Calabrò F, Arcuri T, Jinkins J R
Neuroradiology Section T.M.A. Clinica Villa Salus, Genoa, Italy.
Neuroradiology. 2000 Apr;42(4):290-5. doi: 10.1007/s002340050888.
Abnormal cerebrospinal fluid (CSF) collections within the posterior fossa are defined by the Dandy-Walker complex (DWC) and by arachnoid cysts (AC). The DWC includes the Dandy-Walker malformation (DWM), the Dandy-Walker variant (DWV) and the mega-cisterna magna (MCM). In addition, Tortori-Donati et al. added persistent Blake's pouch cyst (BPC) as an independent entity within the DWC. BPC represents a posterior ballooning of the superior medullary velum into the cisterna magna. All of these malformations are overlapping developmental anomalies characterized by varying degrees of malformation of the medullary vela, the cerebellar vermis and hemispheres, the fourth ventricle choroid plexus, the posterior fossa subarachnoid cisterns and the enveloping meningeal structures. We present two cases of persistent BPC detected in two adult women without history of gestational or subsequent growth problems. They underwent neuroradiological investigation because of headache and because of recurrent episodes of loss of consciousness, respectively. The MRI findings included tetraventricular hydrocephalus, wide communication of the fourth ventricle and the cystic posterior fossa (i.e. BPC), inferior posterior fossa mass effect with or without hypoplasia of both the cerebellar vermis and the medial aspects of the cerebellar hemispheres, and absence of communication between fourth ventricle and the basal subarachnoid space in the midline posteriorly. Persistent BPC is defined by a failure of embryonic assimilation of the area membranacea anterior within the tela choroidea associated with imperforation of the foramen of Magendie. Typically this condition becomes symptomatic early in life. In the current cases the normal function of the laterally positioned foramina of Luschka probably helped to maintain some CSF flow between intraventricular and subarachnoid spaces, with the establishment of a precarious equilibrium characterized by a compensatory enlargement of the cerebral ventricular system (i.e. hydrocephalus).
后颅窝内异常脑脊液（CSF）聚集由丹迪-沃克复合体（DWC）和蛛网膜囊肿（AC）定义。DWC包括丹迪-沃克畸形（DWM）、丹迪-沃克变异型（DWV）和巨大枕大池（MCM）。此外，托尔托里-多纳蒂等人将持续存在的 Blake 囊囊肿（BPC）作为DWC中的一个独立实体。BPC表现为上髓帆向后膨出进入枕大池。所有这些畸形都是重叠的发育异常，其特征是髓帆、小脑蚓部和半球、第四脑室脉络丛、后颅窝蛛网膜下池以及包绕的脑膜结构存在不同程度的畸形。我们报告两例在两名成年女性中检测到的持续存在的BPC，她们均无妊娠或后续生长问题的病史。她们分别因头痛和反复意识丧失发作接受了神经放射学检查。MRI表现包括四脑室脑积水、第四脑室与囊性后颅窝（即BPC）广泛相通、后颅窝下部肿块效应，伴或不伴有小脑蚓部和小脑半球内侧发育不全，以及第四脑室与中线后方基底蛛网膜下腔不相通。持续存在的BPC定义为脉络丛内前膜区域胚胎期吸收失败，伴有马根迪孔未穿孔。通常这种情况在生命早期就会出现症状。在当前病例中，位于外侧的Luschka孔的正常功能可能有助于维持脑室内和蛛网膜下腔之间的一些脑脊液流动，从而建立一种不稳定的平衡，其特征是脑室系统代偿性扩大（即脑积水）。
