Experimental Studies on the Stapedius Reflex Response and the Influence of Different Peri Lymphatic Pressures in Human Temporal Bones

Abstract

An acoustically elicited stapedius muscle contraction in man has been shown to cause either an outward or an inward displacement of the tympanic membrane. Change of posture affects the displacement and three different patterns of movement have been found. In the present study experiments on human temporal bones were performed. A simulated muscle contraction was elicited by loading the stapedius muscle with weights, and the effect on the displacement of the tympanic membrane caused by applying different pressures to the perilymph was studied. In these experiments it was possible to reproduce all three patterns of stapedius reflex response which had been observed in man as caused by change of posture. The results thus indicate that the different responses found in man and induced by change of posture can be explained by a change in the perilymphatic pressure. It was also observed that the movement of the stapedial footplate caused by a simulated stapedius muscle contraction induced an increase in the volume of the perilymphatic space. Furthermore the movement of the tympanic membrane and the long process of incus always took the same direction.