Aided Sound-Field Evoked Frequency Specific Auditory Brainstem Responses in Paediatric Cochlear Implant Users

Abstract

Introduction: The cochlear implant (CI) is a surgically implanted device that bypasses the damaged part of the auditory system and provides direct stimulation to the auditory nerve. CI programming is a technique that helps clinicians to set accurate lower stimulation levels (T-level or threshold level) and upper stimulation levels or comfort levels (C-level) through mapping. Auditory brainstem response (ABR) is the most widely used diagnostic tool in audiology to estimate the hearing threshold especially in difficult to test population. Frequency-specific ABR is often used to obtain frequency specific information about the auditory system. Aim of the study: The present study aimed to evaluate aided sound-field evoked frequency-specific auditory brainstem responses (ABRs) thresholds and its relationship with aided behavioural sound-field thresholds in paediatric cochlear implant (CI) users. Methods: A total of twenty paediatric CI users participated in the study. Frequency specific ABRs were recorded in the aided sound-field condition using tone burst stimuli across four frequencies (500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz). The ABR threshold, wave V absolute latency and peak-to-peak amplitude were analysed and compared across frequencies. The Agreement between ABR thresholds and aided behavioural sound-field thresholds was measured for all the four frequencies. Results: There was significant effect of frequency and intensity on aided ABR wave V latency and peak to peak amplitude. Latency range for 500 Hz (13.4-16.95), 1000 Hz (11.95 -15.40), 2000 Hz (11.7-13.95) and 4000 Hz (11.4-13.8) and peak to peak amplitude range for 500 Hz (0.39-3.01), 1000 Hz (0.72-4.37), 2000 Hz (0.92-5.79) and 4000 Hz (1.04-6.3). The mean difference was negative at lower frequencies -9.75 dB SPL at 500 Hz, -7.50 dB SPL at 1000 Hz, -2 dB SPL at 2000 Hz and the difference shifted into positive values 3 dB SPL at 4000 Hz. Conclusion: The aided sound-field evoked frequency-specific ABRs provide reliable objective method to estimate frequency specific thresholds in paediatric CI users. The aided ABR can be used to guide CI mapping and evaluate aided benefit when behavioural responses are limited or inconsistent.