Wintour E M, Lewitt M, McFarlane A, Moritz K, Potocnik S, Rees S, Tangalakis K
Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, Australia.
Acta Neuropathol. 1996;91(5):537-44. doi: 10.1007/s004010050463.
Hydranencephaly is defined as the replacement of a previously normal brain, in whole or in part, by membranous fluid-filled sacs. The etiology is not well understood, and the time course of development is unknown. Fifteen ovine fetuses were chronically cannulated and had both carotid arteries ligated at 100 days of gestation (term is 145-150 days). They were killed at 1 (n = 4), 2 (n = 6) and 4 (n = 5) weeks post-surgery, and the findings compared with those of 25 age-matched controls. By 2 weeks post-surgery the entire cerebral hemispheres and diencephalon had been replaced by fluid closely resembling cerebrospinal fluid. The choroid plexus, pituitary and brain stem remained outwardly normal, but the cerebellum showed signs of damage. Fetuses maintained normal values for blood gases and hematocrit up to 4 weeks post-surgery, and grew normally. Light microscopy of the brain stem showed significant losses of cell populations in the medulla by 4 weeks. Vascular casting and acute blood flow studies in an additional group of fetuses showed that the entire brain was perfused via the vertebral-occipital anastomosis immediately after acute bilateral carotid clamping, but that the blood flow rate was insufficient to maintain adequate oxygen delivery.
积水性无脑畸形的定义是，先前正常的大脑全部或部分被充满液体的膜性囊所取代。其病因尚不清楚，发育进程也未知。15只绵羊胎儿在妊娠100天时（足月为145 - 150天）进行了长期插管，并结扎了双侧颈动脉。在术后1周（n = 4）、2周（n = 6）和4周（n = 5）将它们处死，并将结果与25只年龄匹配的对照羊的结果进行比较。术后2周时，整个大脑半球和间脑已被与脑脊液极为相似的液体所取代。脉络丛、垂体和脑干外观仍正常，但小脑出现了损伤迹象。胎儿在术后4周内血气和血细胞比容维持正常水平，且生长正常。脑干的光镜检查显示，术后4周时延髓的细胞数量显著减少。在另一组胎儿中进行的血管铸型和急性血流研究表明，急性双侧颈动脉夹闭后，整个大脑立即通过枕椎吻合支供血，但血流速度不足以维持充足的氧气供应。
