Animal models of inner ear vascular disturbances.

Animal models of vascular disorders are identified or developed for the evaluation of functional deficits and morphologic alterations. This information will serve a useful purpose for a better understanding of sudden deafness, Meniere's disease, and presbycusis. The study of microcirculation of the inner ear vessels reveals that their responses to various stimuli, such as anoxia, sympathetic nerve stimulation, hypothermia, and drugs, are different from those of the middle ear vessels. In sudden occlusion of the major vascular supply to the inner ear, the cochlea is found to be more vulnerable than the vestibular labyrinth; outer and inner hair cells and stria vascularis are most often affected. Animal models for Meniere's disease are also described, and the importance of vascularity at the endolymphatic duct and sac is discussed from an etiologic viewpoint. In presbycusis, animal models show sensory cell and spiral ganglion cell atrophies in different locations than in human cochleas, and the relationship between these atrophies and vascular impairments is not clear at the present time.