Mechanism of Eustachian Tube Balloon Dilation in Minipigs

In this study, in situ balloon dilation of the Eustachian tube (BDET) was performed using minipigs as an animal model to observe the dynamic process of damage and repair of the Eustachian tube mucosa and surrounding tissues. The Eustachian tubes of 30 minipigs were divided into seven groups. The five groups included an immediate postoperative group, a 1-week group, a 2-week group, a 3-week group, and a 4-week group following 3 mm balloon dilation. The other two groups were selected as the immediate postoperative group following 7 mm balloon dilation and the normal control group. The damage caused by the 7 mm-diameter balloon involved almost the whole circumference and length of the Eustachian tube, and the depth of the damage included epithelial injury and subcutaneous tissue compression injury, whereas the damage caused by the 3 mm-diameter balloon was relatively limited, with the whole-circumference injury limited near the tympanic orifice. The most noticeable process of postoperative repair was proliferation, with goblet cells recovering faster than other cells, followed by stratified squamous epithelium; pseudostratified columnar epithelium recovered the slowest, but the ciliated structure was restored. Eustachian tube injury was caused by mechanical force against the Eustachian tube wall and included limited stripping of the mucosa, compression and fragmentation of submucosal tissues, and localized linear tearing of the tube wall. The process of pathological repair was initiated immediately after dilation, and the damaged Eustachian tube regained its normal structure and function in about 4 weeks.