O10 The usage of bone conduction (BC) with time-varying frequency chirp stimulation to evaluate auditory brainstem response (ABR)

Abstract

Background Chirp is a frequency time-varying stimulation that compensates for the temporal dispersion in the cochlea by delaying high frequencies of stimulation, so that both low and high frequencies will transmit simultaneously from the cochlea. Most studies that examined the effectiveness of Chirp stimulus used AC ABR, while only little research was done with BC stimulus, which is important for detecting mixed and sensory-neural hearing losses. Objective The purpose of this study is to modify a Chirp stimulus that will match the frequency response of B71 bone vibrator (250–4000 Hz) and compare it to AC stimuli. The research examines correlations between hearing thresholds for Chirp ABR, Click ABR and the behavioral audiometric threshold for those stimuli. Methods 15 healthy students with normal hearing at University of Haifa, aged 19–30 were tested with Navigator-Pro (Natus). Stimuli intensity level was related to the psycho-acoustic threshold of each stimulus and each ear. ABRs were evoked using BC and AC Chirp and Click presented at 60, 40, 20 dB sensation level, and at threshold level, with stimuli rate of 27.1⧹s. Results Chirp stimulus evokes larger ABRs in normal-hearing subjects than standard click stimuli, both in BC and AC. ABR threshold with Chirp stimulus is significantly closer to its psychoacoustic threshold than the Click stimulus, both in BC and AC. Conclusion ABR for BC Chirp results are similar to AC results in adults near psychoacoustic threshold. Significance BC Chirp may be used for hearing threshold assessment using ABR, especially in cases with conductive loss.