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PubMed1986

The tensor tympani muscle reflex in the mouse.

Click evoked electromyographic (EMG) recordings were made from the contralateral tensor tympani muscle of anaesthetised mice. The mean threshold of the EMG response was around 50 dB SPL (peak equivalent) with a mean latency close to 4 ms. The mean amplitude of the response increased over a range of 70 dB to reach a level of around 150 microV with a mean latency around 3.5 ms. The tensor tympani muscle activity was investigated also in profoundly hearing-impaired mutant mice with either cochlear dysfunction (deafness) or brainstem dysfunction (quivering). No evoked EMG activity was detected in either group of hearing-impaired mutants. The data suggest that EMG activity in the mouse can provide a sensitive monitor of auditory function. The study of reflex activity in further mouse mutants is likely to provide information on the vulnerability of the reflex to different types of naturally occurring cochlear and brainstem pathology.

Animals↗
PubMed1990

Histopathology of the tensor tympani muscle in otitis media.

Involvement of the tensor tympani muscle (TTM) and tendon in otitis media have been suggested both clinically and experimentally. Extensive postmortem histopathological studies of the human TTM in cases with known otitis media have not been done. One-hundred-five human temporal bones with and without otitis media were evaluated using light microscopy to determine the pathological changes of the TTM and tendon. Fatty cell infiltration and degenerative changes of the muscle fibers were observed in non-otitis and otitis media groups, but were greater in those cases with otitis media. Inflammatory cell infiltration and fibroblastic reactions occurred more often in chronic and purulent otitis media, and hypercontracted fibers were more frequent in serous and chronic otitis media. This study indicates that the human TTM and tendon are pathologically involved in the inflammatory process of otitis media.

Adolescent↗
PubMed1982

The tensor tympani muscle of cat and dog contains IIM and slow-tonic fibres: an unusual combination of fibre types.

Using recently developed highly specific antisera to the full range of known adult mammalian skeletal muscle myosins, an immunohistochemical and histochemical examination was made of the middle ear muscle tensor tympani in the dog and cat. Approximately half the fibres were of the IIM type and there was a substantial population of apparently slow-tonic fibres, both these types being rare in mammals. In addition, some type I but no IIA nor IIB fibres were detected. Moreover, as no multiple end-plate innervation, thought to be typical of slow-tonic fibres, could be demonstrated in this muscle by acetylcholinesterase staining or by Ruffini gold impregnation, it is suggested that in tensor tympani the slow-tonic fibres are focally innervated. The very short length of the fibres, only 1-2 mm, is probably sufficient to permit adequate depolarization of a whole fibre by a single centrally situated end-plate. The functional implications of this combination of very rare fibre types in tensor tympani are unclear at present.

Animals↗
PubMed1999

Observations on the number, distribution and morphological peculiarities of muscle spindles in the tensor tympani and stapedius muscle of man.

Although the middle ear muscles have been described for the first time more than four hundred years ago their role in modulation and transmission of sound is not yet fully understood. Surprisingly very little is known about proprioceptors in these muscles, especially in man, although this seems to be the key to the understanding of their various functions. Therefore, the question for proprioceptive sensory organs in these muscles is still relevant. The tensor tympani and stapedius muscles of four women who had donated their bodies to our institute were taken. Complete serial sections of these muscles were made which were either impregnated with silver, stained with ferric oxide for acidic polysaccharides or incubated with antibodies against S-100 protein. Thereby four to eight (mean five) muscle spindles distributed along the whole muscle could be detected in the tensor tympani muscles. These spindles contain one to three intrafusal muscle fibres and their length ranges from 140 to 4270 microm (mean 1492.8 microm). Furthermore, in three stapedius muscles one to two (mean 1.7) muscle spindles were found. They were from 350 to 500 microm (mean 482 microm) long and contained only one intrafusal muscle fiber. Regarding the diameter of intrafusal muscle fibers in both, the tensor tympani as well as the stapedius muscle, no difference to extrafusal muscle fibers of these muscles could be detected. The structure of these spindles differs considerably from those found in skeletal muscles. The morphological findings presented strongly suggest that muscle spindles occur regularly in both middle ear muscles. The results presented herein are consistent with clinical findings obtained from electromyographic studies and may help to elucidate all functions the middle ear muscles might serve in man.

Aged↗
PubMedDate not supplied

Electromyogram of the tensor tympani muscle in man during swallowing.

Experiments were carried out on 2 patients who underwent an operation for chronic otitis media, whereupon the tensor tympani muscle was visualized. A unipolar platinum electrode was inserted into the muscle belly. EMG recordings were made during swallowing and other motor activity. Distinct, pronounced EMG activity was recorded from both patients every time they swallowed. It was concluded that the tensor tympani muscle participates in the act of swallowing and thereby probably contributes to the ventilation of the middle ear.

Deglutition↗
PubMed1986

Effects of tenotomy of the tensor tympani muscle on the acoustic reflex in dogs.

The acoustic reflex (AR) was recorded from 12 healthy mixed-breed dogs. Latency and amplitude were measured from ipsilateral and contralateral AR at stimulus frequencies of 1 and 2 kHz and intensities of 70 to 110 dB sound pressure level for ipsilateral AR and 70 to 120 dB hearing level for contralateral AR. Mean latencies for ipsilateral and contralateral AR were between 33.46 and 206.10 ms and between 45.26 and 180.89 ms, respectively, and amplitudes were between 0.14 and 1.79 cm3 and between 0.31 and 1.86 cm3 of air, respectively. Stimulus frequencies and intensities had significant effects (P less than 0.05) on ipsilateral and contralateral AR latencies and amplitudes. Ipsilateral and contralateral AR decays were determined by measuring compliance change during a 10-s pure-tone stimulation at frequencies of 1 and 2 kHz at an intensity of 10 dB above AR threshold. Reflex decays for 1 kHz and 2 kHz frequencies averaged 5.74% and 9.71%, respectively, for ipsilateral AR and 5.08% and 5.40%, respectively, for contralateral AR. Bilateral tympanograms and brain stem auditory-evoked responses were performed on each dog. Mean normal static compliance of the middle ear, as determined by tympanometry, was 0.15 cm3. Unilateral tenotomy of the tensor tympani muscle was done on 6 of the 12 dogs, and each of the preceding procedures were repeated within 1 week after surgical operation. Transection of the tensor tympani tendon did not alter (P greater than 0.05) the latencies or amplitudes of 1 kHz- or 2 kHz-evoked contralateral AR, the latency or amplitude of 1 kHz-evoked ipsilateral AR, or the amplitude of 2 kHz-evoked ipsilateral AR. However, the latency of 2 kHz-evoked ipsilateral AR was significantly (P less than 0.05) increased. Reflex decay increased significantly (P less than or equal to 0.001) for the contralateral reflex elicited by the 2 kHz stimulus. Neither compliance of the middle ear system nor amplitude and latency of the brain stem auditory-evoked response were affected (P greater than 0.05) by tenotomy. Since tenotomy eliminates participation of the tensor tympani in the AR, these data indicate that contraction of this muscle is not primarily responsible for the compliance changes recorded during an acoustic reflex in dogs.

Animals↗
PubMed1988

Muscle fiber types in the cat middle ear muscles. II. Tensor tympani.

Using quantitative histochemical techniques, it was determined that the tensor tympani muscle of the cat consists of three muscle fiber types: type 1, type 2A (staining characteristics similar to the type 1 and type 2A muscle fibers found in the control tibialis anterior muscles), and a third unclassified fiber type (type 3) similar to the 2A fiber type except that it had extremely dense alkaline actomyosin adenosine triphosphatase staining (mean transmittance, type 2A = 33.6%; type 3 = 17.3%), as well as dense staining for periodic acid-Schiff, menadione-linked alpha-glycerolphosphate dehydrogenase, nicotinamide-adenine dinucleotide tetrazolium reductase, and succinic dehydrogenase. The type 1 fiber population was smaller in diameter (mean +/- SD, 14 +/- 4 microns) than the type 2A fiber (mean +/- SD, 21 +/- 5 microns) and the type 3 fiber (mean +/- SD, 22 +/- 6 microns) populations. In all muscles, intrafascicular and extrafascicular fat accumulations were found, with the majority being extrafascicular. Calculations indicate that the tendon occupies approximately 41% of the total muscle volume, while the muscle fibers constitute 59% of the volume.

Adenosine Triphosphatases↗
PubMed1989

Detailed morphology of the tensor tympani muscle of the rat. An integrated light microscopical, morphometrical, histochemical, immunohistochemical and electron microscopical study in relation to function.

The gross anatomy, microscopical anatomy, morphometry, enzyme histochemistry, immunohistochemistry and electron microscopy of the tensor tympani muscle of the rat was studied. The aim of the study was to create an integrated insight into the morphology of the muscle and to discuss functional implications. The tensor tympani muscle of the rat is an atypical muscle. It is a small muscle composed of very small muscle fibres with a complex microscopical and submicroscopical architecture. Histochemically the muscle consists mainly of fast oxidative glycolytic fibres, but discrepancies are found when anti-heavy chain myosin antibodies are used for fibre typing. Different adult heavy chain myosin isotypes coexist in one single muscle fibre. The electron microscopical study shows that bundles of myofilaments branch and interconnect with other bundles of myofilaments. The findings suggest that the muscle is able to contract fast and is fatigue-resistant. Both features seem to suggest that the muscle has a function in protecting the inner ear against noise damage.

Adenosine Triphosphatases↗
PubMedDate not supplied

Reflexogenic vertigo treated by tensor tympani transection.

Two patients complained of severe vertigo following eructation or hiccup. One patient was poststapedectomy; the other had idiopathic cochlear degeneration. The symptoms were reproduced by Hennebert's test in the pathologic ear. The tensor tympani was transected in both patients. An endolymphatic sac procedure was performed concomitantly in the second patient. Both patients had immediate relief of symptoms. It is hypothesized that these reflex phenomena, which elicited vertigo, were accompanied by tensor tympani contraction, which resulted in medial movement of the stapes or prosthesis, and that this movement was transmitted via adhesions to vestibular endorgans to produce the described symptoms.

Adult↗
PubMed2005

Tonic contractions of the tensor tympani muscle: a key to some non-specific middle ear symptoms? Hypothesis and data from temporal bone experiments.

CONCLUSIONS: The results of this study show that in clinical practice it will not be easy to diagnose tonic contractions of the tensor tympani muscle and only a combination of findings will be helpful. Based on these experimental results a clinical study will be started which should clarify the diagnostic relevance of indicators of tonic tensor muscle contractions. OBJECTIVES: There are indications from the literature and from personal experience that tonic contractions of the tensor tympani muscle may play a role in some ear symptoms, such as fullness, certain cases of tinnitus, slight hearing loss or Ménière's disease-like findings. In order to prove this theory we looked for indicators, either visual or functional, to help clinically diagnose the functional state of the muscle, particularly its tonic contraction. MATERIAL AND METHODS: Experiments simulating tensor contractions were carried out on temporal bone specimens. Traction was applied either to the isolated muscle, to its tendon or to the malleus neck. Effects were observed either visually via an endoscope or by impedance audiometry using multiple-frequency tympanometry. RESULTS: During simulated tensor traction the aspect of the tympanic membrane changed slightly, i.e. there was some inward movement of the umbo. However, such effects were only identifiable during the pulling action or by directly comparing the "contracted" and "relaxed" states. Tympanometry revealed a decrease in the peak amplitudes and a shift in the middle ear resonance towards higher frequencies during contractions.

Acoustic Impedance Tests↗
PubMed1986

A morphological evidence of direct connections from the cochlear nuclei to tensor tympani motoneurons in the cat: a possible afferent limb of the acoustic middle ear reflex pathways.

The central circuitry of the acoustic middle ear reflex activating the tensor tympani muscle was studied in the cat by tracer methods using horseradish peroxidase (HRP), wheat germ agglutinin (WGA) or HRP conjugated with WGA (WGA-HRP). The results indicate that the dorsal and ventral cochlear nuclei send fibers to motoneurons innervating the tensor tympani muscle, bilaterally with an ipsilateral dominance.

Afferent Pathways↗
PubMed2005

Reconstruction of the tensor tympani tendon.

We describe a case in which reconstruction of the tendon of the tensor tympani muscle was necessary for the successful restoration of sound conduction. The right ear of a nine-year-old boy was treated for cholesteatoma with staged surgery. During the first operation, the tendon was cut to ensure good visibility in the tympanic cavity. Post-operatively, maintenance of aeration of the middle ear required ventilation tubes at first and Valsalva manoeuvres later on. The position of the reconstructed tympanic membrane varied a great deal, moving between the medial wall of the tympanic cavity and extreme bulging. This made exact measurement of a columella for ossicular reconstruction impossible. The preserved handle of the malleus was bound to the cochleariform process with ionomer cement, using a piece of surgical suture material as a substitute for the tendon. This arrangement prevented the tympanic membrane from undergoing excessive lateral movement after inflation and the ossicular chain was replaced with a successful ossiculoplasty with an autogenous bone 'drum to footplate' columella. The pre-operative 55.0 dB air-bone gap decreased immediately to 3.3 dB, widening after three years to 15.0 dB.

Child↗
PubMedDate not supplied

Bipolar electric stimulation to elicit and isolated tensor tympani reflex.

A bipolar electrode is described, designed to obtain improved reflex responses from the tensor tympani muscle by electric stimulation of the under surface of the tongue, d.c. generator, 7-9 V d.c. In comparison with the previous unipolar method of stimulation the responses under oscilloscopic analysis appear very constant and of greater size. The latency, in normal subjects, is 117 msec.

Electric Stimulation↗
PubMedDate not supplied

Value of the isolated tensor tympani muscle reflex elicited by electric lingual stimulation.

A bilateral reflex contraction of the isolated tensor tympani muscle has been obtained in man by bipolar electric stimulation of the edge of the tongue (DC generator). The avoidance of the elevated and variable body electric resistance and of the variable contact resistance from the hand to the ground plate, represents an appreciable improvement of this method in comparison with the unipolar method described in a earlier paper. A further improvement has also been achieved by applying the electric stimulus to one inferior aspect of the tongue near the floor of the mouth, nearer to the lingual nerve. An analysis has been subsequently conducted in normal subjects and in patients affected by pathologies of the tympano-ossicular system; otosclerosis, tympanosclerosis, unilateral complete suprastapedial facial paralysis, interrumption of the ossicular chain; in cases of interruption of the afferent arc: section of the unilateral lingual nerve; involvement of its central portion: cerebello-pontine angle tumour, brain stem tumour. A chiasma-like central nervous pattern is suggested.

Brain Neoplasms↗
PubMedDate not supplied

Electrophysiological and HRP studies of the direct afferent inputs from the cochlear nuclei to the tensor tympani muscle motoneurons in the cat.

The direct fiber connections from the cochlear nuclei to the tensor tympani muscle (TTM) motoneurons were investigated by means of electrophysiological and horseradish peroxidase (HRP) methods, using cats. When HRP was injected into motoneuron region of the TTM, HRP-labelled cells were found bilaterally in the dorsal cochlear nucleus (DCN) and ventral cochlear nucleus (VCN). When the electrical stimulus was applied to the cochlear nucleus, the TTM motoneurons fired spikes monosynaptically with s short latency. These histological and electrophysiological results indicate the existence of direct fiber connections from the bilateral cochlear nuclei to the TTM motoneurons.

Animals↗
PubMed1982

Localization of the motor neurons to the tensor tympani muscle.

The localization of the motor neurons to the tensor tympani (TT) muscle was studied using the method of retrograde transport of horseradish peroxidase (HRP). After intramuscular injections of HRP, specifically labeled neurons were found in the ventral, parvocellular portion of the trigeminal motor nucleus. These cells had a medial relation to the rootlets of the trigeminal nerve and, rostrally, to the lateral lemniscus. The results are compared to those of other investigators and a generalization is suggested for the localization of these neurons which allows for species variation. Other incidental findings are also discussed.

Animals↗
PubMed1993

Cholera toxin B-HRP and wheat germ agglutinin-HRP tracing of tensor tympani muscle motoneurons and processes in rabbits.

The brain stem position, organization and number of motoneurons innervating the rabbit tensor tympani muscle (TTM) were determined by retrograde axonal transport of cholera toxin B/horseradish peroxidase conjugate (CTB-HRP) and wheat germ agglutinin HRP conjugate (WGA-HRP) tracers. The synaptic input to the TTM motoneurons was examined with WGA-HRP. The results show the motoneurons of the TTM to be localized in a cluster ventro-lateral to the outer margin of the ipsilateral trigeminal motor nucleus (VMN) and dorso-lateral to the superior olive. The number of labeled cells was greater in the combined CTB-HRP/WGA-HRP injected cases. The TTM motoneurons were triangular and elongated in shape and smaller than those of the VMN. An extensive network of dendritic branches was present ventro-laterally in the vicinity of the superior olive. Similar, but less extensive collections of dendritic processes were observed to course dorso-medially, rostrally and caudally. Axons were observed to project first dorsally or laterally, towards the trigeminal motor root, then after a sharp turn coursed ventrally within the trigeminal motor root (VMR). Transneuronal transport of the WGA-HRP was not accomplished in any preparation, suggesting among other things, system or species differences in the effectiveness of the WGA-HRP conjugate as a transynaptic tracer. It is concluded that the TTM acoustic reflex in rabbits and other mammals, its threshold, prolonged contraction capacity, and its influence on middle ear sound transmission may be related to its demonstrated extensive synaptic field in the reflex chain, particularly in the area of the superior olive, while its many other physiological functions may be made possible by the number, location, and multi-dimensional orientation of its motoneurons and dendrites.

Animals↗
PubMed1986

Tensor tympani reflex pathways studied with retrograde horseradish peroxidase and transneuronal viral tracing techniques.

The neural pathway involved in activation of the tensor tympani (TT) muscle was studied in the rat using retrograde HRP and transneuronal viral tracing techniques. The pool of TT motoneurons labeled with HRP was located ipsilaterally under the anterior third of the trigeminal motor nucleus and extended rostrally towards the lateral lemniscus. The origin of the inputs to these motoneurons was then determined using transneuronal viral transport: presumably transneuronally infected neurons appeared bilaterally in the vicinity of the superior olivary complex, mainly in between the two nuclei of the trapezoid body. The present data are consistent with previous conclusions based on lesion experiments that the TT reflex loop is made up of a chain of 4 neurons.

Animals↗