The bone conduction implant: Clinical results of the first six patients

Objective: To investigate audiological and quality of life outcomes for a new active transcutaneous device, called the bone conduction implant (BCI), where the transducer is implanted under intact skin. Design: A clinical study with sound field audiometry and questionnaires at six-month follow-up was conducted with a bone-anchored hearing aid on a softband as reference device. Study sample: Six patients (age 18–67 years) with mild-to-moderate conductive or mixed hearing loss. Results: The surgical procedure was found uneventful with no adverse events. The first hypothesis that BCI had a statistically significant improvement over the unaided condition was proven by a pure-tone-average improvement of 31.0 dB, a speech recognition threshold improvement in quiet (27.0 dB), and a speech recognition score improvement in noise (51.2 %). At speech levels, the signal-to-noise ratio threshold for BCI was ? 5.5 dB. All BCI results were better than, or similar to the reference device results, and the APHAB and GBI questionnaires scores showed statistically significant improvements versus the unaided situation, supporting the second and third hypotheses. Conclusions: The BCI provides significant hearing rehabilitation for patients with mild-to-moderate conductive or mixed hearing impairments, and can be easily and safely implanted under intact skin.     

The hearing benefit of cochlear implantation for individuals with unilateral hearing loss,but no tinnitus

Conclusion: Cochlear implants improve the hearing abilities of individuals with unilateral hearing loss and no tinnitus. The benefit is no different from that seen in patients with unilateral hearing loss and incapacitating tinnitus.

Objective: To evaluate hearing outcomes after cochlear implantation in individuals with unilateral hearing loss and no tinnitus and compare them to those obtained in a similar group who had incapacitating tinnitus.

Methods: Six cases who did not experience tinnitus before operation and 15 subjects with pre-operative tinnitus were evaluated with a structured interview, a monosyllabic word test under difficult listening situations, a sound localization test, and an APHAB (abbreviated profile of hearing aid benefit) questionnaire.

Results: All subjects used their cochlear implant more than 8?hours a day, 7 days a week. In ‘no tinnitus’ patients, mean benefit of cochlear implantation was 19% for quiet speech, 15% for speech in noise (with the same signal-to-noise ratio in the implanted and non-implanted ear), and 16% for a more favourable signal-to-noise ratio at the implanted ear. Sound localization error improved by an average of 19°. The global score of APHAB improved by 16%. The benefits across all evaluations did not differ significantly between the ‘no tinnitus’ and ‘tinnitus’ groups.     

Outcomes of the Baha Attract System combined with auricle reconstruction in mandarin speaking patients with bilateral microtia-atresia

Background: A transcutaneous bone-conduction hearing device (tBCHD), the Baha Attract System has been recently introduced to China, and very few studies have assessed the efficacy of this system in speakers of mandarin.

Objectives: This study aims to analyze the functional and cosmetic outcomes of this system.

Materials and Methods: This prospective study included 11 patients (nine males, two females), of mean age 16 years (range 9–32 years). Seven patients were conducted the implantation simultaneously with auricle reconstruction, and the other four were before it. Auditory results were compared between unaided patients and implanted patients. Subjective satisfaction was analyzed using three questionnaires.

Results: The mean sound field thresholds were 65.9?±?5.1?dB SPL unaided and 30.9?±?4.7?dB SPL with an implanted Baha Attract System, resulting in a mean hearing gain of 35.0?±?6.7?dB. The mean WRS scores were 47.8?±?8.7% unaided and 92.1?±?2.0% with the Baha Attract System, resulting in a mean improvement of 47.8?±?8.7%. No adverse events were reported and questionnaires showed good patients satisfaction.

Conclusions: The transcutaneous Baha Attract System is effective in mandarin speaking patients, and the combination of hearing rehabilitation and auricle reconstruction surgery is promising for patients with bilateral microtia-atresia.     

Transcutaneous bone conductive implants in patients with conductive/mixed hearing loss: audiological outcomes in noise condition

Background: Recently, the use of transcutaneous bone conduction implants (BCIs) has been increased. However, scarce data about BCI hearing recovery in noise conditions have been reported.

Objectives: To investigate the audiological benefits obtained with transcutaneous BCI-Sophono Alpha System in noise conditions. To evaluate post-implantation clinical outcomes and patient satisfaction levels.

Materials and methods: Fourteen patients suffering from conductive or mixed hearing loss implanted with the Sophono Alpha System were evaluated. Patients underwent physical examination, free-field pure-tone and speech audiometry both in unaided and aided conditions. The matrix sentence test was employed with fixed noise at 65?dB, and with a fluctuating primary signal, in three different conditions of noise presentations (S0/N0, S0/Ncontra, S0/Nipsi).

Results: Hearing gain, expressed as the difference between pre-implant AC and post-implant SAS free field, was on average 26.7?dB. The unaided speech recognition score in quiet conditions had a mean value of 64.6%, and improved after SAS implantation, achieving mean values of 98.2%. SRT₅₀ with the matrix sentence test improved in all three conditions of noise presentation.

Conclusions: Sophono Alpha System devices represent a valid treatment option for hearing rehabilitation of patients with conductive or mixed hearing loss. The audiological results regarding hearing gain in noise conditions were good.     

Comparative effects of unilateral and bilateral bone conduction hearing devices on functional hearing and sound localization abilities in patients with bilateral microtia-atresia

Abstract

Background: Various amplification options are available for patients with congenital bilateral conductive hearing loss. Unilateral bone conduction hearing device (BCHD) is widely used for these patients, whereas benefits of bilateral BCHDs in certain subgroups of patients require further exploration.

Objectives: To evaluate functional and directional hearing in patients with unilateral Bonebridge (MEDEL) and contralateral ADHEAR (MEDEL) devices.

Materials and methods: This study included 32 patients (20 males, 12 females), of mean age 11.8?years (range 7–27?years). Hearing thresholds, speech perception and sound localization were tested three months after activation of the Bonebridge under three conditions: unaided, unilateral BHCD (Bonebridge) and bilateral BHCDs (Bonebridge plus contralateral ADHEAR). Patient acceptance of these devices in daily life was evaluated by questionnaire.

Results: Compared with unaided, the mean hearing thresholds (0.5, 1, 2, and 4?kHz) and speech perception with unilateral BCHD and bilateral BCHDs were improved significantly (p?<?.05 each). Markers of directional hearing ability, including percentages of accurate responses, bias angles and RMS errors, were significantly better with bilateral BCHDs than unilateral BHCD (p?<?.05 each). Questionnaire revealed high patient satisfaction with both unilateral and bilateral devices.

Conclusions: Functional hearing and sound localization abilities were better with bilateral BCHDs than unilateral BCHD.     

Patient satisfaction after auditory implant surgery: ten-year experience from a single implanting unit center

Abstract

Conclusions: The satisfaction rate of the subjects with an auditory implant appears strictly related to the resulting auditory improvement, and the surgical variables would play a prevailing role in respect to the esthetic factors.

Objectives: To assess the rate of satisfaction in subjects who underwent the surgical application of an auditory device at a single Implanting Center Unit.

Method: A series of validated questionnaires has been administered to subjects who underwent the surgical application of different auditory devices. The Glasgow Benefit Inventory (GBI), the Visual Analog Scale (VAS), and the Abbreviated Profile of Hearing Aid Benefit (APHAB) have been used to compare the implanted situation with the hearing-aided one; a percutaneous bone conductive implant (pBCI) with an active middle ear implant (AMEI) on the round window in mixed hearing loss; and an invisible, fully-implantable device with a frankly and bulky semi-implantable device.

Results: The mean GBI scores were higher in Vibrant Soundbridge (VSB)^® and Bonebridge^® subjects, without significant differences among the various devices. The mean VAS score increased for all the devices in comparison with the conventional hearing aid. The mean APHAB score was similarly better in the implanted condition as total and partial scores.     

BoneBridge implantation in patients with single-sided deafness resulting from vestibular schwannoma resection: objective and subjective benefit evaluations

Abstract

Background: The BoneBridge could rehabilitate hearing for patients with single-sided deafness (SSD).

Objectives: To evaluate the objective and subjective benefits of BoneBridge implantation in patients after vestibular Schwannoma resection and to explore the factors affecting the benefits.

Material and methods: We prospectively enrolled all 15 patients implanted with BoneBridge after VS resection from January to June 2017. The primary outcome was the ability to hear in noisy conditions. The secondary outcomes were the soft-band BoneBridge try-on rate, the frequency of BB use, the sound source localization test result, and questionnaire measures of quality of life (QoL).

Results: Patients showed better speech recognition ability in the presence of noise with the BoneBridge. The BoneBridge provided no help in sound localization, although most patients reported subjective sound localization benefits. The results of QoL questionnaires showed significant satisfaction with BoneBridge implantation. The unilateral hearing deprivation duration and high education levels had significant impacts on the subjective benefits of patients.

Conclusions: The BoneBridge could improve speech recognition performance in complex auditory backgrounds, as well as QoL, especially in patients with short unilateral hearing deprivation durations and high education levels.

Significance: The BoneBridge is an effective hearing aid for single-sided deafness patients after VS removal.     

Bone conductive implants in single-sided deafness

Conclusion: Bone conduction implants (BCIs) have been shown to partially restore some of the functions lost when binaural hearing is missing, such as in subjects with single-sided deafness (SSD). The use of a single BCI needs to be recommended by a clinician based on thorough counselling with the SSD subject. Objectives: To perform an overview of the present capabilities of BCIs for SSD and to evaluate the reliability of the audiological evaluation for assessing speech recognition in noise and sound localization cues, which are major problems related to the loss of binaural hearing. Methods: Nine subjects with SSD who received BCI implants underwent a preoperative audiological evaluation that included sound field speech audiometry, word recognition score (WRS) testing and sound localization testing in quiet and in noise. They were also tested for the accuracy of their directional word recognition in noise and their subjective perceptions of their hearing difficulties using the APHAB questionnaire. Results: The mean maximum accuracy of word discrimination was 65.5% in the unaided condition and 78.9% in the BCI-aided condition. Sound localization in noise was better with the BCI than in the unaided condition, especially when the stimulus and noise were presented on the same side as the implanted ear. The accuracy of directional word recognition showed an improvement with the BCI with respect to the unaided condition on the BCI side, with either the stimulus in the implanted ear and the noise in the contralateral ear or with both the stimulus and noise presented to the implanted ear.     

Utility of bilateral acoustic hearing in combination with electrical stimulation provided by the cochlear implant

Abstract

Objective: The aim of the study was to quantify the benefit provided by having access to amplified acoustic hearing in the implanted ear for use in combination with contralateral acoustic hearing and the electrical stimulation provided by the cochlear implant. Design: Measures of spatial and non-spatial hearing abilities were obtained to compare performance obtained with different configurations of acoustic hearing in combination with electrical stimulation. In the combined listening condition participants had access to bilateral acoustic hearing whereas the bimodal condition used acoustic hearing contralateral to the implanted ear only. Experience was provided with each of the listening conditions using a repeated-measures A-B-B-A experimental design. Study sample: Sixteen post-linguistically hearing-impaired adults participated in the study. Results: Group mean benefit was obtained with use of the combined mode on measures of speech recognition in coincident speech in noise, localization ability, subjective ratings of real-world benefit, and musical sound quality ratings. Conclusions: Access to bilateral acoustic hearing after cochlear implantation provides significant benefit on a range of functional measures.     

Horizontal sound localisation accuracy in individuals with conductive hearing loss: effect of the bone conduction implant

Abstract

Objective: The objective of this study is to quantify the effect of the Bone Conduction Implant (BCI) on sound localisation accuracy in subjects with conductive hearing loss (CHL).

Design: The subjects were tested in a horizontal sound localisation task in which localisation responses were objectively obtained by eye-tracking, in a prospective, cross-sectional design. The tests were performed unaided and unilaterally aided. The stimulus used had a spectrum similar to female speech and was presented at 63 and 73?dB SPL. The main outcome measure was the error index (EI), ranging from 0 to 1 (perfect to random performance).

Study sample: Eleven subjects (aged 21–75 years, five females) with BCI participated in the study. Their mixed/conductive hearing loss was either unilateral (n?=?5) or bilateral (n?=?6).

Results: Three of five subjects (60%) with unilateral CHL, and four of six subjects (67%) with bilateral CHL showed significantly improved sound localisation when using a unilateral BCI (p?<?.05). For the subjects with bilateral CHL, a distinct linear relation between aided sound localisation and hearing thresholds in the non-implant ear existed at 73?dB SPL (18% decrease in the EI per 10?dB decrease in pure-tone average, r?=?0.98, p?<?.001).

Conclusions: Individuals with mixed/conductive hearing loss may benefit from a unilateral BCI in sound localisation.     

Transitions in auditory rehabilitation with bone conduction implants (BCI)

Background: The bone conductive implants (BCI) are nowadays a reliable alternative for rehabilitation of specific forms of hearing loss, i.e. conductive, mixed or single sided deafness (SSD).

Aims/Objective: To analyse the various factors in play when considering an auditory rehabilitation with a bone-conductive device (BCI).

Materials and Methods: The clinical charts of subjects who underwent BCI application at the same Implanting Center from 2005 to 2018 were retrieved analysing also the reason for eventual explantation and the alternative option (transition) for hearing rehabilitation.

Results: Nine BAHA Compact, 4 BAHA Intenso, 21 BAHA Divino, 3 BAHA BP100, 4 Ponto, 2 Sophono, 5 Bonebridge, 5 BAHA5 Attract; 11 BAHA5 Connect were used in 12 unilateral COM; 16 bilateral COM; 3 unilateral cholesteatoma; 6 bilateral cholesteatoma; 2 unilateral otosclerosis; 5 bilateral otosclerosis; 9 congenital malformations; 6 major otoneurosurgical procedures; 5 sudden deafness. Explantation was necessary for five subjects.

Conclusions: Middle ear pathology and sequels from surgery represent the most common reason for BCI implantation, both in unilateral and in bilateral cases. Transition from one implantable device to another one can be predictable, mostly when explantation is necessary.

Significance: The role of BCI for rehabilitation in middle ear pathology may be extremely important.     

Quality of life in persons with hearing loss: a study of patients referred to an audiological service

Abstract

Objective: To investigate the relationship between hearing loss (HL) and general quality of life (QoL) in adults seeking hearing aids (HAs).

Design: The patients completed the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire’s general part and a questionnaire measuring self-assessed communication ability (Abbreviated Profile of hearing Aid Benefit—APHAB). These responses were compared with EORTC scores from a general population and patients with former head and neck cancer.

Study sample: One-hundred and fifty-eight adults with HL were recruited prior to hearing aid (HA) fitting with one half seeking renewal of their HA.

Results: General QoL scores among patients with HL were similar to those in the general population, but higher than in many chronic serious diseases. Patients with unilateral HL reported slightly worse social function and more fatigue than patients with bilateral HL. Self-assessed communication ability correlated with general QoL scores. Also, we found that best ear pure tone average (PTA), cognitive and physical QoL function predicted APHAB scores.

Conclusion: In the investigated HL group, general QoL scores seem to be relatively close to those seen in the general population.     

Comparative outcomes of active and passive hearing devices by transcutaneous bone conduction

Conclusion Bonebridge (BB) and Sophono (SP) devices improved hearing; with the BB implant showing a better performance at medium and high frequencies. Furthermore, the BB, as an active implant, showed higher functional gain and increased time of use, when compared to the SP, a passive system. Objectives This study aims to compare surgical and audiological outcomes of SP and BB devices in order to assess and further differentiate the indication criteria. Methods Fourteen patients with conductive and mixed hearing loss were evaluated pre- and post-operatively (BB or SP) (period 2013–2014). Age, gender, surgical history, cause and type of hearing loss, implant use per day, levels of bone and air conduction, and functional gain were recorded. Data was analysed by Wilcoxon singed-rank and Wilcoxon rank-sum tests. Results Fourteen patients (BB; n?=?10 and SP; n?=?4) with an average age?=?25.42 years (CI95?=?12.41–38.43) were evaluated. The gender relation was equal (1:1), with pre-implantation osseous thresholds of 20.42?dB (CI95?=?11.15–29.69), and pre-implantation aerial thresholds of 70.83?dB (CI95?=?62.52–79.14). The SP wearing time was significantly lower than that of the BB (SP?=?7–10?h/day, BB?=?8–12?h/day; p?=?0.0323). The functional gain did not differ significantly between the two devices (BB?=?40.00?±?13.19?dB, SP?=?34.06?±?15.63?dB; p?=?0.3434), but a significant improvement from pre- to post-implantation was observed (p?p?=?0.0140) and 4?kHz (p?相似文献   

The case for earlier cochlear implantation in postlingually deaf adults

Abstract

Objective: This paper aimed to estimate the difference in speech perception outcomes that may occur due to timing of cochlear implantation in relation to the progression of hearing loss. Design: Data from a large population-based sample of adults with acquired hearing loss using cochlear implants (CIs) was used to estimate the effects of duration of hearing loss, age, and pre-implant auditory skills on outcomes for a hypothetical standard patient. Study sample: A total of 310 adults with acquired severe/profound bilateral hearing loss who received a CI in Melbourne, Australia between 1994 and 2006 provided the speech perception data and demographic information to derive regression equations for estimating CI outcomes. Results: For a hypothetical CI candidate with progressive sensorineural hearing loss, the estimates of speech perception scores following cochlear implantation are significantly better if implantation occurs relatively soon after onset of severe hearing loss and before the loss of all functional auditory skills. Conclusions: Improved CI outcomes and quality of life benefit may be achieved for adults with progressive severe hearing loss if they are implanted earlier in the progression of the pathology.     

Long term benefit of bone anchored hearing systems in single sided deafness

Abstract

Conclusion: Bone Anchored Hearing Systems (BAHS) can be expected to still be used by ～85% of patients with single sided deafness (SSD) 5 years after implantation, and by ～50% after 10 years. Objectives: To investigate the long-term use of BAHS and the reasons to stop.

Method: This was a retrospective chart review of all 33 German speaking adults with SSD who had been implanted with a BAHS at one center and of whom the implant status and use of the BAHS were known.

Results: Ranging from 2.6–12.3 years after BAHS implantation, 21 implantees (63.6%) were still using their device (average use?=?7.9 years). Seven (21.2%) had stopped using their BAHS because of insufficient benefit (audiologic reasons). The subjective assessment of the benefit of the BAHS differs significantly from the users. Five former users (15.2%) became non-users for reasons unrelated to their hearing performance, namely infections, implant loss, difficulties with the handling, or aesthetic reasons.     

A practical guide to cochlear implantation in adults with long durations of monaural sound deprivation

Abstract

Objective: This paper aims to summarize published findings by the authors and integrate these within current literature to support clinical guidelines when choosing an ear for cochlear implantation in adults with long-term monaural sound deprivation. Study sample: Four retrospective cohort studies based on data collected in five cochlear implantation centres with adults with bilateral hearing loss who used a single hearing aid for at least 15 years prior to unilateral or bilateral cochlear implantation. Design: Review, integration and interpretation of retrospective cohort studies to support clinical recommendations. Results: In this population, the prelingual nature of the hearing loss and the duration of bilateral significant hearing loss were the most reliable predictors of cochlear implantation outcomes. Importantly, the duration of sound deprivation in the ear to be implanted was not a significant predictor of speech recognition scores after cochlear implantation and should carry less weight in making recommendations. Conclusions: In most adults with postlingual hearing loss and long-term monaural sound deprivation, the sound-deprived sound deprivation ear should be preferred for implantation. For adults with prelingual deafness and monaural sound deprivation, the decision should weigh the risks of obtaining poorer results with the cochlear implant compared to the benefits of accessing binaural hearing.     

Bone-anchored Hearing Aids in Unilateral Inner Ear Deafness

In nine patients with unilateral deafness and normal hearing in the contralateral ear, measurements of sound localization and speech perception were obtained before intervention, with a conventional contralateral routing of sound (CROS) hearing aid and later with a bone-anchored hearing aid (BAHA) implanted in the deaf ear. Sound localization did not show any differences between the three conditions. Speech perception using short, everyday sentences showed a reduction in the head-shadow effect of 2 dB for both the conventional CROS hearing aid and the BAHA in comparison to the unaided condition. Patients' real-life experiences of the three conditions were evaluated using the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire. The results showed a significant benefit with the BAHA in situations involving background noise and reverberation and a reduced aversion to loud sounds in comparison to the unaided and conventional CROS conditions.     

Sound lateralization ability of patients with bilateral microtia and atresia after bilateral reconstruction of auricles and external auditory canals and fitting of new canal-type hearing aids to replace a bone conduction hearing aid

Abstract

Conclusion: Each of eight patients with bilateral microtia and atresia underwent bilateral reconstruction of the auricles and external auditory canals and were fitted bilateral canal-type hearing aids in the operated ears to replace a bone conduction hearing aid. The ability to discriminate inter-aural intensity difference (IID) and even inter-aural time difference (ITD) was retained in all these patients.

Objective: This study studied the post-operative sound lateralization ability of patients with bilateral microtia and atresia after total reconstruction of both auricles and external auditory canals, followed by fitting of bilateral canal-type hearing aids.

Methods: Eight patients with bilateral microtia and atresia ranging in age from 13–43 years were recruited in this study. Each of them underwent bilateral reconstruction of the auricles and external auditory canals and were fitted canal-type hearing aids in both the operated ears to replace a bone conduction hearing aid. A sound lateralization test was conducted to determine IID and ITD discrimination ability thresholds.

Results: In all the patients, the IID discrimination ability thresholds of the patients were more than 3-fold those of the controls, the ITD discrimination ability threshold was more than 5-fold those of controls, and binaural hearing was retained.     

Results of Active Middle Ear Implantation in Patients With Mixed Hearing Loss After Middle Ear Surgery: A Prospective Multicenter Study (the ROMEO Study)

ObjectivesThis study was conducted to evaluate the user satisfaction, efficacy, and safety of round window (RW) vibroplasty using the Vibrant Soundbridge (VSB) in patients with persistent mixed hearing loss after mastoidectomy.Methods The study included 27 patients (mean age, 58.7 years; age range, 28–76 years; 11 men and 16 women) with mixed hearing loss after mastoidectomy from 15 tertiary referral centers in Korea. The VSB was implanted at the RW. The Korean translation of the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire and the Korean version of the International Outcome Inventory for Hearing Aids (K-IOI-HA) questionnaire were used to evaluate user satisfaction as the primary outcome. The secondary outcome measures were audiological test results and complication rates.ResultsThe mean scores for ease of communication (61.3% to 29.7% to 30.2%), reverberation (62.1% to 43.1% to 37.4%), and background noise (63.3% to 37.7% to 34.3%) subscales of the APHAB questionnaire significantly decreased after VSB surgery. The mean K-IOI-HA scores at 3 and 6 months after surgery were significantly higher than the mean preoperative score (18.6 to 27.2 to 28.1). The postoperative VSB-aided thresholds were significantly lower than the preoperative unaided and hearing aid (HA)-aided thresholds. There was no significant difference between preoperative unaided, preoperative HA-aided, and postoperative VSB-aided maximum phonetically balanced word-recognition scores. None of the 27 patients experienced a change in postoperative bone conduction pure tone average. One patient developed temporary facial palsy and two developed surgical wound infections.ConclusionRW vibroplasty resulted in improved satisfaction and audiological test results in patients with mixed hearing loss after mastoidectomy, and the complication rate was tolerable.     

Effects of loss of residual hearing on speech performance with the CI422 and the Hybrid-L electrode

Abstract

Objective

Preservation of residual low-frequency hearing has become a priority in cochlear implantation. The purpose of this study was to compare rates of hearing preservation and effects on performance of loss of low-frequency acoustic hearing with two different length electrodes.

Study design

Retrospective chart review.

Setting

Tertiary Care Hospital.

Patients

Twelve patients were implanted with the CI422 a slim-straight electrode; the second group consisted of 10 patients implanted with the Hybrid-L, a shorter hearing preservation electrode.

Main outcome measure

Audiometric thresholds and speech perception measures.

Results

At 1 year, 3/10 (30%) patients with the Hybrid-L and 7/12 (58%) patients with the CI422 lost residual acoustic hearing resulting in a profound hearing loss in the implanted ear. In comparing these patients in particular, mean CNC words in the implanted ear were 72% in the CI422 electrode group and 15% in the Hybrid-L electrode group at 1 year (P = 0.03). While hearing preservation rates with the Hybrid-L tended to be better, among recipients who lost residual hearing, speech perception was better in those with the longer CI422 electrode.

Conclusions

With emphasis on preservation of residual hearing, patients need to be counseled regarding possible outcomes and options should loss of residual hearing occur following implantation. While shorter electrodes may have better rates of hearing preservation, the patients with the longer straight electrode in our study had significantly better speech understanding following the loss of residual hearing.