Ref: Clohertys Manual of Neonatal Care, 6th edition. Page 646 and ENT DhingraExplanation:"ABR is reliable after 34 weeks postnatal age. "Ref: ClohertyBRAINSTEM EVOKED RESPONSE AUDIOMETRY (BERA)Other nameso Auditory brainstem responses (ABR)o Brainstem auditory evoked response (BAER)o Brainstem auditory evoked potential (BAEP).Measures the electroencephalographic waves generated hy the auditory system in response to clicks through three electrodes placed on the infant's scalp.The characteristic waveform recorded from the electrodes becomes better defined with increasing postnatal age.ABR is reliable after 34 weeks postnatal age.At present, because of the increased risk of injury to the auditory pathway beyond the cochlea (auditory nerve) including auditory dyssynchrony, ABR is the preferred screening method to evaluate hearing loss in the NICE graduate.Non-invasive technique to find integrity of central auditory pathways through the 8th cranial nerve, pons and midhrain.Electrical potentials are generated in response to several click stimuli or tone-bursts and picked up from the vertex by surface electrodes.It measures hearing sensitivity in the range of 1000 - 4000 Hz.In normal person. 7 waves are produced in the first 10 milliseconds.The 1st, 3rd and 5th waves are most stable and are used in measurements.Parameters studied in waveforms:o Latencyo Inter-wave latencyo Amplitude.The exact anatomic site of neural generators are:o Wave 1 - Distal part of CN 8.o Wave 2 - Proximal part of CN 8 near the brainstem.o Wave 3 - Cochlear nucleuso Wave 4 - Superior olivary complexo Wave 5 - Lateral lemniscuso Wave 6 & 7 - Inferior colliculus.UsesScreening for hearing in infants.To determine the threshold of hearing in:o Infants.o Children.o Uncooperative adultso Malingerers.To diagnose retroeochlear pathology (e.g.: Acoustic neuroma).To diagnose brainstem pathology (e.g.: Multiple sclerosis or Pontine tumors)To monitor CN 8 intraoperatively in surgery of acoustic neuromas to preserve the function of cochlear nerve.