PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “TENSOR TYMPANI”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed1975

Auditory systems of Heteromyidae: functional morphology and evolution of the middle ear.

Middle ears (515) from 26 species of the rodent family Heteromyidae - genera Dipodomys, Microdipodops, Perognathus, and Liomys - were studied both grossly and histologically, for qualitative and quantitative comparisons. Middle ear modifications characteristic of each genus are qualitatively described. Quantitative comparisons are made among the 26 species in the study. Some correlations between middle ear size and other measurements are discussed. The middle ear is an acoustical transformer that for best efficiency must match the impedance of the cochlea to the impedance of the air in the external auditory meatus. It accomplishes this by a pressure increase and a velocity decrease through the combined effects of the lever and areal ratios; however, because the important consideration is a matching of two impedances rather than an absolute pressure increase, the pressure transformer ratio is a less informative measure of the middle ear's efficiency than is the impedance transform ratio. The impedance transformer mechanism is explained (from a morphological point of view), and equations are presented. Dipodomys, Microdipodops, and Perognathus have a theoretical transmission (at the resonant frequency) of 94-100% of the incident acoustical energy; Liomys, 78-80%. The areal ratio of stapes footplate to 2/3 tympanic membrane is remarkably constant among the species, varying only from 0.04 to 0.07: in Dipodomys and Microdipodops this small ratio is due to the very large tympanic membrane; in Perognathus and Liomys it is due to the extremely small stapes footplate. The lever ratio of incus to malleus varies from 0.28 to 0.33 in Dipodpmys and Microdipodops, from 0.37 to 0.46 in Perognathus, and from 0.55 to 0.60 in Liomys. In addition, the middle ear volumes and the morphology of tympanic membrane, ossicles, ligaments, and muscles, all combine to minimize both mass and stiffness. All these data suggest middle ear mechanisms which are very efficient over a broad frequency range. The middle ear modifications found in heteromyids are adaptive in predator avoidance, especially in areas of little natural cover; nevertheless, contrary to expectations, there is no firm relationship between habitat and the extent of these modifications in the 26 species. However, environment did apparently plan an important role in the evolution of the family, and this is discussed.

Acoustics↗
PubMed1978

Mycotic infection of the temporal bone.

Herein is a histopathologic study of the temporal bone changes in three patients with fatal systemic fungal infections. All three patients were compromised hosts who failed to respond to adequate chemotherapy. Interestingly, one patient with cryptococcosis had a unilateral hearing loss as the sole manifestation of cerebral cryptococcosis. The most common histopathologic change consisted of a fungal infiltration of the nerves in the internal auditory canal, with moderate infiltration of the sense organs of the membranous labyrinth.

Adult↗
PubMed1987

Volumetric analysis of the tympanic isthmus in human temporal bones.

A volumetric study on the tympanic isthmus and its relationship to temporal bone pneumatization was conducted in 110 serially sectioned temporal bones with and without middle ear pathology. With a microcomputer and digitizing tablet, the area of the tympanic isthmus and the degree of pneumatization in sample sections were calculated. Nonpathologic temporal bones showed a significant correlation between the volume of the tympanic isthmus and the degree of pneumatization. The narrowest area of the tympanic isthmus and the degree of pneumatization were also highly correlated. The result indicated a definite inhibition of pneumatization due to chronic middle ear infection when compared with nonpathologic temporal bones.

Aged↗
PubMed1988

Concomitant changes in the acoustic impedance and the cochlear microphonic potentials during twitch contractions of the middle ear muscles in cats.

The effect of twitch contractions of the middle ear muscles in cats on sound transmission through the middle ear (as measured by the cochlear microphonic potential of the inner ear) was compared with the simultaneous changes in the acoustic input impedance of the middle ear at the same frequency. It was found that decreases in impedance were related to an increase in the amplitude of the cochlear microphonics and vice versa. This may imply that decreases in impedance measured during the initial phase of the acoustic reflex in man are true decreases and are not due to transient decoupling of the ossicular chain at any point.

Acoustic Impedance Tests↗
PubMed1984

Intra-aural reflexes elicited by a cochlear prosthesis in monkeys.

Objective audiological tests are needed for pre- and postsurgical evaluation of cochlear prosthesis patients who are unable to give reliable subjective responses. In this study we demonstrated that contralateral intra-aural reflexes were elicited by a cochlear prosthesis in the monkey. Reflex variables measured include threshold, latency and amplitude. These findings indicate that the electrically elicited intra-aural reflex response may be useful to evaluate the peripheral auditory system in subjects with sensory deafness.

Acoustic Stimulation↗
PubMed2005

Topographical anatomy of the guinea pig temporal bone.

Systematic anatomical description of the various structures of the temporal bone have been performed based on dissection of 16 guinea pigs (32 temporal bones). It has been found that besides two main air spaces in the middle ear, the tympanic bulla and dorsal bulla described in literature, there are also additional air cells in the mastoid process and facial nerve region in the temporal bone of a guinea pig. Moreover recesses were found in the walls of the tympanic bulla that formed almost completely separated partitions of tympanic cavity. The malleus head, the body of the incus and the superior and lateral semicircular canals as well as the facial nerve are easily accessible from the dorsal bulla. From the ventral tympanic bulla, one can access both windows and the cochlea. The semicircular canals are relatively large, the lateral canal is largest and the posterior the smallest. The cochlea has thin bony wall, and is composed of 3.5-3.75 turns.

Animals↗
PubMed2005

Human efferent adaptation of DPOAEs in the L1,L2 space.

The adaptive properties of distortion product otoacoustic emissions (DPOAEs) at 2f(1)-f2 were investigated in 12 ears of normally hearing adults aged 18-30 years using long-lasting 1-s primary-tone on-times. In this manner, DPOAE adaptation at a single f2 of 1.55 kHz (f2/f1=1.21) was evaluated as a function of the levels of the primary tones in a matrix of L1, L2 settings, which varied from 45 to 80 dB SPL, in 5-dB steps. DPOAEs were elicited under both monaural and binaural stimulus-presentation conditions. Adaptation was defined as the difference in DPOAE levels between the initial 92-ms baseline measure using a standard protocol and one obtained during the final 92 ms of the prolonged 1-s primary-tones. These differences were averaged across subjects to create contour plots of mean adaptation in the L1,L2 space. The 2f(1)-f2 DPOAE revealed consistent regions of suppression (-0.5 dB difference) or enhancement (+0.5 dB difference) with respect to baseline measures within the L(1),L(2) matrix for both acoustic-stimulation conditions. Specifically, 2f(1)-f2 DPOAE suppressions of 1-2 dB occurred for both monaural and binaural presentations, typically at level combinations in which L1>L2. In contrast, larger 2f(1)-f2 DPOAE enhancements of 3-4 dB occurred for only the binaural condition, at primary-tone level combinations where L1<L2. Although adaptation activity was also evaluated for the DPOAEs at f(2)-f1, 2f(2)-f1, and 3f(1)-2f2, these emissions were either immeasurable (e.g., f(2)-f1) or only present in a subset of subjects over a narrow range of primary-tone frequencies and levels that did not support a systematic analysis. In summary, the 2f(1)-f2 results suggest that a potentially important area for adaptation measures exists in the L1,L2 space, when L1 is lower than L2. This combination of primary-tone levels can lead to large DPOAE adaptation effects that may be related to a notch in the DPOAE response/growth or input/output (I/O) function.

Acoustic Stimulation↗
PubMed2002

["Irritative" pathology of the external auditory canal and decreased sound sensation].

We have not found in the literature an explanation for the intermittent and transient decreased lesser hearing sensation in patients with dysesthesia of the external auditory canal (EAC). In this paper we offer a possible explanation for it. Our hypothesis is that the stimulation of the sensory fibers of the trigeminal and facial nerves in the EAC is able to increase the stiffness of the ossicular chain by means of a reflex stimulation of malleus and stapes muscles. This intermittent and transient increase of the ossicular stiffness could explain the intermittent and transient decrease of hearing sensation in these patients.

Ear Canal↗