MORPHOMETRIC ANALYSIS OF THE HUMAN VESTIBULAR NUCLEI

Background: Cytoarchitectural investigations of the vestibular nuclei have been undertaken in different species of mammals. These data provi de a description of the general architecture of the nuclei but limited information about quantitative characteristics of their cell populati on. We have recently obtained data about the morphometric parameters o f the vestibular nuclei neurons in some species. The application of qu antitative image analysis techniques to the research of the cellular m orphology in the vestibular area of humans might provide basic informa tion to compare with data from animal studies, taking into account the observed correlation between physiological and morphological properti es of vestibular neurons. Methods: The characteristics of the major ve stibular nuclei in humans have been studied with light microscopic tec hniques in serially cut sections. Camera lucida drawings of the vestib ular nuclei and their neurons were made and subjected to computerized image analysis. For each vestibular nucleus, information was obtained about topography, morphological characteristics (i.e., location, volum e, and length), and the number and morphometric parameters of their ne urons (cross-sectional areas, maximum and minimum diameters). Morphome tric data about cell parameters were statistically analyzed by compari ng the populations within different parts of each nucleus and from dif ferent nuclei. Results: Among the vestibular nuclei, the medial, which is the largest, has the greatest number of neurons, and the interstit ial, the least. The lateral and interstitial nuclei contain the larges t cells, and the descending nucleus has the smallest cells. The superi or nucleus contains cells of intermediate size. The size of cells decr eases in a rostrocaudal direction in the medial, lateral, and descendi ng nuclei, the opposite trend being observed in the superior nucleus. Within the superior and medial nuclei, there are discrete areas with c ells with distinctive characteristics. Conclusions: These results sugg est that, just as most of the anatomical characteristics of the second -order neurons found in animals have been preserved in humans, so the physiological mechanisms observed in the vestibular system of animals should apply to humans. (C) 1997 Wiley-Liss, Inc.