[The effect of a parietal meningoencephalocele on the morphogenesis of the neuroepithelium of the human brain].

Meningoencephalic hernia was studied in human embryo at the 5th week (stage 15) of the development. The analysis of parietal hernia showed that the anomalous development of cerebral tissue was related with disturbed shape-forming processes in the nerve tube. The medullar toruli were not closed at the stage of nerve plate to form a free edge of neuroepithelial layer. Its relaxation resulted in a spontaneous foldness and an enhanced proliferation of neuroepithelial cells. The proliferative activity induced hyperplasia of the layer end zones a disproportionately rapid growth of the brain disturbed the integrity of cephalic ectoderm and elicited formation of external cerebral hernias. It was suggested that disturbances of tangential mechanical tensions which control the proliferative activity in the neuroepithelium underlie the overgrowth of nervous tissue.