Three-dimensional images of the temporal bone and experimental otitis media in Japanese monkeys

Since the middle ear structure of animals commonly used for experimental study is different from that of humans, we used the Japanese monkey (Macaca fuscatus) as an animal model for otitis media with effusion (OME). The exact similarities and differences of the ear structure between humans and Japanese monkeys were studied by the use of computer-aided three-dimensional reconstruction, in addition to light and electron microscopy. Otitis media with effusion was repeatedly induced by direct intratympanic inoculation of one of the following: keyhole limpet hemocyanin; following systemic immunization with keyhole limpet hemocyanin, Streptococcus pneumoniae; or endotoxin. The temporal bones were serially sliced with a diamond band saw, after which the histologic findings were examined by light and electron microscopy on the basis of macroscopic observations. Each substance induced OME equally, 2 to 3 days after inoculation. Inflammatory reaction of the middle ear mucosa extended to all of the air cells; subsequently, the inflamed mucosa returned to normal in each case along with normalization of both the tympanometric and otoscopic findings. No remarkable architectural change remained, even after OME was induced repeatedly. These findings are applicable to acute otitis media and acute mastoiditis. The development of chronic middle ear effusion was not observed in this study. The usefulness of the diamond band saw and computer-aided analysis for temporal bone histologic evaluations is emphasized.