BACKGROUND: Whether hyperbilirubinemia suppresses electrophysiological activity 
of the neonatal auditory brainstem remains to be investigated.
AIM: To determine whether hyperbilirubinemia suppresses the brainstem auditory 
electrophysiology in term neonates.
METHODS: Maximum length sequence brainstem auditory evoked response (MLS BAER) 
was recorded shortly after confirming hyperbilirubinemia in 58 term neonates. 
Wave amplitudes of the response were analyzed in detail.
RESULTS: Compared with age-matched term controls, the neonates with 
hyperbilirubinemia showed a significant reduction in the amplitudes of MLS BAER 
waves III and particularly V at all click rates 91-910/s. The reduction tended 
to be more significant at higher than lower rates. Wave I amplitude was reduced 
at 910/s. V/I amplitude ratio was decreased at all click rates. Therefore, the 
amplitudes of MLS BAER, particularly later, waves were all reduced. The 
amplitudes of all MLS BAER waves tended to be reduced with the increase in total 
serum bilirubin level. All wave amplitudes were correlated with the level of 
total serum bilirubin at some or most click rates.
CONCLUSIONS: Brainstem auditory electrophysiology is suppressed in neonates with 
hyperbilirubinemia, which related to the severity of hyperbilirubinemia. Wave 
amplitudes are valuable BAER variables to detect functional impairment of the 
brainstem and auditory pathway in neonatal hyperbilirubinemia, and are 
recommended to be used in assessing bilirubin neurotoxicity to the neonatal 
brain.