Auditory brainstem responses (ABR) in high-risk neonates.

In the present study, auditory brainstem responses (ABR) were recorded in 60 high-risk neonates in the intensive care unit selected by the following criteria: Birth-weight less than 2000 g, hyperbilirubinemia requiring phototherapy or exchange transfusion, idiopathic respiratory distress syndrome, artificial ventilation, asphyxia, sepsis or meningitis, intracranial haemorrhage, neurological symptoms and potential ototoxic medication (aminoglycoides, furosemide). The infants tested ranged in gestational age from 27-44 weeks. The ABR testing was performed in a sound-proof room using the Madsen (ERA-74) equipment. Four infants did not reveal responses to 70 dB HL ("nonresponders"), and the total of 10 neonates (16.6%) had abnormal ABR-tests, when the physiological changes related to gestational age and conceptional age (gestational age plus the age after birth) were taken into account. The 10 neonates with abnormal tests were reexamined after discharge, and in six there were no improvement of threshold sensitivity. three of the "nonresponders" were retested several times within the two years after birth (one died at age 18 months of pertussis), and none of them revealed ABR at stimulus intensity of 70 dB HL. They all attend an audiological training program started at age of six months as a consequence of the early diagnosis of impaired auditory function. It is our opinion that a routine ABR-evaluation should be performed on high risk neonates (criteria mentioned above) in the newborn intensive care unit. Retesting of infants with abnormal responses within three months, and several times within the next two years if abnormal responses persist, is important. Transient impairment of auditory functions is not uncommon in these infants. However, the children with persisting hearing impairment should be discovered early to attend an early audiological training program.