滲出性中耳炎と耳管

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The pathogenesis of otitis media with effusion (OME) in relation to the eustachian tube was investigated clinically and experimentally. Clinical observations revealed the follow i ng characteristic pathophysiological state of OME: 1. Among 300 ears with OME, organic obstruction or stenosis was rare (16%), but 95% of the patients could not equilibrate middle ear negative pressure by swallowing. 2. Even in the convalescent stage, most of the OME patients (91 %) could not equilibrate middle ear nagative pressure by swallowing, and this dysfunction of th e eustachian tube was thought to be a predisposing factor for OME. 3. Middle ear pressure of 30 ears of OME children measured transtubally using a catheter pressure transducer were slight negative, being within 100 m mH2O in m ost cases ( -54.0±58.9mmH2O). 4. After releasing middle ear negative pressure by myringotomy, middle ear effusion was excreted transtubally within one day in 24 of 30 ears with OME (80% ). Experimental studies using cats revealed the following results: 1. Abolishment of the active ventilatory function of the eustachian tube by transecting the tensor veli palatini muscle and pterygoid hammulotomy rarely caused OME (7.1%), indicating that the 'Hydrops ex vacuo' theory can not adquately explain the etiology of OME. 2. Mean negative middle ear pressure of -150.7 mmH2O was induced by ciliary clearance function of the eustachian tube within a few hours and -27.2 mmH2O was induced by muscular clearance function within three to four minutes when there was fluid in the closed middle ear space. 3. Transtubal clearance of middle ear fluid was significantly impaired in ears with tubal ventilatory dysfunction compared with normal ears. 4. Experimental OME induced by intratympanic injection of E. coli endotoxin was long-lasting when the tubal ventilatory function was impaired. From these clinical and experimental studies, the development of OME was not considered to be initiated from tubal obstruction but from fluid production within the middle ear. As a next step, negative pressure develops in the middle eardue to the tubal clearance function of the fluid. The important thing is that the eustachian tube of OME patients can not release this negative middle ear pressure, therefore, negative pressure progresses to be a state where the maximum negative pressure and fluid retention coexist within the closed middle ear space. This irreversible pathophysiological state continues until transtympanic ventilation such as myringotomy is performed. In conclusion, the eustachian tube dysfunction in OME patients is not the primary etiological factor of OME, but plays an important role in the characteristic long-lasting course of OME.
耳鼻咽喉科臨床学会の論文

滲出性中耳炎と耳管

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