Comparison of thresholds estimation in adults with conductive hearing loss and normal hearing adults using auditory steady state response evoked by narrow band CE-chirps

Abstract

Background: Narrowband CE Chirps (NB CE-chirps) were used to provide the characteristics of compensation for the cochlear traveling wave delay and frequency specificity.Aim: The aim was to compare the objective frequency-specific hearing thresholds estimation by the use of NB CE-chirps ASSR and behavioural thresholds in normal hearing subjects and patients with the conductive hearing loss.Subjects and methods: The cases group comprised 35 ears of 25 patients with the conductive hearing loss with varying degree from mild to severe in severity and their age ranging from 15 to 60 years. They were compared with 20 ears of 10 adult control subjects with normal hearing thresholds, whose age ranged from 19 to 42 years. All cases and controls were subjected to pure-tone audiometry (PTA), tympanometry and auditory steady-state response (ASSR), using 4 NB CE-chirp for air conduction (AC) and bone conduction (BC) threshold estimation.Results: AC-ASSR estimated thresholds were statistically significantly higher than AC PTA thresholds at 500, 1000, 2000 and 4000 Hz in both the cases and the control groups. BC ASSR estimated thresholds were statistically significantly lower than BC PTA thresholds only at 500 Hz in the cases and statistically significantly higher than BC PTA thresholds only at 2000 Hz in the controls. There was a statistically significant positive correlation between AC-ASSR and AC PTA, and between ABG-ASSR and ABG PTA in the cases group.Conclusions: Auditory steady-state responses with NB CE-chirps is suitable tool for objective frequency-specific hearing threshold detection, that can be used for estimation of behavioural bone conduction thresholds in adults with conductive hearing loss, with more accuracy in the mid frequencies, and can estimate behavioural air conduction thresholds and air-bone gap more accurately in the higher frequencies 2000, 4000 Hz more than at 500 and 1000 Hz.