Biomedical subjects

K Gyo

Publications and source records attributed to K Gyo.

At least 19 recordsLinked to original sources

PubMed1995

Herpetic vestibular neuritis: an experimental study.

An animal model of vestibular neuritis was developed by inoculating herpes simplex virus type 1 (HSV-1) into the auricle of mice. Postural deviation was observed in 5 of 99 mice at 6 to 8 days after inoculation. Following evaluation of the vestibular function, the animals were sacrificed and the vestibular nerves examined for histopathology and immunohistochemically. All mice developed postural deviation, presented as abnormal behaviour; they could not perform various vestibular tasks, such as gait, traversing a narrow path, climbing a rope, negative geotaxis, grasping a rod, and swimming. Degeneration of Scarpa's ganglion was observed in 4 of 5 mice that developed postural deviation, while HSV-1 antigens were found in 2 of them. No such histological findings were seen in animals with normal vestibular function.

Animals↗

PubMed1995

[Dilemma in surgical treatment of petrous cholesteatoma].

Surgical treatment of petrous cholesteatoma that involves the petrous pyramid and extends beyond the internal auditory canal is often difficult because of the site and extent of the cholesteatoma. Various problems pertaining to the operation are discussed from our experience with fourteen patients who underwent surgery in our hospital. When accompanied with otorrhea, the middle ear was eradicated by radical mastoidectomy before total removal of the cholesteatoma in order to avoid intracranial infection. Staging operation was conducted in 6 patients in which otorrhea could not be stopped by conservative treatment. The surgical approach was translabyrinthine in 10 patients, middle cranial fossa plus transmastoid in 2, and a combination of these methods in 2. The postoperative large cavity was totally exteriorized in 5 cases in which eradication of the cholesteatoma was deemed too risky, although the exposed internal auditory canal and the denuded dura were supplemented locally. In the other 9 cases, the cavity was obliterated with abdominal fat and/or muscle flap. Facial nerve palsy was present preoperatively in 11 patients. They were treated by decompression in 7 cases, nerve-anastomosis in 2 and nerve grafting in one. In one patient, atrophy of the nerve was too severe to perform nerve grafting. Plastic surgery, such as suspension of the eyelid and masseter muscle transfer, was additionally carried out in 6 of the above patients. Postoperative follow-up study with CT and MRI is very important. In 3 of our cases, the cholesteatoma recurred and the reoperation was needed.

Adult↗

PubMed1995

[Middle fossa acoustic neuroma surgery--indications and predictive factors for hearing restoration].

Between June 1990 and May 1993, 17 acoustic tumors were removed by the middle cranial fossa approach with attempted hearing preservation. Measurable hearing was restored in 13 patients (76.5%) and useful hearing (PTA < 50 dB, SDS > 50%) in 10 patients (58.8%). In addition, significant hearing improvement, greater than 10 dB in pure-tone average, was noted in 6 patients (35.3%). In the hearing improvement group, useful hearing was restored after tumor resection in two patients with poor preoperative hearing. These six patients with hearing improvement exhibited several findings in common: smaller tumors, sudden deterioration of hearing, trough type of audiogram, inferior vestubular nerve origin and short duration of hearing loss before surgery. Such signs suggested favorable preoperative prognostic factors for potential postoperative hearing improvement. Because there was no significant difference between postoperative facial nerve outcome in the middle cranial fossa approach and the translabyrinithine approach in our series of small tumors, we recommend the use of the middle cranial fossa approach for hearing preservation in patients with small tumors, even when their hearing is poor preoperatively.

Adult↗

PubMed1995

Partially implantable hearing aid using piezoelectric ceramic ossicular vibrator. Results of the implant operation and assessment of the hearing afforded by the device.

The aim of designing an implantable hearing aid (IHA) is to compensate for some of the disadvantages of conventional hearing aids. The IHA described in this article is a direct oscillation type in which the piezoelectric ceramic ossicular vibrator coupled directly to the stapes transmits sound signals to the perilymph effectively. This type of IHA can give a better fidelity of sound perception than a conventional hearing aid.

Adult↗

PubMed1994

Solubilization of keratin debris in conservative treatment of middle ear cholesteatoma: an in vitro study.

A variety of solutions were tested in vitro to find a suitable solvent which could be used in clinical practice for cholesteatoma debris. Though a little weak as a solvent, a liquid soap composed mainly of plant oil did not cause irritation of the middle ear mucosa, and was thought to be a promising solvent with which to rinse away tenacious debris, especially when used in combination with hydrogen peroxide.

Cholesteatoma↗

PubMed1994

Experimental cholesteatomas arising from autologous free skin grafting in the middle ear cavity.

An autologous free skin graft taken from the upper or the lower external ear canal or the auricle was implanted in the otic bulla of 28 guinea pigs. An epidermal cyst simulating middle ear cholesteatoma was successfully produced in 25 (89.3%) animals 8 weeks after grafting. Using this model, the histological reaction of middle ear granulation tissue to the debris was studied. Cysts originated from the auricular skin showed the strongest activity with regard to growth rate, amount of debris produced, and inflammatory reaction to the exposed debris. We conclude that the exposed debris plays an important role in chronic granulomatous inflammation in association with cholesteatoma.

Animals↗

PubMed1994

[A case of revision of a cochlear implant].

The patient was a 41-year-old man who lost his hearing on the left at 7 years of age and on the right at 34 years of age due to meningitis. At 35 years of age a single-channel cochlear implant, 3M/House design, was implanted. Five years after the initial operation, the single-channel prosthesis was replaced by a multichannel device (Cochlear Corp.) because of the patients earnest wish to obtain better hearing. Explanation of the short electrode of the single-channel device was easy, but reimplantation of the longer electrode of multichannel device was somewhat difficult, probably because of the presence of the peri-implant fibro-osseous cuff in the Scala tympani. Single-channel and those of the multichannel speech data were compared in relation to performance in the same individual. The reimplanted multichannel device was equivalent to or outperformed the original 3M prosthesis. The patient preferred the hearing afforded by the multichannel device.

Adult↗

PubMed1992

Incidence of attic retraction after staged intact canal wall tympanoplasty for middle ear cholesteatoma.

Incidence of retraction pocket and recurrent cholesteatoma in the attic after surgery for middle ear cholesteatoma using the staged intact canal wall technique were investigated in 95 ears of 91 patients, all of which had various degrees of bone defect in the tympanic scutum. Surgical procedures employed in the second stage for prevention of attic retraction were classified into three types: Type I, no scutumplasty; Type II, scutumplasty; Type III, scutumplasty plus mastoid obliteration. In 83 ears followed up for more than 1 year after the second stage, such retraction troubles occurred in 2 of 13 ears (15%) in Type I, 8 of 20 ears (40%) in Type II, and 24 of 50 ears (48%) in Type III. Incidence of retraction troubles was higher in Types II and III, probably because these procedures were indicated in ears with large scutum defects. Dislocation and atrophy of the graft materials, together with bone resorption around the bone defect were the main reasons for failure in scutumplasty. Dysfunction of the eustachian tube and traction of the eardrum by the scar tissue behind it may have also contributed to attic retraction. Mastoid obliteration with small blocks of hydroxyapatite was more effective in prevention of retraction troubles than that with pedicled temporalis muscle flap.

Adolescent↗

PubMed1992

Transmission of change in the atmospheric pressure of the external ear to the perilymph.

In experiments using guinea pigs, the middle ear and perilymphatic pressures were simultaneously registered in response to pressure change in the external ear canal. In the first experiment, pressure was slowly loaded in the ear canal in the range of 200 mm H2O to -200 mm H2O. Pressure transmission to the perilymph was smaller when the bulla was open to the outside than when it was closed. It was significantly impaired by disruption of the ossicular chain and especially by closure of the round window. The data indicate that air volume in the middle ear cavity plays an important role in transmission of slowly changing atmospheric pressures. In the second experiment, the eustachian tube was closed and the pressure was changed in the range of 1000 mm H2O to -1000 mm H2O. The middle ear and perilymphatic pressures increased or decreased corresponding to the loading pressure in the range of 400 mm H2O and -200 mm H2O. Beyond these levels, response rate of the middle ear pressure decreased and perilymphatic pressure declined in spite of further increase in loading pressure. The increase in pressure difference between the middle ear and the inner ear might cause disruption of the round and/or oval windows.

Animals↗

PubMed1991

[Experiment study on solubilization of cholesteatoma debris].

A variety of solutions were tested in vitro to find a suitable solvent of cholesteatoma debris for use in clinical practice. The specimens were taken during surgery from the patients of otitis media with cholesteatoma. They were divided in pieces and put in test tubes. Each tube was then admixed with one of the test solutions and incubated at 37 degrees C for 48 hours. Hydrochloric acid (1N) and sodium hydroxide (1N) had no substantial effect to solve the debris. Urea (10N), acetylcysteine (20%) and chymotrypsin (1%) had a weak such effect. Proteolytic agents such as diiodosalitylic acid (0.1N), sodium dodecyl sulfate (0.1N) and cholic acid (0.1N) showed a stronger effect but not enough for clinical use. In contrast, a detergent which contains interfacial active agents and a proteolytic enzyme (alkaline cellulase), such as Attack and Hi-Top, proved to be more effective to solve the debris. However, biological effect of such detergent on the ear is not clear. Further study will be necessary before actual application in the patients.

Cholesteatoma↗

PubMed1991

Defects in the bony wall of the mastoid bowl: a study based on staged intact canal-wall tympanoplasty.

The incidence and outcome of bony wall defects in the mastoid bowl were studied in 175 ears of 167 patients who underwent staged tympanoplasty by the intact canal-wall technique. In the first stage, the middle fossa dura was exposed iatrogenically in 38 ears and pathologically in eight ears through a defect at the tegmen. In the second stage, the bone defect was cured in 27 ears of the former group and in 3 ears of the latter group. The overall cure rate of the defect in the tegmen during these stages was 65.2 percent (30/46). Exposure of the sigmoid sinus or posterior fossa dura, which had occurred iatrogenically in 12 ears in the first stage, was cured in 11 ears (91.7%) in the second stage. Defects of the anterior wall of the mastoid bowl, i.e., the posterior wall of the external auditory canal, were recognized in 105 ears in the first stage, 91 of which involved pathologic defects of the tympanic scutum caused by cholesteatoma. In the second stage, these defects remained unhealed with cures occurring in only two ears (1.9%), in which a small hole had been created iatrogenically in the middle of the canal wall. Defects in the canal wall due to bone resorption following the first stage operation were noted in the second stage in 26 of 175 ears (14.9%).

Adolescent↗

PubMed1991

Inflammatory pseudotumor of the facial nerve as a cause of recurrent facial palsy: case report.

This is a report of a case presenting recurrent facial palsy due to inflammatory pseudotumor of the facial nerve. The patient was a 41-year-old man suffering from facial palsy on the right side once in 1983, which recurred in 1988. The initial facial palsy was cured after conservative treatments including steroid administration. Three months after the recurrence, the same treatments were attempted without noticeable effect. He was referred to our clinic two and half months later. Electromyographic examination indicated pronounced denervation of the facial nerve. Imaging study including high resolution CT and MRI revealed a mass lesion around the geniculate ganglion. Facial neuroma was initially suspected. Surgical exploration revealed a tumor involving the geniculate ganglion and the horizontal portion of the facial nerve. The tumor was resected through a combined transmastoid and middle cranial fossa approach, followed by nerve grafting. Histologically, the tumor proved to be an inflammatory pseudotumor originating from the nerve sheath, although the etiologic factor causing the inflammation was not verified.

Adult↗

PubMed1990

Chronic otitis media and tympanoplasty in aged patients.

Results of tympanoplasty in patients over 60 years old were analyzed mainly in terms of hearing and postoperative course. Tympanoplasty was carried out in 78 ears of 67 patients during the last ten years. The following types of tympanoplasty were employed: type I in 34 ears, type III-Columella in 23 ears, type IV-Columella in 13 ears, and other types in 8 ears. The results were compared to those of 145 ears from 119 patients ranging from 20 to 59 years of age who had undergone tympanoplasty during the last 3 years. In tympanoplasty type I, closure of the air-bone gap within 20 dB was attained in 70% of the patients over 60 years old, 90% in the 50-59 year age group, and 100% in the 20-49 year age group. In type III-Columella, these values were 60, 78, and 94%, respectively. During the postoperative follow-up, perforation of the eardrum recurred in 5 of 78 ears (6.4%) in the patients over 60, in 5 of 52 ears (9.6%) in the 50-59 year group, and in 7 of 93 ears (7.5%) in the 20-49 year group. These results suggested that hearing results were worse in patients over 60 than in the other age groups, even though the incidence of graft failure did not greatly differ by age.

Adult↗

PubMed1990

[Recurrence of perilymphatic fistula].

Recurrence of the perilymphatic fistula is not rare and may be a tough problem for surgical treatment. This is because a graft is usually applied on the ruptured window(s) from the middle ear and therefore the perilymphatic pressure directly acts on the graft. The recurrence may be caused by a technical failure, use of an unsuitable graft material, poor postoperative bedrest, trauma, increased inner ear pressure, etc. In our clinic, the recurrence occurred in 7 of 48 cases surgically treated. Vertigo accompanied with spontaneous or positional nystagmus was seen in all 7 recurrent cases, while only 2 of them complained of worsening of the existing hearing loss. Re-operation was carried out in two patients. In the first case, closure of the round window by the previous operation was found incomplete, and the perilymph leaked through the gap around the graft. In the second case, closure of the round window was complete, but perilymph leaked from the oval window. In order to prevent the recurrence, the operation should be carefully performed by using strong and adhesive tissue as a graft material, applying a glue between the graft and the inner ear window(s), and keeping strict postoperative bedrest.

Adolescent↗

PubMed1990

[Audiological evaluation of the middle ear implant--temporal auditory acuity].

Temporal auditory acuities provided by the middle ear implant (MEI) and by the hearing aid (HA) were compared in ten patients implanted with the MEI. Test sounds used in the experiment were tone bursts [rise and fall time: 25 msec, duration (t): 982-1000 msec, interval (T): 1000 msec] of 500 Hz or 2000 Hz at 70 dBSPL. A speaker was placed in front of a subject one meter apart. At first, the subject adjusted the gain control of outer unit at the most comfortable loudness level. He heard totally fifty times of the test sounds, which varied in duration each 2 msec difference between 982 and 1000 msec and were provided in random manner. Therefore, sound of each duration was given 5 times. The notch [= (T-t) x 2] of the test sounds recognized by the patients was regarded as time gap. Fifty percent discrimination thresholds, which were indicated by the gap times of the test sounds half identified, were obtained as the index of the temporal auditory acuity. Following the above test, performance of the HA was investigated by use of the same procedure. The results indicated that the temporal auditory acuities of the MEI were superior to those of the HA at 500 Hz (P less than 0.01) and 2000 Hz (P less than 0.001). When the intensity of the test sound at 2000 Hz decreased from 70 dBSPL to 60 or 50 dBSPL, the temporal auditory acuities of the MEI and the HA were almost depreciated together with consistent difference in the test of 6 patients (P less than 0.01, 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

[Audiological evaluation of the middle ear implant--speech discrimination under noise circumstances].

Speech discrimination scores under noise circumstances were studied by use of the middle ear implant (MEI) and the conventional hearing aid (HA, HA-33, RION, Co, Ltd). The studies were performed in 10 patients implanted with the MEI and in 12 adult volunteers with normal hearing as a control. The tests were carried out using Japanese monosyllabic lists from 57S-speech discrimination test list as a test sound and multi-talker noise as a noise source. A speaker was placed in front of a subject in one meter apart. Sound characteristics of HA were adjusted as far as possible to those of the MEI by use of a sound equalizer. The intensity of speech sound pressure was adjusted at 65dB SPL, while that of the noise was changed to 65, 70 and 75dB SPL in the position of patients. Audiological evaluation of the MEI, the HA and control obtained by percentages of correct answers to 50 words in speech discrimination test with and without noise (65, 70, 75dB SPL). When the test was performed without noise, speech discrimination scores by the MEI and the HA were either 96.8 +/- 3.6% and 94.8 +/- 4.1%. However, under noise circumstances (65dB SPL) that by both devices were either 81.6 +/- 9.1% and 66.8 +/- 10.6% (P less than 0.001). When the intensity of the noise increased to 70 and 75dB SPL, speech discrimination scores by both devices deprecated together with consistent difference (P less than 0.01). Moreover speech discrimination scores by the MEI were almost same as control.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

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↗