The Relationship between Ultra high frequency Thresholds and Transient Evoked Otoacoustic Emissions in Adults with Tinnitus.

The possible role of cochlear function in tinnitus generation is still a matter of debate. To assess the role of outer hair cell dysfunction in tinnitus and its possible relationship with ultra-high frequency (UHF) hearing sensitivity, transient evoked otoacoustic emissions (TEOAE) and UHF hearing thresholds were investigated in normal hearing individuals with and without tinnitus. Eighteen individuals with tinnitus and 22 without tinnitus participated in this study. TEOAE was recorded with click stimulus at 80 dBpeSPL. UHF pure tone audiometry was performed at 10, 12.5, 16, and 18 k Hz. The individuals with tinnitus had significantly poorer UHF hearing sensitivity compared to the control group at 12.5 and 18 k Hz (p<0.048). TEOAE was significantly abnormal in 72.2% of the tinnitus, and 18.2% of the control groups (p=0.001). 'There was a stronger correlation between increasing UHFs hearing threshold and decreasing SNRs of TEOAEs in the tinnitus group compared to the controls. The results support the deafferentation hypothesis, which suggests that the cochlear damage triggers tinnitus incidence, even in patients with normal hearing sensitivity on conventional audiometry, and considers a deafferentation as the underlying cause that elicits central reorganization and eventually leads to tinnitus. The deafferentation hypothesis provides a rationale for performing UHF threshold and OAE assessments in subjectively normal hearing patients with tinnitus. Our study revealed poorer UHF hearing thresholds and more TEOAE abnormalities in normal hearing individuals with tinnitus compared to the controls. Perhaps the alterations in the basal cochlea, following a decrease in UHF hearing sensitivity, affect OAEs that are originated from more apical cochlear parts in tinnitus ears more than non-tinnitus ears. [ABSTRACT FROM AUTHOR]