Distortion product otoacoustic emissions in term infants after hypoxia-ischaemia

Distortion product otoacoustic emissions (DPOAEs) were recorded in 46 term infants who suffered perinatal hypoxia-ischaemia to identify which frequencies in the cochlear audiogram are susceptible to perinatal hypoxia-ischaemia. On days 3–5 after birth, the pass rates across the frequencies of the f2 primary tone between 1 and 10 kHz, particularly 1–5 kHz, were all lower than those in normal term controls (X2 = 7.27–32.30, all P <0.01). Of the 92 ears, 15 (16.3%) failed the DPOAE test, which was significantly higher than in the controls (4.3%, X2 = 5.81, P <0.05). At 1 month, 80 ears with a type A tympanogram were re-tested. The pass rates at most frequencies, mainly 1 and 2 kHz, were slightly further decreased. Thirteen ears (16.2%) failed the DPOAE test. These results suggest that the neonatal cochlea, mainly at the frequencies 1–5 kHz, is impaired shortly after perinatal hypoxia-ischaemia and the impairment remains at 1 month. Conclusion: Perinatal hypoxia-ischaemia impairs the neonatal cochlea mainly at the frequencies 1–5 kHz and the impairment detected on days 3–5 after birth is unlikely to improve in the later neonatal period. These findings may have implications for the management of hearing impairment in infants after perinatal hypoxia-ischaemia.