[Tinnitus with normal hearing and evoked otoacoustic emissions].

Objective: To investigate the objective methods for tinnitus exploration by analysing the cochlear activity in tinnitus patients with normal hearing.

Method: The 50 cases (50 ears) of unilateral tinnitus with normal hearing (the plastic group 1), 24 cases (46 ears) of bilateral tinnitus with normal hearing(the plastic group 2) and the 34 persons (68 ears) of normal hearing without tinnitus (control group) were measured by evoked otoacoustic emissions (TEOAE and DPOAE). All the tinnitus patients were also tested by the subjective tinnitus frequency and analysed with appropriate characteristic in TEOAE and DPOAE audiogram.

Result: (1) The passing rate of TEOAE was 64.0% in the tinnitus group 1, 91.3% in the group 2, and 100% in the control group (group 1 P < 0.01, group 2 P >0.05 ). (2) The passing rate of DPOAE was 100% in three groups. But comparing to the control group, the amplitudes of DPOAE at the limited frequency ranges (3.125 kHz and 8.837 kHz) of the tinnitus group 1 was significant decreased ( P <0.05). (3) The subjective tinnitus frequencies were 0.25 approximately 8.00 kHz. The decreases in amplitudes and absent within the tinnitus frequencies were observed in TEOAE and DPOAE audiogram.

Conclusion: Some patients of normal hearing with tinnitus have had early harmness of outer hair cell in cochlear. Evoked otoacoustic emissions is one of worthy methods to evaluated objectively the tinnitus. TEOAE is more susceptible to harmness in cochlear than DPOAE. DPOAE is superior to the analysis of tinnitus frequencies.