Spontaneous Otoacoustic Emissions in Tinnitus Patients

Abstract

Otoacoustic emissions (OAEs) are believed to be the products of active cochlear mechanics. They are generally associated with relatively intact outer hair cell function. OAEs usually decrease or become undetectable when hearing loss of cochlear origin exceeds 40-50 dB HL. Subjective tinnitus is a perception of sound without detectable corresponding source. It is most often seen in patients with hearing loss. It is also frequently seen in patients with head injuries. Studies have suggested that the prevalence of spontaneous otoacoustic emissions(SOAEs) is lower in patients with hearing loss and tinnitus than in normal population. There have also been reports on association between tinnitus and SOAEs of unusually high amplitudes, which can be controlled by aspirin administration. The current paper is a preliminary review of clinical data collected from a group of tinnitus patients in an attempt to elucidate on the relationship between SOAEs and tinnitus from a clinical point of view. Audiometric, tinnitus and SOAE data from 59 patients seen at the Oregon Health & Science University Tinnitus Clinic were retrospectively studied. Fifty-four of these 59 patients showed sensorineural hearing loss of various degrees at the time of evaluation, mostly affecting high frequencies. SOAEs were detected in 26 ears (22%) of 18 patients(30.5%). There was no difference in SOAE prevalence between male and female patients. SOAEs were recorded in four of the five patients whose pure tone thresholds were within normal limits up to 8000 Hz. SOAEs appeared to be recorded at a higher rate in patients whose tinnitus started following motor vehicle accidents or head injuries(5/10) than in other patients. Time course of tinnitus did not appear to affect SOAE detection rate. There were no correlations between SOAE frequency and matched tinnitus pitch or frequency of maximum hearing loss. Significance of these findings is discussed.