Failure to detect children with congenital or acquired hearing loss may result in lifelong deficits in speech and language acquisition, poor academic performance, personal-social maladjustment, and emotional difficulties. Physicians need to be able to recognize children who are at risk of congenital or acquired hearing loss, be prepared to evaluate their hearing and, if needed, arrange for proper referral and treatment. To assist them, the American Academy of Pediatrics (AAP) recently released screening recommendations for assessing hearing loss in children of all ages. The report was published in the February 2003 issue of Pediatrics and also is available atwww.aap.org.
Significant hearing loss is present in one to six per 1,000 newborns, but some cases of congenital hearing loss may not become evident until childhood. Leading causes of acquired hearing loss include infectious diseases, especially meningitis and otitis media, trauma to the nervous system, damaging noise levels, and ototoxic drugs. Certain physical findings, historical events, and developmental conditions, including but not limited to anomalies of the ear and other craniofacial structures, significant perinatal events, and global developmental or speech-language delays also may indicate a potential hearing problem. Any child with at least one of the high-risk indicators in Table 1 should be screened periodically for late-onset congenital or acquired hearing loss.
According to the AAP, physicians should seriously consider a parent's concern that a child cannot hear and perform a formal hearing evaluation. Parents often report suspicion of hearing loss, inattention, or erratic response to sound before hearing loss is confirmed. In fact, parental concern has been found to be of greater predictive value than the informal behavioral examination performed in the physician's office.
A thorough physical examination is essential in the evaluation of 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, abnormalities of the eardrum, dimpling or skin tags around the auricle, cleft lip or palate, asymmetry of the facial structures, and microcephaly. Hypertelorism and abnormal pigmentation of the skin, hair, or eyes, which is seen in Waardenburg's syndrome, also may be associated with hearing loss.
|Birth to 28 days||Family history of SNHL, presumably congenital|
|In utero infection associated with SNHL (e.g., toxoplasmosis, rubella, cytomegalovirus, herpes, syphilis)|
|Ear and other craniofacial abnormalities|
|Hyperbilirubinemia at levels requiring exchange transfusion|
|Birth weight less than 1,500 g|
|Low Apgar scores: 0 to 3 at five minutes; 0 to 6 at 10 minutes|
|Respiratory distress (e.g., meconium aspiration)|
|Prolonged mechanical ventilation for more than 10 days|
|Ototoxic medication (e.g., gentamicin) administered for more than five days or used in combination with loop diuretics|
|Physical features or other stigmata associated with a syndrome known to include SNHL (e.g., Down syndrome, Waardenburg's syndrome)|
|29 days to 24 months||Parental or caregiver concern about hearing, speech or language, and/or developmental delay|
|Any of the newborn risk factors listed above|
|Recurrent or persistent otitis media with effusion for at least three months|
|Head trauma with fracture of temporal bone|
|Childhood infectious disease associated with SNHL (e.g., meningitis, mumps, measles)|
|Neurodegenerative disorders (e.g., Hunter syndrome) or demyelinating diseases (e.g., Friedreich's ataxia, Charcot-Marie-Tooth syndrome)|
Temporary hearing loss has been demonstrated during episodes of acute otitis media with effusion. Any child with repeated or chronic otitis media should undergo a hearing evaluation. Pneumatic otoscopy and tympanometry are useful diagnostic tools for managing otitis media with effusion.
Objective Screening Tools
Universal hearing screening should be performed in all newborns. In addition, objective screenings for hearing impairment should be performed periodically on all infants and children, according to the schedule outlined in the AAP statement, “Recommendations for Preventive Pediatric Health Care” (available atwww.aap.org/policy/re9939.html). Age-specific audiologic tests are outlined in Table 2.
The automated auditory brainstem response (ABR) is one objective means of evaluating hearing. It is currently used in many newborn-screening programs, but can be used in children of any age. The instrument is automated and provides a pass-fail report; no test interpretation by an audiologist is required. Because motion artifact interferes with test results, ABR is best performed in infants and children who are sleeping or, if necessary, sedated.
Evoked otoacoustic emissions (OAE) is another objective test for hearing loss and can be performed in children of all ages. While motion artifact does interfere with test results, children do not need to be sleeping or sedated. Although OAE is an effective screening tool for inner and middle ear abnormalities, it does not quantify hearing loss or hearing threshold levels. Because it does not assess the integrity of the neural transmission of sound from the eighth nerve to the brainstem, it will miss auditory neuropathy and other neuronal abnormalities. Children with such abnormalities will have normal OAE test results, but abnormal ABR test results.
Even if ABR or OAE test results are normal, hearing cannot be definitively considered normal until a reliable behavioral audiogram can be obtained. Behavioral pure tone audiometry remains the standard for hearing evaluation. It can determine hearing thresholds at specific frequencies as well as the degree of hearing impairment.
Children as young as nine to 12 months of age can be screened using conditioned oriented responses or visual reinforced audiometry. Both of these techniques condition the child to associate speech or frequency-specific sound with a stimulus such as a lighted toy or dancing animal. Visual reinforced audiometry usually is performed by an audiologist.
Children from two to four years of age are tested more appropriately using play audiometry. They are conditioned to respond to an auditory stimulus by, for example, dropping a block when a sound is heard through earphones.
Conventional screening audiometry can be used for children four years and older. Children are asked to raise their right or left hand when they hear a sound in the respective ear. Because ambient noise can affect test performance, especially at lower frequencies (i.e., 500 and 1,000 Hz), audiometry should be performed in a quiet environment using earphones. According to the AAP, each ear should be tested at 500, 1,000, 2,000, and 4,000 Hz. Air conduction hearing thresholds greater than 20 dB at any of these frequencies indicate possible impairment. Evidence of hearing loss should be substantiated by repeat screening. Before re-testing, the AAP recommends removing and repositioning earphones and carefully repeating the instructions to the child to ensure proper understanding and attention. A child whose repeat test shows hearing thresholds greater than 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. The results of hearing screening and ear examinations should be explained carefully to parents, and the child's chart should be marked clearly to facilitate tracking of referrals, developmental skills, and school performance.
Physicians should familiarize themselves with local referral resources for hearing impaired children. According to the AAP, pediatric otolaryngologists, audiologists, and speech and language pathologists with special training and experience caring for children should be consulted for diagnosis, counseling, and treatment, if needed. Communication among professionals is essential to ensure appropriate management of the hearing impaired child.