The auditory steady-state response is evoked by amplitude-and frequency-modulated tones (AM/FM tones), and by the relatively frequency specific tone. The Audera® system objectively detects the thresholds of auditory steady-state responses and reproduces frequency-specific hearing patterns in the form of audiograms. The optimal AM/FM tone varies with a subject's age, consciousness level (alert or sleeping), and target frequency. If these conditions are carefully selected, however, the Audera® will generate the optimal AM/FM tone and predict the value of the pure-tone hearing level. We used this system to examine 15 adult subjects with normal hearing. The results were as follows: 1) for sleeping subjects, the Audera® system could predict the subjects' pure-tone hearing levels; 2) for alert subjects, Audera® could predict the pure-tone hearing levels of the subjects only at 250Hz and 500Hz; 3) when the setup for alert subjects was used, even if they were sleeping, the Audera® could predict their pure-tone hearing levels at 250Hz, 500Hz, and 1000Hz; and 4) These prediction values were reproducible. Consequently, we found that the pure-tone hearing prediction accuracy of the Audera® changes with the environment and measurement method on subjects with normal hearing.
To discuss the intracranial source and the organizing mechanism of amplitude modulation following response (AMFR), an analysis of waveforms, a simulation study for the power spectral analysis of the waveform, and a comparison of the spectral amplitude of signal and noise level (calculated from the mean ±3SD of the spectral amplitude of the six frequency components around the signal) were performed. Though the waveforms of 40-Hz AMFR were similar to the sine waves, those of the 80-Hz response resembled the train of wave V of ABR or slow ABR. According to the findings of the spectral amplitude analyses, the differences in the detectability of the 40-Hz and 80-Hz responses in different arousal states (waking and sleeping) were explained as follows. The lower detectability of the 40-Hz response during sleeping was likely due to a reduction in the signal, where as the higher detectability of the 80-Hz response during sleeping probably originated from a reduction of the noise level, while the amplitude of the signal was sustained, compared with that in the waking state. Based on the above findings, the origin of the 40-Hz AMFR was thought to be MLR and that of the 80-Hz AMFR was thought to be ABR. However, the cochlear nucleus is also a candidate for the source of the 80-Hz response.
We investigated the actual conditions of the Newborn Hearing Screening program in Mie prefecture using a questionnaire sent to obstetricians and otorhinolaryngologists. The screening was performed and was planned to start in 56.6% of the maternity clinics in Mie prefecture. The obstetricians were requested to provide a system of identification and intervention for infants who failed the screening. About 60% of the otorhinolaryngologists did not have sufficient information about the screening program. They needed more information about the screening and the system used to identify hearing impairment in infants. Among the 21 infants who were referred to us based on the results of the screening, bilateral hearing loss was discovered in 7 infants and unilateral hearing loss was found in another 7. After completing this survey, we developed a set of screening guidelines for otorhinolaryngologists. The need for further examination after the initial screening should be based on the sufficient knowledge and consensus of all the otorhinolaryngologists. This guideline includes a parent inrerview, an examination for the diagnosis of hearing impairment in infants, and recommendations for early parental intervention in infants with hearing impairment up to 6 months of age. In the future, the efficacy of these guidelines should be monitored to continuously provide updated information to otorhinolaryngologists. At the same time, closer communication between otorhinolaryngologists and obstetricians must be established, and systems for intervention must be improved.
The reference equivalent threshold force level (RETFL) for Japanese bone conduction speech audiometry has not been reported, and the tentative recommendation in the JIS T1201-2 (2000) is 6dB different from the international reference specified in IEC60645-2 (1993). To examine the validity of the Japanese standard, the vibratoy force levels of three types of audiometric bone conduction receivers corresponding to the mean speech recognition threshold for single digits included in the 67-S Japanese speech audiometric test were measured in 20 otologically normal listeners. And then compared with the RETFLs in both standards. Although each of the three levels was within 2.5dB of the recommended RETFL for speech in the JIS T1201-2, statistically significant interreceiver differences existed up to 4dB. These differences were considered to originate primarily from inter-receiver differences in frequency response and, for one receiver, from sound radiation from the bone vibrator. These findings indicate that the RETFL for speech must be determined for individual receivers in instances where the frequency response of the bone conduction receiver is not specified.
Twenty out of 26 patients undergoing tinnitus retraining therapy (TRT) were evaluated after 6 months of treatment. Counseling and sound therapy using a tinnitus contror instrument (TCI) were used. Fitting of the TCI was performed every month. Fifty-five percent of the patients selected speech noise, and the noise level was varied for 3-month period. An interview regarding the effectiveness of TRT indicated that the treatment was effective in 55% of the patients, slightly effective in 25%, and not effective in 20%. None of the patients, conditions were aggravaled by the treatment. An improvement rate of 80% was obtained in the group that received the full treatment; the overall improvement rate was 61.5%. A reduction in the average scores for awareness of tinnitus loudness and the level of annoyance occurred after 3 to 4 months of treatment; these reductions were correlated with the effectiveness of TRT. TRT must be performed for 3 to 4 months to properly fit the TCI and assess the effectiveness of TRT in patients with tinnitus.
We investigate the qualitative effects of wearing cochlear implants in two adults who developed acquired profound hearing impairment at different stages in their lives: in infancy and during adolescence. We recorded and examined narratives with the patients as part of their rehabilitation over a period of 2 years and 6 months. The results were as follows: 1) With regard to speech communication, both of the patients described an obvious improvement in their ability to recognize the “speaker's vitality affect” and “meta-communication”, or the ability to recognize a proposition through changes in speech patterns. The patients attributed these improvements to better recognition of supra-segmental features in speech, like rhythm, accent, speech interval, voiced pauses, etc. 2) Improvements in the ability to hear natural environmental sounds, especially sounds associated with special aspects of Japanese society or culture, (e. g, feeling the arrival of spring after hearing the song of a Japanese nightingale) contributed to a subjective improvement in the patients' quality of life. 3) Differences in age at the time of hearing-impairment onset might affect the quality of social-cultural experiences, with substantial improvements, achieved through the use of cochlear implants.
The clinical features of acute low-tone sensorineural hearing loss (ALHL) were examined in 274 patients treated at our hospitals. One-handred and thirty-one patients received a Glyceol test and were included in the final evaluation. Seventyseven out of 131 patients (53%) reaived a positive Glyceol test result (a hearing improvement of 2 or more frequencies) We examined the relation between the Glyceol test results and the final hearing. outcome. Our results indicated that patients with a clear reaction on the Glyceol test tended to have a better prognosis. Isosorbide was administered to 96 out of the 274 cases. A significant difference was not observed between outcome and the administration of Isosorbide in all the cases. However, when the subjects were limited to patients who showed a hearing improvement of 3 or more frequencies on the Glyceol test, the administration of Isosorbide and a favorable outcome were correlated. Our results suggest that endolymphatic hydrops may be involved in the mechanism of ALHL. In cases where a strong contribution of endolymphatic hydrops is suspected, favorable prognosis and response to Isosorbide administration can be expected.
Acute low-tone sensorineural hearing loss is defined by the following criteria: the sum of hearing levels at low-tone frequencies (125, 250 and 500Hz) must be 70dB or more and that at high-tone frequencies (2000, 4000 and 8000Hz) must be 60dB or loss. However, several studies have suggested that a similar etiology exists among patients in whom the sum of hearing levels at high-tone frequencies is 65dB or more. We compared the epidemiological characteristics of typical cases meeting these criteria to those of atypical cases, whose hearing levels exceeded 65dB at high frequencies. All the subjects had unilateral hearing loss (317 typical cases and 91 atypical cases); all patients were registered in nationwide epidemiological surveys conducted between 2000 and 2002. Many similarities in the epidemiological characteristics of the two groups were seen (more prevalent in females that in males and in spring/summer than in winter; hearing recovery depended on initial hearing level; severity of hearing loss at low-tone frequencies), but several differences were also noted (levels of hearing impairment at middle to high-tone frequencies; correlation of prognosis with age and the number of days from onset to the first examination), suggesting differences in the pathophysiological features of typical and atypical cases.
Fabry disease is a rare X-linked recessive glycosphingolipid storage disorder that is caused by a deficiency of the lysosomal enzyme α-galactosidase A. This deficiency leads to widespread glycoshingolipid deposition in the endothelial and smooth muscle cells of the microvasculature throughout the body. Clinically, affected patients suffer from ischemic complications involving brain and heart as well as chronic renal insufficiency. A few reports have mentioned cochlear involvement in Fabry disease. Here, we present two cases with Fabry disease. A 51-year-old male experienced a sudden hearing loss on the different occassions. He was diagnosed as having Fabry disease during a follow-up examination for chronic renal failure. A 47-year-old female exhibited a high frequency sensorineural hearing loss. Analysis of SISI and Bekesy test results showed inner ear hearing loss in both cases. We hypothesized that sudden hearing loss may be caused by vascular mechanisms as a result of the accumulation of glycosphingolipids within endothelial and smooth muscle cells, leading to ischemia and frank occlusion in the vessels feeding the cochlea. Slowly progressive hearing loss might be caused by the accumulation of glycosphingolipids within the spiral ganglion cells or cochlear vessels. Fabry disease should be included in a differential diagnosis of unexplainable sensorineural hearing loss with renal insufficiency.