Otoport OAE+ABR
User Manual for Otoport DP+TE model
15
Introduction
1.6
Auditory Brainstem Response
Auditory Brainstem Response (ABR) is an electrophysiological response
that measures the auditory system’s response to sound. Three voltage
sensors (electrodes) are placed on the patient and a sound probe is placed
in the test ear. The equipment sends a click, brief tone, or chirp sound
stimuli to the test ear.
The cochlea (inner ear) converts sound into electrical signal. These signals
travel in sequence to the acoustic nerve, the brainstem, and finally to
the cortical areas of the brain. The electrodes pick up these electrical
responses to the sound which are commonly known as auditory evoked
potentials. A response which occurs within 20ms of the onset of the
stimulus is referred to as an Auditory Brainstem Responses (ABR).
As the amplitude of the ABR is very small compared to the ‘noise’ of other
brain electrical activity (EEG) the ‘signal to noise ratio’ is very poor. It is
enhanced by a process called averaging. The amplitude of the ABR is also
quite small compared to voltages generated by myogenic (muscle) activity;
therefore, ideally, patients should be tested when sleeping or when very
still.
If EEG and myogenic artefacts are below a tolerable (noise reject) level,
the Otoport ABR firmware will detect the ABR and automatically give a
simple Pass/Fail response to the user. Other details of the test including
the ABR waveforms may also be viewed, and results interpreted, manually
if so desired.