Background
The Narrow-Band (NB) chirp stimuli induce a slightly wider stimulation of the basilar membrane around the 0.5, 1, 2, and 4 kHz frequencies, providing a closer auditory brainstem response (ABR) threshold to the behavioral one as compared to click-evoked ABR. Data regarding absolute and predicted hearing thresholds using NB chirp-ABR are lacking. This work aims to evaluate the absolute and predicted hearing thresholds measured by NB chirp stimuli and to find the relationship between the electrophysiologic and behavioral hearing thresholds in adults with different degrees of sensorineural hearing loss (SNHL).
Method
An observational, case-control study was conducted on 50 adults with normal hearing (control group) and 50 adults with mild to profound SNHL (study group). Both groups were matched in age and gender. All participants were evaluated for their history, basic audiological evaluation, and NB chirp-ABR assessment.
Results
The main NB chirp-ABR measures showed significantly longer latency, smaller amplitude, and lower mean electrophysiologic-behavioral threshold differences at higher degrees of SNHL. There was a moderate-to-strong positive correlation at normal and earlier degrees of hearing loss and a weak positive correlation at higher degrees between the electrophysiologic and behavioral thresholds. Moreover, regression equations predicted pure-tone thresholds from that of NB chirp-ABR.
Conclusions
The current results indicate that the NB chirp-ABR can be used effectively as a diagnostic tool to evaluate hearing thresholds in adults with different degrees of SNHL. Therefore, the NB chirp-ABR can be suggested to apply to frequency-specific threshold estimation in difficult-to-test individuals.