Objective: Analysis of labyrinthitis in a model of otitis media.

Methods: Morphologic study in 20 Wistar rats in which otitis media was induced by transbullar inoculation of Pseudomonas aeruginosa with obstruction of the eustachian tube.

Results: Seventy percent of rats showed vestibular signs. Histologic changes ranged from nonaffected labyrinths to suppurative labyrinthitis.

Conclusions: Dissemination of infection probably occurs through round window membrane. A thinner round window membrane typical of rodents would be the reason for a more severe clinical and morphologic picture in rats when compared to human beings.