Experimental conditions for the development of persistent otitis media with effusion.

The purpose of this study was to investigate sufficient conditions for the development of long-lasting otitis media with effusion (OME) without any organic obstruction of the eustachian tube. Three experimental conditions were employed using 20 adult cats (27 ears). Only tubal ventilatory dysfunction with transection of the tensor veli palatini muscle and excision of the pterygoid hamulus resulted in a small incidence of OME (7.1%), which lasted for 5 weeks. Instillation of Escherichia coli endotoxin into the middle ears formed only a transient OME in 50% of the animals. Combination of these two procedures brought a high incidence of OME (85.7%), most of which lasted for more than 8 weeks. These studies showed that tubal ventilatory dysfunction alone was not a sufficient condition for the development of OME but was important for prolongation of the pathological state of OME. The production of inflammatory exudate was considered to be a trigger for the formation of OME.