Genetic and Non-genetic Workup for Pediatric Congenital Hearing Loss

Etiology of Childhood Profound Sensorineural Hearing Loss: The Role of Hearing Loss Gene Panel Testing

OBJECTIVE

Establishing the cause of hearing loss (HL) is important and rewarding, though not without its challenges. While our ability to identify the etiology for HL has improved with advances in scientific knowledge, a significant proportion of cases remain of unknown etiology. Recent protocol changes within the NHS Genomic Medicine Service support the utilization of the HL gene panel test, rather than individual gene tests. In light of these changes, determining the yield of these more extensive panel tests is important in informing future practice.

STUDY DESIGN

Retrospective study.

SETTING

The Cochlear Implant (CI) Department at Great Ormond Street Hospital (GOSH).

METHODS

Four hundred seventy-six children with profound HL were identified from a database of referrals to the GOSH CI Department. Data on etiology of HL including genetic diagnosis was collected from hospital notes on an electronic patient records system and hospital genetics database.

RESULTS

We identified a positive result in 163/476 (34%) cases through the gene panel test, representing an additional 19% yield to current level 1 investigations. Genetic HL, including both syndromic (including those not covered by the HL gene panel) and nonsyndromic (209/476, 44%) was the most common etiology in our cohort. Perinatal, intrauterine, ototoxicity, meningitis, and encephalitis categories altogether comprised 97/476 (20%) cases.

CONCLUSION

Gene panel testing provides significant additional yield over current level 1 investigations which include GJB2 testing only. This has far-reaching implications for how we optimize investigations into HL in children and counsel families, and for future early interventions.

Using Xenopus to discover new candidate genes involved in BOR and other congenital hearing loss syndromes

Hearing in infants is essential for brain development, acquisition of verbal language skills, and development of social interactions. Therefore, it is important to diagnose hearing loss soon after birth so that interventions can be provided as early as possible. Most newborns in the United States are screened for hearing deficits and commercially available next-generation sequencing hearing loss panels often can identify the causative gene, which may also identify congenital defects in other organs. One of the most prevalent autosomal dominant congenital hearing loss syndromes is branchio-oto-renal syndrome (BOR), which also presents with defects in craniofacial structures and the kidney. Currently, mutations in three genes, SIX1, SIX5, and EYA1, are known to be causative in about half of the BOR patients that have been tested. To uncover new candidate genes that could be added to congenital hearing loss genetic screens, we have combined the power of Drosophila mutants and protein biochemical assays with the embryological advantages of Xenopus, a key aquatic animal model with a high level of genomic similarity to human, to identify potential Six1 transcriptional targets and interacting proteins that play a role during otic development. We review our transcriptomic, yeast 2-hybrid, and proteomic approaches that have revealed a large number of new candidates. We also discuss how we have begun to identify how Six1 and co-factors interact to direct developmental events necessary for normal otic development.

Genetic screening of 15 hearing loss variants in 77,647 neonates with clinical follow-up

BACKGROUND

To analyze the genotype distribution and frequency of hearing loss genes in newborn population and evaluate the clinical value of genetic screening policy in China.

METHODS

Genetic screening for hearing loss was offered to 84,029 neonates between March 2019 and December 2021, of whom 77,647 newborns accepted the screening program with one-year follow-up. The genotyping of 15 hot spot variants in GJB2, GJB3, SLC26A4, and MT-RNR1 was performed on microarray platform.

RESULTS

A total of 3.05% (2369/77,647) newborns carried at least one genetic hearing loss-associated variant, indicated for early preventive management. The carrier frequency of GJB2 gene was the highest, at 1.48% (1147/77,647), followed by SLC26A4 gene at 1.07% (831/77,647), and GJB3 gene at 0.23% (181/77,647). GJB2 c.235delC variant and SLC26A4 IVS7-2A>G variant were the most common allelic variants with allele frequency of 0.6304% (979/155,294) and 0.3992% (620/155,294), respectively. 10 children are identified as homozygous or compound heterozygous for pathogenic variants (4 in GJB2, 6 in SLC26A4), and 7 of these infants had passed the hearing screening. Following up of the genetically screened newborns revealed that genetic screening detected more hearing-impaired infants than hearing screening alone. Genetic screening helped identify the infants who had passed the initial hearing screening, and reduced time for diagnosis and intervention of hearing aid. In addition, we identified 234 newborns (0.30%, 234/77,647) susceptible to preventable aminoglycoside antibiotic ototoxicity undetectable by hearing screening.

CONCLUSION

We performed the largest-scale neonatal carrier screening for hearing loss genes in Southeast China. Our results indicated that genetic screening is an important complementation to conventional hearing screening. Our practice and experience may facilitate the application and development of neonatal genetic screening policy in mainland China.

A Nationwide Study of GATA2 Deficiency in Italy Reveals Novel Symptoms and Genotype-phenotype Association

GATA2 deficiency is a rare disorder encompassing a broadly variable phenotype and its clinical picture is continuously evolving. Since it was first described in 2011, up to 500 patients have been reported. Here, we describe a cohort of 31 Italian patients (26 families) with molecular diagnosis of GATA2 deficiency. Patients were recruited contacting all the Italian Association of Pediatric Hematology and Oncology (AIEOP) centers, the Hematology Department in their institution and Italian societies involved in the field of vascular anomalies, otorhinolaryngology, dermatology, infectious and respiratory diseases. Median age at the time of first manifestation, molecular diagnosis and last follow-up visit was 12.5 (age-range, 2-52 years), 18 (age-range, 7-64 years) and 22 years (age-range, 3-64), respectively. Infections (39%), hematological malignancies (23%) and undefined cytopenia (16%) were the most frequent symptoms at the onset of the disease. The majority of patients (55%) underwent hematopoietic stem cell transplantation. During the follow-up rarer manifestations emerged. The clinical penetrance was highly variable, with the coexistence of severely affected pediatric patients and asymptomatic adults in the same pedigree. Two individuals remained asymptomatic at the last follow-up visit. Our study highlights new (pilonidal cyst/sacrococcygeal fistula, cholangiocarcinoma and gastric adenocarcinoma) phenotypes and show that lymphedema may be associated with null/regulatory mutations. Countrywide studies providing long prospective follow-up are essential to unveil the exact burden of rarer manifestations and the natural history in GATA2 deficiency.

Audiological profile of deaf and hard-of-hearing children under six years old in the "HI HOPES cohort" in South Africa (2006-2011)

BACKGROUND

This study concerns deaf children under six years in the South African HI HOPES Cohort.

OBJECTIVE

To examine their audiological profile, aetiological risk factors for infant hearing loss as well as the relationship between identification, amplification and socio-economic influences.

DESIGN

Using a cohort design, secondary data analysis of a pre-existing dataset demonstrated adequate representation of South African demographic characteristics.

STUDY SAMPLE

A total of 532 deaf and hard-of-hearing infants enrolled in the HI HOPES early intervention programme in three provinces (2006-2011).

RESULTS

The median age of identification of children with bilateral hearing loss (n = 502) was 24.0 months (IQR = 12-36 months). Infants with aetiological risk factors were identified later than those without risk factors, and the latest age of identification (28.5 months) was for those with three aetiological risk factors (n = 42). The median age of amplification was 32 months with 102 children eligible for amplification at 31.1 months still unamplified. Early identification did not imply early amplification, and the more economically advantaged a Province the smaller the gap between ages of identification and amplification.

CONCLUSIONS

In a field with little population-level evidence, the size, and representativeness of this dataset makes a significant contribution to our understanding of infant hearing loss in South Africa.

Single Versus Multigene Testing for Hereditary Hearing Loss: Use and Costs in a Commercially Insured Cohort

OBJECTIVE

The objectives of this study were to describe trends in single-gene GJB2/6 (connexin 26/30) and multigene hearing loss panel (HLP) testing for hereditary hearing loss using real-world evidence.

STUDY DESIGN

Retrospective study using insurance claims data.

SETTING

Optum Data Mart database from 2015 to 2020.

METHODS

Rates of overall and hearing-specific genetic testing and costs to insurers and patients were reported. Linear regression models were used to assess the proportion of single-gene GJB2/6 testing over time. Additional linear regression models were used to assess changes in costs over time.

RESULTS

From 2015 to 2020, 91,986 children received genetic testing for any indication, of which 601 (0.65%) received hearing-specific tests. The proportion of single-gene GJB2/6 testing remained similar over time (mean difference [MD]: -1.3% per year; 95% confidence interval [CI]: -4.3%, 1.7%), while multigene HLP use increased over time (MD: 4.0% per year; 95% CI: 0.4%, 7.5%). The median charge for single-gene GJB2/6 testing remained constant during the study period (MD: -$34; 95% CI: -$86, $18), while the median charge for multigene HLP decreased during the study period (MD: -$145 per year; 95% CI: -$278, -$12).

CONCLUSION

Compared to molecular testing for GJB2/6, HLPs are becoming more common for hereditary hearing loss. The comprehensiveness of HLP and decreasing costs provide justification for its more widespread adoption moving forward.

Association of sleep duration and noise exposure with hearing loss among Chinese and American adults: two cross-sectional studies

OBJECTIVES

To examine the associations of sleep duration (SPD) and noise exposure with hearing loss (HL) among Chinese and American adults.

DESIGN

Two cross-sectional studies.

SETTING

The National Health and Nutrition Examination Survey (2011-2012), and Zhejiang Chinese participants between 1 January 2018 and 1 November 2021.

PARTICIPANTS

3322 adults from the USA and 4452 adults from Zhejiang, China.

MAIN OUTCOME MEASURES

HL was defined as a pure-tone average >20 dB in the better ear at low frequency (500, 1000 and 2000 Hz), speech frequency (500, 1000, 2000 and 4000 Hz) or high frequency (3000, 4000, 6000 and 8000 Hz). Binary logistic regression analysis quantified the associations between SPD, noise exposure (at work or off-work) and HL.

RESULTS

SPD ≥8 hours/night had an OR of 0.71 (95% CI 0.59 to 0.84) for high-frequency HL vs. an SPD of 6-8 hours/night among the Chinese participants but had an OR of 1.28 (95% CI 1.03 to 1.58) among American participants. Noise exposure (both at work and off-work) was associated with poorer low-frequency (OR 1.58, 1.43; p<0.05), speech-frequency (OR 1.63, 1.29; p<0.05) and high-frequency (OR 1.37, 1.23; p<0.05) hearing among the Chinese participants; and it was associated with worse high-frequency hearing (OR 1.43, 1.66; p<0.05) among the American participants. The negative relationship between SPD ≥8 hours/night and HL was mainly observed in the Chinese participants with noise exposure (OR <1, p<0.05), and SPD ≥8 hours/night associated with poorer HF hearing was only identified in the American participants without noise exposure (OR >1, p<0.05).

CONCLUSIONS

Noise exposure was associated with poorer hearing. SPD ≥8 hours/night was negatively associated with HL in the Chinese participants especially when exposed to noise. SPD ≥8 hours/night was related to poorer high-frequency hearing in the American participants when they had no noise exposure.

Congenital Sensorineural Hearing Loss

Congenital sensorineural hearing loss is highly prevalent in our population, with a wide variety of causes. The key to clinical management is early detection and intervention, to promote language and cognitive development. With expanding genetic knowledge about congenital sensorineural hearing loss, the indiscriminate approach in workup is no longer recommended. Comprehensive genetic evaluation and cytomegalovirus testing are key to identify the underlying cause of the hearing loss. Treatment and prognosis depend on age of hearing loss onset and detection; management plans will typically include audiology consultation, speech therapy, and various hearing amplification devices and technologies when applicable.

Selective Inner Hair Cell Loss in a Neonate Harbor Seal (Phoca vitulina)

Simple Summary

Congenital hearing loss (i.e., hearing impairment present at birth) is recognized in humans and other terrestrial species, but there is a lack of information on congenital malformations and associated hearing loss in pinnipeds (seals, sea lions, and walruses). Baseline knowledge on marine mammal inner ear malformations is essential to differentiate between congenital and acquired abnormalities, which may be caused by infectious agents, age, or anthropogenic interactions, such as noise exposure. Analysis of the cochlea of a neonate harbor seal (Phoca vitulina) revealed bilateral loss of inner hair cells (sensory cells responsible for transducing the auditory signal) while the outer hair cells (sensory cells responsible for sound amplification and frequency selectivity and sensitivity) were intact. The selective inner hair cell loss (up to 84.6% of loss) was more severe in the basal turn, where the high frequencies are encoded. Potential causes and consequences are discussed. This is the first report of a case of selective inner hair cell loss in a marine mammal neonate, likely congenital.

Abstract

Congenital hearing loss is recognized in humans and other terrestrial species. However, there is a lack of information on its prevalence or pathophysiology in pinnipeds. It is important to have baseline knowledge on marine mammal malformations in the inner ear, to differentiate between congenital and acquired abnormalities, which may be caused by infectious pathogens, age, or anthropogenic interactions, such as noise exposure. Ultrastructural evaluation of the cochlea of a neonate harbor seal (Phoca vitulina) by scanning electron microscopy revealed bilateral loss of inner hair cells with intact outer hair cells. The selective inner hair cell loss was more severe in the basal turn, where high-frequency sounds are encoded. The loss of inner hair cells started around 40% away from the apex or tip of the spiral, reaching a maximum loss of 84.6% of hair cells at 80–85% of the length from the apex. Potential etiologies and consequences are discussed. This is believed to be the first case report of selective inner hair cell loss in a marine mammal neonate, likely congenital.

Comprehensive medical evaluation of pediatric bilateral sensorineural hearing loss

Children with bilateral sensorineural hearing loss (SNHL) should undergo a comprehensive medical evaluation to determine the underlying etiology and help guide treatment and counseling. In this article, we review the indications and rationale for medical evaluation of pediatric bilateral SNHL, including history and physical examination, imaging, genetic testing, specialist referrals, cytomegalovirus (CMV) testing, and other laboratory tests. Workup begins with a history and physical examination, which can provide clues to the etiology of SNHL, particularly with syndromic causes. If SNHL is diagnosed within the first 3 weeks of life, CMV testing should be performed to identify patients that may benefit from antiviral treatment. If SNHL is diagnosed after 3 weeks, testing can be done using dried blood spots samples, if testing capability is available. Genetic testing is oftentimes successful in identifying causes of hearing loss as a result of recent technological advances in testing and an ever-increasing number of identified genes and genetic mutations. Therefore, where available, genetic testing should be performed, ideally with next generation sequencing techniques. Ophthalmological evaluation must be done on all children with SNHL. Imaging (high-resolution computed tomography and/or magnetic resonance imaging) should be performed to assess for anatomic causes of hearing loss and to determine candidacy for cochlear implantation when indicated. Laboratory testing is indicated for certain etiologies, but should not be ordered indiscriminately since the yield overall is low.

Overview of Medical Evaluation of Unilateral and Bilateral Hearing Loss in Children

Early identification, treatment, and medical evaluation of childhood hearing loss are essential to promoting language and social development, regardless of their age of presentation. Evaluation of hearing loss in children should prioritize reversible and treatable causes. Multiple algorithms have been established to address the changing prevalence of genetic or infectious contributions to hearing loss and include recommendations on laboratory testing, imaging, and genetic testing. Despite these recommendations, significant practice variation remains on assessing the etiology of hearing loss in children.

Assessment of Hearing Screening Combined With Limited and Expanded Genetic Screening for Newborns in Nantong, China

IMPORTANCE

Early identification and intervention for newborns with hearing loss (HL) may lead to improved physiological and social-emotional outcomes. The current newborn hearing screening is generally beneficial but improvements can be made.

OBJECTIVE

To assess feasibility and evaluate utility of a modified genetic and hearing screening program for newborn infants.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study used a 4-stage genetic and hearing screening program at 6 local hospitals in Nantong city, China. Participants were newborn infants born between January 2016 and June 2020 from the Han population. Statistical analysis was performed from April 1 to May 1, 2021.

EXPOSURES

Limited genetic screening for 15 variants in 4 common HL-associated genes and newborn hearing screening (NHS) were offered concurrently to all newborns. Hearing rescreening and/or diagnostic tests were provided for infants with evidence of HL on NHS or genetic variants on screening. Expanded genetic tests for a broader range of genes were targeted to infants with HL with negative results of limited genetic tests.

MAIN OUTCOMES AND MEASURES

The detection capability for infants with hearing impairment who passed conventional hearing screening, as well as infants with normal hearing at risk of late-onset HL due to genetic susceptibility.

RESULTS

Among a total of 35 930 infants, 32 512 infants completed the follow-up and were included for analysis. Among the infants included in the analysis, all were from the Han population in China and 52.3% (16 988) were male. The modified genetic and hearing screening program revealed 142 cases of HL and 1299 cases of genetic variation. The limited genetic screening helped identify 31 infants who passed newborn hearing screening, reducing time for diagnosis and intervention; 425 infants with normal hearing with pathogenic SLC26A4 variation and 92 infants with MT-RNR1 variation were at risk for enlarged vestibular aqueduct and aminoglycoside-induced ototoxicity respectively, indicating early aversive or preventive management.

CONCLUSIONS AND RELEVANCE

This study found that performing modified genetic and hearing screening in newborns was feasible and provides evidence that the program could identify additional subgroups of infants who need early intervention. These findings suggest an advantage for universal adoption of such a practice.

Identification of Novel Compound Heterozygous MYO15A Mutations in Two Chinese Families with Autosomal Recessive Nonsyndromic Hearing Loss

Congenital deafness is one of the most common causes of disability in humans, and more than half of cases are caused by genetic factors. Mutations of the MYO15A gene are the third most common cause of hereditary hearing loss. Using next-generation sequencing combined with auditory tests, two novel compound heterozygous variants c.2802_2812del/c.5681T>C and c.5681T>C/c.6340G>A in the MYO15A gene were identified in probands from two irrelevant Chinese families. Auditory phenotypes of the probands are consistent with the previously reported for recessive variants in the MYO15A gene. The two novel variants, c.2802_2812del and c.5681T>C, were identified as deleterious mutations by bioinformatics analysis. Our findings extend the MYO15A gene mutation spectrum and provide more information for rapid and precise molecular diagnosis of congenital deafness.