Perinatal risk factors in the aetiology of hearing loss in preschool children

Gentamicin Exposure and Sensorineural Hearing Loss in Preterm Infants

Objective

To evaluate the impact of gentamicin exposure on sensorineural hearing loss (SNHL) in very low birth weight (VLBW) infants.

Methods

Exposure to gentamicin was determined in infants born between 1993 and 2010 at a gestational age < 32 weeks and/or with a birthweight < 1500 g, who presented with SNHL during the first 5 years of life. For each case, we selected two controls matched for gender, gestational age, birthweight, and year of birth.

Results

We identified 25 infants affected by SNHL, leading to an incidence of SNHL of 1.58% in our population of VLBW infants. The proportion of infants treated with gentamicin was 76% in the study group and 70% in controls (p = 0.78). The total cumulated dose of gentamicin administered did not differ between the study group (median 10.2 mg/kg, Q1-Q3 1.6–13.2) and the control group (median 7.9 mg/kg, Q1-Q3 0–12.8, p = 0.47). The median duration of gentamicin treatment was 3 days both in the study group and the control group (p = 0.58). Maximum predicted trough serum levels of gentamicin, cumulative area under the curve and gentamicin clearance were not different between cases and controls.

Conclusion

The impact of gentamicin on SNHL can be minimized with treatments of short duration, monitoring of blood levels and dose adjustment.

Sensorineural hearing loss in children: the association with Apgar score. A registry-based study of 392,371 children in Norway

OBJECTIVES

The causes of congenital permanent hearing loss in children are insufficiently understood. We studied the association of Apgar score 5 min after birth with sensorineural hearing loss diagnosed before the age of 5 years.

METHODS

We performed an epidemiological cohort study with data obtained by linkage between The Medical Birth Registry of Norway and the Norwegian County Registry of Children with Hearing Loss. Cases were 327 children born in Norway during the period 1978-1998 with sensorineural hearing loss. Controls were all children in Norway without sensorineural hearing loss born in the same counties and during the same period as the cases (n=392,044). The associations of Apgar score 5 min after birth with sensorineural hearing loss were estimated as odds ratios (OR) with 95% confidence intervals (CI) by applying logistic regression analyses.

RESULTS

Among children with sensorineural hearing loss 0.9% (3/327) had Apgar score<3, whereas that was true for 0.1% (304/392044) of children without hearing loss (p=0.001, chi square test). The aOR for sensorineural hearing loss was 7.5 [95% CI 2.3-, 24.2] comparing Apgar score<3 to Apgar score 10, after adjustment for birthweight and concurrent birth defects. Most children with sensorineural hearing loss (90%) had Apgar score>8 five minutes after birth.

CONCLUSIONS

Low Apgar score was associated with childhood sensorineural hearing loss. However, most children with sensorineural hearing loss, had Apgar score>8.

Attitudes of the UK ear, nose and throat clinical community to the future potential use of stem cell therapies to treat deafness

AIMS

Hearing loss is commonly due to the degeneration and death of hair cells and their associated spiral ganglion neurons. A total of 250 million people are affected worldwide. Stem cell treatments offer new and powerful strategies to enable recovery from hearing loss. This study focuses on the translational process required to move stem cell therapy from the laboratory to clinical use as a novel treatment of deafness and an alternative to conventional therapy. In particular, this study aims to inform and enable the adoption process for such therapies, including understanding the awareness of and attitudes towards stem cell therapy for hearing loss among ear, nose and throat surgeons, physicians, audiologists and scientists, who are key stakeholders in the adoption process.

METHODS

A structured questionnaire has been developed and applied to assess the knowledge and awareness of the clinical community with respect to the future potential use of stem cell therapies to treat deafness.

RESULTS

Results showed >87% of the clinicians sampled have very little or no knowledge of stem cell therapy. A total of 11% have been asked by patients about the use of stem cell therapies to treat deafness, and 64% felt a new treatment is needed for deafness. Significantly, 40% felt that a stem cell therapy would be a good adjuvant to a cochlear implant. In total, 78% were supportive of investment in stem cell therapy research and manufacturing. This investment should be in work directed at those areas where clinicians favor adoption.

CONCLUSION

Alignment is required between the scientific and clinical communities. This should not only take into account the likelihood of scientific success when pursuing the therapeutic alternatives, but should also consider the clinical trial requirements, regulatory landscape and reimbursement conditions for each option.

Maternal and neonatal factors associated with mode of delivery under a universal newborn hearing screening programme in Lagos, Nigeria

Background

Emerging evidence from a recent pilot universal newborn hearing screening (UNHS) programme suggests that the burden of obstetric complications associated with mode of delivery is not limited to maternal and perinatal mortality but may also include outcomes that undermine optimal early childhood development of the surviving newborns. However, the potential pathways for this association have not been reported particularly in the context of a resource-poor setting. This study therefore set out to establish the pattern of delivery and the associated neonatal outcomes under a UNHS programme.

Methods

A cross-sectional study in which all consenting mothers who delivered in an inner-city tertiary maternity hospital in Lagos, Nigeria from May 2005 to December 2007 were enrolled during the UNHS programme. Socio-demographic, obstetric and neonatal factors independently associated with vaginal, elective and emergency caesarean deliveries were determined using multinomial logistic regression analyses.

Results

Of the 4615 mothers enrolled, 2584 (56.0%) deliveries were vaginal, 1590 (34.4%) emergency caesarean and 441 (9.6%) elective caesarean section. Maternal age, parity, social class and all obstetric factors including lack of antenatal care, maternal HIV and multiple gestations were associated with increased risk of emergency caesarean delivery compared with vaginal delivery. Only parity, lack of antenatal care and prolonged/obstructed labour were associated with increased risk of emergency compared with elective caesarean delivery. Infants delivered by vaginal method or by emergency caesarean section were more likely to be associated with the risk of sensorineural hearing loss but less likely to be associated with hyperbilirubinaemia compared with infants delivered by elective caesarean section. Emergency caesarean delivery was also associated with male gender, low five-minute Apgar scores and admission into special care baby unit compared with vaginal or elective caesarean delivery.

Conclusions

The vast majority of caesarean delivery in this population occur as emergencies and are associated with socio-demographic factors as well as several obstetric complications. Mode of delivery is also associated with the risk of sensorineural hearing loss and other adverse birth outcomes that lie on the causal pathways for potential developmental deficits.

Children with chronic non-progressive encephalopathy: hearing evaluation and hearing aids

AIM

to assess the auditory abilities of children with non-progressive chronic encephalopathy (NPCE), independently of the presence or not of hearing loss, and of the etiology of the encephalopathy; to characterize the benefit of hearing aids in children with NPCE and hearing loss.

METHOD

neurologic, otorhinolaryngologic and auditory assessments. Application of the Parent's Evaluation of Aural/Oral Performance of Children (PEACH) protocol.

RESULTS

out of the 46 assessed children, 22 (48%) presented no hearing loss and 24 (52%) presented some level of sensorineural hearing loss. Regarding the encephalopathy etiology, most of the participants presented ischemic hypoxic encephalopathy followed by infectious process and kernicterus. The results also indicate that 16 (35%) parents suspected that their child had hearing loss; out of this total, 56% had the hearing loss confirmed. Thirty parents (65%) did not have any hearing complaints about their children. For these children the auditory evaluation indicated that 50% presented some level of hearing loss. The PEACH protocol proved to be effective to assess the benefit of hearing aids.

CONCLUSION

the results indicate that over half of participants presented hearing loss. No correlation was observed between etiology and complaints of hearing loss. This means that it is not possible to predict hearing loss based on complaints. All children who presented hearing loss benefited from the use of hearing aids.

Iatrogenic environmental hazards in the neonatal intensive care unit

Premature infants in the neonatal intensive care unit (NICU) face many illnesses and complications. Another potential source of iatrogenic disease is the NICU environment. Research in this area, however, is limited.

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.

Comparative evaluation of Transient Evoked Oto-acoustic Emissions and Brainstem Evoked Response Audiometry as screening modality for hearing impairment in neonates

OBJECTIVE

This study was designed to evaluate Transient Evoked Oto-acoustic Emission (TEOAE) as screening modality for hearing impairment in neonates. Brainstem Evoked Response Auditometry (BERA) was used as gold standard diagnostic tool in this study. The factors affecting the specificity of TEOAE were also studied.

METHODS

The study group of 200 randomly selected neonates was subjected to TEOAE and BERA (400 ears). Oto-endoscopy was done in all TEOAE failures and a repeat test was done after suction cleaning of blocked external auditory canal (EAC).

RESULTS

Otoscopic evaluation of all 52 TEOAE failures was done. EAC obstruction was noticed in 31 ears and 4 ears showed collapsible EAC. TEOAE was repeated after suction cleaning of the obstructed EAC and using long probe tips for collapsible EAC. This improved the Pass rate of TEOAE from 87% to 92%. EAC obstruction and collapsible EAC were the two factors identified in this study that significantly affected the specificity of TEOAE as a screening test. Pass rate of TEOAE in <48 hrs age group was found to be 55.5%, which was nearly half of over-all pass rate. This was because of high prevalence of obstructed EAC in this age group. TEOAE was found to be a rapid screening tool as average time taken for BERA was 35 min/neonate and for TEOAE was 17.4 min/neonate. Acceptability of TEOAE was found to be higher as compared to BERA.

CONCLUSIONS

TEOAE is a simple and rapid test with relatively higher acceptability. But, the low sensitivity and specificity are the main shortcomings that take away from TEOAE, the status of independent screening modality for hearing impairment in neonates. TEOAE cannot completely replace BERA as screening modality for hearing impairment in neonates, however can complement it.

Teenage outcome after being born at term with moderate neonatal encephalopathy

The aim of this study was to assess cognitive functions and behavior problems in teenagers who survived moderate neonatal encephalopathy and did not develop cerebral palsy. The study population comprised all 97,468 individuals born in Sweden in 1985. Of these, 684 (0.7%) were born at term and had an Apgar score of <7 at 5 minutes. The obstetric and neonatal records were scrutinized and the individuals were classified according to degree of neonatal encephalopathy. Teenagers with moderate neonatal encephalopathy without cerebral palsy and other major neuro-impairments were subjected to a clinical assessment including interviews, neuropsychological tests, and assessments of data from records. Age at examination was 15-19 years. Fifty-six individuals who had moderate neonatal encephalopathy were identified. Thirteen (23%) had parents who declined participation in the study. Of the remaining 43 subjects, 15 (30%) had a diagnosis of cerebral palsy or other major neuro-impairments and 28 had no such impairments. The latter group was examined, 20 of whom (71%) had definite cognitive dysfunctions. Five (18%) had hearing impairments. Only eight teenagers were without impairments. Of those who did not have cerebral palsy, the majority had cognitive/executive problems that interfered with their daily life situation. Clinical follow-up, including assessments of cognitive functions before school start, should be considered for all individuals in this high-risk group.

The association between short stature and sensorineural hearing loss

In order to test the Thrifty Phenotype Hypothesis on hearing, data from two cross-sectional studies on hearing were re-evaluated. The data sets comprised 500 18-year-old conscripts, and 483 noise-exposed male employees. Sensorineural hearing loss (SNHL) was over-represented among conscripts with a short stature (odds ratio=2.2) or hearing loss in the family (odds ration=4.2), but not among noise-exposed conscripts (odds ratio=0.9-1.3). Among noise-exposed short employees, hypertension and age exhibited a negative impact on high frequency hearing thresholds, while among tall employees hypertension had no effect on hearing and the influence of age was less pronounced (p<0.01 for body height; p<0.02 for age, hypertension and the interaction between body height and hypertension; p<0.05 for the interaction between body height and age). This suggests that mechanisms linked to fetal programming and growth retardation and/or insulin-like growth factor 1 levels during fetal life, such as a delayed cell cycle during the time window when the cochlea develops, may cause SNHL in adulthood.

Stem cells as therapy for hearing loss

One of the greatest challenges in the treatment of inner-ear disorders is to find a cure for the hearing loss that is caused by the loss of cochlear hair cells or spiral ganglion neurons. The recent discovery of stem cells in the adult inner ear that are capable of differentiating into hair cells, as well as the finding that embryonic stem cells can be converted into hair cells, raise hope for the future development of stem-cell-based treatment regimens. Here, we propose different approaches for using stem cells to regenerate the damaged inner ear and we describe the potential obstacles that translational approaches must overcome for the development of stem-cell-based cell-replacement therapies for the damaged inner ear.

[Hypoacusis-deafness related to perinatal adverse conditions. According to the register available in a specialized unit of Ciudad de Mexico. Analysis according to birth weight]

OBJECTIVE

To analyse perinatal adverse conditions related with birth weight in 160 children with hearing impairment-deafness (prelingual sensorineural hearing loss) according to medical data of a specialized medical unit in Mexico City.

RESULTS

The average age of children was 4 years old +/- 1.7; 61% were male. 47.5% of the cases had a birthweight between 1,500 and 2,900 g. 90 cases (56%) had an abnormal delivery and 68 (42.5%) were first pregnancy cases. A high number of cases had delayed breathing, cyanosis, jaundice or respiratory failure. 104 cases (65%) had deafness and 56 (35%) presented. hearing loss. Only 11% of the children had a birth-weight under 1,500 g. 58% of all cases had a birth weight lower than 3,000 g.

CONCLUSION

The quality of medical assistance provided during the perinatal period has a very important role in origin of hearing impairment--deafness in this group of children. It is important to increase our knowledge about the perinatal adverse conditions in order to establish preventive programs.

Adverse perinatal conditions and the inner ear

Epidemiological studies in a number of Western countries have attributed 6-14% of sensorineural hearing impairment from birth or early childhood to problems relating to the birth process [1-4]. In spite of this association it is not always clear in individual instances whether adverse perinatal conditions identified subsequently have been causative of a hearing loss or not. It is possible that the hearing impairment was the consequence of an earlier intrauterine insult or is a coincidental finding. Infants carrying genetic mutations for hearing loss may coincidentally experience perinatal stress. It is therefore important to investigate the cause of a hearing loss discovered in infancy irrespective of the history of the infant having experienced adverse conditions surrounding the time of birth.

Histopathology and molecular genetics of hearing loss in the human

Hearing loss is among the most common disabilities of man. It has been estimated that over 70 million individuals in the world are hearing impaired with pure tone averages greater than 55 dB. A genetic etiology is thought to be responsible for over half of early onset hearing loss and at least one third of late onset hearing loss. In this review, examples of the histopathology of the inner ear in known genetic syndromes in the human will be presented in order to provide a structural basis for understanding molecular mechanisms of development and maintenance in the inner ear, and to serve the essential function of validating the applicability of animal genetic models of hearing loss to the human condition.

Neonatal asphyxia, definitive markers and hearing loss

A study of 56 severely asphyxiated infants (8 hearing impaired and 46 normally hearing) was designed to identify specific markers associated with asphyxia which could be related to hearing loss. Sixteen variables, including such items as: one- and five-minute Apgar scores, muscle tone, use of a ventilator, prolonged stay in the NICU, hypoxic-ischemic encephalopathy (HIE), other organ damage, and intra-uterine growth retardation (IUGR) were considered. Results suggested four factors related to asphyxia which are often found in the presence of hearing loss, but none of these was considered a definitive marker or predictor of such a disability. A combination of HIE, seizures, associated organ damage and IUGR should be considered a strong marker for the probability of a sensorineural hearing loss.

Relative and attributable risks for moderate to profound bilateral sensorineural hearing impairment associated with lower birth weight in children 3 to 10 years old

OBJECTIVE

To determine the prevalence, relative risks, and attributable fractions for congenital bilateral sensorineural hearing impairment in relation to lower birth weight among children born in the 1980s and living in the metropolitan Atlanta area from 1991 through 1993.

METHODS

We used the population-based, active case ascertainment Metropolitan Atlanta Developmental Disabilities Surveillance Program that conducts surveillance in the five-county metropolitan Atlanta area. Hearing impairment was defined as a bilateral, pure-tone hearing loss at frequencies of 500, 1000, and 2000 Hz averaging 40 dBs or more, unaided, in the better ear. Case children, 3 to 10 years of age, with sensorineural loss of presumed congenital origin were included in these analyses (n = 172). Prevalence rates and relative risks were computed for various birth weight categories by hearing level, sex, race, the presence or absence of coexisting developmental disabilities, and gestational age. Attributable fractions were calculated for low birth weight and very low birth weight children by race.

RESULTS

The overall prevalence rate of presumed congenital bilateral sensorineural hearing impairment was 5.3 cases per 10 000 3-year survivors. The prevalence was 4.1 per 10 000 among children weighing >/=4000 g, 3.7 per 10 000 among those weighing 3000 to 3999 g, 6.6 per 10 000 among those 2500 to 2999 g, 12.7 per 10 000 among those 1500 to 2499 g, and 51.0 per 10 000 among those <1500 g. There was virtually no difference in birth weight-specific rates of hearing impairment across three hearing levels. The presence of coexisting developmental disabilities was associated with a much stronger inverse trend with birth weight. Black children weighing <2500 g had much higher rates of hearing impairment than comparable white children. The overall percentage of moderate to profound congenital bilateral sensorineural hearing loss in the entire study population that was attributable to children weighing <2500 g or <1500 g was estimated to be 18.9% and 9.4%, respectively. Prematurity did not alter the magnitude of risk among children weighing <2500 g.

CONCLUSIONS

The results presented here provide recent estimates of the rates, relative risks, and attributable fractions for congenital bilateral sensorineural hearing impairment by birth weight among children in the United States. The elevated relative risks among children weighing 2500 to 2999 g and 1500 to 2499 g may have implications for future newborn hearing screening criteria.

Auditory screening in neonates by means of transient evoked otoacoustic emissions: a report of 2,842 recordings

The principal goal of an early identification program is to identify hearing impairment present at birth, in order to effect appropriate intervention as early as possible. Although recent research provides some evidence for the value of transient evoked otoacoustic emissions (TEOAEs) in neonate hearing screening, data are needed from large-scale clinical evaluations about the value of using TEOAEs for screening not only high-risk but also healthy neonates. A cohort of 1,421 neonates (2,842 ears) from the well-baby nursery was screened with TEOAEs in a 2-stage process. Neonates were referred from the first test prior to being discharged from the hospital. Those who failed were rescreened before the end of the first month. Those who did not pass the second-stage TEOAE screening were referred for diagnostic audiological evaluation for confirmation of hearing loss. Neonates transferred to a neonatal intensive care unit were not included in this study. Two neonates with bilateral sensorineural hearing loss of >40 dB hearing level were identified from this cohort. This study demonstrates the feasibility and the limitations of using TEOAEs as a universal hearing screening tool for all neonates. It confirms that the prevalence of hearing impairment in neonates has to be taken into account, even in a group of children without high-risk criteria. In France, a prevalence of 1.4 per 1,000 would represent 1,000 deaf children born every year, with reference to about 700,000 births per year. This study suggests that such universal screening programs would substantially increase the rate of early-identified infants with significant hearing impairment.

Aetiology and risk indicators of hearing impairments in a one-year birth cohort for 1985-86 in northern Finland

The aetiology and risk indicators of hearing impairments of all types and degrees were studied in a 1-year birth cohort of 8713 children from northern Finland. The subjects (7 years of age) included in the clinical and audiometric examinations were recruited by standard clinical criteria, i.e. suspicion of parents according to a questionnaire, abnormal hearing screening result or a hearing impairment noted in hospital records (n = 541), and by random sampling from among the 8172 not suspected (n = 1009). One-hundred-and-one subjects in the group suspected of having hearing impairment and 27 subjects in the random sample eventually had hearing impairment. The aetiology could be defined in only 44.5% of the cases, ear infections being the most common. In this relatively small series, only a few risk indicators (congenital anomalies, meningitis and a history of ear discharge lasting for over 1 month) could be shown to be associated with impaired hearing in a logistic regression analysis.

Epidemiology of moderate to profound childhood hearing impairments in northern Finland. Any changes in ten years?

The epidemiology of childhood hearing impairments was studied in a clinical series of the birth cohorts for 1973-82 and 1983-92 from a geographically well-defined area. The overall prevalence of hearing impairments with PTA0.5-4 kHz > or = 40 dB was 1.2/1000 live births. Even in the later cohort, the median age ascertainment was 2.6 years for the congenital or early acquired group and 3.0 years for all impairments. Risk indicators for hearing impairment were present in half of the children, and those referred for the risk were ascertained at the median age of 1.1 years. The delay from suspicion to ascertainment was over a year in about one fifth of cases, while the median time from referral to ascertainment was only 1.8 months. The planning and implementation of neonatal hearing screening are suggested, and general information is given on paedoaudiology for both parents and professionals. A database could be beneficial in increasing the systemacy of the diagnostic process.

Changes in prevalence, aetiology, age at detection, and associated disabilities in preschool children with hearing impairment born in Göteborg

The prevalence of hearing impairment (HI) in preschool children born in Göteborg in 1980 to 1984 was 2.0 per 1000. This was significantly lower than the 3.8 per 1000 found in a previous study for 1970 to 1974. The decrease took place in the moderate to severe range of HI, while deafness and mild HI remained unchanged during the period. The cause was considered to be prenatal in 58% with heredity in 33% as the main causative factor. Following the introduction of the MPR (Morbilli-Parotitis-Rubella) vaccination programme in Sweden, no cases of rubella- or mumps-induced HI could be found. The number of HI of perinatal origin decreased by half, in spite of the fact that the figures for preterm baby survival almost doubled during the period. Associated disabilities were diagnosed in 62% of the children with HI; speech retardation in 33%, visual abnormalities in 30%, mental retardation in 12% and neuropsychiatric disorders in 9% of the cases. The importance of collaborative efforts between the otolaryngologist and the neurologically and neuropsychiatrically interested paediatrician in the complete evaluation of additional difficulties in the HI child is emphasized.

Hearing, speech, language, and vestibular disorders in the fetal alcohol syndrome: a literature review

Fetal alcohol syndrome (FAS) is characterized in part by mental impairment, as well as craniofacial and ocular anomalies. These conditions are traditionally associated with childhood hearing disorders, because they all have a common embryonic origin in malformations of the first and second branchial arches, and have similar critical periods of vulnerability to toxic insult. A review of human and animal research indicates that there are four types of hearing disorders associated with FAS. These are: (1) a developmental delay in auditory maturation, (2) sensorineural hearing loss, (3) intermittent conductive hearing loss due to recurrent serous otitis media, and (4) central hearing loss. The auditory and vestibular systems share the same peripheral apparatuses (the inner ear and eighth cranial nerve) and are embryologically and structurally similar. Consequently, vestibular disorders in FAS children might be expected. The evidence for vestibular dysfunction in FAS is ambiguous, however. Like other syndromes associated with craniofacial anomalies, hearing disorders, and mental impairment, FAS is also characterized by a high prevalence of speech and language pathology. Hearing disorders are a form of sensory deprivation. If present during early childhood, they can result in permanent hearing, language, and mental impairment. Early identification and intervention to treat hearing, language, and speech disorders could therefore result in improved outcome for the FAS child. Specific recommendations are made for intervention and future research.

Alcohol, auditory functioning and deafness

This paper reviews studies of alcohol and auditory impairment and the treatment of deaf people with alcohol problems and concludes that: (a) alcohol affects auditory functioning, (b) prenatal exposure to alcohol is a risk factor for hearing impairment in FAS children,

Preauricular tags and pits in the newborn: the role of hearing tests

The aim of this study was to determine the role of audiometry in a group of newborn infants with preauricular tags or pits. During the 2 years of prospective study, 26 infants were born with preauricular tags or pits (5.7 per 1,000 livebirths) and were assessed for hearing impairment by performing behavioural audiometry on day 3 of life and brainstem-evoked response audiometry at 4 months of age. Five infants had associated congenital anomalies (19%). The behavioural audiometry was abnormal in seven infants (27%). The evoked response audiometry was abnormal in 4/23 (17%) newborn infants with isolated tags or pits, and revealed both conductive and/or sensorineural hearing impairment. The incidence of hearing impairment with isolated preauricular tag/pit was significantly higher (p < 0.001) than the incidence reported in preschool children. We conclude that hearing assessment is recommended in the routine evaluation of the newborn with isolated preauricular tags or pits. This policy may facilitate early diagnosis and treatment of hearing impairment in this population.

Risk factors for childhood sensorineural hearing loss in the Oxford region

We have used a comprehensive register of hearing-impaired children born in the former Oxford Health Region to study risk factors for sensorineural hearing loss. The occurrence of a wide variety of risk factors was documented from the case notes of 145 children; these were all the cases known at the time of the study with all degrees of hearing loss born between 1984 and 1988. Comparison with the normal Regional population showed that maternal age over 35 years and Asian ethnic origin were significant risk factors for congenital (non-acquired) hearing loss (odds ratio 1.7 and 2.5 respectively). Black/Asian children were also significantly more likely to have acquired losses. Low birthweight (below 2500 g) also gave a significantly increased risk, with an odds ratio of 4.5, rising to 9.6 for birthweight less than 1500 g. We also found that significantly more hearing-impaired cases were in lower social classes compared with the general population. A high proportion of cases (24%) had cranio-facial abnormalities (CFA), including many non-aural abnormalities and dysmorphic features, which therefore should be counted as high risk. Hearing losses acquired due to perinatal causes were almost all mild or moderate. Four factors-admission to special care baby unit for more than 72 hours, CFA, family history, and meningitis-accounted for 69% of all cases in this study. Targeted neonatal screening based on the first three factors, plus obligatory testing following meningitis, therefore, should be highly efficient at detecting deafness early.

Perinatal asphyxia, hypoxia, ischemia and hearing loss. An overview

Birth hypoxia, asphyxia and ischemia have often been thought to be major causes of early hearing loss or deafness. The purpose of the present review is to focus on the role of these particular factors for perinatal auditory disorders. On the whole, only a small proportion of neonatal hearing loss is caused by perinatal factors. The exact etiology of neonatal hearing loss in children with complicated deliveries is difficult to evaluate due to the large number of causative factors that might be involved. After reviewing the literature covering the past 15-20 years, it is not possible to say that we understand the relative importance of different factors and their interactions. However, in the majority of studies, birth asphyxia is not correlated with hearing loss in babies with complicated deliveries Prolonged artificial ventilation, the presence of severe hypoxic ischemic encephalopathy or persistent pulmonary hypertension are important factors. The brain is more susceptible to anoxia than the ear and both are more likely to be damaged after prolonged pre-, peri- and postnatal hypoxia-ischemia than pure hypoxia during delivery. Perinatal hypoxia is more likely to cause a temporary hearing loss than a permanent one. Preterm babies are more vulnerable than term babies. The total number of risk factors, e.g. medicated by total length of stay in the neonatal intensive care unit and length of artificial ventilation, is the best predictor of risk for hearing loss of perinatal origin. The similarities between hearing loss and cerebral palsy are pointed out; only 8% of the cases of cerebral palsy are considered to be caused by conditions during delivery.

Prevalence of sensorineural hearing loss in Asian children

The study was designed to assess whether Asian children were at an increased risk of having sensorineural hearing loss. All the Asian children aged between 5 and 16 years were identified from class lists to form the study group, and an equal number of non-Asian children, controlling for age and sex, were randomly selected from the Child Health records to form the control group. With parent's consent, a four frequency (1, 2, 4 and 8 kHz) pure tone screening test was carried out on the children in both groups. There was a second screen for the failures and a diagnostic assessment for those failing again. Prevalence rate was calculated for two categories of hearing impairment (mild-to-profound and moderate-to-profound) and for the better and worse ear, resulting in four prevalence estimates for each group. The absolute prevalence rates for the Asian children were all consistently higher (ranging from 5.09 to 9.61 per 1000) than the non-Asian children (ranging from 1.4 to 3.51 per 1000) and the relative risk measure showed the Asian group to be 2.42-3.61 times at greater risk of having a hearing loss. The results of this study were compared with other studies and inconsistencies were discussed with reference to methodological differences and deficiencies. It was concluded that Asian children were at an increased risk of sensorineural hearing loss.

Prevalence, aetiology, and care of severe and profound hearing loss

Severe and profound hearing loss (> 70 dB) were analysed in a retrospective study of 226 children, born between 1976 and 1985, and recruited from three French administrative departments. The prevalence was 0.54 per 1000 children under 9 years old, with no decrease over the study period. A hereditary origin was identified in 20.8% of cases and an infectious origin in 11.5%. Perinatal risk factors were present in 11.5%, while the aetiology was undetermined in more than half the cases. In 85.8% of the children there was no other severe impairment. Marked learning difficulties were observed: 36% of the children were two years behind their age group and 28% were more than two years behind. The age of initial care decreased over the study period but is still too advanced. Systematic neonatal screening would enable earlier care, which should limit the social and educational impact of hearing loss.

Hearing loss at the age of 5 years of children born preterm--a matter of definition

The effect of three common hearing impairment criteria on the prevalence of hearing loss was evaluated in 58 prospectively followed-up 5-year-old children born preterm at < or = 32 weeks of gestation. Audiological assessment was done as part of an extensive neurodevelopmental evaluation at the age of 5 years. With the criterion based on the classification of the World Health Organization (average threshold hearing level > 25 dB at frequencies of 0.5, 1 and 2 kHz, classified according to the less impaired side) there were two preterm children with mild hearing impairment. With Clark's criterion (unilateral average threshold hearing level > 15 dB at frequencies of 0.5, 1 and 2 kHz) eight children had slight hearing impairment; seven of these had conductive hearing problems. With the criterion of a single frequency-specific deficit > 15 dB for 0.25-4 kHz the number of hearing-impaired children was 28 out of 54 (51.9%), most of whom had conductive or unspecified hearing deficits. Moreover, of the four multiply handicapped, retarded children whose pure tone thresholds were not assessed monaurally, three would belong to the hearing-impaired group according to Clark's criterion and four according to the frequency-specific criterion.

[Deafness in the neonatal period: basis for screening]

Deafness must be recognized in infancy in order to reduce auditory disability to a minimum. To achieve this, it is important to implement screening programmes as soon after birth as possible. In the United States, the Joint Committee on Infant Hearing recommended in 1982 that identification of hearing loss should be screened in the neonatal period. This early detection is now considered critical for optimal rehabilitative outcome. This paper presents the "state of art" neonatal screening principles and procedures. In France, neonatal screening programs for auditory dysfunction are not consistent with these principles. Evoked otoacoustic emissions represent an important advance in screening for hearing loss in normal neonates and babies from neonatal intensive care units. This method records very low intensity sound energy released by the cochlea in response to a brief sound stimulation. These otoacoustic emissions show promise as a rapid, cost-effective means of quickly discharging all babies with normal peripherical auditory systems.

A survey of ear and hearing disorders amongst a representative sample of grade 1 schoolchildren in Swaziland

A representative sample of Grade 1 (first year school entry) schoolchildren in Swaziland were surveyed during a single week to determine the prevalence of ear and hearing disorders: 79.8% had both normal ears and normal hearing, 16.8% had an ear disorder, but 80% of them had normal hearing. The most common disorder was impacted wax, with a prevalence rate of 74/1000. Middle ear disorders were common and the prevalence rate for children with active middle ear disease was 30/1000 (17/1000 having a hearing loss), and for children with inactive ear disease, the prevalence was 21/1000 (5/1000 having a hearing loss); 8/1000 children were found to have a sensorineural hearing loss, 5.3/1000 unilateral and 2.1/1000 bilateral. Improved treatment of acute otitis media, which is also common in the pre-school age group, could reduce the sequelae of the disorder, which has a deleterious effect on hearing and impairs educational achievement once the children enrol at school.

Screening and assessment of childhood deafness: experience from a centralized multi-disciplinary service

A paediatric hearing assessment unit was set up in Lothian in 1978 to provide a clear referral pathway for children with suspected sensorineural hearing impairment and particularly for those children detected by the health visitor screening test. Over a 6-year-period the incidence of bilateral sensorineural deafness was 1.3/1000 suggesting that all children in the region were being seen. The mean age of diagnosis fell significantly over this period. Children in high risk groups, through adverse perinatal events or a positive family history, were not detected any earlier than other children. They were therefore not contributing to this improved earlier age of diagnosis. These findings support the continuation of health visitor screening but changes in practice are needed to encourage earlier diagnosis in high-risk groups.

Screening for sensorineural deafness by health visitors. The Steering Committee, Oxford Region Child Development Project

Screening for hearing loss in the first year of life, using the distraction test, remains the responsibility of health visitors in most health districts in the United Kingdom. We have evaluated the screening procedure used routinely in one health region in a population of infants at increased risk of sensorineural deafness. They were infants who weighed less than 2000 g at birth or infants who weighed 2000 g or more at birth and who spent more than 24 hours in a special care nursery. The infants' responses to a distraction test were recorded by health visitors and sent to the project office. The results were compared with information from a regional register of early childhood impairment that included children in whom sensorineural deafness had been diagnosed before the age of 3 years. The register had been compiled using information from a wide range of sources. When used in this high risk population the distraction test was sensitive (91%), but nonspecific (82%). The effectiveness of the screening programme was limited, however, because there was an increased risk of deafness among infants who missed being screened by health visitors. In addition, 71% of the deaf infants on the register were not in the high risk population.

Epidemiologic patterns in childhood hearing loss: a review

In an attempt to clarify international epidemiologic trends, a review of the published literature pertaining to childhood hearing loss is presented. Inconsistencies of methodology and classification, which complicate the interpretation of data and make difficult the quantification of the influence of genuine population differences, are discussed. Selective review of the literature allows certain crude statements to be made regarding childhood hearing loss. In developed countries, serous otitis media is the most common cause of hearing loss in children, affecting up to two thirds of preschool children. In addition, 1.0-2.0/1000 children have bilateral SNHL of at least 50 dB. In underdeveloped countries, suppurative middle ear disease is common and is still frequently associated with either an intratemporal or intracranial complication. SNHL appears to occur almost twice as often as in developed countries, with a greater proportion being of infectious etiology. In specific populations, the Inuits, Amerindians and Aboriginals, acute and chronic suppurative otitis media are almost endemic, yet both cholesteatoma and serous otitis media are uncommon.

Hearing identification in difficult-to-test children. A study of 142 infants and children

Prior to auditory brainstem response (ABR) threshold determinations in 142 anaesthetized 'difficult-to-test' children, 125 had one or more behavioural auditory tests performed. We used the ABR thresholds as a basis and retrospectively analysed the case records in relation to some parental and behavioural auditory aspects. The accuracy of the parental opinion regarding hearing has been evaluated, and showed a relatively high rate of false-negatives (29%). In contrast, the presence of a hearing loss was correctly identified in 53%. The reliability of one or more standard behavioural auditory tests was poor in children with normal hearing, but in hearing impaired, there was agreement between ABR and behavioural results in more than 70% of cases. Median age at the ABR examination was 32 months. These and other results are discussed in view of the need to minimize diagnostic delay.

Hearing impairment in connection with preauricular tags

Between 1977 and 1984, 230 newborns (5.4/1,000 livebirths) were registered at the two maternity hospitals of Göteborg as having preauricular tags. Of these 188 were available for hearing assessment. In 10 children (5%) the tag was associated with other malformations of the ear/face region. All these children had hearing impairment (HI), 8 conductive, 1 sensorineural and 1 mixed. In 178 neonates the tag was the only defect. Of these, 23 (13%) were found to have HI, all sensorineural and of mild to moderate degree. In the total group of children a positive family history for HI was found in 29% and for malformation in 24%. In the children where HI was found (33 cases in total) the figures for heredity rose to 67% (HI) and 30% (malformation). In the 23 cases with ear tag and HI, a hereditary tendency for HI was found to be 78%. Accordingly there is a clearly elevated risk for HI in connection with ear tags and we therefore recommend routine hearing assessment in all children with preauricular tags.

Screening for auditory dysfunction in high risk neonates

Brainstem auditory evoked responses were recorded in 117 pre-term and 71 full-term infants from the general population of infants born at a referral obstetric unit. The threshold intensity required to evoke a reliable BAER was determined at different post-menstrual ages (PMAs) and in many cases at follow-up clinics. The BAER thresholds for 12 infants born and tested at less than 31 wk PMA were all greater than or equal to 50 dBHL. Sixty-two low-gestational-age infants who were tested between 31 and 36 wk PMA had BAER thresholds between less than or equal to 30 dBHL and greater than or equal to 80 dBHL. The majority of pre-term and term infants tested at term equivalent age had BAER thresholds less than or equal to 30 dBHL. Longitudinal studies also indicated that BAER thresholds can decline rapidly during the pre-term period. Follow-up studies showed that those pre-term and term infants with BAER thresholds less than or equal to 30 dBHL had normal auditory thresholds as determined using conventional behavioural testing at 4 or more months of age. Of those infants with BAER thresholds greater than or equal to 40 dBHL at the time of discharge or at term equivalent age, 67% (n = 16) were confirmed later as having a moderate to profound hearing deficit. The remaining 8 infants in this group had had BAER thresholds at term of 40 or 50 dBHL and had normal BAER and behavioural thresholds at follow-up. The cross-sectional and longitudinal data indicate that the majority of low-gestational-age infants who are at risk of hearing deficit achieve BAER thresholds less than or equal to 30 dBHL by term equivalent age. We recommend that auditory screening of infants in this group is best performed at the time of discharge from hospital or at term equivalent age, whichever is the later. Those infants with thresholds greater than or equal to 40 dBHL at that time should be encouraged to attend follow-up testing and, if high thresholds persist, they should then be referred on for behavioural testing and assessment for habilitative support.