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PubMedDate not supplied

The avian stapedius muscle. Influence on auditory sensitivity and sound transmission.

The influence of the solitary avian middle ear muscle, the m. stapedius, on auditory sensitivity and sound transmission was investigated in the domestic chicken, Gallus gallus. Electrophysiological recordings of inner ear microphonic potentials (MP) were made in order to determine the effects of calibrated, mechanically induced stapedius muscle (SM) tension changes on sounds reaching the auditory receptor cells. The maximum MP responses recorded during the pre-tension measurements were on the order of 200 microV and were linear (on a log-log scale) over a range of 40-100 dB SPL. Tension levels of 50-400 mN in the SM caused a reduction of up to 20 dB in the MP at frequencies throughout the auditory spectrum. It is concluded that the SM of Aves serves to protect the inner ear receptor cells against overstimulation. In addition to attenuating the amplitude of the MP response, SM tension changes caused significant changes in the phase of the signals reaching the inner ear. The magnitude of attenuation in the ipsilateral MP response to 200-400 mN of tension was found to be similar to the interaural attenuation that occurs when sound is transmitted to the ipsilateral ear from the contralateral ear via the intracranial passageway. The similarity in MP amplitude changes resulting from SM tension and intracranial transmission suggests that the SM may be involved in interaural interaction and thereby may aid in sound localization.

Animals↗
PubMed1981

Abnormalities of the stapedius reflex in patients with vertigo.

Analysis of the latency, amplitude, and rise characteristics of the stapedius reflex as demonstrated on a strip recorder revealed abnormalities in patients with vestibular neuronitis and other vertigo syndromes. The findings in vestibular neuronitis, acute labyrinthitis, perilymphatic fistulas, Meniere's disease, cerebrovascular insufficiency, and metabolic vertigo are described. Alterations in the stapedius reflex included increase in latency, decrease in amplitude, stepping of the rise, and absence of the reflex. This study suggests that absence of the reflex can be associated with vertigo as well as with acoustic neuromas and other retrocochlear lesions. The findings of abnormalities in vestibular neuronitis support a brain-stem localization as the site of lesion in this disease.

Cerebrovascular Disorders↗
PubMed1978

Quantitative studies on the nervus stapedius of the mouse with the electron microscope.

A nerve fiber count analysis was performed with the electron microscope on the nerve to the stapedius in seven mice. On an average, 77 (81%) of the total nerve fibers (95) were myelinated and 18 (19%) unmyelinated. The nerve consisted mostly of large myelinated fibers, minor diameters of which measured 3-4 micrometer most frequently like the large fiber zone of the motor root of the facial nerve and the facial trunk. The nerve fibers to the stapedius come from the large fiber zone of the facial nerve trunk.

Animals↗
PubMed1980

[Effects of diazepam on stapedius reflex: physiological research].

The effect of diazepam (10 mg i.m. X 7 days) on crossed and uncrossed acoustic stapedius reflex parameters (threshold, amplitude and duration) has been studied in 7 normal hearing subjects. The results showed that diazepam has a not clinically significant damping effect on the threshold, the amplitude and, very often, the duration of both ipsilateral and contralateral acoustic stapedius reflexes.

Acoustic Stimulation↗
PubMed1997

Stapedius tendon reconstruction during stapedotomy: technique and results.

During surgery for otosclerosis, it is common for the surgeon to cut the stapedius tendon. Even without reconstruction of the tendon, the results of this kind of surgery are particularly satisfactory. The stapedial reflex is more important for improving intelligibility of speech in the presence of background noise than for protection against hazardous levels of noise. An intact stapedial reflex improves ones ability to follow speech in the presence of background noise. This report will present a technique to reconstruct the stapedius tendon, along with the results obtained when adding this procedure to stapedotomy surgery.

Aged↗
PubMed1998

The influence of the concentration of volatile anesthetics on the stapedius reflex determined intraoperatively during cochlear implantation in children.

OBJECTIVE: The goal of this study was, first, to determine the effect of the concentrations of volatile anesthetics (halothane and isoflurane) on the intraoperative elicited electrical stapedius reflex threshold (ESRT) and, second, to evaluate the relation between the ESRTs and postoperative C-levels. STUDY DESIGN: This was a prospective clinical study in a single subject design. SETTING: The study was conducted at University Hospital Nijmegen, which is a tertiary care and cochlear implant center in The Netherlands. PATIENTS: The study population comprised 13 deaf children (6 males and 7 females) undergoing cochlear implantation. RESULTS: In most of the children, increasing the concentration of volatile anesthetic agent resulted in higher stapedius reflex threshold. After correction for this effect, a good relation was found between ESRT and C-level in all children, except for one. CONCLUSIONS: The outcome of this study supports the determination of intraoperative ESRTs for programming of the speech processor postsurgery.

Anesthetics, Inhalation↗
PubMed1984

Effect of ketamine on the stapedius reflex in the squirrel monkey.

We evaluated the effect of ketamine hydrochloride on the acoustically elicited stapedius reflex of squirrel monkeys. After intramuscular injection, in the presence of normal tympanometry, the amplitude of the contralateral stapedius reflex was severely depressed, even at low, preanesthetic dose levels. Possible mechanisms for the mediation of this unexpected effect are discussed.

Acoustic Impedance Tests↗
PubMed1987

A histochemical characterization of muscle fiber types in the avian M. stapedius.

The muscle fiber types and sizes in the M. stapedius (middle ear muscle) of the domestic chicken, Gallus gallus were determined histochemically on the basis of their reactions to myofibrillar adenosine triphosphatase (mATPase), succinic dehydrogenase and NADH diaphorase. Only type II fibers were identified at pH 9.4 and 4.2. At pH 4.6 three levels of activity were seen: high, intermediate and low. With the staining techniques three subtypes of fibers for oxidative enzymes, Types II1 (highly glycolytic), II12 (intermediately glycolytic and lipolytic) and II123 (highly lipolytic) were identified. Fiber diameter was also measured for the different fiber types. The average fiber diameter was around 20 micron for each fiber type. Although similar in size, the fiber types were markedly different in their histochemical properties. These findings plus those of earlier physiological studies suggest that the M. stapedius of G. gallus is a fast twitch, muscle with fibers of similar diameter showing mainly fatigue resistance characteristics.

Adenosine Triphosphatases↗
PubMed1998

Preservation of the stapedius tendon in laser stapes surgery.

OBJECTIVES/HYPOTHESIS: The stapedius tendon is routinely transected during stapes surgery. The objective of this study was to evaluate the technique of stapedial tendon preservation during stapes surgery and to compare results of these cases with cases where the stapedial tendon was not preserved. STUDY DESIGN: Retrospective study. METHODS: Four groups of patients were evaluated. Two groups had undergone stapes surgery with preservation of the stapedial tendon. One of these groups underwent a laser stapedotomy minus prosthesis (laser STAMP) procedure, while the other group had a prosthesis inserted. The other two groups had undergone laser stapedotomy with one of two different prostheses being used. Audiometric data were obtained and reviewed both preoperatively and at approximately 6 weeks postoperatively. RESULTS: All groups had overall successful results demonstrating that stapedial tendon preservation is technically possible and does not compromise outcomes. CONCLUSIONS: Based on the results, it is recommended that the stapedius tendon be preserved whenever possible during laser stapes surgery. Reasons justifying its preservation are discussed.

Adult↗
PubMed2004

Wideband reflectance measures of the ipsilateral acoustic stapedius reflex threshold.

OBJECTIVE: The purpose of this study was to develop a method for acoustically measuring the ipsilateral acoustic stapedius reflex threshold by using wideband shifts in energy reflectance and admittance. DESIGN: A group of 27 young adult subjects with normal hearing participated in the study. Contralateral reflex thresholds were first measured for a 4000 Hz activator tone (maximum level, 92 dB SPL), using a clinical method with a 226 Hz probe tone. Ipsilateral and contralateral reflex thresholds were then measured by using an experimental wideband reflectance and admittance system that used a band-filtered click (200 to 2000 Hz) as the probe stimulus, presented simultaneously with the 4000 Hz activator tone. Reflex thresholds for the wideband system were determined by using statistical tests of the magnitude of the reflex responses as well as their correlation with other reflex responses. RESULTS: Clinical and experimental reflex thresholds were obtained for 9 of the 27 subjects for all conditions. Clinical reflex thresholds were absent for 8 subjects for whom experimental reflex thresholds were present and were present for 5 subjects who had absent experimental reflex thresholds for one or more conditions. An additional 5 subjects had absent reflex thresholds in all conditions, consistent with the low maximum level of the activator. Wideband measures of contralateral reflex thresholds were approximately 3 dB lower than those obtained with the clinical system. The magnitudes of the group means of the reflex responses were similar for ipsilateral and contralateral stimulations. CONCLUSIONS: Wideband measures of reflectance and admittance may be used to estimate the ipsilateral acoustic stapedius reflex threshold by separating in frequency the spectral energies of the wideband probe stimulus from the activator stimulus. This technique holds promise for measuring reflex thresholds for individuals with absent reflex thresholds through the use of standard clinical methods.

Acoustic Impedance Tests↗
PubMed1992

Short-term poststimulatory response characteristics of the human acoustic stapedius reflex: monotic and dichotic stimulation.

Two experiments were performed to study short-term poststimulatory response characteristics of the human acoustic stapedius reflex in the time and intensity domains. In experiment 1, monotic magnitude-intensity functions (MIFs) were obtained for a 20-ms test stimulus preceded by a conditioning stimulus varying in duration (20, 50, 100, 500 ms) and level (-10, 0, +10 dB re: stapedius-reflex threshold) and temporally separated from the test stimulus by various interstimulus intervals (ISIs) (0, 20, 50, 100, 500 ms). Experiment 2 was similar in design except that conditioner and test stimuli were presented dichotically and fewer ISIs were used. Both experiments demonstrated that a prior conditioning stimulus produced significant increases in test-stimulus response magnitude. These poststimulatory effects were characterized by complex interactions among stimulus variables (conditioner duration, conditioner level, and interstimulus interval) with similar interactions occurring for both monotic and dichotic stimuli. A simple superposition effect of the responses to the conditioner and test stimulus does not account for the effect of prior stimulation since responses often exceeded the sum of the responses to the conditioner and the test stimulus alone.

Acoustic Stimulation↗
PubMed1994

Stapedotomy with stapedius tendon preservation: technique and long-term results.

From 1975 to 1992, a total of 1459 primary stapedoplasty operations (i.e., stapedectomy, stapedotomy with tendon section, and stapedotomy with tendon preservation) were performed in 1323 subjects at the Ear, Nose, and Throat Department of the University of Verona. Pure-tone audiometry was carried out in all subjects who were operated on and who underwent 6-month and 10-year follow-ups. To evaluate the influence of stapedius tendon preservation on functional outcome, we randomly selected subgroups of patients using the three different stapedioplasty techniques and tested them by multiple-frequency tympanometry, psychoacoustic tuning curves, and speech discrimination in noise. Finally, to assess the effect of prosthesis diameter on middle ear transfer function, we used the electrocochleographic technique and examined the threshold and latency of cochlear nerve compound action potentials recorded during surgery from the round window. The results of this study show that the best auditory performance in otosclerotic subjects is achieved by performing a stapedotomy of 0.7 mm diameter, using a 0.6 wire-Teflon piston, and preserving the stapedius tendon.

Acoustic Impedance Tests↗
PubMedDate not supplied

Auditory fatigue in patients with stapedius muscle paralysis.

Experiments were performed in 18 patients with peripheral facial palsy (Bell's palsy) including unilateral stapedius muscle paralysis. After exposure to narrow band noise centered at 0.5 kHz temporary threshold shift at 0.75 kHz was significantly higher in the ear with paralysis than in the normal ear. After exposure to 2.0 kHz narrow band noise there was no difference in TTS at 3.0 kHz between affected and non-affected ear. It was concluded that the stapedius reflex has a protective function against low frequency sound exposure and suggested that this protection might be extended to higher frequencies only when high frequency noise also contains low frequency components.

Acoustic Stimulation↗
PubMedDate not supplied

Classical conditioning of the stapedius muscle.

A delayed conditioning paradigm was employed to condition the stapedius muscle. While many previous attempts have failed using loud sound as the unconditioned stimulus(UCS), this paper presents evidence of successful conditioning of this muscle when the unconditioned stimulus was a mild electrocutaneous stimulation of the external ear canal. Using a weak tone as the conditioned stimulus, conditioned responses were readily obtained in eight of ten subjects after only 30 or fewer toneshock pairs. Temporal con ditioning was also demonstrated. A parallel is shown to exist between attempts to condition the pupillary and stapedius reflexes.

Acoustic Stimulation↗
PubMed1994

Stapedius reflex and EABR thresholds in experienced users of the Nucleus cochlear implant.

Evoked auditory brainstem responses (EABR) and stapedius reflex thresholds were established in 7 experienced users of the Nucleus cochlear implant. Even using biphasic 400 microseconds/phase clicks for the EABR, responses were observed in only 5 patients; no stapedius reflex (SR) was seen in 3 patients, 2 of whom had a history of middle-ear disorder. The EABR threshold varied widely between subjective threshold and uncomfortable loudness level (ULL) for the same stimulus. The average SR threshold was found somewhat more consistently at 66% of the dynamic range between threshold and ULL, but grossly overestimated the most comfortable level (MCL) in most cases. To obtain equal loudness at the same current level we suggest that broad clicks (300 microseconds/phase) be used for EABR measurements, thus compensating for the lower repetition rate of EABR stimulus compared with the device fitting stimulus.

Acoustic Stimulation↗
PubMed1994

Tympanometry, stapedius reflex and hearing impairment in children with otitis media with effusion.

The study assessed the relationship between tympanometry, stapedius reflex and pure tone audiometric hearing impairment. A total of 581 audiograms and typanograms from 370 children aged between 3 and 10 years were studied. Only one ear was examined. Measurements of the pure tone air conduction thresholds (PTACT) were made: firstly as an average of the thresholds from 500, 1,000, and 2,000 Hz, secondly as an average of six frequencies from 250 Hz to 8 Hz. The mean PTACT were calculated for each year of age and for each type of tympanogram. Tympanograms were further subdivided by the presence or absence of the stapedius reflex. The sensitivity, specificity and predictive value of a type B tympanogram were investigated for different ages in relation to mean six frequency PTACT at 20, 25 and 30 dB HL. The results were used to show the accuracy of a type B tympanogram in detecting hearing impairment in children of different ages. The results suggest that tympanometry may be used to screen younger children with otitis media with effusion for hearing impairment, without the need for a pure tone audiogram.

Acoustic Impedance Tests↗
PubMedDate not supplied

Stapedius reflex abnormalities in multiple sclerosis.

Thirteen patients suffering from multiple sclerosis were analyzed by a Madsen ZO 70 electroacoustic bridge connected to an electronystagmograph through an impedance adaptor. Threshold, amplitude, decay and difference limen of intensity (DLI) of the stapedius reflex were examined for the frequencies 500, 1 000, 2 000 and 4 000 Hz. The difference between standard audiometric results and stapedius reflex data stresses the value of reflex measurements in assessing brain stem pathology.

Acoustic Stimulation↗
PubMed1982

Time course of the human acoustic stapedius reflex. A comparison of eight different measures in normal-hearing subjects.

Different measures of the dynamic properties of the contralateral stapedius reflex were compared in normal-hearing subjects. The stapedius reflex was measured as change of the acoustic impedance at 800 Hz. The stimulus was a 1-s burst of pure tone at 500 or 2000 Hz with a rise time of 10 ms; a 25-ms burst of pure tone at 500 Hz, rise time 2 ms; an amplitude modulated 500 Hz pure tone (30% modulation depth); a continuous pure tone in which a 1-s pause was introduced after at least 5 s. Onset was measured as rise time to 50% of maximum response and offset as time from end of stimulus until 50% of response amplitude was reached. The impulse response was quantified by time from start of stimulus to peak of response. The frequency transfer function was characterized by the 6 dB (half amplitude) cut-off point and decay was measured in percentage during a 5-s period. Recovery was quantified as the relative regain of amplitude after a 1-s pause. It was found that impulse response correlated to rise time for response to tone burst. Onset and offset were not correlated. Amplitude modulation was a mixture of onset and offset properties and not correlated to either measure. The decay and recovery were (nearly significantly) correlated and are probably different measures of the same process. A simplified test procedure for different aspects of time course was suggested but it remains to be shown if the pattern in pathological cases follows the pattern found in the present group of normal subjects.

Adaptation, Physiological↗