Implantable microphone for total implantation of the cochlear prosthesis was developed by utilizing a piezoelectric ceramic element. As the ceramic element generates electric potential in response to the mechanical distortion of its bimorph structure, it can be used as a pick-up of the vibration of the tympanic membrane by touching it to the head of the malleus. The tympanic membrane works a diaphragm of microphone, and there is no need to implant a diaphragm. Therefore, by this method it is possible to design a miniaturized microphone for implantation. The ceramic element is good at durability and can easily be coated with biocompatible material with least reduction of its performance. Sensitivity and frequency response of this implantable microphone were studied with three human temporal bones preserved in 10% formaldehyde solution. The results showed that their best sensitivities in the three specimens ranged from-5 dB to -63dB re V/Pa for 1kHz, which warranted the possibility of this method in practical use.
Cochlear and brainstem responses evoked by ultrasonic vibration of 46.67kHz were recorded in 10 human subjects. The first peak of these responses resembling the wave I (AP) of acoustic ABR had the following remarkable characteristics. 1) The latency of this peak was considerably shorter than that of AP in ABR evoked by acoustic stimuli of the same intensity level above threshold. 2) The amplitude of this peak showed the higher resistance to the reduction of interstimulus interval than that of AP in ABR. It was concluded that 1) the perception mechanism of the ultrasonic vibration applied to the human auditory system may be quite different from the classical auditory perception theory, 2) the ultrasonic vibration-evoked cochlear and brainstem resbonse has a possibility of a valuable diagnostic lieasure in some cochlear pathology.
The diagnosis of the ossicular condition such as ixation or dislocation may often not be achieved by the routine tympanogram. This might be due to the facts that the routine tympanogram figurizes the impedance of the middle ear as an equivalent air volume without phase measurement, and frequency of the probe tone is quite tow and mostly 220 Hz. A new technique has been developed in our department in order to improve the diagnostic value. The method was consisted of the followings: (1) Frequency of probe tone was changed continuously from 45 Hz to 2500Hz. (2) The changes in sound pressure and in phase were measured continuously at the external meatus, as the frequency of the tone changed. (3) These values were figurized in a kind of polar notation as the difference between conditions of -200mmH2O and 0mmH2O, by the aid of a microcomputer. This system was applied for normal subjects and patients of otosclerosis and traumatic ossicular dislocation. Pre- and post-operative diagnosis agreed with each other. The authors feel that this new system should be routinely applied because of it's validity in clinical use.
Threshold shift due to neck torsion (positional one decay) in cases of vertebro-basilar artery insufficiency and in cases of cervical deformity was studied and discussed. The changes of the auditory threshold above 6dB were recognized in about 80% of the former cases, and about 70% of the latter cases. After stellate ganglion block, the threshold shift was disappeared. And the blood flow pattern of he vertebral artery by ultrasonic doppler method was extremely changed by the neck torsion in the above cases.
Difference in middle latency response pattern was studied between the vertex and the right and left post-auricular leads. And binaural interaction in M. L. R. was studied both in cats and human subjects. The experiment was proceeded as follows: M. L. R. to right and left monaural stimulations were added together, then M. L. R. to binaural stimulation was subtracted from it. The results were as follows: 1) There was no remarkable difference between the vertex and the post-auricular leads in normal cats, and cats whose unilateral inner ear was destroyed, and normal and unilateral deaf human subjects. 2) In cats binaural interaction was recognized within about 20msec. 3) In human subjects binaural interaction was recognized in the Po-Na components of M. L. R., however, the pattern of binaural interaction was variable.
In order to detect the generator of acoustically evoked middle latency responses (MLR), a series of animal experiments were carried out as follows; 1) cross-section of the brain 2) thermo-coagulation of the brain 3) lesion formation by contrast media via a etal catheter 4) compression and decompression using the allooning method. The results were as follows: 1) The generator of Na component of MLR was mainly located at the medial geniculate body contra ateral to sound sitmulus. 2) Pa component was generated from the thalanus, although the definite foci were not clearly entified. The succeeding components (Nb, Pb…) ere suggested to be generated from the widespread entral areas. 3) It was possible to detect the reversible modal ies of early components of MLR ballooning method. These experimental results of MLR suggest the possibilities of neurological application of this response.
The present study was undertaken to make the confidence of slow vertex response more reliable and a new trial for the testing procedure was investigated. In sequential averaging of original EEG, parts of EEGs following the odd-numbered triggers (1st, 3rd 5th, ……triggers) and those following the even numbered triggers (2nd, 4th, 6th, ……triggers) were averaged separately, and they were designated as odd-numbered averaged EEG and even-numbered averaged EEG respectively. These two averaged EEGs were relatively resemble each other in a point of view of the sleeping depth. And under these conditions, the responses shown in odd-numbered averaged EEG and even numbered averaged EEG were thought to possess the common factors to some extent in terms of morphology and latency. The response could be identified by searching the common factors in these two averaged EEG even in these cases in which the responses in the conventional method were not distinct. The detectability of the responses by this method was 79%, which is fairly good comparing with those in the conventional methods, and the incidence of false positive response was decreased to 13%.
The auditory evoked slow vertex response (SVR) was examined using a wireless telemeter in 34 awake children with normal hearing between the ages of 2 and 6, and in 22 sleeping children using the conventional method (control study). The results were as follows: (1) Using a wireless telemeter, SVR was obtained in all awake subjects. (2) The delectability of the responses in the awake state was better than in the sleeping state. (3) In the awake state, SVR showed shorter latencies in accordance with the increase of sound intensity, while no relation was found in the sleeping state. (4) The patterns of SVR in the awake children were highly variable and were not be tipified to a single form. In the same subjects, however, test-retest modalities showed the quite similar patterns. (5) Using this telemeter in the awake children, the rate of detection of false positivee response was 20.8%. (6) The averaged power spectra of EEG were also examined with or without sound applied to the subjects, and no clear difference of the power spectra in each state was found.