Auditory Brainstem Evoked Potential (ABEP) Test
An auditory brainstem evoked potential (ABEP) test, also known as brainstem auditory evoked response (BAER) or evoked response audiometry, is performed to measure the brain wave activity that occurs as a response to certain sounds. The test detects sensorineural hearing loss. Electrical activity in the cochlea, a part of the internal ear, and the auditory pathways in the brain is detected by this test. This electrical activity is similar to that of the heart detected by an ECG (electrocardiography). The waveform produced in response to the stimuli consists of a series of peak numbers with roman numerals. The initial peak I is produced by the cochlea and the later peaks are produced by the brain.
The ABEP test is specially designed to make testing of hearing in a newborn smooth and straightforward. The test results do not differ,irrespective of the number of babies tested per day. This test diagnoses nervous system abnormalities and hearing loss, specifically in low birth weight newborns. The test also assesses the neurological functions of newborns. The test can also be performed to gauge the severity of conditions such as acoustic neuroma, sensorineural hearing loss, or central pontine myelinolysis.
The patient is made to lie still on a table or reclining chair. Electrodes are connected to the scalp and both earlobes. Brief sounds (usually clicking sounds) are produced, which are heard by the patient through earphones. The response of the patient's brain to these sounds in the form of electrical activity is picked up by each of the electrodes and is recorded.
If the recorded electrical activity falls within the normal range, it means that sounds are getting transmitted normally from the ear to the brain, which means that the newborn's hearing capacity is not affected in any way. The normal range varies, depending upon the type of instrument used and its calibration. Abnormal results of an ABEP test are mostly indicative of hearing loss that could be a result of cerebrovascular stroke, multiple sclerosis, or some other organic brain disease. It means that the nerves that form the auditory area of the brain are not functioning prperly. A deaf ear does not respond at all to the sound stimulus; therefore, only a flat line is seen, i.e., devoid of any waveforms.
There are no risks involved in an ABEP test. There may be a little discomfort experienced during or after the test. ABEP is more cost-effective as compared to an MRI (magnetic resonance imaging). However, an MRI can provide additional important information. If the patient is suffering from a cold or ear infection, the results of the test may get affected. The person to be tested should avoid getting exposed to loud noise for at least 16 hours prior to the test in order to obtain accurate test results. Movement of the body may also interfere with the results of the test.
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