Children Hearing Evaluation

Children Hearing assessment is avilable at Karnataka ENT Hospital and Research Center(R).

Auditory brainstem response (ABR)

The automated auditory brainstem response (ABR) 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 programs.

Evoked otoacoustic emissions (OAE)

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 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.

Limitations of ABR and OAE tests

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.

Conditioned oriented responses (CORs) or visual reinforced audiometry (VRA)

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.

Play audiometry

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.

Conventional screening audiometry

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 (i.e., 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.