Stapedius reflex, static compliance, type of mpanogram and shift of pressure peak were exa ined before and after tubal inflation for a total of 1 ears of 97 adults aged from 21 to 87 years for jective evaluation of the effect of tubal inflation nd for predicting presence or absence of middle ear fusion in the cases in which air-fluid level was not etected otoscopically. Concerning the judgement of the effect of tubal flation, change of type of tympanogram was found seful for the cases with type B and C before infla on, and pressure peak shift for those with type A efore inflation. The efficacy was 80.0 and 100% espectively for the cases with type B and C before flation which altered to type A after inflation. n the cases with type A before inflation the efficacy f tubal inflation varied with the extent of pressure eak shift, and it was proved that the tubal inflation was always useful when the pressure peak shifted toward positive pressure exceeded 35mmH2O. The change of tympanogram type before and after inflation could predict the presence of effusion in the middle ear, and the cases with type B before and after inflation were suspected of the presence of effusion, but tympanostomy was not necessary in the cases with type A after inflation unless air-fluid level was observed.
Acoustic impedance measurement was routinely performed in 18 healthy infants during the first year of life using both Madsen ZO-72 and Grason-Stadler 1722. Most of the data were obtained while the infants were asleep with sedatives. The measurement was more difficult in this age than in neonates. AD type tympanogram, which was predominant in neonates, was reduced with increasing age, and was not obtained after the fifth month, on the other hand, AW (wide A) type tympanogram, which was defined as type A with relative gradient of 0.15 or less, was prominent from the fifth through ninth month. Mean middle ear pressure did not vary through out the first year of life, and there was a dispersive tendency of the data with age. During the first six months the relative gradient decreased with age, while the latter half of the year it was nearly constant. Static compliance was high in the first three months and decreased after wards to come to be in plateau from the fifth month Stapedial reflex was positive in 67 percent even in the first month old babies.
A 45-year-old house wife with hemifacial spasm developed a profound sensorineural deafness after neuro-vascular decompression operation of the facial nerve at cerebellopontine angle. Electrocochleography was performed using the transtympanic electrode technique. The results obtained were as follows: The wave form of action potential (AP) showed a broad pattern and a low amplitude, but AP threshold was remarkably lower than that of pure tone audiogram. The cochlear microphonics showed the well-developed responses. The above findings seem to indicate that the organ of Corti was found to be functioning because of the preservation of blood supply, but the first neuron region or spiral ganglion cell region was impaired partially and retrogradely, by the surgical procedure on the eighth cranial nerve.
Measurement of maximum and minimum diameter of the superficial blood vessels was performed to clarify the effect of intraduodenally administered ATP on the vascular system of the inner ear. ATP was given to 20 guinea pigs intraduodenally at dose of 30, 100, 300 and 500mg/kg respectively. Physiological saline solution was given to 5 control animals. The animals were sacrificed and decapitated 15, 30, 60 and 90 minutes after the ATP administration. Benzidine reaction was made on the formalin fixed cochlea and vestibule to demonstrate the configuration of the blood vessels. The measurement of the blood vessels was conducted on the photomicrographs at the same magnification. The following results were obtained. 1) The increase in the diameter of the blood vessels was observed in radiating arterioles, suprastrial capillaries and stria vascularis in every turn of the cochlea and in capillary network of the ampullar cristae as well as maculae of the vestibulum in the guinea pigs. 2) The increase in the vascular diameter showed dose dependency, and began to appear at dose of 100mg/kg and became maximum at dose of 500mg/kg. 3) The increase in the vascular diameter was most prominent 15 minutes after the administration of ATP at dose of 500mg/kg and then became decreased gradually to normal value 90 minutes later. 4) These findings suggest that the effect of ATP on the vascular diameter may persist longer in intraduodenal administration than intraperitoneal administration.
The auditory post-auricular responses in children were studied to evaluate its clinical use. The positive responses in awaked children were observed in over 50%, 92.5% and 100% at the intensity levels of 20, 40 and 80dB respectively. The probability of positive response was higher than that in adults, and was consistent in each ear and between both ears in each individual at the intensity levels of above 50dB. The response was low in sleeping children even when high intensity stimuli (80dB) was used. As the results, this response can be applied in clinical practice as a screening test of hearing in children, which is simple and easy to perform, and further, painless and acceptable to children without sedation.
Spectral components of ABR as a function of stimulus intensity and stimulus interval were measured in 10 adults with normal hearing. At higher stimulus intensities, three peaks were observed at 0-100, 500 and 900Hz in the spectrum, of which the most prominent peak was around 100Hz. However, this dominancy of the low frequency components disappeared when the corresponding spectrum of spontaneous brain activities was subtracted from the response spectrum. With decrease of stimulus intensity, the power of all spectral components was regularly diminished. The power of low frequency spectral components up to 500Hz was kept unchanged with various stimulus intervals from 125ms to 11ms, while the power of higher frequency components tended to decrese with decreasing stimulus interval.
Peculiar type of unilateral hearing impairment was noted in two patients who had subacute onset of dizziness and hearing loss. The first case was a 33-year-old man in whom neurological examination revealed left facial paresis and hypesthesia in addition to left cochleo-vestibular nerve disorder. The second case was a 30-year-old man who demonstrated right cochleo-vestibular nerve disorder. Although almost normal pure tone audiograms were obtained in both of them, Bekesy audiometry demonstrated type III or IV tracings in the affected ears. Acoustic reflex showed ‘reflex decay’ at 1000Hz stimulus and a marked decrease in the amplitude of the reflex at 500Hz stimulus in the first case. The second case had poor speech discrimination scores of 60% in the affected ear. Caloric tests demonstrated markedly decreased response in the affected ears of both cases. The results of audiological tests and caloric tests indicated the eighth nerve lesion in these cases. Their hearing impairment was gradually recovered, and the audiological test results in consistent with the retrocochlear lesion was not observed three to four weeks after the onset. Neuroradiological findings showed less probability of space occupying lesions in these two cases. Serological tests showed no evidence of virus infection. The etiology and lesion in these cases were not yet determined, however, the presence of temporary disorder of the eighth nerve could be suggested.
Speech discrimination scores can be affccted by frequency characteristics of the auditory systems ie. pure tone audiograms of hearing impaired patients. This may be one of reasons why it is difficult to determine the site of lesion in the auditory pathway by speech audiometry. In order to evaluate the effect of pure tone audiograms, the authors propose the application of a digital filter to simulate the abnormal frequency charactoristics of the ear in this paper. (1) The results obtained by digital filter were compared with those from the analog filter which has usually been applied. Digital filters are superior to analog ones at some points such as signal to noise ratio, flexibility of design and stability of frequency characteristics etc. (2) The effect of finite impulse response (FIR) digital filter was compared theoretically with that of the infinite impulse response (IIR) digital filter. It was concluded that the FIR digital filter was better than the other because any pure tone audiograms could be approximated by this filter with linear phase. The FIR digital filter used in this experiment was designed by a window method, and filtered speed sounds were produced to simulate the abnormal speech perception of patients and presented to the normal hearing subjects. The results from this procedure were compared with those obtained from the patients. In conclusion, the FIR digital filter is useful to simulate the frequency characteristics of the auditory systems.