Abstract
Background/Aim: Perinatal hypoxia-ischaemia (HI) is one of the major risk factors of acquired sensorineural hearing impairment in infants. So far, little is known about which frequencies on the audiogram of the cochlea in newborn infants are highly susceptible to perinatal HI. By measuring distortion product otoacoustic emissions (DPOAEs), this study aimed to identify the frequencies that are impaired in neonates after HI.
Methods: The subjects were 46 term neonates who suffered perinatal HI (5 min Apgar score ≥7 and clinical evidence of HI). Normal controls were 35 healthy term neonates without problems. DPOAE was elicited by two pure tones (f 1 and f 2; f 2/ f 1 = 1.22) presented simultaneously, with the lower frequency primary tone (f 1) at 65 dB SPL and the higher frequency primary tone (f 2) at 55 dB SPL. The f 2 primary tone was presented at 10 frequencies between 0.5 and 10 kHz. In individual subjects, a testing result that 6 or more out of the 10 frequencies passed the criteria was classified as a total pass. Both the left and right ears were tested. DPOAE was measured on day 3–5 after birth. One month later, all neonates after HI who had normal acoustic impedance (n = 41, 82 ears), and the normal controls who failed in the first DPOA testing were re-tested.
Results: On day 3–5 after birth, the pass rates across the frequencies, mainly 1–5 kHz, in the neonates after HI were all lower than in the controls. The total pass rate was 77.2% (71/92 ears), compared with 95.7% (67/70 ears) in the controls. The patterns of 2 f 1− f 2 DPOAE amplitudes at different frequencies in both the neonates after HI and the controls were generally similar to those of the pass rates, with a ‘dip' at the frequencies 750 Hz and 1 kHz. The difference in the patterns between the two groups was also similar to that in the pass rates. One month later, all the 3 ears which did not pass the first DPOAE testing in the controls passed the re-test. Of the 92 ears in neonates after HI, 80 had Type A tympanogram, and the remaining had Type B (n= 2) or Type As/C (n= 10), suggesting middle ear disorders. The DPOAE pass rates in the 80 neonates with Type A tympanogram tended to decrease slightly further at all frequencies. The total pass rate also decreased further to 62.5%.
Conclusions: The neonatal cochlea, mainly at the frequency range of 1–5 kHz, was impaired after perinatal HI. One month later, the impairment did not show any improvement. The findings may have important implication to early intervention. Follow-up study is needed to detect any permanent frequency-specific impairment.
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Jiang, Z., Zhang, Z. & Wilkinson, A. 120 Frequency-Specific Hearing Impairment in Neonates After Perinatal Hypoxia-Ischaemia. Pediatr Res 56, 484 (2004). https://doi.org/10.1203/00006450-200409000-00143
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DOI: https://doi.org/10.1203/00006450-200409000-00143