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Biomedical subjects

J E Zakrisson

Publications and source records attributed to J E Zakrisson.

13 recordsLinked 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↗
PubMedDate not supplied

The role of the stapedius reflex in poststimulatory auditory fatigue.

The human ear is very resistant against noise-induced damage in the low frequency range. The aim of the present study was to investigate whether or not the stapedium reflex is of any importance for this resistance. Subjects with peripheral facial palsy (Bell's palsy) including unilateral stapedius muscle paralysis were exposed to several different levels of narrow band noise centered at 0.5 and 2.0 kHz. Temporary threshold shift (TTS) at 0.75 kHz was significantly higher in the affected than in the nonaffected ear after 0.5 kHz noise at and above 110 dB SPL. After the exposure with 2.0 kHz narrow band noise there was no difference in TTS at 3.0 kHz between the affected and nonaffected ear. It is concluded that the attenuation provided by the stapedius reflex reduces TTS after low frequency noise exposure. An implication is that the stapedius reflex also may have the function of protecting the ear from hearing damage caused by low frequency noise exposure.

Acoustic Stimulation↗
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

The activity of the stapedius muscle in man during vocalization.

The EMG of the stapedius muscle and visible movements in the stapedius tendon during the subject's own vocalization of an [a:] and during contralateral acoustic stimulation were studied in subjects with eardrum perforation. The threshold for stapedius activity was near the lowest vocal intensity that the subjects could produce. At normal vocal effort the stapedius muscle was activated to about 50% of its maximum value. The EMG often started before the vocal sound, indicating that the stapedius muscle can be activated from the central nervous system as a part of the vocalization process. It is suggested that the contraction of the stapedius muscle during vocalization reduces the masking caused by the low frequency components of the person's own voice even at normal vocal effort and thereby improves intelligibility of simultaneous external speech.

Acoustic Stimulation↗
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↗
PubMedDate not supplied

The relaxation time of the stapedius reflex in dystrophia myotonica (Steinert).

Eight patients with dystrophia myotonica (Steinert) were studied. They all had myotonia and pathological EMG and in some cases other signs of the disease. The 50% relaxation times of the stapedius reflex were significantly prolonged compared with a control group of 40 healthy, young subjects with normal hearing and normal stapedius reflex thresholds. The relaxation times could be well quantified and had a low standard deviation from the mean in the control group. In the patient group as well as in the control group only slight differences in the relaxation times were found between the frequencies 500 and 2000 Hz and between the simultaneously measured ipsilateral and contralateral reflexes. It was concluded that measurement of the relaxation time of the stapedius reflex increases the diagnostic possibilities in patients with myotonia.

Adolescent↗