Age- Related Changes of Quantitative Parameters of Neurons in Extraocular Motor Nuclei

Abstract

Introduction: Extraocular motor nuclei are located in the midbrain (principal oculomotor and trochlear nucleus) and in the pons (abducens nucleus). With aging, there are significant changes in eyeball mobility. Aim of the Study: The aim was to determine whether the quantitative parameters of neurons (volume and surface density, and the absolute number per mm² of the surface) in these nuclei significantly change with aging. Patients and Methods: The study was done on 30 adult brainstems, both male and female, without diagnosed neurological disturbances. Three-millimeter-thick strata were taken in transversal plane and cut in 0.3 micrometer semi-serial sections stained with Mallory method. The images of studied nuclei were taken by 'Leica' DM 1000 microscope and 'Leica' EC3 digital camera under 400x magnification and analyzed by ImageJ software with A100 grid. The statistical analysis was performed by Statistical Package for the Social Sciences software using Pearson's correlation coefficient with 5% level of significance. Results: The volume density of neurons had highly statistically significantly increased with age in principal oculomotor nucleus (r = 0.571, p = 0.001) and trochlear nucleus (r = 0.581, p = 0.001), while abducens nucleus showed no change in neuron volume. Changes of values of surface density and absolute number of neurons per mm2 with age did not reach statistical significance. Conclusion: Volume of neurons of extraocular motor nuclei located in the midbrain increase with age, while their surfaces and absolute number do not change significantly. These changes are not observed in the nucleus located in the pons.