Monosyllable speech perception of Japanese hearing aid users with prelingual hearing loss: implications for surgical indication of cochlear implant

OBJECTIVE: The monosyllable speech perception ability after years of educational intervention was compared between prelingually deafened pediatric hearing aid users and their cochlear implant counterparts. DESIGN: An open-set monosyllabic speech perception test was conducted on all subjects. The test required subjects to indicate a corresponding Japanese character to that spoken by the examiner. Fifty-two subjects with prelingual hearing impairment (47 hearing aid users and 5 cochlear implant users) were examined. RESULTS: Hearing aid users with average pure-tone thresholds less than 90 dB HL demonstrated generally better monosyllable perception than 70%, which was equivalent or better performance than that of the cochlear implant group. Widely dispersed speech perception was observed within the 90-99 dB HL hearing-aid user group with most subjects demonstrating less than 50% speech perception. In the cluster of >100 dB HL, few cases demonstrated more than 50% in speech perception. The perception ability of the vowel part of each mora within the cochlear implant group was 100% and corresponding to that of hearing aid users with moderate and severe hearing loss. CONCLUSION: Hearing ability among cochlear implant users can be comparable with that of hearing aid users with average unaided pure-tone thresholds of 90 dB HL, after monosyllabic speech perception testing was performed.     

Patients utilizing a hearing aid and a cochlear implant: speech perception and localization

OBJECTIVE: The purpose of this pilot study was to document speech perception and localization abilities in patients who use a cochlear implant in one ear and a hearing aid in the other ear. DESIGN: We surveyed a group of 111 cochlear implant patients and asked them whether they used a hearing aid on their unimplanted ear. The first three patients who were available were tested on word and sentence recognition and localization tasks. Speech stimuli were presented from the front in quiet and in noise. In the latter conditions, noise was either from the front, the right, or the left. Localization was tested with noise bursts presented at 45 degrees from the right or left. In addition we asked the patients about their abilities to integrate the information from both devices. RESULTS: Speech perception tests in quiet showed a binaural advantage for only one of the three patients for words and none for sentences. With speech and noise both in front of the patient, two patients performed better with both devices than with either device alone. With speech in front and noise on the hearing aid side, no binaural advantage was seen, but with noise on the cochlear implant side, one patient showed a binaural advantage. Localization ability improved with both devices for two patients. The third patient had above-chance localization ability with his implant alone. CONCLUSIONS: A cochlear implant in one ear and a hearing aid in the other ear can provide binaural advantages. The patient who did not show a clear binaural advantage had the poorest hearing aid alone performance. The absolute and relative levels of performance at each ear are likely to influence the potential for binaural integration.     

Evaluation of binaural functions in bilateral cochlear implant users

Binaural abilities are difficult to assess, yet important to understand, in the course of rehabilitating bilateral cochlear implantees. One purpose of this research was to develop a binaural assessment methodology using direct electrical input to the cochlear implant, 'direct connect assessment', pre-processed by appropriate headrelated transfer functions (HRTFs) to simulate the binaural cues for spatial release from masking and sound localization. A second purpose was to create and evaluate new, modified rules for adaptively measuring the speech reception threshold in noise with the Hearing In Noise Test (HINT) for use with cochlear implant subjects. A third purpose was to develop a new sound localization protocol whose difficulty is adjusted to the sound localization ability of the individual cochlear implant subject. These new protocols were combined with the direct connect method and evaluated in acoustic hearing subjects and cochlear implant subjects. HINT thresholds and sound localization scores measured in the sound field and with the direct connect method did not differ significantly and were highly correlated in both groups. Measures of spatial release from masking, head shadow effects, binaural squelch, and binaural summation derived from the thresholds also were comparable for both methods. The alternative adaptive rules for HINT were found to measure different points on the same performance-intensity function. These rules allowed all cochlear implant subjects in the study to be tested adaptively and their thresholds to be compared to norms. Sound localization was measured successfully in all subjects with a sector localization protocol whose difficulty is to be adjusted to the localization ability of the subject. This protocol reduced by one-third to one-half the time required to complete the assessment of the localization ability.     

Comparison of speech perception between monaural and binaural hearing in cochlear implant patients

OBJECTIVE: To assess the advantages of binaural hearing for cochlear implant (CI) users using a hearing aid (HA) for the contralateral ear. MATERIAL AND METHODS: The subjects comprised 3 males and 3 females (age range 48-84 years). All of them had been using a CI and HA for > 6 months. Their speech perception was examined in quiet using monosyllables and Japanese Hearing in Noise Test (J-HINT) sentences. Speech perception in noise was examined using J-HINT sentences. Late cortical waves were measured while subjects listened to 1 kHz frequent and 2 kHz target tone stimuli. The latency of the event-related potential (P300) wave was compared for monaural and binaural hearing conditions. RESULTS: Three subjects showed significantly better results for binaural than monaural (CI alone) hearing for monosyllables and HINT sentences (p < 0.05; paired t-test). Subjects with better speech perception had been using an HA for longer than those with poor performance (18.3 vs 4.0 years). The overall average score was better for binaural than monaural hearing in the speech perception test under quiet and noisy conditions. Comparison of the latency of the P300 wave under monaural and binaural hearing conditions showed a significantly shorter latency for the latter (p = 0.02; paired t-test). CONCLUSIONS: Although the use of an HA alone showed marginal benefit for CI users, binaural hearing (CI+HA) resulted in a significant improvement in speech perception under various circumstances.     

Evaluation of binaural functions in bilateral cochlear implant users

Binaural abilities are difficult to assess, yet important to understand, in the course of rehabilitating bilateral cochlear implantees. One purpose of this research was to develop a binaural assessment methodology using direct electrical input to the cochlear implant, ‘‘direct connect assessment’’, pre-processed by appropriate headrelated transfer functions (HRTFs) to simulate the binaural cues for spatial release from masking and sound localization. A second purpose was to create and evaluate new, modified rules for adaptively measuring the speech reception threshold in noise with the Hearing In Noise Test (HINT) for use with cochlear implant subjects. A third purpose was to develop a new sound localization protocol whose difficulty is adjusted to the sound localization ability of the individual cochlear implant subject. These new protocols were combined with the direct connect method and evaluated in acoustic hearing subjects and cochlear implant subjects. HINT thresholds and sound localization scores measured in the sound field and with the direct connect method did not differ significantly and were highly correlated in both groups. Measures of spatial release from masking, head shadow effects, binaural squelch, and binaural summation derived from the thresholds also were comparable for both methods. The alternative adaptive rules for HINT were found to measure different points on the same performance-intensity function. These rules allowed all cochlear implant subjects in the study to be tested adaptively and their thresholds to be compared to norms. Sound localization was measured successfully in all subjects with a sector localization protocol whose difficulty is to be adjusted to the localization ability of the subject. This protocol reduced by one-third to one-half the time required to complete the assessment of the localization ability.     

Should a hearing aid in the contralateral ear be recommended for children with a unilateral cochlear implant?

OBJECTIVES: To predict bimodal benefit before cochlear implantation, we compared the performances of participants with bimodal fitting and with a cochlear implant alone on speech perception tests. METHODS: Twenty-two children with a cochlear implant in one ear and a hearing aid in the other (bimodal fitting) were included. Several aided and unaided average hearing thresholds and the aided word recognition score of the hearing aid ear were related to the bimodal benefit on a phoneme recognition test in quiet and in noise. Results with bimodal fitting were compared to results with the cochlear implant alone on a phoneme recognition test in quiet and in noise. RESULTS: No relationship was found between any of the hearing thresholds or the aided phoneme recognition score of the hearing aid ear and the bimodal benefit on the phoneme recognition tests. At the group level, the bimodal scores on the phoneme recognition tests in quiet and in noise were significantly better than the scores with the cochlear implant alone. CONCLUSIONS: Preoperatively available audiometric parameters are not reliable predictors of bimodal benefit in candidates for cochlear implantation. Children with unilateral implants benefit from bimodal fitting on speech tests. This improvement in performance warrants the recommendation of bimodal fitting even when bimodal benefit cannot be predicted.     

Binaural-bimodal fitting or bilateral implantation for managing severe to profound deafness: a review

There are now many recipients of unilateral cochlear implants who have usable residual hearing in the non-implanted ear. To avoid auditory deprivation and to provide binaural hearing, a hearing aid or a second cochlear implant can be fitted to that ear. This article addresses the question of whether better binaural hearing can be achieved with binaural/bimodal fitting (combining a cochlear implant and a hearing aid in opposite ears) or bilateral implantation. In the first part of this article, the rationale for providing binaural hearing is examined. In the second part, the literature on the relative efficacy of binaural/bimodal fitting and bilateral implantation is reviewed. Most studies on comparing either mode of bilateral stimulation with unilateral implantation reported some binaural benefits in some test conditions on average but revealed that some individuals benefited, whereas others did not. There were no controlled comparisons between binaural/bimodal fitting and bilateral implantation and no evidence to support the efficacy of one mode over the other. In the third part of the article, a crossover trial of two adults who had binaural/bimodal fitting and who subsequently received a second implant is reported. The findings at 6 and 12 months after they received their second implant indicated that binaural function developed over time, and the extent of benefit depended on which abilities were assessed for the individual. In the fourth and final parts of the article, clinical issues relating to candidacy for binaural/ bimodal fitting and strategies for bimodal fitting are discussed with implications for future research.     

Assessing binaural/bimodal advantages using auditory event-related potentials in subjects with cochlear implants

Objective

To assess the advantage of binaural and bimodal hearing for subjects with cochlear implant (CI) using auditory event-related potentials as well as speech perception tests.

Subjects and methods

The subjects comprised four binaural CI users (CI/CI group) and eleven bimodal CI users, who wore a hearing aid (HA) contralaterally (CI/HA group). All subjects had used binaural or bimodal fitting for over 6 months. Their speech perception was examined in a quiet environment using monosyllabic words. Late cortical waves were measured while subjects were engaged in an oddball task of 1 kHz frequent and 2 kHz rare tone stimuli. The latencies of event-related potential (N1, N2, P3) were compared for monaural, binaural, and bimodal hearing conditions.

Results

Significantly (p < 0.01, paired t-test) better speech perception for monosyllabic words was found for both binaural and bimodal hearing than monaural hearing. The latency of N1 did not significantly change for either binaural or bimodal hearing. On the other hand, the latency of N2 was significantly (p < 0.01, paired t-test) shorter for binaural and bimodal hearing than for monaural hearing. The latency of P3 was shorter for binaural and bimodal hearing than monaural hearing in all subjects, and the difference was statistically significant in both CI/CI and CI/HA groups (p < 0.01, paired t-test).

Conclusions

Better speech perception was obtained for binaural and bimodal hearing than for monaural hearing in CI subjects. The results obtained in the comparison of P3 latency agreed with that of speech perception. Thus, using bilateral hearing devices is recommended for CI subjects. We also found that event-related potentials were useful as an objective tool to assess the advantage of binaural and bimodal hearing for CI subjects.     

Performance in children with hearing aids or cochlear implants: bilateral stimulation and binaural hearing

It is well recognised that normal hearing people use their hearing in both ears to locate sounds and to understand speech in complex listening conditions. Whereas it is standard practice to provide two hearing aids to children with bilateral hearing loss, the situation with cochlear implantation is less certain. Questions remain as to what binaural aided functioning is possible for children who use a hearing aid and a cochlear implant in opposite ears (bimodal hearing). The first part of this paper draws on research at the National Acoustic Laboratories to show that children who used bimodal hearing devices obtained binaural advantages in localization. They could also take advantage of head shadow and binaural redundancy for speech intelligibility. The second part presents data showing that some hearing-impaired children may have binaural processing deficits even when bilateral stimulation is provided. Additional strategies may be necessary to develop or enable the use of binaural cues by these children.     

Contralateral hearing aid use in cochlear implanted patients: Multicenter study of bimodal benefit

Abstract Conclusion: The use of a hearing aid (HA) in combination with a cochlear implant (CI) significantly improved performance for speech perception in quiet, in noise, and for localization compared with monaural conditions. No significant differences in functional performance were observed following optimization of HA fitting. Objectives: To evaluate the binaural benefits derived from using a contralateral HA in conjunction with a CI in subjects with significant functional hearing in the nonimplanted ear and the effects of HA fitting optimization. Methods: Fifteen adult CI users, intra-subject controls, were enrolled in a prospective repeated-measure multicenter study. Evaluation of performance for speech understanding, localization, and subjective impressions was conducted before and following HA fitting optimization for CI alone, HA alone, and CI + HA. Results: For speech testing in quiet, bimodal scores were significantly better than for HA alone and CI alone conditions (p < 0.01). For speech and noise (S0N0) at 0° azimuth the scores were significantly better in the bimodal condition than for CI alone (p = 0.01), indicating binaural summation. When noise was presented to the HA side (S0NHA) bimodal scores were significantly better than for CI alone (p < 0.01 and p < 0.05, respectively), suggesting a significant binaural squelch effect. Sound localization ability was significantly improved in the bimodal condition compared with the CI alone condition (p = 0.002).     

双耳双模式助听儿童情感语调感知特征

目的探讨单侧人工耳蜗植入儿童对侧配戴助听器能否提升其情感语调识别能力,不同的情绪语调识别是否存在难度差异。方法选取35例(男15例,女20例)双耳双模式助听的重度、极重度感音神经性听力损失儿童,组内比较单侧人工耳蜗助听状态和双模式助听两种状态下儿童的情感语调识别特征。结果双耳双模式助听状态下听障儿童的语调得分极显著高于单侧人工耳蜗助听状态(P<0.01),识别率总体提升了16.65%。开心语调提升了20.59%,生气语调提升了19.21%,难过语调提升了13.23%。个体数据分析发现,有82.85%的儿童体现出双耳双模式优势。两种助听状态下,生气语调识别得分显著高于开心和难过(P<0.05),双耳双模式助听状态下,23.53%的儿童会将开心感知为难过语调,22.79%的儿童会将难过感知为开心语调。结论相比于单侧人工耳蜗植入,儿童通过双模式助听可以获得情感语调感知优势;两种助听模式下,生气语调的识别均比开心和难过容易,开心和难过语调容易混淆。频率变化可能是儿童感知情感语调的重要线索,提示在康复训练中应予以重视。     

Two Ears Are Not Always Better than One: Mandatory Vowel Fusion Across Spectrally Mismatched Ears in Hearing-Impaired Listeners

Hearing loss and auditory prostheses can alter auditory processing by inducing large pitch mismatches and broad pitch fusion between the two ears. Similar to integration of incongruent inputs in other sensory modalities, the mismatched, fused pitches are often averaged across ears for simple stimuli. Here, we measured parallel effects on complex stimulus integration using a new technique based on vowel classification in five bilateral hearing aid users and eight bimodal cochlear implant users. Continua between five pairs of synthetic vowels were created by varying the first formant spectral peak while keeping the second formant constant. Comparison of binaural and monaural vowel classification functions for each vowel pair continuum enabled visualization of the following frequency-dependent integration trends: (1) similar monaural and binaural functions, (2) ear dominance, (3) binaural averaging, and (4) binaural interference. Hearing aid users showed all trends, while bimodal cochlear implant users showed mostly ear dominance or interference. Interaural pitch mismatches, frequency ranges of binaural pitch fusion, and the relative weightings of pitch averaging across ears were also measured using tone and/or electrode stimulation. The presence of both large interaural pitch mismatches and broad pitch fusion was not sufficient to predict vowel integration trends such as binaural averaging or interference. The way that pitch averaging was weighted between ears also appears to be important for determining binaural vowel integration trends. Abnormally broad spectral fusion and the associated phoneme fusion across mismatched ears may underlie binaural speech perception interference observed in hearing aid and cochlear implant users.     

Binaural redundancy and inter-aural time difference cues for patients wearing a cochlear implant and a hearing aid in opposite ears

We investigated speech perception advantages arising from the use of inter-aural time difference cues, and from the provision of redundant information by the use of a hearing aid contralateral to a cochlear implant (bimodal hearing devices). Thirty-eight subjects (14 normally hearing and 23 hearing-impaired) participated in this study. The effect of binaural redundancy was assessed by comparing the signal-to-noise ratio (SNR) required for 50% correct identification of sentences in noise when listening monaurally to that when listening binaurally. The use of inter-aural time difference cues was determined by comparing the binaural SNRs obtained with or without a noise delay of 700 micros between ears. Results indicated adults who used bimodal hearing devices benefited from binaural redundancy, but children did not. Whereas normally hearing subjects used inter-aural time difference cues to improve speech perception in noise, neither adults nor children who used bimodal hearing devices were able to do so.     

Comparison of speech perception between monaural and binaural hearing in cochlear implant patients

Objective To assess the advantages of binaural hearing for cochlear implant (CI) users using a hearing aid (HA) for the contralateral ear.

Material and Methods The subjects comprised 3 males and 3 females (age range 48–84 years). All of them had been using a CI and HA for >6 months. Their speech perception was examined in quiet using monosyllables and Japanese Hearing in Noise Test (J-HINT) sentences. Speech perception in noise was examined using J-HINT sentences. Late cortical waves were measured while subjects listened to 1 kHz frequent and 2 kHz target tone stimuli. The latency of the event-related potential (P300) wave was compared for monaural and binaural hearing conditions.

Results Three subjects showed significantly better results for binaural than monaural (CI alone) hearing for monosyllables and HINT sentences (p<0.05; paired t-test). Subjects with better speech perception had been using an HA for longer than those with poor performance (18.3 vs 4.0 years). The overall average score was better for binaural than monaural hearing in the speech perception test under quiet and noisy conditions. Comparison of the latency of the P300 wave under monaural and binaural hearing conditions showed a significantly shorter latency for the latter (p=0.02; paired t-test).

Conclusion Although the use of an HA alone showed marginal benefit for CI users, binaural hearing (CI + HA) resulted in a significant improvement in speech perception under various circumstances.     

Simultaneous bilateral cochlear implantation in adults: a multicenter clinical study

OBJECTIVE: To determine the efficacy of "simultaneous" bilateral cochlear implantation (both implants placed during a single surgical procedure) by comparing bilateral and unilateral implant use in a large number of adult subjects tested at multiple sites. DESIGN: Prospective study of 37 adults with postlinguistic onset of bilateral, severe to profound sensorineural hearing loss. Performance with the bilateral cochlear implants, using the same speech processor type and speech processing strategy, was compared with performance using the left implant alone and the right implant alone. Speech understanding in quiet (CNCs and HINT sentences) and in noise (BKB-SIN Test) were evaluated at several postactivation time intervals, with speech presented at 0 degrees azimuth, and noise at either 0 degrees , 90 degrees right, or 90 degrees left in the horizontal plane. APHAB questionnaire data were collected after each subject underwent a 3-wk "bilateral deprivation" period, during which they wore only the speech processor that produced the best score during unilateral testing, and also after a period of listening again with the bilateral implants. RESULTS: By 6-mo postactivation, a significant advantage for speech understanding in quiet was found in the bilateral listening mode compared with either unilateral listening modes. For speech understanding in noise, the largest and most robust bilateral benefit was when the subject was able to take advantage of the head shadow effect; i.e., results were significantly better for bilateral listening compared with the unilateral condition when the ear opposite to the side of the noise was added to create the bilateral condition. This bilateral benefit was seen on at least one of the two unilateral ear comparisons for nearly all (32/34) subjects. Bilateral benefit was also found for a few subjects in spatial configurations that evaluated binaural redundancy and binaural squelch effects. A subgroup of subjects who had asymmetrical unilateral implant performances were, overall, similar in performance to subjects with symmetrical hearing. The questionnaire data indicated that bilateral users perceive their own performance to be better with bilateral cochlear implants than when using a single device. CONCLUSIONS: Findings with a large patient group are in agreement with previous reports on smaller groups, showing that, overall, bilateral implantation offers the majority of patients advantages when listening in simulated adverse conditions.     

Cortical auditory evoked responses from an implanted ear after 50 years of profound unilateral deafness

A male with unilateral deafness in the right ear since 8 years of age developed a sudden hearing loss in the left ear at age 63. A hearing aid was fitted in the left ear with limited benefit. The right ear received a cochlear implant (CI) 20 months later. Cortical auditory evoked potentials (CAEPs) and speech recognition scores (SRS) were measured in free-field three, six and nine months after implantation with the hearing aid alone, CI alone and bimodal condition (hearing aid and CI together). Three months after implantation the cortical responses for the two ears were similar, despite more than 50 years of unilateral auditory deprivation. CAEPs measured over time show evidence of binaural interaction and improvements in SRS.     

Advantages of binaural hearing provided through bimodal stimulation via a cochlear implant and a conventional hearing aid: a 6-month comparative study

CONCLUSIONS: Our study data demonstrate the additional benefit derived from continued use of a contralateral hearing aid (HA) post-cochlear implantation for speech recognition ability in quiet and in noise. Postoperative bimodal stimulation is recommended for all subjects who show some speech recognition ability in the contralateral ear as it may offer binaural listening advantages in various listening situations encountered in everyday life. OBJECTIVES: To assess the benefits derived from bimodal stimulation for experienced HA users implanted with a cochlear implant (CI) (score=20% in disyllabic test). The correlation between pre- and postoperative performance on speech perception measures was examined to determine additional criteria for recommending bimodal stimulation postoperatively. MATERIAL AND METHODS: A within-subject repeated-measures design was used, with each subject acting as their own control. Assessments were carried out preoperatively in aided monaural and best-aided conditions and at 6 months postoperatively in CI-alone, contralateral HA-alone and bimodal listening conditions. Speech recognition using Spanish words and sentences materials was assessed at conversational level and for soft speech in quiet. Speech comprehension in noise was assessed using word materials at a signal:noise ratio of +10, for coincident speech in noise and for spatially separated speech in noise. Twelve adult native Spanish subjects with a severe-to-profound hearing impairment who were experienced with optimally fitted conventional amplification and who displayed suboptimal speech understanding preoperatively were enrolled in the study. Preoperatively, conventional amplification was worn by five subjects binaurally and by seven monaurally. RESULTS: Postoperatively, superior speech recognition ability in quiet and in noise for disyllabic words was achieved using bimodal stimulation in comparison to performance for either monaural aided condition. Mean improvement in speech recognition in the bimodal condition was significant over performance in the CI-alone condition for disyllabic words in quiet at 70 (p=0.006) and 55 dB SPL (p=0.028), for disyllabic words in noise at +10 dB with speech and noise spatially separated with the noise source closest to the contralateral HA (S0NHA) (p=0.0005) and when the noise source was closest to the CI ear (S0NCI) (p=0.002). When testing word recognition in noise with speech and noise sources coincident in space, word scores were superior in the bimodal condition relative to the CI-alone condition but this improvement was not significant (p=0.07). The advantages of bimodal stimulation included significant effects of binaural summation in quiet and significant binaural squelch effects in both the S0NHA and S0NCI test conditions. All subjects showed superior performance in the binaural situation postoperatively relative to the best-aided condition preoperatively for one or more test situations.