Influence of long-term repetitive rotatostimulations on lateral semicircular canals

Sixty-five guinea pigs were used to investigate the influence of rotatostimulations on the lateral crista ampullaris. After repeated turning stimulations with the cupulometric mode (the terminal turning velocity: 180 degrees/sec) for 24-72 hours, the morphological changes in the crista ampullaris on the ampullopetal flow side were compared with those on the ampullofugal flow side by using scanning and transmission electron microscopy. Postrotatory nystagmus recorded by ENG during this experiment revealed the response decline phenomenon in all animals, and the caloric test performed after the rotatostimulation showed 'canal paresis' in the ear on the ampullopetal flow side. In a group stimulated for 24 hours, no particular damage on the crista ampullaris was noticed. However, in a group stimulated for 72 hours, local damage was dominant in the central part of the crista, which showed a tendency to extend towards the planum semilunatum according to an increment of changes. These findings were more remarkable on the ampullopetal flow side than on the ampullofugal flow side, suggesting the predominant effect of the ampullopetal endolymph flow in the lateral semicircular canal.