Development of tone-pip auditory brainstem responses and auditory steady-state responses in infants aged 0-6 months.

CONCLUSIONS

The longitudinal findings presented in this study suggest that with the maturational development, the conduction time of the auditory nerve decreases while the thresholds had no physiological changes within 0-6 months after birth. Comparing the tone-pip auditory brainstem response (ABR) with the auditory steady-state response (ASSR), the former had lower thresholds than the latter at 500-8000 Hz, which indicates that the estimation of tone-pip ABR maybe nearer to the actual hearing level of infants.

OBJECTIVE

To evaluate the feasibility of tone-pip ABR and ASSR for newborns and infants, and to follow the development of the threshold estimates from tone-pip ABR and ASSR in normal infants through the first 6 months of life.

METHODS

The tone-pip ABR and ASSR thresholds were measured at octave frequencies from 250 to 8000 Hz bilaterally in 80 infants aged 0-6 months with normal hearing.

RESULTS

For click ABR at 70 dB nHL, the absolute and inter-peak wave latencies decreased as the age increased. The tone-pip ABR had similar waveforms to the click ABR, its wave latencies decreased and the waveforms improved as the age and frequency increased. On average, the thresholds of tone-pip ABR and ASSR were observed at 1.2-41.2 dB nHL (SD = 2.6-8.0 dB) and 16.9-43.0 dB nHL (SD = 2.5-8.0 dB), respectively, at 250-8000 Hz in infants aged 0-6 months, but there were no physiological differences. Tone-pip ABR thresholds were significantly lower than those for ASSR except at 250 Hz (p < 0.05). Both ASSR and ABR had stable and similar audiograms in the different groups.