Auditory brainstem responses in patients with neonatal hyperbilirubinemia and bilirubin encephalopathy

To understand the neurotoxicity of neonatal hyperbilirubinemia, auditory brainstem response (ABR) studies were performed in 75 jaundiced patients, who were divided into 4 groups in either a retrospective or prospective way. Retrospective ABR study in 10 known kernicteric patients (group I) showed elevation of the hearing threshold and delay of wave I, as well as prolongation of central brainstem transmission, in various degrees, in most cases. Six jaundiced infants (group II) with ABR testing before and after blood exchange transfusion (BET) showed shortening of wave latencies and increase in amplitude after BET. There were additional 20 infants with BET (group III) and 39 with phototherapy (group IV) receiving ABR testing after the therapeutic procedures. Prospective follow-up in groups II, III and IV showed normalization of the ABRs in all except one patient in the following months. These findings demonstrate the nature of bilirubin neurotoxicity and the prognostic value of ABRs in the monitoring of bilirubin toxicity. ABR testing is sensitive in reflecting the effect of hyperbilirubinemia, and provides a valuable guide for the early recognition and close follow-up of bilirubin neurotoxicity.