Am Fam Physician. 2007;75(9):1349-1352
Author disclosure: Nothing to disclose.
Congenital hearing loss is estimated to affect one in every 1,000 newborns. Causes of hearing loss can be conductive, sensorineural, mixed, or central. Known risk factors for congenital hearing loss include cytomegalovirus infection and premature birth necessitating a stay in the neonatal intensive care unit. However, up to 42 percent of profoundly hearing-impaired children will be missed using only risk-based screening. Universal newborn hearing screening is a way to identify hearing-impaired newborns with or without risk factors. Newborns with positive screening tests should be referred for definitive testing and intervention services. Whether early intervention in hearing-impaired children identified with universal screening improves language and communication skills has not been established by good-quality studies. However, universal screening has been endorsed by most national children's health organizations because of the ease of administering the screening tests and the ability to identify children who may need early intervention.
During the 2002–2003 school year, nearly 72,000 children in the United States received special services for hearing impairment.1 The incidence of congenital hearing loss (i.e., hearing loss present at birth) is estimated to be one out of every 1,000 live births; however, emerging data from states with universal screening indicate that the incidence may be closer to two or three per 1,000 live births.2
If congenital hearing loss is not recognized and managed, a child's speech, language, and cognitive development are often severely delayed.3
|Clinical recommendation||Evidence rating||References|
|Universal newborn hearing screening should be used to accurately diagnose moderate to severe sensorineural hearing loss.||C||7|
|Children with risk factors for hearing loss who have a negative hearing screen at birth should undergo audiologic testing every six months until three years of age.||C||7,17,19|
|Identification of hearing loss before six months of age improves language development and communication skills.||B||9,15|
Etiology of Hearing Loss
There are four types of hearing loss: conductive, sensorineural, mixed, and central.2 Conductive losses are caused by a problem with the outer or middle ear and usually affect all frequencies to the same degree. Sensorineural loss is caused by problems in the inner ear or auditory nerve. Mixed losses involve both conductive and sensorineural etiologies. Central hearing losses are rare and are caused by problems along the auditory pathway or in the brain itself.2
More than 50 percent of hearing impairment in children is thought to be genetic and not related to infectious, anatomic, or other noninherited causes.4 Cytomegalovirus infects about 1 percent of all newborns in the United States. Annually, between 6,000 and 8,000 infected newborns will have clinical manifestations, and 75 percent of these infants will develop sensorineural hearing loss.4 Table 14 lists various causes of congenital hearing loss.
|Anomalies of the pinna, external ear canal, tympanic membrane, or ossicles|
|Genetic*: isolated impairment or syndromes (e.g., Waardenburg's syndrome [autosomal dominant], Usher's syndrome [autosomal recessive], Alport's syndrome [sex-linked disorder], Turner's syndrome [chromosomal abnormality])|
|Infectious (e.g., cytomegalovirus, syphilis, herpesvirus, rubella, toxoplasmosis, group B streptococcal sepsis, streptococcal virus)|
Risk Factor–Based Screening Is Not Enough
An admission to the neonatal intensive care unit (NICU) for more than two days increases the likelihood of the presence of hearing impairment 10-fold.5 Early screening programs focused on children with known risks.6 Table 2 lists risk factors for hearing impairment in newborns.7,8 However, recent studies indicate that 19 to 42 percent of profoundly hearing-impaired children will be missed with targeted, risk factor–based screening.9
|Craniofacial anomalies, including abnormalities of the pinna and ear canal|
|Family history of hereditary childhood sensorineural hearing loss|
|Neonatal intensive care unit admission for more than two days|
|Rubella or other fetal infection (e.g., herpes, cytomegalovirus)|
|Syndromes associated with hearing loss (e.g., Usher's syndrome, Waardenburg's syndrome)|
Rationale for Universal Screening
Data from cohort studies indicate that diagnosis and intervention before six months of age can improve language and speech acquisition in hearing-impaired children.9–11 However, in children who are not screened at birth, diagnosis of hearing loss may be delayed by as long as three years.13 Lowering the age at which screening and intervention services are initiated may improve language, cognitive, and social outcomes in hearing-impaired children.14
No prospective studies have compared outcomes of children who received screening through a universal newborn hearing screening program and those who were managed using a risk factor–based approach. Consequently, the U.S. Preventive Services Task Force found insufficient evidence to recommend for or against universal newborn hearing screening in the immediate newborn period.15
Despite the lack of high-quality evidence, in 1993 the National Institutes of Health Consensus Development Conference on Early Identification of Hearing Impairment in Infants and Children recommended universal newborn screening.16 The Joint Committee on Infant Hearing issued similar guidelines in 1995 and again in 2000.7,17 Universal newborn hearing screening is also recommended by the American Academy of Pediatrics, by the Centers for Disease Control and Prevention, and in Healthy People 2010.7,18
Children with risk factors should be screened not only at birth but also throughout childhood. The Joint Committee on Infant Hearing recommends continued surveillance of these children because they may be at risk of progressive hearing loss.7,17 This recommendation includes audiologic testing every six months until three years of age.19 In low-risk children, a repeat hearing screening is recommended before entry into kindergarten.
Evaluation of hearing should include a demonstration of a behavior in response to a measured stimulus; this cannot be reliably performed on a child younger than eight to nine months.9 Tests for infants include automated auditory brainstem response (AABR) and the transient evoked otoacoustic emissions (TEOAE) test.
AUTOMATED AUDITORY BRAINSTEM RESPONSE
AABR tests the auditory pathway from the external ear to the lower brainstem. The newborn's ears are covered with earphones that emit a series of soft clicks. Electrodes on the infant's forehead and neck measure brain wave activity in response to the clicks. A computer then compares the brain wave activity with normal response templates and provides a pass or refer (i.e., fail) report.5
TRANSIENT EVOKED OTOACOUSTIC EMISSIONS
The TEOAE test evaluates the function of the peripheral auditory system, primarily the cochlea, which is the area most often involved in sensorineural hearing loss. Normally the cochlear hair cells generate “echoes” when presented with sound waves. The TEOAE test measures these echoes by placing a small microphone in the external ear canal and testing the response to a series of clicks. As with AABR, a computer-generated report compares the newborn's response to standardized emission norms and provides a pass or refer report.5
AABR and TEOAE have been shown to accurately diagnose moderate to profound sensorineural hearing loss in newborns. The sensitivity and specificity measured against an independent benchmark were 84 and 90 percent, respectively.9 Children with a positive result should be referred for definitive testing and evaluation, including a detailed family history for genetic causes.7 Using these devices, a universal newborn hearing screening program has been shown to reduce by eight months the average age at which hearing-impaired children receive hearing aids (i.e., to about six months of age).14 There currently is no evidence to support either AABR or TEOAE as the preferred method of screening newborns.7
Drawbacks of Universal Newborn Hearing Screening
Universal newborn hearing screening produces a large number of false-positive test results. Both AABR and TEOAE can be influenced by motion artifact and therefore are more specific if performed on a sleeping child in a quiet room. The rate of false positives ranges from more than 30 percent for one-step programs using TEOAE20 to less than 1 percent with a two-step process, such as retesting a child before discharge if the initial test is positive.21
Despite these concerns, the consensus of multiple organizations that develop children's health guidelines is that the potential benefits of universal newborn hearing screening outweigh its adverse effects.7 Currently, 37 states and the District of Columbia have enacted legislation requiring that hearing screening be performed on all newborns in hospitals and birthing centers (Table 3).24 Additional resources for physicians and patients are provided in Table 4.
|National Center on Birth Defects and Developmental Disabilities|
|National Dissemination Center for Children with Disabilities|
|National Institute on Deafness and Other Communication Disorders|