Evoked otoacoustic emissions (EOAEs) were measured in 30 patients with unilateral tinnitus before and after intravenous injection of lidocaine. After lidocaine injection, in 22 (73%) of 30 patients, tinnitus disappeared completely or diminished partially. Concerning EOAEs, in 18 (60%) of 30 patients, the amplitudes of EOAEs showed some changes. In these 18 patients, tinnitus disappeared completely or diminished partially in 17 (94%) patients. On the other hand, in 12 patients without any change of EOAEs, tinnitus was found to disappear or diminish only in five (42%) patients. The above results may indicate that intravenous lidocaine injection has the effect on cochlear micromechanics, and suggest that there is a relationship between EOAEs change and tinnitus suppression in their mechanism.
The blood flow in cutaneous vessels of a finger was monitored by using a laser Doppler flowmetry from 37 tinnitus patients during electrical promontory stimulation. When tinnitus was fully suppressed by electrical promontory stimulation, increased blood flow in the cutaneous vessels was observed. On the contrary, blood flow in patients without tinnitus relief following electrical promontory stimulation was not increased. This study showed that blood flow in the finger cutaneous vessels using a laser Doppler flowmetry was a good objective, but indirect assessment of electrical stimulation for tinnitus patients. There was no correlation between the ratio of blood flow before/after treatment and etiology of hearing loss, age and hearing level.
A comparative study on the results with the whispered voice test and pure tone audiometry was undertaken on 104 patients from 3 to 21 years old. The results obtained were as follows. 1) The whispered voice test, which had already been performed in Aichi Prefecture and consisted of words with the acoustical characteristics at 1000Hz and 4000Hz, was benefical for screening of children for low frequency or high frequency hearing loss. And the test was available to detect whether the hearing loss was over 20dB or not at mean hearing level of 2000, 4000 and 1000Hz. 2) About 20% of mothers were not able to whisper correctly but talked in low voice. We must invent a scheme how mothers can whisper correctly. But even if the test is undergone by low voice, we expect that considerable number of hearing impaired children whose mean hearing level at 500, 1000, 2000 and 4000Hz is 40-49dB can be detectable. Therefore it is very important for mothers to undertake the whispered voice test at home.
The relation between the most frequently used gain (MFUG) of hearing aids and hearing levels was studied in 335 cases with mild to moderate sensorineural hearing loss. The MFUG was measured at 500, 1000 and 2000Hz, and these hearing aids were selected and adjusted by repeated audition in every day life. The results were as follows: 1) As the average hearing levels increased, the MFUG (averaged by 500, 1000, 2000Hz) was increased. But, the MFUG was different from individual to individual among the same hearing level groups. 2) In the study of each frequency, as the hearing level increased, the MFUG was increased. And the degree of increase of the MFUG differed in each frequency. And in the case with mild hearing loss, the MFUG of high frequency was relativery large, and as the hearing became worse, the difference of the MFUG in each frequency became smaller. 3) Comparing the MFUG with the gain by half gain method, the MFUG was smaller than the half gain. The half gain was located near the limit of the range of the MFUG.
Cisplatin (7.5mg/kg) was administered to the guinea pigs intramuscularly twice at an interval of 5 days. The thresholds of compound action potential (CAP) showed a rapid elevation at all frequencies after the second injection, while they showed an elevation only at high frequencies after the first injection. These electrophysiological results were in agreement with the cochleograms, and the slight damage of outer hair cells (OHCs) was observed after the first injection, while the damage was fairly strong after the second injection. For assessment whether cisplatin directly affects on OHC, which is assumed as a main target of this drug, isolated OHCs of the guinea pigs pre-treated with cisplatin were incubated in the medium containing 1mM CDDP. The viability curve of isolated OHCs 6 days after the pre-treatment, evaluated by using the nuclear dye propidium iodide, showed a rapid decrease compared with the non-treated. On the other hand, the cochlear damage in vivo after the second injection at an interval of 17 days was mild, and viability of the OHCs which were isolated 17 days after the pre-treatment was not different from the control group. From these results, it was shown that the shorter the interval of two treatments was, the stronger the OHC damage became. It was suspected, furthermore, there was a possibility of the recovery of OHC damage after long interval, and direct effect of CDDP on OHCs besides nephrotoxicity and strial disorder played a role as a part of acute ototoxicity after repeated treatment at a short interval with CDDP.
More than four years have past since a screening audiometry using 1kHz and 4kHz was made mandatory in general health examination. We investigated results of screening audiometry at several health examination offices and studied how it is carried out and its problems. The rate of positive findings by sex and frequency was relatively high in males with 4kHz alone. The rate of positive findings by job category suggested the possiblity that males of 50 years and older in a specific job category (job category with a relatively high level of noise) would have mild noise-induced deafness. Based on the results of these investigations, we studied on what extent noise-induced deafness is detected by a special health examination at the noiso works hops. As a result, the number workers exposed to noise of more than Leq 85dB (A) was estimated at about 2, 500, 000. Of them, about 200, 000 to 400, 000 were suspected of have noise-induced deafness.
Fluid loading audiometry, a diagnostic method to determine ossicular function or stapes mobility, is based on the threshold difference (TD) between bone conductions when fluid is present or not in the external ear canal, reflecting the mobility of the stapes foot plate. For the purpose of utilizing this testing method for evaluating ossicular mobility, we first investigated and confirmed the utility and reliability of this testing method. From 34 notmal ears we obtained normal range of TD at 250, 500, 800 and 1000Hz, each mean value of which was only about 2.5-7.5dB less than that obtained by Tsunoda, who has proposed this method. In 256 ears classified into 5 groups with nonperforated ear drums and 3 groups with perforated ones, mean TD value for each group of each frequency was obtained. From these results we obtained diagnostic value of more than 20dB and less than 10dB at 250Hz for ossicular function and that of more than 10dB and less than 5dB at 1000Hz for situation of middle ear cleft under the condition that TD at 250Hz is more than 20dB. Mechanism of threshold difference was also discussed.
Measurement of aided thresholds in a sound field is often used in hearing-aid evaluation for children. These measurements can also be used to calculate the Aided Articulation Index (AAI). Hearing threshold levels, aided threshold levels, and hearing-aid output levels with 90dB input sound pressure levels were used to calculate the AAI. A Word-Pattern Perception Test and a Word Identification Test were also performed. Hearing-impaired children in a school for the deaf were enrolled in this study. The results suggested that the AAI decreased gradually with hearing threshold level. Test scores for the Word Pattern Perception Test were higher than those for the Word Identification Test. Even subjects whose AAI was around 0.1 attained relatively high word pattern perception scores. Subjects with an AAI of less than 0.3 showed markedly lower scores on the Word Identification Test. In severely to profoundly hearing-impaired children, an AAI of 0.3 was considered necessary to function effectively with speech communication.