Total Myringoplasty: Functional Aspects

Abstract

In recent experiments employing time-averaged holography, strong evidence was found supporting Helmholtz' hypothesis of 1868 concerning tympanic membrane action. Since this action requires the tympanic membrane to be tightly coupled to the manubrium and not to be subjected to stretch during its vibratory displacements, attention was focused upon tympanic membranes lacking the characteristic fiber network of membrana propria. The displacement patterns of tympanic membranes, 6 to 7 months after replacement (fascia grafts), were recorded in cats, once more using time-averaged holography. In general, these tympanic membranes were stiffer than normal ones, and coupling to the manubrium was poor. Thus, the maximal displacements occurring in atypical locations involved stretching of the membrane, and there was no indication of the normal transformer action. The combination of high compliance and good coupling found in normal tympanic membranes was thus shown to be facilitated by the intricate fiber network of membrana propria.