Morphometric analyses and aging process of nerve fibers in the human spinal posterior funiculus

The aim of the present study is to evaluate the size and number of axons in the human spinal cord nerve fibers according to the aging process, and, after conducting morphometry of histology preparations at different ages, to show some of the effects of aging on those fibers. We examined thirty-eight human spinal cords which had been taken from cadaver specimens (25 males and 13 females) aged from 41 to 97 years. The spinal segments were embedded in celloidin and sections were stained with Luxol fast blue-periodic acid-Schiff-hematoxylin (LPH). Highly enlarged images with a square eyepiece grid and oil-immersion lens were used to count the myelinated axons and to measure the axon transverse area in a unit area of the posterior funiculus at C6 level, with the help of a microscope equipped with a drawing tube, an electronic optical planimeter and a computer. Significant age-related linear decreases were found for all parameters. Our report may provide new information concerning the aging process of the human spinal cord. It revealed that a decrease in size and number of axons were one of the important changes occurring with the aging process in the human spinal posterior funiculus.