Infant and Children's Hearing Testing
I. General Information
Audiologists test infants and children using specialized test procedures
designed to take advantage of age appropriate behaviors and measure the
responses to sound accordingly. Tests that do not require patient responses,
and rely solely on objective test results, allow the audiologist to estimate
auditory sensitivity of the peripheral auditory mechanism of infants and
young children who cannot respond subjectively. The normal development of
speech and language in children depends on the presence of normal hearing.
Without normal hearing a child's receptive and expressive language skills
will typically be absent, delayed, or otherwise poorly established. Between
birth and thirty-six months of age, the miracle of human communication develops
at an explosive rate. Therefore, identification of hearing loss at a very
young age is critical.
II. Specific Test
Procedures
A. Conditioned Orientation Response Audiometry (CORA)
CORA testing is a rudimentary test procedure used to estimate
hearing thresholds of infants and very young children who cannot be tested
subjectively using standard hearing test procedures. A child is placed in
a sound booth in the parent's lap, or on the floor facing the parent, and
subsequent warbled pure tones and other sounds are presented through opposing
loudspeakers in the sound room. The objective of this testing is to identify
the lowest levels which the child responds to various sounds and compare
those to other infants and children of similar age. This test procedure
is often aided by using lighted toys to help condition the child to the
sounds presented through the loudspeakers. Most children respond to this
test procedure favorably and the audiologist can determine quite accurately
how well the child hears.
B. Conditioned Play
Audiometry
Conditioned Play Audiometry is used to assess children three
to six years of age under headphones using playful strategies to condition
the child to respond to warbled tones at various frequencies. This is usually
done in close proximity to the child using portable test equipment in the
sound treated room. Test results from this procedure are also very accurate,
diagnostically significant and, more importantly, ear specific.
C. Brainstem Auditory
Evoked Response (BAER)
BAER testing is a non-invasive electrophysiologic, objective
test of peripheral auditory sensitivity and function. This test procedure
is accomplished under headphones with a sleeping or mildly sedated child.
This objective test is used if other forms of hearing loss identification
are unsuccessful. This test procedure uses a series of clicks and or tone
pips to help estimate peripheral auditory sensitivity at various test frequencies,
usually the higher frequencies. This test requires the patient to recline
and relax with little or no movement. Any sort of muscle movement, especially
in the head and neck, will adversely affect the test results. Therefore,
many times mild sedation of a child is required to obtain results. Sedated
BAER testing should only be attempted in a hospital type setting where the
child can be monitored by hospital nursing staff.
D. Otoacoustic Emission
Testing (OAE)
OAE testing is one of the most advanced, fast and accurate
means of assessing infant and children's hearing abilities. OAE testing
which was initially developed in England, and can most simply be defined
as an auditory echo resonating from the internal auditory system which is
measured using very sophisticated equipment. OAE test equipment averages
and filters out biological noise and allows the audiologist to identify
the actual otoacoustic emission waveform.
OAE testing is accomplished by simply inserting a rubber
ear plug into the infant or child's ear canal which directs the auditory
stimulus into the external auditory canal. The incorporated microphone in
the ear plug picks up the resultant auditory emission from the external
auditory canal. Presence of a robust otoacoustic emission indicates the
child most likely has normal auditory sensitivity and, at most, has a very
mild hearing loss which should not affect normal speech-language development.
Consequently, absence of the otoacoustic emission indicates that the child
has minimally a mild hearing loss and this hearing loss can and will affect
speech/language development if left untreated. The total test time averages
as little as thirty seconds per ear, and as long as two minutes per ear,
with a cooperative child. Finally, the cost of OAE is very in expensive
when compared to BAER testing and is covered by most major insurance companies.
III. Effects
of Hearing Loss on Childhood Language and Learning Development
It has been well documented that children who suffer from chronic
hearing loss as infants and young children, between the ages of 0 and three
years, are at higher risk for language and learning disabilities. Chronic
middle-ear infections and undiagnosed sensory hearing loss can have detrimental
effects on a child's language and learning development. Furthermore, central
auditory processing disorders have been found to be related to chronic ear
infections and coincidental hearing loss, especially noted in infants and
young children. Therefore, it is critical that infants and children who
are at risk for hearing loss be assessed by an audiologist to determine
the child's hearing abilities. Audiologists are best qualified to assess
the pediatric population and have the necessary knowledge and equipment
to accurately diagnose pediatric hearing loss.