Auditory Abnormality in Term Neonates With Different Stages of Hypoxic-Ischemic Encephalopathy.

Objective: This study aims to explore differences in brainstem auditory function shortly after birth between term neonates with different stages of perinatal hypoxic-ischemic encephalopathy (HIE) using brainstem auditory evoked responses.

Method: The responses were recorded and analyzed during the first 8 days after birth in term neonates with HIE. The data were compared between the HIE neonates and normal controls and between the neonates with different stages of HIE.

Results: Compared to normal controls, neonates with HIE, particularly those with Stage 3 HIE, had a significantly elevated response threshold. The response wave latencies were prolonged, and Wave V amplitude was reduced. The response abnormalities were generally more significant with increasing in the HIE stages. The I-V interval was nearly normal in the neonates with Stage 1 HIE but significantly prolonged in those with Stages 2 and 3 HIE. All wave latencies and I-V interval were significantly longer and Wave V amplitude was smaller in the neonates with Stages 2 or 3 HIE than in those with Stage 1 HIE. The neonates with Stage 3 HIE manifested significantly higher response threshold, significantly longer Waves III and V latencies, and moderately longer I-V interval than those with Stage 2 HIE.

Conclusions: Brainstem auditory function is minimally affected by mild HIE but is significantly impaired in moderate and particularly severe HIE during the first 8 days after birth. The impairment tends to be more significant in severe HIE than in moderate HIE. The risk of auditory impairment is significantly increased in moderate and particularly severe HIE.