Histopathologic Changes in the Vestibule after Cochlear Implantation

OBJECTIVE: The study goal was to determine the histopathologic changes of the vestibular end organs after cochlear implantation and to relate them to clinical performance. STUDY DESIGN: To differentiate the effect of implantation from the disease process that originally destroyed the hearing, 11 pairs of temporal bones from unilateral implantees were studied with light microscopy to compare the vestibular damage in the implanted ears with that in the nonimplanted ears. RESULTS: Significant histopathologic damage of the vestibular end organs was noted in 6 patients (54.5%). The major histopathologic findings were fibrosis in the vestibule, saccule membrane distortion, new bone formation, and reactive neuromas. The scala vestibuli involvement, as a result of damage to the osseous spiral lamina or basilar membrane in cochlear basal turn, was highly correlated with vestibular damage (75%). CONCLUSIONS: Although the clinical incidence of balance disturbance after cochlear implantation is low, damage of the vestibular end organs may occur and be asymptomatic. Keeping the electrode array in the scala tympani will minimize vestibular damage.