한국인 태아의 중추 신경계 수초화에 관한 연구

Abstract

It is often desirable to know the maturity of the fetal brains of a wide variety of gestational ages. Although myelination is known as an important process of regional maturation of the nervous system, it is still not clear whether myelination cycle is stereotypic enough to be a parameter of maturation in the fetal brains. We have studied a total of 123 brains and spinal cords of the Korean fetuses of gestational ages ranging from 12 to 44 weeks. These fetuses were products of artificial abortion. The brains and spinal cords were removed as soon as possible after delivery, and were fixed in 10% formalin. Representative blocks were taken from standardized portions of the nervous system. Through routine histological process slides were made and stained with hematoxylin-eosin and Luxol-Fast-Blue for general morphology and myelin, respectively. Tables were made to list myelination process of all the major fiber-systems by different gestational periods. The listing of a fiber-system was based on microscopically demonstrated myelin tubules in certain area in more than half of the cases. Following conclusions were made. 1. The pattern of myelination in the developing central nervous system at various gestational periods. is not strictly stereotyped. However, there is a definite trend of an orderly process in which functionally allied systems were synchronized in an orderly sequence. 2. As gestation progresses, increasing number of cells with large pale vesicular nuclei appeared in thearea to be myelinated, prior to actual deposit of the material (myelin) stainable with Luxol Fast Blue. These myelination glial cells decreased gradually in number as myelination process advanced. 3. The myelination started in the anterior and posterior nerve roots of the spinal cords at 12 to 15weeks gestational period. The fiber-system mediating the general proprioceptive experience myelinates early and rapidly at 16 to 20 weeks gestational period. followed by the fiber-system mediating vestibular and acoustic modalities in the brain stem. Theexteroceptive( tactile and pain) somatic fiber-system myelinates later and slowly. These sensory pathways showed ascending (cephalad) progression of myelination. The corticospinal tract myelination then rapidly becomes apparent in a caudal direction through the brain stem and spinal cord. 4. Stainable myelin was rarely seen in the medullary substance of the cerebral hemisphere except along the course of fiber tract of the internal capsule and optic radiation even in full term fetuses.