Hong S K, Chi J G, Sim B S
Department of Neurosurgery, Seoul Red Cross Hospital.
J Korean Med Sci. 1989 Mar;4(1):35-50. doi: 10.3346/jkms.1989.4.1.35.
To elucidate the early sequential morphogenetic progress of exencephaly and myeloschisis, rat embryos whose mothers had been treated with hypervitaminosis A were studied at 1-day interval from gestation day 10.5 to 15.5. In exposed animals sequential change was found in both exencephaly and myeloschisis as the embryos grew up. The 10.5-day old exencephalic embryos had still widely open cephalic neural tubes. Exencephalic embryos older than 13.5 days of gestation showed strikingly severe eversion and overgrowth of the cephalic neuroepithelium, thus failed in forming normal primitive brain. The convex dorsal surface of the exencephaly was covered with ependyma, which was connected directly with surrounding surface eqithelium at the periphery. The earliest morphologically recognized myeloschisis was in the 13.5-day old embryos. In myeloschisis, divergence at the roof plate and eversion of the spinal neural tube, disorganized overgrowth of the neuroepithelium, malformed and misplaced spinal ganglia and nerve roots, and absence of the neural arch and dermal covering were characteristic. It is suggested that exencephaly results from failure of the cephalic neural tube closure which is followed by eversion and overgrowth of the neuroepithelium. And failure in closure of the posterior neuropore and disturbance in the development of the tail bud probably play major role in the morphogenesis of myeloschisis.
为阐明无脑儿和脊柱裂早期连续的形态发生过程，对其母亲患有维生素A过多症的大鼠胚胎从妊娠第10.5天至15.5天每隔1天进行研究。在暴露的动物中，随着胚胎的生长，无脑儿和脊柱裂均出现了连续变化。妊娠10.5天的无脑儿胚胎的头端神经管仍广泛开放。妊娠13.5天以上的无脑儿胚胎显示出头端神经上皮显著严重的外翻和过度生长，因此未能形成正常的原始脑。无脑儿的凸背表面覆盖有室管膜，其在周边直接与周围的表面上皮相连。最早在形态学上识别出的脊柱裂见于妊娠13.5天的胚胎。在脊柱裂中，顶板处的分离和脊髓神经管的外翻、神经上皮的无序过度生长、脊髓神经节和神经根的畸形和错位以及神经弓和皮肤覆盖物的缺失是其特征。提示无脑儿是由于头端神经管闭合失败，随后神经上皮外翻和过度生长所致。而后神经孔闭合失败和尾芽发育障碍可能在脊柱裂的形态发生中起主要作用。
