The Cost-Effectiveness of Bimodal Stimulation Compared to Unilateral and Bilateral Cochlear Implant Use in Adults with Bilateral Severe to Profound Deafness.

OBJECTIVES: An increasing number of severe-profoundly deaf adult unilateral cochlear implant (CI) users receive bimodal stimulation; that is, they use a conventional acoustic hearing aid (HA) in their nonimplanted ear. The combination of electric and contralateral acoustic hearing provides additional benefits to hearing and also to general health-related quality of life compared with unilateral CI use. Bilateral CI is a treatment alternative to both unilateral CI and bimodal stimulation in some healthcare systems. The objective of this study was to conduct an economic evaluation of bimodal stimulation compared with other management options for adults with bilateral severe to profound deafness. DESIGN: The economic evaluation took the form of a cost-utility analysis and compared bimodal stimulation (CI+HA) to two treatment alternatives: unilateral and bilateral CI. The analysis used a public healthcare system perspective based on data from the United Kingdom and the United States. Costs and health benefits were identified for both alternatives and estimated across a patient's lifetime using Markov state transition models. Utilities were based on Health Utilities Index estimates, and health outcomes were expressed in Quality Adjusted Life Years (QALYs). The results were presented using the Incremental Cost-Effectiveness Ratio and the Net Monetary Benefit approach to determine the cost-effectiveness of bimodal stimulation. Probabilistic sensitivity analyses explored the degree of overall uncertainty using Monte Carlo simulation. Deterministic sensitivity analyses and analysis of covariance identified parameters to which the model was most sensitive; that is, whose values had a strong influence on the intervention that was determined to be most cost-effective. A value of information analysis was performed to determine the potential value to be gained from additional research on bimodal stimulation. RESULTS: The base case model showed that bimodal stimulation was the most cost-effective treatment option with a decision certainty of 72 and 67% in the United Kingdom and United States, respectively. Despite producing more QALYs than either unilateral CI or bimodal stimulation, bilateral CI was found not to be cost-effective because it was associated with excessive costs. Compared with unilateral CI, the increased costs of bimodal stimulation were outweighed by the gain in quality of life. Bimodal stimulation was found to cost an extra £174 per person in the United Kingdom ($937 in the US) and yielded an additional 0.114 QALYs compared with unilateral CI, resulting in an Incremental Cost-Effectiveness Ratio of £1521 per QALY gained in the United Kingdom ($8192/QALY in the United States). The most influential variable was the utility gained from the simultaneous use of both devices (CI+HA) compared with Unilateral CI. The value of further research was £4,383,922 at £20,000/QALY ($86,955,460 at $50,000/QALY in the United States). CONCLUSIONS: This study provides evidence of the most cost-effective treatment alternative for adults with bilateral severe to profound deafness from publicly funded healthcare perspectives of the United Kingdom and United States. Bimodal stimulation was found to be more cost-effective than unilateral and bilateral CI across a wide range of willingness-to-pay thresholds. If there is scope for future research, conducting interventional designs to obtain utilities for bimodal stimulation compared with unilateral CI would reduce decision uncertainty considerably.

Effects of Tinnitus on Cochlear Implant Programming.

Clinical observations suggest that tinnitus may interfere with programming cochlear implants (CIs), the process of optimizing the transmission of acoustic information to support speech perception with a CI. Despite tinnitus being highly prevalent among CI users, its effects and impact on CI programming are obscure. This study characterized the nature, time-course, and impact of tinnitus effects encountered by audiologists and patients during programming appointments. Semistructured interviews with six CI audiologists were analyzed thematically to identify tinnitus effects on programming and related coping strategies. Cross-sectional surveys with 67 adult CI patients with tinnitus and 20 CI audiologists in the United Kingdom examined the prevalence and time-course of those effects. Programming parameters established at CI activation appointments of 10 patients with tinnitus were compared with those of 10 patients without tinnitus. On average, 80% of audiologists and 45% of patients reported that tinnitus makes measurements of threshold (T) levels more difficult because patients confuse their tinnitus with CI stimulation. Difficulties appeared most common at CI activation appointments, at which T levels were significantly higher in patients with tinnitus. On average, 26% of patients reported being afraid of "loud" CI stimulation worsening tinnitus, affecting measurements of loudest comfortable (C) stimulation levels, and 34% of audiologists reported observing similar effects. Patients and audiologists reported that tinnitus makes programming appointments more difficult and tiresome for patients. The findings suggest that specific programming strategies may be needed during CI programming with tinnitus, but further research is required to assess the potential impact on outcomes including speech perception.

Contralateral acoustic hearing aid use in adult unilateral cochlear implant recipients: Current provision, practice, and clinical experience in the UK.

OBJECTIVES: The study surveyed practising cochlear implant (CI) audiologists with the aim of: (1) characterizing UK clinical practice around the management and fitting of a contralateral hearing aid (HA) in adult unilateral CI users ('bimodal aiding'); (2) identifying factors that may limit the provision of bimodal aiding; and (3) ascertaining the views of audiologists on bimodal aiding. METHODS: An online survey was distributed to audiologists working at the 20 centres providing implantation services to adults in the UK. RESULTS: Responses were received from 19 of the 20 centres. The majority of centres reported evaluating HAs as part of the candidacy assessment for cochlear implantation. However, a majority also indicated that they do not take responsibility for the contralateral HA following implantation, despite identifying few practical limiting factors. Bimodal aiding was viewed as more beneficial than wearing the implant alone, with most respondents actively encouraging bimodal listening where possible. Respondents reported that fitting bimodal devices to take account of each other's settings was potentially more beneficial than independently fit devices, but such sympathetic fitting was not routine practice in any centre. DISCUSSION: The results highlight some potential inconsistencies in the provision of bimodal aiding across the UK as reported by practising audiologists. The views of audiologists about what is best practice appear to be at odds with the nature and structure of the services currently offered. CONCLUSION: Stronger evidence that bimodal aiding can be beneficial for UK patients would be required in order for service providers to justify the routine provision of bimodal aiding and to inform guidelines to shape routine clinical practice.

Choosing which ear to implant in adult candidates with functional residual hearing.

This study examined whether audiologists consider the potential benefits of contralateral hearing aid use following cochlear implantation when recommending which ear to implant in UK adult candidates with residual hearing. Thirty-four audiologists from providers of adult implantation services completed a decision-choice experiment. Clinicians were willing to consider recommending that the poorer ear be implanted, provided it had been aided continuously, suggesting that their decision making seeks to preserve access to residual hearing in the non-implanted ear where possible. Future approaches to determining candidacy should therefore consider that a sub-set of patients may obtain additional benefit from this residual hearing following implantation.

Access to aidable residual hearing in adult candidates for cochlear implantation in the UK.

Guidance from the National Institute for Health and Care Excellence (NICE) permits candidates to receive a cochlear implant provided they only hear sounds louder than 90 dB HL at 2 and 4 kHz. In some patients, their level of residual hearing may be sufficient to warrant the use of a hearing aid in their non-implanted ear. A survey of unilaterally implanted adults indicated that those implanted since the publication of NICE guidance were almost seven times more likely to use a hearing aid than those implanted prior to this. If contralateral hearing aid use provides additional benefits over implant use alone, it may be appropriate to consider the capacity to use residual hearing following implantation when determining candidacy.

The perception of complex pitch in cochlear implants: A comparison of monopolar and tripolar stimulation.

Cochlear implant listeners typically perform poorly in tasks of complex pitch perception (e.g., musical pitch and voice pitch). One explanation is that wide current spread during implant activation creates channel interactions that may interfere with perception of temporal fundamental frequency information contained in the amplitude modulations within channels. Current focusing using a tripolar mode of stimulation has been proposed as a way of reducing channel interactions, minimising spread of excitation and potentially improving place and temporal pitch cues. The present study evaluated the effect of mode in a group of cochlear implant listeners on a pitch ranking task using male and female singing voices separated by either a half or a quarter octave. Results were variable across participants, but on average, pitch ranking was at chance level when the pitches were a quarter octave apart and improved when the difference was a half octave. No advantage was observed for tripolar over monopolar mode at either pitch interval, suggesting that previously published psychophysical advantages for focused modes may not translate into improvements in complex pitch ranking. Evaluation of the spectral centroid of the stimulation pattern, plus a lack of significant difference between male and female voices, suggested that participants may have had difficulty in accessing temporal pitch cues in either mode.

Assessment of 'Fitting to Outcomes Expert' FOX™ with new cochlear implant users in a multi-centre study.

OBJECTIVE: To compare the fitting time requirements and the efficiency in achieving improvements in speech perception during the first 6 months after initial stimulation of computer-assisted fitting with the Fitting to Outcome eXpert' (FOX) and a standard clinical fitting procedure. METHOD: Twenty-seven post-lingually deafened adults, newly implanted recipients of the Advanced Bionics HiRes 90K™ cochlear implant from Germany, the UK, and France took part in a controlled, randomized, clinical study. Speech perception was measured for all participants and fitting times were compared across groups programmed using FOX and conventional programming methods. RESULTS: The fitting time for FOX was significantly reduced at 14 days (P < 0.001) but equivalent over the 6-month period. The groups were not well matched for duration of deafness; therefore, speech perception could not be compared across groups. DISCUSSION: Despite including more objective measures of performance than a standard fitting approach and the adjustment of a greater range of parameters during initial fitting, FOX did not add to the overall fitting time when compared to the conventional approach. FOX significantly reduced the fitting time in the first 2 weeks and by providing a standard fitting protocol, reduced variability across centres. CONCLUSIONS: FOX computer-assisted fitting can be successfully used at switch on, in different clinical environments, reducing fitting time in the first 2 weeks and is efficient at providing a usable program.

Interpulse interval discrimination within and across channels: comparison of monopolar and tripolar mode of stimulation.

Perception of temporal patterns is crucial to speech understanding and music perception in normal hearing, and is fundamental in the design and implementation of processing strategies for cochlear implants. Two experiments described here investigated the effect of stimulation mode (monopolar versus tripolar) on interpulse interval discrimination using single-electrode stimulation (experiment 1) and dual-electrode stimulation (experiment 2). Experiment 1 required participants to discriminate stimuli containing different interpulse intervals and experiment 2 required listeners to discriminate between two dual-electrode stimuli that had the same temporal pattern on each electrode, but differed in inter-electrode timing. The hypotheses were that (i) stimulation mode would affect the ability to distinguish interpulse interval patterns on a single electrode and (ii) the electrode separation range in which subjects were sensitive to inter-electrode timing would be more restricted in tripolar than in monopolar stimulation. Results in nine cochlear implant users showed that mode did not have a significant mean effect on either the ability to discriminate interpulse intervals in single-electrode stimulation or the range of electrode separation in dual-electrode stimulation in which participants were sensitive to inter-electrode timing. In conclusion, tripolar stimulation did not show any advantage in delivering temporal information within or across channels in this group.

Place specificity of monopolar and tripolar stimuli in cochlear implants: the influence of residual masking.

This experiment investigated whether place specificity of neural activity evoked by cochlear implant stimulation is improved in tripolar compared to monopolar mode using a forward masking protocol addressing some limitations of previous methods of measurement and analysis. The amount of residual masking (masking remaining at long masker-probe delays) was also measured, and its potential influence on the specificity measures was evaluated. The masker stimulus comprised equally loud interleaved mono- or tripolar stimulation on two electrodes equidistant from a central probe electrode in an apical and basal direction, reducing the influence of off-site listening. The effect of masker-probe distance on the threshold shift of the tripolar probe was analyzed to derive a measure of place specificity. On average, tripolar maskers were more place specific than monopolar maskers, although the mean effect was small. There was no significant effect of masker level on specificity or on the differences observed between modes. The mean influence of residual masking on normalized masking functions was similar for the two modes and, therefore, did not influence the comparison of specificity between the modes. However, variability in amount of residual masking was observed between subjects, and therefore should be considered in forward masking studies that compare place specificity across subjects.

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.

Evaluation of bilaterally implanted adult subjects with the nucleus 24 cochlear implant system.

OBJECTIVE: To evaluate the speech perception benefits of bilateral implantation for subjects who already have one implant. STUDY DESIGN: Repeated measures. PATIENTS: Thirty adult cochlear implant users who received their second implant from 1 to 7 years with a mean of 3 years after their first device. Ages ranged from 29 to 82 years with a mean of 57 years. SETTING: Tertiary referral centers across the United Kingdom. MAIN OUTCOME MEASURES: Monosyllabic consonant-nucleus-consonant words and City University of New York sentences in quiet with coincident speech and noise and with the noise spatially separated from the speech by +/-90 degrees . RESULTS: At 9 months, results showed the second ear in noise was 13.9 +/- 5.9% worse than the first ear (p < 0.001); a significant binaural advantage of 12.6 +/- 5.4% (p < 0.001) over the first ear alone for speech and noise from the front; a 21 +/- 6% (p < 0.001) binaural advantage over the first ear alone when noise was ipsilateral to the first ear; no binaural advantage when noise was contralateral to the first ear. CONCLUSIONS: There is a significant bilateral advantage of adding a second ear for this group. We were unable to predict when the second ear would be the better performing ear, and by implanting both ears, we guarantee implanting the better ear. Sequential implantation with long delays between ears has resulted in poor second ear performance for some subjects and has limited the degree of bilateral benefit that can be obtained by these users. The dual microphone does not provide equivalent benefit to bilateral implants.

Explantation and reimplantation of cochlear implants.

This study looks at the rates of explantation and reimplantation surgery in adult cochlear implant patients between 1990 and 2002 and also evaluates the surgical and audiological implications. 15 (5.5%) out of 272 adult cochlear implantees (288 cochlear implants: 282 Nucleus, 4 MED-EL Combi 40, 2 Clarion) needed their devices removed (explanted). 14 out of the 15 patients selected received explantation, reimplantation or revision surgery. The main reasons included device failure (2.2%), wound and flap problems (1.8%), and electrode extrusion (0.73%). Wound and flap problems were more common with larger skin incisions. In staged reimplantations, reinsertion was made easier if the electrode was retained in situ until reimplantation. Performance of the replacement device was not related to the aetiology of deafness or to the cause of explantation. These data will be useful in counselling patients.