Speech-evoked auditory brainstem response with ipsilateral noise in adults with unilateral hearing loss.

ABSTRACT

INTRODUCTION: Subjects with unilateral hearing loss (UHL) report difficulties in speech understanding in noise. Speech-evoked auditory brainstem response (S-ABR) provides cues for temporal and spectral encoding of speech in the brainstem. S-ABR recording in noise increases its sensitivity in evaluating the auditory processing and related disorders. OBJECTIVES: Study speech encoding at the level of brainstem when the auditory system relies on one ear and to study the effect of noise on this encoding. SUBJECTS AND METHOD: This study included two groups control group consisted of 15 adults with normal hearing sensitivity and study group consisted of 30 adults with UHL. The study group was further subdivided into two subgroups study subgroup A (SG A) consisted of 15 adults with right functioning ears and study subgroup B (SG B) consisted of 15 adults with left functioning ears. S-ABR in quiet and with ipsilateral noise was recorded in both the groups using complex ABR advanced auditory research module. RESULTS: In UHL, there was a statistically significant delay in the S-ABR onset and offset in noise compared to quiet. Moreover, quiet-noise (+5 SNR) correlation was significantly low compared to NH. Furthermore, pitch representation (F0 amplitude) was significantly degraded with noise. In addition, there was a statistically significant noise-induced phase shift in the transition region of speech syllable in these subjects. CONCLUSION: In monaural processing, pitch representation (F0 amplitude) and cross-phaseogram were the main affected domains. Speech phonemes of transient origin can be confused in subjects with UHL.