Hearing preservation with labyrinthine ablation in otitis media

Objectives: Iatrogenic fenestration of the inner ear in the presence of oti tis media is commonly associated with permanent hearing loss. Hearing can g enerally be preserved when the vestibular labyrinth is ablated in a control led manner in noninflamed ears. The purpose of this study was to examine th e feasibility of hearing preservation with violation of the inner ear in th e presence of middle ear inflammation. Study Design: Prospective and contro lled animal model. Methods: Otitis media was induced bilaterally in pigment ed guinea pigs with transtympanic injection of Streptococcus pneumoniae, no ntypeable Haemophilus influenzae, or formalin-billed nontypeable II influen zae, Two to 4 days after injection, the horizontal canal of one ear was tra nsected and sealed, Hearing was tested before and after labyrinthine ablati on, Results: Otitis media was induced in all ears. Bacterial cultures were positive in 19 of 20 S pneumoniae-injected ears, and in 10 of 16 nontypeabl e H influenzae-injected ears. One week after surgery, elevation of click th resholds (> 15 dB) was encountered in none of the fenestrated or unfenestra ted S pneumoniae-infected ears, in two of six unfenestrated and three of si x fenestrated nontypeable H influenzae-infected ears, and in one of five ki lled-nontypeable LI influenzae-injected ears both with and without fenestra tion, Conclusions: These data suggest that ablation of a semicircular canal in the presence of middle ear inflammation or infection does not necessari ly lead to profound sensorineural hearing loss. Hearing loss associated wit h iatrogenic violation of the semicircular canals may be more dependent on factors other than the presence of nonspecific middle ear inflammation.