Otoacoustic emissions in patients with tinnitus and normal hearing

Abstract

Objectives: Tinnitus is defined as a sound perception in the absence of a sonorous external stimulus. This symptom is highly associated to hearing loss, although about 10% of the patients with tinnitus have a normal hearing. We studied the otoacoustic emissions (OE) in patients with complaints of tinnitus and normal hearing. Methods: We evaluated 104 patients with tinnitus. Only 10 met the inclusion criterion that was to have thresholds of 20 dB or less in each frequency at tonal audiometry; 5 were men with average age of 36.1 years. OE was performed in each patient. History of occupational noise exposition was evaluated. Results: Sixty percent had OE absent or lowered in one or more frequencies; 60% of them had a positive history of occupational noise exposition (time average of 7.58 years); and 83% of them did not use individual protection equipment. Conclusion: One of the theories that try to explain the pathogenesis of tinnitus is the imbalance between external hairy cells (EHC) and internal hairy cells (IHC). The EHC are more prone to damage and, when it occurs, they fail to perform the inhibition over the ICH function. This lost of IHC inhibition results then in tinnitus. Our results agree with this theory mainly because our patients had alterations in the EHC demonstrated by the OE.