Comparative study of auditory brainstem response and auditory steady-state response as an objective measure for hearing aid verification

Introduction: Hearing aid benefit could be measured objectively by electrophysiological tests. Objective measures are important for hearing assessment in individuals who are unable to provide behavioural responses to reach optimal hearing aids fitting verification. Purpose: This study was designed to compare the Functional Gain (FG) of Auditory Steady State Response (ASSR) and Tone Burst Auditory Brainstem Response (TB ABR) as objective tools with the subjective FG using sound field pure tone audiometry (PTA) in adult patients with sensorineural hearing loss using two hearing aid fitting formulae; DSL v5 and NAL-NL2. Material and methods: This study included twenty hearing-impaired adults, their hearing thresholds ranged from moderate to moderately severe sensorineural hearing loss with flat or gradually falling configuration. Their age ranged from eighteen to sixty years. Subjects were examined in three scheduled sessions; unaided, aided NAL-NL2 and aided DSL V5. Each session included free field PTA, TB ABR and ASSR testing at four tested frequencies 500, 1000, 2000 and 4000 Hz. Results: The mean difference between free field PTA FG and TB ABR FG was 6.02 +/- 5.11 and 6.51 +/- 4.53 by NAL-NL2 and DSL v5 respectively. The cumulative percentage of cases who had mean total differences within +/- 2 SD (<+/- 15dB) was 100% in both formulae. The mean difference between free field PTA FG and ASSR FG was 2.00 +/- 7.48 and 2.00 +/- 6.99 by NAL-NL2 and DSL v5 formulae respectively. The cumulative percentage of cases who had mean total differences within +/- 2 SD (<+/- 15dB) was 90% in NAL-NL2 formula and 95% in DSL v5 formula. When using identical test conditions and the same type of stimulus, NAL-NL2 and DSL v5 revealed similar functional gain measurements. Conclusions: Both TB ABR and ASSR are valuable objective measures for thresholds detection. The FG measured by TB ABR and ASSR could be applied as an objective tool for hearing aid fitting verification in hearing impaired individuals.