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1.  Fully implantable Otologics MET Carina™ device for the treatment of sensorineural hearing loss. Preliminary surgical and clinical results 
Summary
Middle ear implants overcome some of the common problems of conventional hearing aid technology, such as feedback, signal distortion, ear canal occlusion and associated issues. The Otologics MET Carina™, Boulder, CO, USA, is a fully implantable hearing prosthesis designed to address the amplification needs of adults (> 18 years of age), with moderate to severe sensorineural hearing loss and normal middle ears, providing a mechanical direct stimulation of middle ear ossicles. Recently, it has been successfully used also in patients with conductive hearing loss. In the present report, personal surgical and clinical experience with the fully implantable Carina™ is described in 5 adults with moderate to severe sensorineural hearing loss, operated upon between November 2007 and May 2008 in the ENT Unit, University of Pisa. Mean follow-up was 10.2 months of device use (range 7-13). Surgery was performed under general anaesthesia, in ~3 hours, with no surgical complications in any of the patients. In these 5 cases, no significant post-operative variation was observed in hearing thresholds, either for air or bone conduction, indicating absence of surgical damage to the cochlea. All patients showed improvements in hearing thresholds, in free field and in speech perception abilities, with the device functioning, moreover, they reported subjective benefits. With regard to post-operative adverse effects, no cases of extrusion of the device, device failure, loss of external communication or increased charging times were observed. Problems of feedback noise occurred, which were resolved with minor fitting adjustments in 4 cases, while a second operation was required to change the microphone position in the other patient. The present results, in agreement with those reported in the literature, confirm that the Otologics MET Carina™ is viable treatment for moderate to severe sensorineural hearing loss and, in selected cases, may represent an alternative to conventional hearing aids.
PMCID: PMC2808684  PMID: 20111617
Sensorineural hearing loss; Middle ear implants
2.  Sequential Bilateral Cochlear Implantation in a Patient with Bilateral Meniere’s Disease 
This case study describes a 45 year old female with bilateral, profound sensorineural hearing loss due to Meniere’s disease. She received her first cochlear implant in the right ear in 2008 and the second cochlear implant in the left ear in 2010. The case study examines the enhancement to speech recognition, particularly in noise, provided by bilateral cochlear implants.
Speech recognition tests were administered prior to obtaining the second implant and at a number of test intervals following activation of the second device. Speech recognition in quiet and noise as well as localization abilities were assessed in several conditions to determine bilateral benefit and performance differences between ears. The results of the speech recognition testing indicated a substantial improvement in the patient’s ability to understand speech in noise and her ability to localize sound when using bilateral cochlear implants compared to using a unilateral implant or an implant and a hearing aid. In addition, the patient reported considerable improvement in her ability to communicate in daily life when using bilateral implants versus a unilateral implant.
This case suggests that cochlear implantation is a viable option for patients who have lost their hearing to Meniere’s disease even when a number of medical treatments and surgical interventions have been performed to control vertigo. In the case presented, bilateral cochlear implantation was necessary for this patient to communicate successfully at home and at work.
doi:10.3766/jaaa.23.4.4
PMCID: PMC3431798  PMID: 22463939
Cochlear implant; hearing aid; Meniere’s disease; sensorineural hearing loss; speech recognition; vertigo
3.  Testing a Method for Quantifying the Output of Implantable Middle Ear Hearing Devices 
Audiology & neuro-otology  2007;12(4):265-276.
This report describes tests of a standard practice for quantifying the performance of implantable middle ear hearing devices (also known as implantable hearing aids). The standard and these tests were initiated by the Food and Drug Administration of the United States Government. The tests involved measurements on two hearing devices, one commercially available and the other home built, that were implanted into ears removed from human cadavers. The tests were conducted to investigate the utility of the practice and its outcome measures: the equivalent ear canal sound pressure transfer function that relates electrically driven middle ear velocities to the equivalent sound pressure needed to produce those velocities, and the maximum effective ear canal sound pressure. The practice calls for measurements in cadaveric ears in order to account for the varied anatomy and function of different human middle ears.
doi:10.1159/000101474
PMCID: PMC2596735  PMID: 17406105
Implantable hearing aids; Middle ear transfer function; Sound-induced stapes velocity
4.  Cochlear Implantation in Adults with Asymmetric Hearing Loss 
Ear and Hearing  2012;33(4):521-533.
Objective
Bilateral severe-to-profound sensorineural hearing loss is a standard criterion for cochlear implantation. Increasingly, patients are implanted in one ear and continue to use a hearing aid in the non-implanted ear to improve abilities such as sound localization and speech understanding in noise. Patients with severe-to-profound hearing loss in one ear and a more moderate hearing loss in the other ear (i.e., asymmetric hearing) are not typically considered candidates for cochlear implantation. Amplification in the poorer ear is often unsuccessful due to limited benefit, restricting the patient to unilateral listening from the better ear alone. The purpose of this study was to determine if patients with asymmetric hearing loss could benefit from cochlear implantation in the poorer ear with continued use of a hearing aid in the better ear.
Design
Ten adults with asymmetric hearing between ears participated. In the poorer ear, all participants met cochlear implant candidacy guidelines; seven had postlingual onset and three had pre/perilingual onset of severe-to-profound hearing loss. All had open-set speech recognition in the better hearing ear. Assessment measures included word and sentence recognition in quiet, sentence recognition in fixed noise (four-talker babble) and in diffuse restaurant noise using an adaptive procedure, localization of word stimuli and a hearing handicap scale. Participants were evaluated pre-implant with hearing aids and post-implant with the implant alone, the hearing aid alone in the better ear and bimodally (the implant and hearing aid in combination). Postlingual participants were evaluated at six months post-implant and pre/perilingual participants were evaluated at six and 12 months post-implant. Data analysis compared results 1) of the poorer hearing ear pre-implant (with hearing aid) and post-implant (with cochlear implant), 2) with the device(s) used for everyday listening pre- and post-implant and, 3) between the hearing aid-alone and bimodal listening conditions post-implant.
Results
The postlingual participants showed significant improvements in speech recognition after six months cochlear implant use in the poorer ear. Five postlingual participants had a bimodal advantage over the hearing aid-alone condition on at least one test measure. On average, the postlingual participants had significantly improved localization with bimodal input compared to the hearing aid-alone. Only one pre/perilingual participant had open-set speech recognition with the cochlear implant. This participant had better hearing than the other two pre/perilingual participants in both the poorer and better ear. Localization abilities were not significantly different between the bimodal and hearing aid-alone conditions for the pre/perilingual participants. Mean hearing handicap ratings improved post-implant for all participants indicating perceived benefit in everyday life with the addition of the cochlear implant.
Conclusions
Patients with asymmetric hearing loss who are not typical cochlear implant candidates can benefit from using a cochlear implant in the poorer ear with continued use of a hearing aid in the better ear. For this group of ten, the seven postlingually deafened participants showed greater benefits with the cochlear implant than the pre/perilingual participants; however, further study is needed to determine maximum benefit for those with early onset of hearing loss.
doi:10.1097/AUD.0b013e31824b9dfc
PMCID: PMC3383437  PMID: 22441359
Asymmetric hearing loss; Bilateral; Bimodal; Cochlear implant; Speech recognition
5.  Stem cells and molecular strategies to restore hearing 
Panminerva medica  2008;50(1):41-53.
Hearing loss is a costly and growing problem for the elderly population worldwide with millions of people being affected. There are currently two prosthetic devices available to minimize problems associated with the two forms of hearing loss: hearing aids that amplify sound to overcome middle ear based conductive hearing loss and cochlear implants that restore some hearing after neurosensory hearing loss. The current presentation provides information on the treatment of neurosensory hearing loss. Although the cochlear implant solution for neurosensory hearing loss is technologically advanced; it still provides only moderate hearing capacity in neurosensory deaf individuals. Inducible stem cells and molecular therapies are appealing alternatives to the cochlear implant and may provide more than a new form of treatment as they hold the promise for a cure. To this end, current insights into inducible stem cells that may provide cells for seeding the cochlea with the hope of new hair cell formation are being reviewed. Alternatively, similar to induction of stem cells, cells of the flat epithelium that remains after hair cell loss could be induced to proliferate and differentiate into hair cells. In either of these strategies, hair cell specific genes known to be essential for hair cell differentiation or maintenance such as ATOH1, POU4F3, GFI1, and miRNA-183 will be utilized with the hope of completely restoring hearing to all patients with hearing loss.
PMCID: PMC2610336  PMID: 18427387
Hearing loss; Stem cells; Gene therapy; Cochlear implants
6.  Bone Anchored Hearing Aid 
Executive Summary
Objective
The objective of this health technology policy assessment was to determine the effectiveness and cost-effectiveness of bone-anchored hearing aid (BAHA) in improving the hearing of people with conduction or mixed hearing loss.
The Technology
The (BAHA) is a bone conduction hearing device that includes a titanium fixture permanently implanted into the mastoid bone of the skull and an external percutaneous sound processor. The sound processor is attached to the fixture by means of a skin penetrating abutment. Because the device bypasses the middle ear and directly stimulates the cochlea, it has been recommended for individuals with conduction hearing loss or discharging middle ear infection.
The titanium implant is expected to last a lifetime while the external sound processor is expected to last 5 years. The total initial device cost is approximately $5,300 and the external sound processor costs approximately $3,500.
Review of BAHA by the Medical Advisory Secretariat
The Medical Advisory Secretariat’s review is a descriptive synthesis of findings from 36 research articles published between January 1990 and May 2002.
Summary of Findings
No randomized controlled studies were found. The evidence was derived from level 4 case series with relative small sample sizes (ranging from 30-188). The majority of the studies have follow-up periods of eight years or longer. All except one study were based on monaural BAHA implant on the side with the best bone conduction threshold.
Safety
Level 4 evidence showed that BAHA has been be implanted safely in adults and children with success rates of 90% or higher in most studies. No mortality or life threatening morbidity has been reported. Revision rates for tissue reduction or resiting were generally under 10% for adults but have been reported to be as high as 25% in pediatric studies.
Adverse skin reaction around the skin penetration site was the most common complication reported. Most of these conditions were successfully treated with antibiotics, and only 1% to 2% required surgical revision. Less than 1% required removal of the fixture.
Other complications included failure to osseointegrate and loss of fixture and/or abutment due to trauma or infection.
Effectiveness
Studies showed that BAHAs were implanted in people who have conduction or mixed hearing loss, congenital atresia or suppurative otitis media who were not candidates for surgical repair, and who cannot use conventional bone conduction hearing aids. The need for BAHA is not age- related. Objective audiometric measures and subjective patient satisfaction surveys showed that BAHA significantly improved the unaided and aided free field and sound field thresholds as well as speech discrimination in quiet and in noise for former users of conventional bone conduction hearing aids. The outcomes were ambiguous for former users of air conduction hearing aids.
BAHA has been shown to reduce the frequency of ear infection and reduce the discharge particularly among patients with suppurative otitis media.
Patients have reported that BAHA improved their quality of life. Reported benefits were improved speech intelligibility, better sound comfort, less pressure on the head, less skin irritation, greater cosmetic acceptance and increase in confidence. Main reported shortcomings were wind noise, feedback and difficulty in using the telephone.
Experts and the BAHA manufacturer recommended that recipients of a BAHA implant be at least 5 years old. Challenges associated with the implantation of BAHA in pediatric patients include thin bone, soft bone, higher rates of fixture loss due to trauma, psychological problems, and higher revision rates due to rapid bone growth. The overall outcomes are comparable to adult BAHA. The benefits of pediatric BAHA (e.g. on speech development) appear to outweigh the disadvantages.
Screening according to strict eligibility criteria, preoperative counselling, close monitoring by a physician with BAHA expertise and on-going follow-up were identified as critical factors for long-term implant survival. Examples of eligibility criteria were provided.
Cost-effectiveness
No literature on cost-effectiveness of BAHA was found.
PMCID: PMC3387772  PMID: 23074440
7.  Recognition and Localization of Speech by Adult Cochlear Implant Recipients Wearing a Digital Hearing Aid in the Nonimplanted Ear (Bimodal Hearing) 
Background
The use of bilateral amplification is now common clinical practice for hearing aid users but not for cochlear implant recipients. In the past, most cochlear implant recipients were implanted in one ear and wore only a monaural cochlear implant processor. There has been recent interest in benefits arising from bilateral stimulation that may be present for cochlear implant recipients. One option for bilateral stimulation is the use of a cochlear implant in one ear and a hearing aid in the opposite nonimplanted ear (bimodal hearing).
Purpose
This study evaluated the effect of wearing a cochlear implant in one ear and a digital hearing aid in the opposite ear on speech recognition and localization.
Research Design
A repeated-measures correlational study was completed.
Study Sample
Nineteen adult Cochlear Nucleus 24 implant recipients participated in the study.
Intervention
The participants were fit with a Widex Senso Vita 38 hearing aid to achieve maximum audibility and comfort within their dynamic range.
Data Collection and Analysis
Soundfield thresholds, loudness growth, speech recognition, localization, and subjective questionnaires were obtained six–eight weeks after the hearing aid fitting. Testing was completed in three conditions: hearing aid only, cochlear implant only, and cochlear implant and hearing aid (bimodal). All tests were repeated four weeks after the first test session. Repeated-measures analysis of variance was used to analyze the data. Significant effects were further examined using pairwise comparison of means or in the case of continuous moderators, regression analyses. The speech-recognition and localization tasks were unique, in that a speech stimulus presented from a variety of roaming azimuths (140 degree loudspeaker array) was used.
Results
Performance in the bimodal condition was significantly better for speech recognition and localization compared to the cochlear implant–only and hearing aid–only conditions. Performance was also different between these conditions when the location (i.e., side of the loudspeaker array that presented the word) was analyzed. In the bimodal condition, the speech-recognition and localization tasks were equal regardless of which side of the loudspeaker array presented the word, while performance was significantly poorer for the monaural conditions (hearing aid only and cochlear implant only) when the words were presented on the side with no stimulation. Binaural loudness summation of 1–3 dB was seen in soundfield thresholds and loudness growth in the bimodal condition. Measures of the audibility of sound with the hearing aid, including unaided thresholds, soundfield thresholds, and the Speech Intelligibility Index, were significant moderators of speech recognition and localization. Based on the questionnaire responses, participants showed a strong preference for bimodal stimulation.
Conclusions
These findings suggest that a well-fit digital hearing aid worn in conjunction with a cochlear implant is beneficial to speech recognition and localization. The dynamic test procedures used in this study illustrate the importance of bilateral hearing for locating, identifying, and switching attention between multiple speakers. It is recommended that unilateral cochlear implant recipients, with measurable unaided hearing thresholds, be fit with a hearing aid.
PMCID: PMC2876351  PMID: 19594084
Bimodal hearing; cochlear implant; hearing aid; localization; speech recognition
8.  Outcome of Vibrant Soundbridge Middle Ear Implant in Cantonese-Speaking Mixed Hearing Loss Adults 
Objectives
To investigate the aided benefits, speech recognition in quiet and in noise, change in hearing and subjective report of satisfaction on mixed hearing loss adults implanted with Vibrant Soundbridge (VSB) middle ear implant.
Methods
Eight Cantonese speaking adult patients with mixed hearing loss were enrolled in a single-subject, repeated measures prospective study design. Audiometric testing, including air and bone conduction and word recognition under sound-field were conducted before surgery. Device activation was arranged 8 weeks after operation. Audiometric testing was taken to evaluate the change in hearing. Patients were asked to wear the device and come back for fine tuning as needed. Outcome measurements were undertaken at 3 and 6 months after device activation. The outcome measures included sound-field thresholds, Cantonese Hearing in Noise Test (CHINT), Abbreviated Profile of Hearing Aid Benefit (APHAB) and International Outcome Inventory for Hearing Aids (IOI-HA).
Results
The application of the VSB improved the aided thresholds and improved speech intelligibility in quiet and noise without significant changes in hearing thresholds.
Conclusion
VSB is considered as a safe, effective and reliable auditory rehabilitation option for Cantonese speaking adults with mixed hearing loss.
doi:10.3342/ceo.2012.5.S1.S82
PMCID: PMC3369990  PMID: 22701155
Mixed hearing loss; Middle ear implant; Vibrant soundbridge
9.  New Criteria of Indication and Selection of Patients to Cochlear Implant 
Numerous changes continue to occur in cochlear implant candidacy. In general, these have been accompanied by concomitant and satisfactory changes in surgical techniques. Together, this has advanced the utility and safety of cochlear implantation. Most devices are now approved for use in patients with severe to profound unilateral hearing loss rather then the prior requirement of a bilateral profound loss. Furthermore, studies have begun utilizing short electrode arrays for shallow insertion in patients with considerable low-frequency residual hearing. This technique will allow the recipient to continue to use acoustically amplified hearing for the low frequencies simultaneously with a cochlear implant for the high frequencies. The advances in design of, and indications for, cochlear implants have been matched by improvements in surgical techniques and decrease in complications. The resulting improvements in safety and efficacy have further encouraged the use of these devices. This paper will review the new concepts in the candidacy of cochlear implant. Medline data base was used to search articles dealing with the following topics: cochlear implant in younger children, cochlear implant and hearing preservation, cochlear implant for unilateral deafness and tinnitus, genetic hearing loss and cochlear implant, bilateral cochlear implant, neuropathy and cochlear implant and neural plasticity, and the selection of patients for cochlear implant.
doi:10.1155/2011/573968
PMCID: PMC3195958  PMID: 22013448
10.  Cochlear Implantation in Non-Traditional Candidates: Preliminary Results in Adolescents with Asymmetric Hearing Loss 
Objective
Traditionally, children are cochlear implant (CI) candidates if bilateral severe to profound hearing loss is present and amplification benefit is limited. The current study investigated abilities of adolescents with asymmetric hearing loss (one ear with severe to profound hearing loss and better hearing contralaterally), where the poorer ear received a CI and the better ear maintained amplification.
Study Design
Within-subject case study
Setting
Pediatric hospital, outpatient clinic
Patients
Participants were five adolescents who had not met traditional CI candidacy due to one better hearing ear, but did have one ear that met criteria and was implanted. All maintained hearing aid (HA) use in the contralateral ear. In the poorer ear pre-implant, three participants had used amplification and the other two had no HA experience.
Main Outcome Measure
Participants were assessed in three listening conditions: HA alone, CI alone, and both devices together (bimodal) for speech recognition in quiet and noise, and sound localization.
Results
Three participants had CI open-set speech recognition and significant bimodal improvement for speech recognition and localization compared with the HA or CI alone. Two participants had no CI speech recognition and limited bimodal improvement.
Conclusions
Some adolescents with asymmetric hearing loss who are not typical CI candidates can benefit from a CI in the poorer ear, compared to a HA in the better ear alone. Additional study is needed to determine outcomes for this population, especially those who have early onset profound hearing loss in one ear and limited HA experience.
doi:10.1097/MAO.0b013e31827850b8
PMCID: PMC3600103  PMID: 23222962
11.  Younger- and older-age adults with unilateral and bilateral cochlear implants: Speech and spatial hearing self-ratings and performance 
Objective
Compare results of cochlear implantation in younger and older adults in the domains of disability and handicap, as well as in tests of word recognition and localization, across unilateral implant (CI), bilateral (CI+CI) and CI with an acoustic hearing aid in the non-implanted ear (CI+HA).
Design
Three parts: retrospective (post-implant only) analysis; prospective (pre-versus post-implant); correlation between age and benefit from CI versus CI+CI. Two age groups, above and below 60 years, for the first two analyses; age is a continuous variable for the third analysis.
Setting
Tertiary referral hospital clinic
Patients
Postlingually severely-to-profoundly hearing impaired adults: Totals of 68 CI, 36 CI+CI, and 38 CI+HA in the retrospective part of the study; totals of 30 CI, 18 CI+CI and 16 CI+HA in the prospective parts. Numbers vary from these totals on individual measures.
Interventions
Patients receive either one or two cochlear implants; some with one CI opt to retain a hearing aid in the non-implanted ear.
Outcome measures
Principal measures: Hearing Handicap Inventory for the Elderly, Hearing Handicap Questionnaire, Speech, Spatial and Qualities of Hearing scale, word recognition test, and soundfield localization test. The study is exploratory, but proceeding from a null hypothesis of no expected contrast as a function of patient age.
Results
All patient groups show significant benefit following implantation. No significant age-related differences are observed in patients with unilateral implant, nor in CI+HA group. In the CI+CI group, the younger cohort showed very substantial increases in both performance and self-rated abilities; the older cohort provides more mixed outcomes.
Conclusion
Results for the CI group confirm and extend earlier research. The result for the younger group of CI+CI patients demonstrates the consistent incremental benefit obtained from a bilateral procedure. The mixed outcome observed in the older CI+CI group might be due to individual differences in interaction between effects of aging and the ability to integrate binaural cues.
doi:10.1097/MAO.0b013e3181b76b3b
PMCID: PMC2828521  PMID: 19692936
12.  Leupeptin reduces impulse noise induced hearing loss 
Background
Exposure to continuous and impulse noise can induce a hearing loss. Leupeptin is an inhibitor of the calpains, a family of calcium-activated proteases which promote cell death. The objective of this study is to assess whether Leupeptin could reduce the hearing loss resulting from rifle impulse noise.
Methods
A polyethelene tube was implanted into middle ear cavities of eight fat sand rats (16 ears). Following determination of auditory nerve brainstem evoked response (ABR) threshold in each ear, the animals were exposed to the noise of 10 M16 rifle shots. Immediately after the exposure, saline was then applied to one (control) ear and non-toxic concentrations of leupeptin determined in the first phase of the study were applied to the other ear, for four consecutive days.
Results
Eight days after the exposure, the threshold shift (ABR) in the control ears was significantly greater (44 dB) than in the leupeptin ears (27 dB).
Conclusion
Leupeptin applied to the middle ear cavity can reduce the hearing loss resulting from exposure to impulse noise.
doi:10.1186/1745-6673-6-38
PMCID: PMC3286414  PMID: 22206578
protection; noise; apoptosis; threshold shift; calpains; rifle
13.  Studies on Bilateral Cochlear Implants at the University of Wisconsin’s Binaural Hearing and Speech Lab 
This report highlights research projects relevant to binaural and spatial hearing in adults and children. In the past decade we have made progress in understanding the impact of bilateral cochlear implants (BiCIs) on performance in adults and children. However, BiCI users typically do not perform as well as normal hearing (NH) listeners. In this paper we describe the benefits from BiCIs compared with a single CI, focusing on measures of spatial hearing and speech understanding in noise. We highlight the fact that in BiCI listening the devices in the two ears are not coordinated, thus binaural spatial cues that are available to NH listeners are not available to BiCI users. Through the use of research processors that carefully control the stimulus delivered to each electrode in each ear, we are able to preserve binaural cues and deliver them with fidelity to BiCI users. Results from those studies are discussed as well, with a focus on the effect of age at onset of deafness and plasticity of binaural sensitivity. Our work with children has expanded both in number of subjects tested and age range included. We have now tested dozens of children ranging in age from 2-14 years. Our findings suggest that spatial hearing abilities emerge with bilateral experience. While we originally focused on studying performance in free-field, where real world listening experiments are conducted, more recently we have begun to conduct studies under carefully controlled binaural stimulation conditions with children as well. We have also studied language acquisition and speech perception and production in young CI users. Finally, a running theme of this research program is the systematic investigation of the numerous factors that contribute to spatial and binaural hearing in BiCI users. By using CI simulations (with vocoders) and studying NH listeners under degraded listening conditions, we are able to tease apart limitations due to the hardware/software of the CI systems from limitations due to neural pathology.
doi:10.3766/jaaa.23.6.9
PMCID: PMC3517294  PMID: 22668767
14.  Passive and active middle ear implants 
Besides eradication of chronic middle ear disease, the reconstruction of the sound conduction apparatus is a major goal of modern ear microsurgery. The material of choice in cases of partial ossicular replacement prosthesis is the autogenous ossicle. In the event of more extensive destruction of the ossicular chain diverse alloplastic materials, e.g. metals, ceramics, plastics or composits are used for total reconstruction. Their specialised role in conducting sound energy within a half-open implant bed sets high demands on the biocompatibility as well as the acoustic-mechanic properties of the prosthesis. Recently, sophisticated titanium middle ear implants allowing individual adaptation to anatomical variations are widely used for this procedure. However, despite modern developments, hearing restoration with passive implants often faces its limitations due to tubal-middle-ear dysfunction. Here, implantable hearing aids, successfully used in cases of sensorineural hearing loss, offer a promising alternative. This article reviews the actual state of affairs of passive and active middle ear implants.
doi:10.3205/cto000061
PMCID: PMC3199819  PMID: 22073102
middle ear; implantable hearing aids; tympanoplasty; titanium; middle ear implants
15.  The multiple-channel cochlear implant: the interface between sound and the central nervous system for hearing, speech, and language in deaf people—a personal perspective 
The multiple-channel cochlear implant is the first sensori-neural prosthesis to effectively and safely bring electronic technology into a direct physiological relation with the central nervous system and human consciousness, and to give speech perception to severely-profoundly deaf people and spoken language to children.
Research showed that the place and temporal coding of sound frequencies could be partly replicated by multiple-channel stimulation of the auditory nerve. This required safety studies on how to prevent the effects to the cochlea of trauma, electrical stimuli, biomaterials and middle ear infection. The mechanical properties of an array and mode of stimulation for the place coding of speech frequencies were determined.
A fully implantable receiver–stimulator was developed, as well as the procedures for the clinical assessment of deaf people, and the surgical placement of the device. The perception of electrically coded sounds was determined, and a speech processing strategy discovered that enabled late-deafened adults to comprehend running speech. The brain processing systems for patterns of electrical stimuli reproducing speech were elucidated. The research was developed industrially, and improvements in speech processing made through presenting additional speech frequencies by place coding. Finally, the importance of the multiple-channel cochlear implant for early deafened children was established.
doi:10.1098/rstb.2005.1782
PMCID: PMC1609401  PMID: 16627295
multiple-channel cochlear implant; electrical stimulation of the auditory nerve; management of severe-profound hearing loss
16.  Effects of Semicircular Canal Electrode Implantation on Hearing in Chinchillas 
Acta oto-laryngologica  2009;129(5):481-486.
Conclusion
Implantation of vestibular prosthesis electrodes in chinchilla semicircular canal ampullae can be accomplished without significant loss of cochlear function; however, the risk of hearing loss with the current surgical technique is high.
Objectives
To determine if it is possible to implant vestibular prosthesis electrodes into the labyrinth without damaging hearing, and to quantify the extent of hearing loss due to implantation.
Method
The left semicircular canals of 6 chinchillas were implanted with 3 bipolar pairs of electrodes using a transmastoid approach. Right ears, which served as controls, were subjected to the same mastoid approach without fenestration and implantation. Auditory brainstem response hearing thresholds to free field clicks and tone pips at 2, 4, 6, and 8 kHz were measured bilaterally 3–9 weeks after implantation. Hearing thresholds were compared between sides and against data from 6 normal chinchillas.
Results
4 implanted ears suffered severe hearing loss, with thresholds ranging from 5 to 11 SD above the mean threshold of sham surgery control ears across all tested stimuli. 2 implanted ears had preserved hearing, with thresholds remaining within 1 SD of the mean threshold of sham surgery control ears across nearly all stimulus frequencies.
doi:10.1080/00016480802252243
PMCID: PMC2767272  PMID: 18615331
Vestibular prosthesis; labyrinth; sensorineural hearing loss; auditory brainstem response; chinchilla; cochlea; implant
17.  Unilateral hearing during development: hemispheric specificity in plastic reorganizations 
The present study investigates the hemispheric contributions of neuronal reorganization following early single-sided hearing (unilateral deafness). The experiments were performed on ten cats from our colony of deaf white cats. Two were identified in early hearing screening as unilaterally congenitally deaf. The remaining eight were bilaterally congenitally deaf, unilaterally implanted at different ages with a cochlear implant. Implanted animals were chronically stimulated using a single-channel portable signal processor for two to five months. Microelectrode recordings were performed at the primary auditory cortex under stimulation at the hearing and deaf ear with bilateral cochlear implants. Local field potentials (LFPs) were compared at the cortex ipsilateral and contralateral to the hearing ear. The focus of the study was on the morphology and the onset latency of the LFPs. With respect to morphology of LFPs, pronounced hemisphere-specific effects were observed. Morphology of amplitude-normalized LFPs for stimulation of the deaf and the hearing ear was similar for responses recorded at the same hemisphere. However, when comparisons were performed between the hemispheres, the morphology was more dissimilar even though the same ear was stimulated. This demonstrates hemispheric specificity of some cortical adaptations irrespective of the ear stimulated. The results suggest a specific adaptation process at the hemisphere ipsilateral to the hearing ear, involving specific (down-regulated inhibitory) mechanisms not found in the contralateral hemisphere. Finally, onset latencies revealed that the sensitive period for the cortex ipsilateral to the hearing ear is shorter than that for the contralateral cortex. Unilateral hearing experience leads to a functionally-asymmetric brain with different neuronal reorganizations and different sensitive periods involved.
doi:10.3389/fnsys.2013.00093
PMCID: PMC3841817  PMID: 24348345
cochlear implant; plasticity; single-sided deafness; critical periods; development
18.  Combined Acoustic and Electric Hearing: Preserving Residual Acoustic Hearing 
Hearing research  2007;242(1-2):164-171.
The topic of this review is the strategy of preserving residual acoustic hearing in the implanted ear to provide combined electrical stimulation and acoustic hearing as a rehabilitative strategy for sensorineural hearing loss. This chapter will concentrate on research done with the Iowa/Nucleus 10mm Hybrid device, but we will also attempt to summarize strategies and results from other groups around the world who use slightly different approaches. A number of studies have shown that preserving residual acoustic hearing in the implanted ear is a realistic goal for many patients with severe high-frequency hearing loss. The addition of the electric stimulation to their existing acoustic hearing can provide increased speech recognition for these patients. In addition, the preserved acoustic hearing can offer considerable advantages, as compared to a traditional cochlear implant, for tasks such as speech recognition in backgrounds or appreciation of music and other situations where the poor frequency resolution of electric stimulation has been a disadvantage.
doi:10.1016/j.heares.2007.11.008
PMCID: PMC2593157  PMID: 18164883
Acoustic Plus Electric (A+E); Cochlear Implant; Sensorineural Hearing Loss
19.  Preliminary speech recognition results after cochlear implantation in patients with unilateral hearing loss: a case series 
Introduction
Cochlear implants known to provide support in individuals with bilateral hearing loss may also be of great benefit for individuals with unilateral hearing loss. This case report demonstrates the positive effects of cochlear implantation on speech understanding in noise conditions in patients with unilateral hearing loss and normal hearing on the contralateral side. To the best of our knowledge, the data presented here are from the first few cases to receive a cochlear implant for unilateral hearing loss.
Case presentation
Four Caucasian German men, two aged 48 and the others aged 51 and 57 years old, with post-lingual unilateral hearing loss and normal hearing on the contralateral side were implanted with a cochlear implant. All our patients were members of the German army. Before and after implantation, they were given a battery of speech tests in different hearing conditions to assess the effect of unilateral cochlear implantation on speech understanding in noise conditions. Test results showed that all patients benefited from unilateral cochlear implantation, particularly in terms of speech understanding in noise conditions.
Conclusions
Unilateral cochlear implantation might be a successful treatment method for patients with unilateral hearing loss not benefiting from alternative treatment options. The results of this case report open up the field of cochlear implantation for expanded criteria and new areas of research.
doi:10.1186/1752-1947-5-343
PMCID: PMC3169493  PMID: 21810235
20.  Reconstructive methods in hearing disorders - surgical methods 
Restoration of hearing is associated in many cases with resocialisation of those affected and therefore occupies an important place in a society where communication is becoming ever faster. Not all problems can be solved surgically. Even 50 years after the introduction of tympanoplasty, the hearing results are unsatisfactory and often do not reach the threshold for social hearing. The cause of this can in most cases be regarded as incomplete restoration of the mucosal function of the middle ear and tube, which leads to ventilation disorders of the ear and does not allow real vibration of the reconstructed middle ear. However, a few are also caused by the biomechanics of the reconstructed ossicular chain. There has been progress in reconstructive middle ear surgery, which applies particularly to the development of implants. Implants made of titanium, which are distinguished by outstanding biocompatibility, delicate design and by biomechanical possibilities in the reconstruction of chain function, can be regarded as a new generation. Metal implants for the first time allow a controlled close fit with the remainder of the chain and integration of micromechanical functions in the implant. Moreover, there has also been progress in microsurgery itself. This applies particularly to the operative procedures for auditory canal atresia, the restoration of the tympanic membrane and the coupling of implants. This paper gives a summary of the current state of reconstructive microsurgery paying attention to the acousto-mechanical rules.
PMCID: PMC3201000  PMID: 22073050
middle ear surgery; middle ear reconstruction; tympanoplasty; stapessurgery; auditory canal reconstruction; middle ear implant; auditory canal atresia
21.  Cochlear implantation in branchio-oto-renal syndrome — A surgical challenge 
Branchio-oto-renal syndrome (Melnick-Fraser Syndrome) is a rare Autosomal Dominant disorder characterized by the syndromic association of branchial cysts or fistulae along with external, middle & inner malformations and renal anomalies. Incomplete penetrance and variable expressivity are common with the phenotypic variation ranging from mild to severe forms & consisting of various eye, ear, oral and craniofacial abnormalities. Mutations in the EYA1 gene on chromosomal site 8q13.3 are identified as the primary cause of BOR syndrome. We present a 3year old child with BOR syndrome, who came to us with bilateral low set, malformed ears & profound cochlear hearing loss along with bilateral branchial fistulae & unilateral renal agenesis. This child underwent successful cochlear implantation recently. The clinical presentation, pre-operative investigations, intra-operative findings & post-op habilitation status are presented with special highlights on the unique facial nerve course along with middle and inner ear anomalies which posed a surgical challenge during cochlear implantation.
doi:10.1007/s12070-007-0081-7
PMCID: PMC3452117  PMID: 23120453
Branchio-oto-renal syndrome; Renal EYA1 gene; facial nerve anomaly
22.  Bilateral Cochlear Implants in Children: Localization Acuity Measured with Minimum Audible Angle 
Ear and hearing  2006;27(1):43-59.
Objective
To evaluate sound localization acuity in a group of children who received bilateral (BI) cochlear implants in sequential procedures and to determine the extent to which BI auditory experience affects sound localization acuity. In addition, to investigate the extent to which a hearing aid in the nonimplanted ear can also provide benefits on this task.
Design
Two groups of children participated, 13 with BI cochlear implants (cochlear implant + cochlear implant), ranging in age from 3 to 16 yrs, and six with a hearing aid in the nonimplanted ear (cochlear implant + hearing aid), ages 4 to 14 yrs. Testing was conducted in large sound-treated booths with loudspeakers positioned on a horizontal arc with a radius of 1.5 m. Stimuli were spondaic words recorded with a male voice. Stimulus levels typically averaged 60 dB SPL and were randomly roved between 56 and 64 dB SPL (±4 dB rove); in a few instances, levels were held fixed (60 dB SPL). Testing was conducted by using a “listening game” platform via computerized interactive software, and the ability of each child to discriminate sounds presented to the right or left was measured for loudspeakers subtending various angular separations. Minimum audible angle thresholds were measured in the BI (cochlear implant + cochlear implant or cochlear implant + hearing aid) listening mode and under monaural conditions.
Results
Approximately 70% (9/13) of children in the cochlear implant + cochlear implant group discriminated left/right for source separations of ≤20° and, of those, 77% (7/9) performed better when listening bilaterally than with either cochlear implant alone. Several children were also able to perform the task when using a single cochlear implant, under some conditions. Minimum audible angle thresholds were better in the first cochlear implant than the second cochlear implant listening mode for nearly all (8/9) subjects. Repeated testing of a few individual subjects over a 2-yr period suggests that robust improvements in performance occurred with increased auditory experience. Children who wore hearing aids in the nonimplanted ear were at times also able to perform the task. Average group performance was worse than that of the children with BI cochlear implants when both ears were activated (cochlear implant + hearing aid versus cochlear implant + cochlear implant) but not significantly different when listening with a single cochlear implant.
Conclusions
Children with sequential BI cochlear implants represent a unique population of individuals who have undergone variable amounts of auditory deprivation in each ear. Our findings suggest that many but not all of these children perform better on measures of localization acuity with two cochlear implants compared with one and are better at the task than children using the cochlear implant + hearing aid. These results must be interpreted with caution, because benefits on other tasks as well as the long-term benefits of BI cochlear implants are yet to be fully understood. The factors that might contribute to such benefits must be carefully evaluated in large populations of children using a variety of measures.
doi:10.1097/01.aud.0000194515.28023.4b
PMCID: PMC2651156  PMID: 16446564
23.  Comparison of bimodal and bilateral cochlear implant users on speech recognition with competing talker, music perception, affective prosody discrimination and talker identification 
Ear and hearing  2011;32(1):16-30.
Objectives
Despite excellent performance in speech recognition in quiet, most cochlear implant users have great difficulty with speech recognition in noise, music perception, identifying tone of voice, and discriminating different talkers. This may be partly due to the pitch coding in cochlear implant speech processing. Most current speech processing strategies use only the envelope information; the temporal fine structure is discarded. One way to improve electric pitch perception is to utilize residual acoustic hearing via a hearing aid on the non-implanted ear (bimodal hearing). This study aimed to test the hypothesis that bimodal users would perform better than bilateral cochlear implant users on tasks requiring good pitch perception.
Design
Four pitch-related tasks were used:
Hearing in Noise Test (HINT) sentences spoken by a male talker with a competing female, male, or child talker.
Montreal Battery of Evaluation of Amusia. This is a music test with six subtests examining pitch, rhythm and timing perception, and musical memory.
Aprosodia Battery. This has five subtests evaluating aspects of affective prosody and recognition of sarcasm.
Talker identification using vowels spoken by ten different talkers (three male, three female, two boys, and two girls).
Bilateral cochlear implant users were chosen as the comparison group. Thirteen bimodal and thirteen bilateral adult cochlear implant users were recruited; all had good speech perception in quiet.
Results
There were no significant differences between the mean scores of the bimodal and bilateral groups on any of the tests, although the bimodal group did perform better than the bilateral group on almost all tests. Performance on the different pitch-related tasks was not correlated, meaning that if a subject performed one task well they would not necessarily perform well on another. The correlation between the bimodal users' hearing threshold levels in the aided ear and their performance on these tasks was weak.
Conclusions
Although the bimodal cochlear implant group performed better than the bilateral group on most parts of the four pitch-related tests, the differences were not statistically significant. The lack of correlation between test results shows that the tasks used are not simply providing a measure of pitch ability. Even if the bimodal users have better pitch perception, the real-world tasks used are reflecting more diverse skills than pitch. This research adds to the existing speech perception, language, and localization studies that show no significant difference between bimodal and bilateral cochlear implant users.
doi:10.1097/AUD.0b013e3181edfbd2
PMCID: PMC3059251  PMID: 21178567
cochlear implants; bimodal; bilateral
24.  Changes in auditory perceptions and cortex resulting from hearing recovery after extended congenital unilateral hearing loss 
Monaural hearing induces auditory system reorganization. Imbalanced input also degrades time-intensity cues for sound localization and signal segregation for listening in noise. While there have been studies of bilateral auditory deprivation and later hearing restoration (e.g., cochlear implants), less is known about unilateral auditory deprivation and subsequent hearing improvement. We investigated effects of long-term congenital unilateral hearing loss on localization, speech understanding, and cortical organization following hearing recovery. Hearing in the congenitally affected ear of a 41 year old female improved significantly after stapedotomy and reconstruction. Pre-operative hearing threshold levels showed unilateral, mixed, moderately-severe to profound hearing loss. The contralateral ear had hearing threshold levels within normal limits. Testing was completed prior to, and 3 and 9 months after surgery. Measurements were of sound localization with intensity-roved stimuli and speech recognition in various noise conditions. We also evoked magnetic resonance signals with monaural stimulation to the unaffected ear. Activation magnitudes were determined in core, belt, and parabelt auditory cortex regions via an interrupted single event design. Hearing improvement following 40 years of congenital unilateral hearing loss resulted in substantially improved sound localization and speech recognition in noise. Auditory cortex also reorganized. Contralateral auditory cortex responses were increased after hearing recovery and the extent of activated cortex was bilateral, including a greater portion of the posterior superior temporal plane. Thus, prolonged predominant monaural stimulation did not prevent auditory system changes consequent to restored binaural hearing. Results support future research of unilateral auditory deprivation effects and plasticity, with consideration for length of deprivation, age at hearing correction and degree and type of hearing loss.
doi:10.3389/fnsys.2013.00108
PMCID: PMC3861790  PMID: 24379761
unilateral hearing loss; congenital; conductive; stapedotomy; brain imaging; sound localization; speech recognition
25.  Acoustic Analysis of Speech of Cochlear Implantees and Its Implications 
Objectives
Cochlear implantees have improved speech production skills compared with those using hearing aids, as reflected in their acoustic measures. When compared to normal hearing controls, implanted children had fronted vowel space and their /s/ and /∫/ noise frequencies overlapped. Acoustic analysis of speech provides an objective index of perceived differences in speech production which can be precursory in planning therapy. The objective of this study was to compare acoustic characteristics of speech in cochlear implantees with those of normal hearing age matched peers to understand implications.
Methods
Group 1 consisted of 15 children with prelingual bilateral severe-profound hearing loss (age, 5-11 years; implanted between 4-10 years). Prior to an implant behind the ear, hearing aids were used; prior & post implantation subjects received at least 1 year of aural intervention. Group 2 consisted of 15 normal hearing age matched peers. Sustained productions of vowels and words with selected consonants were recorded. Using Praat software for acoustic analysis, digitized speech tokens were measured for F1, F2, and F3 of vowels; centre frequency (Hz) and energy concentration (dB) in burst; voice onset time (VOT in ms) for stops; centre frequency (Hz) of noise in /s/; rise time (ms) for affricates. A t-test was used to find significant differences between groups.
Results
Significant differences were found in VOT for /b/, F1 and F2 of /e/, and F3 of /u/. No significant differences were found for centre frequency of burst, energy concentration for stops, centre frequency of noise in /s/, or rise time for affricates. These findings suggest that auditory feedback provided by cochlear implants enable subjects to monitor production of speech sounds.
Conclusion
Acoustic analysis of speech is an essential method for discerning characteristics which have or have not been improved by cochlear implantation and thus for planning intervention.
doi:10.3342/ceo.2012.5.S1.S14
PMCID: PMC3369976  PMID: 22701768
Acoustic analysis; Speech production; Cochlear implantees

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