[Hair cell function diagram in premature and mature newborn infants]

The grade of maturation of the cochlear function must be taken into account when the cochlear function is investigated in premature infants and neonates. Quantitative analysis has not yet been performed.

Using the otodynamic analyzer ILO 88/92, we therefore determined haircell functional diagrams and the echo 65 dB levels in 35 healthy neonates 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 were performed in 10 neonates and 16 premature infants.

The mean echo 65 dB levels were 4.88 +/- 4.22 dB for the right ears and 5.72 +/- 5.16 dB for the left ears in premature infants < or = 32 weeks of GA, 10.25 +/- 3.89 dB and 10.69 +/- 5.55 dB respectively 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 between neonates at day 2 and 4 post natum. In 16 premature infants the echo 65 dB 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 the age of 4 weeks.

We present therefore strong evidence for a maturation of the cochlear function in premature infants with increasing age. The individual grade of maturation of the cochlea is of relevance for the auditive stimulation of very premature infants.