Cochlear and vestibular functions of the rat after obliteration of the endolymphatic sac

A combined morphological and physiological study on the effect of saccus obliteration on the cochlea and the vestibular labyrinth of the rat is presented. Endolymphatic hydrops was successfully induced in 49% of the animals. It was frequently associated with fistulae of the membranous wall and degenerative changes in the organ of Corti and spiral ganglion. In hydropic ears electrocochleography revealed a CAP threshold increase only in those cases where hydrops was associated with loss of hair cells and ganglion cells. In two of these animals also an increased negative SP was present. Static otolith reflexes were found to be normal in all hydropic ears despite severe lesions of the saccule in some of these. Abnormal canal reflexes measured by electronystagmography and cupulometry were established in animals with hydrops of the semicircular canals and in one animal with a fistula of the saccule.