Bera

BERA

• Auditory brainstem response (ABR): Also called BAER or BAEP (brainstem auditory evoked response or potential) or BERA (brainstem evoked response audiometry)
• Elicits brainstem responses to auditory stimulation by clicks or tone bursts.
• It is a non-invasive technique to find the integrity of central auditory pathways through the VIIIth nerve, pons and midbrain.
• It measures hearing sensitivity in the range of 1000-4000 Hz.

WAVES OF BERA

• In auditory brain stem evoked response audiometry, the impulses are generated by the brain stem in the form of waves.

These waves are considered to originate from the following anatomical sites:

1. Distant Cochlear nerve- Wave I
2. Proximal Cochlear Nerve-Wave II
3. Cochlear nucleus – Wave III
4. Superior olivary complex – Wave IV
5. Nulclei of lateral lemniscus – Wave V
6. Inferior colliculus – Wave VI
7. Medial Geniculate Body-Wave VII

• These peaks occur in most readable form in response to click stimuli over a period of 1 – 10 milliseconds after the stimulus in normal hearing adults.
• BERA is resistant to the effects of sleep, sedation, sleep and anesthesia. Its threshold has been found to be within 10dB as elicited by conventional audiometry.

 USES OF BERA 

• As a screening procedure for infants.
• Investigation of choice for audiometric evaluation of an infant is BERA
• Best screening test to evaluate hearing in a neonate is Otoacoustic Emission.
• Most screening programmes for newborn hearing ability uses otoacoustic emission as the initial test. It this test fails then auditory brainstem response is used for screening.
• Otoacoustic emissions (OAEs) are objective, noninvasive, and rapid measures (typically less than 2 minutes) used to determine cochlear outer hair cell function.
• To determine the threshold of hearing in infants; also in children and adults who do not cooperate and in malingerers.
• It is the most reliable audiological method of differentiating between cochlear and Retrocochlear hearing losses
• To diagnose retrocochlear pathology particularly acoustic neuroma.
• To diagnose brainstem pathology, e.g. multiple sclerosis or pontine tumours.
• To monitor CN VIII intraoperatively in surgery of acoustic neuromas to preserve the function of cochlear nerve.