Prevalence and etiology of bilateral sensorineural hearing impairment in a Finnish childhood population

A systematic review of the prevalence of late identified hearing loss in childhood

OBJECTIVES

The objective of this systematic review was to assess the evidence about the prevalence of permanent hearing loss for children not identified from newborn hearing screening (NHS).

DESIGN

Articles were grouped into three categories based on the methodological approach: (1) all participants received diagnostic testing, (2) otoacoustic emission (OAE) or pure tone screening was completed and those not passing were referred for a diagnostic test, and (3) data were retrieved from archival records. Study characteristics, prevalence, and contextual factors were synthesised and narratively described.

STUDY SAMPLE

30 peer-reviewed articles.

RESULTS

Prevalence of permanent hearing loss per 1,000 children ranged from 0.32 to 77.87 (M = 7.30; SD = 16.87). Variations in the criteria for inclusion contributed to prevalence differences. Prevalence was higher when unilateral and milder degrees of hearing loss were included, and older children had higher prevalence (M = 13.71; SD = 23.21) than younger children (M = 1.57; SD = 0.86).

CONCLUSION

There is scant research on prevalence of childhood hearing loss after NHS that utilised methods to accurately differentiate between permanent and temporary hearing loss. Rigorous research is needed on the prevalence of permanent childhood hearing loss to inform strategies for monitoring, identification, intervention, and management.

Imaging in pediatric bilateral sensorineural hearing loss: Diagnostic yield with computed tomography versus magnetic resonance imaging

OBJECTIVES

To evaluate the findings and compare the diagnostic yield of computed tomography (CT) versus magnetic resonance imaging (MRI) in children with bilateral sensorineural hearing loss (BSNHL).

STUDY DESIGN

Multi-institutional retrospective review.

SETTING

Three tertiary referral centers.

METHODS

A multi-institutional retrospective chart review was performed in patients under the age of 18 years with BSNHL (diagnosis codes 389.00-389.22) who underwent both CT and MRI from 2010 to 2012. An abnormal imaging finding was defined as an abnormality of the cochleovestibular or central nervous system known to directly correlate with sensorineural hearing loss. Diagnostic yield of CT versus MRI was compared by McNemar's test.

RESULTS

Of 2081 charts reviewed, 313 patients met inclusion criteria. The diagnostic yield of CT and MRI were 25% and 18%, respectively. Approximately one-quarter of patients had an abnormal finding on CT or MRI. The concordance rate was 92%. CT was more likely to yield an abnormal finding versus MRI (p-value = 0.0001). The most common findings on CT were cochlear and semicircular canal abnormalities. On MRI, the most common findings were cochlear nerve aplasia/hypoplasia and semicircular canal abnormalities.

CONCLUSIONS

This study evaluates and directly compares the diagnostic yield of CT versus MRI for pediatric BSNHL. While both modalities have important and often complementary diagnostic utility, CT had superior diagnostic yield in identifying abnormalities associated with BSNHL.

Aetiologies of profound bilateral sensorineural hearing loss among children in Ekiti State, South Western Nigeria

Introduction

a strong need exists for the knowledge of aetiologies of diseases as this will guide the clinicians on the strategies for their treatment and prevention. In this study, we determined the aetiologies of profound bilateral sensorineural hearing loss (pbSNHL) with a view to provide the relevant data needed for preventive and therapeutic intervention among children in Ekiti State, South Western Nigeria.

Methods

medical records of children with pbSNHL seen over a ten-year period were analysed.

Results

in all, records of 142 children with pbSNHL were analysed. The results showed spectrum of aetiologies that were similar to those reported decades ago with the 'unknown' assuming a recurring decimal. Of the known (acquired) cases, measles takes up the largest 'chunk' with a prevalence of 45.8%. Twenty-eight (32.2%) of those with febrile illnesses had treated their fever with ototoxic antibiotics. Late diagnosis was characteristic of the pbSNHL.

Conclusion

this study shows that there hasn't been any significant shift in the common causes of pbSNHL. Of great concern is the persistence of the 'unknown' causes which assumes a recurring decimal in this and previous studies. Also worrisome is the high prevalence of measles-induced pbSNHL despite the availability of anti-measles vaccine. We therefore suggest effective immunization against measles and other vaccine-preventable causes of pbSNHL. The need for intensive research on the unknown causes of pbSNHL is hereby stressed. Also recommended is routine hearing assessment for survivors of febrile conditions so as to detect, if any, hearing loss promptly.

Does the involvement of first-year residents have a negative impact on the performance of a newborn hearing screening program?

OBJECTIVES

We aimed to evaluate the efficiency of our hearing screening program, prior to hospital discharge, together with the consistency of our teamwork including first year residents by assessing a learning curve for the operators involved.

METHODS

We evaluated all the data collected during the first stage of the screening program of all non-NICU neonates from March 2009 to July 2013, analyzing by means of a linear regression model, the monthly referral rate for the whole period of activity of each group of residents.

RESULTS

performances of each group of screeners were statistically different (chi square test p < 0.005). The nptrend test showed that group 2 (p = 0.01) and group 4 (p = 0.01) reached a statistical significance in higher and lower referral rates respectively. No statistical differences were found in other groups (Group 1 p = 0.161; Group 3 p = 0.853).

CONCLUSION

Despite a statistically significant difference in the performances between the groups of residents, the referral rates for each group (range 6.18%-9.29%) and the overall referral rate for the whole period (7.84%) agree with the values commonly reported for TEOAEs in the literature. It means that our screening program is reasonably effective despite a yearly turnover of operators.

A conceptual framework for rationalized and standardized Universal Newborn Hearing Screening (UNHS) programs

Congenital hearing loss is the most frequent birth defect. The American Academy of Pediatrics and the Joint Committee on Infant Hearing established quality of care process indicators for Universal Newborn Hearing Screening starting from 1999. In a previous systematic review of Universal Newborn Hearing Screening studies we highlighted substantial variability in program design and in reported performance data. In order to overcome these heterogeneous findings we think it is necessary to optimize the implementation of Universal Newborn Hearing Screening programs with an appropriate application of the planning, executing, and monitoring, verifications and reporting phases. For this reason we propose a conceptual framework that logically integrates these three phases and, consequently, a tool (a check-list) for their rationalization and standardization.Our paper intends to stimulate debate on how to ameliorate the routine application of high quality Universal Newborn Hearing Screening programs. The conceptual framework is proposed to optimize, rationalise and standardise their implementation. The checklist is intended to allow an inter-program comparison by removing heterogeneity in processes description and assessment.

Evaluating reporting and process quality of publications on UNHS: a systematic review of programmes

Background

Congenital hearing loss is one of the most frequent birth defects, and Early Detection and Intervention has been found to improve language outcomes. The American Academy of Pediatrics (AAP) and the Joint Committee on Infant Hearing (JCIH) established quality of care process indicators and benchmarks for Universal Newborn Hearing Screening (UNHS). We have aggregated some of these indicators/benchmarks according to the three pillars of universality, timely detection and overreferral. When dealing with inter-comparison, relying on complete and standardised literature data becomes crucial.

The purpose of this paper is to verify whether literature data on UNHS programmes have included sufficient information to allow inter-programme comparisons according to the indicators considered.

Methods

We performed a systematic search identifying UNHS studies and assessing the quality of programmes.

Results

The identified 12 studies demonstrated heterogeneity in criteria for referring to further examinations during the screening phase and in identifying high-risk neonates, protocols, tests, staff, and testing environments. Our systematic review also highlighted substantial variability in reported performance data. In order to optimise the reporting of screening protocols and process performance, we propose a checklist. Another result is the difficulty in guaranteeing full respect for the criteria of universality, timely detection and overreferral.

Conclusions

Standardisation in reporting UNHS experiences may also have a positive impact on inter-program comparisons, hence favouring the emergence of recognised best practices.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-015-0404-x) contains supplementary material, which is available to authorized users.

Screening, rubella vaccination, and childhood hearing impairment in Taiwan

Childhood hearing impairment (CHI) is a major developmental disability, but data at the national level are limited, especially those on the changes in the prevalence over time. In Taiwan, the government began to certify disabled residents for providing various services in 1980 and maintains a registry of certified cases, which provides a rare opportunity for studying the trends of CHI prevalence. Using the registry data, we estimated the prevalence of CHI by age and severity and explored factors affecting its changes over time. From 2000 to 2011, the registered cases under 17 years old ranged from 3427 to 4075. The overall prevalence increased from 2000 to 2006, but then decreased till 2011. While the prevalence of mild CHI increased over the years, such a pattern was not observed in moderate or severe CHI. In general, the overall prevalence increased over the years in the age groups <3 years, 3-5 years, and 6-11 years (p<0.01), and the largest increase was observed in the age group <3 years, particularly after the promotion of screening by the government in 2003. The decrease after 2006 was mainly attributable to decreases in the age groups 12-14 (with a decreasing trend from 2001, p<0.01) and 15-17 years (with a decreasing trend from 2004, p<0.01). The timing was related to the implementation of a nationwide rubella vaccination program. Similar decreases had been observed in countries with rubella vaccination programs.

Investigação etiológica da deficiência auditiva em neonatos identificados em um programa de triagem auditiva neonatal universal

Objetivo descrever os resultados da investigação etiológica da deficiência auditiva realizada em neonatos rastreados em um programa de triagem auditiva neonatal universal. Métodos estudo descritivo, transversal e prospectivo. Foram incluídos no estudo todos os neonatos diagnosticados com deficiência auditiva identificados em um programa de triagem auditiva neonatal universal no período de agosto de 2003 a dezembro de 2006. A provável etiologia da deficiência auditiva foi determinada após anamnese detalhada realizada pelo médico otorrinolaringologista; pesquisa das sorologias para toxoplasmose, rubéola, citomegalovírus, herpes, sífilis e HIV; tomografia dos ossos temporais e exames genéticos. Resultados foram diagnosticados 17 sujeitos com deficiência auditiva no período estudado. 64.7% dos casos estudados apresentaram como provável etiologia causas pré-natais, 29.4% causas peri-natais e um sujeito (5,9%) apresentou etiologia desconhecida. Das causas pré-natais, 36.4% tiveram origem genética confirmada e 36.4% etiologia presumida de hereditariedade. Foi confirmada a presença de infecções congênitas em 18.2% dos casos e um sujeito (9%) apresentou anomalia craniofacial como provável etiologia. O grau de perda auditiva mais frequente observado nos sujeitos estudados foi o profundo (47,1%). Conclusão a maior ocorrência de etiologias observada neste estudo foram as de origem pré-natal, seguida das de origem peri-natal.

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.

Hearing level in children with Down syndrome at the age of eight

This study examines the prevalence of hearing loss in children with Down syndrome at the age of 8. All children were examined in the ENT-departments of public hospitals in Norway and the study population consisted of children born in Norway in 2002 with Down syndrome. Hearing loss was defined as pure-tone air-conduction reduction by on average more than 25 dB HL in the best hearing ear. A cross sectional clinical and audiological population based study was chosen as study design. Hearing loss more than 25 dB HL in the best hearing ear was found in 17/49 children (35%). Mild hearing loss was found in 13 children (26%), moderate in 3 (6%) children and severe hearing loss in 1 child (2%). Conductive hearing loss was found in 8 children (16%), 9 children (18%) had a sensory-neural hearing loss, and mixed hearing loss was found in 3 children. Mean hearing level among boys and girls were 30.0 dB HL (SD 15.7) and 25.5 dB HL (SD13.7) respectively, a non-significant difference (p=0.139). In conclusion this study indicates that both conductive and sensorineural hearing loss, is still common in children with Down syndrome children at the age of eight and as much as two thirds of the children may have a bilateral impairment. The study population was under diagnosed in terms of hearing loss and thus our findings underline the importance of continuous audiological follow up of this group of children throughout childhood.

Prevalence and etiology of congenital or early acquired hearing impairment in Eastern Finland

OBJECTIVE

The purpose of this study was to determine the prevalence and etiology of congenital or early acquired bilateral sensorineural hearing impairment (SNHI) in children born from 1988 to 2002 in the district of Kuopio University Hospital, Finland, and to compare the results with those from an earlier 14-year period in the same region and similar population.

METHODS

The data were collected retrospectively from Hospital Records. The degree of hearing impairment was based on average air conduction threshold calculated over the frequencies 0.5, 1, 2 and 4 kHz in the better hearing ear. Hearing impairment was classified as mild (≥ 20-39 dB), moderate (40-69 dB), severe (70-95 dB) and profound (>95 dB).

RESULTS

We identified 92 children with bilateral SNHI diagnosed before the age of 7 years. The overall prevalence and the prevalence for at least moderate SNHI was 2.1 per 1000 live births and 1.2 per 1000 live births, respectively. We found no differences in the prevalence of SNHI during both study periods. Etiology was genetic in 46%, acquired in 14% and unknown in 40%. Out of the genetic cases 74% were non-syndromic and 26% were syndromic. In comparison to the previous study there was a decline in the proportion of acquired SNHI and the proportion of genetic and unknown cause had increased. Six children in five families had homozygous 35delG mutation and six children in four families presented with a homozygous M34T mutation.

CONCLUSIONS

The prevalence of congenital or early acquired SNHI in the Kuopio University Hospital district area has not changed during a period of 29 years. Despite possibility to test the GBJ2 gene, the proportion of hearing impairment of unknown etiology remained high.

Universal newborn hearing screening: systematic review to update the 2001 US Preventive Services Task Force Recommendation

OBJECTIVE

This review is an update for the US Preventive Services Task Force on universal newborn hearing screening to detect moderate-to-severe permanent, bilateral congenital hearing loss. We focus on 3 key questions: (1) Among infants identified by universal screening who would not be identified by targeted screening, does initiating treatment before 6 months of age improve language and communication outcomes? (2) Compared with targeted screening, does universal screening increase the chance that treatment will be initiated by 6 months of age for infants at average risk or for those at high risk? (3) What are the adverse effects of screening and early treatment?

METHODS

Medline and Cochrane databases were searched to identify articles published since the 2002 recommendation. Data from studies that met inclusion criteria were abstracted, and studies were rated for quality with predetermined criteria.

RESULTS

A good-quality retrospective study of children with hearing loss indicates that those who had early versus late confirmation and those who had undergone universal newborn screening versus none had better receptive language at 8 years of age but not better expressive language or speech. A good-quality nonrandomized trial of a large birth cohort indicates that infants identified with hearing loss through universal newborn screening have earlier referral, diagnosis, and treatment than those not screened. These findings are corroborated by multiple descriptive studies of ages of referral, diagnosis, and treatment. Usual parental reactions to an initial nonpass on a hearing screen include worry, questioning, and distress that resolve for most parents. Cochlear implants have been associated with higher risks for bacterial meningitis in young children.

CONCLUSIONS

Children with hearing loss who had universal newborn hearing screening have better language outcomes at school age than those not screened. Infants identified with hearing loss through universal screening have significantly earlier referral, diagnosis, and treatment than those identified in other ways.

Estudo retrospectivo de crianças e jovens com deficiência auditiva: caracterização das etiologias e quadro audiológico

OBJETIVO: conhecer os fatores de risco para deficiência auditiva e obter informações sobre o tempo transcorrido entre suspeita, diagnóstico e intervenção em crianças e jovens deficientes auditivos atendidos no Serviço de Audiologia Educacional, DERDIC-PUC-SP. MÉTODOS: estudo retrospectivo de 162 prontuários de deficientes auditivos com idade entre um e 17 anos e 6 meses, atendidos de 1999 a 2002. Para registro dos dados utilizou-se a adaptação do protocolo elaborado no Fórum de Reabilitação Aural do Encontro Internacional de Audiologia, no Brasil. RESULTADOS: 54% dos sujeitos eram do sexo masculino e 46% do feminino; 60% tinham idade entre três e oito anos e 11 meses; 43% tiveram a suspeita da deficiência auditiva no primeiro ano de vida. Em 25% dos casos, o diagnóstico ocorreu logo após a suspeita, em 34% ocorreu um intervalo de até um ano; 11% iniciaram atendimento fonoaudiológico após diagnóstico, 54% demoraram até um ano e 27% demoraram mais de um ano. Trinta e dois por cento apresentaram etiologia desconhecida, 18% genética, 17% presumida multifatorial, 15% meningite, 9% rubéola congênita. CONCLUSÃO: a prevalência da etiologia desconhecida aponta para a necessidade do aprofundamento no diagnóstico etiopatológico (estudos genéticos, de imagens e laboratoriais) como rotina para se obter as causas da deficiência auditiva. Observou-se que mesmo após as campanhas de vacinação, a rubéola ainda foi a maior causa de deficiência auditiva congênita e a meningite a maior causa das deficiências auditivas adquiridas após o nascimento. Constatou-se um longo intervalo de tempo entre suspeita, confirmação e início da intervenção fonoaudiológica.

Birthweight and the risk of childhood sensorineural hearing loss

The aim of this study was to estimate the impact of birthweight on the risk of sensorineural hearing loss in children. The study was a nested case-control study. Cases (n = 327) were identified through the Norwegian county registers of children with hearing loss, and controls (n = 391 992) were all children without hearing loss born in the same counties, identified through the Norwegian Medical Birth Registry of Norway. Case definition was mean sensorineural hearing loss (MHL) > or =35 decibel (dB) hearing level (HL) in the better-hearing ear averaged over the pure-tone hearing thresholds at 500, 1000 and 2000 Hz, diagnosed before the age of 5 years. Birthweight <1500 g, as compared with 3500-3999 g, gave an adjusted odds ratio for sensorineural hearing loss of 6.3 [95% CI 2.4, 16.4], controlled for gestational age, gender, parity, maternal age and concurrent birth defects. The risk of hearing loss decreased with increasing birthweights, with adjusted odds ratios of 4.4, 3.8, 1.7 and 1.4 for the birthweights 1500-1999, 2000-2499, 2500-2999 and 3000-3499 g respectively. The risk of both mild to moderate (MHL 35-70 dBHL) and severe/profound hearing losses (MHL >70 dBHL) were influenced by birthweight.

Etiological diagnosis of bilateral, sensorineural hearing impairment in a pediatric Greek population

Early diagnosis, evaluation and treatment of childhood deafness are essential for a child's normal growth. Etiological diagnosis of hearing loss makes prevention, family scheduling and more effective therapy feasible goals. Etiological assessment of sensorineural deafness still remains difficult although recently with the progress of genetics it has become more efficient. In this retrospective study, the etiology of bilateral, sensorineural hearing loss with indication for hearing aids has been studied in 153 hearing impaired children. Etiological diagnosis was based on family and patient record, physical, audiological and laboratory examinations. Among the 94 children who completed the diagnostic protocol etiological groups revealed the following distribution: non-hereditary acquired hearing impairment was present in 36 children (38%) and hereditary was present in 44 (47%) children. The etiology remained unknown in 14 (15%) children. Non-syndromic autosomal dominant type accounted for 13 (29% of hereditary hearing loss) children, non-syndromic autosomal recessive type for 21 (48%) children and syndromic deafness for 10 (23%) children. Modern diagnostic methods, such as genetic testing, help diminish the number of cases with hearing impairment of unknown etiology, for the benefit of children who receive early and appropriate medical, audiologic, genetic and educational counseling based on the etiology of their hearing loss.

A population-based study of the recurrence of developmental disabilities--Metropolitan Atlanta Developmental Disabilities Surveillance Program, 1991-94

Serious developmental disabilities (DD) are quite common and affect approximately 2% of all school-aged children. The impact of DDs with respect to the need for special education services, medical care and the demand on family members can be enormous. While this impact can be magnified for families with more than one child with a DD, little is known regarding the epidemiology of recurrence of DDs. When the cause of a DD is unknown, genetic counsellors rely on recurrence risk estimates which for DDs are over 10 years old. The objectives of our study were to: (1) assess the contribution of recurrent cases to the prevalence of DDs; (2) provide current, population-based recurrence risk estimates; and (3) examine characteristics of the first affected child as predictors of recurrence. Two population-based data sources were used to identify all children born to the same mother during the period 1981-91 in the five-county metropolitan Atlanta area with at least one of four DDs: mental retardation (MR), cerebral palsy, hearing loss, or vision impairment. Recurrence risk estimates for these DDs ranged from 3% to 7% and were many times higher than the background prevalences. The risk of recurrence of DDs was greatest for MR - approximately eight times greater than the baseline MR prevalence. Isolated mild MR (IQ 50-70) was highly concordant between siblings with MR. Sex, race, and birthweight of the index child, maternal education, and maternal age were not significantly associated with recurrence risk. Further research is needed to investigate the roles of genetic and environmental factors on the recurrence of DDs, particularly isolated mild MR.

Syndromic etiology in children at schools for the deaf in Turkey

OBJECTIVE

The aim of this study was to determine the syndromic etiology of bilateral severe sensorineural hearing disorders in children and current etiological causes to reduce the cases in the unknown group.

METHODS

This study was conducted on 550 students of five schools for the deaf in Istanbul and Zonguldak, Turkey. Otologic, audiologic, dysmorphologic, ophthalmologic and dental examinations were performed in all children. Familial and medical histories were obtained.

RESULTS

The etiology of hearing loss was genetic in 346 (62.90%), acquired in 107 (19.45%) and unknown in 97 (%17.63) cases. A total of 619 malformations were defined in 550 children and 99 of them belonged to a syndrome. We identified 33 different syndromes for these 99 syndromic children. Syndromic etiology was found in 18.0% of the total and 28.61% of the subjects with genetic etiology. Most common syndrome was Waardenburg syndrome which occurred in 33 children.

CONCLUSION

The incidence of hereditary hearing impairment is very high in developing countries compared to developed countries. Prevention is essential to reduce the incidence, multidisciplinary approach and genetic counselling are necessary in this regard.

Sensorineural hearing loss in Jewish children born in Jerusalem

OBJECTIVE

Many factors, hereditary and environmental, may cause deafness. The aim of the present study was to analyze data on the etiology of bilateral sensorineural hearing impairment in children born in the Jerusalem area during 1978-1991, and to compare the results to those of a previous survey (1968-1977) in the same area.

METHODS

The study included 150 Jewish children (139 families) with hearing loss, born during 1978-1991. Information was obtained on prenatal, perinatal and postnatal events, history of hearing loss in the family, the parents' communities and consanguinity. Children with a sensorineural hearing impairment of 56 dB HL or greater in the better ear, within the frequency range of 0.5-4 kHz were included in the study. The hearing loss was classified as moderate-severe (56-70 dB HL), severe (71-90 dB HL) and profound (91 dB HL or more) in the better ear. Mutations in the coding sequence of the connexin 26 (C x 26) and the connexin 30 genes were examined in some of the families.

RESULTS

The hearing impairment was hereditary in 66 (44%) of the children, environmental in 31 (21%) and four children (3%) had multiple malformations. The cause was unknown in 49 (33%) children. Sixty-two families were of European origin (Ashkenazim) and 62 of Afro-Asian origin (Sephardim). Consanguinity was in 7% of the families. Mutations in connexin 26 and the deletion in connexin 30 were diagnosed in 9/18 families tested. The incidence of hearing loss decreased from 1.28 per thousand during 1968-1977 to 1.06 per thousand during 1978-1991. The rate of environmental causes decreased over the years together with an increase in the rate of unknown causes. The rate of hearing loss among Sephardim decreased significantly and increased among Ashkenazim.

CONCLUSIONS

The rate of hearing impairment in Israel is as that found in other countries, as was the distribution of the causes of deafness. The decrease in the rates of hearing impairment among the Sephardim may be due to a continuing decrease in consanguineous marriages among Sephardim. It is expected that the group of unknown causes will become smaller in future with the availability of more molecular genetic tests.

Systematic review of the etiology of bilateral sensorineural hearing loss in children

OBJECTIVE

Identification of the etiology of sensorineural hearing loss (SNHL) in children facilitates management and provides important prognostic information. In recent years, the etiology of bilateral SNHL in children has changed due to advances in genetic testing and treatment of perinatal infections. The objective of this study was to determine the frequency of etiologies of moderate-profound bilateral sensorineural hearing loss (SNHL) in children.

METHODS

The English literature was searched in Medline for articles published between 1966 and 2002. The inclusion criteria were studies involving bilateral SNHL >/=40dB in children less than 18 years of age. The studies were required to account for all patients, and provide a breakdown of etiologic factors. Etiologies investigated included genetic and non-genetic (prenatal, perinatal, postnatal). To compare differences between the frequencies of etiologies a two-sample t-test was performed assuming unequal variance. Studies were stratified according to perceived confounders: start date of study, study design, and degree of hearing loss.

RESULTS

Seven hundred and eighty abstracts were screened for relevancy. Forty-three studies satisfied the inclusion criteria. The common etiologies of bilateral SNHL were unknown (41.5%), genetic non-syndromic (27.2%), prenatal (11.5%), perinatal (9.7%), postnatal (6.6%), and genetic syndromic (3.5%). Unknown and Rubella were significantly less frequent etiologies in the more recent studies, while genetic non-syndromic, asphyxia and prematurity were more common. Genetic non-syndromic hearing loss was more frequent in the prospective studies compared to the population and retrospective studies, but this difference was not significant. Genetic non-syndromic hearing loss was more common among patients with profound hearing loss.

CONCLUSION

Accounting for the recent decline in infectious etiologies, the most common causes of bilateral SNHL are unknown (37.7%), genetic non-syndromic (29.2%), prenatal (12%), perinatal (9.6%), postnatal (8.2%), and genetic syndromic (3.2%).

Análise das principais etiologias de deficiência auditiva em Escola Especial "Anne Sullivan"

OBJETIVO: Determinar as principais etiologias de deficiência auditiva em estudantes da Escola de Ensino Especial para surdos "Anne Sullivan" em São Caetano do Sul e comparar com os dados da literatura mundial. FORMA DE ESTUDO: Estudo retrospectivo. MATERIAL E MÉTODO: Cento e trinta e um alunos da escola no ano de 2001 foram avaliados através de análise de seus prontuários, levando-se em conta dados de anamnese com a família, exame físico otorrinolaringológico, avaliação fonoaudiológica e psicológica. RESULTADOS: Dos 131 pacientes, 67 (51%) eram do sexo masculino e 64 (49%) do sexo feminino. A perda auditiva sensorioneural foi a mais encontrada, representando 99% dos casos. Quanto ao grau de disacusia, 65% foi classificado como profundo. Quanto à etiologia, 24% foi classificada como desconhecida e das causas identificáveis a rubéola congênita foi a mais encontrada (22%). Na maioria dos pacientes a suspeita e o diagnóstico foram feitos com 12 meses de idade. CONCLUSÕES: A etiologia não definida foi a mais representativa, seguida pela rubéola, e a idade de diagnóstico predominou entre 12 e 30 meses.

Screening and prevention of hearing loss in children

Congenital hearing loss is the most common neurosensory handicap in neonates. Recently, technology has become available that has allowed states to implement universal screening programs at a relatively low cost and with minimal expertise needed for hospital personnel to operate the screening machines. In successful programs, the age of diagnosis has been reduced from 2(1/2) years to 3 to 6 months. Children diagnosed with hearing loss before speech develops have been shown to have better speech and language outcomes than those who are diagnosed later. Strategies for screening and early intervention are discussed, as well as the causes, prevention, and treatment of more common forms of childhood hearing loss.

Newborn hearing screening in Western Australia

AIM

To report the preliminary findings of a pilot program to screen newborn babies for congenital bilateral permanent hearing loss.

SETTING

The five largest maternity hospitals in Perth, Western Australia. Screening was gradually introduced over seven months from February to August 2000.

PARTICIPANTS

All babies born at these hospitals after the introduction of hearing screening until 30 June 2001.

METHODS

One or both of two automated screening devices were used: one measuring transient evoked otoacoustic emissions (TEOAE) and the other automated auditory brainstem responses (AABR). If a "pass" was not obtained in both ears, screening was repeated. All babies who did not obtain a pass in either ear at follow-up were referred for audiological assessment.

MAIN OUTCOME MEASURES

Prevalence of permanent bilateral hearing loss.

RESULTS

Of 13 214 eligible babies, 12 708 (96.2%) received screening. The main reason for missing screening was early hospital discharge (309; 2.3%). Of the screened babies, 99% had a pass response in both ears at either the initial or follow-up screen. Twenty-three babies were referred for audiological assessment, and nine were diagnosed with bilateral permanent hearing loss (0.68/1000; 95% CI, 0.31-1.28).

CONCLUSIONS

Despite our program meeting process quality indicators, our detection rate was low. Before extending the program to smaller hospitals, we need to validate our screening instruments and put in place a system to monitor false negative results.

The need for universal neonatal hearing screening--some aspects of epidemiology and identification

The devastating consequences of a congenital/early-acquired hearing disability on the speech language and social development of a child and the estimated prevalence rates of at least 1-1.5/1000 live births of congenital permanent hearing impairment are important health problems. Universal neonatal hearing screening programs have provided the opportunity to detect neonates with permanent congenital hearing loss, and thus initiate auditory rehabilitation before the age of 3 mo. Universal neonatal hearing screening represents secondary prevention of hearing impairment/deafness, and the world-wide documented delayed identification of children with congenital/early-acquired hearing impairment will no doubt be improved with the implementation of universal neonatal hearing screening programs.

Clinical features of the prevalent form of childhood deafness, DFNB1, due to a connexin-26 gene defect: implications for genetic counselling

BACKGROUND

DFNB1, the locus of an autosomal recessive form of deafness due to mutations in the connexin-26 gene (CX26 or GJB2) is one of the most frequent hereditary defects in human beings. To date, no clinical characterisation of the DFNB1 inner-ear defects has been reported, which precludes the provision of prognostic information and genetic counselling.

METHODS

We enrolled, in a prospective study, 140 children from 104 families affected by sensorineural deafness with various degrees of hearing loss. The children either belonged to a family affected by autosomal recessive deafness (DFNB family) or represented sporadic cases. We searched for mutations in the 5' non-coding exon and in the coding region of CX26. Audiometric and radiological features were investigated and compared in deaf children with and without CX26 mutations.

FINDINGS

CX26 mutations were present in 43 (49%) of the 88 families with cases of prelingual deafness versus none of the 16 families with postlingual forms of deafness (p<0.01). The inner-ear defects of 54 prelingually deaf children with biallelic CX26 mutations were compared with the defects in 57 prelingually deaf children without CX26 mutations. DFNB1 deafness varied from mild to profound, associated with sloping or flat audiometric curves and a radiologically normal inner ear. Hearing loss was not progressive in 11 of 16 cases tested, and variations in the severity of deafness between siblings were common.

INTERPRETATION

The characteristic audiometric and radiological features of DFNB1 should be the reference used to guide the investigation, by CX26 molecular diagnostic tests, of deaf children with a compatible phenotype. Prognostic information can now be given to families: the hearing loss in DFNB1 deafness is non-progressive in most cases, at least up to young adulthood. An important element for genetic counselling is that the severity of hearing loss due to DFNB1 is extremely variable and cannot be predicted, even within families.

Prevalence and characteristics of children with serious hearing impairment in metropolitan Atlanta, 1991-1993

OBJECTIVES

There is a paucity of data describing the epidemiology of serious hearing impairment among children in the United States. This report provides information on the prevalence of serious hearing impairment among children born in the 1980s and living in the metropolitan Atlanta area in 1991-1993 and on the characteristics of children with serious hearing impairment.

METHODS

Data for this report are drawn from the Metropolitan Atlanta Developmental Disabilities Surveillance Program, an ongoing, active case-ascertainment system for mental retardation, cerebral palsy, hearing impairment, and vision impairment among children 3 to 10 years of age. Hearing impairment was defined as a bilateral, pure-tone hearing loss at frequencies of 500, 1000, and 2000 Hz averaging 40 decibels or more, unaided, in the better ear. Both severity and type of hearing loss were examined. Cross-sectional as well as birth cohort prevalence rates of serious hearing impairment were computed by sex and by race. The presence of mental retardation, cerebral palsy, vision impairment, or a seizure disorder was also assessed. An attempt was made to determine the probable etiology of a subset of the cases.

RESULTS

The average, annual prevalence rate for moderate to profound hearing loss was 1.1 per 1000. The prevalence rate increased steadily with age. Ninety percent of all cases for which the type of loss was recorded were sensorineural. The highest rate was seen among black male children (1.4 per 1000). Thirty percent of case children had another neurodevelopmental condition, most frequently mental retardation. Black male children also experienced the highest rate of presumed congenital hearing impairment. The mean age at which children with presumed congenital hearing impairment first met the surveillance case definition was 2. 9 years. A probable etiology could only be found for 22% of cases born in the study area.

CONCLUSIONS

The data presented here provide information on the descriptive epidemiology of serious hearing impairment among United States children. The reasons for the higher rates among black children, especially males, may be a fruitful direction for further research.

Prevalence and etiology of unilateral sensorineural hearing impairment in a Finnish childhood population

A retrospective study was undertaken on the prevalence and etiology of unilateral sensorineural hearing impairment (> 25 dB at 0.5-4 kHz, including mixed hearing impairments with bone conduction thresholds > or = 25 dB) among children born between 1972 and 1986 in a province of eastern Finland. Only patients who had been diagnosed before the age of 10 years were included. A total of 84 children with such an unilateral hearing loss were identified, with prevalence of 1.7 per 1000 live births. A significant decline from the prevalence of 2.2 per 1000 in the 1970s to the prevalence of 1.2 per 1000 in the 1980s was observed, which was mainly due to the disappearance of hearing losses caused by mumps and measles in the 1980s and the decrease in cases attributed to otitis media. In agreement with some previous studies, a considerable male predominance was present. Thirty-five percent of the hearing losses were profound (> 95 dB) and 15% were severe (71-95 dB). Etiology of the hearing impairment was estimated as genetic in 2%, congenital non-genetic in 12%, delayed-onset non-genetic in 35% and remained unknown in 51%.