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At least 145 records · Page 8Linked to original sources
PubMed2005

Influence of anaesthetic agents on transient evoked otoacoustic emissions and stapedius reflex thresholds.

This aim of this study was to determine the effect of anaesthetic agents on stapedius reflex (SR) thresholds and transient evoked otoacoustic emissions (TEOAE). Fifty patients who were scheduled for operation and who had normal hearing were included in the study. All were given midazolam for premedication and propofol for induction. Anaesthesia was maintained in five different ways in each group of 10 patients. Groups I-IV received inhalational anaesthesia: group I received 70 per cent N2O plus 30 per cent O2, group II sevoflurane, group III desflurane and group IV halothane. Group V received total intravenous anaesthesia with propofol plus sufentanil. The SR and TEOAE of the patients were measured four times: on the day before surgery (first measurement), after premedication (second measurement), after induction of anaesthesia (third measurement) and during maintenance of anaesthesia (fourth measurement). Midazolam significantly increased ipsilateral and contralateral SR thresholds and decreased TEOAE wave reproducibility. Propofol significantly increased only the SR thresholds. The other anaesthetic agents significantly increased only the contralateral reflex thresholds. Of these, the highest increase was seen after sevoflurane and the lowest after halothane. The changes in TEOAE wave reproducibility due to anaesthetic agents used for maintenance were not significant. We concluded that midazolam premedication may affect audiological evaluation with SR and TEOAE tests, and sevoflurane should not be used when it is necessary to measure SR under general anaesthesia.

Adolescent↗
PubMed1988

Prediction of dynamic range from stapedius reflex in cochlear implant patients.

Amplitude growth functions of the electrically elicited stapedius reflex were compared with behavioral estimates of dynamic range in seven patients using multielectrode cochlear implants. The range between threshold and saturation level of the amplitude growth function usually either encompassed or fell between the preferred and uncomfortable listening levels. Implications of these findings for the initial mapping of electrodes in young children are discussed.

Adult↗
PubMed1979

The effects of aging on the stapedius reflex thresholds.

The acoustic reflex thresholds for broadband noise and 500-, 1000-, and 2000-Hz activating signals were measured in a group of young normal hearing adults and a group of elderly normal hearing subjects. The results indicated that the acoustic reflex thresholds for tonal activating signals in the young subjects were similar to those in the elderly subjects. However, the acoustic stapedius reflex thresholds for broadband noise activating signals is significantly higher in the elderly subjects than in the young. These differences were explained in light of Bredburg's findings [Acta Otolaryngol. Suppl. 236, 1--135 (1968)] regarding degeneration of outer hair cells as a function of aging.

Acoustic Stimulation↗
PubMed1981

Effect of sensorineural hearing loss on the stapedius reflex growth function in the elderly.

The effect of sensorineural hearing loss upon stapedius reflex growth functions was studied in the elderly. The reflex activators were pure tones (500, 1000, and 2000 Hz) and broadband noise; reflex magnitude was expressed in decibels relative to static acoustic impedance. When expressed in decibels relative to reflex threshold, the mean growth functions of the elderly were reduced compared to previous data for young subjects [Silman, Popelka, and Gelfand, J. Acoust. Soc. Am. 64, 1406--1411 (1978)] and the noise functions differed in terms of both shape and magnitude. When expressed in SPL, the mean growth functions of the normal hearing elderly demonstrated saturation at high activator levels, whereas saturation was not observed in the mean growth functions of the hearing loss subjects. In the normal elderly, saturation was found to be frequency dependent. The saturation effect is discussed in terms of energy integration of the reflex response in the aging ear.

Acoustic Stimulation↗
PubMed1993

Ultrastructure of nerve endings in the stapedius muscle of the squirrel monkey.

The stapedius muscle of the squirrel monkey (Saimiri sciureus) was studied electron microscopically with regard to neuromuscular junctions, muscle-tendon junctions and tendons. Two types of neuromuscular junctions were identified. The first type which was predominant in number showed well-developed primary and secondary synaptic clefts. They were almost the same with those of other mammalian skeletal muscles. The second type showed a flat-shaped junction with fewer secondary synaptic clefts. Muscle-tendon junctions were characterized by many interdigitations between the muscle fibers and tendon. The tendon was composed of collagen fibers, approximately 70-100 nm in diameter. Muscle spindles were not present, while nerve endings resembling the Golgi tendon organ were found adjacent to the tendon and the muscle-tendon junctions. These findings suggest that a feedback system may exist and regulate the fine contractile function of this muscle.

Animals↗
PubMedDate not supplied

Stapedius reflex to electrical stimulation in a patient with a cochlear implant.

In a patient with a multichannel cochlear implant, it was possible to demonstrate stapedius reflex contraction to intracochlear electrical stimulation. Using a standard immittance measurement technique, characteristics of the electrically evoked reflex were compared to analogous characteristics of the acoustically evoked reflex. Latency-intensity functions were similar for the two modes of excitation, but reflex waveform morphology and amplitude growth functions were different.

Acoustic Stimulation↗
PubMedDate not supplied

Dynamic parameters of the stapedius muscle reflex in response to stimuli of varying duration but with the same energy content.

An evaluation was made of the behaviour of the dynamic parameters of the stapedius contraction reflex (latency, amplitude, recruitment time, duration, and efficiency) in response to stimuli with the same energy content but of different duration. A comparison was made with the results of a similar experiment in which stimuli with different energy contents were used. As adumbrated in earlier studies, it was found that these parameters are more subject to the influence of the temporal characteristics of the stimulus than to its energy content.

Acoustic Stimulation↗
PubMed1996

Binaural interaction of stapedius reflex.

It is known that stapedius reflex (SR) shows bilateral interaction and that its center is located in the brainstem. In the present study, the pattern of SR was compared in two different conditions, either with binaural acoustic stimuli or with monaural stimuli using the impedance measurement method. When the sound source was placed in front of the head model, the amplitude of impedance change was higher in the binaural hearing condition than in the monaural condition, suggesting bilateral superposition. When the sound source was placed laterally to the head model, the amplitude of impedance change was higher in the ipsilateral ear than in the contralateral ear in the binaural condition. In the monaural condition, the amplitude of impedance change in the ipsilateral ear was as high as that obtained in the ipsilateral ear in the binaural condition, whereas it was markedly low in the contralateral ear. It is assumed that sense of sound direction cannot be well maintained without binaural interaction of SR.

Acoustic Impedance Tests↗
PubMedDate not supplied

The stapedius reflex tests in retrocochlear hearing disorders.

The commonly used parameters of the stapedius reflex responses in the diagnosis of sensorineural hearing disorders are the reflex threshold level and the persistence of the reflex response on prolonged stimulation, i.e., the reflex decay test. With the object of establishing the sensitivity of these reflex parameters to identify tumours affecting the eighth nerve in the early stages, a series of 97 such cases were examined. The mean hearing loss of the affected ears was 32 dB; 28 of the cases still had normal thresholds of hearing; 95 of the ears demonstrated elevated reflex thresholds and/or pathologic reflex decay. To check the specificity of the test, a control series with sensorineural hearing loss and reflex threshold elevation or pathologic reflex decay was analysed with respect to clinical diagnoses. In every third case of reflex threshold elevation and in every second case of reflex decay, the medical diagnosis confirmed a disease known to be associated with retrocochlear dysfunction. It was also noted that none of the cases with brain stem lesion demonstrated reflex decay--an observation which supports the idea of the reflex decay phenomenon as specifically associated with eighth-nerve lesions.

Cranial Nerve Neoplasms↗
PubMed1988

Stapedius reflex threshold in cochlear implant patients.

The contralateral stapedius reflex elicited by sinusoidal electrostimulation via cochlear implant was investigated in 12 patients. Contraction of the middle ear muscle was monitored by time-resolved synchronized digital sampling of the impedance change in the contralateral ear. The reflex was detected in all patients in whom the uncomfortable loudness level (UCLL) could be reached and who had intact middle ear function. Generally, the reflex threshold is located in the upper part of the dynamic range between the most comfortable loudness (MCL) and the UCLL. The demonstrated method may provide suitable assistance in speech processor adjustment in difficult-to-test patients.

Adult↗
PubMed1990

Changes of stapedius reflex and hearing threshold in patients receiving high-dose cisplatin treatment.

The value of stapedius reflex (SR) measurement in the clinical management of the ototoxic side-effect of cisplatin was examined in 24 patients who had received a dose of 100-120 mg/m2. The main finding was a frequent but inconsistent deterioration of the SR threshold (SRT) at 3 and/or 4 kHz, usually with a moderate rise of the hearing threshold (HT) in the frequency range 3-8 kHz. A hearing loss exceeding 60 dB HL is detected with high probability as an SRT deterioration. None of the patients showed any influence on the SRT before the HT rise could be detected. The SR test cannot replace pure-tone audiometry for the identification of cisplatin ototoxicity. The pathological SR results observed in this study indicated a cochlear lesion. It was not possible to identify those patients most susceptible to ototoxic changes from the pretreatment results of the SR test.

Adult↗
PubMedDate not supplied

Effect of stimulus duration on stapedius reflex threshold in electrical stimulation via cochlear implant.

The effect of stimulus duration on the threshold of the contralateral stapedius reflex was investigated in patients supplied with a Vienna cochlear implant (analog stimulation via CI) and compared to results of a normal-hearing reference group in case of acoustic stimulation. Changes in reflex threshold were determined at four frequencies (125, 500, 1,000 and 2,000 Hz in case of electrostimulation and at 500, 1,000, 2,000 and 4,000 Hz for acoustic stimulation) and for five durations (30, 50, 100, 300 and 500 ms). The comparison of the two stimulation modes was accomplished by using the same instrumentation and procedure. Reflex threshold was evaluated according to an objective criterion based on the individual noise distribution of recordings without reflex and by subjective judgement. For both stimulation modes a strong effect of stimulus duration on reflex threshold was observed (p < 0.001). The amount of temporal integration reflected by the threshold difference between 500 and 50 ms was approximately 2-4 dB for electrical stimulation via CI and 6 dB for acoustic stimulation in normal-hearing individuals. In case of electrostimulation, the reflex threshold for stimuli of 30 ms was most often above the limit of uncomfortable loudness sensation; the increase in reflex threshold for acoustic stimulation between 500 and 30 ms was approximately 14 dB. There was no evidence of frequency effect on reflex threshold nor an interaction between frequency and stimulus duration for either stimulation mode.

Adult↗
PubMed1984

Stapedius reflex and brainstem auditory evoked responses in multiple sclerosis patients.

The stapedius reflex (SR), its adaptation and the brainstem auditory evoked potential (ABR) were recorded in a group of 53 multiple sclerosis patients. All cases were classified as definite according to Schumacher's criteria, and their grade of disability in Hyllested's system was 1-4: no cases of the gravest (grades 5 and 6) disability were included in the series. The peripheral hearing (pure-tone audiogram and speech threshold) was normal in 44 and slightly impaired in 8 cases. SR was abnormal in 6 (11%) and borderline in 11 (21%), whereas the ABR was considered abnormal in 21 (40%) patients. Deviant SR and ABR findings had only slight or no correlation to clinical data. Intercorrelation between SR and ABR abnormality was better but not implicit and a few cases with deviant ABR showed normal SR: The frequency of abnormal and borderline SR findings was clearly higher in bilateral than in unilateral ABR abnormality. Subclassification of ABR into an upper and a lower type of pathology did not correlate with SR abnormality.

Adult↗
PubMed1991

The effect of quinine on psychoacoustic tuning curves, stapedius reflexes and evoked otoacoustic emissions in healthy volunteers.

Quinine causes reversible hearing loss, closely related to the quinine plasma concentration. The effects of quinine on psychoacoustic tuning curves, stapedius reflex thresholds and evoked otoacoustic emissions were studied in healthy volunteers. The tuning curves became shallower, whereas reflex thresholds were unaffected. The shift in the emission thresholds paralleled that of the pure-tone thresholds. There were also qualitative changes in the emissions: 1) the exponent of the stimulus-response function changed from 0.34 to 0.56; 2) decay time shortened; 3) the power spectrum shifted towards lower frequencies. The results are discussed in relation to various aspects of cochlear performance and are suggested to depend on an outer hair cell dysfunction.

Acoustic Stimulation↗
PubMed2002

Relationship of intraoperative electrically evoked stapedius reflex thresholds to maximum comfortable loudness levels of children with cochlear implants.

Previous studies of the relationship between the intraoperatively obtained electrically evoked stapedius reflex threshold (ESRT) and the maximum comfortable loudness (MCL) values used to program the speech processor of cochlear implant (CI) patients have indicated that ESRTs provide an inexact estimate of MCL. In order to determine whether this estimate might be more exact for electrodes in different parts of the electrode array, we studied the electrode-specific relationships between ESRT and MCL in 29 Med-E1 Combi 40+ and 25 Nucleus CI 24 M patients after first fitting of the speech processor and 2 and 6 months later. The MCL values were mostly less than the ESRT values, but increased progressively over the first 6 months, reaching 83% and 72% of the ESRT values, on average, across all electrodes for the Med-E1 and Nucleus systems respectively. The population variation across electrodes decreased over the 6-month observation period and was least for the apical half of the array, for which the correlation coefficients of regressions between ESRT and MCL were around 0.65 for both systems. These results indicate that estimates of MCL values from the ERST are more accurate for the apical half of the intra-cochlear array and could then be described by an offset value plus an increase of MCL by 0.62 and 0.53 of ESRT for the Med-E1 and Nucleus systems, respectively.

Adolescent↗
PubMed2003

[Contralateral electrically evoked reflex of the musculus stapedius in patients with cochlear implant].

Registration of electrically evoked reflex is widely applied in rehabilitation of patients by cochlear implantation. As a rule, visual assessment of the ipsilateral reflex is made intraoperatively for functional evaluation of surgical results. Of interest is use of contralateral electrically evoked reflex of the musculus stapedius in the course of adjustment of the speech processor. We studied the latter reflex in 20 patients with cochlear implants Cl24M and Cl22 made by 'Cochlear'. 13 patients used Sprint processors, 7 patients - Spectra ones. Zodiak impedansometer registered the reflex which was recorded in 12 patients. The threshold of the reflex registration correlated well with comfortable perception of loudness. Most of the patients evaluated threshold (for the reflex) sound perception as the sound of moderate loudness. The conclusion is made that registration and analysis of the contralateral electrically evoked reflex can assess a comfortable stimulation level in adjustment of speech processors in patients with cochlear implants.

Adolescent↗
PubMed1990

The prognostic value of the stapedius reflex in peripheral facial palsy.

Stapedius reflex can provide useful prognostic information in FPs when the middle ear is normal. Its preservation may have a favorable significance in partial FP and Bell's palsy. Its loss, even though less reliable, can also have some value as an indicator for a poor prognosis in patients with total and herpes zoster FPs. Most importantly, our findings have shown that the SR alone is not sufficient to be of prognostic value, but is useful if combined with other clinical parameters and electrical responses.

Adolescent↗
PubMed1989

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

The stapedius muscle of the rat, a very small muscle, appeared to have several atypical morphological characteristics. The muscle fibres were found to be irregularly shaped and composed of relatively small bundles of myofibrils. Mitochondria were distributed irregularly, i.e. in long strands, between the bundles of myofibrils. Enzyme histochemically, most fibres could be classified as fast oxidative glycolytic fibres (IIA). Only 5% of the fibres appeared to be slow twitch fibres; however, these fibres also had a high glycolytic capacity and therefore could not be classified as the classical slow twitch fibres. The immunohistochemical staining with monoclonal anti-heavy chain myosin isotypes showed discrepancies when compared to the enzyme histochemical results. Moreover, different adult heavy chain myosin isotypes appeared to coexist in one single muscle fibre. The results suggest that the muscle has an isometric contraction pattern and that it can contract rapidly with great endurance. This endows the muscle with properties suitable for a function in the prevention of noise-induced hearing loss and also in impact noise over longer periods of time.

Animals↗