上鼓室真珠腫

特にその成因について

抄録

The initial steps of attic cholesteatoma formation has never been documented. Therefore, the true cause of this disease remains only to be speculated. The most frequently suggested hypothesis is the migration theory.
In order to clarify the conditions concerning the pathogenesis of attic cholesteatoma, the present study was conducted to search for predisposing factors for the development of this disease by way of clinical statistics and observations of the formation of, cholesteatoma in experimental animals.
An analysis of patients with attic cholesteatoma and of their courses after posterior tympanotomy has revealed that a majority of cases have a history of acute or secretory otitis media in childhood, an extremely sclerotic mastoid process which is suggestive of a genetic disposition, intratympanic negative pressure, and occlusion of tympanic isthmuses by fibrous or granulation tissue.
Experimental cholesteatoma in guinea pigs can be produced behind an intact tympanic membrane by injections of Glycerin into the middle ear. This viscous fluid cause eustachian tube obstruction, negative middle ear pressure, and middle ear inflammations. The cholesteatoma develops as a result of the proliferation of basal cells of the epidermis of the external auditory meatus or the tympanic membrane, growing into the granulation tissue which has formed in the middle ear space.
The conditions related to the etiology of attic cholesteatoma formation implied by the above observations are:(1) inflammatory changes around the ossicular chain ;(2) negative pressure in the attic, and (3) chronic dysfunction of the eustachian tube associated with incomplete pneumatization.