Vascular system of the human spinal cord in the prenatal period: a dye injection and corrosion casting study

The vascularization of the spinal cord was investigated in 50 human fetuses aged from 10 to 28 gestational weeks using dye injection methods and corro sion casting accompanied by scanning electron microscopy. In the investigat ed period of fetal development, the general vascular architecture of the sp inal cord, corresponding to that described postnatally, seemed to be alread y established. The observed changes included: (1) remodeling of the supplyi ng (extrinsic) arterial branches, (2) transformation of the posterior anast omotic chain into two distinct posterior spinal arteries, and (3) developme nt of the capillary networks in the gray and white matter. The remodeling of the radicular arteries supplying the spinal cord was acco mpanied by a decrease in their number and transition from regular to irregu lar distribution (appearance of intersegmental differences in their frequen cy). The anterior spinal artery and regular array of the central arteries w ere already present in the youngest fetuses examined, but the final remodel ing of the posterior anastomotic chain into two posterior spinal arteries o ccurred between 15th and 20th week of fetal life indicating that the vascul arization of the anterior region of the spinal cord in the investigated per iod of fetal life was more advanced as compared with that of the posterior region. The capillary network of the gray matter in the youngest fetuses ha d the form of discrete glomerular plexuses supplied by groups of central ar teries and mainly vascularizing the anterior horns. Successively, the plexu ses fused to form a continuous system along the anterior columns and the sy stem expanded to fully vascularize the posterior horns. The white matter in the earlier fetal period seemed to be partially avascular, later the densi ty of capillaries vascularizing those areas was still much lower than in th e gray matter. The veins showed considerably greater variability than the arteries, as far as their topography and distribution was concerned. High tortuosity charac terized the superficial veins, especially in the younger fetuses, although the degree of tortuosity differed even between individual fetuses. Only ant erior spinal and central arteries were usually accompanied by their venous counterparts, the other veins seemed to have no regular topographical relat ions with the arteries.