The increase in sound pressure level in the ear canal when wearing a hearing aid is known to be different from the 2cm3 coupler gain of the hearing aid. In this study, the real-ear coupler difference (RECD) was measured in 44 otologically normal adults for comparison with the results of previous studies, among which considerable differences were noted. For real ear measurement, the probe microphone was placed within 2mm of the ear-drum. The reliability and validity of RECD measurements were also evaluated. The mean values of RECD were comparable to those reported by Seewald et al. (1993), within 3dB at 7 frequencies ranging from 0.25 to 6kHz. Intersubject differences were within 2dB in SD at frequencies below 4kHz. The mean unsigned testretest variability for RECD was a little over 1dB at middle frequencies between 0.5 and 4kHz. The mean unsigned prediction errer of real-ear aided gain was within 5dB at frequencies below 3kHz when individually measured RECD was used. This error was not less than that when averaged RECD was used for the prediction. Based on the above results, in spite of its importance for children and cases involving abnormalities in the conduction system, individual measurement of RECD was considered to be of little value for adults with normal conduction systems as long as the accuracy of measurement is not improved.
Several investigators have proposed an equation to predict the average hearing level of age effect. Recently, the ISO have also published a new formula. According to my recent investigation, however, these equations are not fully adequate for predicting the hearing loss of age effect. The purpose of this paper is to offer a new formula for predicting the age effect which is more accurate than the formers.
New criteria have been propose for acute low-tone sensorineural hearing loss (ALHL) by the Research Committee on Acute Profound Deafness of the Ministry of Health, Labor and Welfare of Japan, and nationwide epidemiological surveys based on these criteria were conducted in 2000-2001. We especially investigated recurrent cases of ALHL. The results in 96 cases, including 5 cases of bilateral hearing loss were analyzed for two years. All curative percentage of recurrent cases about full recovery and better recovery in regard to the criteria is 68%. The outcome of hearing was better in patients who consulted a physician within a week after the onset of the recurrence. No significant differences were noted in other factors, i.e., sex, age, severity of hearing loss at the time of the examination for recurrence or recurrent time during the first attack. The specification of recurrent cases is that the percentage of cases cleared for the criteria at recurrent attack (cleared at first attack) are about 60% in recurrent cases.
We used DPOAE and AABR to screen newborns (all well babies) and one-month-old infants for hearing disorders. Initially only newborns were enrolled in the study, but because the pass rate for screening (64.7%) by DPOAE alone was low, we switched to one-month-old infants as subjects. The pass rate of the one-month-old infants was higher than that of the newborns (94.1%), and repeated examinations improved the pass rate. Finally, the use of AABR in addition improved the pass rate even more (99.1%). Screening of the one-month-old infants was carried out without major problems. From the standpoint of the relationship between mother and infant, management, counseling and early intervention, the screening at one-month-old infants seemed more useful than the screening of newborns. A hearing screening amd early intervention system based on agreement among medical staff members, public health nurses, educators, and counselors is needed. Adjustment of the general environment from pregnancy to infant care support is also important.
To investigate the effects of ventilation tube insertion on acoustic emissions in children diagnosed with otitis media with effusion, transiently evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) were measured in normal-hearing ears with a ventilation tube inserted (ventilation group, 14 ears) and in normal-hearing ears with an intact tympanic membrane (normal group, 11 ears). Both the TEOAEs and DPOAEs were clearly detected in the ventilation group, although the echo power of each was slightly smaller in the ventilation group than in the normal group, and the DPOAE noise levels were somewhat higher in the ventilation group than in the normal group. In addition, both the total echo power and whole-wave reproducibility of the TEOAEs in the ventilation group were as high as in the normal group, and the difference between the two groups was not statistically significant. We concluded that it measuring otoacoustic emissions after ventilation tube insertion is worthwhile as a method of assessing hearing ability in children.
Effect of AMPA (a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid), a glutamate agonist, on the compound action potential (CAP) and endocochlear DC potential (EP) was investigated in gerbils. AMPA 100μM, AMPA 200μM, sucrose 200μM, and artificial perilymph were administered via Gelfoam placed on the round window membrane. Artificial perilymph or sucrose 200μM did not markedly change the CAP threshold, but it gradually increased in response to AMPA 100μM or 200μM. EP, on the other hand, did not change markedly after administration of artificial perilymph or AMPA 100μM, but it decreased after administration of AMPA 200μM and sucrose 200μM. These findings suggest that the stria vascularis is not influenced by glutamate excitotoxicity, which devastates the inner hair cells and the spiral ganglion neurons. The decrease in EP in the AMPA 200μM group appears to have be due to the high osmotic gradient of the solution.
The purpose of this study was to retrospectively investigate the degree of coincidence between a secular change in auditory brainstem evoked responses (ABRs) and the conditioned orientation reflex audiometry (COR) findings in 229 multiply handicapped children with motor disorders. The subjects were all less than 3 years old and had been observed for a period of more than 2 years at the time of the first hearing evaluations. Improvement in Behavioral Hearing Testing minimum response level, including mental and physical development, was observed in 111 cases. There were 92 cases of ABR, and in 37 of them there was no correlation between the ABR and COR findings. The initial diagnosis in 44 patients was moderate to severe hearing loss, and a secular change was observed in 37 of them. The ABR thresholds and the COR minimum reaction level decreased in 11 patients, whereas in 17 patients ABR thresholds remained unchanged and only the COR values decreased. The final diagnosis was moderate to severe hearing loss in 18 patients. Because confirmation of the efficacy of hearing aids takes a lond time and there are fluctuations in hearing levels during the observation period, periodic assessment of hearing is important, using evaluations of mental and physical development as a base.