Hearing Evaluation in Children (continued)

• limited, poor, or no speech
• frequently inattentive
• difficulty learning
• often increases the volume on the TV
• fails to respond to conversation-level speech or answers inappropriately to speech

Types of Hearing Loss

Conductive hearing loss is caused by an interference in the transmission of sound to the inner ear. Infants and young children frequently develop conductive hearing loss due to ear infections. This loss is usually mild, temporary, and treatable with medicine or surgery.

Sensorineural hearing loss involves malformation, dysfunction, or damage to the inner ear (cochlea) and is rarely due to problems with the auditory cortex of the brain. The most common type is cochlear hearing loss and this may involve a specific part of the cochlea (inner hair cells or outer hair cells or both). It usually exists at birth. It may be hereditary or may be caused by a number of medical problems, but sometimes the cause is unknown. This type of hearing loss is usually permanent.

The degree of sensorineural hearing loss can be mild, moderate, severe, or profound. Sometimes the loss is progressive (hearing gradually becomes poorer) and sometimes unilateral (one ear only).

Because the hearing loss may be progressive, repeat audiologic testing should be done. Sensorineural hearing loss is generally not reversible medically or surgically, but children with this type of hearing loss often can be helped with hearing aids.

A mixed hearing loss occurs when both conductive and sensorineural hearing loss are present.

A central hearing loss involves the hearing areas of the brain, which may show as difficulty "processing" speech and other auditory information. This is often referred to as "auditory processing disorder" and may be misdiagnosed as a behavioral disorder.

How Hearing Is Tested

Several methods can be used to test a child's hearing, depending on the child's age, development, or health status.

Behavioral tests involve careful observation of a child's behavioral response to sounds like calibrated speech and pure tones. Pure tones are the distinct pitches (frequencies) of sounds. Sometimes other calibrated signals are used to obtain frequency information.

The behavioral response might be an infant's eye movements, a head-turn by a toddler, placement of a game piece by a preschooler, or a hand-raise by a gradeschooler. Speech responses may involve picture identification of a word or repeating words at soft or comfortable levels. Very young children are capable of a number of behavioral tests.

Physiologic Tests

Physiologic tests are not hearing tests but are measures that can partially estimate hearing function. They're used for kids who can't be tested behaviorally (due to young age, developmental delay, or other medical conditions) and sometimes can help find which function of the auditory system is at fault.

Auditory brainstem response (ABR) test

For this test, tiny earphones are placed in the ear canals and small electrodes (which look like small stickers) are placed behind the ears and on the forehead. Usually, click-type sounds are introduced through the earphones, and the electrodes measure the hearing nerve's response to the sounds. A computer averages these responses and displays waveforms. An infant may be sleeping naturally or may have to be sedated for this test. Older cooperative kids may be tested in a silent environment while they're visually occupied.