Biomedical subjects

M Aoyagi

Publications and source records attributed to M Aoyagi.

At least 127 records · Page 7Linked to original sources

PubMed1994

Postoperative changes in the contralateral auditory brainstem response after microvascular decompression in cases of trigeminal neuralgia.

Postoperative changes in auditory brainstem response (ABR) in 40 patients with trigeminal neuralgia (TN) who underwent microvascular decompression (MVD) were analyzed. A high proportion (60%) were found to have a decrease in the latency of wave V in the contralateral (unaffected) ABR in the postoperative period. In some cases, a decrease in the latency of wave V was found on the unaffected side postoperatively while an increase was found on the affected side. Furthermore, in one case it was found that an improvement of the shortened latency of wave V on the unaffected side occurred in parallel with a recovery of prolonged latency on the affected side. This indicates that the decrease in the latency of wave V on the unaffected side corresponds to some retrocochlear lesion produced by MVD on the affected side, and shortened latency is considered to be a result of damage to the efferent system of the auditory pathway.

Adult↗

PubMed1994

Three frequency component waveforms of auditory evoked brainstem response in spinocerebellar degeneration.

Under adequate stimulus intensities, the power spectra of normal auditory evoked brainstem responses (ABRs) are composed of three major components: 0-350 Hz, 350-700 Hz and 700-1200 Hz. By means of a digital filter using fast Fourier transform, three ABR waveforms consisting of each frequency component of the power spectrum were obtained. The significance of these three component waveforms in the analysis of ABR abnormality was estimated in 30 patients with spinocerebellar degeneration (SCD). In conventional wave latency analysis, 9 out of 30 patients (30%) had abnormal ABRs, the main abnormality being prolonged interpeak latencies of waves I-III, I-V and the disappearance of wave V. On the other hand, component waveforms were abnormal in 82.5% of the cases. These results suggest that analysis of ABRs by the use of component waveforms is useful for detecting abnormality in the brainstem auditory pathway in SCD patients.

Audiometry, Evoked Response↗

PubMed1994

Phase spectral analysis of auditory brainstem response in cats.

In order to apply the phase spectral analysis of auditory brainstem response (ABR) to the clinical diagnostic test, the phase spectra of ABRs were investigated under adequate stimulus intensity in normal cats and after the destruction of acoustic nerve and brainstem auditory pathways in cats. The results were as follows; i) In normal ABRs, the phase spectra were mainly composed of three frequency components at 0-300 Hz (component A), 300-900 Hz (component B) and 900-1500 Hz (component C). ii) A greater decrease of the component synchrony measure (CSM) occurred if ipsilateral destruction was performed in a peripheral lesion. Lesions of the auditory pathway were followed by a decrease of the CSM of component C in response to contralateral stimulation. These results suggest that the phase spectral analysis of ABRs has significant clinical value in the detection of brainstem lesions.

Acoustic Stimulation↗

PubMed1994

ABR topographic mapping with digital filtering using fast Fourier transform.

The power spectrum of normal ABR consists of three major parts: low (0-350 Hz: component A), middle (350-700 Hz: component B) and high (700-1200 Hz: component C) frequency components. With digital filtering using fast Fourier transform (FFT), three component waveforms of ABR were obtained and designated as component A, B and C. Component A has a positive peak which corresponds to wave V or the slow component of the original ABR. Component B has three positive peaks (B1-B3) which correspond to wave I, III and V, and component C has five positive peaks (C1-C5) which correspond to wave I-V. These three component waveforms of ABR were analyzed topographically in normal hearing adults and cats. In addition, changes in the topography of three component waveforms of ABR were studied in a series of experimentally induced lesions in the brainstem auditory pathway in cats. The following results were obtained: i) The highest voltage (HV) area of component B1 was detected on the ipsilateral side in normal adults and cats. The HV areas of component C1, C2 and C3 in normal adults and C1, C2 in normal cats were detected on the ipsilateral side. ii) There was a correlation between changes in component C and the lesion site of the auditory pathway. Component C appears to be the most sensitive indicator of the lesion site of the brainstem.

Acoustic Stimulation↗

PubMed1994

Measurement of cochlear basilar membrane traveling wave velocity by derived ABR.

Auditory brainstem response (ABR) can be used to measure the basilar membrane traveling wave velocity (TWV). Traveling wave velocity was calculated from the latency difference between wave V of different derived ABR and the cochlear location distance between the appropriate derived band center frequency. The latency of wave V of derived ABR produced by 6 noise-masked ABR using high pass filtered noise and the location of the corresponding cochlear partition (distance from the stapes foot-plate) were measured, and five traveling wave velocities were estimated based on this parameter. Ten subjects with normal hearing, 7 patients with Meniere's disease, and 8 patients with sensorineural hearing loss were used in this study. The traveling wave velocity in the sensorineural hearing loss group was within normal limits at all frequencies, whereas the traveling wave velocity at 8 kHz in the Meniere group greatly exceeded that of the normal and sensorineural hearing loss group.

Acoustic Stimulation↗

PubMed1994

Acoustic neuroma presented as repeated hearing loss.

Up to 15% of patients with acoustic neuroma may have a history of sudden hearing loss. Recovery from sudden hearing loss with acoustic neuroma is rare. In this paper, a case of bilateral acoustic neuromas presented as repeated sudden hearing loss with recovery on the left side after removal of right-sided tumor were reported. She experienced three episodes of sudden hearing loss, showing various types of audiograms and ABR on the left side. There was no relationship between the type of audiograms and ABR findings. Factor influencing ABR might be different from the cause of hearing impairment. Acoustic neuromas can be reliably identified by performing MRI properly. However, MRI showed negative scan and ABR finding was abnormal in the first episode of our case. ABR continues to be a sensitive diagnostic back-up test to MRI for the detection of acoustic neuromas. Even if the patient, who showed abnormal ABR findings suggesting retrocochlear pathology, showed normal MRI, acoustic neurinoma should not be ruled out and both ABR and MRI must be re-examined at regular intervals.

Adult↗

PubMed1994

Effects of aging on hearing results in tympanoplasty.

The effects of aging on the preoperative and postoperative hearing results of tympanoplasty were assessed in 642 patients with chronic suppurative otitis media (COM) or cholesteatoma (CHL). Analysis focused on the correlation between hearing results and age for each disease and type of tympanoplasty. Data were evaluated by calculating the regression line, mainly using second order polynomial regression analysis. Averaged air and bone conduction thresholds (PTA) in patients were appreciably poorer in younger patients and increased with age, compared with physiological hearing impairment in old age (presbyacusis). Regression lines for PTA of air and bone conduction in patients and for normal data (air conduction) separated from each other after the age of 30 and hearing impairment gradually accelerated with age. Means of air-borne gap, however, were almost the same in each age group, though hearing thresholds in individual patients were distributed widely. This was more dominant in patients who had undergone type III or IV tympanoplasty than those with type I tympanoplasty, and in patients with COM than with CHL. Labyrinthine function thus appears to be gradually aggravated with age in patients with chronic inflammatory ear disease. Patients with chronic otitis media should be thus recommended to undergo tympanoplasty at an early age.

Adolescent↗

PubMed1994

Frequency analysis of transiently evoked otoacoustic emissions in sensorineural hearing disturbance.

Transiently evoked otoacoustic emissions (TEOAE) are present in nearly all normal hearing ears and recognized as useful for objective auditory screening. In the spectral analysis of TEOAE with click stimuli, the normal power spectrum of TEOAE has yet to be obtained. In this study, the normal range of the power spectrum was determined for 42 adults with normal hearing and compared with sensorineural hearing disturbance data. The power spectrum of TEOAE in normal hearing adults sloped down at high frequencies and was the same for right and left ears in both males and females. For comparison with sensorineural hearing disturbance, a significant correlation between the audiogram and power spectrum of TEOAE was sought. Frequency specificity was noted in the power spectrum of TEOAE with click stimulation.

Adult↗

PubMed1994

Slow saccades and quick phases of nystagmus after pontine lesions.

A patient was referred to the university hospital to test eye movements after she had suffered cerebellar hemorrhage one month previously. Examination showed a selective deficit of saccades and quick phases of nystagmus toward the lesion site in the horizontal plane, which was later confirmed pathologically, and which corresponded precisely to the paramedian pontine reticular formation (PPRF). This may suggest that velocities in the quick phase of nystagmus, whether visual or vestibular, and saccades show the same result in PPRF lesion and they share the same neural circuitry in cells located in the PPRF. In the present study, the non-linear saccade velocity-amplitude equation was best-fitted to this patient. Quantitative evaluation of the quick phase may provide a simple and quick reference in saccade slowing.

Brain Diseases↗

PubMed1994

Quantitative assessment of influence of aging on optokinetic nystagmus.

A quantitative assessment of the influence of aging on optokinetic nystagmus (OKN) was investigated using 50 normal adults in ages ranging from 30 to 70 years. In linear stimulus-induced OKN, a statistically significant difference was demonstrated in slow-phase OKN velocity only between the 30-59 year old age group and the 70-79-year-old age group, when OKN stimulus was more than 60 degrees/s. Step stimulus-induced OKN was investigated in the same age groups in order to compare aging effects upon slow-phase OKN velocity. No statistically significant difference was found in slow-phase OKN velocity between younger age groups and the oldest age group. There was no significant difference in fast-phase velocity among the age groups. Thus, step-induced OKN has a wider clinical application than linear stimulus-induced OKN.

Adaptation, Physiological↗

PubMed1994

Computer analysis for routine electronystagmography tests.

A computer program has been developed for on-line analysis of routine electronystagmography (ENG) tests. With this system, data acquisition of eye movements and stimulus signals obtained from ENG are accomplished at a rate of 200 Hz through a 12-bit analog-digital converter. A small spotlight for eye tracking tests is sinusoidally driven by a computer-generated analog signal. Six optokinetic stripes projected onto a screen are also controlled by the computer. Seven spots for saccade tests can be turned on or off based on digital signals produced through a digital output device. There are three types of eye movements in this series: nystagmus, pursuit eye movement and saccadic eye movement. An algorithm for the analysis of different eye movements is described in this paper. Recent significant advances in computer technology make it possible to perform such complicated tasks and to accomplish quantitative assessment of any type of eye movements in routine ENG tests. Consequently, computer analysis provides clues to the location of a disease and is very useful as a diagnostic tool in routine ENG testing.

Artifacts↗

PubMed1994

Rebound positional nystagmus as a peripheral origin.

Three cases of rebound positional nystagmus (RPN) are discussed in the present study. In all cases, spontaneous nystagmus was absent in the primary position, but positional nystagmus appeared in the side down position, and then nystagmus in the reversed direction appeared when the patient was returned to the primary position. The characteristics of RPN in the cases we studied were very similar to those of benign positional nystagmus. Tinnitus was accompanied with vertigo in Cases 2 and 3, and the glycerol tests were positive in Cases 1 and 3. There were no other abnormalities of ocular movements, neurological and neuroradiological examinations suggestive of central nervous system disorders indicating that RPN can be ascribed to peripheral lesions. A selective review of the literature is presented.

Electrooculography↗

PubMed1994

Quantitative analysis of oblique ocular movements.

In the present study, oblique saccadic eye movements in the orthogonal and oblique directions were investigated in 10 normal subjects, and a computer program was used to accomplish quantitative assessment of oblique eye movements. Eye movements were recorded with direct-current electronystagmography (DC-ENG) and a 12-bit analog to digital converter was used to collect analog data of horizontal and vertical eye position, and stimulus signals at a sampling rate of 200 Hz. The oblique eye movement was displayed two-dimentionally on a high-resolution color graphic terminal for the evaluation of the trace of eye movements, and the peak velocity and the amplitude of the horizontal, vertical and oblique saccades were calculated. It was frequently found that the tracing line in the oblique saccadic eye movement was not completely straight, but loosely curved. The velocity of the vertical component of the oblique saccade was much lower than that of the horizontal component. This suggests that oblique saccades might be made by synchronized but independent vertical and horizontal pulse generators, and the system developed this time might be very useful for investigation of oblique eye movements in both the clinical and physiological field.

Adult↗

PubMed1994

Clinical advantages of electroneurography in patients with Bell's palsy within two weeks after onset.

One of the advantages of applying ENoG to patients with Bell's palsy resides in its quantitative determinability for the axons which do not undergo wallerian degeneration. The relation between the ENoG value each day after onset and during the recovery process was investigated in 551 patients with Bell's palsy within 2 weeks after onset in order to consider the diagnostic value of ENoG. It was discovered that ENoG on patients with Bell's palsy makes it possible to reveal the extent of wallerian degeneration by 7 days after the onset of palsy. Accordingly, treatment of Bell's palsy should be administered within the above 7 days; as early as 8 days after onset, exact prognostic diagnosis and judgment of therapeutic effect from ENoG values were concluded to be practicable.

Action Potentials↗

PubMed1994

Facial nerve palsy in children: clinical aspects of diagnosis and treatment.

Eighty-two children with facial palsy aged less than 6 years were examined. Sixty-four cases, excluding patients with congenital and traumatic palsy, were distributed through the ages, but a predominant tendency to symptomatic palsy for cases aged less than 2 years was observed. Facial movement scoring was not practical in prognostic diagnosis in cases aged under 4 years, while ENoG was useful in all age-groups. Of 58 cases of acute peripheral facial palsy, 29 were observed clinically but given no treatment, 9 were given steroids, and 16 were given vitamins and other drugs. In the patients with acute peripheral facial palsy in whom a follow up study was performed, 56 cases (96.6%) showed complete recovery. The time of recovery was independent of treatment. Facial palsy in children is considered to have a good prognosis regardless of treatment. Steroid administration thus does not appear to be necessary in children with acute facial palsy.

Acute Disease↗

PubMed1994

Diagnosis and treatment for Bell's palsy associated with diabetes mellitus.

The method of detecting diabetes mellitus and estimating the diabetic control status in patients with Bell's palsy, and the effect of high-dose steroid therapy for Bell's palsy accompanied by diabetes were investigated. From October 1987, hemoglobin A1c (HbA1c) was introduced to detect diabetes in 288 out of 372 patients with Bell's palsy, as a screening test for DM. Thirty-six diabetics with complete facial palsy were treated by high dose steroid therapy as described by Stennert. Hemoglobin A1c was useful in diagnosing diabetes and in assessing the diabetic control. Many patients under diabetic therapy kept their diabetes under good control. In cases of complete palsy, high-dose steroid therapy, at a cure rate of 97.4%, was highly effective in treating diabetes-accompanied Bell's palsy.

Adult↗

PubMed1994

Recording of single fiber electromyography in patients with peripheral facial palsy.

We determined muscle fiber density with single fiber electromyography (SFEMG) to discuss the condition of re-innervation after the recovery of facial movement in cases of peripheral facial palsy. Muscle fiber density was then compared with electroneurography (ENoG) which is thought to correlate with the severity of facial neuropathy in the early stage after the onset. The degree of neuropathy and subsequent recovery of innervation was also discussed. The subjects were 36 patients with peripheral facial palsy (30 patients with Bell's palsy and 6 with Hunt's syndrome), treated at our hospital, in whom ENoG could be recorded within 2 weeks after the onset. Muscle fiber density was determined after the recovery of facial movement. As a control, muscle fiber density was determined in 11 normal adults, and muscles on the healthy side in 23 patients with Bell's palsy. Muscle fiber density was 1.44 +/- 0.15 (mean +/- S.D.) in normal adults and 1.51 +/- 0.18 on the healthy side in patients, showing no significant difference. Data on the affected side were divided into 4 groups according to the minimum ENoG level within 2 weeks after onset and were compared with the normal group. In all cases with an ENoG level of 40% or more, muscle fiber densities were normal, and no significant differences were noted between the affected side and the healthy side. In cases with an ENoG level of less than 40%, muscle fiber density increased significantly with increasing severity of denervation. These findings suggest that collateral sprouting is absent in cases of peripheral facial palsy who show an ENoG level of 40% or more, or no wallerian degeneration.

Action Potentials↗

PubMed1994

Electrophysiological study on the pathology of synkinesis after facial nerve paralysis.

By conducting electrophysiological tests on patients with facial nerve paralysis, the characteristics of synkinesis and the mechanisms of its manifestations were examined. The subjects were 114 patients of facial nerve paralysis on whom electroneurography (ENoG) and the blink reflex were conducted. As a result, it was indicated that synkinesis could be determined by the blink reflex, and that the frequency of synkinesis manifestation increased with severity of paralysis. From examination during the latent period, early component (SI) recognized in the cases of synkinesis was found to be the waveform which passed the fibers with a slow conducting speed. It was not related to the degree of degeneration of nerves for either the severe or light degeneration of nerves. From the above result it was concluded that synkinesis is generated as a misdirection of reproduced nerves.

Adolescent↗