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Biomedical subjects

K Gyo

Publications and source records attributed to K Gyo.

At least 55 records · Page 3Linked to original sources
PubMed1990

Present status and outlook of the implantable hearing aid.

An implantable hearing aid (IHA), in which the direct driving of the stapes by a ceramic vibrator is a fundamental mechanism, was applied to 24 patients with mixed hearing loss of varying degree due to chronic otitis media. The instrument used in the present study was a partial IHA, in which only the vibrator and secondary coil were implanted and the remaining components were packed in a unit to be located behind the auricle. All the patients reported that quality of sound provided by the IHA was natural, clear, and intelligible without causing fatigue with long use. Speech discrimination tests conducted under conditions with background noise demonstrated that speech perception with the partial IHA was superior to that with a conventional hearing aid. These advantages may be ascribed to the direct oscillation of the stapes by the piezoelectric element.

Adult↗
PubMed1989

Comments on "Acoustic Transfer Characteristics in Human Middle Ears Studied by a SQUID Magnetometer Method" [J. Acoust. Soc. Am. 82, 1646-1654 (1987)].

The study by Brenkman et al. [J. Acoust. Soc. Am. 82, 1646-1654 (1987)] of malleus umbo and anterior crus of stapes displacement in 14 human temporal bones shows a mean -7.3-dB/oct slope above 1.0 kHz for stapes displacement in response to a 80-dB SPL input at the eardrum. The slope they obtained for midfrequency (1.0-4.0 kHz) stapes displacement is significantly flatter than what was found previously [Gyo et al., Acta Otolaryngol. 103, 87-95 (1987); Gundersen, Prostheses in the Ossicular Chain (University Park, Baltimore, MD, 1971); Kringlebotn and Gundersen, J. Acoust. Soc. Am. 77, 159-164 (1985); Vlaming and Feenstra, Clin. Otolaryngol. 11, 353-363 (1986a)]; in these studies, stapes displacement rolled off at -12.0 to -14.9 dB/oct above 1.0 kHz. It appears that their mean midfrequency stapes displacement slope has been flattened by some unusual results in a small number of ears. Possible reasons for these results are discussed.

Acoustic Stimulation↗
PubMed1989

Intentionally induced abnormalities in optokinetic pattern tests.

Abnormalities of optokinetic nystagmus are easily detected by administering an optokinetic pattern test, in which optokinetic nystagmus responses to acceleration and deceleration of a series of optokinetic stimuli are recorded at slow paper speed, and the results are visually assessed based on the response pattern. Although optokinetic pattern tests are regarded as valuable in diagnosing lesions of the nervous system that directly or indirectly relate to the reflex route of optokinetic nystagmus, these tests can be significantly influenced by the intention of the person being tested. The present study revealed that the majority of abnormal optokinetic patterns can be induced intentionally. This indicates that optokinetic pattern tests are of limited diagnostic value, and a definite diagnosis should not be made based solely on the optokinetic pattern test result.

Brain Diseases↗
PubMed1989

[Single channel cochlear implant: application to three patients].

Single channel cochlear implant of 3M/House design was implanted to the three patients with profound hearing loss. Before the implantation, use of hearing aid had not afforded serviceable hearing enough for speech recognition in these patients. Postoperative courses were uneventful. Speech rehabilitation was started at 3 weeks after the surgery. The speech tracking scores with the cochlear implant plus lipreading achieved 20-25 bunsetues (the minimum meaningful unit of the Japanese sentence) per minute at three or four months after the operation. All the patients could recognize speech of daily life with help of lipreading. However, speech recognition by the cochlear implant alone was not satisfactory.

Adult↗
PubMed1989

[Modification of speech encoding process of single channel cochlear implant utilizing digital delay circuit].

Speech perception by single channel cochlear implant can be improved to some extent by modifying the encoding process of the speech signals. The principle of our encoding strategy is to present speech signals with appropriate delay time for lower frequency components of the speech sound, while without delay for higher frequency components. This is based on a cochlear physiology that higher frequency sounds are perceived earlier than lower frequency sounds, since the former is perceived at the basal turn and the latter at the apical turn. The following tests were performed without the aid of lip reading in the two patients implanted with a single channel cochlear implant of 3M-House design. Lower frequency components of the speech signals were digitally delayed with a Sony SDP-777 ES surround processor. The results indicated that the optimal delay time for identification of /i/, /e/ and /u/ needed longer delay time, while that of /a/ and /o/ need shorter delay time, corresponding to the difference between the first and second formant of each vowel. Comparison of vowel perception with and without delay coding showed that vowel identification with delay coding was superior to that without it; 30% vs. 16% in case 1, and 48% vs. 30% in case 2.

Adult↗
PubMed1989

[The effect of intravenous administration of xylocaine for the treatment of tinnitus].

One hundreds and forty-nine patients (221 ears) suffering from tinnitus were treated by an intravenous administration of Xylocaine. Xylocaine, 1mg per kg, was administered once a week. The immediate effect of Xylocaine on tinnitus was evaluated subjectively for all the patients. The long term effect in 57 patients who received Xylocaine administration more than 12 times was also analyzed. The results can be summarized as follows. 1. Short and long term relief of tinnitus was obtained in 165 of 221 ears (74.7%) and in 35 of 57 cases (61.4%), respectively. 2. This therapy was more effective in old patients and in the patients with low pitch tinnitus, or with positive residual inhibition. 3. The numbers of the effective cases increased after the 8th time administration of Xylocaine. Thus we recommend the Xylocaine administration at least 8 times. 4. The results of the loudness balance test were not correlated with the change of the subjective improvements. 5. The suppressive effect of tinnitus by injecting saline solution intravenously was recognized in 24 of 73 cases. At present, repeated administration of Xylocaine would be one of the most significant therapies of tinnitus.

Adolescent↗
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↗