Epidermoid Formation in the Middle Ear Cavity

Overview

Cholesteatoma is an accumulation of stratified squamous epithelium in the middle ear, comprisingboth living cellular matrix and the dead keratinous layer. There are two types of cholesteatomaacquired and congenital. The pathogenesis of cholesteatoma is still not well understood. One theoryof development of congenital cholesteatoma is Michaels’ theory of epidermoid formation. Theepidermoid foci are at the same site asmany congenital cholesteatomas, i.e. in the anterior superiorpart of the middle ear. In our study 92 foetal temporal bones were examined and epidermoidformation was found in 16 i.e. 17%. We found 39 epidermoid formations in 16 temporal bones, thusthere were several epidermoid foci, in one temporal bone (maximum 7). The epidermoid formationspresented several configurations: 21 superficial, 13 spherical and mixed, 4 elongated into thesubepitheliumand one intraepithelial. Twenty - one epidermoid formations (53.8%) were at the mosttypical site e.g. in the anterior superior part of the middle ear. The gestational age of the foetuseswere from 13 to 42 weeks.We did not find any epidermoid formation after the 33rd week of gestation.

Key words:
epidermoid formation, temporal bone, foetus, middle ear, histology, cholesteatoma.