Infant Hearing

Milestones of Infant Hearing

After birth, the auditory behavior of infants follows a fairly typical set of developmental stages:

• Birth to three months of age: Begins to localize or turn towards interesting environmental sounds. appears to "listen", pays attention. Awakens more easily to environmental sounds.

• Three to six months of age: Localizes more often and more accurately to environmental sounds. Starts to understand a few words such as no, bye-bye, or so big. Starts to imitate some sounds.

• Six to twelve months of age: Says first meaningful word such as mama or dada. Understands more of what is said.

• Twelve months of age: Starts to learn a greater number of words, starts to understand more of what is said, and starts to put more than one word together in an utterance.

Risk Factors for Hearing Loss

There are several high-risk factors that suggest a newborn to 28 day old may have either a conductive or a sensorineural hearing loss:

• A family history of hereditary childhood sensorineural hearing loss
• An in-utero infection, such as cytomegalovirus, rubella, syphilis, herpes, or toxoplasmosis
• Craniofacial anomalies, including those with morphological abnormalities of the pinna and ear canal
• Birth weight less than 1500 grams (3.3 lbs)
• Hyperbilirubinemia at a level requiring exchange transfusion
• The use of prolonged or multiple courses of ototoxic medications, including but not limited to aminoglycosides -- the use of loop diuretics may potentiate this problem
• Mechanical ventilation lasting five days or longer
• Stigmata or other findings known to be associated with a syndrome that is associated with a sensorineural or conductive hearing loss

Conditions Associated with Hearing Loss

For the older infant (from 29 days through two years of age), the following conditions warrant hearing testing:

• Parent or caregiver concern about hearing, speech, or language development or developmental delay.
• Bacterial meningitis and other infections associated with sensorineural hearing loss.
• Head trauma associated with loss of consciousness or skull fracture.
• Stigmata or other findings associated with a syndrome known to include a sensorineural or conductive hearing loss.
• Ototoxic medications, including but not limited to chemotherapeutic agents or aminoglycosides, used in multiple courses or in combination with loop diuretics.
• Recurrent of persistent otitis media with effusion for at least three months.

At what age can an infant's hearing be tested? At any age! In 1994, a Joint Committee on Infant Hearing Screening issued a position statement recommending universal detection of infants with hearing loss as early as possible and before three months of age. They also recommended that intervention and rehabilitation occur before six months of age. For this to occur effectively, infants should be tested in the newborn nursery or they may never be tested until specific symptoms of hearing loss are observed by parents or care takers.

Prior to a few years ago, newborns in the nursery were chosen for hearing screening based on their inclusion in a high-risk registry for hearing loss (see above). The literature has shown, however, that approximately 50% of infants with significant hearing loss will not be identified by sole use of the high-risk registry. Therefore, a number of states, Virginia included, are starting to mandate that all infants be screened while they still are in the newborn nursery.

In the nursery, infants can be tested either with the brainstem auditory evoked response (BAER) or with otoacoustic emissions. The BAER involves placing several electrodes on the baby's head. The change in electrical activity (EEG) of the brain in response to sound is computer processed while the child is asleep. These procedures are non-invasive and do not hurt even a pre-mature/fragile newborn. It is best to perform either procedure just before discharge from the nursery so as to take advantage of infant maturation.

Please remember that all babies, even pre-mature newborns, can be given a hearing test. It is never too early to test a baby's hearing.