The author classified the cholesteatoma of the ear region into 3 groups, that is, middle ear cholesteatoma, meatal cholesteatoma, and inplantation cholesteatoma, and assumed their origin.
Further, middle ear cholesteatoma was divided in the epitympanal type (attic type), the mesotympanal type (tensal type) and the non-perforative type.
Statistically, 58 cases of the attic type, 82 cases of the tensal type and one case of the non-perforative type were obtained. The attic type might be originated from the invagination of Shrapnell's membrane provoked by the inflammation of the external meatus, while the tensal type caused by the metaplasia of mucous membrane of the tympanic cavity during the course of chronic otitis media.
Meatal cholesteatoma was seen in 2 cases.
The foundamental conditions originating cholesteatoma were considered as follows;
1) Epidermis must be kept in such situation as a sack form or a cavity form. 2) Stimulation provoking ablation or proliferation into deep layer must be given to the epidermis.
3) Tissue surrounding that cavity-formed or sack-formed epidezmis must be solid as to produce the higher pressure in the cavity as the result of ablation and accumulation of epidermis.
As the predispositions of cholesteatoma, low age and the limited pneumatization of the middle ear are needed. Pneumatization may have not a certain correlation with the type of cholesteatoma probably because of its original diversity. In the attic type, only 15 cases showed remarkable pneumatization, while 43 cases showed limited pneumatization. In the tensal type, remarkable pneumatization was seen in 44 cases, while limited pneumatization in 38 cases.
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