Sudden Traumatic Noise Exposure Induces an altered wave I in the Auditory Brainstem Response in Human

INTRODUCTION: Noise trauma may induce auditory symptoms and temporary or permanent shifts in hearing thresholds, assessed with a tone audiogram. Until recently it has been assumed that primary changes after noise trauma exclusively represent damage to the sensory hair cells. Contrary, animal studies have now shown early alterations in auditory brainstem response (ABR) characteristic of auditory neuropathy (AN), as reduction or absence of wave I, following noise trauma. AN involves a variety of disease mechanisms in the cochlea and auditory nerve, affecting the synaptic encoding and/or neural transmission of auditory information. The aim of this study was to evaluate whether patients exposed to noise trauma exhibit click ABR alterations characteristic of AN. METHOD: Thirty-one adult patients who attended an ear-nose and throat clinic, after a noise trauma, were included and an age- and gender-matched control group of 31 adults was constructed. To evaluate audiologic hearing impairment pure tone audiometry, click ABR and transient evoked otoacoustic emissions (TEOAE)/cochlear microphonics (CM) were performed. A full linear mixed model including the interaction between sex and group was tested. RESULTS: Our study showed that individuals exposed to sudden and distinct traumatic noise exhibit a statistically significant reduction (81.1 nV, p < 0.001) in the amplitude of wave I in ABR. CONCLUSION: We suggest that the hearing investigation after sudden traumatic noise exposure should therefore be expanded with ABR to confirm or exclude AN.