Central nervous system defects in early human abortuses.

Thirteen embryos with various central nervous system (cns) defects were examined macroscopically and by serial sectioning, and were compared with seven control embryos. All had been aborted spontaneously. Examples of anencephaly, anencephaly with spina bifida, spina bifida alone, encephalocele, iniencephaly and cyclops were found. Histological assessment was directed mainly to the cns, the skeletal axis, the neural-crest derivatives and remaining viscera. The cns was affected by postmortem change in some cases. Brain tissue was absent in most anencephalic embryos and spinal-cord tissue was absent at the level of the external lesion in all except one of the spina-bifida embryos. Defects such as diastematomyelia were found occasionally. Widespread abnormalities were found in the cartilaginous vertebral colun. The meninges were unusually vascular, but other neural crest derivatives appeared to be normal. The possible causes of absent brain or spinal cord are discussed and the findings are compared with the pathology of cns defects in childhood.