The key difference between Auditory Brainstem Response (ABR) and Otoacoustic Emissions (OAE) tests lies in what part of the auditory system they assess: ABR measures the nerve and brainstem's response to sound, while OAE measures the function of the outer hair cells in the cochlea.
ABR vs. OAE: A Detailed Comparison
| Feature | Auditory Brainstem Response (ABR) | Otoacoustic Emissions (OAE) |
|---|---|---|
| What it measures | Electrical activity of the auditory nerve and brainstem pathways | Function of the outer hair cells in the cochlea |
| Mechanism | Measures the brain's response to sounds. | Measures sounds produced by the outer hair cells. |
| Level of Assessment | Auditory nerve and brainstem | Cochlea (specifically outer hair cells) |
| Indication | Assessing hearing in infants, diagnosing auditory neuropathy, etc. | Screening hearing in newborns, monitoring ototoxic drug effects |
| Response Type | Electrical signal | Sound |
Further Explanation
-
Auditory Brainstem Response (ABR): This test involves placing electrodes on the scalp to measure the electrical activity generated by the auditory nerve and brainstem in response to sound stimuli presented through earphones. The ABR screening provides information about how well the auditory nerve conducts signals to the brain, identifying potential issues in the neural pathways for hearing. It bypasses the need for a behavioral response from the patient, making it ideal for testing infants or individuals who cannot reliably participate in traditional hearing tests.
-
Otoacoustic Emissions (OAE): This test measures the sounds produced by the outer hair cells in the cochlea. These cells vibrate in response to sound and produce a "echo" that can be measured by a probe placed in the ear canal. OAEs are present when the outer hair cells are functioning normally, and their absence can indicate hearing loss, particularly related to cochlear dysfunction. However, OAEs do not provide information about the auditory nerve or brainstem.
In essence, ABR tells us about the neural pathway for hearing, while OAE tells us about the health of the outer hair cells in the inner ear. These two tests are often used together to provide a comprehensive assessment of hearing function. A normal OAE and an abnormal ABR result can suggest Auditory Neuropathy Spectrum Disorder (ANSD).
