The Verification of ABR Response by Using the Chirp Stimulus in Moderate Sensorineural Hearing Loss

Background: The Brainstem Auditory Evoked Potentials (BAEP) are historically recorded using clicks. An alternative to the click have been developed aiming to a simultaneous neuronal activation along the basilar membrane, and, consequently, the recording of responses with larger amplitude, this stimulus, named chirp. Objectives: Assessment of ABR responses in adults subjects with normal hearing sensitivity and in patients with moderate degree of SNHL by using chirp stimuli. Comparing the results of chirp ABR with those obtained from the same individuals using click stimuli. Methodology: Thirty young adult subjects ranging from 20 to 40 years with normal hearing sensitivity (group 1) and thirty subjects of same age group with moderate degree of SNHL (group 2) were evaluated. ABR recorded using low frequency (1000Hz) and high frequency (4000Hz) chirp stimulus and the results were compared with those obtained by click stimulus presented monaurally. Results: In this research we found a statistically significant difference as regards wave V latency between click, low frequency and high frequency chirp in all test conditions in subjects with normal hearing sensitivity. Also there is a statistically significant difference as regards wave V latency between click and high frequency chirp stimulus at both stimuli level used in patients with moderate degree of SNHL with shorter latencies by chirp stimulus. Shorter latency of wave V is found with high frequency chirp than low frequency chirp in group 1 at 10SL and in group 2 at 10 and 20SL. As regards wave V amplitude a statistically significant difference between click and chirp in all conditions in (group 1) and a statistically significant difference was found as regards wave V amplitude between click and chirp in all conditions except between click and low frequency chirp at 20dB SL (group 2). Wave V amplitude is larger with high frequency chirp in both groups. Conclusions: Response to chirp stimulus is characterized by shorter latency when compared to click stimuli and latency of wave V is shorter with high frequency chirp than with low frequency chirp. Wave V amplitude is larger with chirp stimuli than those obtained with click and amplitude of wave V is larger with the high frequency chirp than low frequency chirp.