Optimizing parameters for using the parallel auditory brainstem response (pABR) to quickly estimate hearing thresholds

Objectives: Timely assessments are critical to providing early
intervention and better hearing and spoken language outcomes for children
with hearing loss. To facilitate faster diagnostic hearing assessments in
infants, the authors developed the parallel auditory brainstem response
(pABR), which presents randomly timed trains of tone pips at five
frequencies to each ear simultaneously. The pABR yields high-quality
waveforms that are similar to the standard, single-frequency serial ABR
but in a fraction of the recording time. While well-documented for
standard ABRs, it is yet unknown how presentation rate and level interact
to affect responses collected in parallel. Furthermore, the stimuli are
yet to be calibrated to perceptual thresholds. Therefore, this study aimed
to determine the optimal range of parameters for the pABR and to establish
the normative stimulus level correction values for the ABR stimuli.
Design: Two experiments were completed, each with a group of 20 adults (18
– 35 years old) with normal hearing thresholds (≤ 20 dB HL) from 250 to
8000 Hz. First, pABR electroencephalographic (EEG) responses were recorded
for six stimulation rates and two intensities. The changes in component
wave V amplitude and latency were analyzed, as well as the time required
for all responses to reach a criterion signal-to-noise ratio of 0 dB.
Second, behavioral thresholds were measured for pure tones and for the
pABR stimuli at each rate to determine the correction factors that relate
the stimulus level in dB peSPL to perceptual thresholds in dB nHL.
Results: The pABR showed some adaptation with increased stimulation rate.
A wide range of rates yielded robust responses in under 15 minutes, but 40
Hz was the optimal singular presentation rate. Extending the analysis
window to include later components of the response offered further
time-saving advantages for the temporally broader responses to low
frequency tone pips. The perceptual thresholds to pABR stimuli changed
subtly with rate, giving a relatively similar set of correction factors to
convert the level of the pABR stimuli from dB peSPL to dB nHL.
Conclusions: The optimal stimulation rate for the pABR is 40 Hz, but using
multiple rates may prove useful. Perceptual thresholds that subtly change
across rate allow for a testing paradigm that easily transitions between
rates, which may be useful for quickly estimating thresholds for different
configurations of hearing loss. These optimized parameters facilitate
expediency and effectiveness of the pABR to estimate hearing thresholds in
a clinical setting.