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Biomedical subjects

M Aoyagi

Publications and source records attributed to M Aoyagi.

230 records · Page 13Linked to original sources
PubMedDate not supplied

CT detection of facial canal dehiscence and semicircular canal fistula: comparison with surgical findings.

OBJECTIVE: The purpose of this study was to determine the accuracy of high resolution CT (HRCT) in the detection of facial canal dehiscence and semicircular canal fistula, the preoperative evaluation of both of which is clinically very important for ear surgery. MATERIALS AND METHODS: We retrospectively reviewed the HRCT findings in 61 patients who underwent mastoidectomy at Yamagata University between 1989 and 1993. The HRCT images were obtained in the axial and semicoronal planes using 1 mm slice thickness and 1 mm intersection gap. RESULTS: In 46 (75%) of the 61 patients, the HRCT image-based assessment of the facial canal dehiscence coincided with the surgical findings. The data for the facial canal revealed sensitivity of 66% and specificity of 84%. For semicircular canal fistula, in 59 (97%) of the 61 patients, the HRCT image-based assessment and the surgical findings coincided. The image-based assessment in the remaining two patients, who both had massive cholesteatoma, was false-positive. CONCLUSION: HRCT is useful in the diagnosis of facial canal dehiscence and labyrinthine fistula, but its limitations should also be recognized.

Adolescent↗
PubMedDate not supplied

Reliability of 80-Hz amplitude-modulation-following response detected by phase coherence.

The reliability and frequency specificity of the 80-Hz amplitude-modulation-following response (80-Hz AMFR) during sleep detected by phase coherence as a measure of the hearing threshold was evaluated in 169 affected ears of 125 children with hearing impairment. The 80-Hz AMFR at a carrier frequency of 1000 Hz was monitored in all 169 ears and the auditory brainstem response (ABR) elicited by 1000-Hz tone pips was evaluated in 93 ears. Both responses were examined during sleep, and the thresholds were compared with the behavioral hearing threshold, which was determined by standard pure-tone audiometry or play audiometry. In 24 ears of 22 children with various patterns of audiogram, the 80-Hz AMFR was examined at different carrier frequencies, and the threshold pattern was compared with the pure-tone audiogram to investigate the frequency specificity of 80-Hz AMFR. The mean and standard deviation of the difference between the 80-Hz AMFR at a carrier frequency of 1000 Hz and pure-tone thresholds of 1000 Hz was 3.8 and 12.9 dB, and that between the ABR and pure-tone thresholds was 6.8 and 14.1 dB, respectively. The threshold patterns of 80-Hz AMFR clearly followed the corresponding audiogram patterns in all types of hearing impairment. The measurement of 80-Hz AMFR thus appears to be accurate in hearing assessment and to have good frequency specificity in children during sleep.

Adolescent↗
PubMedDate not supplied

Short-term outcome and prognosis of acute low-tone sensorineural hearing loss by administration of steroid.

Acute low-tone hearing loss (ALHL) is a typical type of hearing loss in Ménière's disease and thought to be caused by endolymphatic hydrops in the inner ear. We treated 40 patients with ALHL by administration of the steroid and the early outcome and prognosis of the hearing level was retrospectively evaluated. The prognosis was generally determined within 7-10 days after administration of steroid. High-dose steroid cured some patients who failed to recover with low-dose steroid therapy. Our results showed that steroid is one of the effective therapies for ALHL and supported that etiology of ALHL involves an immune response.

Acute Disease↗
PubMedDate not supplied

Bilateral hearing loss due to viral infection.

We encountered 2 patients with bilateral hearing loss due to the mumps virus in one and the varicella-zoster virus in the other. Each virus was identified by a serological test, and virus-specific IgG and IgM antibodies were detected in the sera. In both patients, hearing loss on the contralateral side occurred a few days after that on the initially affected side, but vestibular function was normal. Although therapy included the administration of steroids, antiviral agents and hyperbaric oxygen, the bilateral hearing loss remained unchanged in these 2 patients. Both required the use of a hearing aid after discharge.

Adult↗
PubMedDate not supplied

Regional cerebral blood flow measured by the gamma camera after direct injection of 133Xe into the distal stump of the occluded middle cerebral artery.

Regional cerebral blood flow (rCBF) was measured after intracarotid injection of 133Xe concurrently with measurements of local cerebral blood flow (LCBF) after injection of 133Xe directly into the distal stump of the occluded middle cerebral artery (MCA) by the use of the gamma camera after producing experimental ischemia in baboons by occluding the MCA. Regional MCA stump pressure (rMCAP) was also measured. Regions of ischemia assessed by intracarotid injection of 133Xe correlated well with the territory of infarct defined by injection of 133Xe into the distal MCA stump. Flow values in ischemic regions obtained by direct injection of 133Xe into the MCA were 15% to 20% lower than those obtained by intracarotid injection of 133Xe. Possible explanations for these differences are discussed. During induced hypertension autoregulation in ischemic areas was abolished and paradoxical responses of LCBF and rMCAP to changes in arterial carbon dioxide tension (PaCO2) were confirmed.

Animals↗
PubMedDate not supplied

Visual suppression of caloric nystagmus in normal individuals.

The effects of opening of the eyes and of ocular fixation upon caloric nystagmus were investigated during the period of maximum intensity of caloric nystagmus in a series of 32 normal individuals. The percentage reduction in slow-phase velocity induced depended upon the test conditions, but, on the other hand, did not depend upon the temperature of the water applied as caloric stimulus. This latter fact favors the theory of visual suppression of the caloric test. Another striking finding was that a clear correlation definitely existed between the percentage reduction of suppression in slow-phase velocity and that in the multiplication product of amplitude by nystagmus frequency (P.A.F.) during the period of eye opening and ocular fixation. The percentage of suppression in slow-phase velocity is interchangeable with that in P.A.F., which broadens the practical scope of the routine test.

Adolescent↗
PubMedDate not supplied

Visual suppression of caloric nystagmus in cats.

A newly devised animal box with which caloric tests can be easily performed in the awake cat is presented. This device is also useful for position and optokinetic tests. Visual suppression of caloric nystagmus was investigated in such vertebrates as monkeys, cats and rabbits. There was a definite species difference in the rate of visual suppression of caloric nystagmus. It may be that the difference among species is due to a difference in fixation function among animal species.

Animals↗
PubMedDate not supplied

Loss of visual suppression of caloric nystagmus in cats.

Loss of visual suppression (VS) of caloric nystagmus was produced after creating flocculus lesions. The flocculus receives visual signals through a climbing fiber pathway via the inferior olive (IO) and through a mossy fiber pathway (MF) presumably via the superior colliculus (SC). In order to elucidate the prefloccular nuclei responsible for VS of caloric nystagmus, VS of caloric nystagmus was investigated after making lesions in such nuclei as the SC and the IO in 42 cats. After the IO lesion, VS of caloric nystagmus was revealed in all IO-lesioned cats throughout the whole experimental course. After the SC lesion, loss of VS was constantly observed and persisted in 7 out of 9 cats. Hence, the MF pathway via the SC is believed to be the most likely candidate for the immediate modification of the vestibuloocular reflex by visual stimuli.

Animals↗
PubMedDate not supplied

Frequency specificity of amplitude-modulation-following response detected by phase spectral analysis.

To investigate the frequency specificity of steady-state responses elicited with a sinusoidally amplitude-modulated tone (amplitude-modulation-following response, AMFR), AMFR at different carrier frequencies were examined in 15 subjects with normal hearing, 12 patients with abrupt high-frequency hearing loss, 5 patients with low-frequency hearing loss and 1 patient with mid-frequency hearing loss. The stimulus was a sinusoidally amplitude-modulated tone with a modulation frequency of 40 Hz and modulation depth of 95%. Carrier frequencies were from 250 to 4000 Hz in normal subjects and from 250 to 8,000 Hz in hearing-impaired subjects. Fridman's phase spectral analysis was conducted for automatic detection of response. The thresholds of AMFR were distributed within 30 dB nHL at all carrier frequencies in normal subjects. In the hearing-impaired subjects, AMFR thresholds were between 0 and 25 dB above the behavioral threshold at all carrier frequencies. The threshold patterns of AMFR detected by phase spectral analysis very closely resembled the corresponding audiogram patterns in all types of hearing impairment. AMFR is thus shown to have a very good frequency specificity.

Acoustic Stimulation↗
PubMedDate not supplied

Application of fast Fourier transform to auditory evoked brainstem response.

The current application of fast Fourier transform (FFT) to the analysis of auditory evoked brainstem response (ABR) is reviewed under four categories: (1) digital filtering, which facilitates isolation of fast and slow components from the same ABR wave, is the most common use of FFT; (2) power spectral analysis: this seems significant in ABR for isolating and analysing slow, middle and fast components from the Fourier components around each peak of the power spectrum with a three-peak pattern by inverse fast Fourier transform; (3) cross correlation function shows the relationship between two signals being analysed from the viewpoint of their phase. Clinical applications are used in the diagnosis of multiple sclerosis and for automatic detection of ABR; and (4) phase spectral analysis: the synchrony measure method (Fridman, 1984) is a type of phase spectral analysis. In this method, the phase variances of selected Fourier components are calculated, from among 10 averaging groups of 200 sweeps in the same stimulating conditions, to determine the presence or absence of a response. The clinical application of this method to the automatic evaluation of ABR is discussed.

Adult↗