Eustachian tube gland changes in acute otitis media

OBJECTIVES: To investigate the histomorphologic impact of acute otitis media on the subepithelial glands of the eustachian tube. Previous investigations have shown an increase of eustachian tube goblet cell density during and up to at least 6 months after acute otitis media.

STUDY DESIGN: Longitudinal study in an experimental animal model of acute otitis media caused by Streptococcus pneumoniae.

METHODS: Bacterial middle ear challenge, after which the animals were killed, in groups of five rats on Days 4, 8, 16, 90, and 180. Dissection and preparation of the eustachian tube and adjacent structures, followed by serial transverse sectioning, periodic acid-Schiff/alcian blue staining, and qualitative/quantitative morphometric light-microscopic investigations of the histomorphology of the eustachian tube glands, in particular, the stainability, composition, volume, and number of gland acini.

RESULTS: The volume of the eustachian tube glands progressed to peak 16 days after inoculation, followed by a gradual normalization. The volume was still increased 3 months after the acute infection but completely normalized after 6 months. The increase was primarily due to hypertrophy of the mucous gland components, as the serous gland component volume and number of gland acini was unchanged. The periodic acid-Schiff/alcian blue staining of the mucous gland acini changed temporarily during the acute infection, indicating changes in mucus glycoprotein composition, from neutral to acidic/sulfated.

CONCLUSION: The volume of the eustachian tube glands increases during and up to at least 3 months after acute otitis media, primarily because of hypertrophy of the mucous gland components. This may compromise tubal ventilatory and drainage function.