Aetiology of congenital hearing loss: a cohort review of 569 subjects

Spectrum of genetic variants in bilateral sensorineural hearing loss

Background: Hearing loss (HL) is an impairment of auditory function with identified genetic forms that can be syndromic (30%) or non-syndromic (70%). HL is genetically heterogeneous, with more than 1,000 variants across 150 causative genes identified to date. The genetic diagnostic rate varies significantly depending on the population being tested. Countries with a considerably high rate of consanguinity provide a unique resource for studying rare forms of recessive HL. In this study, we identified genetic variants associated with bilateral sensorineural HL (SNHL) using whole-exome sequencing (WES) in 11 families residing in the United Arab Emirates (UAE). Results: We established the molecular diagnosis in six probands, with six different pathogenic or likely pathogenic variants in the genes MYO15A, SLC26A4, and GJB2. One novel nonsense variant, MYO15A:p.Tyr1962Ter*, was identified in a homozygous state in one family, which has not been reported in any public database. SLC26A4 and GJB2 were found to be the most frequently associated genes in this study. In addition, six variants of uncertain significance (VUS) were detected in five probands in the genes CDH23, COL11A1, ADGRV1, NLRP3, and GDF6. In total, 12 variants were observed in eight genes. Among these variants, eight missense variants (66.7%), three nonsense variants (25.0%), and one frameshift (8.3%) were identified. The overall diagnostic rate of this study was 54.5%. Approximately 45.5% of the patients in this study came from consanguineous families. Conclusion: Understanding the genetic basis of HL provides insight for the clinical diagnosis of hearing impairment cases through the utilization of next-generation sequencing (NGS). Our findings contribute to the knowledge of the heterogeneous genetic profile of HL, especially in a population with a high rate of consanguineous marriage in the Arab population.

Recent advances in genetic etiology of non-syndromic deafness in children

Congenital auditory impairment is a prevalent anomaly observed in approximately 2-3 per 1,000 infants. The consequences associated with hearing loss among children encompass the decline of verbal communication, linguistic skills, educational progress, social integration, cognitive aptitude, and overall well-being. Approaches to reversing or preventing genetic hearing loss are limited. Patients with mild and moderate hearing loss can only use hearing aids, while those with severe hearing loss can only acquire speech and language through cochlear implants. Both environmental and genetic factors contribute to the occurrence of congenital hearing loss, and advancements in our understanding of the pathophysiology and molecular mechanisms underlying hearing loss, coupled with recent progress in genetic testing techniques, will facilitate the development of innovative approaches for treatment and screening. In this paper, the latest research progress in genetic etiology of non-syndromic deafness in children with the highest incidence is summarized in order to provide help for personalized diagnosis and treatment of deafness in children.

cdh23 affects congenital hearing loss through regulating purine metabolism

Introduction

The pathogenic gene CDH23 plays a pivotal role in tip links, which is indispensable for mechanoelectrical transduction in the hair cells. However, the underlying molecular mechanism and signal regulatory networks that influence deafness is still largely unknown.

Methods

In this study, a congenital deafness family, whole exome sequencing revealed a new mutation in the pathogenic gene CDH23, subsequently; the mutation has been validated using Sanger sequencing method. Then CRISPR/Cas9 technology was employed to knockout zebrafish cdh23 gene. Startle response experiment was used to compare with wide-type, the response to sound stimulation between wide-type and cdh23-/-. To further illustrate the molecular mechanisms underlying congenital deafness, comparative transcriptomic profiling and multiple bioinformatics analyses were performed.

Results

The YO-PRO-1 assay result showed that in cdh23 deficient embryos, the YO-PRO-1 signal in inner ear and lateral line neuromast hair cells were completely lost. Startle response experiment showed that compared with wide-type, the response to sound stimulation decreased significantly in cdh23 mutant larvae. Comparative transcriptomic showed that the candidate genes such as atp1b2b and myof could affect hearing by regulating ATP production and purine metabolism in a synergetic way with cdh23. RT-qPCR results further confirmed the transcriptomics results. Further compensatory experiment showed that ATP treated cdh23-/- embryos can partially recover the mutant phenotype.

Conclusion

In conclusion, our study may shed light on deciphering the principal mechanism and provide a potential therapeutic method for congenital hearing loss under the condition of CDH23 mutation.

Aetiology of permanent childhood hearing loss at a population level

AIM

To evaluate and describe results of aetiological investigations offered to a population level cohort of babies who had confirmed permanent hearing loss after they either (i) failed universal neonatal hearing screening or (ii) passed newborn screening but were detected with a permanent hearing loss in early childhood.

METHODS

Descriptive analysis of results of investigations offered to neonates and young children in whom permanent hearing loss was detected as part of a statewide newborn hearing screening programme. A total of 306 285 newborns were screened between 2013 and 2017. The failed screening results were confirmed by a diagnostic audiological assessment battery. Medical evaluation for the identification of the cause of the hearing loss was performed by a paediatrician or otolaryngologist, investigations were ordered using a stepwise approach, and aetiology was assigned using a coding scheme.

RESULTS

Permanent hearing loss was confirmed in 967 children (0.3%). Data were available for 873. An aetiological factor was identified or presumed in 61.3% of cases. Genetic causes were present in 26.8% and structural causes were present in 24.9% of cases. Congenital cytomegalovirus was present in 4.4%.

CONCLUSIONS

Use of a coding scheme is feasible at a population level and allows collation of data from multiple sites and will allow outcome mapping and service planning.

Congenital Unilateral Hearing Loss: Characteristics and Etiological Analysis in 121 Patients

OBJECTIVE

To describe the characteristics and etiological analysis in patients with congenital unilateral hearing loss.

STUDY DESIGN

Retrospective cohort analysis.

SETTING

Tertiary referral center.

PATIENTS

Children with permanent congenital unilateral hearing loss born between 2007 and 2018. Patients were referred after universal newborn hearing screening or by a colleague to confirm the diagnosis and perform etiological examinations.

MAIN OUTCOME MEASURES

Hearing loss type, severity, and evolution linked with the results of etiological testing.

RESULTS

In the 121 included children, aural atresia is the leading cause of congenital unilateral hearing loss (32%), followed by structural anomalies (19%) and cCMV (13%), whereas 24% remained idiopathic after etiological work-up. Severity is mainly moderately severe (33% with 56-70 dB hearing loss, majority aural atresia) or profound (31% with > 90 dB hearing loss, predominantly cochlear nerve deficiency). Syndromic features were present in 26%. Although discussed with all parents, only 26% of the children regularly used hearing amplification.

CONCLUSIONS

Congenital conductive unilateral hearing loss is mainly caused by aural atresia, which proportion in congenital unilateral hearing loss proved higher than previously reported. Cochlear nerve deficiency and cCMV are the predominant etiologies of congenital unilateral sensorineural hearing loss. Etiological work-up in affected patients is mandatory as it might impact the approach, and syndromic features should be actively searched for.

Twelve years of neonatal hearing screening: audiological and etiological results

PURPOSE

Most developed countries have implemented some form of universal newborn hearing screening program. Early identification and rehabilitation of congenital hearing loss is important in functional outcome, and the need to identify the cause of hearing impairment has become clear. We aimed to evaluate audiological and etiological outcomes in a large group of patients with failed neonatal hearing screening.

METHODS

We performed a retrospective chart analysis of patients who were referred to our tertiary referral center after failing neonatal hearing screening during a 12-year period (2007-2019). Screening was based on automated auditory brainstem response (AABR) or a combined approach of AABR and auditory steady-state response (ASSR) with chirp stimulus. Extensive audiometric testing was performed to confirm and determine the type and degree of hearing loss. In case of permanent hearing loss, a standardized etiological protocol was followed to determine the cause.

RESULTS

Of the 802 referred newborns, hearing loss was confirmed by diagnostic ABR in 78%. Main causes of hearing loss included otitis media with effusion (56%, higher in patients screened by AABR/ASSR compared to AABR), a genetic disorder (12%), congenital cytomegalovirus infection (cCMV, 5%) and atresia/stenosis of the external ear canal (5%). Of the patients with permanent hearing loss, 15% showed changes in hearing loss severity over time.

CONCLUSION

In the majority of newborns referred after failing universal neonatal hearing screening, hearing loss could be confirmed. The leading cause was reversible hearing loss due to otitis media with effusion, but hearing loss proved permanent in about 35% of referred newborns, with genetics as predominant cause. Follow-up of congenital hearing loss patients is important as deterioration as well as improvement was observed over time.

[Epidemiological study of hearing impairments in children: prevalence, structure, amplification, and social factors]

For the first time, a detailed epidemiological study of hearing impairments (HI) in the children's population of St. Petersburg (n=3098) was conducted. The data on the incidence of HI in children, the distribution of children depending on the degree of hearing loss, HI type, the presence of additional disorders, risk factors for hearing loss were obtained. Only 19% of children with HI were diagnosed in accordance with modern requirements of early care - at the age of 3 months. In children who underwent universal newborn hearing screening the average age of diagnosis was significantly lower than in children who were not screened. Only 54% of HI children use hearing aids (HA) or cochlear implants. Among the children who do not use HA, the main number is children with mild and moderate hearing loss, unilateral hearing loss and otitis media with effusion. A significant part of them should be considered as candidates for amplification according to current recommendations. The average interval between diagnosis and amplification was 15.7 months. Only 5% of children from the entire population of children with HI received early intervention in accordance with the modern time standard: 1 month (detection) - 3 months (diagnosis) - 6 months (amplification). The problems of organizing an effective care for HI children and the directions of its development are discussed: improving newborn hearing screening; introduction the system of informing the citizens and doctors of related specialties (pediatricians, neurologists) in the field of prevention, diagnosis and rehabilitation of HI in children; expansion of genetic testing of children; reducing time of waiting and improving the quality of HA provided to handicapped children.

Congenital Deafness and Recent Advances Towards Restoring Hearing Loss

Congenital hearing loss is the most common birth defect, estimated to affect 2-3 in every 1000 births. Currently there is no cure for hearing loss. Treatment options are limited to hearing aids for mild and moderate cases, and cochlear implants for severe and profound hearing loss. Here we provide a literature overview of the environmental and genetic causes of congenital hearing loss, common animal models and methods used for hearing research, as well as recent advances towards developing therapies to treat congenital deafness. © 2021 The Authors.

Impact of Universal Newborn Hearing Screening on cochlear implanted children in Ireland

OBJECTIVES

Cochlear Implant (CI) is an established treatment for severe to profound hearing loss (HL). Early diagnosis and intervention in HL are crucial in order to provide access to sound and increase the likelihood of spoken language development in pre-lingually deaf children. In April 2011, the Health Service Executive (HSE) implemented the Universal Newborn Hearing Screening (UNHS) in a phased regional basis in Ireland. This study aimed to investigate the general clinical pathway for UNHS referrals to the CI service and to evaluate the impact of earlier referrals via UNHS on functional outcomes in children.

METHODS

The first part of this study constituted a retrospective review of 100 children referred to the National Hearing Implant and Research Centre (NHIRC) via UNHS from November 2011 to December 2016. Implanted children referred via UNHS were categorised into three groups according to their medical status. Their clinical pathway to cochlear implantation was evaluated. Functional outcomes were investigated based on medical and developmental status, respectively. In the second part of this study, developmentally healthy implanted children referred post-UNHS were compared with medically healthy children referred pre-UNHS under the age of four, from January 2005 to June 2011. Current implant status of children, age at referral and functional outcomes were investigated.

RESULTS

Medically healthy children were referred to the NHIRC at an earlier age than the medically complex children (2.8 months vs 5.2 months, p < 0.01) and the children presenting with auditory neuropathy spectrum disorder (ANSD) (2.8 months vs 5.3 months, p < 0.01). On average they attended their first appointment and were implanted at a younger age than the ANSD group (6.1 months vs 10.1 months, p < 0.01; 16.3 months vs 29.4 months, p < 0.001, respectively). Developmentally healthy children had significantly better functional outcomes than children with developmental delays. Children referred via UNHS were referred and implanted at a younger age than those referred pre-UNHS. The former group achieved better Categories of Auditory Performance (CAP) and Speech Intelligibility Rating (SIR) scores 2 years post-implantation.

CONCLUSION

UNHS in Ireland is an important platform for earlier diagnosis and management of congenital HL and our results show that early intervention has a positive impact on functional outcomes in children.

Methodological aspects of testing vestibular evoked myogenic potentials in infants at universal hearing screening program

Motor development in infants is dependent upon the function of the inner ear balance organ (vestibular organ). Vestibular failure causes motor delays in early infancy and suboptimal motor skills later on. A vestibular test for newborns and infants that is applicable on a large scale, safe and cost effective is in demand in various contexts: in the differential diagnosis of early onset hearing loss to determine forms associated with vestibular failure; in early hearing habilitation with cochlear implant, indicating the vestibular predominant side; and in the habilitation of children affected by motor skill disorders, revealing the contribution of a vestibular failure. This work explored the feasibility of cervical vestibular evoked myogenic potentials (VEMP) in conjunction with newborn universal hearing screening program. VEMP was measured after the hearing tests and was evoked by bone-conducted stimuli. Moreover, stimulus delivery was regulated by neck muscle activity, with infants rested unconstrained in their parents´ arms and with the head supported by the operator´s hand. This VEMP protocol showed a high level of feasibility in terms of test viability and result reproducibility. VEMP integrated into the newborn hearing screening program may represent a practical method for large-scale assessment of balance function in infants.

Next-generation sequencing reveals a novel pathological mutation in the TMC1 gene causing autosomal recessive non-syndromic hearing loss in an Iranian kindred

OBJECTIVES

Hearing loss (HL) is the most common sensory-neural disorder with excessive clinical and genetic heterogeneity, which negatively affects life quality. Autosomal recessive non-syndromic hearing loss (ARNSHL) is the most common form of the disease with no specific genotype-phenotype correlation in most of the cases. Whole exome sequencing (WES) is a powerful tool to overcome the problem of finding mutations in heterogeneous disorders.

METHODS

A comprehensive clinical and pedigree examination was performed on a multiplex family from Khuzestan province suffering from hereditary HL. Direct sequencing of GJB2 and genetic linkage analysis of DFNB1A/B was accomplished. WES was utilized to find possible genetic etiology of the disease. Co-segregation analysis of the candidate variant was done. High resolution melting analysis was applied to detect variant status in 50 healthy matched controls.

RESULTS

Clinical investigations suggested ARNSHL in the pedigree. The family was negative for DFNB1A/B. WES revealed a novel nonsense mutation, c.256G > T (p.Glu86*), in TMC1 segregating with the phenotype in the pedigree. The variant was absent in the controls.

CONCLUSION

Here, we report successful application of WES to identify the molecular pathogenesis of ARNSHL in a large family. The novel nonsense TMC1 variant meets the criteria of being pathogenic according to the ACMG-AMP variant interpretation guideline.

Detection of hearing loss in newborns: Definition of a screening strategy in Bogotá, Colombia

OBJECTIVE

To describe the results from the hearing screening protocol adopted in a Hospital in Colombia emphasizing the importance of performing screening on an outpatient basis, when the newborn is more than 24 h old.

METHODS

A prospective study at Hospital Universitario San Ignacio in Bogota, Colombia was carried out, from May 1st, 2016 to Nov 30^th, 2017, the study sample included 2.088 newborns examined using transient otoacoustic emissions.

RESULTS

We obtained written consent from the parents of 1.523 newborns and 24 individuals (1.6%) failed the first stage of the screening, nine cases unilateral and 15 bilateral. A total of nine neonates (0,6%) failed the second screening test, six cases unilateral and three bilateral. Four (0,3%) did not return to the second test. Our false altered screening rate was 0.7%.

CONCLUSIONS

In a developing country with limited human and economic resources, in which newborn early discharge is the norm, a newborn hearing screening program linked to infants' check-ups, that uses otoacoustic emissions after 48 h of life, seems a feasible option compare to the standard US protocol aiming to conduct hearing screening prior to discharge.

The etiological evaluation of sensorineural hearing loss in children

This study aims to evaluate the etiology of pediatric sensorineural hearing loss (SNHL). A total of 423 children with SNHL were evaluated, with the focus on the determination of causative genetic and acquired etiologies of uni- and bilateral SNHL in relation to age at diagnosis and severity of the hearing loss. We found that a stepwise diagnostic approach comprising of imaging, genetic, and/or pediatric evaluation identified a cause for SNHL in 67% of the children. The most common causative finding in children with bilateral SNHL was causative gene variants (26%), and in children with unilateral SNHL, a structural anomaly of the temporal bone (27%). The probability of finding an etiologic diagnosis is significantly higher in children under the age of 1 year and children with profound SNHL.Conclusions: With our stepwise diagnostic approach, we found a diagnostic yield of 67%. Bilateral SNHL often has a genetic cause, whereas in unilateral SNHL structural abnormalities of the labyrinth are the dominant etiologic factor. The diagnostic yield is associated with the age at detection and severity of hearing loss: the highest proportion of causative abnormalities is found in children with a young age at detection or a profound hearing loss. What is Known: • Congenital sensorineural hearing loss is one of the most common congenital disorders • Determination of the cause is important for adequate management and prognosis and may include radiology, serology, and DNA analysis What is New: • Using a stepwise diagnostic approach, causative abnormalities are found in 67% both in uni- and bilateral SNHL, with the highest diagnostic yield in very young children and those suffering from profound hearing loss • Bilateral SNHL often has a genetic cause, whereas in unilateral SNHL structural abnormalities of the labyrinth are the dominant etiologic factor.

Newborn Sequencing in Genomic Medicine and Public Health

The rapid development of genomic sequencing technologies has decreased the cost of genetic analysis to the extent that it seems plausible that genome-scale sequencing could have widespread availability in pediatric care. Genomic sequencing provides a powerful diagnostic modality for patients who manifest symptoms of monogenic disease and an opportunity to detect health conditions before their development. However, many technical, clinical, ethical, and societal challenges should be addressed before such technology is widely deployed in pediatric practice. This article provides an overview of the Newborn Sequencing in Genomic Medicine and Public Health Consortium, which is investigating the application of genome-scale sequencing in newborns for both diagnosis and screening.

Congenital hearing loss

Congenital hearing loss (hearing loss that is present at birth) is one of the most prevalent chronic conditions in children. In the majority of developed countries, neonatal hearing screening programmes enable early detection; early intervention will prevent delays in speech and language development and has long-lasting beneficial effects on social and emotional development and quality of life. A diagnosis of hearing loss is usually followed by a search for an underlying aetiology. Congenital hearing loss might be attributed to environmental and prenatal factors, which prevail in low-income settings; congenital infections, particularly cytomegalovirus infection, are also a common risk factor for hearing loss. Genetic causes probably account for the majority of cases in developed countries; mutations can affect any component of the hearing pathway, in particular, inner ear homeostasis (endolymph production and maintenance) and mechano-electrical transduction (the conversion of a mechanical stimulus into electrochemical activity). Once the underlying cause of hearing loss is established, it might direct therapeutic decision making and guide prevention and (genetic) counselling. Management options include specific antimicrobial therapies, surgical treatment of craniofacial abnormalities and implantable or non-implantable hearing devices. An improved understanding of the pathophysiology and molecular mechanisms that underlie hearing loss and increased awareness of recent advances in genetic testing will promote the development of new treatment and screening strategies.

Aetiologic diagnosis of hearing loss in children identified through newborn hearing screening testing

With the implementation of universal newborn hearing screening (UNHS) programmes and early diagnosis and treatment of hearing problems, the need has clearly emerged to implement and carry out a systematic and coordinated protocol for the aetiological diagnosis of permanent hearing impairment (PHI). Within the framework of the Italian Ministry of Health project CCM 2013 "Preventing Communication Disorders: a Regional Program for early Identification, Intervention and Care of Hearing Impaired Children", it has been decided to consider the problems relative to aetiological diagnosis of child PHI within UNHS programmes. The specific objective was to apply a shared diagnostic protocol that can identify the cause in at least 70% of cases of PHI. For this part of the project, four main recommendations were identified that can be useful for an efficient aetiological diagnosis in children affected by PHI and that can offer valid suggestions to optimise resources and produce positive changes for third-level audiologic centres.