Hearing Assessment in Infants and Children: Recommendations Beyond Neonatal Screening

RISK INDICATORS FOR HEARING LOSS

Significant hearing loss is present in 1 to 6 per 1000 newborns.⁵ Most children with congenital hearing loss have hearing impairment at birth and are potentially identifiable by newborn and infant hearing screening. However, some congenital hearing loss may not become evident until later in childhood. Hearing impairment also can be acquired during infancy or childhood for various reasons. Infectious diseases, especially meningitis and otitis media, are leading causes of acquired hearing loss. Trauma to the nervous system, damaging noise levels, and ototoxic drugs can all place a child at risk of developing acquired hearing loss.^6,7 Certain physical findings, historical events, and developmental conditions may indicate a potential hearing problem. These include but are not limited to anomalies of the ear and other craniofacial structures, significant perinatal events, and global developmental or speech-language delays. All older infants and children should be screened for risk factors involving hearing problems. A summary of high-risk indicators for hearing loss and speech-language-auditory milestones are included in Tables 1 and 2, respectively. Every child found to have 1 or more of the high-risk indicators in Table 1 should be followed and periodically screened for late-onset congenital or acquired hearing loss.

Although questionnaires and checklists are useful in identifying a child at risk for hearing loss, studies have shown that only 50% of children with hearing loss are identified by the comprehensive use of such questionnaires.^8,9 Therefore, periodic objective assessment of the hearing of all children should be performed.

If a parent or caregiver is concerned that a child cannot hear, the pediatrician needs to assume that such is true until the child has been evaluated objectively. Parental concern is of greater predictive value than the informal behavioral examination performed in the physician’s office. Parents often report suspicion of hearing loss, inattention, or erratic response to sound before hearing loss is confirmed.^10,11 One study showed parents were as much as 12 months ahead of physicians in identifying their child’s hearing loss.³ Any parental concern should be taken seriously, and formal hearing evaluation should be performed.

PHYSICAL EXAMINATION

A thorough physical examination is an essential part of evaluating a child for hearing loss. Findings on head and neck examination associated with hearing impairment include heterochromia of the irises, malformation of the auricle or ear canal, dimpling or skin tags around the auricle, cleft lip or palate, asymmetry or hypoplasia of the facial structures, and microcephaly.¹² Hypertelorism and abnormal pigmentation of the skin, hair, or eyes also may be associated with hearing loss, as in Waardenburg syndrome. Abnormalities of the eardrum should alert the physician to the possibility of hearing impairment. A leading cause of acquired hearing impairment is otitis media with effusion (OME). Temporary hearing loss has been demonstrated during episodes of acute otitis media. The child with repeated or chronic OME is at high risk of acquired hearing impairment and should undergo hearing evaluation.¹³ Pediatricians should be familiar with pneumatic otoscopy and tympanometry as useful diagnostic tools in the management of OME.

TOOLS FOR OBJECTIVE HEARING SCREENING

In addition to universal newborn hearing screening, objective screenings for hearing impairment should be performed periodically on all infants and children in accordance with the schedule outlined in the AAP statement, “Recommendations for Preventive Pediatric Health Care.”⁴ The technology used for hearing screening should be age appropriate. The child also should be comfortable with the testing situation; young children may need preparation. Screenings should be conducted in a quiet area where visual and auditory distractions are minimal. Various audiologic tests are outlined in Table 3.

One objective means of evaluating hearing is the automated auditory brainstem response (ABR). This instrument measures ABRs at frequencies greater than 1000 Hz with a broadband click stimulus in each ear. The testing instrument incorporates a built-in artifact rejection for myogenic, electrical, and environmental noise interference, which ensures that data collection is halted if testing conditions are unfavorable. The automated screener provides a pass-fail report; no test interpretation by an audiologist is required. Automated ABR can test each ear individually and can be performed on children of any age. Motion artifact interferes with test results. For this reason, the test is performed best in infants and young children while they are sleeping or, if necessary, sedated. The ABR is currently used in many newborn screening programs.

Evoked otoacoustic emissions (OAE) are acoustic signals generated from within the cochlea that travel in a reverse direction through the middle ear space and tympanic membrane out to the ear canal. These signals are generated in response to clicks or tone bursts. The signals may be detected with a very sensitive microphone/probe system placed in the external ear canal. The OAE test allows for individual ear assessment, is performed quickly at any age, and is not dependent on whether the child is asleep or awake. Motion artifact does interfere with test results. The OAE is an effective screening measure for inner and middle ear abnormalities, because at hearing thresholds of 30 dB or higher, there is no OAE response. The OAE test does not further quantify hearing loss or hearing threshold level. The OAE also does not assess the integrity of the neural transmission of sound from the eighth nerve to the brainstem and, therefore, will miss auditory neuropathy and other neuronal abnormalities. Infants with such abnormalities will have normal OAE test results but abnormal ABR test results.

The ABR and OAE are tests of auditory pathway structural integrity but are not true tests of hearing. Even if ABR or OAE test results are normal, hearing cannot be definitively considered normal until a child is mature enough for a reliable behavioral audiogram to be obtained. Behavioral pure tone audiometry remains the standard for hearing evaluation. Hearing thresholds at specific frequencies can be determined and the degree of hearing impairment can be assigned. If there are distractions or the room is not soundproof, pure tone audiometry in the office should be considered solely a screening test.

Children as young as 9 to 12 months can be screened by means of conditioned oriented responses (CORs) or visual reinforced audiometry (VRA). Both of these techniques condition the child to associate speech or frequency-specific sound with a reinforcement stimulus, such as a lighted toy or dancing animal. The VRA is a more sophisticated and accurate form of COR requiring a soundproof room and is typically performed by an audiologist.

Children 2 to 4 years of age are tested more appropriately by play audiometry. These children are conditioned to respond to an auditory stimulus through play activities, such as dropping a block when a sound is heard through earphones.

For children 4 years and older, conventional screening audiometry can be used. The child is asked to raise the right or left hand when a sound is heard in the respective ear. The test should be performed in a quiet environment using earphones, because ambient noise can affect test performance significantly, especially at lower frequencies (ie, 500 and 1000 Hz). Each ear should be tested at 500, 1000, 2000, and 4000 Hz. Air conduction hearing threshold levels of >20 dB at any of these frequencies indicate possible impairment.

Audiometric evidence of hearing loss should be substantiated by repeat screening. Earphones should be removed and repositioned, and instructions should be carefully repeated to the child to ensure proper understanding and attention to the test. A child whose repeat test shows hearing thresholds >20 dB at any of these frequencies, especially if there is no pathologic abnormality of the middle ear on physical examination, should be referred for formal hearing testing. Children with unilateral or mild hearing loss also should be further evaluated; studies show such children to be similarly at risk for adverse communication skills as well as difficulties with social, emotional, and educational development.¹⁴

The results of hearing screening and ear examinations should be explained carefully to parents. The child’s chart should be marked clearly to facilitate tracking of appropriate referrals, developmental skills, and school performance.

HEARING REFERRAL RESOURCES

Pediatricians should be familiar with the referral resources available in their community for hearing impaired children. Pediatric otolaryngologists and audiologists and speech and language pathologists with special training and experience in treating children should be consulted for specific diagnosis, counseling, and treatment. The primary care pediatrician and the otolaryngologist should collaborate to refer the child for comprehensive educational counseling and treatment services. Communication among professionals caring for a hearing-impaired child is essential to ensure appropriate case management.

Committee on Practice and Ambulatory Medicine, 2002–2003

Kyle Yasuda, MD, Chairperson

Lawrence Hammer, MD

Norman Harbaugh, Jr, MD

Philip Itkin, MD

John Jakubec, MD

Robert Walker, MD

Consultant

Edward O. Cox, MD

Liaisons

Adrienne A. Bien

Medical Group Management Association

Todd Davis, MD

Ambulatory Pediatric Association

Winston Price, MD

National Medical Association

Staff

Junelle P. Speller

Section on Otolaryngology/Bronchoesophagology, 2002–2003

Michael J. Cunningham, MD, Chairperson

David H. Darrow, MD, DDS

Mark N. Goldstein, MD

Andrew J. Hotaling, MD

Bruce R. Maddern, MD

Seth M. Pransky, MD

Nina L. Shapiro, MD

Liaison

Anthony E. Magit, MD

American Society of Pediatric Otolaryngologists

Staff

Chelsea L. V. Kirk