Hearing Asymmetry Biases Spatial Hearing in Bimodal Cochlear-Implant Users Despite Bilateral Low-Frequency Hearing Preservation.

Many cochlear implant users with binaural residual (acoustic) hearing benefit from combining electric and acoustic stimulation (EAS) in the implanted ear with acoustic amplification in the other. These bimodal EAS listeners can potentially use low-frequency binaural cues to localize sounds. However, their hearing is generally asymmetric for mid- and high-frequency sounds, perturbing or even abolishing binaural cues. Here, we investigated the effect of a frequency-dependent binaural asymmetry in hearing thresholds on sound localization by seven bimodal EAS listeners. Frequency dependence was probed by presenting sounds with power in low-, mid-, high-, or mid-to-high-frequency bands. Frequency-dependent hearing asymmetry was present in the bimodal EAS listening condition (when using both devices) but was also induced by independently switching devices on or off. Using both devices, hearing was near symmetric for low frequencies, asymmetric for mid frequencies with better hearing thresholds in the implanted ear, and monaural for high frequencies with no hearing in the non-implanted ear. Results show that sound-localization performance was poor in general. Typically, localization was strongly biased toward the better hearing ear. We observed that hearing asymmetry was a good predictor for these biases. Notably, even when hearing was symmetric a preferential bias toward the ear using the hearing aid was revealed. We discuss how frequency dependence of any hearing asymmetry may lead to binaural cues that are spatially inconsistent as the spectrum of a sound changes. We speculate that this inconsistency may prevent accurate sound-localization even after long-term exposure to the hearing asymmetry.

Genetic Hearing Loss Affects Cochlear Processing.

The relationship between speech recognition and hereditary hearing loss is not straightforward. Underlying genetic defects might determine an impaired cochlear processing of sound. We obtained data from nine groups of patients with a specific type of genetic hearing loss. For each group, the affected cochlear site-of-lesion was determined based on previously published animal studies. Retrospectively obtained speech recognition scores in noise were related to several aspects of supra-threshold cochlear processing as assessed by psychophysical measurements. The differences in speech perception in noise between these patient groups could be explained by these factors and partially by the hypothesized affected structure of the cochlea, suggesting that speech recognition in noise was associated with a genetics-related malfunctioning of the cochlea. In particular, regression models indicate that loudness growth and spectral resolution best describe the cochlear distortions and are thus a good biomarker for speech understanding in noise.

Home-Based Audiometry With a Smartphone App: Reliable Results?

PURPOSE: The aim of this study was to assess the test-retest reliability of a smartphone-based hearing test, performed without supervision of a hearing professional in an uncontrolled environment. METHOD: The hearing application is based on an automated hearing test (DuoTone) and relies on verification procedures (ambient noise monitoring algorithm, graphical user interface) to ensure appropriate measurement conditions. Thresholds obtained with DuoTone were compared to those obtained with standard clinical audiometry for 0.5, 1, 2, and 4 kHz in 13 subjects. Subsequently, test-retest reliability was analyzed using anonymized cloud-stored data from a large group of app users (1,641 subjects) who performed multiple hearing tests. Thresholds at minimum or maximum presentation level of the hearing test (10 dB HL, 85 dB HL) were excluded to avoid floor/ceiling effects. A subset (500 subjects) was created to exclude potentially unreliable data. Test-retest thresholds were compared at 12 test frequencies, from 125 Hz to 12 kHz. RESULTS: Thresholds determined by DuoTone and clinical audiometry did not differ significantly for each test frequency. Regarding test-retest analysis, the percentage of test-retest results within 5 dB ranged from 60% to 77% per test frequency. Results from the subset were not substantially different. Test-retest reliability for app users was comparable to results published in the literature regarding test-retest reliability of audiometry, performed in the clinic. CONCLUSIONS: Initial validation results suggest that thresholds obtained with DuoTone are comparable to clinical audiometry (four frequencies tested). The hearing app provides reliable hearing thresholds between 15 and 80 dB HL (12 frequencies tested) with a test-retest reliability comparable to clinical audiometry.

Unexplained Variation in Benefit of Treatment of Congenital Unilateral Aural Atresia: A Review of the Literature.

OBJECTIVE: A review of published data regarding binaural hearing after treatment of congenital unilateral conductive hearing loss (UCHL) due to aural atresia. Treatment options concern atresia surgery (reconstructive surgery), application of a bone conduction device (BCD), or application of a middle ear implant (MEI). DATA SOURCES: Database PubMed was searched for articles published in English and German between January 1, 1994, and January 1, 2019. STUDY SELECTION: The initial search identified 52 studies, of which 9 met the inclusion criteria. DATA SYNTHESIS: Comparison of studies was based on a structured review. Meta-analysis was not feasible because of the heterogeneity of outcome measures, the limited number of relevant papers (9), and diverse types of treatment (5). CONCLUSIONS: Treatment of UCHL results in bilateral hearing instead of binaural hearing. The large intersubject variability in benefit of treatment is unexplained with a clear improvement in the minority of listeners and a limited improvement or binaural interference in most listeners after atresia repair or amplification with a BCD or MEI.

Spatial Hearing by Bilateral Cochlear Implant Users With Temporal Fine-Structure Processing.

Several studies have demonstrated the advantages of the bilateral vs. unilateral cochlear implantation in listeners with bilateral severe to profound hearing loss. However, it remains unclear to what extent bilaterally implanted listeners have access to binaural cues, e.g., accurate processing of interaural timing differences (ITDs) for low-frequency sounds (<1.5 kHz) and interaural level differences (ILDs) for high frequencies (>3 kHz). We tested 25 adult listeners, bilaterally implanted with MED-EL cochlear implant (CI) devices, with and without fine-structure (FS) temporal processing as encoding strategy in the low-frequency channels. In order to assess whether the ability to process binaural cues was affected by fine-structure processing, we performed psychophysical ILD and ITD sensitivity measurements and free-field sound localization experiments. We compared the results of the bilaterally implanted listeners with different numbers of FS channels. All CI listeners demonstrated good sensitivity to ILDs, but relatively poor to ITD cues. Although there was a large variability in performance, some bilateral CI users showed remarkably good localization skills. The FS coding strategy for bilateral CI hearing did not improve fine-structure ITD processing for spatial hearing on a group level. However, some CI listeners were able to exploit weakly informative temporal cues to improve their low-frequency spatial perception.

The Merits of Bilateral Application of Bone-Conduction Devices in Children With Bilateral Conductive Hearing Loss.

OBJECTIVES: This study aims to characterize lateralization of sounds and localization of sounds in children with bilateral conductive hearing loss (BCHL) when listening with either one or two percutaneous bone conduction devices (BCDs). DESIGN: Sound lateralization was measured with the minimum audible angle test in which children were asked to indicate from which of the two visible speakers the sound originated. Sound localization was measured with a test in which stimuli were presented from speakers that were not visible to the children. In the sound localization test, 150 ms broadband noise bursts were presented, and sound level was roved over a 20-dB range. Because speakers were not visible the localization response was not affected by any visual cue. The sound localization test provides a clear distinction between lateralization and localization of sounds. Ten children with congenital BCHL and one child with acquired BCHL participated. RESULTS: Both lateralization and sound localization were better with bilateral BCDs compared with the unilaterally aided conditions. In the bilateral BCD condition, lateralization was close to normal in nearly all the children. The localization test demonstrated lateralization rather than sound localization behavior when listening with bilateral BCDs. Furthermore, in the unilateral aided condition, stimuli presented at different sound levels were mainly perceived at the same location. CONCLUSIONS: This study demonstrates that, in contrast to listening with two BCDs, children demonstrated difficulties in lateralization of sounds and in sound localization when listening with just one BCD (i.e., one BCD turned off). Because both lateralization and sound localization behavior were tested, it could be demonstrated that these children are more able to lateralize than localize sounds when listening with bilateral BCDs. The present study provides insight in (sub-optimal) sound localization capabilities of children with congenital BCHL in the unilateral-aided and bilateral-aided condition. Despite the sub-optimal results on sound localization, this study underlines the merits of bilateral application of BCDs in such children.

Hearing Aid Treatment for Patients with Mixed Hearing Loss. Part II: Speech Recognition in Comparison to Direct Acoustic Cochlear Stimulation.

BACKGROUND: The conventional therapy for severe mixed hearing loss is middle ear surgery combined with a power hearing aid. However, a substantial group of patients with severe mixed hearing loss cannot be treated adequately with today's state-of-the-art (SOTA) power hearing aids, as predicted by the accompanying part I of this publication, where we compared the available maximum power output (MPO) and gain from technical specifications to requirements for optimum benefit using a common fitting rule. Here, we intended to validate the theoretical assumptions from part I experimentally in a mixed hearing loss cohort fitted with SOTA power hearing aids. Additionally, we compared the results with an implantable hearing device that circumvents the impaired middle ear, directly stimulating the cochlea, as this might be a better option. OBJECTIVES: Speech recognition outcomes obtained from patients with severe mixed hearing loss supplied acutely with a SOTA hearing aid were studied to validate the outcome predictions as described in part I. Further, the results obtained with hearing aids were compared to those in direct acoustic cochlear implant (DACI) users. MATERIALS AND METHODS: Twenty patients (37 ears with mixed hearing loss) were provided and fitted with a SOTA power hearing aid. Before and after an acclimatization period of at least 4 weeks, word recognition scores (WRS) in quiet and in noise were studied, as well as the speech reception threshold in noise (SRT). The outcomes were compared retrospectively to a second group of 45 patients (47 ears) using the DACI device. Based on the severity of the mixed hearing loss and the available gain and MPO of the SOTA hearing aid, the hearing aid and DACI users were subdivided into groups with prediction of sufficient, partially insufficient, or very insufficient hearing aid performance. RESULTS: The patients with predicted adequate SOTA hearing aid performance indeed showed the best WRS in quiet and in noise when compared to patients with predicted inferior outcomes. Insufficient hearing aid performance at one or more frequencies led to a gradual decrease in hearing aid benefit, validating the criteria used here and in the accompanying paper. All DACI patients showed outcomes at the same level as the adequate hearing aid performance group, being significantly better than those of the groups with inadequate hearing aid performance. Whereas WRS in quiet and noise were sensitive to insufficient gain or output, showing significant differences between the SOTA hearing aid and DACI groups, the SRT in noise was less sensitive. CONCLUSIONS: Limitations of outcomes in mixed hearing loss individuals due to insufficient hearing aid performance can be accurately predicted by applying a commonly used fitting rule and the 35-dB dynamic range rule on the hearing aid specifications. Evidently, when outcomes in patients with mixed hearing loss using the most powerful hearing aids are insufficient, bypassing the middle ear with a powerful active middle ear implant or direct acoustic implant can be a promising alternative treatment.

Contribution of spectral pinna cues for sound localization in children with congenital unilateral conductive hearing loss after hearing rehabilitation.

Congenital unilateral conductive hearing loss (UCHL) jeopardizes directional hearing and speech perception in noisy conditions. Potentially, children with congenital UCHL can benefit from fitting a hearing device, such as a bone-conduction device (BCD). However, the literature reports limited benefit from fitting a BCD, and often, surprisingly, relatively good sound localization in the unaided condition is reported. In this study, we hypothesized that the limited benefit with a BCD is related to (i) insufficient access to binaural cues and (ii) relying on monaural spectral pinna cues for sound localization in the horizontal plane. Directional hearing was tested in seventeen children with congenital UCHL (age 6-19) using a percutaneous BCD. Additionally, a mold was placed in the pinna of the normal-hearing ear to diminish direction-dependent spectral pinna cues. Relatively good localization in azimuth was found in the unaided hearing condition in the majority of the children. Sound localization improved when listening with a BCD, and no correlation between age of implantation and aided localization performance was found. When the mold was inserted, the unaided and aided localization abilities of most children deteriorated. Interestingly, in the children with poor localization performance in the unaided condition, sound localization improved significantly with the BCD, and was hardly affected by molding the pinna of the normal-hearing ear. These observations indicate that the majority of these children rely on spectral pinna cues to localize sounds, independent of listening with or without their device. In conclusion, an important reason for the limited benefit of BCD fitting in children with congenital UCHL might be ascribed to an effective coping strategy (use of spectral pinna cues) that still plays a dominant role after BCD fitting.

An Individual With Hearing Preservation and Bimodal Hearing Using a Cochlear Implant and Hearing Aids Has Perturbed Sound Localization but Preserved Speech Perception.

This study describes sound localization and speech-recognition-in-noise abilities of a cochlear-implant user with electro-acoustic stimulation (EAS) in one ear, and a hearing aid in the contralateral ear. This listener had low-frequency, up to 250 Hz, residual hearing within the normal range in both ears. The objective was to determine how hearing devices affect spatial hearing for an individual with substantial unaided low-frequency residual hearing. Sound-localization performance was assessed for three sounds with different bandpass characteristics: low center frequency (100-400 Hz), mid center frequency (500-1,500 Hz) and high frequency broad-band (500-20,000 Hz) noise. Speech recognition was assessed with the Dutch Matrix sentence test presented in noise. Tests were performed while the listener used several on-off combinations of the devices. The listener localized low-center frequency sounds well in all hearing conditions, but mid-center frequency and high frequency broadband sounds were localized well almost exclusively in the completely unaided condition (mid-center frequency sounds were also localized well with the EAS device alone). Speech recognition was best in the fully aided condition with speech presented in the front and noise presented at either side. Furthermore, there was no significant improvement in speech recognition with all devices on, compared to when the listener used her cochlear implant only. Hearing aids and cochlear implant impair high frequency spatial hearing due to improper weighing of interaural time and level difference cues. The results reinforce the notion that hearing symmetry is important for sound localization. The symmetry is perturbed by the hearing devices for higher frequencies. Speech recognition depends mainly on hearing through the cochlear implant and is not significantly improved with the added information from hearing aids. A contralateral hearing aid provides benefit when the noise is spatially separated from the speech. However, this benefit is explained by the head shadow in that ear, rather than by an ability to spatially segregate noise from speech, as sound localization was perturbed with all devices in use.

Efficacy of Auditory Implants for Patients With Conductive and Mixed Hearing Loss Depends on Implant Center.

INTRODUCTION: Although from a technological point of view, progress is impressive, most implantable hearing devices for conductive or mixed hearing loss have a limited capacity. These devices all bypass the impaired middle ear; therefore, the desired amplification (gain) should be based on the cochlear hearing loss (component) only. The aim of the study is to review the literature with regard to accomplished gain with current implantable devices. METHOD: Thirty-one articles could be included. Aided thresholds were compared with prescribed values, based on cochlear hearing loss (bone-conduction thresholds), according to the well-validated NAL rule. RESULTS: For the majority of the studies, NAL targets were not met. Variation in accomplished gain between implant teams was unacceptably large, largely independent of the type of device that was used. NAL targets were best met at 2 kHz, with worse results at the other frequencies. CONCLUSION: Large variations in reported results were found, which primarily depended on implant center. Based on the analyses, a pragmatic fitting procedure is proposed which should minimize the differences between implant centres.

Expanding unilateral cochlear implantation criteria for adults with bilateral acquired severe sensorineural hearing loss.

OBJECTIVES: To report on a retrospective cohort study on the effects of expanding inclusion criteria for application of cochlear implants (CIs) on the performance 1-year post-implantation. METHODS: Based on pre-implantation audiometric thresholds and aided speech recognition scores, the data of 164 CI recipients were divided into a group of patients that fulfilled conservative criteria (mean hearing loss at 0.5, 1 and 2 kHz > 85 dB HL and phoneme scores with hearing aids < 30%), and the remaining group of patients that felt outside this conservative criterion. Speech recognition scores (in quiet) and quality of life (using the NCIQ) of both groups, measured at 1-year post-implantation, were compared. RESULTS: The group that felt outside the conservative criterion showed a higher phoneme score at 1-year post-implantation compared to the conservative group, suggesting that relaxed criteria have a positive influence on the speech recognition results with CI. With respect to quality of life, both groups significantly improved 1-year post-implantation. The conservative group showed a higher benefit on the advanced perception domain of the NCIQ. Based on their worse pre-implantation hearing, this was expected. CONCLUSIONS: The data suggest that relaxation of CI indication positively affects the speech recognition performance of patients with severe hearing loss. Both groups of patients showed a positive effect of CI on the quality of life. This benefit relates to communication skills and the subjective day-to-day functioning in society.

Sound-localization performance of patients with single-sided deafness is not improved when listening with a bone-conduction device.

An increased number of treatment options has become available for patients with single sided deafness (SSD), who are seeking hearing rehabilitation. For example, bone-conduction devices that employ contralateral routing of sound (CROS), by transmitting acoustic bone vibrations from the deaf side to the cochlea of the hearing ear, are widely used. However, in some countries, cochlear implantation is becoming the standard treatment. The present study investigated whether CROS intervention, by means of a CROS bone-conduction device (C-BCD), affected sound-localization performance of patients with SSD. Several studies have reported unexpected moderate to good unilateral sound-localization abilities in unaided SSD listeners. Listening with a C-BCD might deteriorate these localization abilities because sounds are transmitted, through bone conduction to the contralateral normal hearing ear, and could thus interfere with monaural level cues (i.e. ambiguous monaural head-shadow cues), or with the subtle spectral localization cues, on which the listener has learned to rely on. The present study included nineteen SSD patients who were using their C-BCD for more than five months. To assess the use of the different localization cues, we investigated their localization abilities to broadband (BB, 0.5-20 kHz), low-pass (LP, 0.5-1.5 kHz), and high-pass filtered noises (HP, 3-20 kHz) of varying intensities. Experiments were performed in complete darkness, by measuring orienting head-movement responses under open-loop localization conditions. We demonstrate that a minority of listeners with SSD (5 out of 19) could localize BB and HP (but not LP) sounds in the horizontal plane in the unaided condition, and that a C-BCD did not deteriorate their localization abilities.

Ototoxicity in locally advanced head and neck cancer patients treated with induction chemotherapy followed by intermediate or high-dose cisplatin-based chemoradiotherapy.

BACKGROUND: This study evaluated ototoxicity in locally advanced head and neck cancer patients treated in the CONDOR study with docetaxel/cisplatin/5-fluorouracil (TPF) followed by conventional radiotherapy with concomitant cisplatin 100 mg/m2 on days 1, 22, and 43 (cis100+RT) versus accelerated radiotherapy with concomitant cisplatin weekly 40 mg/m2 (cis40+ART). METHODS: Sixty-two patients were treated in this study. Audiometry was performed at baseline, during TPF, before start of chemoradiotherapy, and 1, 4, 8, and 12 months after treatment. RESULTS: A complete dataset of audiometric data was available of 12 patients treated with high-dose cisplatin and of 11 patients treated with intermediate-dose cisplatin. Patients in the high-dose group showed significant more hearing loss than in the intermediate group at 4 kHz ([z = 1.98; P = .04] and 8 kHz [z = 2.07; P < .03]). Interindividual variation was high in both groups. CONCLUSION: After induction TPF, more ototoxicity was observed in chemoradiotherapy with cis100+RT than after chemoradiotherapy with cis40+ART.

Measuring Cortical Activity During Auditory Processing with Functional Near-Infrared Spectroscopy.

Functional near-infrared spectroscopy (fNIRS) is an optical, non-invasive neuroimaging technique that investigates human brain activity by calculating concentrations of oxy- and deoxyhemoglobin. The aim of this publication is to review the current state of the art as to how fNIRS has been used to study auditory function. We address temporal and spatial characteristics of the hemodynamic response to auditory stimulation as well as experimental factors that affect fNIRS data such as acoustic and stimulus-driven effects. The rising importance that fNIRS is generating in auditory neuroscience underlines the strong potential of the technology, and it seems likely that fNIRS will become a useful clinical tool.

Effect of extreme adaptive frequency compression in bimodal listeners on sound localization and speech perception.

OBJECTIVES: This study aimed to improve access to high-frequency interaural level differences (ILD), by applying extreme frequency compression (FC) in the hearing aid (HA) of 13 bimodal listeners, using a cochlear implant (CI) and conventional HA in opposite ears. DESIGN: An experimental signal-adaptive frequency-lowering algorithm was tested, compressing frequencies above 160 Hz into the individual audible range of residual hearing, but only for consonants (adaptive FC), thus protecting vowel formants, with the aim to preserve speech perception. In a cross-over design with at least 5 weeks of acclimatization between sessions, bimodal performance with and without adaptive FC was compared for horizontal sound localization, speech understanding in quiet and in noise, and vowel, consonant and voice-pitch perception. RESULTS: On average, adaptive FC did not significantly affect any of the test results. Yet, two subjects who were fitted with a relatively weak frequency compression ratio, showed improved horizontal sound localization. After the study, four subjects preferred adaptive FC, four preferred standard frequency mapping, and four had no preference. Noteworthy, the subjects preferring adaptive FC were those with best performance on all tasks, both with and without adaptive FC. CONCLUSION: On a group level, extreme adaptive FC did not change sound localization and speech understanding in bimodal listeners. Possible reasons are too strong compression ratios, insufficient residual hearing or that the adaptive switching, although preserving vowel perception, may have been ineffective to produce consistent ILD cues. Individual results suggested that two subjects were able to integrate the frequency-compressed HA input with that of the CI, and benefitted from enhanced binaural cues for horizontal sound localization.

Cochlear implantation and clinical features in patients with Noonan syndrome and Noonan syndrome with multiple lentigines caused by a mutation in PTPN11.

Existing literature only reports a few patients with Noonan syndrome (NS) and Noonan syndrome with multiple lentigines (NSML) who underwent cochlear implantation (CI). The present study describes four NS patients and one NSML patient with a PTPN11 mutation. They all had severe to profound hearing loss, and they received a CI. The age at which the CI surgery occurred ranged from 1 to 13 years old, and the audiological results in all five patients improved after the CI. Otological and audiological examinations in NS and NSML are important, and for those with severe hearing loss, the CI surgery improved the audiological outcome regardless of age.

Cochlear Implantation in Patients With Usher Syndrome Type IIa Increases Performance and Quality of Life.

OBJECTIVES: Usher syndrome type IIa (USH2a) is characterized by congenital moderate to severe hearing impairment and retinitis pigmentosa. Hearing rehabilitation starts in early childhood with the application of hearing aids. In some patients with USH2a, severe progression of hearing impairment leads to insufficient speech intelligibility with hearing aids and issues with adequate communication and safety. Cochlear implantation (CI) is the next step in rehabilitation of such patients. This study evaluates the performance and benefit of CI in patients with USH2a. DESIGN: Retrospective case-control study to evaluate the performance and benefit of CI in 16 postlingually deaf adults (eight patients with USH2a and eight matched controls). Performance and benefit were evaluated by a speech intelligibility test and three quality-of-life questionnaires. RESULTS: Patients with USH2a with a mean age of 59 years at implantation exhibited good performance after CI. The phoneme scores improved significantly from 41 to 87% in patients with USH2a (p = 0.02) and from 30 to 86% in the control group (p = 0.001). The results of the questionnaire survey demonstrated a clear benefit from CI. There were no differences in performance or benefit between patients with USH2a and control patients before and after CI. CONCLUSIONS: CI increases speech intelligibility and improves quality of life in patients with USH2a.

An Assessment of the Clinical Acceptability of Direct Acoustic Cochlear Implantation for Adults With Advanced Otosclerosis in the United Kingdom.

HYPOTHESIS: Assess the clinical acceptability of direct acoustic cochlear implantation for patients with advanced otosclerosis and the support for conducting a controlled trial of its effectiveness in the United Kingdom. BACKGROUND: Emerging evidence supports the efficacy of direct acoustic cochlear implantation in patients with advanced otosclerosis whose needs cannot be managed using the combination of stapes surgery and hearing aids. A controlled trial would provide evidence for its effectiveness and cost-effectiveness to healthcare commissioners. METHODS: An online survey of clinical professionals was constructed to characterize current standard of care for patients with advanced otosclerosis and to assess whether clinicians would be willing to refer patients into a trial to evaluate direct acoustic cochlear implantation. A consensus process was conducted to define inclusion criteria for the future trial. RESULTS: No survey respondent considered direct acoustic cochlear implantation to be inappropriate with a majority indicating that they would refer patients into a future trial. The consensus was that there is a lack of available treatment options for those patients with bone conduction thresholds worse than 55 dB HL and who did not meet current criteria for cochlear implantation. CONCLUSION: The present study confirms that a controlled trial to evaluate the effectiveness of direct acoustic cochlear implantation would have the support of clinicians in the United Kingdom. A feasibility study would be required to determine whether patients who meet the inclusion criteria could be recruited in a timely manner and in sufficient numbers to conduct a formal evaluation of effectiveness.