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.
  1. Investigation of choice for audiometric evaluation of an infant is BERA
  2. Best screening test to evaluate hearing in a neonate is Otoacoustic Emission.
  3. 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.
  4. 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.
Exam Question
  • Investigation of choice for audiometric evaluation of an infant is BERA.
  • Best screening test to evaluate hearing in a neonate is Otoacoustic Emission.
  • Wave II in BERA originates from Proximal eighth nerve.

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