The vestibular system in the elderly.

Aging in the peripheral vestibular apparatus is shown to consist of processes similar to those occurring in other parts of the nervous system. Sensory epithelium and primary efferents degenerate and are not replaced. Type I hair cells and elements of the pars inferior are most susceptible. Remaining cells show a build-up of lipofuscin and microstructural changes suggesting compromised metabolism. Rupture of the saccular membrane and microfractures of the otic capsule are frequently seen. Otoconia undergo degeneration, and the tissue between the endolymphatic duct and bony vestibular aqueduct becomes fibrotic. The recognition of these findings is a first step in the clinical delineation of the "dysequilibrium of aging" from symptoms related to specific disease processes. Further clinical correlation will remain difficult until changes in the central vestibular pathways and their connections with the optic and locomotor systems are better understood.