NEURONAL LOSS IN HUMAN MEDIAL VESTIBULAR NUCLEUS

The data concerning the effects of age on the brainstem are inconsiste nt, and few works are devoted to the human vestibular nuclear complex. The medial vestibular nucleus (MVN) is the largest nucleus of the ves tibular nuclear complex, and it seems to be related mainly to vestibul ar compensation and vestibule-ocular reflexes. Eight human brainstems have been used in this work. The specimens were embedded in paraffin, sectioned, and stained by the formaldehydethionin technique. Neuron pr ofiles were drawn with a camera lucida at x330. Abercrombie's method w as used to estimate the total number of neurons. We used the test of K olmogorov-Smirnov with the correction of Lilliefors to evaluate the fi t of our data to a normal distribution, and a regression analysis was performed to determine if the variation of our data with age was stati stically significant. The present study clearly shows that neuronal lo ss occurs with aging. The total number of neurons decreases with age, from 122,241 +/- 651 cells in a 35-year-old individual to 75,915 +/- 4 53 cells in an 89-year-old individual. Neuron loss was significant in the caudal and intermediate thirds of the nucleus, whereas the changes in the rostral third were not significant. The nuclear diameter of su rviving neurons decreased significantly with age. There is a neuron lo ss in the MVN that seems to be age-related. It could help explain why elderly people find it hard to compensate for unilateral vestibular de ficits. The preservation of neurons in the rostral third could be rela ted to the fact that this area primarily innervates the oculolmotor nu clei; these latter neurons do not decrease in number in other species studied. Anat. Rec. 251:431-438, 1998. (C) 1998 Wiley-Liss, Inc.