Effect of Tinnitus in Distortion Products Otoacoustic Emissions (DPOAEs) in Normal Hearing Patients

Tinnitus is a symptom whose pathophysiology remains still unclear. Its diagnosis and treatment is complicated, due to its subjectivity. The generation of tinnitus is commonly linked with the impaired functioning of the outer hair cells (OHC) inside the cochlea. Distortion product otoacoustic emissions (DPOAEs) are the objective test used to assess their activity. This study investigates the cochlear outer hair cell function in patients with tinnitus and normal hearing using DPOAEs. We performed a prospective study of the cochlear function in normal hearing patients complaining of tinnitus by analysing DPOAEs amplitude and signal/noise (S/N) ratio. We gathered a sample of 21 ears from adults that attended to the ENT Department complaining of tinnitus with normal hearing. We compared their results with a control group of 21 ears, with the same demographic characteristics, presenting normal hearing but without tinnitus in order to exclude the influence of age in DPOAEs results. A decreased mean of S/N levels in DPOAEs was found in tinnitus and normal hearing group comparing with control group, although these differences were not statistically significant ( p > 0.05). Based on the results, OHC dysfunction is not necessary to experience tinnitus. The majority of the patients that present OHC dysfunction do not present a tinnitus at the moment. Other mechanisms in auditory pathway may be evaluated in the tinnitus development.