collect data on electrically evoked compound action potential (eCAP) and electrically evoked stapedius reflex thresholds (eSRT) in HiResolution(TM) cochlear implant (CI) users, and to explore the relationships between these objective measures and behavioural measures of comfort levels (M-levels). METHODS: A prospective study on newly implanted subjects was designed. The eCAP was measured intra-operatively and at first fitting through neural response imaging (NRI), using the SoundWave(TM) fitting software. The eSRT was measured intra-operatively by visual monitoring of the stapes, using both single-electrode stimulation and speech bursts (four electrodes stimulated at the same time). Measures of M-levels were performed according to standard clinical practice and collected at first fitting, 3 and 6 months of CI use. RESULTS: One hundred seventeen subjects from 14 centres, all implanted unilaterally with a HiResolution CII Bionic Ear(®) or HiRes 90K(®), were included in the study. Speech burst stimulation elicited a significantly higher eSRT success rate than single-electrode stimulation, 84 vs. 64% respectively. The NRI success rate was 81% intra-operatively, significantly increasing to 96% after 6 months. Fitting guidelines were defined on the basis of a single NRI measurement. Correlations, analysis of variance, and multiple regression analysis were applied to generate a predictive model for the M-levels. DISCUSSION: Useful insights were produced into the behaviour of objective measures according to time, electrode location, and fitting parameters. They may usefully assist in programming the CI when no reliable feedback is obtained through standard behavioural procedures.

Benefits of the HiRes 120 coding strategy combined with the Harmony processor in an adult European multicentre study.

CONCLUSION: The Harmony processor was found to be reliable, comfortable and offered a substantially increased battery life compared with the previous generation processor. No significant improvement in speech understanding with HiRes was demonstrated from objective measures, but the majority of subjects showed a clear subjective preference for the combination HiRes 120/Harmony processor. OBJECTIVES: To evaluate experience with the Harmony™ sound processor, together with the HiRes 120 strategy. METHODS: Postlingually deafened adults implanted with a CII or HiRes 90K were included and divided into three groups: (1) experienced users using the Platinum body-worn processor; (2) experienced users who had been using other processors; (3) new users with the Harmony processor from first fitting. The latter group entered a randomized crossover protocol where half were initially fitted with HiRes and half with HiRes 120. The initial strategy was used for 3 months and the alternative for a further 3 months. Speech perception tests and questionnaires were performed. RESULTS: The study included 65 subjects. Implementing HiRes 120 was straightforward. The speech test group results did not show significant differences between HiRes and HiRes 120. However, the questionnaires showed significantly higher ratings for HiRes 120 in some instances. Subjects were highly satisfied with the Harmony processor.

One-year results of the banded neural response imaging study.

OBJECTIVE: To investigate the relationship between single-channel and banded neural response imaging (NRI) responses and to evaluate whether banded NRI measurements are better correlated to fitting parameters than single-channel NRI measurements. PATIENTS: Nineteen profoundly deaf subjects implanted with a HiRes 90K cochlear implant from Advanced Bionics Corporation (Valencia, CA). INTERVENTION(S): Neural response imaging thresholds (tNRIs; single-channel and banded tNRIs) were measured intraoperatively; at first fitting; and after 3, 6, and 12 months of implant use. Relationships between those measurements and correlations between those measurements and implant program parameters were investigated. MAIN OUTCOME MEASURE(S): Single-channel and banded tNRI collected at each measurement session. RESULTS: Banded NRI could be recorded reliably and was not more time-consuming than the routine single-channel NRI. Significant correlations (Pearson R; p < 0.05) were observed between first-fitting banded tNRI and most comfortable levels at 12 months, with a higher level of significance than the correlations observed with single-channel tNRI. CONCLUSION: Banded NRI may be a more appropriate fitting tool than single-channel NRI. However, the sample size was small, and more data are necessary to confirm these findings.

Evidence of a tonotopic organization of the auditory cortex in cochlear implant users.

Deprivation from normal sensory input has been shown to alter tonotopic organization of the human auditory cortex. In this context, cochlear implant subjects provide an interesting model in that profound deafness is made partially reversible by the cochlear implant. In restoring afferent activity, cochlear implantation may also reverse some of the central changes related to deafness. The purpose of the present study was to address whether the auditory cortex of cochlear implant subjects is tonotopically organized. The subjects were thirteen adults with at least 3 months of cochlear implant experience. Auditory event-related potentials were recorded in response to electrical stimulation delivered at different intracochlear electrodes. Topographic analysis of the auditory N1 component (approximately 85 ms latency) showed that the locations on the scalp and the relative amplitudes of the positive/negative extrema differ according to the stimulated electrode, suggesting that distinct sets of neural sources are activated. Dipole modeling confirmed electrode-dependent orientations of these sources in temporal areas, which can be explained by nearby, but distinct sites of activation in the auditory cortex. Although the cortical organization in cochlear implant users is similar to the tonotopy found in normal-hearing subjects, some differences exist. Nevertheless, a correlation was found between the N1 peak amplitude indexing cortical tonotopy and the values given by the subjects for a pitch scaling task. Hence, the pattern of N1 variation likely reflects how frequencies are coded in the brain.

Effects of auditory pathway anatomy and deafness characteristics? Part 2: On electrically evoked late auditory responses.

The purpose of this study was to distinguish the effects of different parameters on latencies of wave N1, wave P2, and inter-peak interval N1-P2 of electrical late auditory responses (ELARs). ELARs were recorded from four intra-cochlear electrodes in fourteen adult HiRes90K cochlear implant users who had at least three months of experience. The relationship between latencies and stimulation sites in the cochlea was characterized to assess the influence of the auditory pathway anatomy on ELARs, i.e., whether the speed of neural propagation varies according to the place that is activated in the cochlea. Audiograms before implantation, duration of deafness, and psychophysics at first fitting were used to describe the influence of deafness characteristics on latencies. The stimulation sites were found to have no effect on ELAR latency and, while there was no influence of psychophysics on latency, a strong relationship was shown with duration of deafness and the pre-implantation audiogram. Thus, ELAR latency was longer for poorer audiograms and longer durations of deafness and this relationship appeared to be independent of stimulation parameters such as stimulation site. Comparison between these findings and those from the equivalent study on EABR waves IIIe and Ve latency [Guiraud, J., Gallego, S., Arnold, L., Boyle, P., Truy, E., Collet, L., 2007. Effects of auditory pathway anatomy and deafness characteristics? (1): On electrically evoked auditory brainstem responses. Hear. Res. 223 (1-2), 48-60] shows that, while ELAR and EABR latencies are related with parameters that reflect the integrity of the auditory pathway, ELAR latency is less dependent on stimulation parameters than EABR latency.

Effects of auditory pathway anatomy and deafness characteristics? (1): On electrically evoked auditory brainstem responses.

The purpose of this study was to distinguish the effects of different parameters on latencies of wave IIIe, wave Ve, and interpeak interval IIIe-Ve of electrical auditory brainstem responses (EABRs). EABRs were recorded from all the intra-cochlear electrodes in eight adult HiRes90K((R)) cochlear implant users. The relationship between latencies and stimulation sites in the cochlea was characterized to assess activity along the auditory pathway. Audiograms before implantation, psychophysics at first fitting and duration of deafness were used to describe the influence of deafness on latencies. A decreasing baso-apical latency gradient was found for waves IIIe and Ve, while the interpeak interval IIIe-Ve remained the same along the electrode array. Electrical stimulation enabling to stimulate various parts of the cochlea at the same time, this could indicate an anatomical way of compensating for the delay the acoustic wave takes to reach the cochlea apex in a non-implanted ear. However, psychophysical levels were also found to increase at the cochlear base showing that the latency gradient could result from an increasing gradient of neural degeneration toward the base. Correlations of EABR latencies with psychophysics, audiometric data and duration of deafness show that factors linked to deafness have indeed an influence on EABR latencies. The possible explanations for the latency shift observed, whether they are anatomical and/or pathological, are exposed.