Since the interaural attenuation (IA) value for bone conduction is almost 0dB, the bone-conduction component of the air-conduction signal transmitted to the opposite inner ear through IA for air-conduction must be transmitted to the simulated ear on the almost same level. Accordingly, an air-conduction signal is transmitted to the stimulated ear by two routes: the ordinary air-conduction route through air-bone gap of that ear and the bone-conduction route through IA for air-conduction. Comparison of these two transmission routes led to the conclusion that the value of the air-bone gap never exceeds the IA value for air-conduction, and this phenomenon will be referred to as “the law of IA for air-conduction”. The following relationships can be deduced from this law of IA. 1. The difference between the unmasked poorer air-conduction threshold and the unmasked better bone-conduction threshold never exceeds the IA value for air-conduction on condition that the air-conduction receivers are placed on both ears. 2. Shadow hearing (cross-hearing, transcranial hearing) of air-conduction occurs only when the above difference is equal to the IA value for air-conduction. 3. If the unmasked poorer air-conduction threshold of the test ear (tentatively referred to as “the initial threshold”) is the result of shadow-hearing by the opposite inner ear, the bone-conduction threshold of the test ear must be poorer than that of the opposite ear by at least the difference in air-conduction threshold between the initial threshold and the “true” threshold of the test ear.
Audiograms of sudden sensorineural hearing loss (SSHL) were discussed in 82 cases with complete recovery and 27 with no improvement. Results were summarized as follows: 1. The shape of the average audiogram of cases with complete recovery was bowl-shaped (all frequency affected) and of cases with no improvement was gradual sloping high tone loss. 2. The amount of hearing loss was additive with aging in the cases with complete rccovery, but not in cases with no improvement. 3. Strong similarities were found in the clinical pictures of the cases with complete recovery to the diuretic hearing loss. 4. It was suspected that the pathological process of SSHL with complete recovery may be in the stria vascularis. 5. The characteristics of acute strial hearing loss are: (i) sudden onset, (ii) complete recovery, (iii) bowl-shaped audiogram (all frequency affected) and (iv) additive hearing loss with aging.
The objective of this study was to evaluate outcome of a hearing screen program for well, full term babies in Japanese Red Cross Society Wakayama Medical Center. Two handred and fifty infants were tested in this study using transient evoked otoacoustic emissions (TEOAE) and distortion-product otoacoustic emissions (DPOAE). The TEOAE pass required the response of≥10dB or reproducibility of≥70%. The DPOAE were judged to be present if the DPOAE level was more than 2SD above the associated noise floor repeatable in 2, 3 and 4kHz. Of 500 ears, 42 ears (8.4%) failed TEOAE screening, and 60 ears (12%) failed DPOAE screening, respectively. The measurement of OAE was repeated in a follow-up examination after 4 weeks. Two infants failed OAF rescreening. If OAE were again absent, evoked auditory brainstem responses were measured. No infant was found to have hearing dysfunction. We conclude that time and experience are important factors in the development and refinement of a universal hearing screen program.
The second survey of ear injury caused by auditory canal impression in hearing aids fitting was conducted in 398 medical institutions and 815 hearing aids stores. The questionnaires were recovered in 63.3% and 79 medical institutions out of 263 (30.0%) reported ear injuries. As found in the first survey of 1986, there were bleeding and inflammation of the external ear and foreign bodies of impression material in the ear canal. Serous injuries such as middle or inner ear injury and penetration of the tympanic membrane were reported for the first time. At the removal of foreign bodies in some cases, a piece of material was left in the canal, and injury of the middle ear was occurred during operation. Previous examination by an otolaryngologist not only gives attention for hearing aids fitting but also gives clues for removed of foreign bodies of impression material. Therefore collaboration of the otolaryngologists and hearing aids stores in very important for hearing aids fitting. According to these results, ear injuries might have occurred during hearing aids fitting and in some cases which is the impression material will become a foreign body in the ear difficult to remove. It is necessary that hearing aids fitting should be conducted by the otolaryngologists.
In order to evaluate the usefulness of DPOAEs for universal neonatal hearing screening (UNHS), we measured DPOAEs in 1075 normal Japanese babies at one obstetric clinic and 4 general hospitals by using ERO/SCAN DPOAE screener (MAICO). Advantages of this device are autostart and capability of quick measurement, 7seconds at default basic mode. Overall referral rate was 4% at first stage and was down to 0.8% by two-stage screening. In about half of the babies, measurement was completed within 1minute in each ear including preparation time, and 80% of that within 3minutes. We concluded that the DPOAEs are useful in the relatively small Japanese obstetric clinics and hospitals in the view points of low cost, easy operation and accuracy. However, DPOAEs are quite new method for evaluation of deafness and PASS/REFER criteria has not yet been standarlized. Therefore, we must pay a carefull attention for evaluation of deafness by this device.
The scale was designed to assess the effects of auditory rehabilitation including hearing aid fitting. First we collected 303 items and after discussion on the content relevance, we selected 50 items for the first version. The questionnaire consisting of 50 items was tested on 266 patients wearing no hearing aids and 154 patients with hearing aids. The average age of the patients was 66.5±14.1 years and the average hearing level was 50.2±13.8dB. The factor analyses revealed 3 subscales: disability, handicap and communication strategy. In order to reduce the number of items in the questionnaire for clinical use, we selected 28 items based on the result of the pilot test. The relevance and reliability of the second version should be assessed in future.
153 newborns and 118 3-month-old infants were tested by using automated transient otoacoustic emissions (automated TEOAE) as hearing screening. The pass rate was lower than that by using automated ABR which we have reported before. But it was possible to improve the pass rate by re-testing. The instruments for screening should be selected according to the efficiency of each institution. Regarding the practice on the hearing screening, the newborns screening was carried out easier than the screening of 3-month-old infants. But considering referrals, follow-up, counseling and intervention, the screening of 3-month-old infants seemed to be performed more smoothly than the newborns screening by using the systems of the existing infants health examination. The hearing screening should be performed based on the agreement between medical staffs, health nurses, educators, counselors, etc. The systems for hearing re-check after the hearing screening should be also established.