Normative Values for Auditory Brainstem Responses and Wave V Thresholds in Indian Neonates and Infants

Click-evoked auditory-brainstem-response (ABR) is widely used for hearing screening in neonates and infants. However, their normative values are based on small studies. This retrospective study was done at a tertiary-care centre where click-ABR based screening is done in all newborns. ABR records (Nihon-Kohden machine, model MEB-9400K) of 420 healthy neonates (preterm 75; full-term 32) and infants (113) done over a period 4 years (2014-2018) were analysed retrospectively. Sick neonates and those with Wave V threshold > 40 dbnHL were excluded. Infants were divided into four groups based on post-conceptual age, Group A (75): 34-36 weeks; Group B (44): 37-40weeks; Group C (188):41 weeks-1 month; and Group D (113): 1-6months. The mean absolute latencies for wave I, wave III, and wave V varied from 1.45-1.56 milliseconds (ms), 4.14-4.37 ms, and 6.36-6.81 ms respectively. Interpeak latencies for I-V and I-III varied from 4.91 ms to 5.22 ms and 2.69 ms to 2.81 ms respectively. Older infants had lower absolute and interpeak latencies. Late preterm babies were not different from term babies suggesting early maturation of brainstem pathways.