Cause of hearing loss in the high-risk premature infant

Periodic change of body position under phototherapy in term and preterm neonates with hyperbilirubinaemia

BACKGROUND

Phototherapy is the mainstay of treatment of neonatal hyperbilirubinaemia. Periodic change in position of the neonate under phototherapy (from supine to prone or lateral positions) may improve the efficiency of phototherapy by hastening the access of phototherapy light to bilirubin deposited in different parts of the skin and subcutaneous tissue.

OBJECTIVES

To evaluate the effects of periodic change of body position during phototherapy as compared to no prescribed change in body position, on serum total bilirubin level and duration of treatment in neonates with unconjugated hyperbilirubinaemia during the first 28 days of life. Secondary objectives of the review included evaluation of the efficacy of periodic change of body position on the need for or number of exchange transfusions, incidence of bilirubin-induced neurological damage (BIND), side effects of phototherapy, and sudden infant death syndrome (SIDS).

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to run comprehensive searches in the Cochrane Central Register of Controlled Trials (CENTRAL; 2021, Issue 3) in the Cochrane Library and Ovid MEDLINE and Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Daily and Versions on 5 March 2021. We also searched clinical trials databases and the reference lists of included studies and relevant reviews for randomised controlled trials (RCTs) and quasi-RCTs.

SELECTION CRITERIA

We included RCTs and quasi-RCTs if they enrolled neonates (term and preterm) of either gender with unconjugated hyperbilirubinaemia requiring phototherapy and compared periodic change of the body position of the infant under phototherapy with no prescribed change in body position.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data, consulting with a third review author in the case of disagreement. We used standard Cochrane methodological procedures, including assessing the risk of bias of included studies. We used the GRADE approach to assess the certainty of evidence. Primary outcomes were the duration of phototherapy and rate of fall of serum bilirubin at 24 hours. Secondary outcomes included the need for exchange transfusion, number of exchange transfusions, incidence of BIND, and SIDS.

MAIN RESULTS

We included five studies (343 neonates) with an overall high risk of bias in the review. The body position under phototherapy was changed every two hours or every two-and-a-half hours in two studies each, and every three hours in one study. Three of the five studies included healthy term neonates, whilst the other two studies also included preterm neonates (≥ 33 weeks' gestation); however, separate data about review outcomes in preterm neonates were not available. Periodic change in body position may lead to little or no difference in the duration of phototherapy (mean difference (MD) 1.71 hours, 95% confidence interval (CI) -3.17 to 6.59 hours; I² = 58%; 4 studies, 231 participants; low certainty evidence). Only one study reported the rate of fall of serum total bilirubin at 24 hours of starting the phototherapy. Periodic change in body position may lead to little or no difference in the rate of fall of serum total bilirubin at 24 hours (MD 0.02 mg/dL/h, 95% CI -0.02 to 0.06 mg/dL/h; 1 study, 100 participants; low certainty evidence). We downgraded the certainty of evidence to low due to risk of bias and imprecision. None of the included studies reported the need for or number of exchange transfusions, incidence of BIND, or SIDS. Lack of separate data precluded subgroup analysis.

AUTHORS' CONCLUSIONS

The available evidence is insufficient to determine the effects of periodic change of body position compared with no prescribed change of body position under phototherapy. There is low certainty evidence that there may be little or no difference in the duration of phototherapy and rate of fall in bilirubin at 24 hours of starting phototherapy between periodic change in body position and no prescribed change of body position under phototherapy in term and preterm neonates. None of the included studies reported the effect of change of position on the need for or number of exchange transfusions, incidence of BIND, or SIDS. One study is awaiting classification and could not be included in the review. Further studies are needed to evaluate the effect of periodic change in body position under phototherapy, especially in neonates with haemolytic hyperbilirubinaemia and in very preterm neonates. The results of this systematic review apply mainly to neonates born at late-preterm or term gestation receiving phototherapy for non-haemolytic hyperbilirubinaemia.

Sex-specific association of high maternal psychological stress during pregnancy on newborn birthweight

Birthweight is an important predictor of newborn health and has been linked to maternal psychological stress during pregnancy. However, it is unclear whether prenatal stress affects birthweight similarly for both male and female infants. We used a well-established pregnancy cohort to investigate the impact of high maternal psychological stress during pregnancy on birthweight as a function of infant sex. Overall, 5702 mother-newborn pairs were analysed. Of these, 198 mothers reported high levels of stress using the Psychological Stress Measure (nine-items version; PSM-9). Maternal psychological stress was assessed between the 24^th and 28^th week of gestation and analyses were performed jointly and independently as a function of neonatal sex (separate analyses for male and female infants). Newborns exposed to high maternal psychological stress during pregnancy (a score above 26 measured using the PSM-9 questionnaire, corresponding to >97.5^th percentile) were compared to newborns of mothers who reported lower stress. ANCOVAs revealed that high levels of maternal stress during pregnancy were linked to infant birthweight as a function of infant sex. Male infants of mothers who reported high levels of stress had a greater birthweight whereas female infants had a lower birthweight under the same conditions, in comparison to mothers who did not report greater levels of stress. Although the effect size is small, these results underline the possibility that male and female fetuses may use different strategies when adapting to maternal adversity and highlight the need to consider infant sex as a moderator of the association between maternal psychological stress during pregnancy and infant birthweight.

Negative Effects of Noise on NICU Graduates' Cochlear Functions

To evaluate the adverse effects of noise on hearing. Methods: Thirty-two infants that had been admitted to neonatal intensive care unit (NICU) and 25 healthy controls were included in this study. Noise levels were recorded continously during the hospitalization period. Results: All healthy controls passed the hearing screening tests before discharge and on the sixth-month follow up. Hospitalized infants had lower "Distortion Product Auto Acoustic Emission Signal Noise Ratio" (DPOAE SNR) amplitudes (dB) at five frequencies (1001, 1501, 3003, 4004, 6006 Hz in both ears). DPOAE fail rates at 1001 Hz and 1501 Hz were higher than in hospitalized infants (81.8% and 50.0% vs 20.0% and 4.0%). Infants who failed the test at 1001 and 1501 Hz were exposed to noise above the recommended maximum level for longer periods of time. Conclusion: Hearing tests performed at sixth-months of life were adversely affected in NICU graduates.

The Importance of Reverberation for the Design of Neonatal Incubators

Low frequency noises are predominant in neonatal intensive care units (NICUs). Some studies affirm that neonates can perceive noises from 113 Hz, and can therefore be affected by sound sources with high spectral content at low frequencies (e.g., incubator engine, air fan). Other studies suggest that reverberation amplifies noise within incubators. In this paper, the reverberation time (T, T ₃₀) within an incubator with standard dimensions was measured in one-third octave bands. To get reliable results, the T was measured in 15 positions at the neonate's ear height, in a room with low T values (to reduce the influence of the room in the results), using an impulsive sound method. Results show a heterogeneous T distribution at the neonate's ear height, with maximum average T differences between positions of 1.07 s. The highest average T of all microphone positions is 2.27 s at 125 Hz, an extremely high mean value for such a small space. As the frequency of electrical devices in America is 60 Hz, some harmonics lay within the one-third octave band of 125 Hz, and therefore may create a very reverberant and inappropriate acoustic environment within the audible spectrum of neonates. As the acoustic environment of the incubator and the room are coupled, it is expected that the results are higher in the NICUs than in the room where the measurements were conducted, as NICUs are more reverberant. Therefore, it is recommended that the T will be limited in the international standards, and that incubator designers take it into account.

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.

Maternal and Placental Factors Associated with Congenital Hearing Loss in Very Preterm Neonates

BACKGROUND

Sensorineural hearing loss (SNHL) is a multifactorial disease that more frequently affects preterm newborns. Although a number of maternal conditions have been reported to be associated with preterm birth, little information is available concerning maternal risk factors for the development of SNHL. We aimed to identify maternal and placental risk factors associated with a "refer" result on the newborn hearing screening (NHS) test and subsequently confirmed SNHL in very preterm neonates.

METHODS

This retrospective cohort study included 267 singleton neonates who were born alive after ≤ 32 weeks. Histopathologic examination of the placenta was performed, and clinical data were retrieved from a computerized perinatal database. Cases with two abnormal findings, "refer" on the NHS test, and presence of SNHL on the confirmation test were retrospectively reviewed based on electronic medical records.

RESULTS

Forty-two neonates (15.7%) showed a "refer" result, and, on the confirmation test, permanent SNHL was identified in 1.87% (5/267) of all neonates. Multivariate regression analysis revealed that the presence of funisitis was independently associated with a "refer" on the NHS test, whereas use of antenatal corticosteroids was statistically significantly associated with a reduced incidence of "refer" on the screening test. Neither histologic chorioamnionitis nor prematurity (as defined by low gestational age and birth weight) was associated with a "refer" on the NHS test. By contrast, multivariate analysis with occurrence of SNHL as a dependent variable identified no significant associations with the parameters studied, probably owing to the small total number of neonates with permanent SNHL.

CONCLUSION

Presence of funisitis was significantly and independently associated with increased risk of abnormal NHS results, while administration of antenatal corticosteroids was related to a normal NHS result. These findings support the hypothesis that a systemic fetal inflammatory response, manifested as funisitis, might play a role in the pathogenesis of SNHL in preterm neonates.

Universal Hearing Screening in Newborns Using Otoacoustic Emissions and Brainstem Evoked Response in Eastern Uttar Pradesh

The objectives were to determine the incidence of hearing impairment in a standardized population of neonates and to determine the significance of association of epidemiological and risk factors with neonatal hearing loss. A cohort of 600 newborns was selected for study and divided into two groups-525 in 'No Risk' group and remaining 75 in 'At Risk' group. The study protocol was carried out in three steps: (a) Screening of Hearing Loss with TOAE, done from 36 h after birth to 28 days of life, (b) Re-screening of hearing loss in newborns (of 4-12 weeks of age), who were tested positive for hearing loss in the first screening, done with DPOAE, (c) Confirmation of hearing loss with BERA, in those who were tested positive in both the first and second screening. In the study the incidence of hearing impairment in 600 infants screened was 6.67 per 1000 screened; 3.81 per 1000 screened in the Not at Risk group and 26.67 per 1000 screened in At Risk group. In At Risk group, admitted to the NICU, severe birth asphyxia and hyperbilirubinemia were found to be major risk factors. Loss to follow up was more in Not at Risk group and False Positive cases with TEOAE were more than DPOAE. BERA was found to be must for confirmation of hearing loss. Neonatal Hearing Screening of only At Risk population is likely to miss some hearing loss. Universal Hearing Screening should be the preferred strategy. Good follow up in the 'At Risk' group suggests that initial interventions in NICU had sensitized the parents for the possibility of hearing loss. This study recommends the introduction of two stage neonatal screening-rescreening protocol, using OAE and BERA, in the country in phased manner.

Multicenter neonatal databases: Trends in research uses

BACKGROUND

In the US, approximately 12.7% of all live births are preterm, 8.2% of live births were low birth weight (LBW), and 1.5% are very low birth weight (VLBW). Although technological advances have improved mortality rates among preterm and LBW infants, improving overall rates of prematurity and LBW remains a national priority. Monitoring short- and long-term outcomes is critical for advancing medical treatment and minimizing morbidities associated with prematurity or LBW; however, studying these infants can be challenging. Several large, multi-center neonatal databases have been developed to improve research and quality improvement of treatments for and outcomes of premature and LBW infants. The purpose of this systematic review was to describe three multi-center neonatal databases.

METHODS

We conducted a literature search using PubMed and Google Scholar over the period 1990 to August 2014. Studies were included in our review if one of the databases was used as a primary source of data or comparison. Included studies were categorized by year of publication; study design employed, and research focus.

RESULTS

A total of 343 studies published between 1991 and 2014 were included. Studies of premature and LBW infants using these databases have increased over time, and provide evidence for both neonatology and community-based pediatric practice.

CONCLUSIONS

Research into treatment and outcomes of premature and LBW infants is expanding, partially due to the availability of large, multicenter databases. The consistency of clinical conditions and neonatal outcomes studied since 1990 demonstrates that there are dedicated research agendas and resources that allow for long-term, and potentially replicable, studies within this population.

NICU music therapy: song of kin as critical lullaby in research and practice

Music therapy can improve neonatal function and reduce anxiety in parents during neonatal intensive care unit (NICU) stays. Live music entrained to an infant's observed vital signs, provided by a certified music therapist with First Sounds RBL (rhythm, breath, and lullaby) training, enhanced bonding for infant-parent dyads and triads. The author's song of kin intervention, which employs parent-selected songs, is compared to the presentation of a well-known folk theme ("Twinkle") in 272 neonates. Culturally based, parent-selected, personalized musical tunes provided in song, as a noninvasive intervention, foster optimal, continuous quality of care. Music psychotherapy sessions for parents before working with their infants can instill a potent means of nonconfrontational support, allowing for expression of fear or anxiety related to the premature birth. Although most attention is typically directed to their infant, using music can support the parents' grief and assist in the expression of hope that can instill a sense of security and containment. From the NICU to home, a familiar thread-line theme can be resourced directly from the family and/or parent and applied effortlessly throughout the growing baby's transitional moments.

Triple difficulties in Japanese women with hearing loss: marriage, smoking, and mental health issues

Objective

To examine the consequences of early-onset hearing loss on several social and health measures and any related gender differences in Japanese populations.

Methods

Data from a 2007 nationally representative cross-sectional household survey of 136,849 men and women aged 20 to 39 years were obtained (prevalence of self-reported hearing loss: 0.74%). We focused particularly on four social and health measures: employment status (employed/unemployed), marital status (married/unmarried), smoking behavior (yes/no), and psychological distress (K6 instrument: ≥ 5 or not). We examined the association of hearing loss for each measure using generalized estimating equations to account for correlated individuals within households.

Findings

There was no significant association with employment status (p = 0.447). Men with hearing loss were more likely to be married, whereas women with hearing loss were less likely to be married (p < 0.001 for interaction). Although hearing loss was not associated with a current smoking status in men, women with hearing loss were more likely to be current smokers (p < 0.001 for interaction). Moreover, hearing loss was associated with psychological distress in men and women (both p < 0.001).

Conclusion

These findings suggest that hearing loss is related to social and health issues in daily life, including a lower likelihood of marriage, more frequent smoking, and poorer mental health, especially in women. These issues may reflect a gap between the actual needs of women with hearing loss and the formal support received as a result of existing public health policies in Japan.

Assessment of Hearing Loss by OAE in Asphyxiated Newborns

BACKGROUND

Severe birth asphyxia (apgar < 7 at the 5th minute of birth) is recognized as a hearing loss risk factor by the joint committee on infant hearing (JCIH). About half of the newborns with hearing loss do not indicate any sign and risk factor at birth. Accordingly, the joint committee recommended performance of hearing screening test in 2000, especially for babies born with risk factors.

OBJECTIVES

The aim of this study was to evaluate hearing loss in asphyxiated neonates. Early diagnosis would result in early treatment of these newborns.

PATIENTS AND METHODS

We assessed the relationship between asphyxia and hearing impairment in newborns admitted to a referral hospital, Tehran, Iran within 3 years (2003 - 2006). Hearing problems were diagnosed and followed by otoacoustic emission (OAE) in the third and fifth days of birth. Asphyxiated neonates with abnormal OAE were referred to an ENT specialist; second OAE and tympanometry were carried out after 2 weeks. Based on the results, newborns underwent treatment or were discharged.

RESULTS

Of 149 asphyxiated neonates, 80 had mean first minute apgar score of 4.01, and mean 5th minute score was 7.24. Two percent (3/149) of asphyxiated neonates had abnormal OAEs. No statistical correlation was found between the 5th minute apgar score and abnormal OAE (P value = 0.391). However, a significant relationship between the mean birth weight and abnormal OAE (P value = 0.0406) was found.

CONCLUSIONS

It seems that birth asphyxia is not correlated with hearing loss.

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.

Neonatal incubators: a toxic sound environment for the preterm infant?*

BACKGROUND

High sound pressure levels may be harmful to the maturing newborn. Current guidelines suggest that the sound pressure levels within a neonatal intensive care unit should not exceed 45 dB(A). It is likely that environmental noise as well as the noise generated by the incubator fan and respiratory equipment may contribute to the total sound pressure levels. Knowledge of the contribution of each component and source is important to develop effective strategies to reduce noise within the incubator.

AIMS

The objectives of this study were to determine the sound levels, sound spectra, and major sources of sound within a modern neonatal incubator (Giraffe Omnibed; GE Healthcare, Helsinki, Finland) using a sound simulation study to replicate the conditions of a preterm infant undergoing high-frequency jet ventilation (Life Pulse, Bunnell, UT).

METHODS

Using advanced sound data acquisition and signal processing equipment, we measured and analyzed the sound level at a dummy infant's ear and at the head level outside the enclosure. The sound data time histories were digitally acquired and processed using a digital Fast Fourier Transform algorithm to provide spectra of the sound and cumulative sound pressure levels (dBA). The simulation was done with the incubator cooling fan and ventilator switched on or off. In addition, tests were carried out with the enclosure sides closed and hood down and then with the enclosure sides open and the hood up to determine the importance of interior incubator reverberance on the interior sound levels

RESULTS

With all the equipment off and the hood down, the sound pressure levels were 53 dB(A) inside the incubator. The sound pressure levels increased to 68 dB(A) with all equipment switched on (approximately 10 times louder than recommended). The sound intensity was 6.0 × 10(-8) watts/m(2); this sound level is roughly comparable with that generated by a kitchen exhaust fan on high. Turning the ventilator off reduced the overall sound pressure levels to 64 dB(A) and the sound pressure levels in the low-frequency band of 0 to 100 Hz were reduced by 10 dB(A). The incubator fan generated tones at 200, 400, and 600 Hz that raised the sound level by approximately 2 dB(A)-3 dB(A). Opening the enclosure (with all equipment turned on) reduced the sound levels above 50 Hz by reducing the revereberance within the enclosure.

CONCLUSION

The sound levels, especially at low frequencies, within a modern incubator may reach levels that are likely to be harmful to the developing newborn. Much of the noise is at low frequencies and thus difficult to reduce by conventional means. Therefore, advanced forms of noise control are needed to address this issue.

Chronic bilirubin encephalopathy: diagnosis and outcome

Chronic bilirubin encephalopathy (kernicterus) can be diagnosed using semi-objective criteria based on history, physical and neurological examination and laboratory findings including auditory brainstem responses and magnetic resonance imaging. Classical kernicterus is a well-described clinical tetrad of (i) abnormal motor control, movements and muscle tone, (ii) an auditory processing disturbance with or without hearing loss, (iii) oculomotor impairments, especially impairment of upward vertical gaze, and (iv) dysplasia of the enamel of deciduous teeth. Subtle kernicterus or bilirubin-induced neurologic dysfunction (BIND) refers to individuals with subtle neurodevelopmental disabilities without classical findings of kernicterus that, after careful evaluation and consideration, appear to be due to bilirubin neurotoxicity. Kernicterus can be further classified as auditory predominant or motor predominant and characterized based on the severity of clinical sequelae. Proposed research definitions for kernicterus diagnosis in infants from 3 to 18 months are reviewed, as are treatments of auditory and motor deficits and other complications of bilirubin encephalopathy.

The infant incubator in the neonatal intensive care unit: unresolved issues and future developments

Since the 19th century, devices termed incubators were developed to maintain thermal stability in low birth weight (LBW) and sick newborns, thus improving their chances of survival. Remarkable progress has been made in the production of infant incubators, which are currently highly technological devices. However, they still need to be improved in many aspects. Regarding the temperature and humidity control, future incubators should minimize heat loss from the neonate and eddies around him/her. An unresolved issue is exposure to high noise levels in the Neonatal Intensive Care Unit (NICU). Strategies aimed at modifying the behavior of NICU personnel, along with structural improvements in incubator design, are required to reduce noise exposure. Light environment should be taken into consideration in designing new models of incubators. In fact, ambient NICU illumination may cause visual pathway sequelae or possibly retinopathy of prematurity (ROP), while premature exposure to continuous lighting may adversely affect the rest-activity patterns of the newborn. Accordingly, both the use of incubator covers and circadian lighting in the NICU might attenuate these effects. The impact of electromagnetic fields (EMFs) on infant health is still unclear. However, future incubators should be designed to minimize the EMF exposure of the newborn.

Late morbidity during childhood and adolescence in previously premature neonates after patent ductus arteriosus closure

The health status of previously premature neonates after closure of a patent ductus arteriosus (PDA) was analyzed in childhood and adolescence. Physician questionnaires were used to study 180 hospital survivors among 210 consecutive premature neonates who underwent PDA closure between 1985 and 2005. Complete follow-up data were obtained for 129 patients (72%). During a median follow-up period of 7 years (range, 2-22 years), three late deaths (2.3%) had occurred. Only 45% of the patients were considered healthy. Morbidity included developmental delay (41.1%), pulmonary illness (12.4%), neurologic impairment (14.7%), hearing impairment (3.9%), gastrointestinal disease (3.1%), and thoracic deformity (1.2%). None of the adverse variables during the neonatal period (intraventricular hemorrhage, bradycardia apnea syndrome, bronchopulmonary dysplasia, pulmonary bleeding, hyaline membrane disease, artificial respiration time [continuous positive airway pressure + intubation], or necrotizing enterocolitis) statistically predicted respective system morbidity at the follow-up evaluation. Hyaline membrane disease (odds ratio, 2.5; p = 0.026) and longer hospitalization time (odds ratio, 1.2 days per 10 hospitalization days; p = 0.032) in the newborn period were significant predictors of an unhealthy outcome at the last follow-up evaluation. Survival until childhood after closure of a hemodynamically significant PDA in premature neonates is satisfactory. However, physical and neurodevelopmental co-morbidity persist for half of the patients, perhaps as a sequela of prematurity unrelated to ductus closure.

Unbound (free) bilirubin: improving the paradigm for evaluating neonatal jaundice

BACKGROUND

The serum or plasma total bilirubin concentration (B(T)) has long been the standard clinical laboratory test for evaluating neonatal jaundice, despite studies showing that B(T) correlates poorly with acute bilirubin encephalopathy (ABE) and its sequelae including death, classical kernicterus, or bilirubin-induced neurological dysfunction (BIND). The poor correlation between B(T) and ABE is commonly attributed to the confounding effects of comorbidities such as hemolytic diseases, prematurity, asphyxia, or infection. Mounting evidence suggests, however, that B(T) inherently performs poorly because it is the plasma non-protein-bound (unbound or free) bilirubin concentration (B(f)), rather than B(T), that is more closely associated with central nervous system bilirubin concentrations and therefore ABE and its sequelae.

CONTENT

This article reviews (a) the complex relationship between serum or plasma bilirubin measurements and ABE, (b) the history underlying the limited use of B(f) in the clinical setting, (c) the peroxidase method for measuring B(f) and technical and other issues involved in adapting the measurement to routine clinical use, (d) clinical experience using B(f) in the management of newborn jaundice, and (e) the value of B(f) measurements in research investigating bilirubin pathochemistry.

SUMMARY

Increasing evidence from clinical studies, clinical experience, and basic research investigating bilirubin neurotoxicity supports efforts to incorporate B(f) expeditiously into the routine evaluation of newborn jaundice.

Permanent bilateral sensory and neural hearing loss of children after neonatal intensive care because of extreme prematurity: a thirty-year study

OBJECTIVE

We present population-based, childhood prevalence rates of and neonatal risk factors for permanent hearing loss among extremely premature infants.

METHODS

By using an inception-cohort, longitudinal study design for 1974-2003, we studied permanent hearing loss among 1279 survivors with gestational age of < or =28 weeks and birth weight of <1250 g (mortality rate: 42.7%; lost to follow-up monitoring: 4.7%) Newborn hearing screening, performed by experienced pediatric audiologists, used click-evoked auditory brainstem response testing after 1975. Survivors underwent repeated behavioral audiologic testing and multidisciplinary follow-up monitoring. Permanent hearing loss was defined as mild/moderate (26-70 dB hearing level), severe/profound (71 to >90 dB hearing level), delayed-onset (diagnosed after previously normal hearing), or progressive (increase in loss of > or =15 dB hearing level). Permanent hearing loss rates were established at 3 years of age, with newborn, infant, and >5-year final hearing outcomes being recorded. Risk factors were compared for children with and without hearing loss, odds ratios were calculated, and prediction performance was determined through area under the curve analysis.

RESULTS

Forty (3.1%) of 1279 survivors 3 years of age had permanent hearing loss and 24 (1.9%) had severe/profound loss, with no changes over time. Bilateral delayed-onset loss occurred for 4 children (10%) and progressive loss for 11 children (28%). One child had auditory neuropathy, and 29 (73%) had multiple disabilities. Prolonged oxygen use, gastrointestinal surgery, patent ductus arteriosus ligation, and low socioeconomic index yielded good prediction of permanent hearing loss; oxygen use was the most significant predictor of severe/profound loss.

CONCLUSIONS

Permanent hearing loss remains an adverse outcome of extreme prematurity, complicated by significant delayed-onset and progressive loss. Prolonged supplemental oxygen use is a marker for predicting permanent hearing loss; this requires detailed analysis of the pathophysiologic features, to reduce the prevalence of permanent hearing loss.

Unbound bilirubin predicts abnormal automated auditory brainstem response in a diverse newborn population

OBJECTIVE

The objective of this study was to determine if plasma unbound or 'free' bilirubin concentration (B(f)) measured during the first 30 days of life is associated with subsequent abnormal hearing screening testing by automated auditory brainstem response (AABR) in a diverse population of newborns.

STUDY DESIGN

An observational study of newborns receiving AABR, plasma total bilirubin concentration (TBC) and B(f) measurements and without underlying conditions known to affect hearing was conducted. Logistic regression was used to determine associations between abnormal AABR and B(f) or TBC. The impacts of a variety of clinical factors on the regression model were also assessed.

RESULT

A total of 191 patients with birth weights and gestations ranging from 406 to 4727 g and 24 to 42 weeks, respectively, were studied. Among them, 175 (92%) had normal (bilateral PASS) AABR and 16 had abnormal AABR (6 had unilateral REFER AABR, and 10 had bilateral REFER AABR). Mean TBC was not significantly different in babies with normal or abnormal AABR, but mean B(f) was greater in the latter group (1.76 versus 0.93 microg per 100 ml, respectively, P=0.012). B(f), but not TBC, was associated with an abnormal AABR (B(f) adjusted odds ratio 3.3, 95% CI 1.8 to 6.1). Comparing receiver-operating characteristics curves, the B(f)/TBC ratio was a better predictor of an abnormal AABR than B(f) alone. Intraventricular hemorrhage was the only confounding clinical variable.

CONCLUSION

An abnormal AABR is associated with an elevated B(f) or B(f)/TBC ratio, but not the TBC alone. The prevalence of bilirubin neurotoxicity as a cause of audiological dysfunction may be underestimated if the TBC alone is used to assess the severity of newborn jaundice.

Assessment of deafmute patients: a study of ten years

Present prospective study was conducted on 350 patients presenting with chief complaints of impaired hearing and delayed speech from 1996-2006. The aim of the present study was to find out the prevalence of deafmutism in our area, the aetiology of childhood deafness and to ascertain the role of acoustic reflex test (ART) for hearing screening considering brain stem evoked response audiometry (BSERA) as gold standard. A detailed history, clinical and other relevant systemic examination and investigations were done to find out the cause. All patients were subjected to ART test and BSERA. Male to female ratio was 2.1:1. Prevalence was found to be 5.59 per one lac population in our district. The commonest age of presentation was in the second decade. The causes for childhood deafness were genetic (15.8%), embryopathies (10%), perinatal (10.8%) and postnatal problems (12.5%). In 50.6% cases it was aediopathic. Congenital syndromic abnormalities were found in 5.4% patients. In BSERA 21% patients were found to have residual hearing varying from 60 dB to 100dB. The positive predictive value of ART was found to be low (10.4%). Hence it was recommended that ART should not be used as screening tool for childhood deafness.

Hearing loss in children with very low birth weight: current review of epidemiology and pathophysiology

An association between birth weight <1500 g (very low birth weight (VLBW)) and hearing loss has been long recognised. As universal hearing screening programmes have become widely implemented and the survival rate of VLBW babies in modern intensive care units has increased, we have gained a substantially better understanding of the nature of this problem. However, many gaps in our knowledge base exist. This review describes recent data on hearing loss in the VLBW population and explains the current level of understanding about the physiological basis underlying the auditory deficits in these patients. Although VLBW alone may not have a severe impact on hearing, it is commonly associated with multiple other risk factors that can alter hearing in a synergistic fashion. Therefore, the risk of hearing loss is substantially higher than in the general newborn population. Also, it is important to perform a more comprehensive audiometric evaluation than standard otoacoustic emission screening for infants who are in the neonatal intensive care unit in order not to miss hearing loss due to retrocochlear pathology. Furthermore, children with VLBW are also at increased risk of experiencing progressive or delayed-onset hearing loss, and thus should continue to have serial hearing evaluations after discharge from the neonatal intensive care unit.

Low prevalence of hearing impairment among very low birthweight infants as detected by universal neonatal hearing screening

OBJECTIVES

To (a) study the prevalence of hearing impairment in a cohort of very low birthweight (VLBW) infants and (b) evaluate the effectiveness of transient evoked otoacoustic emissions (TEOAE) as a first stage in-hospital hearing screening tool in this population.

STUDY DESIGN

The study group was a cohort of 346 VLBW infants born in 1998-2000 at The Sheba Medical Center. The prevalence of hearing impairment in the study group was compared with that of all other newborn infants participating in a universal newborn hearing screening programme during the same period. To evaluate the effectiveness of TEOAE, a control group of 1205 healthy newborns who had no known risk factors for hearing impairment was selected. The results and follow up of hearing screening for these infants were examined retrospectively.

RESULTS

Only one VLBW infant (0.3%) was diagnosed with bilateral sensory-neural hearing loss. In addition, nine infants (2.7%) were diagnosed with conductive hearing loss. Bronchopulmonary dysplasia and low Apgar score were the most significant factors for predicting the occurrence of conductive hearing loss. The percentage of VLBW infants who successfully passed the in-hospital TEOAE screening was 87.2, compared with 92.2% in the full term control group. No false negative cases were detected on follow up.

CONCLUSIONS

The study shows a low incidence of sensory-neural hearing loss in a cohort of VLBW infants and a relatively high incidence of conductive hearing loss. TEOAE screening was found to be an effective first stage in-hospital hearing screening tool in this population.

Hyperbilirubinemia and kernicterus

This article describes new findings concerning the basic science of bilirubin neurotoxicity, new considerations of the definition of clinical kernicterus, and new and useful tools to diagnose kernicterus in older children, and discusses treatments for kernicterus beyond the newborn period and why proper diagnosis is important.

Transient bilirubin encephalopathy and apnea of prematurity in 28 to 32 weeks gestational age infants

OBJECTIVE

Apnea of prematurity (AoP) is, in part, a reflection of brainstem-mediated respiratory control system maturation. We previously demonstrated changes in brainstem function in relation to hyperbilirubinemia (bilirubin encephalopathy, (BE)) as evaluated by auditory brainstem evoked responses (ABR) in infants 28 to 32 weeks gestational age (GA). We hypothesized that in this population, as bilirubin increases and causes auditory brainstem dysfunction, respiratory control system may also be adversely affected leading to increased frequency of AoP.

STUDY DESIGN

We studied 100, 28 to 32 weeks GA infants and identified 66 with normal and 34 with abnormal ABR progression in temporal relation to hyperbilirubinemia (BE). The abnormal ABR progression was associated with elevated bilirubin, specifically elevated unbound bilirubin levels. A blinded, retrospective chart review quantified the amount of weekly apnea and bradycardia events during the hospital stay, total duration of methylxanthine treatment, total duration of mechanical ventilation, CPAP, and/or nasal cannula, and risk factors for apnea (sepsis, IVH grade >II, asphyxia). Since mechanical ventilation confounds the identification of apnea, infants requiring mechanical ventilation were excluded from further review (n = 60; 21 with BE and 39 with normal ABR progression). Data from the remaining 40 infants were analyzed. Student's t-test was used to analyze continuous variables if the distribution was normal otherwise Wilcoxon-ranked-sum test was used. chi(2) was used to analyze nominal variables. A p < or =0.05 was considered significant.

RESULTS

There was no difference in risk factors between infants with and without BE. BE was identified on day 3 (median; range 1 to 6 days). Patients with BE had significantly more apneic events (15 vs 2, p = 0.0009), bradycardic events (14 vs 1, p = 0.02), and required more prolonged treatment with CPAP (2.2 vs 0.5 days, p = 0.007), nasal cannula (6.6 vs 2.2 days, p = 0.02), and methylxanthines (9.5 vs. 1.9 days, p = 0.002) than those with normal ABR progression. The difference in the incidence of apnea and bradycardia between infants with and without BE was most pronounced during the first week.

CONCLUSIONS

Premature infants with transient bilirubin encephalopathy as defined by abnormal ABR progression in relation to hyperbilirubinemia have more concurrent apneic events and require more prolonged respiratory support and medications.

Clinical assessment of bilirubin-induced neurotoxicity in premature infants

The clinical assessment of bilirubin-induced neurotoxicity in premature infants remains difficult in the absence of a gestational age-specific total or free (unbound) bilirubin level that predicts bilirubin-induced neurotoxicity. Because the total serum bilirubin concentration is an unreliable predictor of bilirubin-induced neurotoxicity in premature infants, alternative mean for predicting bilirubin-induced neurotoxicity in jaundiced preterm newborns is needed. Over the last few years, we have witnessed substantial gain in our knowledge involving usefulness of bilirubin-binding variables (total bilirubin, free bilirubin, bilirubin:albumin molar ratio) for clinical assessment of bilirubin-induced neurotoxicity in preterm infants. The knowledge gained has provided impetus for more clinical studies that are geared toward confirming the usefulness of free bilirubin as a predictor of bilirubin-induced neurotoxicity and identifying the gestational age-specific free bilirubin level that may increase the risk of bilirubin-induced neurotoxicity in premature infants. The paper has attempted to provide an overview of bilirubin-induced auditory toxicity along with the existing clinical evidence in favor of free bilirubin assay and usefulness of auditory brainstem evoked response for evaluation of bilirubin-induced neurotoxicity in premature infants. In addition, the author has described findings that suggest an association of apnea, a clinical manifestation, with acute bilirubin encephalopathy in premature infants.

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%).

Behavioural and physiological reactivity to noise in the newborn

OBJECTIVE

To assess the electromyographic (EMG) and behavioural reactivity of a group of newborn infants exposed to noisy stimulation of various intensity recorded in the Paediatric intensive care Unit (PICU).

METHODS

The study was performed at the nursery of the Paediatrics Department (University of Padova) on a group of 21 healthy newborns (mean 39 weeks of gestation), assessed between 24 and 72 h after birth. The study involved taking EMG recordings of the corrugator supercilii muscle and assessing the infant's behaviour at the baseline (15 seconds before stimulation), during noisy stimulation (for 1-2 seconds) and during recovery (15 seconds in three subphases). The noises, previously recorded in PICU, had four different intensities and were administered in random order to all infants. Descriptive analysis and repeated-measures analysis of variance (anova) were performed on the EMG and behavioural data.

RESULTS

The infants demonstrated a significant reaction to the noises both in the EMG recordings and in behavioural changes, especially during intense noisy stimulation. The reaction lasted longer than the stimulation period, preventing the infants from returning to the baseline condition.

CONCLUSIONS

Exposure to high-intensity noise produced in PICU causes evident behavioural and physiological effects (EMG). This is a field of study that could have important repercussions, given the medium- and long-term effects of repeated noise stimulation.

Bilirubin toxicity in the developing nervous system

Bilirubin toxicity remains a significant problem despite recent advances in the care of jaundiced (hyperbilirubinemic) neonates. A recent surge in reported cases of classical kernicterus, due in part to earlier hospital discharge and relaxation of treatment criteria for hyperbilirubinemia, and new reports of hyperbilirubinemia-induced auditory dysfunction using evoked potential based infant testing and hearing screening, underscore the need to better understand how hyperbilirubinemia causes brain damage in some infants, especially because the damage is preventable. Recent progress in understanding bilirubin binding and neurotoxicity resulting from unbound or "free" unconjugated bilirubin, how bilirubin affects the central nervous system in vivo and in vitro, and the use of new clinical tools in neonates, for example magnetic resonance imaging revealing bilateral lesions in globus pallidus and subthalamus, and abnormal brainstem auditory evoked potentials with normal inner ear function, may lead to improved detection and prevention of neurologic dysfunction and damage from bilirubin. Finally, the concern is raised that partial or isolated neurologic sequelae, for example auditory neuropathy and other central auditory processing disorders, may result from excessive amount and duration of exposure to free, unconjugated bilirubin at different stages of neurodevelopment.

The otolaryngologist's role in management of hearing loss in infancy and childhood

This article reviews the role of the otolaryngologist-head and neck surgeon-in the diagnosis and treatment of hearing loss in infants and young children. The otolaryngologist is well-versed in the anatomy, physiology, and pathophysiology of the auditory system, as well as the craniofacial syndromes that can involve the head and neck in combination with deafness. In this paper, the various causes of congenital hearing loss are described, as well as the steps required for proper diagnosis. Finally, surgeries used by otolaryngologists to treat childhood hearing loss, their indications, and outcomes, are discussed.

Nongenetic causes of hearing loss

Nongenetic as well as genetic etiologies must be explored in the child with identified hearing loss. Graduates of the neonatal intensive care unit are at increased risk for developing hearing loss due to hypoxia, hyperbilirubinemia, very low birth weight, and ototoxic medications. Although meningitis has decreased in frequency, it is still a risk factor for hearing loss. Cytomegalovirus remains the most common congenital infection and a relatively common etiology of hearing loss, which can be progressive. Preventable causes of hearing loss include those caused by head trauma, noise, and ototoxic medications. Identification of the etiology of hearing loss can facilitate the development of a treatment and management plan.

Cognitive and behavioral deficits in premature graduates of intensive care

A substantial number of VLBW graduates of intensive care develop cognitive and behavioral problems, even in the absence of neuroimaging abnormalities. Although this article has highlighted the potential, important, contributing role of medical and stressful, neonatal, environmental conditions to the development of these deficits, it is not all-encompassing, and there are additional prenatal (ie, in utero stress, drug exposure) and neonatal (ie, infectious) contributing factors. The long-term, outcome data presented in this article are pertinent to the more mature, VLBW infant, and it remains unclear and critically important to delineate the long-term, neurobehavioral outcome of those extremely low birth-weight survivors born at the cutting limit of viability.

Changes in calcium-binding protein expression in the auditory brainstem nuclei of the jaundiced Gunn rat

Sensorineural hearing loss and auditory dysfunction are major sequelae of neonatal hyperbilirubinemia. The sites and cellular effects of bilirubin toxicity in the auditory brainstem pathway are not easily detected. Since altered intracellular calcium homeostasis may play a role in neuronal cell death, we hypothesized that the expression of calcium-binding proteins may be altered in the classic animal model of bilirubin neurotoxicity. The expression of the calcium-binding proteins, calbindin-D28k and parvalbumin, in the brainstem auditory pathway of homozygous recessive jaundiced (jj) Gunn rats was examined by light and electron microscopic immunohistochemistry at 18 days postnatally and compared to the findings obtained from age-matched non-jaundiced heterozygous (Nj) littermate control rats. Immunoreactive staining for both calbindin and parvalbumin was reduced in the cochlear nuclei and the superior olivary complex in jj rats. The extent of the reduction in immunoreactivity was related to the severity of the clinical symptoms. By contrast, immunoreactive staining in other brainstem areas (e.g., dorsal and ventral nuclei of the lateral lemniscus, inferior colliculus), thalamic (medial geniculate body) auditory areas, and neighboring non-auditory structures was similar in jaundiced and control rats. Calbindin-immunoreactive staining in the superior paraolivary and medial superior olivary nuclei in Nj rats was associated with myelinated axons, whereas parvalbumin-immunoreactive staining was localized postsynaptically in neuronal somata and dendrites. Immunoreactive staining for the calcium-binding proteins calbindin and parvalbumin in lower brainstem auditory nuclei shows abnormalities in areas susceptible to the effects of hyperbilirubinemia and provides a sensitive new way to assess bilirubin toxicity in the auditory system.

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.

Neurobehavioral deficits in premature graduates of intensive care--potential medical and neonatal environmental risk factors

There is growing evidence that a large number of very low birth weight infants are exhibiting neurobehavioral problems in the absence of cerebral palsy at follow-up that has extended into school age and adolescence. Many clinical factors (ie, chronic lung disease, recurrent apnea and bradycardia, transient hypothyroxemia of prematurity, hyperbilirubinemia, nutritional deficiencies, glucocorticoid exposure), as well as stressful environmental conditions, including infant-provider interaction, constant noise, and bright light, may act in combination to impact on the developing brain, even in the absence of overt hemorrhage and/or ischemia. Any potential intervention strategy designed to prevent cognitive and behavioral problems has to account for the numerous biological and clinical conditions and/or interventions, as well as postdischarge social and environmental influences.

Bilirubin and the auditory system

The auditory system is highly sensitive to bilirubin toxicity. Damage to the auditory nervous system includes auditory neuropathy or auditory dyssynchrony and auditory processing problems which may occur with or without deafness, hearing loss. Auditory dysfunction may occur in children with or without other signs of classical kernicterus. Bilirubin selectively damages the brainstem auditory nuclei, and may also damage the auditory nerve and spiral ganglion containing cell bodies of primary auditory neurons. The inner ear, thalamic and cortical auditory pathways appear to be spared. Noninvasive auditory neurophysiological tests such as the auditory brainstem response (ABR) or brainstem auditory response (BAER) play an important role in the early detection of bilirubin-induced auditory and central nervous system dysfunction in the neonate.

Bilirubin and serial auditory brainstem responses in premature infants

OBJECTIVES

To determine the usefulness of the bilirubin-albumin (B:A) molar ratio (MR) and unbound bilirubin (UB) as compared with serum total bilirubin (TB) in predicting bilirubin encephalopathy as assessed by auditory brainstem responses (ABR) in infants of 28 to 32 weeks' gestational age.

STUDY DESIGN

During a 2-year period, serial ABRs were obtained on 143 infants of 28 to 32 weeks' gestational age during the first postnatal week. Waveforms were categorized on the basis of response replicability and the presence of waves III and V. Wave V latencies were also serially analyzed when measurable for individual infants. Maturation of the ABR was defined as abnormal when the waveform category worsened and/or latency increased during the study interval. Serum albumin was analyzed at 48 to 72 hours of age in all patients. Serum TB was analyzed as clinically indicated. Aliquots of the same samples were also analyzed for UB in a subset of infants.

RESULTS

The mean peak TB concentration (10.1 +/- 1.7 mg/dL) for the 71 infants with normal ABR maturation was not significantly different from the mean peak TB (10.2 +/- 2.1 mg/dL) in the 24-hour period preceding the ABR's first showing abnormal maturation in the other 55 infants. However, in infants with UB analyzed, the mean peak UB (0.62 +/- 0.20 vs 0.40 +/- 0.15 microg/dL) was significantly higher in the infants with abnormal maturation (n = 25) than in infants with normal maturation (n = 20). The B:A MR results were equivocal. In the entire study population, there was no difference in B:A MR between infants with normal versus abnormal ABR maturation. However, in the subset of infants in whom UB was measured, although TB was not different, there was a significant difference in B:A MR. Based on receiver-operating characteristic curves, a UB level of 0.5 microg/dL was the best discriminator with a sensitivity of 70% and a specificity of 75%. The proportion of infants who had UB >0.5 microg/dL and UB </=0.5 microg/dL and who had abnormal ABR, maturation was 0.81 and 0.33, respectively, with a significant difference in the incidence of transient bilirubin encephalopathy among these 2 groups. The relative risk of abnormal ABR maturation with UB >0.5 microg/dL compared with UB </=0.05 microg/dL was 2.45 (95% confidence interval: 1.33-4.49).

CONCLUSIONS

UB is a more sensitive predictor than either serum bilirubin or B:A MR of abnormal ABR maturation, and hence transient bilirubin encephalopathy in premature newborns with hyperbilirubinemia.

Sensorineural hearing loss and prematurity

OBJECTIVE

To elucidate clinical antecedents of sensorineural hearing loss (SNHL) in very preterm infants.

DESIGN

Case-control study.

SUBJECTS

Fifteen children < 33 weeks' gestation with significant SNHL born between 1 January 1990 and 31 December 1994, detected within 9 months of birth, and 30 matched control children.

METHODOLOGY

Perinatal variables in the two groups were compared using non-parametric tests and conditional logistic regression (EGRET).

RESULTS

Median birth weight for the index group was 960 g (range 600-2914 g) compared with 1026 g (range 410-2814 g) for controls. Children with SNHL had longer periods of intubation, ventilation, oxygen treatment, and acidosis, and more frequent treatment with dopamine or frusemide. Neither peak nor trough aminoglycoside levels, nor duration of jaundice or level of bilirubin varied between groups. However, SNHL was more likely if peak bilirubin levels coexisted with netilmicin use (odds ratio (95% confidence interval) 14.2 (1.8 to 113.6)) or if acidosis occurred when bilirubin levels were over 200 micromol/l (OR 8.0 (0.9 to 71.6). Frusemide use in the face of high serum creatinine levels (OR 8.9 (1.1 to 74.5)) or netilmicin treatment (OR 5.0 (0.99 to 24.8)) was also associated with SNHL. At 12 months of age, seven of 15 children with SNHL had evidence of cerebral palsy compared with two of 30 controls (OR 12.3 (2.1 to 71)).

CONCLUSIONS

Preterm children with SNHL required more intensive care in the perinatal period and developed more neurological complications than controls. Among very preterm babies, the coexistence of risk factors for hearing loss may be more important than the individual factors themselves.

Otoacoustic emissions and auditory brainstem responses after neonatal hyperbilirubinemia

Severe hyperbilirubinemia often results in hearing loss. Behavioral audiometry, auditory-evoked brainstem responses (ABRs) and otoacoustic emissions (OAEs) were performed in three such patients in an attempt to localize the pathophysiology of this hearing loss. Behavioral audiometric findings in these patients (all male, 4, 15 and 25 years old) ranged from severe in the 4-year-old, moderate in the 15-year-old and slight in the 25-year-old. Where obtained, ABR wave V thresholds were elevated or ABR were absent. However, absolute and inter-wave latency measurements were not indicative of brainstem pathology. OAEs (transient and distortion product) could only be obtained in the high- or low-frequency ranges in these patients. Our findings suggest that at least some lesions producing hearing loss in severe hyperbilirubinemia are in the cochlea, especially at the outer hair cells. Finally, we found that only moderately elevated serum bilirubin levels (<20 mg/dl) may contribute to the development of sensorineural hearing loss.

Neonatal screening for hearing disorders in infants at risk: incidence, risk factors, and follow-up

OBJECTIVE

To determine the incidence and risk factors for hearing disorders in a selected group of neonates and the feasibility of selective hearing screening.

SETTINGS

Multicenter prospective trial at five centers in Germany.

METHODS

Enrollment criteria: in addition to previously defined risk factors by the Joint Committee on Infant Hearing (family history of hearing loss, in utero infections, craniofacial anomalies, birth weight <1500 g, critical hyperbilirubinemia, ototoxic medications, bacterial meningitis, postnatal asphyxia, mechanical ventilation >5 days, stigmata, or syndromes associated with hearing loss), the impact of maternal drug abuse, birth weight <10th percentile, persistent pulmonary hypertension, and intracranial hemorrhage more than or equal to grade III or periventricular leukomalacia on infant hearing were evaluated. The screening procedure was performed by automated auditory brainstem response (A-ABR; ALGO 1-plus; Natus Med Inc, San Carlos, CA).

STATISTICS

univariate analyses of risk factors versus A-ABR results and a multivariate regression analysis were used; additionally, the total test time was recorded.

RESULTS

Seven hundred seventy recordings from 777 infants enrolled consecutively constitute the basis of this analysis. Mean gestational age was 33.8 +/- 4.3 weeks, birth weight 2141 +/- 968 g; 431 infants being male and 339 female; 41 (5.3%) infants exhibited pathologic A-ABR results (16 bilateral and 25 unilateral). Meningitis or sepsis, craniofacial malformations, and familial hearing loss were independent significant risk factors. Median total test time was 25 minutes. Follow-up examinations in 31 infants revealed persistent hearing loss in 18 infants (13 infants sensorineural, 5 from mixed disorders), 7 requiring amplification.

CONCLUSION

Hearing screening in high-risk neonates revealed a total of 5% of infants with pathologic A-ABR (bilateral 2%). Significant risk factors were familial hearing loss, bacterial infections, and craniofacial abnormalities. Other perinatal complications did not significantly influence screening results indicating improved perinatal handling in a neonatal population at risk for hearing disorders.

Etiology of hearing loss in children. Nongenetic causes

Every child with a hearing loss should have an evaluation to determine the cause of hearing loss. This article focuses on the nongenetic origins of hearing loss, the most frequent of which is the neonatal intensive care unit experience, followed by meningitis, cytomegalovirus, and other infections. Preventable causes such as exposure to ototoxic medications and noise are also discussed in this article.

Hearing screening in at-risk neonate cohort

OBJECTIVE

This prospective study reports on the prevalence of hearing impairment in an at-risk neonatal intensive care unit (NICU) population.

DESIGN

From 1990 to 1997, 942 neonates were screened with transient evoked otoacoustic emissions (TEOAE) and brainstem evoked response audiometry (BERA).

RESULTS

835 Infants passed the primary screen for both ears, 57 for one ear, adding up to 94.7%. Seventeen infants (1.9%) were lost to follow-up. In thirteen infants (1.4%), bilateral hearing impairment above 30 dB was confirmed. While all children with hearing impairment belonged to the group of 820 children receiving aminoglycosides, only one presented no other risk factors. In 11 of the hearing impaired children other anamnestic factors, i.e. dysmorphism, prenatal rubella or cytomegaly, family history of hearing loss or severe peri- and postnatal complications seem to be more probable causes of the identified hearing loss.

CONCLUSIONS

From our data, aminoglycosides seem not to be an important risk factor for communication related hearing impairment, when serum levels are continuously monitored, as occurred in our cohort. After adjustment for other risk factors, birth weight between 1000 and 1500 g and a gestational age between 29 and 31 weeks were no predictive markers for hearing impairment. It might be speculated that the improved medical treatment in a Neonatal Intensive Care Unit (NICU) reduces the probability of hearing impairment for those two groups. Conductive hearing loss as a possible additional cause for hearing impairment was not studied in detail, but the high percentage of malformations detected (four out of 13 hearing impaired infants) demands further monitoring, close follow-up, counselling and adequate treatment.

Lack of deafness in Crigler-Najjar syndrome type 1: a patient survey

We performed a questionnaire survey about 42 patients with Crigler-Najjar syndrome type 1 who were currently alive. Information was obtained on their age, sex, birth weight, gestation, parental consanguinity, other family members affected, age of onset of jaundice, neonatal and postneonatal bilirubin values, neonatal and postneonatal therapy, problems faced with phototherapy, liver transplantation, current growth status, current neurologic status, and the status of hearing. Patients were between 2 months and 21 years of age. There were 18 males and 24 females. Thirty-nine patients had been born at full term gestation and 3 had been preterm. Jaundice was noted on postnatal day 1 in 34%, between days 2 and 4 in 55%, and after day 11 of life in 11% of patients. In the neonatal period bilirubin values (mean +/- SD) were typically 19.8 +/- 4.5 mg/dL. Eighty-six percent of patients had neonatal peak bilirubin values of >20 mg/dL. Parental consanguinity was present in 44% and a history of Gilbert's disease in one parent was present in 10% of patients. Causes of exacerbations of jaundice reported were respiratory infections, febrile illnesses, vaccinations, fasting, surgery, emotional stress, and noncompliance with treatment. Neonatal therapy consisted of exchange transfusion in 28%, phototherapy in 79%, phenobarbitone in 20%, and cholestyramine, albumin, infusions, and plasmapheresis in one case each. The mainstay of postneonatal therapy was home phototherapy for 10 to 16 hours, primarily at night during sleep, using blue lights or a combination of blue and fluorescent lights. Some patients used innovatively designed phototherapy units. Problems reported with phototherapy were decreased effectiveness with age, poor compliance, restriction of activity and play, inability to travel or take vacations, irritation from eye shades, difficulty keeping eye protection on, difficulties in temperature maintenance, tanning of the skin, embarrassment from the need to be nearly nude during phototherapy, and difficulty in procuring phototherapy lamps. Other therapies that had been tried included oral agar, albumin infusions, antioxidants, acupuncture, bilirubin oxidase, calcium infusions, clofibrate, cruciferous vegetables, cholestyramine, chlorpromazine, flumecinol, plasmapheresis, tin mesoporphyrin, ursodeoxycholic acid, and urinary alkalinization. Fifteen children had undergone liver transplantation (5 auxiliary and 10 orthotopic). All 42 patients are reportedly of normal height and weight. Neurodevelopmental status is said to be normal in 77% of patients. Two patients have kernicterus, 4 have cerebellar symptoms, and 1 each has developmental delay, mild intention tremor, and mild speech delay. Hearing was reported to be normal in 94% of patients. The 2 children with hearing loss have conductive loss from otitis media. With home phototherapy prolonged, survival free of neurologic deficits is possible in Crigler-Najjar syndrome type 1, but there are many problems associated with phototherapy. Avoiding exacerbations of jaundice is an important aspect of management. Liver transplantation offers the prospect of cure but its risk versus benefit ratio is undetermined. Hearing loss was absent in the patients surveyed despite prolonged exposure to high bilirubin levels, which suggests that bilirubin may not be as ototoxic as is commonly believed.

Effect of hearing impairment on educational outcomes and employment up to the age of 25 years in northern Finland

The association between hearing impairment in adolescence and school performance and the outcome of education was studied among 25-year-old subjects followed since pregnancy in the Northern Finland birth cohort. The series, 395 subjects with abnormal hearing and 977 randomly selected controls, was based on a questionnaire on hearing and school achievement sent to 11780 members of the cohort alive at the age of 14 years, and on audiometric screening test requested from health centers. Hearing loss was defined as 'clinically significant' if the pure tone average (PTA; mean of the thresholds at 0.5, 1 and 2 kHz) exceeded 25 dB in the better ear; a threshold of > or = 30 dB at 4 kHz and a PTA of < or = 25 dB as '4 kHz loss'; and as 'slightly abnormal' if any of the thresholds exceeded 20 dB at any frequency and the case did not belong to the above two categories. The more severe the hearing impairment, the poorer was the child's performance at elementary school. Those with normal hearing and those with a slightly abnormal or 4 kHz loss were equally often accepted for intermediate education (88%), while those with a clinically significant loss had the lowest acceptance figures (64%). When adjusting for neurological and social confounders, excluding mental disability, the risk of not qualifying from intermediate or higher education at all was twice as high among those with a clinically significant loss as among the controls (OR 2.1, 95% CI 1.13-3.8), and was still elevated after adjustment had been made for all the relevant perinatal, neurological and social factors (OR 1.9, 95% CI 1.02-3.6). 14% of those with a clinically significant hearing loss, 9% of the subjects with a 4 kHz loss and 7% of those with normal hearing were unemployed at the age of 25 years. Hearing impairment appears to have effects on both the outcome of education and employment status.

Developmental patterns of heart rate and variability in prematurely-born infants with apnea of prematurity

At equivalent post-conceptional ages, prematurely-born infants have higher heart rates and reduced heart rate variability, relative to full-term neonates. Premature birth might exert long-lasting effects on central and peripheral mechanisms that control cardiovascular activity. We assessed development of heart rate and heart rate variability in symptomatic preterm infants up to 6 months of age. Fifty 6.5-h evening recordings of EKG and breathing were obtained from prematurely-born infants (gestational ages: 24-35 weeks). Cardiac R-R intervals were captured with a resolution of +/- 0.5 msec. One-min epochs were selected from three periods of regular respiration in recordings from premature infants and 72 recordings of full-term infants at comparable post-conceptional ages. Mean heart rate and heart rate variability were determined for each recording. At 40 weeks post-conception, prematurely-born infants with apnea of prematurity showed higher heart rates and reduced heart rate variability than did full-term neonates. These differences between premature and full-term infants persisted throughout the next 6 months in those infants born prior to 30 weeks gestation, and in those infants born at 30-35 weeks who experienced respiratory distress syndrome (RDS) during the neonatal period. The findings suggest that premature delivery, or complications thereof, exerts long-lasting effects on cardiac control.

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.