Indications:

• Nervous system abnormalities
• Children with hearing loss
• To assess neurological functions
• Malingering patients
• Suspected acoustic neuroma
• Central pontine myelinolysis

Bera test Procedure

• The test is done in an air-conditioned room.
• Patient is asked to wash the hair the night before the test.
• Infants and small children need to be administered sedatives like triclofos sodium in a dose of 50 mg per kg of body weight or promethazine hydrochloride in a dose of 0.5mg per kg of body weight so that the child is deeply sedated during the test.

• Electrodes are placed on the patient’s scalp, along the vertex and on each earlobe.
• Patient in lying down position, eyes closed and preferably asleep.
• Earphones are put on the ear. The patient hears a clicking sound between 10 and 40 clicks per second through the earphones.
• The electrodes pick up the brain’s response and record it on the graph.
• It measures hearing sensitivity in the range of 1000–4000 Hz.
• In a normal person, seven waves are produced in the first 10 ms.
• The first, third and fifth waves are most stable and are used in measurements.
• The waves are studied for absolute latency, inter-wave latency (usually between wave I and V) and the amplitude.
• Wave V is the most reliable and easily identifiable wave in the BERA tracing.

Absolute latency:

Wave	Latency (ms)
Wave I	1.55 - 1.75
Wave III	3.8
Wave IV	5.5 - 5.85

Interaural latency:

Parameter measured	Normal value (milliseconds)	Criteria for abnormality (milliseconds)
Interaural latency difference of wave V	Less than 0.3	More than 0.3