Clinical-histopathological correlations in experimental otitis media: implications for silent otitis media in humans.

Clinical-histopathological correlations were sought in an experimental animal model of otitis media. Among 20 chinchillas inoculated intranasally with wildtype influenza A/Alaska virus (H3N2) and type 7F Streptococcus pneumoniae, 15 animals (18 ears) developed otoscopic and tympanometric signs of otitis media with middle ear effusion. Middle ear inflammation was most intense 10 days after virus inoculation. Twenty-two days after virus inoculation, eight ears showed diffuse middle ear histopathology and contained effusion, which cultured pneumococcus, five ears showed focal histopathology, and four of the five contained no effusion. Clinical manifestations of otitis media had disappeared in four of the 13 ears with pathology at sacrifice; otoscopy was normal in all four ears, tympanometry was normal in three ears, and both otoscopy and tympanometry were normal in one ear. All four of these ears with clinically "silent" middle ear histopathology had shown abnormalities of ear drum appearance or tympanometry between 7 and 14 days after inoculation. Discordance between histopathology and the clinical examination performed at sacrifice was greatest for ears with focal pathology.