Brainstem auditory-evoked responses. Normal variation as a function of stimulus and subject characteristics

Area of Science:

• Neuroscience
• Audiology
• Biomedical Engineering

Background:

• Brainstem auditory-evoked responses (BAERs) are crucial for assessing auditory pathway function.
• Variability in BAERs can complicate neurological diagnosis.
• Stimulus parameters are known to influence BAERs, but their full impact is not always recognized.

Purpose of the Study:

• To investigate the effects of acoustic phase, stimulus intensity, and click rate on BAER interpeak latencies (IPLs).
• To identify previously unrecognized interactions between stimulus parameters.
• To highlight how controlling methodological variability can improve BAER test sensitivity and specificity.

Main Methods:

• BAERs were recorded from 64 normal adults and 77 normal neonates.
• Stimuli included broadband clicks (rarefaction/condensation) at 30-70 dB sensation levels.
• Testing was performed at click rates of 10 and 80 clicks per second.

Main Results:

• Beyond known rate effects, acoustic phase and stimulus intensity significantly affected BAER IPLs.
• A significant interaction was observed among acoustic phase, stimulus intensity, and click rate.
• Stimulus characteristics, age, and sex were found to account for substantial inter- and intrasubject variability in BAER IPLs and morphology.

Conclusions:

• Unrecognized stimulus parameter effects and their interactions contribute to BAER variability.
• Clinical applications of BAER can be enhanced by recognizing and controlling these methodological sources of variability.
• Improved understanding of stimulus effects will increase the sensitivity and specificity of BAER for neurological diagnosis.