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PubMed1983

Evaluation of tensor tympani muscle dominance in the biphasic acoustic reflex.

The Acoustic reflex frequently causes a biphasic change in impedance at onset. Understanding the cause of the biphasic response is important for establishing a physiological basis for the clinical measurement of reflex latency. The decrease in impedance at onset may be due to uncoupling of impedance contributed by the cochlea. Subsequent increases in impedance predominantly reflect stapedius muscle activity. The clinical implications of this physiologic model are discussed.

Acoustic Impedance Tests↗
PubMed1978

Extratympanic manometry in man. Clinical and experimental investigations of the acoustic stapedius and tensor tympani contractions in normal subjects and in patients.

New ideas and inspirations for future human investigations have emerged from the experience obtained in this study. These investigations ought to be performed for both scientific and clinical reasons. It is the author's opinion that the ETM method is extremely useful and valuable. The author intends to continue the human investigations if proper conditions are available. The ETM equipment can also be further improved for scientific and special clinical investigations. For normal clinical practice a more "simplified" ETM equipment should be developed. Clinical investigations concerning the diagnosis of brain stem disorders and the selection of noise susceptible persons will be two of the primary clinical tasks.

Acoustic Impedance Tests↗
PubMed1992

[Otologic manifestations of the pain dysfunction syndrome of the stomatognathic system].

Phylogenesis, ontogenesis and anatomy explain the close relationship between temporo-mandibular joint and the middle ear and can therefore help understanding otologic symptoms such as: otalgia which often correspond to articular and muscular pain irradiation (coming from sterno-cleido-mastoid, lateral and medial pterygoid, deep layer of the masseter and temporal muscles); acouphens and ear block sensation that could be caused by a spasm extension of the manducatory (i.e. medial pterygoid) to levator and tympani tensors. These three muscles, which originate from the first branchial arch, have a proprioceptive sensitivity and share the same innervation. What is more tensor and levator veli exchange certain muscular fibers. Tensor tympani spasm can be held responsible both for a decrease or abolition of the Klockhoff's reflex, together with a decrease of the stapedian reflex, the latter due to tympani rigidity induced by a spasm of the tensor tympani.

Ear Diseases↗
PubMed1998

An anatomic study of the tensor veli palatini and dilatator tubae muscles in relation to eustachian tube and velar function.

In a gross anatomic study of 20 sides in 16 human head specimens, the tensor veli palatini, the dilatator tubae, and the tensor tympani muscles were studied. The tensor veli palatini was observed to insert onto the anterior one-third of the pterygoid hamulus, whereas the dilatator tubae rounded the middle one-third of the pterygoid hamulus without an insertion. Thus, the dilatator tubae, not the tensor veli palatini, could serve to tense the anterior velum. An insertion from the superior pharyngeal constrictor muscle onto the posterior one-third of the hamulus could provide a curbing function for the dilatator tubae muscle. Adipose tissue, located at the hamulus, could provide lubrication for the tendinous fibers of the dilatator tubae as they round the hamulus. The dilatator tubae was observed to attach to the hook of the eustachian tube and is accepted as the tubal dilator. Observed on 13 of 20 sides in 11 specimens, the bulk of the dilatator tubae remained distinct from the tensor veli palatini despite a connective tissue alliance and intermingling of some muscle fibers. On 5 of 20 sides in 5 specimens, fibers of the dilatator tubae intermingled extensively with the tensor veli palatini. Of the 20 dilatator tubae muscles dissected, 2 were observed to be deficient. The tensor veli palatini was observed to be continuous with the tensor tympani. Full color versions of the figures are available at the following website: http://www.shc.uiowa.edu/papers/tensor/.

Eustachian Tube↗
PubMed1998

Projections from the caudal spinal trigeminal nucleus to commissural interneurons in the supratrigeminal region: an electron microscope study in the rat.

Electron microscopic double-labeling study in the rat indicated that projection fibers from the caudal spinal trigeminal nucleus (Vc) were distributed ipsilaterally within the supratrigeminal region (STR) capping the trigeminal motor nucleus (Tm) and made synaptic contact with neurons projecting to the contralateral Tm. Nociceptive inputs to the Vc may reflexly control, via interneurons in the STR, the activities of Tm neurons innervating the masticatory, tensor tympani, and/or tensor veli palatine muscles.

Animals↗
PubMed1983

Objective tubal tinnitus: a report of two cases.

Two patients with objective tinnitus due to continuous tubal opening are presented. The objective tubal tinnitus was found to be due to clonic spasm of the muscles of the pharynx and eustachian tube and it can be easily differentiated by means of sonotubometry alone. The acoustic events occurring during the clicking sound were analyzed and were similar to the swallowing sound. Movements of the tympanic membrane were not seen in any of these ears. However, the close relationship of the tensor tympani and tensor palati muscles could explain the movement of the tympanic membrane in some cases. I believe that stapedius muscle spasm or a patulous tube as such does not cause the clicking sound, but it can occur in association with palatal myoclonus. The objective tubal tinnitus is heard as a result of the walls of the eustachian tube snapping together. Transection of the tensor veli palatini muscle tendon may be a useful method of treatment if the patient experiences objective tinnitus which is very distressing.

Adult↗
PubMedDate not supplied

Eardrum displacement following stapedius muscle contraction.

Simultaneous monitoring in human subjects on the same ear of eardrum displacement by tympanomanometry, and impedance with the electroacoustic bridge, provided information concerning contraction of the stapedius muscle and its effect on eardrum displacement. Extensive control procedures were employed to elicit only the stapedius reflex; lower intensity auditory stimulation, electrocutaneous stimulation of the homolateral external ear canal, and anesthetization of nerves leading to the tensor tympani. Following these procedures the following results were obtained: (1) Extremely small biphasic and monophasic eardrum movements were seen in the stapedius--only ear to auditory and electrocutaneous stimulation; the form of the response was much less predictable to auditory stimulation. (2) At high sound intensities relatively large inward and biphasic movements of the eardrum occurred in the normal ear, unquestionably due to contraction of the tensor tympani. These results were further validated in a group of stapedectomized ears, without the stapedius but with normal tensor tympani. (3) Biphasic responses did not occur in the tensor tympani--only ear, only monophasic inward responses. (4) Upon air-jet stimulation to the orbit of the eye, these subjects had an accentuated tensor response in that large inward movements of the eardrum occurred as compared with those in normal ears, suggesting that there is an alteration of the tensor response by the presence of the stapedius muscle. Estimates of the actual eardrum displacement were calculated based on a model of the external ear canal and eardrum.

Acoustic Stimulation↗
PubMed1988

The motor innervation of the tympanic muscles in the guinea pig.

The number and the location of the motor neurons innervating the stapedius or tensor tympani muscles in the guinea pig were identified by retrograde axonal transport of the tracer horseradish peroxidase. Tracer injections were made either into the stapedius or tensor tympani muscle and effected the retrograde labeling of neurons in the ipsilateral brain stem. These findings showed that the stapedius motor neurons lie outside the traditionally recognized facial nucleus and are present in two cell columns: ventromedial and dorsomedial to the facial nucleus. These labeled neurons are dissimilar to cells within the facial nucleus, i.e. they are smaller and more fusiform in shape. The tensor tympani motor neurons were found outside the trigeminal motor nucleus. At a rostral level they were located in a region ventral and ventrolateral to the latter nucleus. These labeled neurons were smaller than the trigeminal motor neurons and polygonal in shape. In the animals studied there were about six times more tensor tympani motor neurons than stapedius motor neurons.

Animals↗
PubMed1983

The fibre-type composition of the first branchial arch muscles in Carnivora and Primates.

A combination of standard histochemical techniques and immunohistochemical staining using myosin type-specific antisera was used to determine the fibre-type composition of the muscles of first branchial arch origin (that is, masseter, temporalis, pterygoideus medialis and lateralis, tensor veli palatini, tensor tympani, anterior digastricus and mylohyoideus) in a wide range of the Carnivora and the Primates. The rare IIM fibre type was found in the first branchial arch muscles of most of the species examined, but never in the limb muscles used as controls for this study. The jaw-closer muscles (masseter, temporalis and pterygoideus medialis) were found to contain IIM fibres in all the Carnivora except the lesser panda and in all the Primates except man. When present, the IIM fibres were usually the predominant fibre type, and the only other fibre types present were types I, II or IIC. The presence of IIM fibres in the jaw-closer muscles of most of the Carnivora and the Primates seems to be associated with an aggressive bite which is required for predation by the former and defence by the latter. In both groups of species there was the member which does not have an aggressive bite, the lesser panda and man, respectively, and these (like all other orders of mammals such as Lagomorpha, Rodentia, etc.) were found to have no IIM fibres in the jaw-closer muscles. The two muscles of the first branchial arch group which are derived from the ventral constrictor muscles of the (phylogenetically) original mandibular arch never contained IIM fibres, and were composed of type I and II fibres similar to those found in the control muscles of the limb. Tensor veli palatini and tensor tympani showed species-dependent variations in fibre-type composition and did not always reflect the composition of the jaw-closer muscles. Thus their common origin with the jaw-closers cannot be responsible for the occurrence of IIM fibres in tensor veli palatini and tensor tympani in some species. Furthermore, in tensor tympani but not in tensor veli palatini, the presence of IIM fibres was always accompanied by immunohistochemically slow-tonic fibres. Finally, the regard to the association of oxidative activity with the fibre type as defined by the myofibrillar ATPase method and by the isoform of myosin present, we suggest that in the first branchial arch muscles this is probably not directly comparable to the situation in the typical limb muscle.

Animals↗
PubMed2004

Responses of primary vestibular neurons to galvanic vestibular stimulation (GVS) in the anaesthetised guinea pig.

Previous studies in humans and animals which have shown that DC galvanic vestibular stimulation (GVS) induces horizontal and torsional eye movements have been interpreted as being due to a preferential activation of primary vestibular afferents innervating the horizontal semicircular canals and otoliths by GVS. The present study sought to determine in guinea pigs whether GVS does indeed selectively activate primary horizontal canal and otolith afferents. Constant-current GVS was passed between electrodes implanted in the tensor-tympani muscle of each middle ear or between electrodes on the skin over the mastoid. During this stimulation, responses from single primary vestibular neurons were recorded extracellularly by glass microelectrodes in Scarpa's ganglion. Afferents from all vestibular sensory regions were activated by both surface and tensor-tympani galvanic stimulation. Tensor tympani GVS was approximately 10 times more effective than surface GVS. At larger current intensities irregularly discharging afferents showed an asymmetrical response: cathodal stimulation resulted in a larger change in firing (increase) than anodal stimulation (decrease), whereas regularly discharging afferents responded symmetrically to the two polarities of GVS. Across all afferents tuned for different types of natural vestibular stimulation, neuronal sensitivity for GVS was found to increase with discharge variability (as indexed by CV*). Anterior canal afferents showed a slightly higher sensitivity than afferents from other vestibular sensory regions. Hence, the present study concluded that GVS activates primary vestibular afferents innervating all sensory regions in a uniform fashion. Therefore, the specific pattern of GVS-induced eye movements reported in previous studies are not due to differential sensitivity between different vestibular sensory regions, but are likely to reflect an involvement of central processing.

Action Potentials↗
PubMed2004

Myosin heavy chain composition of rat middle ear muscles.

OBJECTIVE: To quantitatively analyze myosin heavy chain (MHC) mRNA composition in two rat middle ear muscles (the tensor tympani and stapedius) using competitive polymerase chain reaction (PCR). MATERIAL AND METHODS: An exogenous template, including oligonucleotide sequences specific for the seven rat MHCs (2A, 2B, 2X, 2L/EOM, embryonic, neonatal and beta-cardiac) as well as beta-actin, was constructed and used as the competitor. RESULTS: The tensor tympani and stapedius contained all MHC isoforms except 2L. The tensor tympani contained approximately equal proportions of 2X (40.4% +/- 6.5%) and 2A (34.0% +/- 1.3%) MHCs, with a smaller percentage of 2B (16.6% +/- 1.5%) and neonatal (7.5% +/- 0.6%) MHCs, while beta-cardiac and embryonic MHCs were minimally expressed. The stapedius contained predominantly 2X (58.0% +/- 4.2%) and 2A (32.3% +/- 6.7%) MHCs, with a smaller percentage of 2B (7.4% +/- 0.2%) and beta-cardiac (1.9% +/- 0.1%) MHCs. Neonatal and embryonic MHCs were detected at very low levels. CONCLUSION: These results suggest that two middle ear muscles, which are mainly composed of two fast-twitching myosins (2X and 2A MHCs), contract fast and are fatigue-resistant.

Actins↗