Nongenetic causes of hearing loss

Factors Influencing Intentions of People with Hearing Impairments to Use Augmented Reality Glasses as Hearing Aids

The advent and progression of AR (augmented reality) technology, coupled with the emergence of AR hearing aid glasses, offer a novel opportunity for people with hearing impairments (PHI). This study aims to explore the intention of this population to employ AR hearing aid glasses as their choice of hearing aid device and the specific factors influencing their preference. This study utilized the partial least squares SEM (PLS-SEM) analytical method to create structural equation model for intentions of PHI to use AR glasses as hearing aids. Data were gathered from on-site experiences across multiple locations; a total of 189 valid questionnaires from individuals with varying degrees of hearing disabilities were used for statistical analysis. According to the data analysis results, we discovered that functionality quality, perceived interaction speed, and perceived usability significantly influence communication effectiveness. Further, communication effectiveness positively influences confidence and societal perception, and the latter has a positive impact on information. Both of these factors positively influence behavioral intention. Based on these findings, this study offers design recommendations for AR hearing aid glasses to cater to the specific needs of PHI, aiming to enhance their quality of life. Furthermore, this study provides pivotal insights for the prospective growth of this emerging industry.

Hearing Loss: Genetic Testing, Current Advances and the Situation in Latin America

Congenital hearing loss is the most common birth defect, estimated to affect 2-3 in every 1000 births, with ~50-60% of those related to genetic causes. Technological advances enabled the identification of hundreds of genes related to hearing loss (HL), with important implications for patients, their families, and the community. Despite these advances, in Latin America, the population with hearing loss remains underdiagnosed, with most studies focusing on a single locus encompassing the GJB2/GJB6 genes. Here we discuss how current and emerging genetic knowledge has the potential to alter the approach to diagnosis and management of hearing loss, which is the current situation in Latin America, and the barriers that still need to be overcome.

Neonatal bacterial meningitis: hearing screening and audiological monitoring outcomes

OBJECTIVE

This study reviewed the outcomes of universal newborn hearing screening (UNHS) and ongoing hearing monitoring in children following recovery from neonatal bacterial meningitis to determine (a) whether screening may be a suitable alternative to diagnostic audiology for detecting permanent childhood hearing loss (PCHL) and (b) whether infants who pass UNHS should be monitored throughout childhood.

DESIGN

Retrospective analysis of a UNHS database.

STUDY SAMPLE

Data were extracted from the state-wide UNHS database for all children born in Queensland Australia between 1 September 2004 and 30 June 2020 with the risk factor of bacterial meningitis (in isolation or in combination with other risk factors) identified at the time of the UNHS. This cohort included 231 children.

RESULTS

Results showed that all post-meningitic infants diagnosed with PCHL had a refer result on the UNHS or were medically excluded from screening. Additionally, no cases of PCHL were identified through the targeted surveillance program following a pass result on UNHS.

CONCLUSIONS

UNHS may be sufficient to detect PCHL in post-meningitic neonates and routine audiological monitoring may not be required for children who pass the screen.

Assessing the need for a wearable sign language recognition device for deaf individuals: Results from a national questionnaire

The purpose of this study was to determine how sign language users perceive the sign language recognition (SLR) field, with a focus on gaining perspectives from members of the Canadian Deaf community. A questionnaire consisting of a series of rating and open-ended questions was used to gather perspectives and insights related to a hypothetical SLR device. The survey was distributed to members of the Deaf community, family and friends of Deaf individuals, and service providers, all of whom had some proficiency in American Sign Language (ASL). The average ratings provided by Deaf participants were distributed normally with a right-modal skew in the direction of the positive ratings. Six fundamental concerns about SLR technologies were identified from participants' responses, with the most frequently cited pertaining to the technology's feasibility. In descending order, participants ranked translation accuracy, speed, and comfort as the three most important design characteristics for potential SLR devices. Respondents identified many potential situations in which SLR devices could be used. For a SLR device to be user-centric and culturally appropriate, it is essential that future work in the field integrates perspectives from members of the Deaf community.

Views of Syrian Mothers in Ankara on Infant Hearing Loss: Cross-sectional Survey

Background

Mothers’ awareness of hearing loss, its risk factors, and available detection and intervention choices have been well known to play an essential role in the early detection and intervention of hearing loss.

Objective

To investigate the knowledge and attitude of Syrian mothers toward infant hearing loss, early identification, and intervention.

Methods

The “Maternal Views on Infant Hearing Loss” questionnaire was adapted and translated into Arabic and then administered to 100 Syrian mothers living in different neighborhoods in Ankara within the age range of 18–68 years old. The internal consistency for the main domains of the questionnaire was tested by Cronbach’s alpha coefficient. Descriptive statistics and Spearman’s rank correlation coefficient were used to evaluate the responses.

Results

The highest level of knowledge about the risk factors was about noise exposure (76%), while the lowest level of knowledge was about jaundice (25%). While 98% of the mothers had a positive attitude toward early detection, 97% of them did not mind the early intervention.

Conclusions

The present findings showed the need to improve mothers’ awareness about infant hearing loss risk factors, available detection, and intervention. Such results may help in performing programs that aim to increase awareness about hearing loss.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10995-022-03488-1.

Preimplantation Genetic Diagnosis in Hereditary Hearing Impairment

Sensorineural hearing impairment is a common sensory deficit in children and more than 50% of these cases are caused by genetic etiologies, that is, hereditary hearing impairment (HHI). Recent advances in genomic medicine have revolutionized the diagnostics of, and counseling for, HHI, including preimplantation genetic diagnosis (PGD), thus providing parents-to-be with better reproductive choices. Over the past decade, we have performed PGD using the amplification refractory mutation system quantitative polymerase chain reaction (ARMS-qPCR) technique in 11 couples with a history of HHI, namely eight with GJB2 variants, one with OTOF variants, one with SLC26A4 variants, and one with an MITF variant. We demonstrated that PGD can be successfully applied to HHI of different inheritance modes, namely autosomal dominant or recessive, and phenotypes, namely syndromic or non-syndromic HHI. However, certain ethical concerns warrant scrutiny before PGD can be widely applied to at-risk couples with a history of HHI.

Black Older Americans Have Lower Prevalence of Hearing Loss Than Their White Peers: Findings From Two Large Nationally Representative Surveys

PURPOSE

The purpose of this study was to investigate Black-White differences associated with hearing loss among older adults living in the United States.

METHOD

Secondary data analysis was conducted using the 2017 American Community Survey (ACS) with a replication analysis of the 2016 ACS. The ACS is an annual nationally representative survey of Americans living in community settings and institutions. The sample size of older Americans (age 65+ years) in 2017 was 467,789 non-Hispanic Whites (NHWs) and 45,105 non-Hispanic Blacks (NHBs). In the 2016 ACS, there were 459,692 NHW and 45,990 NHB respondents. Measures of hearing loss, age, race/ethnicity, education level, and household income were based on self-report. Data were weighted to adjust for nonresponse and differential selection probabilities.

RESULTS

The prevalence of hearing loss was markedly higher among older NHWs (15.4% in both surveys) in comparison with NHBs (9.0% in 2017 and 9.4% in 2016, both ethnic differences p < .001). In the 2017 ACS, the age- and sex-adjusted odds of hearing loss were 69% higher for NHWs compared with NHBs, which increased to 91% higher odds when household income and education level were also taken into account (OR = 1.91; 95% confidence interval [CI; 1.85, 1.97]). Findings from the 2016 ACS were very similar (e.g., 65+ fully adjusted OR = 1.81; 95% CI [1.76, 1.87]).

CONCLUSIONS

NHWs have a much higher prevalence and almost double the odds of hearing loss compared with NHBs. Unfortunately, the ACS survey does not allow us to explore potential causal mechanisms behind this association.

Dysmaturation of Premature Brain: Importance, Cellular Mechanisms, and Potential Interventions

Prematurity, especially preterm birth (less than 32 weeks' gestation), is common and associated with high rates of both survival and neurodevelopmental disability, especially apparent in cognitive spheres. The neuropathological substrate of this disability is now recognized to be related to a variety of dysmaturational disturbances of the brain. These disturbances follow initial brain injury, particularly cerebral white matter injury, and involve many of the extraordinary array of developmental events active in cerebral white and gray matter structures during the premature period. This review delineates these developmental events and the dysmaturational disturbances that occur in premature infants. The cellular mechanisms involved in the genesis of the dysmaturation are emphasized, with particular focus on the preoligodendrocyte. A central role for the diffusely distributed activated microglia and reactive astrocytes in the dysmaturation is now apparent. As these dysmaturational cellular mechanisms appear to occur over a relatively long time window, interventions to prevent or ameliorate the dysmaturation, that is, neurorestorative interventions, seem possible. Such interventions include pharmacologic agents, especially erythropoietin, and particular attention has also been paid to such nutritional factors as quality and source of milk, breastfeeding, polyunsaturated fatty acids, iron, and zinc. Recent studies also suggest a potent role for interventions directed at various experiential factors in the neonatal period and infancy, i.e., provision of optimal auditory and visual exposures, minimization of pain and stress, and a variety of other means of environmental behavioral enrichment, in enhancing brain development.

Chronic Auditory Toxicity in Late Preterm and Term Infants With Significant Hyperbilirubinemia

BACKGROUND AND OBJECTIVES

Significant hyperbilirubinemia (SHB) may cause chronic auditory toxicity (auditory neuropathy spectrum disorder and/or sensorineural hearing loss); however, total serum bilirubin (TSB) does not discriminate neonates at risk for auditory toxicity. Our objective was to compare TSB, bilirubin albumin molar ratio (BAMR), and unbound bilirubin (UB) for their association with chronic auditory toxicity in neonates with SHB (TSB ≥20 mg/dL or TSB that met criteria for exchange transfusion).

METHODS

Infants ≥34 weeks' gestational age (GA) with SHB during the first 2 postnatal weeks were eligible for a prospective longitudinal study in India. Comprehensive auditory evaluations were performed at 2 to 3 months of age by using auditory brainstem response, tympanometry, and an otoacoustic emission test and at 9 to 12 months of age by using audiometry. The evaluations were performed by an audiologist unaware of the degree of jaundice.

RESULTS

A total of 93 out of 100 infants (mean GA of 37.4 weeks; 55 boys, 38 girls) who were enrolled with SHB were evaluated for auditory toxicity. Of those, 12 infants (13%) had auditory toxicity. On regression analysis controlling for covariates, peak UB (but not peak TSB or peak BAMR), was associated with auditory toxicity (odds ratio 2.41; 95% confidence interval: 1.43-4.07; P = .001). There was significant difference in the area under the receiver operating characteristic curves between UB (0.866), TSB (0.775), and BAMR (0.724) for auditory toxicity (P = .03) after controlling for covariates.

CONCLUSIONS

Unconjugated hyperbilirubinemia indexed by UB (but not TSB or BAMR) is associated with chronic auditory toxicity in infants ≥34 weeks' GA with SHB.

High Risk Factors Associated With Early Childhood Hearing Loss: A 3-Year Review

PURPOSE

In this study, we examined the association between risk factors for hearing loss and early childhood hearing status (normal hearing, congenital hearing loss, or delayed-onset hearing loss). Follow-up rates of audiologic care following passed or referred birth screens for children with risk factors were also examined.

METHOD

A retrospective data review was completed on 115,039 children born from 2010 to 2012. Data analyses included prevalence rates, odds ratios, and Fisher exact tests of statistical significance.

RESULTS

Ninety percent of children were born with no risk factors for hearing loss; of those, 99.9% demonstrated normal hearing by 3 years of age. Of the 10% of children born with risk factors, 96.3% demonstrated normal hearing by age 3, 1.4% presented with congenital hearing loss, and 2.3% demonstrated permanent hearing loss by age 3. Factors that placed children at the highest risk of congenital hearing impairment were neurodegenerative disorders, syndromes, and congenital infections. Factors that placed children at the highest risk of developing permanent postnatal hearing loss were congenital cytomegalovirus, syndromes, and craniofacial anomalies.

CONCLUSIONS

Certain risk factors place a child at significantly greater risk of congenital hearing impairment or developing permanent hearing loss by age 3. Follow-up diagnostic testing should remain a priority for children with certain risk factors for hearing loss.

Effect of gentamicin and levels of ambient sound on hearing screening outcomes in the neonatal intensive care unit: A pilot study

OBJECTIVE

Hearing loss rates in infants admitted to neonatal intensive care units (NICU) run at 2-15%, compared to 0.3% in full-term births. The etiology of this difference remains poorly understood. We examined whether the level of ambient sound and/or cumulative gentamicin (an aminoglycoside) exposure affect NICU hearing screening results, as either exposure can cause acquired, permanent hearing loss. We hypothesized that higher levels of ambient sound in the NICU, and/or gentamicin dosing, increase the risk of referral on the distortion product otoacoustic emission (DPOAE) assessments and/or automated auditory brainstem response (AABR) screens.

METHODS

This was a prospective pilot outcomes study of 82 infants (<37 weeks gestational age) admitted to the NICU at Oregon Health & Science University. An ER-200D sound pressure level dosimeter was used to collect daily sound exposure in the NICU for each neonate. Gentamicin dosing was also calculated for each infant, including the total daily dose based on body mass (mg/kg/day), as well as the total number of treatment days. DPOAE and AABR assessments were conducted prior to discharge to evaluate hearing status. Exclusion criteria included congenital infections associated with hearing loss, and congenital craniofacial or otologic abnormalities.

RESULTS

The mean level of ambient sound was 62.9 dBA (range 51.8-70.6 dBA), greatly exceeding American Academy of Pediatrics (AAP) recommendation of <45.0 dBA. More than 80% of subjects received gentamicin treatment. The referral rate for (i) AABRs, (frequency range: ∼1000-4000 Hz), was 5%; (ii) DPOAEs with a broad F2 frequency range (2063-10031 Hz) was 39%; (iii) DPOAEs with a low-frequency F2 range (<4172 Hz) was 29%, and (iv) DPOAEs with a high-frequency F2 range (>4172 Hz) was 44%. DPOAE referrals were significantly greater for infants receiving >2 days of gentamicin dosing compared to fewer doses (p = 0.004). The effect of sound exposure and gentamicin treatment on hearing could not be determined due to the low number of NICU infants without gentamicin exposure (for control comparisons).

CONCLUSION

All infants were exposed to higher levels of ambient sound that substantially exceed AAP guidelines. More referrals were generated by DPOAE assessments than with AABR screens, with significantly more DPOAE referrals with a high-frequency F2 range, consistent with sound- and/or gentamicin-induced cochlear dysfunction. Adding higher frequency DPOAE assessments to existing NICU hearing screening protocols could better identify infants at-risk for ototoxicity.

Etiological approach in patients with unidentified hearing loss

OBJECTIVES

Etiological diagnosis of hearing impairment is of great importance to ensure early and adequate management. Even after thorough history taking, clinical and audiometric evaluation, the cause of hearing loss remains unclear in a majority of patients. Further examinations can imply imaging, ophthalmologic investigations, laboratory tests, electrocardiography and genetic testing. Lately, the latter has taken an increasingly prominent place within this diagnostic work-up. However, clear guidelines about optimal implementation and sequence of these tests are required.

METHODS

Records of patients who visited the consultation for otogenetics at Ghent University Hospital (Belgium) during the period 2006-2012 were retrospectively reviewed. In order to optimize the etiological-diagnostic work-up of unidentified hearing loss, application patterns and results of various diagnostic tests, audiometric and etiological data of each patient were collected and analyzed.

RESULTS

Data of 191 patients were analyzed. In 81.2% of the patients, a cause of hearing loss could be determined or suspected. In total, 65.4% had a (presumably) genetic etiology, with connexin 26 (GJB2) mutations as the leading cause. Inquiry of risk factors, associated with congenital hearing loss, and pedigree analysis were found to have the highest diagnostic gain (61.3% and 41.8%). Connexin 26 gene mutations were only present in bilateral hearing impairment, whereas CT abnormalities were related to unilateral (P=0.003), profound (P<0.001) hearing loss. An enlarged vestibular aqueduct was present in 42.9% of all CT abnormalities. Ophthalmologic anomalies were detected in 35.7% of the studied patients.

CONCLUSIONS

A sequential approach for the etiological diagnosis of unidentified hearing loss could determine or suggest a cause in more than 80% of patients. The approach may vary based on the presenting phenotype.

Physical, behavioral, and cognitive effects of prenatal tobacco and postnatal secondhand smoke exposure

The purpose of this review is to examine the rapidly expanding literature regarding the effects of prenatal tobacco and postnatal secondhand smoke (SHS) exposure on child health and development. Mechanisms of SHS exposure are reviewed, including critical periods during which exposure to tobacco products appears to be particularly harmful to the developing fetus and child. The biological, biochemical, and neurologic effects of the small fraction of identified components of SHS are described. Research describing these adverse effects of both in utero and childhood exposure is reviewed, including findings from both animal models and humans. The following adverse physical outcomes are discussed: sudden infant death syndrome, low birth weight, decreased head circumference, respiratory infections, otitis media, asthma, childhood cancer, hearing loss, dental caries, and the metabolic syndrome. In addition, the association between the following adverse cognitive and behavioral outcomes and such exposures is described: conduct disorder, attention-deficit/hyperactivity disorder, poor academic achievement, and cognitive impairment. The evidence supporting the adverse effects of SHS exposure is extensive yet rapidly expanding due to improving technology and increased awareness of this profound public health problem. The growing use of alternative tobacco products, such as hookahs (a.k.a. waterpipes), and the scant literature on possible effects from prenatal and secondhand smoke exposure from these products are also discussed. A review of the current knowledge of this important subject has implications for future research as well as public policy and clinical practice.

[Etiologic profile of severe and profound sensorineural hearing loss in children in the region of north-central Morocco]

Introduction

Le diagnostic d'une surdité profonde est possible dès les premiers jours de vie. Or, le développement du langage et l'intégration scolaire et professionnelle ne sont pas possible que si la surdité est prise en charge précocement. L’établissement d'un diagnostc étiologique a des implications pronostiques et thérapeutiques.

Méthodes

C'est une étude rétrospective allant de Juin 2009 au mois de Janvier 2012 ayant recensé 250 cas d'enfants porteurs d'une surdité sévère et profonde.

Résultats

La moyenne d’âge au moment de l'annonce du diagnostic est de 3.7 ans. Les étiologies prédominantes sont les surdités génétiques dans 35.6% suivies des surdités acquises dans 30.8% des cas. Dans 34.4% des cas aucune étiologie n'a pu être retrouvée.

Conclusion

Cette étude met en évidence la prédominance éventuelle de causes génétiques de la surdité neurosensorielle de l'enfant au Maroc, et souligne la nécessité d'améliorer les politiques de prévention des maladies infectieuses et de dépistage de la surdité néonatale. Cependant, des analyses moléculaires plus ciblées et la réalisation d'un scanner des rochers systématiques sont nécessaires pour évaluer plus précisément la contribution des étiologies génétiques.

Hearing and speech impairment at age 4 and risk of later non-affective psychosis

BACKGROUND

Schizophrenia often becomes manifest in late adolescence and young adulthood but deviations in physical and behavioural development may already be present in childhood. We investigated the relationship between hearing impairment (measured with audiometry) and speech impairment (broadly defined) at age 4 years and adult risk of non-affective psychosis.

METHOD

We performed a population-based, case–control study in Sweden with 105 cases of schizophrenia or other non-affective psychoses and 213 controls matched for sex, date and place of birth. Information on hearing and speech impairment at age 4, along with potential confounding factors, was retrieved from Well Baby Clinic (WBC) records.

RESULTS

Hearing impairment [odds ratio (OR) 6.0, 95% confidence interval (CI) 1.6–23.2] and speech impairment (OR 2.6, 95% CI 1.4–4.9) at age 4 were associated with an increased risk of non-affective psychotic illness. These associations were mutually independent and not explained by parental psychiatric history, occupational class or obstetric complications.

CONCLUSIONS

These results support the hypothesis that psychosis has a developmental aspect with presentation of antecedent markers early in childhood, long before the disease becomes manifest. Our findings add to the growing evidence that early hearing impairment and speech impairment are risk indicators for later non-affective psychosis and possibly represent aetiological clues and potentially modifiable risk factors. Notably, speech impairment and language impairment are both detectable with inexpensive, easily accessible screening.

Genome-wide analysis reveals a novel autosomal-recessive hearing loss locus DFNB80 on chromosome 2p16.1-p21

Hearing impairment (HI) is the decreased ability to hear and discriminate among sounds. It is one of the most common birth defects. Epidemiological data show that more than one child in 1000 is born with HI, whereas more than 50% of prelingual HI cases are found to be hereditary. So far, 95 published autosomal-recessive nonsyndromic HI (ARNSHI) loci have been mapped, and 41 ARNSHI genes have been identified. In this study, we performed a genome-wide linkage study in a consanguineous Tunisian family, and report the mapping of a novel ARNSHI locus DFNB80 to chromosome 2p16.1-p21 between the two single-nucleotide polymorphisms rs10191091 and rs2193485 with a maximum multipoint logarithm of odds score of 4.1. The screening of seven candidate genes, failed to reveal any disease-causing mutations.

Molecular diagnosis of hearing loss

This unit discusses an approach to identifying a genetic etiology in an individual with nonsyndromic hearing loss. The unit begins with a discussion of the decision-making process that can be used to determine whether specific genes and/or a large gene panel should be used for molecular diagnosis of a patient presenting with nonsyndromic hearing loss. Next, two protocols are presented: (1) a full gene-sequencing assay to identify mutations in the GJB2 gene (encoding connexin 26), the most common cause of congenital hearing loss, and (2) an assay to detect the presence of the GJB6-D13S1830 deletion, a 342-kb deletion that causes hearing loss in homozygosity or in combination with a single GJB2 mutation. Finally, the unit ends with a strategy for determining the clinical significance of the test results, which can be challenging given the extensive genetic heterogeneity associated with hearing loss.

A systematic review of pediatric sensorineural hearing loss in congenital syphilis

INTRODUCTION

Congenital syphilis is a known cause of progressive sensorineural hearing loss. The prevalence of syphilitic sensorineural hearing loss (SNHL) in childhood is not clearly defined.

OBJECTIVE

To determine the frequency and characteristics of pediatric SNHL following intrauterine infection with or exposure to Treponema pallidum in order to develop evidence-based guidelines for audiologic monitoring.

DATA SOURCES

Medline (1950-March 2008), EMBASE (1980-March 2008), CINAHL (1982-March 2008), BIOSIS Previews (1969-March 2008), and Cochrane databases. Manual search of references of identified articles and book chapters.

STUDY SELECTION

Articles with an inception cohort of children infected with T. pallidum during pregnancy, positive serological identification of syphilis infection in the antenatal period or pathognomonic clinical signs of congenital syphilis infection, and longitudinal serial audiologic evaluations to identify the prevalence and progression of SNHL.

DATA EXTRACTION

Patient information, maternal and infant serologic status, and audiometric data extracted in an independent fashion. Discrepancies resolved through mutual consensus.

DATA SYNTHESIS

Descriptive statistics.

RESULTS

One prospective cohort study met the inclusion criteria. No cases of SNHL in infants with early congenital syphilis treated with antibiotics in the neonatal period were identified.

CONCLUSIONS

There have been no reports of children with confirmed congenital SNHL secondary to in utero syphilis infection. Newborns with positive syphilis serology should have hearing screening performed at birth and receive treatment with an appropriate course of penicillin therapy. Longitudinal hearing screening is recommended for all pediatric patients with congenital syphilis, as further studies documenting longitudinal audiometric data for patients previously treated either fully or partly for congenital syphilis are required.

NICU noise and the preterm infant

Premature infants in the NICU are often exposed to continuous loud noise despite research documenting the presence and damaging effects of noise on the preterm infant's development. Excessive auditory stimulation creates negative physiologic responses such as apnea and fluctuations in heart rate, blood pressure, and oxygen saturation. Preterm infants exposed to prolonged excessive noise are also at increased risk for hearing loss, abnormal brain and sensory development, and speech and language problems. Reducing noise levels in the NICU can improve the physiologic stability of sick neonates and therefore enlarge the potential for infant brain development. Recommendations include covering incubators with blankets, removing noisy equipment from the incubator environment, implementing a quiet hour, educating staff to raise awareness, and encouraging staff to limit conversation near infants.

Etiologies of hearing impairment among infants and toddlers: 1986-1987 versus 2001

OBJECTIVE

This study compares etiological factors for hearing loss, relevant neuro-sensory impairments and demographics between two groups of children referred for early hearing habilitation in Israel. Group I was referred in the years 1986-1987 (n=73) and group II was referred during 2001 (n=73).

METHODS

Family history, pregnancy, risk factors, developmental milestones, medical history, auditory brainstem response, tympanometry, otoacoustic emissions and behavioral audiometric results were retrospectively retrieved in 2003 from medical records at the MICHA Society for Deaf Children in Israel.

RESULTS

New referrals per year have doubled themselves over the 15 years that elapsed between 1986-1987 and 2001. No changes in gender and age at time of admission were found. The prevalence of mild-to-moderate hearing loss was higher in Group II while severe and profound hearing loss was more prevalent in Group I. Assisted reproductive technologies were involved only in Group II. There were more twin births and post-natal hypoxia in Group II. Rh incompatibility was reported only in Group I. Severe hearing loss was associated with younger age at admission. No significant associations were found between age at admission and etiology with the exception of the fact that children with genetic background were admitted at an earlier age. Since no significant association between genetic background and severity of hearing loss was found, it is conclude that the association between severity of hearing loss and age at admission did not account for changes in etiology in our sample.

CONCLUSIONS

Classic risk factors for hearing loss among infants and toddlers have not changed much over time, and the few changes that have been noticed are probably due to expanded medical knowledge and improved technologies.

A Model for Auditory Brain Stem Implants: Bilateral Surgical Deafferentation of the Cochlear Nuclei in the Macaque Monkey

BACKGROUND

Patients with extensive bilateral lesions of the auditory nerve have a profound and irreversible sensorineural hearing loss (SNHL), which can only be overcome with individually-fitted auditory brain stem implants that directly stimulate the cochlear nuclei. Despite the enormous potential of this increasingly applied treatment, the auditory performance of many implanted patients is limited, and the variability between cases hinders a complete understanding of the role played by the multiple parameters related to the efficacy of the implant.

OBJECTIVES

To mimic the condition of patients who have bilateral lesions of the auditory nerve, we developed an experimental model of bilateral deafferentation of the cochlear nuclei by surgical transection of the cochlear nerves of adult primates.

MATERIALS AND METHODS

We performed bilateral transection of the cochlear nerves of six adult, healthy, male captive-bred macaques (Macaca fascicularis). Before surgery, brain stem auditory evoked potentials were recorded. The histological material obtained from these animals was compared with similarly processed sections from seven macaques with intact cochlear nerves. The surgical technique, similar to that used in human neuro-otology, combined a labyrinthectomy and a neurectomy of the cochlear nerves, and caused deafness. We analyzed immunocytochemically the expression in cochlear nerve fibers of neurofilaments (SMI-32), and cytosolic calcium binding proteins calretinin, parvalbumin and calbindin, and also applied a histochemical reaction for acetylcholinesterase.

RESULTS

None of the primates had any major complications due to the surgical procedure. The lesions produced massive anterograde degeneration of the cochlear nerves, evidenced by marked gliosis and by loss of both type I fibers (which in this species are immunoreactive for calretinin, parvalbumin and neurofilaments) and type II fibers (which are acetylcholinesterase positive). The model of surgical transection described herein causes extensive damage to the cochlear nerves while leaving the cochlea intact, thus mimicking the condition of patients with profound SNHL due to bilateral cochlear nerve degeneration.

CONCLUSIONS

The phylogenetic proximity of primates to humans, and the paramount advantage of close anatomical and physiological similarities, allowed us to use the same surgical technique applied to human patients, and to perform a thorough evaluation of the consequences of neurectomy. Thus, bilateral surgical deafferentation of the macaque cochlear nuclei may constitute an advantageous model for study of auditory brain stem implants.

A novel locus for autosomal recessive nonsyndromic hearing impairment, DFNB63, maps to chromosome 11q13.2-q13.4

Hereditary hearing impairment is a genetically heterogeneous disorder. To date, 49 autosomal recessive nonsyndromic hearing impairment (ARNSHI) loci have been described, and there are more than 16 additional loci announced. In 25 of the known loci, causative genes have been identified. A genome scan and fine mapping revealed a novel locus for ARNSHI (DFNB63) on chromosome 11q13.2-q13.4 in a five-generation Turkish family (TR57). The homozygous linkage interval is flanked by the markers D11S1337 and D11S2371 and spans a 5.3-Mb interval. A maximum two-point log of odds score of 6.27 at a recombination fraction of theta = 0.0 was calculated for the marker D11S4139. DFNB63 represents the eighth ARNSHI locus mapped to chromosome 11, and about 3.33 Mb separate the DFNB63 region from MYO7A (DFNB2/DFNB11). Sequencing of coding regions and exon-intron boundaries of 13 candidate genes, namely SHANK2, CTTN, TPCN2, FGF3, FGF4, FGF19, FCHSD2, PHR1, TMEM16A, RAB6A, MYEOV, P2RY2 and KIAA0280, in genomic DNA from an affected individual of family TR57 revealed no disease-causing mutations.

Congenital hearing impairment

Establishing the etiology of congenital hearing impairment can significantly improve treatment for certain causes of hearing loss and facilitates genetic counseling. High-resolution CT and MRI have contributed to the evaluation and management of hearing impairment. In addition, with the identification of innumerable genetic loci and genetic defects involved in hearing loss, genetic testing has emerged as an invaluable tool in the assessment of hearing impairment. Some of the common forms of congenital hearing loss are reviewed and their imaging features illustrated.

[Hypoacusis after the neonatal period. Situations requiring hearing assessment]

INTRODUCTION

Because hearing plays a major role in language development, pediatric hypoacusis is especially damaging. The high frequency of hearing impairment in newborns and the need for an early diagnosis have led to the establishment of neonatal screening. Nevertheless, there are other situations which may compromise hearing quality in later stages and it is essential to identify them in order to be able to provide early and effective treatment.

OBJECTIVES

To describe the most frequent reasons for referring patients for hearing evaluation to a third level hospital and to identify common situations that require hearing assessment among the pediatric population.

PATIENTS AND METHODS

The clinical histories of 197 non-neonates evaluated for hypoacusis were reviewed. Clinical parameters and diagnosis were compared in patients with impaired and normal hearing.

RESULTS

One hundred sixty-one patients had no previous known hypoacusis. The main reason for evaluation was suspicion by the family or child minder (53.4 %), followed by language underdevelopment. In the first examinations 78 children had hypoacusis (48.4 %), which was more frequently bilateral than unilateral. In 29.5 % of hypoacusic patients, the disease was related to recurrent otitis or adenoiditis and in 25.6 % it was genetic. The most frequent antecedent was deaf relatives in hypoacusic patients and abnormal phenotypes in children with normal hearing. Three patients with previous bacterial meningitis were studied and two of these had hypoacusis.

CONCLUSIONS

Hypoacusic evaluation outside the context of newborn screening is mainly motivated by clinical suspicion of hypoacusis or language underdevelopment. Other situations such as recurrent otitis with effusion, syndromic phenotypic characteristics or bacterial meningitis are related to hearing problems and therefore require detailed evaluation.

A novel D458V mutation in the SANS PDZ binding motif causes atypical Usher syndrome

Homozygosity mapping and linkage analysis in a Turkish family with autosomal recessive prelingual sensorineural hearing loss revealed a 15-cM critical region at 17q25.1-25.3 flanked by the polymorphic markers D17S1807 and D17S1806. The maximum two-point lod score was 4.07 at theta=0.0 for the marker D17S801. The linkage interval contains the Usher syndrome 1G gene (USH1G) that is mutated in patients with Usher syndrome (USH) type 1g and encodes the SANS protein. Mutation analysis of USH1G led to the identification of a homozygous missense mutation D458V at the -3 position of the PDZ binding motif of SANS. This mutation was also present homozygously in one out of 64 additional families from Turkey with autosomal recessive nonsyndromic hearing loss and heterozygously in one out of 498 control chromosomes. By molecular modeling, we provide evidence that this mutation impairs the interaction of SANS with harmonin. Ophthalmologic examination and vestibular evaluation of patients from both families revealed mild retinitis pigmentosa and normal vestibular function. These results suggest that these patients suffer from atypical USH.

In utero exposure to polychlorinated biphenyls and sensorineural hearing loss in 8-year-old children

Early-life exposure to polychlorinated biphenyls (PCBs), a ubiquitous environmental contaminant, increases the hearing threshold at selected frequencies in rats. Among humans from the Faroe Islands with unusually high early-life PCB exposure, exposure was directly associated with increased hearing thresholds at two frequencies, although the deficits were present in the left ear but not the right. We examined PCB levels in maternal pregnancy serum in relation with audiometrically determined hearing thresholds among offspring when they were of school age. Complete data were available for 195 children with sensorineural hearing loss (SNHL) and 615 children selected at random, all of whom were born in 1959-1966 in the Collaborative Perinatal Project (CPP) U.S. cohort. The median exposure among those selected at random, as reflected by the mother's third trimester serum total PCB concentration, was 2.8 microg/l, about twofold higher than recent background levels in the United States. Based on the average hearing threshold across the frequencies essential for speech recognition in the "worst ear," the maternal serum PCB level was unrelated to the adjusted odds of SNHL or to adjusted mean hearing threshold. Overall, an adverse effect of early-life, background-level PCB exposure on SNHL was not supported by these data.