BERA Test or Brainstem Evoked Response Audiometry or ABR test or BAER test or ASSR test is a type of test which traces the electrical impulse traveling in the brain in response to a sound stimulus. This is used for testing hearing for very small children, difficult to test patients, Malingering cases of hearing, and for neuro diagnosis.
Since Little babies can't tell if they have listened to these sounds, we can tell only after seeing their response to sounds but these are not very reliable sometimes, then these electrical tests become handy.
Very small babies are made to sleep with oral sedation. Three surface electrodes are used to capture electrical waves. One is on the forehead (Ground Electrode), the second is behind the pinna and the third is on the vertex of the head.
when we study the waves, then a total of seven peaks are observed on electrical waveforms.
The most important wave in the middle is the fifth wave or V wave.
These seven waves follow a definite pattern and these waves have been originated in the cochlea by converting mechanical sound waves into an electrical wave that travels via the VIIIth cranial nerve into many centers of the brainstem to finally approach the auditory cortex in the brain.
I don't wish to go into technical details or terms and just wish to keep this video simple for laymen to understand.
so, the pattern of these waves tells us that the patient is responding to sound stimulus.
Normally, the stimulus is started at 70 dB and it is a wide click stimulus at a frequency of 11-25 clicks per second and it is decreased or increased at an interval of 10 dB.
And the level at which wave V stops appearing is known as the hearing threshold.
whatever threshold value, we get, the corrected hearing decibel is within 10 dB of this value.
So, the BERA test is very important. There are many other applications of the BERA test.
There are many disorders in the body like in Neurology, take for example Epilepsy, Most of the time, Epilepsy have normal MRI. another example, Migraine, where MRI and Electrical tests may be normal,
But in Epilepsy, EEG may show some waveform disturbance responsible for the involuntary rhythmic movement of body parts and neurologists can make a diagnosis on basis of EEG.
Like this, ECG for the heart may detect Atrial Fibrillation (an Electrical disorder of the heart, where the heartbeat in a random way very fast).
But in the ear, waves are produced in the brain in response to a sound stimulus.
by studying these waves, we can tell whether there is a lesion in these auditory pathways or not.
There is another group of diseases, where a patient's MRI, Audiometry, or even otoacoustic emissions are normal yet the patient is not able to hear.
these are cases where the problem is in the Auditory or VIII nerve or higher and this disorder of hearing is known as Auditory Neuropathy. These cases are best diagnosed with help of the BERA test.
I hope that you would have liked this small quick information about the BERA test.
Thank you.
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Timestamps
00:00 Introduction
00:53 Procedure during BERA test
01:10 Study of Waveforms
03:20 Auditory Neuropathy