It is thought that the gentamicin permeates the perilymph and the endolymph of the inner ear through the round and oval window membranes and damages the vestibular hair cells
. However, the use of intratympanic gentamicin carries the risk of inducing hearing loss.
Loss of vestibular hair cells
accounts for vestibular problems in some patients (9).
Morphological and physiological development of vestibular hair cells
in the organ-cultured otocyst of the chick.
Vestibular dysfunction etiology is still unclear; it has been hypothesized that the reflux of hyperosmotic fluid into the basal end of the cochlear duct may elicit vertigo, while degeneration of vestibular hair cells
due to osmotic and chemical imbalance maybe another mechanism of injury [9, 28, 33].
Most vertebrate vestibular hair cells
are topped with a bundle of stereocilia of increasing length and extended kinocilium and a bipolarity with maximum activation when deflected toward the kinocilium.
Some (amikacin, dihydrostreptomycin, and kanamycin) are primarily and/or initially cochleotoxic, while others (streptomycin and gentamicin) destroy vestibular hair cells
before cochlear hair cells.
Mechanoelectrical transduction (MET) of sound and motion by the inner ear is highly dependent on the ionic composition of the fluids bathing the auditory and vestibular hair cells (Tasaki and Fernandez, 1952; Smith et al., 1954; Corey and Hudspeth, 1979; Crawford and Fettiplace, 1983; Marcus et al., 1983).
Mechano-electrical transduction currents in isolated vestibular hair cells of the chick.
The different expression patterns of Pax2 and Sox2 in the vestibular versus the auditory organs suggest that the expression of these proteins might be associated with different requirements in vestibular hair cell
specialization [9, 32].