DIFFERENCES IN ORIGIN AND FATE BETWEEN THE CRANIAL AND CAUDAL SPINAL-CORD DURING NORMAL AND DISTURBED HUMAN-DEVELOPMENT

Differences in histological appearance between the cranial and caudal parts of the spinal cord and associated axial organs were analyzed in 9- and 15-week-old human dysraphic fetuses and compared with normal fe tuses. In human development the cranial part of the neural tube down t o the lumbosacral level forms during primary neurulation, while its ca udal part results from secondary neurulation. In the 9-week fetus with cervical spina bifida, the cranial spinal cord displayed a variety of morphological changes along the cranio-caudal axis. Spinal cord in th e upper cervical region transformed into the area cerebrovasculosa, wh ile the lower cervical and thoracic levels showed only disturbed diffe rentiation of the cell layers and roof plate. The degree of the crania l spinal cord dysmorphogenesis correlated with anomalies of the underl ying notochord and vertebral column. The caudal to lumbosacral region of the spinal cord appeared normal. In the case of the 15-week-old fet us with complete dysraphia, the area cerebrovasculosa was found along the whole extent of the cranial spinal cord, while more caudally, all axial organs showed a normal histological structure. Our findings conf irmed a different origin for the cranial and caudal parts of the human spinal cord. The appearance of dysraphic disorders corresponded to th e time of primary neurulation; therefore, they resulted in the faulty formation of the cranial spinal cord. Normally formed caudal spinal co rd appears during secondary neurulation at later developmental stages.