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Biomedical subjects

K Gyo

Publications and source records attributed to K Gyo.

At least 91 records · Page 5Linked to original sources
PubMed1987

Implantable hearing aid using an ossicular vibrator composed of a piezoelectric ceramic bimorph: application to four patients.

Direct driving of the stapes by an ossicular vibrator composed of a piezoelectric ceramic bimorph is the key functional mechanism of the partially implantable hearing aid reported in this article. Acoustic signals from a microphone are transmitted to the vibrator by means of electromagnetic induction. The devices were implanted into four patients with mixed deafness due to chronic otitis media. In the first patient, the device has continued to function for two years. The highly efficient sound transmission achieved by the direct driving of the stapes produced excellent sound perception. The functional principle, surgical procedure, and indications for this new device for hearing rehabilitation are described together with the clinical results obtained in the four patients.

Audiometry↗
PubMed1986

Effect of middle ear modification on umbo vibration. Human temporal bone experiments with a new vibration measuring system.

The effects of aditus blockage, decrease of tympanic cavity volume, and resection of the tensor tympani muscle on umbo displacement were studied in human temporal bones using a new non-contacting video measuring system. This system, combined with stroboscopic illumination, allowed measurement of umbo vibration down to 0.3 micron in the 0.1- to 4.5-kHz frequency range for a constant 124-dB sound pressure level at the tympanic membrane. Aditus blockage caused a mean increase of 5.4 dB with a peak at 2.8 kHz and a mean decrease of 3.4 dB below 1.6 kHz. Decrease of the tympanic cavity volume by 30% to 42% showed an improvement of 2.2 dB in the 1.4- to 3-kHz range and a similar loss below 1 kHz. Resection of the tensor tympani muscle produced a slight improvement of 1.7 dB at 1.8 kHz.

Bone Conduction↗
PubMed1984

Development of an implantable hearing aid using a piezoelectric vibrator of bimorph design: state of the art.

A new, implantable hearing aid has been developed. An ultraminiature electric microphone placed under the skin of the external ear canal transduces sound waves into electrical impulses that are amplified with battery power. The amplified electrical impulses are fed into a piezoelectric vibrator directly in contact with the stapes. The vibrator transduces the electrical impulses into mechanical vibration with minimal consumption of electrical energy. Direct coupling of the vibrator to the stapes allows a high degree of fidelity in the perception of sound. The developmental process and the structure and function of each component are described together with clinical problems. Preliminary and tentative implantation of this new device during middle ear surgery indicated that it would be beneficial to patients who have suffered hearing loss from middle ear disease and whose condition does not lend itself to surgical correction.

Electric Power Supplies↗
PubMed1984

Sound pickup utilizing an implantable piezoelectric ceramic bimorph element: application to the cochlear implant.

The degree of sound pickup possible with a piezoelectric ceramic bimorph element ( PCBE ) was tested as part of research on a total implantation system for a cochlear prosthesis. The PCBE functions as an electromechanical transducer and can be utilized as a device to sense vibration in the tympanic membrane by touching it to the malleus head. This method lends itself to the miniaturization and simplification required by an implantable device for sound pickup. The ability of the PCBE to function as a device to pick up sound was investigated using three normal human temporal bones. The sensitivity of the PCBE when coupled to the malleus was calculated as the ratio of the voltage generated by the PCBE to the sound pressure in front of the tympanic membrane, when these factors were processed with a spectrum analyzer. The best sensitivities registered with the three temporal bone specimens were -63, -61, -59 dB re 1 V/Pa, respectively, at 1 kHz. The frequency response curves had resonant frequencies at about 2 kHz and declined beyond 5 kHz. These results indicate that a PCBE coupled to the malleus head performs satisfactorily in regard to sound pickup and shows promise as a component of a totally implanted hearing system.

Bone Conduction↗
PubMed1982

Endolymphatic-mastoid shunt operation: results of the 24 cases and revision surgery with the silastic sheet.

Endolymphatic-mastoid shunt operation due to Kitahara's method was performed on 24 patients with Meniere's disease. In 14 patients, the vertiginous attack was controlled with satisfactory preservation of hearing for longer than one year. In 2 patients, the vertiginous attack subsided but the hearing worsened. In the remaining 8 patients, long-term control of the vertiginous attack was not attained. Of these 8 recurrent cases, revision was performed on 4, revealing shunt obstruction with granulation or scar tissue. After reopening the endolymphatic sac, a large triangular Silastic sheet was placed into its lumen. The vertiginous attack was controlled thus far in the revised cases using this procedure.

Adult↗
PubMed1981

Averaged blink reflex test.

Averaging of blink reflex responses was of particular value in detecting a very small potential of R1 in patients with severe facial nerve palsy where the conventional single stimulation method proved inefficient. To find the most suitable interval of stimulation for averaging, the recovery cycle of R1 was studied. The result showed that the R1 recovery curve could be divided into four phases. The initial facilitation phase at the interval of 5 msec was followed by a brief phase of depression. It was further followed by a second facilitation phase with a maximum of about 60 msec. Lastly the recovery curve returned to almost the 100% level after 100 msec. Due to the second facilitation phase, stimuli given at the interval of 60 msec were efficient for averaging of blink reflex responses. Though R1 to the second stimulus at this interval might have overlapped with R2 to the first stimulus, averaging of responses made R1 more prominent and R2 more inconspicuous, because R1 had a constant latency and R2 a variable one to each stimulus.

Adult↗
PubMed1980

Electrically and acoustically evoked brain stem responses in guinea pig.

Brain stem evoked responses (BSERs) to acoustic and electrical stimulations of the cochlea were compared in guinea pigs. The electric stimuli evoked an averaged response of five to six successive waves within 10 msec, which was similar to that elicited by acoustic stimuli, though the latency of the electrical response was markedly shorter. Moreover, direct electrical stimulation of the auditory nerve evoked the same pattern of response as that elicited by electrical stimulation of the cochlea. On the other hand, stimulation of the vestibular nerve evoked a distinctly different pattern of response that lasted at most for 1.5 msec. Facial nerve stimulation evoked no brain stem response by this procedure. These results suggest that the waves of longer latency over 1.5 msec are available as indicators of auditory activity, even if the response elicited by electrical stimulation of the cochlea might be the sum of auditory and vestibular activities.

Acoustic Stimulation↗
PubMed1979

Transmastoid decompression of the facial nerve in Bell's palsy.

We describe the technique of decompression of the facial nerve from the geniculate ganglion to the stylomastoid foramen. The decompression was made on 51 patients with Bell's palsy, and the results of follow-up study were compared with those of 77 patients in whom the pyramidal and vertical segments were decompressed. The decompressions were indicated when a severe denervation of the nerve was confirmed by electrodiagnostic examinations. Incidences of notable residual palsy and of pronounced sequelae were always lower in the former group of patients regardless of the operational timing. In either group, a more desirable result was obtained by the decompression within 30 days, but a favorable effect of the decompression was recognizable even when the surgery was performed between 31 and 90 days after the onset.

Adolescent↗
PubMedDate not supplied

Perception of sound through direct oscillation of the stapes using a piezoelectric ceramic bimorph.

An ossicular vibrator of original design made from a piezoelectric ceramic bimorph was described. To test its effectiveness, the vibrator was temporarily implanted during tympanoplasty in four selected patients who had suffered extensive damage to the middle ear. By use of a special applicator, the vibrator was connected to either the stapes or the columella and was then excited by pure tone and speech signals. The subjects could hear well with the vibrator and distinguish speech signals. Thus a vibration threshold curve and a vibratory speech discrimination score were obtained. Comparing these with the results of conventional audiometry, the vibrator proved to be a highly efficient sound-conducting device. This study furthermore calls attention to some practical applications of this device, particularly to the possibility of implanting the vibrator as part of an implantable hearing aid.

Adult↗
PubMedDate not supplied

Clinical assessment of ossicular mobility by a ceramic vibrator designed for implantable hearing aids.

Ossicular mobility was assessed by direct coupling of a piezoelectric ceramic vibrator to the ossicles during middle ear surgery. The sites excited were body of the incus, head of the stapes, and footplate of the stapes through a hydroxyapatite ceramic strut. The threshold of the vibratory hearing was determined by the patient's response as a minimum audition, and the vibration threshold was obtained by subtracting the preoperative bone conduction threshold from the vibratory hearing threshold. The results were analyzed by the state of hearing after the operation, which revealed that a patient with a good vibration threshold during the operation had a tendency to get good postoperative hearing. This may mean that postoperative hearing can be predicted to some extent during the operation by the measurement of ossicular mobility.

Adolescent↗
PubMedDate not supplied

Topodiagnosis of lesions in Bell's palsy.

Combined measurements of reflexive lacrimation, stapedial reflex, and electrically induced taste give an indication of the site and extent of intratemporal lesions of the facial nerve. Using refined test batteries, we established the presence of intratemporal lesions in Bell's palsy in 80 patients with facial paralysis. In the acute stage of Bell's palsy, suprastapedial lesions predominated and the occurrence of a suprageniculate lesion was not rare. In the subacute stage, the lesions proximal to the stapedial nerve tended to subside and infrastapedial lesions increased. In 60% of 53 patients with denervation verified by electrodiagnostic examinations, the suprastapedial lesion was responsible for degeneration of the nerve. In the other 40%, degeneration involved the infrastapedial segment.

Electromyography↗
PubMedDate not supplied

Measurement of the ossicular vibration ratio in human temporal bones by use of a video measuring system.

Vibration modes of the ossicles and the lever function were studied in human cadaver temporal bones with an intact cochlea. After placing tiny steel spheres on the ossicles, ossicular vibration to a sound stimulus was measured by observing the displacements of the spheres under a microscope with strobe illumination by means of a video measuring system. The lever ratio varied from 1.9 at 0.6 kHz (minimum) to a peak of 6 near 2 kHz. This relatively high lever ratio at higher frequencies was considered to be caused by a shift of the malleus-incus rotation axis secondary to the loading of the cochlear fluid on the ossicular system. Dependence of the lever ratio on frequency indicated that the rotation axis of the ossicles was not fixed, but variable according to frequency due to a relative increase in the translational movements of the rotation axis of the malleus and incus with frequency.

Aged↗
PubMedDate not supplied

Histological study of chronic electrode implantation through the round window of the guinea pig.

A platinum-iridium electrode with a Teflon cover tube was chronically implanted through the round window into the scala tympani of the guinea pig. Animals were sacrificed at 30 to 40 weeks after electrode implantation, and the cochleae were observed by scanning electron microscopy or with light microscopy. The results revealed that the electrode was firmly enclosed with fibrous tissue on the inside of the round window and with epithelial tissue on the outside. These tissues were considered to act as a barrier to the entry of infection while preventing leakage of the perilymph.

Animals↗