The autitory screening system at 1-year-6-month-old children health examinations was established for the purpose of screening children with bilateral moderate and profound hearing loss. As a first screening method, we used the questionaire and the auditory test of responses to whisper voice by parents. For the children who failed the first screening, we performed the second screening test, behavioral observation audiometry (BOA). And as the further examination, we used COR and auditory brainstem response (ABR) for the children who failed the second screening. 1798 children had been screened in 1 city and 5 towns of Aichi prefecture during about 1 year, and the 7 children with hearing loss were found. Out of them, 2 children had bilateral sensorineural hearing loss. One had profound hearing loss and the other had moderate one. If this screening system had been correctly perfomed, we confirmed that children with bilateral moderate hearing loss could be found. Though the first screening method tested by parents have some problems, it is very effective to detect children with profound hearing loss. Even if the children with mild or moderate hearing loss would pass this screening, they can be detected as the three-year-old-children health examinations. And if auditory training is started for them at the age of three, they will be able to develope their language suitable for their intelligence with some difficulty.
We investigated the electrical stability of electrodes in long-term cochlear implant patients and the effects on the cochlear nerve. The function of the electrode array was studied using the minimal threshold level (T-level), the maximum comfortable level (C-level), and the dynamic range between T-and C-level (DR). The percentage of the electrodes in use decreased within 1 year after the initialization but was stabilized after that, and kept 89% for 4 years after the initialization. The electrodes became out of use mainly because of facial palsy and uncomfortable sensation, which was claimed mostly near the round window. The averaged fluctuation of T-level, C-level, and DR of each electrode became stable 1 year after the initialization and was within 25μA 4 years after in 10 cases in which all electrodes were in use for more than 4 years. The electrodes near the round window fluctuated largely. These results suggested that the surgical trauma brought the effect on the electrodes near the round window stepwise. The electrode showed stable response in one case 10 years after the initialization. We concluded the effect of long-term electrical stimulation under the allowed value on the cochlear nerve was not so much as to effect the ability of hearing.
Ten out of 62 children with bilateral severe to profound sensorineural hearing loss had fluctuation of their hearing. All children wear hearing aids in both ears, receive speech therapy, and have had audiometric examinations regularly. At every examination their hearing loss were aggravated in one or both ears. Only patient was suspected of acoustic trauma by the hearing aid. Six of the 10 children showed dizziness associated with deterioration. Five patients indicated positive glycerol and/or furosemide tests and administration of isosorbide was effective. Though endolymphatic hydrops (ELH) in children seems uncommon, we concluded that some of these children could have ELH as a cause of fluctuation of their hearing loss.
In order to investigate the effect of impulsive sounds from clay pigeon trapshooting on trapshooters, we measured the impulsive sounds using dummy head manequin equipment (KEMAR). We also carried out pure tone audiometry and questionnaire in 63 sport clay pigeon trapshooters The results were as follows. 1) A peak sound pressure level of the clay pigeon trapshooting was about 155dB 2msec after the blast and the peak frequency was around 2500Hz. 2) There were considrable difference in peak sound pressure level between the two cars, on the muzzle side, and the other side. 3) Three kinds of hearing protection devices (HPDs) were tested. The earplug was more effective in attenuating peak levels of shooting impulses than both the earmuff and the earbulb. 4) As a result of pure tone audiometry, 39 subjects showed noise induced hearing loss (NIHL) in high frequency and 24 individuals exhibited normal hearing. Comparing the results of questionnaire between the groups, in the group with NIHL, mean age and mean experience period were higher than the remainders. HPDs were not so frequently used, but HPDs were effective in protecting the trapshooter's hearing when used properly. Educations on the need and appropriate use of HPDs are recommended.
The effect of inter-click interval (Δt) and stimulus intensity on compound action potential (CAP) adaptation was explored in six guinea pigs. In addition, the effect of hypothermia on CAP adaptation was investigated in the same animals. CAP was elicited from the exposed round window through a retroauricular incision using a silver ball electrode. After obtaining the baseline data, hypothermia around 34°C was obtained. Click was used to track the threshold shifts. All animals showed almost no threshold shift throughout the experiment. Click train consisted of 10 clicks in three different Δts and intensities was delivered through the loud speaker placed in front of animals ear. The bigger Δt or the higher intensity, the smaller CAP adaptation occurred in normal temperature. Hypothermia induced decrease in CAP amplitude and altered adaptation pattern to click trains. Decreased CAP amplitude was induced by desynchronization. It is concluded from our results that hypothermia affects CAP adaptation process without changing threshold. It is proposed that CAP adaptation would be useful for detection of some inner ear dysfunction.
The auditory brainstem response (ABR) in neonates and infants should be carefully evaluated because of differences in development of hearing nervous system. We examined ABR in three neonates and 97 infants with risk factor of hearing impairment and the results were compared with final diagnosis mainly by COR. In addition, the study of developmental changes of latency and threshold was done. 51 cases with initially normal ABR were diagnosed normal hearing finally. 24 cases were proved to have normal hearing in spite of abnormality by the initial ABR and 88% of them were preterm infants or under two months old. In more than half cases of them normal results were obtained when ABR were done about 6 months old. Among the 100 subjects, one severe SNH and 13 moderate SNH were found. Half of them were accompanied with embryomental abnormalities, one case had only perinatal factor and 7 of them began the auditory training and hearing aid at about 1 year old. As a conclusion, hearing tests by ABR should be done early in high risk infants, and they should be examined again about their 6 months of age when the first ABR were abnormal.
Clinical data on 187 patients presented with sudden deafness including 110 Japanese and 77 Chinese were statistically investigated. We compared the background of Japanese patients with Chinese, and no significant differences were observed in the ratio of 1) gender, 2) age, 3) vertigo, 4) number of days from onset to start of treatment, 5) season of disease onset, or 6) average hearing level and difference between high tones and low tones of audiograms obtained at the first medical examination. Recovery ratio was almost the same, in spite of the difference of treatment. We estimated several factors for prognosis by analyzing all data statistically. Factors which indicate good prognosis for sudden deafness were 1) absence of vertigo, 2) low-frequency hearing loss pattern of audiogram, 3) the age less than 50 years, 4) the earlier start of treatment and the hearing level under 60dB at the first medical examination. In particular, for early treatment, our study suggested that healing ratio of hearing was 42% and effective recovery ratio of hearing was 62% if treated within three days of onset, and 85% of patient showed hearing recovery if treated within five days.