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Biomedical subjects

S Funasaka

Publications and source records attributed to S Funasaka.

At least 37 records · Page 2Linked to original sources
PubMed1990

Dimensions of the scala tympani in the human and cat with reference to cochlear implants.

The width, height, and cross-sectional area of the scala tympani in both the human and cat were measured to provide dimensional information relevant to the design of scala tympani electrode arrays. Both the height and width of the human scala tympani decreased rapidly within the first 1.5 mm from the round window. Thereafter, they exhibit a gradual reduction in their dimension with increasing distance from the round window. The cross-sectional area of the human scala tympani reflects the changes observed in both the height and width. In contrast, the cat scala tympani exhibits a rapid decrease in its dimensions over the first 6 to 8 mm from the round window. However, beyond this point the cat scala tympani also exhibits a more gradual decrease in its dimensions. Finally, the width of the scala tympani, in both human and cat, is consistently greater than the height.

Anatomy, Comparative↗
PubMed1990

[Changes of the threshold level in patients with 22-channel cochlear implant].

Psychophysical responses of the patients to electrical stimulation were examined in order to clarify long-term effects of the cochlear implant in 9 patients who had received a 22-channel cochlear implant. Measured items were the minimal threshold level (T-level), the maximum comfortable level (C-level), and the dynamic range between T- and C-level. Measurements were repeated for each electrode every three months over more than 6 months. Following results were obtained. 1) The changes of the T-level were classified into four types as follows, a type with no change, a type with gradual decrease, a type with decrease in two to three months followed by gradual increasing threshold and a type with gradual increasing just after surgery. Even in a last type, the maximum increase in the T-level did not exceed 200 microA and, in most cases, these changes were stabilized within a few months after implantation. 2) The dynamic range gradually increased. It was obvious in both in the middle and apical electrodes, while such increased threshold was not observed in the basal electrodes. 3) In some cases, a few basal electrodes could not been used since they caused uncomfortable sensation or those dynamic ranges became below a certain extent. As a result, it was suggested that the electrical stimulation had not induced serious degeneration of the ganglion cells and the auditory nerve fibers. The reduction in the number of usable electrodes might be due to the surgical trauma to the intracochlear tissue. Therefore, exposing of the scala tympani should be minimal in order to avoid the damage of the cochlea.

Adult↗
PubMed1989

[Estimation of surviving auditory nerve by electrically evoked auditory brainstem response (FABR)--comparison between extra-cochlear stimulation and intra-cochlear stimulation].

This study investigated the possibility of using electrically evoked auditory brainstem response (EABR) for predicting surviving spiral ganglion cell populations. EABR recordings were made from six kanamycin induced deaf cats by the round window monopolar stimulation (RW) and the scala tympani bipolar stimulation (ST). On completing the electrical stimulation, each animal was sacrificed and prepared for histological examination. The spiral ganglion cell populations were estimated by classifying them into four groups (0-25%, 25-50%, 50-75%, 75-100%) as a percentage of survival cells under magnification. EABR thresholds and input-output function of amplitude were compared with microscopic findings of surviving spiral ganglion cell populations. The results were as follows: 1) The rate of amplitude growth in response to increased stimulus intensity of electrically evoked potentials from ST was gradual, but that of RW was steep. 2) The vestibular potentials were elicited by RW, and at a lower stimulus intensity the RW waveform began to become distorted by the myogenic potentials. 3) EABR threshold was a poor predictor of surviving spiral ganglion cell populations. 4) There was a correlation between surviving spiral ganglion cell populations and the slope of the input-output functions of ST EABR. However, there was no correlation between that of RW EABR and the slope.

Animals↗
PubMed1989

[Direct observation of the tympanic cavity by the superfine fiberscope].

As a clinical test, direct observation of the middle ear should be ideally performed without any surgical intervention such as myringotomy. This paper reports a newly invented superfine fiberscope which makes it possible to insert through the eustachian tube, and direct views of the middle ear structures on normal subjects and patients. The patients were of a small cholesteatoma and traumatic dislocation of the ossicular chain. All of them were tested with local anesthesia in outpatient clinic. This superfine fiberscope was of great value in observing of middle ear structures as a diagnostic instruments, as that no surgical intervention was necessary in the procedure.

Adult↗
PubMed1988

Tympanometry using a sweep-frequency probe tone and its clinical evaluation.

In this new tympanometric system, air pressure in the external meatus is kept constant at either -200 daPa or 0 daPa. The frequency of the probe tone is swept from 220 to 2,000 Hz (or 2,500 Hz, if necessary) in 4 s. During this frequency sweep, sound pressure in decibels and phase angle in degrees in the external meatus are sampled and the differences in sound pressure and phase angle measured at -200 and 0 daPa pressures are computed. These results are figured as a frequency-sound pressure curve and a frequency-phase angle curve. From the study on 8 fresh human cadaver temporal bones, four parameters in these curves are selected by discriminant analysis to provide diagnostic criteria: the minimum value and the 0-cross frequency of the frequency-sound pressure curve and the maximum value and its frequency of the frequency-phase angle curve. Normal parameters were determined in 50 normal ears. Evaluation of 40 patients with ossicular disorders revealed that 10 out of 12 cases of ossicular discontinuity and 5 out of 6 cases of malleus and/or incus fixation were correctly diagnosed. For stapes fixation, the diagnosis was correct in 12 out of 22 ears. This system is useful in the clinical diagnosis of ossicular disorders, producing a collection of curves and parameters that are distinctively different for the ossicular discontinuity and the ossicular fixation.

Acoustic Impedance Tests↗
PubMed1987

Speech perception with multi-channel cochlear implant of short duration pulse strategy.

A multi-channel cochlear implant (Nucleus type) was implanted in a 40-year-old female Japanese patient who became totally deaf after meningitis. The formant-based speech processing strategy was used, but a narrow pulse width of 22-42 microseconds was required because of intermittent difficulty in controlling the pulse amplitude. The patient was tested with a speech tracking test and could recognize 24 bunsetsues (the minimum meaningful unit of the Japanese sentence) per minute using the cochlear implant plus lipreading and 14.3 bunsetsues for the lipreading alone after 3.5 months' training. The patient was also able to understand usual conversational sentences spoken a little slowly. Scores of vowel and consonant tests reached 70% and 54% respectively for the cochlear implant alone, and 100% and 73% for the cochlear implant plus lipreading. This study has also shown that cochlear stimulation with very narrow pulse widths can be used, and restore speech comprehension ability for the Japanese.

Acoustic Stimulation↗
PubMed1986

Stimulus duration and waves of auditory brainstem response.

This study was conducted to investigate the effects of stimulus duration on auditory brainstem response (ABR) waveform. Stimuli were 3-kHz tone bursts with 1 ms rise/fall times and durations of 5, 10, 20 and 30 ms. They were delivered at interstimuli intervals ranging from 80 to 140 ms. Latency and amplitude increases were observed in waves V and VI as the stimulus duration increased, whereas wave III showed no increase in latency, but decreased in amplitude. Animal experiments showed that the slowly rising curve of the response with increasing stimulus duration results in an increase in the peak latency and in the amplitude of the slow component of the ABR. Thus the change in ABR waveform observed when the duration of the stimulus was increased is not explained by a recovery process of the nervous system, but is possibly mediated by the slow component of the ABR.

Acoustic Stimulation↗
PubMed1984

Sweep-frequency tympanometry: its development and diagnostic value.

This reports a newly developed tympanometric system using a sweep-frequency probe tone. For a sweep-frequency tone ranging from 220 to 2 000 Hz, measurements of sound pressure (P) and phase were performed at ear canal pressures of 0 and -200 mm H2O. The results were expressed as a sound pressure curve (P0-P-200 in decibels), a phase curve (formula: see text) and a polar curve (formula: see text) against probe tone frequency. Both the frequency at which the sound pressure curve crossed the 0-dB difference line and the peak frequency of the phase curve shifted lower than normal for ossicular disruption and higher than normal for ossicular fixation. Changes in the sound pressure curve and in the phase curve were exaggerated for ossicular disruption and limited for fixation. As the result of these, the polar curve showed an expanded type for disruption and a compressed type for fixation. A review of 220-Hz tympanograms and of the polar curves for 10 patients demonstrated that the latter permitted a better discrimination among ossicular disorders.

Acoustic Impedance Tests↗
PubMed1983

Human frequency-specific whole-nerve response by use of frequency-modulated tone.

Based on the results of animal experiments performed previously, a human study of the compound action potential (AP) to frequency-modulated (FM) tone was achieved, using the transtympanic electrode, in order to obtain frequency-specific APs. Clearly recognizable responses were elicited by a downward shift of 20% in the frequency of a 515-, 1 150- or 2 230-Hz pure tone (with a slight amplitude increase). The latency for each frequency was investigated at different intensities. The latency is greater for lower-frequency tones and, as in the animal experiments, this latency increase agrees with the traveling delay for the intensity range used in this study. The latency-intensity curves of the three frequencies do not tend to converge with increase in the intensity of the tone. The latency at moderate intensity is similar to that for the short tone burst at threshold intensity. These findings suggest that the FM tone in downward direction can be a frequency-specific stimulus even at relatively high intensities. Combined use of the tone burst (low intensity) and this FM tone (high intensity) may be useful in clinical tests.

Action Potentials↗
PubMed1983

Experimental study on the effect of inferior colliculus lesions upon auditory brain stem response.

The relationship between the activity of the inferior colliculus and each component of the auditory brain stem response (ABR) was investigated in rats using an electrical coagulation method. The ABR seems to be a composite of slow and fast waves, and the central nucleus of the inferior colliculus is more important for the slow wave than for the fast waves. There was little effect on the shape and latency of the fast waves of the ABR when the destruction was limited to the central nucleus. When the lesion was extended to or located in the lateroventral part of the inferior colliculus, where the nerve fibers of the lateral lemniscus penetrate into the inferior colliculus, potentials 5 and 6 were abolished, but potential 4 remained with a slightly prolonged latency. These findings suggest that the structures peripheral to the inferior colliculus play an important role for the generation of potential 4, and the inferior colliculus, particularly its lateroventral part, is essential for generation of potentials 5 and 6.

Animals↗
PubMed1982

Advanced necrotizing external otitis treated by suboccipital craniectomy.

Necrotizing external otitis is a destructive infection caused by Pseudomonas aeruginosa. It may spread to surrounding soft tissue, cartilage and bone from the skin of the external canal and cause cranial nerve palsy. Most of the disease occurs in elderly diabetics and is accompanied by high mortality in an extended case in spite of intensive antibiotic therapy. A case of advanced necrotizing external otitis with palsies of VI to XII cranial nerves was presented. The patient, 69-year-old male, took a favorable course after complete debridement by suboccipital craniectomy followed by intensive antibiotic therapy. This procedure was performed by co-operation with a neurosurgeon. Characteristics of the pathology, criteria for the diagnosis and method of treatment are discussed; the authors stress the importance of early diagnosis and necessity of complete meticulous debridement on the extended case with multiple nerve palsies.

Aged↗