ABR findings in musicians with normal audiogram and otoacoustic emissions: evidence of cochlear synaptopathy?

Abstract

Purpose: Although findings in human studies trying to identify signs of cochlear synaptopathy (CS) are still controversial, several methodological restrictions exist, including inconsistencies in participants profiles, definition of study groups and inclusion criteria, diverse electrophysiological measurements settings and noise exposure history metrics and participants’ age range, which question the reliability of conclusions.Method: Two groups of individuals aged 18–41 participated in this study. The first group consisted of 24 musicians with well documented occupational noise exposure and the second one of 24 healthy controls. Groups were matched for age and gender. Inclusion criteria were normal and symmetrical pure tone audiometry and extended high frequency audiometry thresholds, as well as present and normal TEOAEs and DPOAEs. Outcome measures included SNR scores of speech in bubble audiometry and auditory brainstem response waves I, II and V amplitudes and latencies at three different presentation rates: 11, 33 and 44 clicks/s.Results: Wave I amplitude in musicians was significantly lower compared to controls at all presentation rates (11/s: p .043, 33/s: p .007 and 44/s: p .014). There was also a significantly greater reduction in wave I amplitude as well as in wave Ι/V amplitude ratio in the 33/s stimulus presentation in musicians compared to the control group (p .02 and .01, respectively). Finally, lower wave I amplitudes were found in musicians with auditory symptoms compared to musicians without symptoms at the 44/s presentation rate (p = .002).Conclusion: The ABR findings in our study are suggestive of possible increased prevalence of CS in musicians. Wave I amplitude was lower in Musicians group compared to matched controls. Furthermore, there was a greater reduction of wave I amplitude and wave Ι/V amplitude ratio at higher stimulation rates, which would support their use in CS studies.