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Hearing threshold as measured by auditory brain stem response in human neonates
1Children's Auditory Research & Evaluation Center, House Ear Institute, Los Angeles, California, USA.
Ear and Hearing
|October 1, 1996
Summary
Neonatal auditory brain stem response (ABR) thresholds are higher than adult thresholds, particularly for high-frequency sounds. This immaturity in hearing development is likely due to conductive and neural factors.
Area of Science:
- Audiology
- Neuroscience
- Developmental Pediatrics
Background:
- Assessing auditory threshold in neonates presents unique challenges.
- Auditory brain stem response (ABR) is a common method for evaluating infant hearing.
- Existing research shows variations in neonatal ABR thresholds compared to adults.
Purpose of the Study:
- To evaluate the concept of auditory threshold in human neonates.
- To compare adult and neonatal ABR thresholds using tonal stimuli.
- To discuss the advantages and limitations of ABR in assessing neonatal hearing.
Main Methods:
- Comparison of data from several studies on neonatal ABR thresholds.
- Authors' study involved 2-channel ABR recordings in neonates and adults.
- Tone burst stimuli (0.5, 1.5, 4, 8 kHz) calibrated using probe-tube microphones.
Main Results:
- Neonatal ABR thresholds were elevated by 5-25 dB compared to adult thresholds across tested frequencies.
- Higher frequency stimuli (4, 8 kHz) showed the greatest threshold elevation in neonates.
- Lower frequency stimuli (0.5 kHz) demonstrated more mature auditory responses in neonates.
Conclusions:
- Neonatal auditory thresholds, measured by ABR, are immature, especially at high frequencies.
- Accurate stimulus calibration is crucial for reliable cross-age comparisons.
- Developmental differences in the auditory system's conductive mechanisms and neural pathways explain elevated neonatal ABR thresholds.