Review zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Am zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA J Otolayngol 10:422~29,1989 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA The Vestibular System in the Elderly: Clinical Implications PHILIPD. SLOANE, MD, MPH, ROBERT W. BALOH, MD, ANDVICENTE HONRUBIA, MD Cell loss, changes in synapse morphology, electrophysiologic alterations, and changes in the supporting microenvironment have all been noted in portions of the vestibular sys- tems of aged animals and humans. Increased variability with age is also a prominent finding in many studies. Quantitative vestibular testing in humans has shown alterations with age as well, but decline with aging is not a prominent feature of all measures, and many reported studies are methodogically flawed. The connection between these ob- served aging changes and the increased incidence of dizziness and falls in the elderly is unproven, however, and clinicians should search carefully for specific disease processes in their elderly patients who present with vestibular symptoms. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR AM J OTOLARYNGOL 10:422-429. 0 1989 by W.B. Saunders Company. Key words: vestibular system, aging, dizziness, vestibular function tests, physiology. Dizziness and dysequilibrium are common symptoms in the elderly. However, because of the overlap in function with other sensory systems, the role of vestibular system dysfunction in caus- ing these symptoms is often unclear. Over the past few decades, considerable new data on aging and the vestibular system has come to light. We re- view the reported effects of aging on the anatomy, histology, and physiology of the vestibular sys- tem, the effects of aging on common tests of ves- tibular function, and the implications of these findings on clinical observations related to vestib- ular function in the elderly. AN OVERVIEW OF THE VESTIBULAR SYSTEM The vestibular system includes the labyrinthine end organs, primary afferent neurons in Scarpa’s ganglia, and secondary neurons in the vestibular nuclei and portions of the cerebellum.l*’ Within the cerebellum, the flocculonodular lobe receives primary vestibular input and the vermis receives zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHG Received January 10, 1989, from the Department of Family Medicine of the University of North Carolina, and the Depart- ments of Neurolonv and OtolarvnaoloPv of the Universitv of California at Los Angeles. Accepted fo;publication M arch 12, 1989. Supported by NIH grant no. AG00341-03. Address correspondence and reprint requests to Philip D. Sloane, MD, MPH, Department of Family Medicine, University of North Carolina, Chapel Hill, NC, 27699. 0 1989 by W.B. Saunders Company. 0196-0709/89/1006-0006$5.00/O secondary vestibular input. Projections from sec- ondary vestibular neurons reach numerous areas of the central nervous system. Their most promi- nent influences are on eye movements (vestibulo- ocular reflexes) and on skeletal muscles in the neck, trunk, and extremities (vestibulo-spinal re- flexes). The vestibulo-ocular reflexes are medi- ated by the median longitudinal fasciculus and other pathways in the reticular substance of the brainstem. The vestibulo-spinal reflexes involve output both direct, from the vestibular nuclei, and indirect, through the cerebellum and reticular for- mation, ultimately affecting the anterior horn neu- rons in the spinal cord.3’4 The vestibular system is one of a variety of sen- sory systems used by the brain to regulate move- ment. Other mediating influences include propri- oceptive input from joints and striated muscle, and visual input from the retina. When one par- ticipating element or system is dysfunctional, the other systems accommodate. This is exemplified by central compensation for peripheral vestibular damage, by virtue of which the clinical effects of labyrinthine destruction (nystagmus, dizziness, and impaired ocular and spinal reflexes) resolve over time. STRUCTURAL AND ELECTROPHYSIOLOGIC CHANGES WITH AGING Cell Loss. The neuronal and sensory cells of the vestibular system are “ fixed postmitotics,” highly differentiated cells that cannot reproduce 422