386 Section IX ■ Miscellaneous Procedures

2. Automated auditory brainstem response (AABR): Also a

noninvasive screening tool that records auditory brainstem responses and compares them to a template representing typical results in neonates. Occlusive earphones

cover the ears and emit sound stimuli into the ear canal.

Electrodes are placed on the head and nape of neck to

detect electrical activity from the auditory nerve and

brainstem in response to the sound stimuli. A computer

registers samples of the electrical activity over a fixed

period of time. The averaged responses are then compared to a normal newborn template to determine if the

result is a “pass” or a “refer” for each ear. Figure 54.2

shows an infant undergoing AABR screening. In addition to assessing middle ear and cochlear activity, this

test evaluates the function of the auditory nerve and

auditory brainstem.

3. Auditory brainstem response (ABR) also referred to as

brainstem auditory evoked response (BAER): Not typically used as the initial hearing screen tool, BAER is a

diagnostic test used to predict type and severity of hearing loss. BAER testing is conducted after a failed screening measurement. Auditory brainstem responses are

determined in each ear for both click and tone stimuli.

These sounds are presented by air (earphone) as well as

bone conduction. Severity of hearing loss is expressed

in decibels and described as conductive, sensorineural,

or mixed.