Pedaudiologic findings after severe neonatal hyperbilirubinemia

Neonatal hyperbilirubinemia (NHB) above 20 mg/dl (NHB20) has been shown to increase the risk of hearing impairments. Up to now, audiological findings based on behavioural audiometry (BA), otoacoustic emissions (TEOAE) and auditory brainstem responses (ABR) from children after being diagnosed with NHB20 have not been thoroughly compared to those with lower NHB-levels. We, therefore, aimed to assess the presence and characteristics of auditory dysfunction in children with NHB20. The audiological data of 15 children aged 11 months to 9 years with a NHB level between 22.6 and 45.6 mg/dl and/or MRI-confirmed bilirubin encephalopathy (NHBG) were compared retrospectively to 15 children with NHB levels between 12.5 and 19.4 mg/dl (CG). After matching by weeks of gestation at birth, BA, TEOAE and ABR were performed in all the children. Subsequently the groups were compared. Only two children of the NHBG had consistently normal audiologic findings. Hearing function disorders were detected in 87% (13/15) of the NHBG-children, ranging from total deafness to normal BA, including unilateral and bilateral deafness as well as cochlear hearing loss. Auditory neuropathy/dys-synchrony (AN) was found in a total of eight children (53%) of the NHBG. In addition, it was found that after the occurrence of NHB20, initially detected TEOAE can disappear in some cases. In the comparison group (CG) only two children demonstrated a hearing dysfunction, both of which were cochlear hearing impairments, whereas no child had AN. A bias towards hearing impairments has to be taken into account for both groups. Detailed pedaudiologic testing should be mandatory for all children after the occurrence of NHB20 including follow-up during the first 12 months. Audiological diagnostic work-up in the affected children requires objective investigations of hearing functions, while BA is recommended to evaluate the adequate therapeutic procedure.