Recently, it was reported that the basilar membrane (BM) was slightly fluctuating without any acoustical stimulation, and this has been speculated to be caused by the outer hair cell fluctuations. However, no studies of the effect of BM fluctuations on TEOAEs have been carried out. Is this study, we investigated this effect by two approaches. One is numerical simulations using the mathematical model of a cochlea, which takes account of the BM fluctuations, and the other is measurement using ILO92. The simulation results demonstrated that the sound pressure which came out as a result of the BM fluctuations could be cancelled by averaging and have no effect on both levels and latencies of the TEOAEs. Additionally, the measurement results revealed that the BM fluctations-induced sound pressure was smaller than the cardiovascular or respiratory noise.
In fifty cochlear implant patients, the correlation between the speech sound discrimination ability in monosyllbles, speech intelligibility in words and sentences was evaluated with auditory only (A) and combination of auditory and visual modality (A+V), using video materials and live voice. There was significant correlation (p<0.0001) between results with video material and live voice, and the results with live voice were higher (1.7-16.2%) than those with video material. The test with live voice suggested that the disadvantage for quantitative evaluation but the advantage for the evaluation of change of the speech perception ability.
By near-infrared spectroscopy (NIRS), the changes in the local concentrations of oxygenated (oxy-Hb), deoxygenated (deoxy-Hb) and total hemoglobin (total-Hb) are measured. NIRS was used as a non-invasive functional brain mapping method of near-threshold auditory responses. Bilateral auditory areas of 14 healthy subjects were studied with a 24-channel NIRS optical topography system (ETG-100, Hitachi Medical Co.) during attentive hearing of toremolo bandnoise (0.5, 1 and 4kHz, 0 and 30dBSL) and of 1kHz tremolo tone (0 and 30dBSL), and non-attentive hearing of 1kHz bandnoise at 0dBSL. A combination of significant changes of oxy-Hb and total-Hb, or of deoxy-Hb and total-Hb, was observed in the attentive hearing of bandnoise even at 0dBSL in all the subjects. A significant response was also observed to 1kHz tone at 30dB above threshold, although only two out of five subjects showed a significant change of Hb concentrations in response to 1kHz tone at 0dB. In the non-attentive condition, a significant response to 1kHz bandnoise was observed in 80% of the subjects.
Despite good knowledge of the key symptoms of acoustic neuroma (AN) such as hearing loss and tinnitus, there has been only a few studies concerning ear fullness in AN. In addition, the pathophysiology of ear fullness remains to be established. In the present study, we investigated the incidence of ear fullness and the relationship between ear fullness and the audiological test results in 268 AN patients. The incidence of ear fullness was 34% in AN, and 6% of AN patients complained of ear fullness as an initial symptom and 5% as a chief complaint. However, there was no significant relation between ear fullness and the audiological test results. Further studies will be needed to clarify the pathophysiology of ear fullness in AN patients.
The aim of this study is to validate automated ABR (AABR) with ALGO2e, using conventional signal-averaged ABR, and to compare AABR with transient evoked otoacoustic emissions (TEOAE) for a universal hearing screening. As our purpose of this screening is to identify neonates with a bilateral, permanent hearing loss, we regarded bilateral fail as “fail”. 49 full-term neonates were tested by hearing screening test, including AABR, TEOAE and conventional ABR. Successful screening in the nursery without sedation was achieved for 100% of infants by AABR, but for 97.9% by TEOAE. The specificity of AABR was 97.9% and that of TEOAE was 93.6%. We could not evaluate the sensitivity, because neonates with bilateral hearing loss were not identified in this study. The mean test duration of AABR was 6min. 27sec. and that of TEOAE was 12min. 36sec. Because of its high sensitivity and its short test duration, AABR was more suitable for newborn hearing screening than TEOAE and conventional ABR. But, if one-month-old infants are tested in a quiet room at health examination when there is no influence of debris in the ear canal and middle ear fluid, TEOAE will be suitable, too. On comparison of AABR with cnnventional ABR, a unilateral referral ear of AABR failed conventional ABR on the same side, too. But one neonate who referred AABR passed conventional ABR. The results indicate that further analysis on the sensitivity is needed, and AABR is somewhat reliable, but there may be false-positive cases.
We investigated the maximum dissociation levels (C-I gap) of 10 patients received cochlear implantation at the age of 37 to 70 years old. The C-I gap was obtained for each patient by Bekesy audiometry test of pure tone of fixed signals and of continuous signals. Results indicated that the patients of a longer period of deafness had a greater C-I gap. Postoperatively, the dissociation gradually decreased, but the patients who experienced a longer period of deafness needed a rather long time to reduce the dissociation.
Auditory brainstem responses (ABR) are useful for the diagnosis of vestibular schwannoma in patients presenting sudden hearing loss. However, it is difficult to detect the existence of retrocochlear impairment in patients with severe or profound hearing loss by ABR. In this study. We evaluated clinical courses and auditory examination on 23 patients with vestibular schwannoma who had severe or profound hearing loss with acute onset. Only three patients suffered from vertigo at the onset of hearing loss. This finding may result from the vestibular compensation by a slow growth of tumor. Concerning prognosis of hearing, recovery to the normal level, marked improvement, slight improvement, and no change were observed in 1, 2, 1, and 19 cases, respectively. Electrocochleography was performed in 13 patients. One patient with hearing recovery to the normal level had normal cochlear microphonics (CM), suggesting normal cochlear function, However, in eight of nine patients with no change of hearing, CM detection thresholds were moderately to severely ellevated. Accordingly, irreversible cochlear dysfunction may result in poor hearing outcome.
Acute low-tone sensorineural hearing loss (ALSH) with sudden onset has some special characters compared with sudden deafness and Meneier's disease. We studied 70 patients of ALSH without dizziness, who visited our department between 1971 and 1995. These patients were investigated and followed up more than six months by repeated audiograms. We found the characteristics of ALSH as follows: 1) Approximately 60% of ALSH were featured by undefinite clinical onset. 2) Hearing recovery can be expected even if the treatment was not initiated soon after the onset. Approximately 60% of ALSH, who had interval more than a month before the treatment initiated, achieved some extent of recovery. 3) Recurrence of the low-tone hearing loss was observed in 24% of the all patients. 4) Among the patients with recurrence, approximately 88% can still achieve some extent of recovery. 5) Hearing can be variable throughout all frequencies in 23% of the all patients.