Abstract:
This study examined the effectiveness of auditory measures that past studies have proven to have potential use in a clinical test battery for identifying a hidden hearing loss and/or cochlear synaptopathy.
The auditory and neural functioning was compared between 20 participants with no reported history of noise exposure and 20 participants with a history of occupational noise exposure. Each group aged 18 - 35 years (M = 27.1 years, SD = 4.56 years), presented with clinical normal hearing. A between-group comparison, cross-sectional analytic study design was implemented. Audiologic measures included pure tone audiometry in the extended high frequencies, distortion product otoacoustic emissions (DPOAEs), middle ear muscle reflexes (MEMR), auditory brainstem response (ABR), electrocochleography (ECochG) and a digits-in-noise test.
The noise-exposed group presented with the following results that significantly differed from the non-noise-exposed group: elevated contralateral MEMR for 500 Hz and a 1000 Hz, a decrease in ABR wave V amplitude (rarefaction, condensation and alternating polarity), a decrease in ABR wave III amplitude (rarefaction and alternating polarity only), a shift in ABR wave V latency (condensation polarity only) and lastly a shift in the ECochG AP latency. No significant difference in test results were observed between the non-noise-exposed group and the noise-exposed group for the DPOAE-, extended high frequency audiometry- or digits-in-noise test.
Results suggested that the inclusion of contralateral MEMR’s, the ABR as well as the ECochG test may be valuable tools in a test battery investigating hidden hearing loss and/or cochlear synaptopathy in populations presenting a noise exposure history similar to the nature of occupational noise. It was further postulated that the nature of the noise individuals are exposed to may play a role in the neural site of lesion and therefore in the effectiveness of the selected audiometric measure in identification of hidden hearing loss.
