Objective Audiology Tests Of Tinnitus Patients With Normal Hearing And The Significance

Objective: Tinnitus is very popular in the people, and would interfere with people's normal life seriously. Tinnitus patients with normal hearing is not uncommon clinically. We studied the characteristics of objective audiology tests in tinnitus patients with normal hearing, including pure tone audiometry,acoustic immittance,middle ear muscle reflexs,matching test,acoustic emission(OAE),auditory brainstem response(ABR) and high frequency stimulation rate ABR, and tried to find the relationship between tinnitus and each testing method, explored mechanisms of tinnitus and the objective basis for diagnosis, provided informations for treatment and therapeutic effect evaluation.Methods: Choose 50 tinnitus patients (69 ears) with normal hearing as tinnitus group and 30 volunteers(60 ears) no difference in the age and sex with normal hearing as control. Pure tone audiometry,tympanometry,stapedial reflex threshold,tinnitus determination (including pitch matching,intensity matching and residual inhibition test),transient evoked otoacoustic emission (TEOAE) and distortion product otoacoustic emission (DPOAE),auditory brainstem response (ABR) and high frequency stimulation rate ABR were performed in each patient and control respectively. Compare the detection rate of TEOAE,DPOAE,the frequency detection rate and the response amplitude of every frequency between the two groups. Analysis the correlation between the tinnitus matching melody and the frequency in which DPOAE amplitude declined or absent, measure the I, III, V peak latencies (PL), interval peak latencies (IPL) and amplitude in normal rate ABR(11.1/s) and high frequency stimulation rate ABR in the two groups. Calculated the peak latency difference of waveⅤ(△Ⅴ) within the two stimulate rate. The results were analyzed by the SPSS11.5 for Windows.Results: The results of tinnitus determination were that 66 out of 69 tinnitus ears'frequency can be successfully matched and within audio-frequency range, the higher frequencies were 4kHz(17.4%),6kHz (15.9%),500Hz (13%),125Hz (13%),250Hz (11.6%),8kHz (11.6%), 49.3% was positive in RI test and the relative strength of the tinnitus threshold was 8.8~16dB nHL. The detection rates of TEOAE and DPOAE were 66.7%,88.4% in patients of tinnitus groups, which were significant lower than those in control group (P<0.05) , particularly the DPOAE detection rates were low in 500Hz and 4000Hz compared to that in control group (P<0.05), the tinnitus patients had lower DPOAE amplitudes in 500Hz,750Hz,3kHz,4kHz,6kHz,8kHz than those in the control group, which were statistically significant (P<0.05).There was a high corresponding rate (average 63.6%) between tinnitus matching melody and the frequency in which DPOAE amplitude declined or absent. There were 43 ears (86%) which can elicit DPOAE, but some frequency performed amplitude declined or absent; 42 ears performed DPOAE amplitude declined or absent in the frequency of tinnitus matching melody. Both the tinnitus group and the control group could induce ABR waveform with better repeatability. With both the two stimulation rate, the tinnitus group performed PL of wave I, III, V prolonged compared with the control group, and the difference was significant (P<0.05), PL of wave I was extraordinarily longer (P <0.01), I-III, III-V. I-V Wave interval peak latencies (IPL) was no significant difference in meaning compared with the control group.△Ⅴand△I-V were also prolonged in tinnitus patients compared with the control group with both two rates and the difference was significant (P<0.05). The frequency of bigⅢand small V in ABR test was significantly different between the two groups (P<0.01). V / I amplitude ratio was larger than 1 in both tinnitus group and the control group. Statisticly there were 46 ears (66.7%) performed abnormal ABR: 32 ears performed prolonged PL of wave I, III, V and 13 ears had IPL prolonged ofⅠ-Ⅲ,Ⅲ-Ⅴ,Ⅰ-Ⅴwith normal stimulation rate; 39 ears performed prolonged PI of wave I', III', V'and 17 ears IPL prolonged ofⅠ'-Ⅲ',Ⅲ'-Ⅴ',Ⅰ'-Ⅴ'with high frequency stimulation rate; there were 13 ears that had△PLⅤ>0.3ms; 22 ears had a bigⅢand small V ABR wave.Conclusions: 1. Normal hearing is not representable of nice auditory function in patients with tinnitus, using otoacoustic emissions test (TEOAE and DPOAE) could reflect cochlear hair cells'lesion in early stage and provide an objective basis for the cochlear mechanism of tinnitus. 2. DPOAE has its own frequence specificity, the study showed a considerable part of tinnitus patients with normal hearing performed DPOAE amplitude declined or absent in the frequency corresponding with tinnitus matching melody, it would consider whether it is impossible to take DPOAE as a method to assess tinnitus pitch. 3. ABR test was helpful for diagnosis of lesions in some tinnitus patients with normal hearing and can provide an objective basis for the central mechanism of tinnitus. But our study did not find patients with post-cochlea lessions. 4. There were some tinnitus patients with normal hearing performed prolonged PL of wave I,III,V with both the two stimulation rate , significantly of wave I . 5.△PLⅤby the two stimulation rate ABR were longer than 0.3ms in some patients, which suggested that there may be obstacles of the blood supplying within the auditory pathway. 6. Part of the tinnitus patients with normal hearing performed a big wave III and small V in ABR test. This maybe the specific changes in some tinnitus patients.