Cochlear implantation in common forms of genetic deafness

Engineering of the AAV-Compatible Hair Cell-Specific Small-Size Myo15 Promoter for Gene Therapy in the Inner Ear

Adeno-associated virus (AAV)-mediated gene therapy is widely applied to treat numerous hereditary diseases in animal models and humans. The specific expression of AAV-delivered transgenes driven by cell type-specific promoters should further increase the safety of gene therapy. However, current methods for screening cell type-specific promoters are labor-intensive and time-consuming. Herein, we designed a "multiple vectors in one AAV" strategy for promoter construction in vivo. Through this strategy, we truncated a native promoter for Myo15 expression in hair cells (HCs) in the inner ear, from 1,611 bp down to 1,157 bp, and further down to 956 bp. Under the control of these 2 promoters, green fluorescent protein packaged in AAV-PHP.eB was exclusively expressed in the HCs. The transcription initiation ability of the 2 promoters was further verified by intein-mediated otoferlin recombination in a dual-AAV therapeutic system. Driven by these 2 promoters, human otoferlin was selectively expressed in HCs, resulting in the restoration of hearing in treated Otof -/- mice for at least 52 weeks. In summary, we developed an efficient screening strategy for cell type-specific promoter engineering and created 2 truncated Myo15 promoters that not only restored hereditary deafness in animal models but also show great potential for treating human patients in future.

Usher Syndrome in the Inner Ear: Etiologies and Advances in Gene Therapy

Hearing loss is the most common sensory disorder with ~466 million people worldwide affected, representing about 5% of the population. A substantial portion of hearing loss is genetic. Hearing loss can either be non-syndromic, if hearing loss is the only clinical manifestation, or syndromic, if the hearing loss is accompanied by a collage of other clinical manifestations. Usher syndrome is a syndromic form of genetic hearing loss that is accompanied by impaired vision associated with retinitis pigmentosa and, in many cases, vestibular dysfunction. It is the most common cause of deaf-blindness. Currently cochlear implantation or hearing aids are the only treatments for Usher-related hearing loss. However, gene therapy has shown promise in treating Usher-related retinitis pigmentosa. Here we review how the etiologies of Usher-related hearing loss make it a good candidate for gene therapy and discuss how various forms of gene therapy could be applied to Usher-related hearing loss.

Cochlear Implantation Outcomes in Patients with Mitochondrial Hearing Loss: A Systematic Review and Narrative Synthesis

This study's aim was to establish outcomes following cochlear implantation (CI) in patients with mitochondrial disorders associated with deafness. Systematic review and narrative synthesis. Databases searched: Medline, EMBASE, Web of Science, COCHRANE, and ClinicalTrials.gov. No limits on language or year of publication. Review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Searches identified 437 abstracts and 37 full text articles, of which 11 studies met the inclusion criteria reporting outcomes in a total of 17 patients. All implants achieved good hearing outcomes, and follow-up ranged between 1 week and 12 months. The methodological quality of the included studies was sufficient, scoring grades 3 to 4 using the Oxford Centre for Evidence Based Medicine grading system. All studies were retrospective and consisted of case reviews and case reports. All cases of CI showed positive outcomes in speech perception and detection. There is some qualitative evidence to suggest improvement in quality of life and satisfaction postoperatively. There was very limited information available on secondary outcomes such as surgical complications, quality of life, and method of cochlear implant insertion. The small sample size of our patient cohort and quality of studies suggests a need for large-scale studies with more robust methodology to assess the effectiveness of CI. There is a need for studies that assess other factors to be considered when counseling patients about cochlear implants, such as adverse events, surgical complications, and long-term benefits.

Screening Strategies for Deafness Genes and Functional Outcomes in Cochlear Implant Patients

OBJECTIVES

To review the current state of knowledge about the influence of specific genetic mutations that cause sensorineural hearing loss (SNHL) on cochlear implant (CI) functional outcomes, and how this knowledge may be integrated into clinical practice. A multistep and sequential population-based genetic algorithm suitable for the identification of congenital SNHL mutations before CI placement is also examined.

DATA SOURCES, STUDY SELECTION

A review was performed of the English literature from 2000 to 2019 using PubMed regarding the influence of specific mutations on CI outcomes and the use of next-generation sequencing for genetic screening of CI patients.

CONCLUSION

CI is an effective habilitation option for patients with severe-profound congenital SNHL. However, it is well known that CI outcomes show substantial inter-patient variation. Recent advances in genetic studies have improved our understanding of genotype-phenotype relationships for many of the mutations underlying congenital SNHL, and have explored how these relationships may account for some of the variance seen in CI performance outcomes. A sequential genetic screening strategy utilizing next-generation sequencing-based population-specific gene panels may allow for more efficient mutation identification before CI placement. Understanding the relationships between specific mutations and CI outcomes along with integrating routine comprehensive genetic testing into pre-CI evaluations will allow for more effective patient counseling and open the door for the development of mutation-specific treatment strategies.

Diagnostic and therapeutic applications of genomic medicine in progressive, late-onset, nonsyndromic sensorineural hearing loss

The progressive, late-onset, nonsyndromic, sensorineural hearing loss (PNSHL) is the most common cause of sensory impairment globally, with presbycusis affecting greater than a third of individuals over the age of 65. The etiology underlying PNSHL include presbycusis, noise-induced hearing loss, drug ototoxicity, and delayed-onset autosomal dominant hearing loss (AD PNSHL). The objective of this article is to discuss the potential diagnostic and therapeutic applications of genomic medicine in PNSHL. Genomic factors contribute greatly to PNSHL. The heritability of presbycusis ranges from 25 to 75%. Current therapies for PNSHL range from sound amplification to cochlear implantation (CI). PNSHL is an excellent candidate for genomic medicine approaches as it is common, has well-described pathophysiology, has a wide time window for treatment, and is amenable to local gene therapy by currently utilized procedural approaches. AD PNSHL is especially suited to genomic medicine approaches that can disrupt the expression of an aberrant protein product. Gene therapy is emerging as a potential therapeutic strategy for the treatment of PNSHL. Viral gene delivery approaches have demonstrated promising results in human clinical trials for two inherited causes of blindness and are being used for PNSHL in animal models and a human trial. Non-viral gene therapy approaches are useful in situations where a transient biologic effect is needed or for delivery of genome editing reagents (such as CRISPR/Cas9) into the inner ear. Many gene therapy modalities that have proven efficacious in animal trials have potential to delay or prevent PNSHL in humans. The development of new treatment modalities for PNSHL will lead to improved quality of life of many affected individuals and their families.

Genotype-Phenotype Correlation for Predicting Cochlear Implant Outcome: Current Challenges and Opportunities

The use and utility of cochlear implantation has rapidly increased in recent years as technological advances in the field have expanded both the efficacy and eligible patient population for implantation. This review aims to serve as a general overview of the most common hearing disorders that have favorable auditory outcomes with cochlear implants (CI). Hearing loss in children caused by congenital cytomegalovirus infection, syndromic conditions including Pendred Syndrome, and non-syndromic genetic conditions such as hearing impairment associated with GJB2 mutations have shown to be successfully managed by CI. Furthermore, cochlear implantation provides the auditory rehabilitation for the most common etiology of hearing loss in adults and age-related hearing loss (ARHL) or presbycusis. However, in some cases, cochlear implantation have been associated with some challenges. Regarding implantation in children, studies have shown that sometimes parents seem to have unrealistic expectations regarding the ability of CI to provide auditory rehabilitation and speech improvement. Given the evidence revealing the beneficial effects of early intervention via CI in individuals with hearing disorders especially hearing loss due to genetic etiology, early auditory and genetic screening efforts may yield better clinical outcomes. There is a need to better understand genotype-phenotype correlations and CI outcome, so that effective genetic counseling and successful treatment strategies can be developed at the appropriate time for hearing impaired individuals.

Application of auditory cortical evoked potentials for auditory assessment in people using auditory prosthesis

The present study explored the application of auditory cortical evoked potentials (ACEP) in the auditory assessment of people using an auditory prosthesis. There were 126 patients with prelingual deafness who were selected from January 2012-June 2017 from the First People's Hospital of Kunshan (Kunshan, China). HEARLab™ system was used to induce a P1-N1-P2 waveform under the condition of 60 dB sound pressure level at /m/, /g/ and /t/ acoustic stimulations. Speech production ability and auditory perception ability of patients were evaluated by speech intelligibility rating (SIR) and categories of auditory performance (CAP). Extraction rate of P1 waves of patients with auditory prosthesis was higher than that of N1 and P2 waves under different acoustic stimulations. A younger initial age and shorter deafness duration before patients used an auditory prosthesis led to more marked P1-N1-P2 waveforms and longer P1 latencies. At /m/ acoustic stimulation, P1 latency and amplitude were negatively associated with the usage time of auditory prosthesis. There were significant differences in the results of SIR and CAP and the initial age of use of auditory prosthesis and deafness duration before patients used the auditory prosthesis. These findings suggest that ACEP can be used to evaluate the auditory assessment of people using an auditory prosthesis. The initial age of use of an auditory prosthesis and deafness duration can affect the P1-N1-P2 waveform and P1 latency of prelingual deafness.

Dual AAV-mediated gene therapy restores hearing in a DFNB9 mouse model

Autosomal recessive genetic forms (DFNB) account for most cases of profound congenital deafness. Adeno-associated virus (AAV)-based gene therapy is a promising therapeutic option, but is limited by a potentially short therapeutic window and the constrained packaging capacity of the vector. We focus here on the otoferlin gene underlying DFNB9, one of the most frequent genetic forms of congenital deafness. We adopted a dual AAV approach using two different recombinant vectors, one containing the 5' and the other the 3' portions of otoferlin cDNA, which exceed the packaging capacity of the AAV when combined. A single delivery of the vector pair into the mature cochlea of Otof ^-/- mutant mice reconstituted the otoferlin cDNA coding sequence through recombination of the 5' and 3' cDNAs, leading to the durable restoration of otoferlin expression in transduced cells and a reversal of the deafness phenotype, raising hopes for future gene therapy trials in DFNB9 patients.

Genetic Testing of Non-familial Deaf Patients for CIB2 and GJB2 Mutations: Phenotype and Genetic Counselling

CIB2 and GJB2 genes variants contribute significantly in familial cases of prelingual recessive hearing loss (HL). This study was aimed to determine the CIB2 and GJB2 variants and associated phenotype in 150 non-familial individuals with HL. After getting informed consent, 150 non-familial deaf patients were enrolled and blood samples were obtained for DNA extraction. Pure tone air conduction audiometry was performed. Coding exons of CIB2 and GJB2 genes were Sanger sequenced. A tetra primer ARMS assay was developed for recurrent CIB2 variant. Four bi-allelic GJB2 variants, c.71G>A p.(Trp24*), c.231G>A p.(Trp77*), c.235delC p.(Leu79Cysfs3*) and c.35delG p.(Gly11Leufs24*), were found in nine hearing impaired individuals. We also found four homozygotes and five carriers of c.380G>A p. (Arg127His) variant of controversial clinical significance. CIB2 sequencing revealed single recurrent variant c.272T>C p. (Phe91Ser) segregating with HL in ten individuals. Among our patients, c.71G>A (p.Trp24*) was the most common variant, accounted for 45% of GJB2 variants. Two known GJB2 variants, c.235delC p. (Leu79Cysfs3*) and c.310del14 p. (Lys105Argfs2*), are reported here for the first time in Pakistani population. Our data further support the benign nature of c.380G>A p. (Arg127His) variant. For CIB2, c.272T>C p. (Phe91Ser) is the second common cause of HL among our sporadic cases. Phenotypically, in our patients, individuals homozygous for GJB2 variants had profound HL, whereas CIB2 homozygotes had severe to profound prelingual HL. Our results suggest that GJB2 and CIB2 are common cause of HL in different Pakistani ethnicities.

Local gene therapy durably restores vestibular function in a mouse model of Usher syndrome type 1G

Our understanding of the mechanisms underlying inherited forms of inner ear deficits has considerably improved during the past 20 y, but we are still far from curative treatments. We investigated gene replacement as a strategy for restoring inner ear functions in a mouse model of Usher syndrome type 1G, characterized by congenital profound deafness and balance disorders. These mice lack the scaffold protein sans, which is involved both in the morphogenesis of the stereociliary bundle, the sensory antenna of inner ear hair cells, and in the mechanoelectrical transduction process. We show that a single delivery of the sans cDNA by the adenoassociated virus 8 to the inner ear of newborn mutant mice reestablishes the expression and targeting of the protein to the tips of stereocilia. The therapeutic gene restores the architecture and mechanosensitivity of stereociliary bundles, improves hearing thresholds, and durably rescues these mice from the balance defects. Our results open up new perspectives for efficient gene therapy of cochlear and vestibular disorders by showing that even severe dysmorphogenesis of stereociliary bundles can be corrected.

[The results of cochlear implantation in the patient with hereditary and non-hereditary hearing loss]

The objective of the present study was to evaluate the effectiveness of rehabilitation of the patients after cochlear implantation in the early and late periods after operation taking into consideration the etiology of congenital deafness. The comprehensive clinico-audiological examination performed during the period from 2010 to 2015 involved 246 children who had undergone cochlear implantation (CI). All children were operated at the National Research Center for Audiology and Hearing Rehabilitation in the period from 2003 to 2013. 83 (56%) patients were aged 1 to 3 years at the time of surgery. Their age varied from 3 to 18 years when they underwent the clinico-audiological examination. Thus, the study is based on the experience with cochlear implantation varying from 3 to 12 years. The genetic analysis revealed mutations in the GJB2 gene in 49% of the children, in agreement with the data of earlier studies. 85% of all the children with GJB2 deafness surgically treated at the age under 4 years attend ordinary institutions of learning. Within 24 months after the onset of the observations the majority of the children with hereditary deafness (63%) were referred to the groups with good and excellent results of the rehabilitation and only 6 (12%) patients presented with unsatisfactory results. It was shown that the acquired causes of the loss of hearing including severe prenatal pathology have a negative influence on the long-term outcomes of rehabilitation. The results of the genetic analysis for the elucidation of the cause of impaired hearing can be employed as a prognostic criteria not only for the prediction but also for the guarantee of the success of cochlear implantation provided the rehabilitative process was initiated in a proper time.

Evaluation of cochlear nerve diameter and cross-sectional area in ANSD patients by 3.0-Tesla MRI

CONCLUSIONS

The size of cochlear nerve (CN) is atrophic in adult auditory neuropathy spectrum disorder (ANSD) patients compared with non-ANSD sensorineural hearing loss (SNHL) patients and normal hearing subjects, and CN deficiency is one of the lesions for ANSD patients.

OBJECTIVES

To evaluate the dimensions of CN in adult ANSD patients on magnetic resonance imaging (MRI) and confirm the hypothesis that CN deficiency is one of the lesions for ANSD patients.

METHODS

Medical records and MRI of 24 adult ANSD patients reviewed retrospectively and 20 non-ANSD SNHL and 24 volunteers with normal hearing were recruited as control groups. The long diameter (LD), short diameter (SD), and cross-sectional area (CSA) of CN and facial nerve (FN) were measured.

RESULTS

Among the 24 ANSD patients, this study was able to reconstruct and measure the CN of 91.7% (22/24, total 43 ears) of patients and FN of 83.3% (20/24, total 38 ears) of patients. The mean values and standard deviations of LD, SD, and CSA of CN in ANSD patients were 0.65 ± 0.20 mm, 0.44 ± 0.15 mm, and 0.30 ± 0.19 mm(2), respectively. They were significantly smaller in ANSD patients than in control groups (p < 0.001).

Guidelines for Audiologists on the Benefits and Limitations of Genetic Testing

PURPOSE

This tutorial provides information to aid audiologists in determining when a referral for a genetics evaluation is appropriate for a patient with hearing loss. Direction is given on discussing the benefits and limitations of genetic testing with parents of children with hearing loss.

METHOD

Genetic patterns of inheritance are reviewed, particularly in reference to syndromic and nonsyndromic forms of hearing loss. A review of pertinent literature was performed.

CONCLUSION

Audiologists are in a unique position to facilitate investigation into the etiology of a patient's hearing loss. This is of high importance in genetic etiologies because the diagnosis can provide information on recurrence risks and other potential health implications. Suggestions are made to help audiologists recognize when a genetics referral is warranted, counsel patients and their parents about the benefits and limitations of genetic testing, and interpret genetic test results.

Genetics of non syndromic hearing loss

Non Syndromic Hearing Loss is an important cause for hearing loss. One in 1000 newborns have some hearing impairment. Over 400 genetic syndromes have been described. Non Syndromic Hearing Loss (NSHL) can be inherited in an Autosomal Dominant, Autosomal Recessive or a Sex Linked fashion. There are several reasons why genetic testing should be done in cases of NSHL, the main reasons being for genetic screening and for planning treatment. This review describes the genes involved in NSHL and the genetic mechanisms involved in the pathogenesis of the disease.

Superior temporal resolution of Chronos versus channelrhodopsin-2 in an optogenetic model of the auditory brainstem implant

Contemporary auditory brainstem implant (ABI) performance is limited by reliance on electrical neurostimulation with its accompanying channel cross talk and current spread to non-auditory neurons. A new generation ABI based on optogenetic technology may ameliorate limitations fundamental to electrical stimulation. The most widely studied opsin is channelrhodopsin-2 (ChR2); however, its relatively slow kinetic properties may prevent the encoding of auditory information at high stimulation rates. In the present study, we compare the temporal resolution of light-evoked responses of ChR2 to a recently developed fast opsin, Chronos, to ChR2 in a murine ABI model. Viral mediated gene transfer via a posterolateral craniotomy was used to express Chronos or ChR2 in the cochlear nucleus (CN). Following a four to eight week incubation period, blue light (473 nm) was delivered via an optical fiber placed directly on the surface of the infected CN, and neural activity was recorded in the contralateral inferior colliculus (IC). Both ChR2 and Chronos evoked sustained responses to all stimuli, even at high pulse rates. In addition, optical stimulation evoked excitatory responses throughout the tonotopic axis of the IC. Synchrony of the light-evoked response to stimulus rates of 14-448 pulses/s was higher in Chronos compared to ChR2 mice (p < 0.05 at 56, 168, and 224 pulses/s). Our results demonstrate that Chronos has the ability to drive the auditory system at higher stimulation rates than ChR2 and may be a more ideal opsin for manipulation of auditory pathways in future optogenetic-based neuroprostheses. This article is part of a Special Issue entitled "Lasker Award".

The polymorphisms of the MBL2 and MIF genes associated with Pediatric Cochlear Implant Patients

OBJECTIVES

Mannose-binding lectin and macrophage migration inhibitory factor gene polymorphisms are associated with several acute/chronic autoimmune or inflammatory diseases. The aim of this study was to investigate if there was any association between mannose-binding lectin 2 (MBL2) and macrophage migration inhibitory factor (MIF) gene polymorphisms and profound congenital sensorineural hearing loss in children who underwent cochlear implantation.

METHODS

A total of 62 patients with congenital hearing loss and 80 age- and sex-matched healthy controls were evaluated for codon 54 A/B polymorphisms in MBL2 and the-173 G/C polymorphism in MIF by using the polymerase chain reaction and restriction fragment length polymorphism method.

RESULTS

The frequency of the BB genotype of MBL2 and MIF -173 GC genotype were statistically significantly higher in the patient group than in the controls (p=0.0127, p=0.0408, respectively).

CONCLUSION

In this study, we found that a subject who is homozygous for the variant allele B of codon 54 of the MBL2and heterozygous for variant allele C of -173 MIF has a risk factor for sensorineural hearing loss.

Genetics of hearing and deafness

This article is a review of the genes and genetic disorders that affect hearing in humans and a few selected mouse models of deafness. Genetics is playing an increasingly critical role in the practice of medicine. This is not only in part to the importance that genetic knowledge has on traditional genetic diseases but also in part to the fact that genetic knowledge provides an understanding of the fundamental biological process of most diseases. The proteins coded by the genes related to hearing loss (HL) are involved in many functions in the ear, such as cochlear fluid homeostasis, ionic channels, stereocilia morphology and function, synaptic transmission, gene regulation, and others. Mouse models play a crucial role in understanding of the pathogenesis associated with these genes. Different types of familial HL have been recognized for years; however, in the last two decades, there has been tremendous progress in the discovery of gene mutations that cause deafness. Most of the cases of genetic deafness recognized today are monogenic disorders that can be broadly classified by the mode of inheritance (i.e., autosomal dominant, autosomal recessive, X-linked, and mitochondrial inheritance) and by the presence of associated phenotypic features (i.e., syndromic; and nonsyndromic). In terms of nonsyndromic HL, the chromosomal locations are currently known for ∼ 125 loci (54 for dominant and 71 for recessive deafness), 64 genes have been identified (24 for dominant and 40 for recessive deafness), and there are many more loci for syndromic deafness and X-linked and mitochondrial DNA disorders (http://hereditaryhearingloss.org). Thus, today's clinician must understand the science of medical genetics as this knowledge can lead to more effective disease diagnosis, counseling, treatment, and prevention.

Defining and evaluating success in paediatric cochlear implantation--an exploratory study

OBJECTIVES

This work is a preliminary study that sought to investigate and develop a method for defining and evaluating "success" in paediatric cochlear implantation (PCI) and to apply a process by which a clinical team could optimally achieve this aim.

METHODS

A pilot group of 25 profoundly deaf children who received a unilateral cochlear implant from 1995 to 2008 was used to develop the process. The cases displayed features that are commonly encountered in PCI. Individual case records were examined retrospectively for adverse factors that might impact on the implantation outcome with particular reference to the probability and severity of impact of each factor. Case prognosis was then rated on a 1-4 basis (1: excellent, 2: good, 3: fair, 4: poor). The subsequent outcomes were assessed using standardised speech (GFW, DEAP), language (PLS-4; CELF) and vocabulary (PPVT; EVT) assessments. Auditory performance outcomes were assessed using a new Categories of Auditory Performance Index (CAPI) that incorporated criteria, testing and scoring aspects. Family issues were also evaluated. Case outcomes were rated 1-4 as above and the prognoses and outcomes were then compared.

RESULTS

Accurate prognostication was seen in 14 cases, 5 had better outcomes than expected and 6 obtained poorer results. "Success", where the outcome equalled or exceeded the prognosis, occurred in 19 (76%) of cases. The successful group contained some "limited gains" cases where the results were nonetheless in line with expectations and parental satisfaction. The detrimental effect of delayed implantation was evident; Connexin 26 (GJB2) mutation had little influence. Poor general medical condition and adverse family situations commonly produced poorer outcomes.

CONCLUSIONS

Success in PCI is achieved when the outcome matches or exceeds the pre-operative expectations of the well-counselled family, without adverse side effects. The assessments achieved a good success rate, but further research is required to clearly identify potential problems and a skilled team is needed to evaluate their risk to the PCI outcome. Unforseen events may also intervene. Currently, differing outcome evaluation techniques impede comparison of studies, particularly in the speech and hearing domains. Rationalisation of these is recommended to facilitate future research.

Genetic diagnosis and cochlear implantation for patients with nonsyndromic hearing loss and enlarged vestibular aqueduct

Objective:

To review the genotype and cochlear implantation outcome of patients with nonsyndromic hearing loss and enlarged vestibular aqueduct.

Methods:

Twenty-one Chinese children with nonsyndromic hearing loss and enlarged vestibular aqueduct underwent genetic examination. A DNA microarray was used to screen for the IVS7-2A>G and H723R mutations. Any DNA samples with one or none of the two mutant alleles were sequenced to detect other mutations in the SLC26A4 and FOXI1 genes.

Results:

Twelve SLC26A4 mutations were detected, including three novel mutations. The most common mutations detected were IVS7-2A>G and H723R. Twelve patients received cochlear implants, and subsequently demonstrated excellent speech perception.

Conclusion:

Three novel mutations were detected in Chinese patients with nonsyndromic hearing loss and enlarged vestibular aqueduct. The SLC26A4 mutation spectrum in the Chinese population is similar to that in other East Asian populations. Cochlear implantation is a safe and effective treatment in patients with enlarged vestibular aqueduct.

Cochlear implantation outcomes in children with Waardenburg syndrome

Waardenburg syndrome (WS) is an autosomal dominant disease, characterized by dystopia canthorum, hyperplasia of the eyebrows, heterochromia iridis, white forelock, and congenital sensori-neural hearing loss (SNHL). The aim of this study was to evaluate the outcome of cochlear implantation in children with WS and compare it with children with pure SNHL. In a prospective study we evaluated 336 cochlear implanted children from 2008 to 2010. The WS was diagnosed by its established criteria and for control group children without any dysmorphic features, anatomical, behavioral, and developmental disorders were also enrolled. We evaluated children of both groups 1 year after cochlear implantation by categories of auditory performance (CAP) and speech intelligibility rating (SIR) tests. Eighty-one children out of the total 336 who had SNHL were included in study. Out of these 75 (22.3%) were healthy and six (1.78%) had WS. Of the 75 healthy children 40 (53.3%) were girls, while of the six children with WS, three (50%) were girls. There was a significant difference in SIR between WS and cases with pure SNHL (2.67 ± 1.03 vs. 3.79 ± 1.11, p = 021) however, the difference was not significant in CAP (4 ± 1.26 vs. 5.13 ± 1.13, p = 0.082). Prevalence of WS was 1.78% at Baqiyatallah Cochlear Implant Center. One year after implantation there was no significant difference in auditory outcome; however, the difference in speech outcome was significant between WS and cases with pure SNHL.

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.

The right not to hear: the ethics of parental refusal of hearing rehabilitation

OBJECTIVE

To explore the ethics of parental refusal of auditory-oral hearing rehabilitation.

STUDY DESIGN

Case study with medical ethical discussion and review.

METHODS

Two young brothers present with severe-to-profound congenital sensorineural hearing loss. The parents, both of whom have normal hearing and work as sign language interpreters, have decided to raise their children with American Sign Language as their only form of communication. They have chosen not to pursue cochlear implantation nor support the use of hearing aids.

DISCUSSION

This case raises significant questions concerning whether hearing rehabilitation should be mandated, and if there are circumstances in which parental preferences should be questioned or overridden with regard to this issue. In addition, legal concerns may be raised regarding the possible need to file a report with Child Protective Services. Although similar cases involving the Deaf community have historically favored parental rights to forego hearing rehabilitation with either cochlear implantation or hearing aids, we explore whether conclusions should be different because the parents in this case are not hearing impaired.

CONCLUSIONS

The ethics of parental rights to refuse hearing rehabilitation are complex and strikingly context-dependent. A comprehensive appreciation of the medical, practical, and legal issues is crucial prior to intervening in such challenging situations.