Hair cell function diagrams in premature and mature births

Background: The grade of maturation of the cochlear function must be taken into account when the cochlear function is investigated in premature infant s and neonates. Quantitative analysis has not yet been performed. Methods: Using the otodynamic analyzer ILO 88/92, we therefore determined h aircell functional diagrams and the echo 65 dB levels in 35 healthy neonate s as well as 30 healthy premature infants with a median gestational age (GA ) of 32 weeks (28-35 weeks) 2-3 days post natum. Follow up investigations w ere performed in 10 neonates and 16 premature infants. Results: The mean echo 65 dB levels were 4.88 +/- 4.22 dB for the right ear s and 5.72 +/- 5.16 dB for the left ears in premature infants less than or equal to 32 weeks of CA, 10.25 +/- 3.89 dB and 10.69 +/- 5.55 dB respective ly in premature infants >32 weeks of GA, and 16.01 +/- 4.99 and 14.90 +/- 4 .41 dB respectively in neonates. There was no significant difference betwee n neonates at day 2 and 4 post natum. In 16 premature infants the echo 65 d B levels increased from 4.92 dB for the right ears and 4.79 dB for the left ears at the second day of life to 11.72 dB and 11.73 dB respectively at th e age of 4 weeks. Conclusion: We present therefore strong evidence for a maturation of the co chlear function in premature infants with increasing age. The individual gr ade of maturation of the cochlea is of relevance for the auditive stimulati on of very premature infants.