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The functional status of the auditory nerve and brainstem auditory sensory pathway can be evaluated effectively and non-invasively using BERA. The awareness state, medications, and a range of contextual circumstances do not...
The functional status of the auditory nerve and brainstem auditory sensory pathway can be evaluated effectively and non-invasively using BERA. The awareness state, medications, and a range of contextual circumstances do not appreciably modify it .
The BERA alterations in response to hyperbilirubinemia include loss of one or more I-V wave peaks, a raised threshold, an increase in wave I, III, or V delay, or a larger inter-peak interval .
It's important to note that BERA Test can identify subclinical bilirubin encephalopathy even in the absence of any kernicterus symptoms or signs.
Early bilirubin reducing therapies can correct the acute alterations found in BERA, which explains why bilirubin encephalopathy is transitory. However, a persistent increase in bilirubin can result in neuronal degeneration and long-lasting changes to BERA.
Procedure for conducting bera test
The auditory nerve and later components in the auditory brainstem circuits are what cause BERA. Moller and Janetta provide details about the places where each wave component of BERA came from.
Wave I It is an image of the complex action potential in the distal end of cranial nerve VIII. As the cranial nerve VIII fibres leave the cochlea and enter the internal auditory canal, they are thought to be the source of the response.
Two Waves In the brainstem, it is produced by the proximal VIII nerve.
Cochlear nucleus, a second order neuron, was the primary source of wave III.
4th Wave It comes from a third order pontine neuron. primarily found in the superior olivary nucleus, but the cochlear nucleus and the nucleus of the lateral lemniscus may also contribute.
Wave V generation is a reflection of the activity of many anatomical auditory processes. The lateral lemniscus is where wave V's sharp positive peak emerges from, while the inferior colliculus is where wave V's gradual negative wave indicates dendritic potential.
In the therapeutic use of the BERA Brainstem Evoked Response Audiometry , Wave V is the component that is most frequently studied.
VI and VII waves These waves seem to originate in the medial geniculate body or the inferior colliculus.
Methodology for Bera Test
Preparation of skin
Electrolyte gel that is non-staining and non-irritating to skin was applied after the skin was prepped using an abrasive skin preparatory paste that is free of acetone and chloride.
Electrode placement
Using a double channel, four electrode montage system, silver electrodes were used and applied in the manner described below.
- Right mastoid—+ve
- Left mastoid—ve
- Forehead—neutral
- Vertex—+ve
Machine setting
Using an insert ear phone, click acoustic stimuli were delivered to each ear at a rate of 20–40 clicks per second with polarity rarefaction at intensities ranging from 90 to 30 dBnHL. The filter setting ranged from 30-3,000 Hz, and the time frame was 15 ms. The normal threshold was defined as the existence of wave V at 30 dBnHL in intensity.
BERA measures taken into account for diagnosis were
- I-V at 90 dBnHL peak loss at one or more locations
- A higher threshold
- Wave peaks I, III, and V's absolute latencies
- Amount of time between the peaks of I-III, III-V, and I-V
