Depressed brainstem auditory electrophysiology in preterm infants after perinatal hypoxia-ischaemia

Our understanding of pathophysiology of hypoxic-ischemic brain damage in preterm infants remains very limited. We studied the amplitudes of brainstem auditory evoked response, recorded with 91-910/s clicks, at term in preterm infants after perinatal HI for functional status of the auditory brainstem. Compared with age-matched healthy preterm infants, the preterm infants after HI did not show any major abnormality in waves I and III amplitudes at any click rates. However, wave V amplitude was reduced significantly at 227 (P<0.05), 455 and 910/s (both P<0.01). V/I amplitude ratio was slightly reduced at 455 and 910/s. Compared with normal term infants, waves III amplitude in the preterm infants after HI tended to be reduced at all click rates, and differed significantly the highest rate 910/s (P<0.05). Wave V amplitude was significantly reduced at higher click rates (455 and 910/s, P<0.05 and 0.01). V/I amplitude ratio was slightly reduced at 455 and 910/s. The reduction of wave amplitudes generally became more significant with the increase in click rate. The slopes of III-V interval-rate function, and wave V amplitude-rate function were significantly steeper than in both the healthy preterm infants and the term infants. Thus, the major abnormality in the preterm infants after HI was a significant reduction in wave V amplitude that mainly reflects central auditory or brainstem function. Brainstem auditory electrophysiology is depressed and so brainstem auditory function is impaired in preterm infants after perinatal HI.