BERA

[Brainstem Auditory Evoked Responses]

Definition

BERA also known as Auditory Brainstem Response Audiometry is an electro-physiological test procedure performed in children to check hearing loss or deafness, especially done with newborn infants. This test is done even if adults have a hearing problem.

BERA is a method used to evaluate the functions of ears and lower part of the auditory system in an infant, even before the child develops to a stage whereby hearing problem is identified; it is done as well for adults.

Why it is done

• To evaluate hearing loss in children.
• To analyze new born infants for deafness.
• To analyze if the brain stem response is absent in the affected ear.
• To monitor or observe patients in Intensive care unit.
• To examine Demyelization disorders.
• To monitor nervous system.
• To find Natal infections.
• To find if there is any injuries in brain.
• Low birth weight infants.
• History of Hearing loss (family)
• Hyperbilirubinemia

Procedure

BERA test is actually a painless and safe procedure of brainstem function and auditory pathway which responds to the click or tone pips stimuli.

The test begins by generating or creating a stimulus in the form of click or tone pips from a headphone which is transmitted through a transducer that is placed in the headphone.

The impulse waves which are generated at the brainstem level are measured by the elicited neuronal action potentials of the electrodes which are placed typically over the vertex of the scalp and ear lobes. Along with this, an earthing electrode is also placed on the forehead, which helps in proper functioning of preamplifier.

Note: [As the electrodes are placed on the head, the patients should be advised to take a shampoo bath, so that the hairs are oil free.]

The signal in the micro-voltage is charted and averaged against the millisecond (time). BERA identifies cases of acoustic schwannoma as it has 90% sensitivity and 80% specificity, which increases in proportion with the size of tumor.

Result

• This test is completely very safe to perform.
• It does not have any side effects.
• It is immune to the effects of sedation and anesthesia, as its threshold is within 10dB as interpreted by the audiometry.
• This can be, routinely performed in newborns. It is important to test the hearing so that we can ensure that at least one ear is functioning normally. If this can be confirmed, then there is no urgency in treating the abnormal ear as regards hearing.