Abstract
The mechanism of pars flaccida type cholesteatoma, which we have considered, is as follows. Chronic inflammation in the attic is maintained due to a disturbance of ventilation which is induced by obstruction of the tympanic isthmus. As a result, the pars flaccida of tympanic membrane retracts, and the epithelium of the pars flaccida invaginates toward the mastoid cavity, accompanied by repeated infection and accumulation of debris in the retraction pocket.
However, there are some surgical cases of cholesteatoma which do not fit this theory. When the pars flaccida is retracted and the epithelium is localized in the attic (acquired cholesteatoma), another cholesteatoma (congenital cholesteatoma) is located just behind the acquired cholesteatoma. These cholesteatomas are independent.
It seems that congenital cholesteatoma, which is located in the aditus, block aeration (ventilation) of the attic, causing the pars flaccida to retract.
If retraction of the pars flaccida is accompanied by acute infection, both cholesteatomas become continuous and may be classified as an acquired cholesteatoma. Recently, we experienced three cases of such cholesteatoma which may contribute to elucidation of the pathogenesis of cholesteatoma.
