Sensorineural hearing loss in experimental purulent otitis media due to Streptococcus pneumoniae

Sensorineural hearing loss (SNHL) has been described clinically following chronic otitis media with effusion, but to the best of our knowledge, no studies have demonstrated SNHL in an animal model of otitis media. Using the chinchilla model of pneumococcal otitis media, significant SNHL was demonstrated after purulent otitis media, especially at higher frequencies. Animals with otitis media received penicillin G procaine treatment for five days after otitis media with effusion (OME) was first documented; resolution of middle ear infection was confirmed by middle ear effusion culture in all animals. Both the inoculated and uninoculated ears were examined by tone burst-elicited compound action potential at threshold. The inoculated ear showed a marked hearing loss of 13 to 36 dB three to four days after OME was first documented; a hearing loss up to 24 dB persisted two to five weeks after inoculation. The change in the compound action potential was highly significant at all frequencies studied. Conductive losses were largely ruled out because there was no middle ear effusion at death and the tympanogram was normal. Purulent labyrinthitis was ruled out by histopathological study. These results indicate that purulent pneumococcal otitis media in the chinchilla model causes significant SNHL and suggest that the pathogenesis of SNHL associated with chronic OME in humans may be studied in this model.