Benefits of Cochlear Implantation for Single-Sided Deafness: Data From the House Clinic-University of Southern California-University of California, Los Angeles Clinical Trial.

OBJECTIVES: Cochlear implants (CIs) have been shown to benefit patients with single-sided deafness (SSD) in terms of tinnitus reduction, localization, speech understanding, and quality of life (QoL). While previous studies have shown cochlear implantation may benefit SSD patients, it is unclear which point of comparison is most relevant: baseline performance before implantation versus performance with normal-hearing (NH) ear after implantation. In this study, CI outcomes were assessed in SSD patients before and up to 6 mo postactivation. Benefits of cochlear implantation were assessed relative to binaural performance before implantation or relative to performance with the NH ear alone after implantation. DESIGN: Here, we report data for 10 patients who completed a longitudinal, prospective, Food and Drug Administration-approved study of cochlear implantation for SSD patients. All subjects had severe to profound unilateral hearing loss in one ear and normal hearing in the other ear. All patients were implanted with the MED-EL CONCERTO Flex 28 device. Speech understanding in quiet and in noise, localization, and tinnitus severity (with the CI on or off) were measured before implantation (baseline) and at 1, 3, 6 mo postactivation of the CI processor. Performance was measured with both ears (binaural), the CI ear alone, and the NH ear alone (the CI ear was plugged and muffed). Tinnitus severity, dizziness severity, and QoL were measured using questionnaires administered before implantation and 6 mo postactivation. RESULTS: Significant CI benefits were observed for tinnitus severity, localization, speech understanding, and QoL. The degree and time course of CI benefit depended on the outcome measure and the reference point. Relative to binaural baseline performance, significant and immediate (1 mo postactivation) CI benefits were observed for tinnitus severity and speech performance in noise, but localization did not significantly improve until 6 mo postactivation; questionnaire data showed significant improvement in QoL 6 mo postactivation. Relative to NH-only performance after implantation, significant and immediate benefits were observed for tinnitus severity and localization; binaural speech understanding in noise did not significantly improve during the 6-mo study period, due to variability in NH-only performance. There were no correlations between behavioral and questionnaire data, except between tinnitus visual analog scale scores at 6 mo postactivation and Tinnitus Functional Index scores at 6 mo postactivation. CONCLUSIONS: The present behavioral and subjective data suggest that SSD patients greatly benefit from cochlear implantation. However, to fully understand the degree and time course of CI benefit, the outcome measure and point of comparison should be considered. From a clinical perspective, binaural baseline performance is a relevant point of comparison. The lack of correlation between behavioral and questionnaire data suggest that represent independent measures of CI benefit for SSD patients.

Initial Results of a Safety and Feasibility Study of Auditory Brainstem Implantation in Congenitally Deaf Children.

OBJECTIVE: To determine the safety and feasibility of the auditory brainstem implant (ABI) in congenitally deaf children with cochlear aplasia and/or cochlear nerve deficiency. STUDY DESIGN: Phase I feasibility clinical trial of surgery in 10 children, ages 2 to 5 years, over a 3-year period. SETTING: Tertiary children's hospital and university-based pediatric speech/language/hearing center. INTERVENTION(S): ABI implantation and postsurgical programming. MAIN OUTCOME MEASURE(S): The primary outcome measure is the number and type of adverse events during ABI surgery and postsurgical follow-up, including behavioral mapping of the device. The secondary outcome measure is access to and early integration of sound. RESULTS: To date, nine children are enrolled. Five children have successfully undergone ABI surgery and postoperative behavioral programming. Three children were screen failures, and one child is currently undergoing candidacy evaluation. Expected adverse events have been documented in three of the five children who received the ABI. One child experienced a cerebral spinal fluid leak, which resolved with lumbar drainage. One child demonstrated vestibular side effects during device programming, which resolved by deactivating one electrode. One child experienced postoperative vomiting resulting in an abdominal radiograph. Four children have completed their 1-year follow-up and have speech detection thresholds of 30 to 35 dB HL. Scores on the IT-MAIS/MAIS range from 8 to 31 (out of a total of 40), and the children are demonstrating some ability to discriminate between closed-sets words that differ by number of syllables (pattern perception). CONCLUSION: ABI surgery and device activation seem to be safe and feasible in this preliminary cohort.

Is Birdsong More Like Speech or Music?

Music and speech share many acoustic cues but not all are equally important. For example, harmonic pitch is essential for music but not for speech. When birds communicate is their song more like speech or music? A new study contrasting pitch and spectral patterns shows that birds perceive their song more like humans perceive speech.

Auditory implant research at the House Ear Institute 1989-2013.

The House Ear Institute (HEI) had a long and distinguished history of auditory implant innovation and development. Early clinical innovations include being one of the first cochlear implant (CI) centers, being the first center to implant a child with a cochlear implant in the US, developing the auditory brainstem implant, and developing multiple surgical approaches and tools for Otology. This paper reviews the second stage of auditory implant research at House - in-depth basic research on perceptual capabilities and signal processing for both cochlear implants and auditory brainstem implants. Psychophysical studies characterized the loudness and temporal perceptual properties of electrical stimulation as a function of electrical parameters. Speech studies with the noise-band vocoder showed that only four bands of tonotopically arrayed information were sufficient for speech recognition, and that most implant users were receiving the equivalent of 8-10 bands of information. The noise-band vocoder allowed us to evaluate the effects of the manipulation of the number of bands, the alignment of the bands with the original tonotopic map, and distortions in the tonotopic mapping, including holes in the neural representation. Stimulation pulse rate was shown to have only a small effect on speech recognition. Electric fields were manipulated in position and sharpness, showing the potential benefit of improved tonotopic selectivity. Auditory training shows great promise for improving speech recognition for all patients. And the Auditory Brainstem Implant was developed and improved and its application expanded to new populations. Overall, the last 25 years of research at HEI helped increase the basic scientific understanding of electrical stimulation of hearing and contributed to the improved outcomes for patients with the CI and ABI devices. This article is part of a Special Issue entitled .

The development of auditory perception in children after auditory brainstem implantation.

Auditory brainstem implants (ABIs) can provide useful auditory perception and language development in deaf children who are not able to use a cochlear implant (CI). We prospectively followed up a consecutive group of 64 deaf children up to 12 years following ABI surgery. The etiology of deafness in these children was: cochlear nerve aplasia in 49, auditory neuropathy in 1, cochlear malformations in 8, bilateral cochlear postmeningitic ossification in 3, neurofibromatosis type 2 in 2, and bilateral cochlear fractures due to a head injury in 1. Thirty-five children had other congenital nonauditory disabilities. Twenty-two children had previous CIs with no benefit. Fifty-eight children were fitted with the Cochlear 24 ABI device and 6 with the MedEl ABI device, and all children followed the same rehabilitation program. Auditory perceptual abilities were evaluated on the Categories of Auditory Performance (CAP) scale. No child was lost to follow-up, and there were no exclusions from the study. All children showed significant improvement in auditory perception with implant experience. Seven children (11%) were able to achieve the highest score on the CAP test; they were able to converse on the telephone within 3 years of implantation. Twenty children (31.3%) achieved open set speech recognition (CAP score of 5 or greater) and 30 (46.9%) achieved a CAP level of 4 or greater. Of the 29 children without nonauditory disabilities, 18 (62%) achieved a CAP score of 5 or greater with the ABI. All children showed continued improvements in auditory skills over time. The long-term results of ABI surgery reveal significant auditory benefit in most children, and open set auditory recognition in many.

Training improves cochlear implant rate discrimination on a psychophysical task.

The purpose of this study was to determine the extent to which cochlear implant (CI) rate discrimination can be improved through training. Six adult CI users took part in a study that included 32 h of training and assessment on rate discrimination measures. Rate difference limens (DLs) were measured from 110 to 3520 Hz in octave steps using 500 ms biphasic pulse trains; the target and standard stimuli were loudness-balanced with the target always at an adaptively lower rate. DLs were measured at four electrode positions corresponding to basal, mid-basal, mid-apical, and apical locations. Procedural variations were implemented to determine if rate discrimination was impacted by random variations in stimulus amplitude or by amplitude modulation. DLs improved by more than a factor of 2 across subjects, electrodes, and standard rates. Factor analysis indicated that the effect of training was comparable for all electrodes and standard rates tested. Neither level roving nor amplitude modulation had a significant effect on rate DLs. In conclusion, the results demonstrate that training can significantly improve CI rate discrimination on a psychophysical task.

Improving speech perception in noise with current focusing in cochlear implant users.

Cochlear implant (CI) users typically have excellent speech recognition in quiet but struggle with understanding speech in noise. It is thought that broad current spread from stimulating electrodes causes adjacent electrodes to activate overlapping populations of neurons which results in interactions across adjacent channels. Current focusing has been studied as a way to reduce spread of excitation, and therefore, reduce channel interactions. In particular, partial tripolar stimulation has been shown to reduce spread of excitation relative to monopolar stimulation. However, the crucial question is whether this benefit translates to improvements in speech perception. In this study, we compared speech perception in noise with experimental monopolar and partial tripolar speech processing strategies. The two strategies were matched in terms of number of active electrodes, microphone, filterbanks, stimulation rate and loudness (although both strategies used a lower stimulation rate than typical clinical strategies). The results of this study showed a significant improvement in speech perception in noise with partial tripolar stimulation. All subjects benefited from the current focused speech processing strategy. There was a mean improvement in speech recognition threshold of 2.7 dB in a digits in noise task and a mean improvement of 3 dB in a sentences in noise task with partial tripolar stimulation relative to monopolar stimulation. Although the experimental monopolar strategy was worse than the clinical, presumably due to different microphones, frequency allocations and stimulation rates, the experimental partial-tripolar strategy, which had the same changes, showed no acute deficit relative to the clinical.

Improving virtual channel discrimination in a multi-channel context.

Improving spectral resolution in cochlear implants is key to improving performance in difficult listening conditions (e.g. speech in noise, music, etc.). Current focusing might reduce channel interaction, thereby increasing spectral resolution. Previous studies have shown that combining current steering and current focusing reduces spread of excitation and improves virtual channel discrimination in a single-channel context. It is unclear whether the single-channel benefits from current focusing extend to a multi-channel context, in which the physical and perceptual interference of multiple stimulated channels might overwhelm the benefits of improved spectral resolution. In this study, signal discrimination was measured with and without current focusing, in the presence of competing stimuli on nearby electrodes. Results showed that signal discrimination was consistently better with current focusing than without, regardless of the amplitude of the competing stimuli. Therefore, combining current steering and current focusing may provide more effective spectral cues than are currently available.

Histopathological analysis of a 15-year user of an auditory brainstem implant.

Auditory brainstem implants (ABIs) can provide highly beneficial hearing sensations to individuals deafened by bilateral vestibular schwannomas (neurofibromatosis type 2). Relatively little is known about the status of stimulated neurons after long-term ABI use. Direct examination of the cochlear nuclear complex (CN) of one 5-year ABI user indicated no deleterious effect. Recently, we examined the brainstem of a patient who used his ABI daily for 15 years with excellent performance. There was good preservation of CN cell size, morphology, and packing density, a very favorable sign considering that a number of infants are now receiving ABIs.

Advances in auditory prostheses.

PURPOSE OF REVIEW: Auditory prostheses use electric currents on multiple electrodes to stimulate auditory neurons and recreate auditory sensations in deaf people. Cochlear implants have restored hearing in more than 200  000 deaf adults and children to a level that allows most to understand speech. Here we review the reasons underlying these results and describe new directions in restoring hearing to additional patient populations and the design of new devices. RECENT FINDINGS: From their early development about 50 years ago, cochlear implants have been well received and beneficial to people who had lost their hearing. Although those first implants did not allow high levels of speech understanding, they provided auditory information that worked synergistically with lip reading to improve communication. Present day cochlear implants provide excellent speech understanding in children and in postlingually deafened adults. Research is focused on improved signal processing and new electrode designs. Electric stimulation of the auditory brainstem can also produce excellent hearing in some children and adults. SUMMARY: Auditory prostheses, both at the level of the sensory nerve and at the brainstem, can restore patterns of neural activation that are sufficient for high levels of speech understanding. These prostheses are not only clinically successful but also important tools for understanding sensory processing in the brain.

Estimated net saving to society from cochlear implantation in infants: a preliminary analysis.

OBJECTIVES/HYPOTHESIS: Although it is clear that cochlear implants (CIs) are highly cost-effective in adults and children, the possible additional economic benefit of implantation at younger ages has to be fully established to verify whether the costs and outcomes of CIs differ between infants and older children. STUDY DESIGN: Retrospective cohort study. METHODS: Comprehensive data of CI costs were obtained in four groups of children (age 2-11, 12-23, 24-35, and 72-83 months) from parent questionnaires, national healthcare and educational systems, and retail prices for materials used. Outcomes are compared in terms of receptive language level (Peabody Picture Vocabulary Test-Revised [PPVT-R]), with follow-up to the chronological age of 10 years. RESULTS: Implantation in infants was associated with a lower total cost for the first 10 years of life. The net savings to society ranged from around 21,000€ in the two younger classes to more than 35,000€ when comparing infants against children in the oldest group. When implantation was delayed, family costs played an important role in the increase in expenses. Children in the 2- to 11-month group scored significantly better at the PPVT-R than those in the other age groups (P < .05, P < .01, and P < .001, respectively; Dunn's test) at 10 years of age. The cost per 1-year gain in vocabulary age at the PPVT-R showed a substantial difference between the youngest and oldest age groups (13,266€/year, 17,719€/year, 20,029€/year, and 28,042€/year, respectively). CONCLUSIONS: CIs for patients under 1 year of age afford significantly improved performance and a net savings to society.

Infants versus older children fitted with cochlear implants: performance over 10 years.

OBJECTIVES: To investigate the efficacy of cochlear implants (CIs) in infants versus children operated at later age in term of spoken language skills and cognitive performances. METHOD: The present prospective cohort study focuses on 19 children fitted with CIs between 2 and 11 months (X=6.4 months; SD=2.8 months). The results were compared with two groups of children implanted at 12-23 and 24-35 months. Auditory abilities were evaluated up to 10 years of CI use with: Category of Auditory Performance (CAP); Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS); Peabody Picture Vocabulary Test (PPVT-R); Test of Reception of Grammar (TROG) and Speech Intelligibility Rating (SIR). Cognitive evaluation was performed using selected subclasses from the Griffiths Mental Development Scale (GMDS, 0-8 years of age) and Leiter International Performance Scale-Revised (LIPS-R, 8-13 years of age). RESULTS: The infant group showed significantly better results at the CAP than the older children from 12 months to 36 months after surgery (p<.05). Infants PPVT-R outcomes did not differ significantly from normal hearing children, whereas the older age groups never reached the values of normal hearing peers even after 10 years of CI use. TROG outcomes showed that infants developed significantly better grammar skills at 5 and 10 years of follow up (p<.001). Scores for the more complex subtests of the GMDS and LIPS-R were significantly higher in youngest age group (p<.05). CONCLUSION: This study demonstrates improved auditory, speech language and cognitive performances in children implanted below 12 months of age compared to children implanted later.

Effect of stimulation rate on cochlear implant users' phoneme, word and sentence recognition in quiet and in noise.

High stimulation rates in cochlear implants (CI) offer better temporal sampling, can induce stochastic-like firing of auditory neurons and can increase the electric dynamic range, all of which could improve CI speech performance. While commercial CI have employed increasingly high stimulation rates, no clear or consistent advantage has been shown for high rates. In this study, speech recognition was acutely measured with experimental processors in 7 CI subjects (Clarion CII users). The stimulation rate varied between (approx.) 600 and 4800 pulses per second per electrode (ppse) and the number of active electrodes varied between 4 and 16. Vowel, consonant, consonant-nucleus-consonant word and IEEE sentence recognition was acutely measured in quiet and in steady noise (+10 dB signal-to-noise ratio). Subjective quality ratings were obtained for each of the experimental processors in quiet and in noise. Except for a small difference for vowel recognition in quiet, there were no significant differences in performance among the experimental stimulation rates for any of the speech measures. There was also a small but significant increase in subjective quality rating as stimulation rates increased from 1200 to 2400 ppse in noise. Consistent with previous studies, performance significantly improved as the number of electrodes was increased from 4 to 8, but no significant difference showed between 8, 12 and 16 electrodes. Altogether, there was little-to-no advantage of high stimulation rates in quiet or in noise, at least for the present speech tests and conditions.

Current focusing sharpens local peaks of excitation in cochlear implant stimulation.

Cochlear implant (CI) users' spectral resolution is limited by the number of implanted electrodes, interactions between the electrodes, and the underlying neural population. Current steering has been proposed to increase the number of spectral channels beyond the number of physical electrodes, however, electric field interactions may limit CI users' access to current-steered virtual channels (VCs). Current focusing (e.g tripolar stimulation) has been proposed to reduce current spread and thereby reduce interactions. In this study, current steering and current focusing were combined in a four-electrode stimulation pattern, i.e quadrupolar virtual channels (QPVCs). The spread of excitation was measured and compared between QPVC and Monopolar VC (MPVC) stimuli using a forward masking task. Results showed a sharper peak in the excitation pattern and reduced spread of masking for QPVC stimuli. Results from the forward masking study were compared with a previous study measuring VC discrimination ability and showed a weak relationship between spread of excitation and VC discriminability. The results suggest that CI signal processing strategies that utilize both current steering and current focusing might increase CI users' functional spectral resolution by transmitting more channels and reducing channel interactions.

Complications in auditory brainstem implant surgery in adults and children.

OBJECTIVE: Surgery for hearing restoration with auditory brainstem implantation (ABI) in patients with neurofibromatosis type 2 (NF2) is considered safe, as no increase in postoperative complications related to surgery or device implantation has been observed. Over the last 10 years, we have extended the use of ABI to nontumor (NT) adults and children with cochlear or cochlear nerve malfunctions who would not or did not benefit from a cochlear implant (CI). This article examines the complications encountered in ABI surgery in all patient groups. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: : One hundred fourteen ABI operations were performed in Verona (Italy) from 1997 to 2008 in 83 adults and 31 children. Thirty-six had NF2 (34 adults and 2 children), and 78 (49 adults and 29 children) had NT cochlear and cochlear nerve disorders. INTERVENTION: A retrosigmoid-transmeatal approach was used in the NF2 cases, and a simple retrosigmoid approach was used in the NT patients. MAIN OUTCOME MEASURES: Surgical complications are tabulated according to standard reporting categories and are presented separately and analyzed statistically for NF2, NT adults, and NT children. Complication rates are compared with those of CI and microvascular decompression surgery. RESULTS: ABI surgery has a very low major complication rate, particularly in non-NF2 patients. Minor complications were easily controlled with complete resolution in all cases. Although the potential complications of intradural ABI implantation are more severe than those of a transmastoid approach for CIs, the actual observed complication rates in ABI candidates without NF2 tumors are comparable to those of CI surgery in both adults and children. CONCLUSION: This study demonstrates that the ABI is a safe procedure when performed by an experienced surgical and rehabilitation team, and its benefits can be extended to a larger population of deaf patients.

Melodic contour identification and music perception by cochlear implant users.

Research and outcomes with cochlear implants (CIs) have revealed a dichotomy in the cues necessary for speech and music recognition. CI devices typically transmit 16-22 spectral channels, each modulated slowly in time. This coarse representation provides enough information to support speech understanding in quiet and rhythmic perception in music, but not enough to support speech understanding in noise or melody recognition. Melody recognition requires some capacity for complex pitch perception, which in turn depends strongly on access to spectral fine structure cues. Thus, temporal envelope cues are adequate for speech perception under optimal listening conditions, while spectral fine structure cues are needed for music perception. In this paper, we present recent experiments that directly measure CI users' melodic pitch perception using a melodic contour identification (MCI) task. While normal-hearing (NH) listeners' performance was consistently high across experiments, MCI performance was highly variable across CI users. CI users' MCI performance was significantly affected by instrument timbre, as well as by the presence of a competing instrument. In general, CI users had great difficulty extracting melodic pitch from complex stimuli. However, musically experienced CI users often performed as well as NH listeners, and MCI training in less-experienced subjects greatly improved performance. With fixed constraints on spectral resolution, such as occurs with hearing loss or an auditory prosthesis, training and experience can provide considerable improvements in music perception and appreciation.

Progress in restoration of hearing with the auditory brainstem implant.

Fifty years ago auditory scientists were very skeptical about the potential of new prosthetic approaches that electrically stimulated the auditory nerve, the cochlear nuclei (CN), and the inferior colliculus (IC). In those decades, the basilar membrane was considered to play a fundamental and irreplaceable role as a fine spectrum analyzer in hearing physiology, and therefore it was thought that electrical stimulation of the auditory system would have never produced functionally useful hearing. Over the last 30 years, cochlear implants (CIs) have improved steadily to the point where the average sentence recognition with modern multichannel devices is better than 90% correct. More recently, similar performance has been observed with electric stimulation of the brainstem with auditory brainstem implants (ABIs). However, it is clear that to fully understand hearing and to design the next generation of prosthetic devices we must better understand the ear-brain relationship. Indeed some aspects of hearing do not require the intricate complexities of cochlear physiological responses, while other auditory tasks rely critically on specialized details of cochlear processing. The progress in electrical stimulation of the central auditory system requires us to reconsider the patient selection criteria for different implant devices, in particular to evaluate the possibility of ABIs for etiologies with poor outcomes with CIs. In the present review, the latest outcomes in restoration of hearing with ABI are presented. New guidelines are proposed for device selection for different etiologies and future research is suggested to further refine the process of matching an individual patient to the most appropriate implant device.