鼓室型先天性真珠腫—アブミ骨周囲に限局し，耳小骨奇形と合併していると考えられる3症例

Congenital Cholestcatoma in the Tympanic Cavity

I．はじめに

　先天性真珠腫は真珠腫の存在部位により大きく錐体部型と鼓室・乳突部型に分けられる。錐体部型は脳神経外科領域で取り扱われることが多く，内耳孔付近に発生し種々の脳神経症状を現わす。錐体上面の中頭蓋底にある場合は，顔面神経の膝神経節周辺に発生して進行性の顔面神経麻痺が初発症状になっていることが多い。

　一方鼓室型あるいは乳突部型においては，真珠腫は手術時にすでにある程度の大きさに増大していて，鼓室を充満し，時には乳突洞へと進展し，しぼしば鼓膜を裏面から押し上げるようになっていることが多い。はたしてこれが先天性なのか後天性なのか確診がつかない例もある。

Three cases with conductive hearing impair-ment and intact drumhead were operated on under the diagnosis of congenital ossicular anom-aly. A small cholesteatoma matrix was found around the stapes in each case. Different degrees of ossicular deformity and defect without con-nection to the cholesteatoma matrix were found in the long process of the incus and superstruc-ture of the stapes.

Though one patient had a history of acute otitis media, and the other patient had a history of insertion of tympanostomy tube in their child-hood, all three were diagnosed as congenital cholesteatoma. It is reasonable that congenital cholesteatoma could be combined with congenital ossicular anomalies, because there is the embryonic similarity of the two pathologies. It is interesting to demonstrate the very early appearance of con-genital cholesteatoma in the tympanic cavity.