しん出性中耳炎の耳管機能に関する実験的研究

Abstract

The pathogenesis of otitis media with effusion (OME) in relation to eustachian tube function was investigated in rats.First, the passive function of the eustachian tube was examined by the inflation-deflation test and the forced response test in experimental OME induced by the intratympanic injection of E. coli endotoxin (ET). Before injection passive opening pressure (Po) was 292.1±64.7 mmH2O, closing pressure (Pc) was 184.5±49.1 mmH2O, tubal resistance (R2) was 85.8±23.7 mmH2O/ml/min. OME persisted for up to 2 days. On the day after inoculation Po, Pc, and R2 were significantly higher than before.Second, the third branch of the trigeminal nerve (V3), which supplies the tensor veli palatini muscle (TVPM), was cut and the four eustachian tube function tests were repeated. The three passive tubal ventilatory tests (inflation-deflation, forced response, and eustachian tube function in a pressure chamber) showed that Po, Pc, and R2 were significantly lower than before the nerve was cut; the negative pressure test indicated that negative middle ear pressure was not released even by swallowing. This dysfunctional eustachian tube model is considered to represent the compliant tube (floppy tube), which is characterized by low middle ear pressure for passive opening and functional obstruction under negative middle ear pressure.Third, three eustachian tube function tests (inflation-deflation, forced response, and negative pressure) were performed after ET inoculation and V3 section. Middle ear effusion was observed for 5 days or longer in all the rats. Compliant tube features were seen on the fourth day, and they persisted even after the effusion cleared.In conclusion, these experimental studies indicate that both inflammation and tubal dysfunction are probably important factors in the pathogenesis of OME.