Tone-burst elicited auditory brainstem responses in full-term and pre-term infants.

OBJECTIVE: To investigate the reliability of tone-burst auditory brainstem response (TB-ABR) latencies and thresholds in pre-term and full-term infants.

DESIGN: TB-ABRs to 500 Hz and 4000 Hz tone-burst stimuli were recorded at two-week intervals over the first six weeks of life in a group of full-term infants (40-46 weeks gestational age [GA]) and over ten weeks (36-46 weeks gestation) in a group of preterm infants. Linear mixed model analyses evaluated within-subject changes and the effects of the subject group, age at assessment, and stimulus frequency on ABR latency and threshold.

STUDY SAMPLE: Twenty-four infants participated. Nine were full-term (GA: 39-41 weeks) and fifteen were healthy pre-term (GA: 28-34 weeks) at birth.

RESULTS: TB-ABR wave V latencies at 70 dBnHL decreased throughout the study ( p  < 0.001) in pre-term babies for both test frequencies by approximately 0.5 ms. There were, however, no group or GA (at birth) effects indicating that response latency normalized in these children by the due date. Similarly, TB-ABR threshold levels in the premature group were elevated ( p  = 0.001) by approximately 5 dB in pre-term evaluation but were equivalent to those of full-term participants in the post-term assessment period.

CONCLUSIONS: In healthy, pre-term infants, tone-burst ABR testing is reliable from 36 weeks gestation.