Abstract:
Purpose:
To compare LS CE-Chirp and click evoked neuro-diagnostic auditory brainstem responses (ABR) for the purpose of determining the preferable stimulus for assessment. This is necessary for the improvement of neural synchrony and compensation for the delay of the sound wave whilst it travels through the cochlea. This will facilitate more successful, efficient and effective neurological ABR assessments.
Method:
This was a within subject comparative, exploratory research design. Participants included 34 normal-hearing individuals (aged 18-25 years, mean age 22.12 years). A comparison was completed between the ABR wave formations evoked by the click and LS CE-Chirp stimuli at 80 dBnHL at stimulus repetition rate of 27.4 Hz and 61.1 Hz with maximum permissible residual noise levels of 40 nV.
Results:
The LS CE-Chirp evoked ABR displayed later absolute latencies and shorter interpeak latencies compared to the click-evoked ABR. Significantly larger amplitudes were consistent for the LS CE-Chirp wave formations (p<0.001) with the exception of the wave I for the rarefaction polarity. Residual noise levels were consistently higher for the LS CE-Chirp stimuli, however, there was no correlation present between the amplitudes and the comparative residual noise levels.
Conclusions:
The LS CE-chirp stimulus elicited considerably larger waveform amplitudes, which facilitate more accurate and timely ABR assessments compared to the click. The lack of correlation between amplitude and residual noise levels suggested independence of residual noise levels, and therefore were likely due to the increased neural synchrony inherent to the chirp stimuli. The click stimulus is still advocated for during neuro-diagnostic assessments as despite the larger LS CE-Chirp amplitudes, further research regarding the correlation with auditory-neural pathology is required before the routine use of the LS CE-Chirp stimulus can be advocated over the well-established click stimulus for neuro-diagnostic purposes.
