The morphological changes in the vestibular sensory epithelia following electrical stimulation

The morphological changes of the vestibular sensory epithelia of the guinea pig following electrical stimulation were investigated using scanning electron microscope. Positive and negative square wave pulse stimulation was given through a silver ball electrode placed on the round window membrane for one hour. The current intensities used were 100, 200 and 300 microA. While the direct current stimulation at intensities of 100 or 200 microA did not cause any significant changes, severe damage of the utricular macula and the ampullar crista of the lateral semicircular canal was observed at 300 microA. The degenerative changes such as fusion of sensory hairs, protrusion of the cuticular plate and loss of sensory cells were found on both the utricle and the semicircular canal. In the most severely damaged area, the sensory epithelial surface was badly torn apart. In the clinical application of direct current to the inner ear for relieving tinnitus, special attention should be paid to the vestibular organ.