CRANIAL BASE AND VERTEBRAL COLUMN IN HUMAN ANENCEPHALIC FETUSES

The purpose of the present study was to investigate the axial skeleton related to the notochord in human anencephalic fetuses in order to el ucidate the pathogenesis. Fifteen second trimester fetuses were examin ed. The spine and the cranial base were dissected and radiographed. Co mparison with normal fetuses was performed. Two patterns of abnormal o ssification were seen. Anencephalic cases without cervical rachischisi s (Groups I and II) differed markedly from cases with cervical rachisc hisis (Group III). Morphological characteristics, such as bilateral na rrowing of the basilar part of the occipital bone combined with normal cranio-caudal dimension, were found in cases without cervical rachisc hisis. In these cases frontal clefting of vertebral corpora occurred. Caudocranial shortening of the basilar part of the occipital bone was found in cases with cervical rachischisis, where complete median cleft ing of vertebral corpora also occurred. Because the vertebral corpora and the basilar part of the occipital bone develop around the notochor d, which interacts also in the process of neurulation, the defects mig ht indicate a notochordal insufficiency. The study showed that when th e initial closure of the neural groove failed, the skeletal deviations were more extensive. The study supports the hypothesis that the notoc hord is an important clue to an understanding of the pathogenesis in a nencephaly.