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Biomedical subjects

H Funai

Publications and source records attributed to H Funai.

35 records · Page 2Linked to original sources
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

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↗
PubMed1980

Mechanical and neural interactions between binaurally applied sounds in cat cochlear nerve fibers.

Most single fibers of the cochlear nerve (CN) in 22 cats exhibited effects of mechanical interaction in one cochlea between two sounds applied binaurally, similarly to results in two cats in which the contralateral CN was transected. In 11 of 189 fibers, the spontaneous and/or the sound-evoked activity was suppressed by a contralateral intense best-frequency sound; this indicates an interaural neural inhibition, probably through the olivocochlear bundle (OCB). The inhibited fiber population was small, and the intensity differences between the binaural sounds were exceptionally large, so that a simple negative feed-back function via the OCB is not likely.

Acoustic Stimulation↗
PubMedDate not supplied

An electrophysiologic study of experimental perilymphatic fistula.

This study was undertaken to elucidate the mechanism that causes sensorineural hearing loss in clinical cases with perilymphatic fistula. Perilymph was experimentally aspirated through the round window membrane in 17 guinea pigs. The extent of cochlear damage was examined electrophysiologically as well as histopathologically. Immediately after aspiration, several types of changes in summating potential (SP) were observed. Two animals without a polarity change of the SP showed only slight threshold changes in both cochlear microphonic and action potentials, and no specific histopathologic changes in the cochlea. Reversed polarity of the SP was observed in three animals, of which one showed a high-amplitude negative SP followed by rapidly progressive hearing loss. Bulging of Reissner's membrane was confirmed histopathologically in this case. The SP disappeared in the remaining 12 animals. In animals with profound electrophysiologic changes, bulging or rupture of Reissner's membrane and damaged hair cells were observed. These findings suggest that an abrupt change in perilymphatic pressure produces morphologic changes in the membranous labyrinth, causing changes in the vibration function of the cochlear partition and in the function of the organ of Corti. Abrupt pressure imbalance may be a causative factor of sensorineural hearing loss in the case of perilymphatic fistula.

Acoustic Stimulation↗
PubMedDate not supplied

Auditory brainstem responses in leptomeningeal metastatic spread. Presentation of 2 cases.

Auditory brainstem responses (ABRs) were recorded in 2 patients with hearing loss caused by leptomeningeal metastatic spread. These recordings showed similar characteristic findings. The absolute latencies of wave V and interwave latencies I-V were exceedingly increased. Definite effects on the wave morphology and latency of wave V were observed with the use of high repetition rates. It is surmised that the hearing loss caused by leptomeningeal metastatic spread is mainly an effect on the auditory nerve and/or the cochlear nucleus. ABR examination is of clinical value in detecting functional abnormalities resulting from leptomeningeal metastatic spread.

Aged↗
PubMedDate not supplied

Endolymphatic hydrops in perilymphatic fistula.

Cochlear hydrops was produced either by injecting artificial perilymph into the subarachnoid space or by sucking perilymph through the round window membrane. The animals were either vitally fixed immediately or kept alive for 1 to 3 months before fixation. Conventional celloidin embedding method was used for serial sectioning. Animals with cochlear hydrops were selected from among 56 guinea pigs; 13 animals were used for the present observation. The cochleas of these animals showed slight to moderate hydrops, while the vestibule and semicircular canals demonstrated either a normal or collapsed endolymphatic space. The pars superior does not develop hydrops. Changes in the saccular wall were not pronounced. One animal developed marked cochlear hydrops with atrophy of both Corti's organ and stria vascularis. The vestibule and semicircular canals showed marked collapse. The ductus reuniens and the saccule were completely obstructed. Marked cochlear hydrops was produced by blocking the longitudinal flow of endolymph. It is assumed that there may be cochlear hydrops in clinical cases of perilymphatic fistula, with various pathologies of the endolymphatic space of the vestibule and semicircular canals.

Animals↗