Age-related change in the number of neurons in the human vestibular ganglion

Dysequilibrium of aging in humans has been speculated to arise from progres sive deterioration within anatomical components of the vestibular system. A n integral part of this system is vestibular ganglions, which are bipolar n eurons that relay peripheral vestibular information to the central nervous system. To assess the effect of aging on the number of human vestibular gan glion newtons, assumption-free stereology in the form of the optical fracti onator was used on 20 serially sectioned archival human temporal bone speci mens. Donors had no history of vestibular pathology and ranged in age from 2 to 88 years. An average of 25,812 (coefficient of variation = 0.13) vesti bular ganglion neurons was found throughout this age range, a significant d eparture from the results of past studies. Logistics-based regression analy sis pointed to a nonlinear pattern of decline in the neuronal population: t he number of cells remained roughly constant at about 28,952 cells in youth and then declined gradually between 30 and 60 years of age before leveling off at approximately 23,349 cells in older individuals. This study confirm ed the existence of an age-related decline in the primary neurons of the hu man vestibular system, thus providing one anatomical basis for the increase d incidence of imbalance seen with age. J. Comp. Neurol. 431:437-443, 2001. (C) 2001 Wiley-Liss, Inc.