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 f(2 )primary tone between 1 and 10 kHz, particularly 1-5 kHz, were all lower than those in normal term controls (X(2 )= 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%, X(2) = 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.

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.