キヌタ骨の転位を伴う先天性耳小骨奇形疑い例

A case of congenital ossicular malformations with incus dislocation

はじめに

　先天性耳小骨奇形は，発生学的な見地と奇形の部位・病態から3つの群に区分された船坂らの分類^1,2）が引用されることが多い。最も頻度の高いキヌタ-アブミ関節離断では，アブミ骨上部構造が消失することも稀ではない。また先天性耳小骨奇形に中耳炎が合併すれば，さらなる形態変化が生じる可能性もありうる。

　今回，アブミ骨上部構造の消失に加えて，長脚が欠損したキヌタ骨が遊離・転位した症例を経験した。この病態をもたらした原因を考察すべく，文献的考察を中心に報告する。

　なお本研究は伊勢赤十字病院倫理委員会の承認を得ている（ER2024-15）

　Congenital ossicular malformations have been dealt as a common disease and detected at an early age because of generalized school medical examinations and higher success rate of surgery. However, cases of delayed diagnosis of hearing loss with otitis media and effusion have been observed. We present the case of 13 year-old boy with hearing loss of 61.3 dB. Preoperatively, elevated bone hearing level at 4000 Hz and disappearance of the stapedial reflex were observed. Computed tomography revealed incus dislocation and illegible stapes. Exploratory tympanotomy revealed the long processus of the incus and superstructure of the stapes. Although the disappearance and dislocation of the incus with small granulation were observed, cholesteatoma was not detected and hearing level improved to 31.3 dB postoperatively. Although the patient was diagnosed with a congenital ossicular malformation with inflammation due to intubation, congenital cholesteatoma resolved spontaneously.