Contralateral Masking in the Measurement of Auditory Brainstem Responses with Air-Conducted Tone Burst Stimuli in Individuals with Unilateral Hearing Loss

Abstract

Background Contralateral noise masking is an important aspect of auditory brainstem response (ABR) measurements. Purpose The primary aim of this study is to determine how contralateral white noise (WN) masking influences the amplitude and the latency of V wave generated during ABR measurements, using tone burst (TB), in adult ears with normal hearing (NH). The secondary aim of this study is to ascertain the need of contralateral masking in ABR measurements with the TB stimuli using a 3A insertion earphone, and to propose the applicability of WN masking in unilateral sensorineural hearing loss (USNHL). Research Design It is a cross-sectional observational and descriptive study. Study Sample Experiment 1: Thirty individuals, without any otologic, psychological, or neurological dysfunction, were selected. Experiment 2: Fifteen individuals with previous audiological diagnoses of severe and profound USNHL were considered. Intervention The study involves ABR TB at specific frequencies of 0.5, 1, 2, and 4 kHz. Data Collection and Analysis Experiment 1: The evaluation was performed at the fixed intensity of 80 dB nHL (decibel normalized hearing level) on the tested ear, followed by the application of simultaneous masking to the nontested ear, intensity ranged from 0 to 80 dB. Experiment 2: ABR threshold measurements were first performed on the ear with hearing loss (HL) at the frequencies of 1, 2, and 4 kHz. The results were subsequently confirmed using contralateral masking. Results Experiment 1: At any given frequency, there were no statistically significant differences in the amplitude and latency of V wave with increase in the intensities of WN masking. Experiment 2: Cross-hearing was observed at least once in all frequencies analyzed through the occurrence of V wave. Conclusion In conclusion, the contralateral WN masking at the maximum intensity of 80 dB does not affect the amplitude and latency of V wave of the ABR TB at 1, 2, and 4 kHz. Contralateral masking for the ABR TB presented using 3A insertion earphones is necessary at 1, 2, and 4 kHz in individuals with severe or profound degrees of USNHL and at intensities of 15, 20, and 10 dB above the ABR threshold of the nontested ear.