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N Yanagita

Publications and source records attributed to N Yanagita.

At least 19 recordsLinked to original sources
PubMed1998

An electrophysiologic study of the guinea pig inner ear following low pressure barotrauma.

We examined electrophysiologic and morphologic changes following low pressure barotrauma in 25 guinea pigs. Compound action potentials (CAPs), cochlear microphonics (CMs), and transiently evoked otoacoustic emissions (TEOAEs) were elicited by tone bursts (1, 2, 4 and 8 kHz) or non-linear clicks immediately following barotrauma. CAP threshold elevations were observed in 19 out of 25 cochleas, mainly at lower stimulus frequencies. Furthermore, CM and TEOAE thresholds were significantly increased, while CAP and CM amplitudes demonstrated reductions at all stimulus frequencies and intensities. CAP N1 latencies exhibited slight elongations at all stimulus frequencies and intensities. The regression coefficient between the mean CAP thresholds of four stimulus frequencies and TEOAE thresholds was statistically significant. Scanning electron microscopy (SEM) study of six electrophysiologically abnormal cochleas revealed stereocilia morphology in four, but no changes in two. We hypothesize that low pressure barotrauma can injure inner ear hair cells through an early threshold shift secondary to dislocation of the basement membrane.

Acoustic Stimulation↗
PubMed1998

[The influence of age and sex on the results of otosclerosis surgery].

The influence of age and sex on auditory improvement after stapes surgery was investigated retrospectively on 127 otosclerotic ears (99 subjects) that were followed up for 6 months postoperatively. The prostheses used were the Shuknecht-type Teflon wire piston (87 ears), the House-type wire loop (29 ears), and the Cawthone-type Teflon piston (11 ears). While closure of the air-bone gap after surgery was good at 2 kHz, it was poor at 8 kHz and frequencies lower than 1 kHz, and especially poor at 250 Hz. At all frequencies, both air and bone thresholds were significantly improved by the surgery, but the greatest improvements in air and bone thresholds resulted from the use of Teflon wire pistons. Ears receiving Teflon wire prostheses were divided into 5 age groups: under 20 years, 20-29, 30-39, 40-49, and 50 or above. Both air and bone thresholds at higher frequencies before surgery worsened with increasing age. However, there were no significant differences among age groups in the postsurgical improvement of either air or bone thresholds. Similarly, no gender-related differences in either air or bone thresholds were recognized postsurgically. The authors speculate that light cases of otosclerosis are common among Japanese patients, while severe cases are rare even among the elderly.

Adult↗
PubMed1997

Changes in cochlear function after double-membrane rupture in the guinea pig.

We measured the transiently evoked otoacoustic emissions (TEOAEs), compound action potentials (CAPs) and cochlear microphonics (CMs) in guinea pigs after rupture of the round window membrane alone (n = 5) or of the round window membrane with localized cochlear damage (n = 10). The localized cochlear damage entailed rupture of Reissner's membrane with damage to the stria vascularis. We determined the time course of changes in the total echo power (TEP) in TEOAEs and the minimal detectable levels of CAPs and CMs. The endocochlear potential (EP) was measured in the cochlea with localized damage. There were no changes in TEOAEs, CAPs or CMs in the guinea pigs subjected to round window membrane rupture alone, but the minimal detectable levels of CAPs and CMs were increased in all the guinea pigs in which TEOAEs were absent after rupture of the round window membrane with localized cochlear damage. Our results suggest that double-membrane rupture (rupture of the round window membrane with localized cochlear damage) produces acute sensorineural hearing loss. The hearing loss appeared to be related to damage to the cochlea, which may be induced by influx of potassium-rich endolymph into the perilymph, and by morphological damage to the scala media.

Acoustic Stimulation↗
PubMed1997

Risk factors for sudden deafness: a case-control study.

In order to investigate risk factors for idiopathic sudden sensorineural hearing loss (sudden deafness), a case-control study was done in 109 patients with sudden deafness who visited our hospital between 1992 and 1994, with 109 controls matched to each patient by gender and age. Odds ratio (OR) and 95% confidence interval (CI) for smoking habits, drinking habits, dietary habits, environmental noise, past history of disease, sleeping hours, appetite, fatigue, incidence of common cold were obtained. Fatigue (OR: 3.28; 95% CI: 1.36-7.90) and loss of appetite (OR: 8:00; 95% CI: 1.00-64.0) elevated the risk for sudden deafness. Those who ate many fresh vegetables were at a decreased risk (OR: 0.48; 95% CI: 0.24-0.96 for light-colored vegetables, OR: 0.55; 95% CI: 0.30-1.02 for green-yellow vegetables). Personal histories of hypertension and thyroid disease, and susceptibility to colds appeared to be positively associated with the risk (0.05 < P < 0.10). Smoking habits, drinking habits and environmental noise had no significant association with sudden deafness. These results suggested that environmental factors, including diet, may be importantly involved in the genesis of sudden deafness.

Adolescent↗
PubMed1997

Comparison of TEOAE with Play audiometry for screening hearing problems in children.

To evaluate the usefulness of transiently evoked otoacoustic emissions (TEOAEs) for hearing screening of children at around 3 years of age, measurements were done together with Peep show test in a group of 47 children (n = 93 ears). A stimulus sound of 30 dB nHL was used as the screening intensity for the TEOAE measurement. All measurements were done with awake subjects. Twenty seven ears, all of which were revealed to have normal hearing (within 20 dB HL, assessed by Peep show test) and tympanograms, showed positive TEOAE results. Furthermore, TEOAEs were sensitive to the presence of middle ear conductive impairment, showing negative results. We conclude that, compared with Play audiometry, TEOAE measurements can not yield quantitative results, but can yield qualitative results for determining the presence of hearing impairment without sedative induced sleeping in this critical age of children.

Acoustic Impedance Tests↗
PubMed1997

A case of pleomorphic adenoma of the epiglottis. Bilateral vocal-cord paralysis after YAG laser surgery.

Pleomorphic adenoma of the larynx is a rare disorder, and until recently has been treated mainly by approaches involving pharyngotomy. We encountered a case of pleomorphic adenoma originating from the laryngeal surface of the epiglottis and removed it using a YAG laser through a suspension laryngoscope. This case was complicated by delayed-onset bilateral vocal-cord paralysis, the causes of which are also discussed.

Adenoma, Pleomorphic↗
PubMed1997

Radiation tolerance of the cochlear nerve at the gamma-knife in rabbits.

Since the first treatment of acoustic neurinoma using the gamma-knife by Leksell, a series of cases have been reported with good control rates. However, the most frequent complication is delayed hearing loss which occurs in more than 50% of patients. The purpose of this study was to define a safe dose by analyzing the radiosurgical dose-response relationship and histological effects on the normal cochlear nerve in rabbit. The rabbits had computed tomography (CT)-guided stereotactic radiosurgery on their cochlear nerves in the internal auditory canal with a 4 mm collimator focusing of a gamma-unit. Maximum doses of 10, 20, 30, 40, 60, 80, 100, 200 and 500 Gy were administered. After the radiosurgery, auditory brain stem responses (ABR) and the behavior of the rabbits were evaluated periodically. At the conclusion, histological investigations were performed. No physiological or histological findings were observed from doses of 30 Gy or below during the 12 month period after the radiosurgery. A dose of 100 Gy caused a severe ABR threshold elevation, vestibular dysfunction and facial palsy. Necrosis and demyelination of nerves were observed pathologically. In this study, we determined that the safe dose to the normal cochlear nerve during radiosurgery was under 40 Gy in rabbits, and complications seemed to vary due to individual differences in radiation tolerance.

Animals↗
PubMed1997

Inner ear disorders due to pressure change.

We reviewed the records of 136 patients who had inner ear disorders including hearing loss and vertigo caused by pressure change. We divided them into three groups, according to the aetiology: group A, change in atmospheric pressure (diving, airplane travel, etc.); group B, rapid change in ear pressure in normal atmosphere (nose blowing, heavy lifting, etc.); and group C, blast injury. A flat initial audiogram was the most common type in groups A and B. In group C, high-tone hearing loss was the most common type of audiogram. These results correspond to findings previously reported in animal experiments. Exploratory tympanotomy was performed more than 12 days after the pressure change in 16 patients. Although the vertigo disappeared after surgery, hearing did not improve.

Adolescent↗
PubMed1997

[Electrophysiological study of inner ear barotrauma in guinea pigs; comparison with scanning electron microscopic findings].

To investigate the mechanism of barotrauma to the inner ear, we used electrophysiologic methods to evaluate guinea pigs exposed to such trauma, and compared the findings with those observed by scanning electron microscopy (SEM). Guinea pigs with good Preyer's reflexes were studied. In those animals that showed a loss of or decrease in Preyer's reflexes and/or nystagmus following exposure to an increase and decrease in pressures in a high-pressure chamber, we measured compound action potentials (CAPs) and cochlear microphonics (CMs) 7-11 days after the exposure. The pressure was increased from 1 ATA to 2 ATA over 30 sec and maintained for 10 min, then pressure was decreased to 1 ATA over 30 sec. Specimens obtained from animals in which CAPs and CMs could be measured were prepared for SEM examination. CAPs and CMs were measured at decreasing 5 dB increments to the visual threshold level of detection with tone bursts at 1, 2, 4 and 8 kHz. Based on the CAPs measured 7-11 days after exposure, guinea pigs were divided into two groups by CAP thresholds, those with severe damage and those with mild damage. None of the animals showed moderate damage. The group with high CAP thresholds showed severe damage to hair cells on SEM, while the group with low CAP thresholds showed no specific morphological abnormalities on SEM. It appeared that some guinea pigs with normal SEM findings following barotrauma to the inner ear did not achieve complete recovery of hearing. From these results, it was speculated that some animals had sustained reversible damage in the mild group and that these animals had recovered from moderate damage. The elevation of CMs was usually not high compared to that of CAPs in the high frequency area, and 4 animals showed CAP and CM separation above 30 dB at 8 kHz. These findings suggested that the group with severe damage exhibited multiple patterns of injury.

Action Potentials↗
PubMed1997

[The effect of CO2 and apnea on cochlear and middle ear blood flow in guinea pigs].

The effect of 10% CO2 (in air) and apnea on cochlear blood flow (CBF) and middle ear blood flow (MEBF), capillary vessel diameters and blood pressure (BP) were investigated in guinea pigs. Intravital microscopic techniques (IVM) using video system, and laser Doppler flowmetry (LD) were used. MEBF was measured in the blood vessels of the middle ear mucosa over the cochlea and CBF was measured in the lateral wall vessels in the second or third cochlear turn. During 10% CO2 respiration for 10 min, the highest vessel diameter dilated about 11% in the middle ear and 5% in the cochlea. During 5 minutes apnea, the highest vessel diameter constricted about 30% in the middle ear and 5% in the cochlea. Elevation of PCO2 dilate blood vessels with constant PO2, but constriction of blood vessels as observed in extremely low PO2 range even if PCO2 was elevated. The ratio of the change in blood flow volume to the change in BP was obtained after the change in blood flow volume was calculated from blood flow velocity and blood vessel diameter. The mean change of ratio in MEBF was a 10% decrease with 10% CO2, 28% decrease with apnea in IVM. The mean change of ratio in CBF was a 44% increase with 10% CO2, 14% increase with apnea in IVM, 67% increase with 10% CO2, 42% increase with apnea, in LD. The change of CBF in LD was about 20% larger than in IVM. Our results showed that CBF belonging to vertebral artery system was more strongly maintained in association with autoregulation even under conditions of low PO2 or high PCO2 compared to MEBF in the external carotid artery system. It was suggested that blood flow behavior was significantly different between the middle ear and inner ear.

Animals↗
PubMed1997

Morphological studies on middle ear barotrauma in guinea pigs.

Experimental middle ear barotrauma was studied morphologically. White guinea pigs were placed in an experimental hyperbaric chamber, and middle ear barotrauma was created by increasing the pressure in the hyperbaric chamber from 1 atmosphere absolute (ATA) to 2 ATA using pure oxygen, maintaining the pressure at 2 ATA for 10 minutes, then again reducing the pressure to 1 ATA. Selected experimental animals were decapitated immediately after, one day after, one week after, or weeks after pressure loading, and their middle ears were examined by a light microscope (LM), a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Hemorrhaging in the tympanic cavity immediately after pressure exposure was apparent even macroscopically. LM also revealed evidence of submucous hemorrhage. Submucous edema was seen in the "one week after" cases. SEM showed a minor loss of cilia in some ciliated cells just after the experiment. In nonciliated cells, the terminal web was somewhat indistinct in the "one week after" cases. TEM also indicated a minor loss of cilia in some ciliated cells in "one day after" cases as well as apparent vacuoles within the cells. These findings suggest that although trauma during compression is more marked than during decompression, recovery from this damage progressed with time.

Animals↗
PubMed1996

Stapes fixation associated with symphalangia.

We describe a 10-year-old boy and his 9-year-old sister, both of whom had bilateral hearing loss associated with ankylosis of the proximal interphalangeal joints (symphalangia). They had no other abnormal findings except hearing loss and ankylosis of the joints of some fingers and toes on systemic examination. The cause of conductive hearing loss in both cases was bony fusion between the stapes and the bone of the oval window niche. There were no other anatomical abnormalities in the middle or the external ear. The patients' hearing improved markedly after stapes surgery. Histopathologic examination of the stapes revealed an abnormal zone of ossification near the anterior annular ligament and calcification in the annular ligament, which seemed to be the cause of the stapes fixation.

Child↗
PubMed1996

HLA associations in otosclerosis in Japanese patients.

Otosclerosis is a disease of the otic capsule that is caused by abnormal resorption and redeposition of bony tissue. Sixty-two unrelated Japanese patients exhibiting clinical otosclerosis were typed for HLA-A, -B, -C antigens. Twenty-one of the patients were also typed for DR antigens. The frequency of HLA-Aw33 was significantly higher in otosclerosis patients than in the control group (24.2% vs 9.5%). This finding suggests that the presence of HLA-Aw33 antigens may be related to an increased susceptibility to otosclerosis or to its clinical outcome.

Adolescent↗
PubMed1996

Eustachian tube function and middle ear barotrauma associated with extremes in atmospheric pressure.

Eustachian tube (ET) function was studied by means of sonotubometry and tubotympano-aerodynamography (TTAG) prior to and following exposure to hypobaric or hyperbaric conditions. Forty normal adults were subjected to hypobaric pressure. Fifty adults who underwent hyperbaric oxygen (HBO) therapy also were studied. Following hypobaric exposure, 14 of 80 ears (17.5%) exhibited middle ear barotrauma. Following hyperbaric exposure, 34 of 100 ears (34%) exhibited middle ear barotrauma. Dysfunction of the ET, characterized by altered active and passive opening capacity, was more prevalent following exposure to extremes in atmospheric pressure compared to baseline. The ET function, which was impaired after the first HBO treatment, improved gradually over the next 2 hours. Overall, however, ET function was worse after the seventh treatment. The patients who developed barotrauma exhibited worse ET function prior to hypobaric or hyperbaric exposure. Thus, abnormal ET function can be used to predict middle ear barotrauma prior to exposure to hypobaric or hyperbaric atmospheric pressure.

Adult↗