67例无脑畸胎的中枢神经系

THE CENTRAL NERVOUS SYSTEM OF 67 ANENCEPHALIC FOETUSES

本文观察了67例(♂18,♀49)无脑畸胎的中枢神经系,根据脑部遗迹的结构将它们分为扁平亚型(32例,47.8%)及囊泡亚型(35例,52.2%)两类。无脑畸胎的脑部无颅盖,整个脑部成了脑血管组织。在颅窝前部(相当于颅中窝以前的部分)稍见隆起,内部形成颅前脑腔(扁平亚型)或囊泡(囊泡亚型),是侧脑室和第三脑室的遗迹。颅窝后部相当脑干下部。脑血管组织腹面附有第Ⅱ—Ⅻ对脑神经根。无脑畸胎都伴有部分或完全的脊柱裂,脊柱裂部的脊髓都呈髓板状,表面复有室管膜上皮,内部已分化出内、外侧细胞团,分别与脊神经的前、后根相连。对比无脑畸胎和正常胎儿的腰节2—3的切片,就见无脑畸胎脊髓发育较差,其横断面积为正常胎儿的18.09%。前角运动细胞大小及尼氏体正常,分群不如正常胎儿明显,只能分出内、外侧两群。也可见严重的血管扩张和出血。我们同意无脑是神经管未闭合的结果,羊水过多与无脑也似有密切关系。

The central nervous system of 67 anencephalic foetuses were studied both grosslyand microscopically.All anencephalic foetuses were characterized by the absence of the calvarium and brain which were replaced by the cerebro-vascular tissue.In the anterior portion of the cranial fossa was a sac,either dilated or collapsed and semilunar in form.Accordingly,the anencephalic cases could be classified into flat(32 cases or 47.8%)and saccular types(35 cases of 52.2%).The structure of the wall of the sac in both types was identical.It was composed of pallium,lined internally with a layer of ependymal epithelium.Within the cavity,the choriod plexus may be found.It is believed that this sac is thevestige of the lateral and third ventricles.Cranial nerves with the exception of the first pair were found to be attached tothe ventral surface of the cerebro-vascular tissue.All anencephalic foetuses showed either partial or complete rachischisis,the spinal cord was maintained in a primitive plate-form.This plate was composed chiefly of the gray matter whereas the white matter was very scanty,it was covered by the columnarependymal epithelium.The gray matter had already differentiated into a medial and a lateral cell group,which were connected with the anterior and posterior roots of the spinalnerves respectively.The average area of the cross sections of Lspinal segments of anencephalic foe-tuses was about 3.35 mm~2,being only 18.09%of the normal.The size and Nissl bodies of the anterior horn motor cells were apparently normal,but only 2 cell groups,medial and lateral,could be identified.Severe vasodilatation and hemorrhage were distinct.Our conclusion is in agreement with those of the previous workers,that is to say,the causation of anencephaly is due to the failure of closure of the foetal neural tube.