Primary acquired and recurrent cholesteatoma versus residual cholesteatoma. A light- and electron-microscopical study.

A comparative morphological study was performed between the primary acquired and recurrent cholesteatoma on the one hand and the residual type on the other. Between these two groups of cholesteatomas, one can distinguish differences in the pathogenesis and clinical features which may have therapeutic implications. This study, based on light- and electron microscopy, revealed no essential differences in morphology between the two groups of cholesteatoma. In particular, infiltration of matrix into subepithelial tissues could be found in cholesteatoma both with and without signs of inflammation or infection in the perimatrix, and this phenomenon could be applied to both types of cholesteatoma. This morphological uniformity suggests that the differences in clinical features and pathogenesis should not influence the otologist's choice of therapeutic approach. The results of this study emphasize the importance of removing as much as possible of the adjacent subepithelial tissue during eradication of the cholesteatoma, regardless of clinical type of cholesteatoma or signs of infection.

The effect of external stimuli on rat middle ear epithelium in culture. Extracellular carbon dioxide concentration.

Serially cultivated rat middle ear epithelium was studied under exposure to various concentrations of carbon dioxide. Three experiments were performed exposing the epithelium to a gaseous environment containing 5 or 10% CO2 or to an atmosphere almost devoid of CO2. Oxygen was maintained constant at 20% and nitrogen was additionally supplied. Cells exposed at 0% CO2 showed a remarkably different morphology compared with the cultures at 5 and 10% CO2, cells could become extremely large at 0% CO2, also showing a great variation in shape and cell size within the culture. Proliferation was significantly impaired at 0% CO2 vis-à-vis the 5 and 10% experiments. Terminal differentiation, however, was not influenced by the different CO2 concentrations, indicating that in vitro, variation in CO2 concentration is of no importance regarding a possible differentiation of middle ear epithelium into a cornifying epithelium.