Cochlear implantation via round window or cochleostomy: Effect on hearing in an animal model.

OBJECTIVES/HYPOTHESIS Cochlear implantation in patients with residual hearing has increased interest in hearing preservation. Two major surgical approaches to implantation have been devised: via the round window membrane and through cochleostomy. However, the advantages of either approach on hearing preservation have not been established. Due to the great inter- and intravariability among implantees, the current study used a normal-hearing animal model to compare the effect of the two methods on hearing. STUDY DESIGN Animal study. METHODS Thirteen fat sand rats were studied, in which 13 ears were implanted through cochleostomy and 13 via the round window. Hearing thresholds were determined by auditory brainstem responses to air and bone conduction at low and high auditory stimuli. RESULTS The results indicated that each stage of the surgery, primarily the opening of the membranous labyrinth, was accompanied by significant deterioration in hearing. Hearing loss was mainly conductive, with no significant differences between the surgical approaches. CONCLUSIONS Both surgical approaches carry similar risk of hearing loss. LEVEL OF EVIDENCE NA Laryngoscope, 126:E375-E378, 2016.