Tetsuo Ishii

Embryonic development of the human organ of Corti: Electron microscopic study

A morphological approach by the electron microscope was used to obtain findings suggestive of the onset of auditory function in the fetal human cochlea. The organs of Corti at three different embryonic ages: 20 weeks 3 days, 22 weeks, and 24 weeks, were studied from the following standpoints: auditory hairs; hair cell bodies; the interrelationship between sensory cells and supporting cells; fluid spaces in the organ of Corti; and nerve endings to the sensory cells. Assessment of these findings implies that the peripheral auditory organ is ready for sending afferent impulses at around 24 weeks of embryonic age.

The fine structure of lipofuscin in the human inner ear.

SummaryLipofuscin inclusions in the human membranous labyrinth were studied by electron microscopy. Lipofuscin is morphologically an irregularly shaped, membrane-bound inclusion consisting of an electron-dense structure. The most common component was a fine, granular, osmiophilic substance which was always associated with a homogenous, spherical structure resembling a lipid droplet. The combination of these two components was frequently observed in the human inner ear. Distended inclusions containing lipofuscin components were also observed within the supporting cells, saccular, utricular and ampullar wall, the epithelial cells of the transitional zone and in the dark cells. Lipofuscin is closely associated with lysosome and is known to accumulate in the tissue as a result of aging. The high lysosomal activity possibly may result in lipofuscin formation in the human inner ears. Also some other unknown metablic conditions may provide the deposits of lipofuscin.

Electron Microscopic Observations of the Utricle and Ampullae in a case of Dizziness of Suspected Saccular Origin

Electron microscopic observation was reported on the utricle and ampullae of a case, a 36-year-old male, with dizziness attack due to suspected saccular origin. After the removal of the utricle and ampullae, the dizziness recurred, and finally the saccular nerve section relieved the dizziness attack of this case. So the actual lesion was localized in the saccule and was not in the specimens obtained at the first surgery. Though most of hair cells appeared normal, there were a few with many vacuoles or shrinkage of the cytoplasm distributing sparsely throughout the sensory epithelia. The distribution of the pathological hair cells in the utricle was more general than in the ampullae. The sensory hair cells without pathology and the presynaptic structures were similar to those found in the experimental animals. Nerve and nerve endings showed normal structures. The findings may be physiological at this age group or an extension of the pathology of the dizziness-causing lesion.

Relationship among Morphological Anomalies of the Ears and Eyes in Congenital Deaf Children

耳介奇形をともなった 外耳道閉鎖または狭窄症は多 くの症例において高度の伝音系難聴 を示し, 骨導聴力は比較的良好である. したがって手術的に外耳道を造設 し, 鼓室成形をおこない, 聴力をあ る程度改善させる事 も可能である. しかし, これらの症例の中には内耳の障害をともない高度の感 音難聴または聾を呈する症例があ り, これ らの症例の手術効果には限度があるので注意を要する. こ れらの例は中耳奇形にともない内耳の奇形 も存在すると考 えられ, 骨迷路の奇形がある場合には側 頭骨の円軌道断層撮影で確認す る事ができる. またとくに本論文で強調したいのは, 内耳奇形にお いて感音性難聴または聾の存在はもちろんだが, それに加えて種々の程度の前庭平衡機能の障害が みとめられること, さらには, ある種の眼球運動障害と内耳障害 とが関連してい ることに注意を促 したい. 先天性難聴の原因には種々あるが, 手術などにより, 難聴が改善 され る可能性がある場合, 早期 に行なう事が望ましく, その正確な診断は重要である. ことに, 小児では, 言語発達に関連がある ため, 診断は, 3才 前後までに行なわれ ることが望ましく, それには諸種の他覚的検査を必要 とす る. また, 時をうつ さず, 適切な治療, 教育が行なわれ る必要がある. 先天性難聴は大別して, 次 の三者 となる. すなわち, (1)手 術あるいは, 補聴器により聴力の改善が可能であるもの. (2)読 唇 法などの聾教育によつて, 意志交換の可能であるもの. (3)いかなる手技, 教育によつて も意志交換 の困難な もの, の三つである. (1)に属するものは, 両側外耳道閉鎖症がある. これは, 手術により聴力改善が可能な場合 もある ので, 少なくとも, 一側の手術を早期に行ない, 言語障害をきたさない配慮が必要である. しかし, 両側外耳道閉鎖~狭窄症の中にも感音難聴があ り, 手術による聴力改善が望めない もの もある. こ れ らの症例の中には, 単に外耳の奇形のみでなく, 中耳, 内耳 さらに, 他の身体的奇形, ことに眼 の奇形をともな うこともあり, 今回, これらを中心に検討した.