Evaluation of risk factors for hearing impairment in at risk neonates by brainstem evoked response audiometry (BERA)

Thirteen (19.2%) of 68 at risk neonates in an intensive care nursery with one or more adverse perinatal clinical factors viz; prematurity (less than 37 wks), low birth weight (less than 2000 gm), hyperbilirubinemia requiring active intervention, birth anoxia, neonatal seizures, infections, aminoglycoside administration, and craniofacial malformations; were diagnosed to have hearing impairment (elevated auditory threshold) by BERA testing performed within the first six weeks of life at a mean conceptional (gestational age + age after birth) age of 40.2 +/- 0.6 wks. As against this, 20 healthy term neonates who were examined at a mean conceptional age of 40.4 +/- 0.8 weeks had a normal hearing threshold of 30 db nHL. Elevated auditory threshold was found more frequently in neonates with multiple clinical adverse factors than in those having single risk factor (6/13 Vs 7/55, p less than 0.001). On multiple logistic regression analysis, however, only 2 factors viz; hyperbilirubinemia at level exceeding indication for exchange transfusion and birth weight less than 1500 gm, were found to be significantly correlated with the hearing impairment in the affected neonates and in that order of importance. Prematurity, birth asphyxia, neonatal seizures, infections and aminoglycoside administration had no significant correlation with hearing impairment. Since most of the neonates admitted to the neonatal ICU have one or more identified adverse risk factors, their hearing screening by BERA at the time of discharge seems justified.