A new method for the electro-magnetic coupling for an extracochlear prosthetic device was designed in order to transmit signal from the outside of the body to the inside. The coupler consists of a primary coil, the secondary one made of tiny chip coils and the limiter made of chip FETs to avoid the excessive current. The primary coil was placed in the earmold and the secondary one was set under the skin of the external ear canal. The size of the secondary circuit was small to be implanted. The secondary part implanted into the body was coated with medical grade silicone rubber. It was placed in a saline solution at 36°C to check its electrical stability. The electrical characteristics were extremely stable during six months. To investigate the efficacy of the coupler, the cochlea of a guinea pig was stimulated by output current pulses produced from the secondary part. The compound action potentials (CAPs) elicited from the auditory nerve bundle were compared with the CAPs evoked using a stimulator with/without the isolator. It was proved that our device could stimulate the auditory nerve similar to the other stimulators. Our method is easily applied to a deaf child because it can be put on or taken off without damaging the inner ear or the skull.
A comparative study on the results with the whispered voice test by pointing pictures and pure tone audiometry was undertaken on 359 patients from 3 to 65 years of age. The results obtained were as follows: 1) It was suitable for children from 3 years of age and adults to be tested with the closer whispered voice test by using two groups of words having each different acoustical characteristics. And the test had remarkable availability to detect whether the hearing loss was under 30dB or not at all the frequencies of 1000, 2000 and 4000Hz. 2) The simple whispered voice test by using easier listening words was suitable for children with unstable listening. And it was concluded that the test was very effective to detect whether the hearing acuity affect his development of language or not.
Xeroderma pigmentosum is a skin disorder characterized by excessive sensitivity to ultraviolet light resulting in atrophy of exposed skin in childhood with the development of pigmentaion and malignant change. Especially the patient in group A has other neurological defects; progressive mental retardation, motor disturbance, and hearing impairment. In this paper the hearing impairment process and speech and language process are described in a 8-year-old patient who had xeroderma pigmentosum group A. By the age of 7 years 2 months, threshold in his right ear was within normal range. However, in his left ear hearing loss was already 63dB. At the age of 7 years 5 months he had sudden decrease of hearing on the right ear. His hearing impairment progressed independently in each ear. He began to use a hearing aid at the 7 years 5 months. The effect of hearing aid has comparatively satisfactory. Routine audiometric assessment suggested that the hearing loss was of a sensorineural type suggestive of a cochlear and retrocochlear lesions. His IQ was less than 45 at the age of 7 years 2 months, when threshold in his right ear was nearly in the normal range. Therefore it was suggested that his mental deterioration preceded his hearing impairment.
In your children, it appears that there is no advantage in recording steady-state response (SSR) at a stimulus rate of 40Hz. To determine the optimal modulation frequency (MF) in auditory SSR evoked by sinusoidally amplitude-modulated (SAM) tones (Amplitude-modulation following response: AMFR) in children during sleep, AMFR was examined in 3 normal adults while awake and during sleep and in 3 normal children during sleep. The stimulus was 1000Hz, 50dBnHL SAM tone with a modulation depth of 95%. MF was varied from 20 to 200Hz in 20Hz intervals at a time. Response was determined by calculating spectral amplitudes at frequencies near that of the stimulus using FFT and by phase spectral analysis. Although AMFR was evoked only by MF of 40Hz in adults while awake, AMFRs to MFs of 80 and 100Hz were detected during sleep in addition to the 40Hz AMFR. In children, 40Hz AMFR was difficult to detect but response could be clearly detected at higher modulation rates (80-200Hz) compared to the response in adults during sleep. Modulation frequencies from 80 to 100Hz would thus appear optimal for detecting AMFR during sleep in young children.
Interpeak latencies of abnormal auditory brainstem response (ABR) in both positive and negative components were investigated. The subjects were 211 adult ears which revealed prolonged I-III or I-V IPL of positive components and 219 adult ears which revealed prolonged I-III or I-V IPL of negative components. And detectability of wave I, wave III, and wave V of both polarity and their IPLs were studied. The subjects were 500 adult ears including those with normal ABR. The results were as follows: 1. Among those cases their IPLs of positive components prolonged, 36.3% of I-III IPLs and 32.0% of I-V IPLs of negative components were within normal range. 2. Among those cases their IPLs of negative components prolonged, 23.1% of I-III IPLs and 16.8% of I-V IPLs of positive components were within normal range. 3. IPLs of ABR were able to be evaluated by negative components even if their positive components were not detected. 4. Not only positive components but also negative components of ABR provide us significant informations when we apply ABR for the evaluation of brainstem disorders.
The speech discrimination scores of a 57S word list were analyzed in 180 patients with sensorineural hearing loss. The speech discrimination scores ranged from 30% to 88% in the subjects. Discrimination scores of voiced consonants and nasal consonants were worse than those of other consonant groups. In contrast, the discrimination scores of voiceless consonants, vibrant consonants and semivowels were better than voiced and nasal consonants. The subjects of this study could be classified into three groups according to the most consonants among the voiceless, voiced and nasal consonants. Patients with sensorineural hearing loss should be classified according to consonant confusion for individual fitting of a hearing aid to improve the speech discrimination scores.
Since October 1990, screening tests for detecting hearing impairment in 3-year-old children has begun. A comparative study on the hearing impairment of 3-year-old children was undertaken in oder to investigate similarities and differences obtained by test results with play audiometry, whispered voice test, etc. The results were as follows: (1) Three-year-old children could be screened for hearing loss equally as well with the whispered voice test as with pure tone play audiometry. (2) The behavior observation audiometry screening test could not be used to find hearing impairment of 3-year-old children. The whispered voice test was useful for detecting moderate hearing impairment in both ears. (3) The words of the whispered voice test by Nakayama were effective for finding low frequency hearing loss. (4) It was difficult to discover unilateral hearing loss using the whispered voice test.
The accuracy of screening hearing test for regular physical examination was analyzed by the comparison between the results of screening hearing test and those of standardized pure tone audiometry. The subjects were 147 persons (124 males, 23 females) which showed no response against the test pure tone of either 30dB at 1kHz or 40dB at 4kHz produced by screening audiometer. The results obtained were as follows; 1) The results of screening hearing test and those of standardized pure tone audiometry corresponded in all 4 test frequencies in 91 subjects out of 147 (61.9%). 2) The results of screening hearing test and those of standardized pure tone audiometry corresponded in both 1kHz and 4kHz in 224 ears out of 294 (76.2%). 3) The accuracy of screening hearing test was 89.1% at 1kHz and 82.0% at 4kHz. 4) The accuracy of screening hearing test was higher in males than in females. 5) The age of the subject did not affect on the accuracy of screening hearing test. 6) There was no remarkable difference of the accuracy of screening hearing test in both ears. 7) The more the test frequencies with no responses in screening hearing test were, the lower the accuracy was. 8) The false negative rate at test frequencies with positive responses in screening hearing test was only 0.5% at 1kHz and 8.5% at 4kHz. 9) The false positive rate at test frequencies with no responses in screening hearing test was 27.7% at 1kHz and 25.5% at 4kHz. 10) Based upon these results, it was concluded that the factors affecting on the accuracy of screening hearing test included test frequency, sex of the subject and the number of test frequencies with no responses. Also, it was suggested that the main factor inducing the deterioration of accuracy of screening hearing test was the false positive rate at test frequencies with no responses but not the false negative rate at test frequencies with positive responses.
The reliability of CNV (contingent negative variation) audiometry with 2dB steps upon tinnitus patients with hearing loss was investigated. In 15 tinnitus patients the thresholds of hearing were determined with two different methods simultaneously, CNV audiometry, the first stimulation by sound and the second stimulation by illumination, and pure tone audiometry using method of limits. The reproducibility of CNV audiometry in measuring the thresholds of hearing within three consecutive trials, and also the differencies of threshold in CNV audiometry and pure tone audiometry were investigated. Because stabilized CNV waves were obtained in 12 out of 15 patients, the following analysis was done in these 12 patients. The thresholds of CNV audiometry obtained from three consecutive trials showed the same findings in 10 out of 12 patients. However in the other 2 patients the thresholds of CNV audiometry were fluctuated in the reproducibility within the range of ±2dB. The threshold differencies of CNV audiometry from pure tone audiometry were -0.75±1.35dB, and a high statistical correlation between the threshold from CNV audiometry and pure tone audiometry was proved. Depending these results, it was concluded that CNV audiometry was reliable within the range of ±2dB as an error and CNV audiometry was useful as an objective audiometry.
Threshold shift of hearing level at the frequency of tinnitus during the tinnitus was suppressed by lidocaine injection was measured by audiometry using CNV (contingent negative variation) with 2dB steps. Because a measuring error of CNV audiometry was considered within ±2dB, a threshold shift more than ±4dB was thought to be significant. In the patients with tinnitus which was suppressed by lidocaine injection, 22% patients (11/49 ears) showed drops in threshold, 76% (37/49 ears) showed no change of threshold, however in the patient in those tinnitus had no change, 94% (28/30 ears) showed no change of threshold. Statistical analysis proved that the significant drops in hearing threshold were detected in the tinnitus suppressed group compared with in the tinnitus unchanged group. Still more these drops of threshold accompanied with tinnitus suppression were observed only in tinnitus frequencies, companied with that few threshold changes in the ranges except for tinnitus frequencies. From these facts it was considered that referring to the previous reports, the drop of the hearing threshold in the tinnitus frequency by lidocaine injection was induced by improvement of S/N ratio within the auditory pathway, because lidocaine specifically suppressed abnormal increasing spontaneous discharge rates, which was thought to be tinnitus, without reducing excitability by external sound.