Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Stapedius”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 55 records · Page 3Linked to original sources
PubMed1979

The effect of the stapedius reflex on attenuation and poststimulatory auditory fatigue at different frequencies.

The effect of the stapedius reflex on attenuation was measured in patients with unilateral facial palsy (Bell's palsy) and stapedius muscle paralysis. Poststimulatory auditory fatigue was determined in the same patients and in a group of normal test subjects with a normal bilateral stapedius muscle function. The attenuation for a 0.5 kHz tone was found to begin at the reflex threshold, to increase about 7 dB per a 10 dB increase in the stimulus tone and to reach a maximum in the vicinity of 20 dB. When a 2.0 kHz tone was used, no attenuation of note appeared until the sound had risen to about 10 dB above reflex threshold. The attenuation reached a maximum at a little less than 10 dB. A properly functioning stapedius muscle significantly reduced poststimulatory auditory fatigue at 0.75 kHz while at 3.0 kHz, it could do so only if it was stimulated into action by low-frequency noise.

Acoustic Impedance Tests↗
PubMed1979

Physiological activation of the stapedius muscle in Gallus gallus.

The function of the avian middle ear muscle was investigated in the chicken, Gallus gallus (domesticus). The avian species offers excellent conditions for study of middle ear muscle function since it possesses a single middle ear muscle, the stapedius, which is located extracranially. Electromyograms (EMG), measurements of impedance change, and volume change in the middle ear cavity were used to assess the muscle's activity. The results showed that the middle ear muscle of Gallus does not exhibit an acoustic reflex. However, the stapedius is regularly activated during the animal's own vocalization. Measurements of the EMG and volume change showed the stapedial activity to increase systematically with increases in the vocal sound level. The use of volume change as a measure of stapedius function was found to be highly suitable in the present experiments in that it allows for measurements of the magnitude of the stapedius contraction without altering the intact physiological state of the middle ear, and is insensitive to the ambient noise and vocal sounds, that hamper the impedance technique.

Acoustic Impedance Tests↗
PubMed1979

Contraction properties and functional morphology of the avian stapedius muscle.

The influence of the stapedius muscle contraction on middle ear volume and acoustic impedance was investigated in the chicken, Gallus gallus. The time course of twitch responses to electrical stimulation (measured as volume and impedance changes) was found to be largely independent of the stimulus voltage, having a contraction time of 22 ms and a half-relaxation time of 22 ms. The stapedius muscle was therefore characterized as a fast twitch muscle. Slow contraction properties were also revealed: A summation of responses to repetitive stimulation beginning at 2.5 Hz and a slow decline to baseline were seen in volume and impedance change recordings. The morphological characteristics were consonant with that of a homogeneously fast muscle: Only fibres with high ATPase activity were identified and no fibres with "en grappe" or multiple innervation were observed. The slow characteristics were suggested to be due to visco-elastic elements in the middle ear. The chicken stapedius muscle is suggested to be analogous to both the stapedius and the tensor tympani of mammals.

Acoustic Impedance Tests↗
PubMed1993

Fine structure of the tendon of the human stapedius muscle: comparison of normals and clinically otosclerotic patients.

The tendon of the human stapedius muscle was studied in normal post mortem material and in clinical otosclerotic patients, using light and electron microscopy. Cross section profiles of collagen fibrils were measured in various regions of the tendon and the amount of elastin was estimated. The normal stapedius tendon consisted of three concentrically arranged portions: A cylindrical central part, a tube-like mid-portion, and a cortical layer. The central part was made up of collagen fibrils with only a few elastic fibers, the mid-portion contained collagen fibrils together with significantly more elastic material, while the cortical layer, again, showed a smaller amount of elastic fibers. Mean diameters of collagen fibrils in the central part of the tendon were 65.12 +/- 11.89 nm, in the intermediate layer 41.00 +/- 9.63 nm, and in the cortical layer 70.28 +/- 19.58 nm. Stapedius tendons from clinically otosclerotic patients, though showing the same construction, were characterized by significantly altered collagen fibrillar diameters (Mann-Whitney U-test). In the central part, mean diameters were reduced to 61.05 +/- 14.70 nm, in the mid-portion increased to 50.90 +/- 10.08 nm, and in the cortical layer reduced to 61.09 +/- 8.49 nm. The changes of collagen cross section profiles estimated for the entire tendon were significant as well: 59.68 +/- 18.74 nm in controls versus 57.82 +/- 12.53 nm in otosclerotic patients. Elastin content in the mid-portion of control stapedius tendons increased with age (13% at 35 years of age to 35% at 70 years of age).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Post-operative stapedius reflex tests with simultaneous loudness scaling in patients supplied with cochlear implants.

The estimation of the maximum comfort loudness levels (MCL) by measurements of the electrically elicited stapedius reflex was examined in six experienced cochlear implant users supplied with the COMBI 40 implant system. The stapedius reflex was tested and loudness scaling was performed simultaneously using an up/down stimulation protocol close to the reflex threshold with automated recording of both test procedures. The electrical stapedius reflex threshold (ESRT) and loudness scaling were evaluated separately. Scaling at the reflex threshold ranged between normal and loud. The range of stimulus intensities corresponding to ESRT is much smaller than that at a particular loudness category. The overall correlation between ESRT and MCL was high (r=0.92), with a similar dependence of ESRT and MCL on the channel stimulated. Thus, when the stapedius reflex can be detected post-operatively, the ESRT can be applied successfully for the fitting procedure of the speech processor. Simultaneous loudness scaling during the entire reflex test showed that overstimulation via the implant can be avoided effectively.

Adult↗
PubMed2001

Contribution to the development of the stapedius muscle structure in human fetuses.

The purpose of this report is to contribute to the knowledge of the morphogenesis of the human stapedius muscle. We have studied the stapedius structure development in 17 temporal bones from human fetuses. Chronological ages were from 48 days (21 mm) to 29 weeks (270 mm). Samples were fixed in 10% formol, decalcified with 2% nitric acid, embedded in Paraplast, sectioned in sequence of 7 microns and were stained with haematoxylin & eosin and Martins' trichrome. Four maturation stages were observed in the development of the stapedius muscle structure. First, the formation of the 'primordium muscularis' in the mesenchyme of the tympanic cavity (promyoblasts) was observed in a 36-mm embryo. Second, its differentiation into myoblasts, and its next cellular fusion to form muscle tubes, was seen in a 99-mm foetus. In the third stage, myofibrogenesis phenomena were developed, to synthesize, the myotube myoblasts, myofilaments, phenomena we observed that took place during the 14th to 17th weeks of development. The last stage was characterized by the presence of striated muscle fibres, at first intermingled with myotubes (18th to 26th weeks), until in the 29th week fetuses (270 mm) the skeletal muscle fibre was completely differentiated. We conclude that in the 29th week of development (270 mm) the stapedius muscle structure is completely differentiated, although the functional development is not complete until birth.

Embryonic and Fetal Development↗
PubMed1992

[Correlation between electrically-induced stapedius reflex and discomfort threshold in cochlear implant patients].

Electrically elicited stapedius reflex thresholds are an objective criteria for the fitting of speech processors in very young children. Reflex thresholds generally fit well within the upper third of a subject's individual dynamic range, the difference between electrical threshold of hearing, (T) and maximum comfort (C) levels and can be used to predict ultimate behavioral maximum comfort levels. In acoustically elicited stapedius reflexes a saturation of impedance amplitude can be registered at approximately 110 dB, which is 90% of the dynamic range. Assuming a similar relationship for the electrically elicited stapedius reflex there would be two values within the dynamic range which could be used for extrapolation of the threshold level. In the present study, the electrically elicited stapedius reflex was examined in 16 deaf patients who had received 22-channel Clark/NUCLEUS cochlear implants. Using an apical, a medial and a basal electrode pair, different stimulation positions within the cochlea were tested. The contralateral reflexes could be elicited in 11 patients (69%). A saturation of the reflex amplitude was recordable in 10 subjects, at least in one of the electrode pairs. The reflex saturation in all cases was located close to the uncomfortable loudness level within the subjects' dynamic ranges (at 95% dynamic). This finding is comparable to acoustic matter. As a result, these data together with reflex threshold data suggest a means for predicting to predict the threshold levels.

Acoustic Impedance Tests↗
PubMed1980

[The human stapedius reflex by ipsilateral electrical stimulation of the auditory meatal skin (author's transl)].

A modified method for eliciting a stapedius reflex by electrical stimulation of the meatal skin is presented. In contrast to the acoustically elicited stapedius reflex, the electrically-induced response is only ipsilateral, and can be ablated by anesthesia of the meatal skin. Contralateral acoustical and ipsilateral electrical stimulations lead to a summation effect of the amplitude off the stapedius reflex. When presented simultaneously, subthreshold electrical and acoustical stimulations may produce a reflectory contraction of the stapedius muscle. Similar responses can be found in diseases of the middle ear and the facial nerve. The method described is not difficult to perform, is painless to the patient, and can be used objectively in neurotologic testing.

Auditory Threshold↗
PubMed1996

Stapedius reflex measurements during surgery for cochlear implantation in children.

Electrically evoked stapedius reflex measurements were obtained in 19 children during surgery for cochlear implantation. They all received the Nucleus device. Stapedius reflexes could be elicited in all the children with congenital deafness but not in all the children with an etiology of meningitis. The intraoperative stapedius reflex thresholds were compared with postoperative values obtained after fitting of the speech processor and with the children's long-term behavioral most comfortable levels (C-levels). The intraoperative reflex thresholds were considerably higher than the postoperative reflex thresholds (44 "stimulus level steps" on the average), which could in part be ascribed to the influence of anesthetics used during surgery. It was concluded that, especially in children with an etiology of meningitis, the intraoperative stapedius reflex threshold (even after corrections for the concentration of the volatile anesthetics used) was a weak predictor of the C-level.

Adolescent↗
PubMed1978

Ultrastructural features of neuromuscular junctions in the stapedius muscle of gallus gallus.

The ultrastructure of neuromuscular junctions in the twitch fibers of the stapedius muscle of Gallus gallus (domesticus) was investigated as part of a series of neurophysiological studies. Among the morphological features observed were elongated end-plates with numerous large and clear synaptic vesicles mixed with larger dense core vesicles and irregular or aperiodic "active sites" in the presynaptic membrane where synaptic vesicles were focused. The most remarkable features of these junctions were large synaptic clefts (50-80 nm) and the absence of junctional folds in the sarcolemmal surface. Unlike the large periodic junctional folds seen in the neuromuscular junctions of frogs and in the fast twitch fibers of the mammalian stapedius, the preparations studied only show small aperiodic invaginations (primitive folds) in the postsynaptic membranes. This morphological feature remains essentially constant from newly hatched to adult chickens. While these smooth junctions are consistent with earlier findings of inconspicuous junctional folds in the twitch fibers of the chicken posterior latissimus dorsi they are unlike those seen in the fast twitch fibers of the mammalian stapedius muscle, or other twitch fibers in general. The morphological findings of the present study may also suggest that the simple, unmodified neuromuscular junctions in the stapedius of Gallus may be a useful preparation for studies of synaptic membrane structures that employ the freeze-fracture technique.

Animals↗
PubMed1989

Vocalization and stapedius muscle activity evoked by local electrical stimulation of midbrain in the chicken (Gallus gallus).

The organization of chicken mesencephalic areas from which stapedius muscle activity and vocalization can be differently elicited was studied. Our results show the existence of an area, around the mesencephalic 'calling area', from which stapedius muscle activity can be evoked independently of vocalization. Furthermore, low threshold 'vocalization loci' stimulation evokes field potentials in the stapedius-controlling area, due to the activation of stapedius-controlling neurons by vocalization neurons.

Animals↗
PubMed1978

[The value of stapedius reflex examinations in patients with myasthenia gravis (author's transl)].

The behavior of the stapedius reflex was examined by means of the Z0-70 Madsen electroacoustic bridge in 41 patients (aged 9-73) with myasthenia gravis. A higher stapedius reflex threshold (90-130 db) at normal hearing was found in 66% of the cases. In 46.3% of the cases, an increased fatigue of the stapedius muscle was observed, as characterized by the lowering of the amplitude or the disappearance of the reflex after several successively repeated recordings. The examination of stapedius muscle fatigqu may be helpful indiagnosing early forms of myasthenia, in following the results of therapy for the disease, as well as in assessing the efficiency of antimyasthenic drugs.

Acoustics↗
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↗
PubMed1990

Electrically elicited stapedius reflex in cochlear implant patients.

Electrically elicited stapedius reflexes were examined in 25 deaf patients who had received a 22-channel Clark/NUCLEUS cochlear implant. Using an apical, a medial and a basal electrode pair, different stimulation positions within the cochlea and different stimulation modes were examined. For threshold determination, 10 reflexes were averaged with reflexes recorded on the nonoperated side. Reflexes were elicited in 19 of the 25 patients (76%); a saturation of reflex amplitude could be recorded in 14 (56%) subjects. In two additional cases, a reflex could be obtained by increasing the bipolar stimulation width (changing the stimulation mode). In comparison with different stimulation positions within the cochlea, the stimulation of apical electrodes produced more distinctive reflexes and required lower current levels. An increase in the bipolar stimulation width also decreased the intensity required for stapedius reflex threshold. Our data suggest that stapedius reflex evaluation may be a useful tool for speech processor fitting.

Adult↗
PubMed1993

Detection of hearing impairment with the acoustic stapedius reflex.

The acoustic stapedius reflex (ASR) is the sound-evoked contraction of the stapedius muscle. The ASR is mediated by a neural network, receiving its afferent input from the VIIIth cranial (auditory) nerve and sending its efferent output to the VIIth cranial (facial) nerve. Several centers in the brain stem comprise the central portion of the reflex pathway. The stapedius muscle in each ear responds to ipsilateral, contralateral, and binaural stimulation. The normal ASR threshold is 90 to 95 dB SPL for tones and 70 to 75 dB SPL for wideband noise. In ears with sensorineural hearing loss, ASR thresholds are elevated more for wideband noise than for tones. These bandwidth-related changes form the basis for detection of hearing loss from ASR data. A number of methods have been proposed which differ in the nature of the outcome. Some try to quantitatively estimate hearing loss, whereas others categorize outcomes as pass or fail. In general, methods that attempt quantitative estimation of hearing loss do so at the expense of higher error rates. With adequate recording techniques, the ASR has been shown to effectively detect hearing losses exceeding 30 dB in adult subjects. Although ASR recording in newborns requires a higher probe frequency than the commonly used 226 Hz, ASR thresholds in newborns appear to be similar to those in adults. Limited information exists on the use of the ASR for detection of hearing loss in the infant population. With adequate attention to methodological requirements of testing infants, the ASR may offer a cost-effective method for the early detection of hearing loss.

Acoustic Stimulation↗
PubMed1995

Congenital ossification of the stapedius tendon: diagnosis with CT.

PURPOSE: To describe the features of congenital ossification of the stapedius tendon at thin-section computed tomography (CT). MATERIALS AND METHODS: Thin-section CT scans, clinical records, and surgical findings were retrospectively evaluated in nine ears of five patients with surgically proved congenital ossification of the stapedius tendon. Thin-section CT scans of 50 control ears were also reviewed. RESULTS: On thin-section CT scans, a linear area of soft-tissue attenuation was demonstrated between the monopod stapes and the pyramidal eminence (nine ears), as well as thickening of the stapes footplate (two ears). In the 50 control ears, the normal stapes tendon was not clearly seen on thin-section CT scans. CONCLUSION: At CT, a linear area of soft-tissue attenuation that extends from the pyramidal eminence to the monopod stapes is suggestive of congenital ossification of the stapedius tendon or a bony bar adjacent to it.

Adolescent↗
PubMed2003

Intraoperative electrically elicited stapedius reflex threshold is related to the dosage of hypnotic drugs in general anesthesia.

Today cochlear implantation is a widely used means of treatment in deafness and severe hearing disorders in adults, children, and infants. Postoperative fitting of the externally worn speech processor is very important for successful use of the cochlear implant. However, especially in infants and young children, this fitting process can be difficult because of limited communication capabilities. The use of intraoperatively obtained stapedius reflex thresholds has been proposed for postoperative speech processor fitting, but the influence of anesthetics on threshold values needs to be taken into account. In a retrospective study with 20 patients between 3 and 43 years of age, a highly significant correlation between the dosage of methohexital and the mean stapedius reflex threshold value could be shown (r = 0.65, p = .002). We conclude that more reliable threshold values can be obtained by reducing the dosage of hypnotics to achieve a lighter level of hypnosis during stapedius reflex measurement. To achieve a light, but still sufficient level of hypnosis, electroencephalographic monitoring including automatic interpretation of the complex raw signal should be used.

Adolescent↗
PubMed1980

Stapedius reflex quantification in acoustic tumor patients.

This investigation is a human application of previously reported work from our laboratories on experimental acoustic tumor effects on the stapedius reflex in monkeys. In this study, the contralateral stapedius reflex was elicited in human controls and in subjects with an acoustic tumor. Acoustic impedance was recorded on magnetic tape for offline analysis of reflex threshold, latency, rise, amplitude, decay, and relaxation. Typical tumor effects on threshold and decay were observed. Most important was the demonstration that decay measured at 20 db SL was more sensitive and more specific for tumor than decay measured at the conventional 10 db SL. Stapedius reflex latency, rise, and amplitude were more sensitive to the presence of a tumor than were measures of threshold and decay. These data indicate that qualification of the reflex will increase the utility of the test.

Acoustic Impedance Tests↗