Degeneration and reorganization of vestibular epithelia after local aminoglycoside application in the mammalian inner ear.

The development of degeneration of vestibular end organs and their possible reorganization have been observed over a 2 year period after local application of sisomicin in the inner ear using scanning electron microscopy (SEM). Degeneration of stereocilia took place as early as 5 days after the treatment in the utricule, the saccule and the cristae. At 10 days, almost the entire surface of these sensory epithelia presented a smooth aspect without specific structure. However, after 15 days, an epithelial reorganization developed with clear limits between cells. At 25 days, systematic kinociliary structures were observed at the apical surface of the cells. Five months after the treatment, the new kinocilium was still present and sometimes stereociliary-like structures appeared in the three types of vestibular organs. Two years after treatment, the kinocilium persisted and the embryonic-like ciliary tufts had disappeared. These SEM observations suggest that in mammals some vestibular epithelial regeneration is possible but stops at a stage which could correspond to an early developmental level.