[Myxomatous remnants in the human middle ear. Histologic studies of their regression and microtopography]

Remnants of embryonic mesenchyma in the human middle ear are visible until the end of the first year of life. They occur in the lateral part of the epitympanon as well as in the region of the cochlear fenestra. However, as a result of an incomplete pneumatisation of the middle ear, they undergo regressive changes via differentiation to precollageneous tissue to form, finally, the tunica propria of the mucoperiosteal layer of the middle ear. Microtopography of these remnants is due to genetic factors but also depends on the function of the Eustachian tube. Alterations of the impedance of the tympanic membrane and the ossicular chain are possible because of the location of these remnants. The importance of obstructions of the Eustachian tube for the persistence of the remnants is discussed, as well as the part that they play in the pathogenesis of cholesteatoma of the middle ear.