Application of distortion product otoacoustic emissions to inflation of the eustachian tube in low frequency tinnitus with normal hearing

Objective: This study was designed to investigate the applications of distortion product otoacoustic emissions to assess the efficacy of eustachian tube inflation on low frequency tinnitus with normal hearing. Methods: Ninety-four patients (155 ears) suffering from subjective tinnitus with normal hearing sensitivity participated in this study. Control group consists of fifty volunteers (100 ears) without tinnitus. They were subjected to full history taking, otoscopy, basic audiologic evaluation and distortion product otoacoustic emissions (DPOAE). As for the patients with decreased DPOAE amplitude over a limited frequency range from 0.5 to 1 kHz, we offered nose dropping and tubal inflation for a week and DPOAE was preformed again. The patients were followed up for a month. Results: 34.8% DPOAE-gram showed decreased amplitude at the frequencies from 0.5 to 1 kHz in tinnitus group and "the ring" is mostly lower in pitch. Among the patients accepted the treatment of eustachian tube inflation, 16.7% the tinnitus disappeared, no recurrence within one month; 66.67% the tinnitus reduced within one month. 95.5% the amplitude of DPOAE showed improved over the limited frequency. 16.7% the tinnitus still existed. Conclusion: The changes of the mechanical properties of ossicular chain or the tympanic membrane influenced by tympanum pressure may cause tinnitus, which is sub-clinical prior to the changes of audiometry and tympanometry. The low frequency tinnitus may gain transitory relief from ringing with the tubal inflation. DPOAE was proved to be a useful tool in the evaluation of the efficacy of tubal inflation on low frequency tinnitus with normal hearing. (c) 2012 Elsevier Ireland Ltd. All rights reserved.