PubMed Health⌕ Search

Biomedical subjects

K Gyo

Publications and source records attributed to K Gyo.

At least 73 records · Page 4Linked to original sources
PubMed1988

Benign paroxysmal positional vertigo as a complication of postoperative bedrest.

Seven cases of benign paroxysmal positional vertigo (BPPV) after operation were reported, occurring between the fourth and 14th postoperative day. In three of the seven cases, the condition occurred when the patients first arose from bed after 5 to 6 days of postoperative bedrest. In two cases, BPPV occurred when patients moved their head while maintaining strict bedrest. In the other two cases, it occurred 1 to 4 days after patients had been released from bedrest. The cause of BPPV was considered to be postoperative bedrest which might have facilitated the deposition of precipitate on the cupula of the posterior semicircular canal. The prognosis was good, and all the patients recovered within 20 days.

Bed Rest↗
PubMed1988

Experimental study on autograft material for repair of round window rupture.

The healing process following experimentally produced rupture of the round window (RW) and subsequent closure with autograft materials were investigated in guinea pigs. The covering materials studied were fascia and perichondrium, both of which were placed over the RW after extensive rupturing of the RW membrane. The grafts were observed 1, 2, and 3 months after the operation. No substantial difference in the results for the two materials could be discerned. They adhered to the surrounding bone and were incorporated into the RW membrane within 3 months.

Animals↗
PubMed1988

Pressure transmission properties from the externa ear canal to the inner ear. An experimental study using guinea pigs.

The inner ear pressure (PIE) in response to pressure changes in the external ear canal was measured in guinea pigs while alternatively opening and closing the perforation of the otic bulla. When the bulla was opened, only a transient degree of applied pressure was transmitted to the inner ear and the amplitude of the PIE was smaller than that of the corresponding PIE when the bulla was closed. This was because the applied pressure was exclusively transmitted to the inner ear via the ossicular chain. When the otic bulla was closed, the pressure was transmitted not only via the ossicular chain but also via the round window (RW) through the middle ear cavity. When the bulla was closed, the amplitude of PIE was larger by a positive pressure load than by the corresponding negative one. The amplitude of PIE showed a linear relationship to ear canal pressure of at least within the +/- 200 mmH2O range, as long as pressure was slowly applied to the ear canal. When the loading pressure was abruptly changed, a bouncing response, possibly reflecting elasticity of the RW, was evoked, which diminished or disappeared when the round window was artificially ruptured.

Acoustic Impedance Tests↗
PubMed1988

Implantable hearing aid in fourteen patients with mixed deafness.

An implantable hearing aid (IHA) in which the stapes was directly driven by a ceramic vibrator of bimorph design was applied to fourteen patients with mixed deafness of varying degree due to chronic otitis media. In the partial IHA system, only the output transducer and secondary coil are implanted, the remainder of the components such as microphone, amplifier, battery and primary induction coil remain in the location behind the auricle. The vibrator was activated by an electric signal transmitted electromagnetically through the induction system from the outer unit. All the patients admitted that sound quality provided by the IHA was natural, clear and easy to hear without causing fatigue in long-term use. Speech discrimination test under noise circumstance showed that acoustic perception by the IHA was superior to that by a conventional hearing aid. In four patients, however, the implanted unit was replaced with a new one due to recurrence of cholesteatoma, head trauma, and accidental disruption of wire by manipulating the ear canal. They regained good hearing after re-implantation.

Adult↗
PubMed1987

Implantable hearing aid. Report of the first human applications.

To our knowledge, this is the first report of human application of the partial implantable hearing aid. Direct driving of the stapes by an ossicular vibrator of piezoelectric ceramic bimorph is the fundamental mechanism of this device. Acoustic signals received by a microphone were transmitted to the external link coil after amplification. By means of electromagnetic induction, the internal coil placed under the retroauricular skin excited electroacoustic energy, which is transmitted to the vibrator directly coupled with the stapes. The device used in this first patient has been functioning for longer than one year. Excellent frequency response of the vibrator and highly efficient direct transmission of electroacoustic signals to the inner ear gave rise to acoustic perception of superior quality that could not be obtained by other surgical or rehabilitative measures.

Deafness↗
PubMed1987

Stapes vibration produced by the output transducer of an implantable hearing aid. Experimental study.

The function of the output transducer of an implantable hearing aid was assessed by applying it to the stapes head in seven fresh human cadaver temporal bones while observing vibration of the stapes under a microscope with the use of a stroboscope and a video measuring system. The transducer was a 5 X 1.2 X 0.6-mm piezoelectric ceramic bimorph with attached metal holder. Transmission changed with the amount of force holding the transducer tip on the head of the stapes. An optimal connection between the vibrator and stapes produced better transmission than a tight or loose connection. Gluing the connection with cyanoacrylate cement decreased transmission in the optimal connection, produced no change in the tight connection, and improved transmission in the loose connection. Comparison of stapes displacement produced by the vibrator at 1 kHz with that produced by normal middle-ear sound transmission revealed that the vibrator-induced stapes displacement for a 1 V peak-to-peak input was equivalent to that produced by a sound stimulus of 90-dB sound pressure level at the tympanic membrane.

Ear Ossicles↗
PubMed1987

Effects of middle ear pressure changes on umbo vibration.

Effects of middle ear pressure changes on umbo vibration were studied in 5 fresh human temporal bones taken from cadavers. Umbo vibration to a constant sound pressure of 120 dB SPL at the tympanic membrane was measured with an MTI 1000 Fotonic Sensor. The results showed that there was a loss of umbo vibration at lower frequencies below 2 kHz; 5.0 +/- 1.0 dB loss at -100 mmH2O, 9.2 +/- 1.3 dB loss at -200 mmH2O, and 13.1 +/- 1.8 dB loss at -300 mmH2O. In contrast, there was a slight increase in umbo vibration at around 2-3 kHz. The effect was considered to be mainly due to increased stiffness of the tympanic membrane and decreased air volume in the middle ear cavity.

Cadaver↗
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↗