Ahdab-Barmada M, Claassen D
Department of Pathology (Neuropathology), University of Pittsburgh School of Medicine, PA.
J Neuropathol Exp Neurol. 1990 Nov;49(6):610-20. doi: 10.1097/00005072-199011000-00007.
A distinct triad of central nervous system (CNS) malformations (prosencephalic dysgenesis, occipital exencephalocele and rhombic roof dysgenesis) was present in seven cases of the Meckel-Gruber syndrome examined at autopsy. We compared our findings with those previously described. Microcephaly, sloping forehead, posterior occipital exencephalocele, cerebellar hypoplasia, Chiari malformation, hydrocephalus, polymicrogyria, arhinencephaly, holoprosencephaly and anencephaly constituted a broad spectrum of the reported CNS anomalies. Few reports contained a comprehensive description of the observed CNS malformations. In those reports, and in our cases, features of prosencephalic dysgenesis included agenesis of olfactory bulbs and tracts (arhinencephaly), hypoplasia of optic nerves and chiasm, agenesis of corpus callosum, fused thalami or complete holoprosencephaly. The occipital encephalocele has consisted of a displacement of rhombic roof elements, including caudal third ventricle, cerebellar vermis and fourth ventricle, extruded through an enlarged posterior fontanelle rather than through an occipital cranium bifidum and is thus more precisely labeled an exencephalocele. Different degrees of dysgenesis of posterior fossa structures, described by some as a variant of Dandy-Walker cyst with features of a Chiari malformation, were often associated with this occipital exencephalocele. This pattern of CNS anomalies represents a triad of malformations probably associated with defective ventral induction of the developing CNS by the prechordal mesoderm.
在尸检的7例梅克尔-格鲁伯综合征病例中，出现了独特的中枢神经系统（CNS）畸形三联征（前脑发育不全、枕部脑膨出和菱形顶发育不全）。我们将我们的发现与先前描述的结果进行了比较。小头畸形、斜坡状前额、枕部后脑膨出、小脑发育不全、 Chiari畸形、脑积水、多小脑回、无脑回畸形、全前脑畸形和无脑畸形构成了所报道的中枢神经系统异常的广泛范围。很少有报告对观察到的中枢神经系统畸形进行全面描述。在那些报告以及我们的病例中，前脑发育不全的特征包括嗅球和嗅束发育不全（无脑回畸形）、视神经和视交叉发育不全、胼胝体发育不全、丘脑融合或完全性全前脑畸形。枕部脑膨出由菱形顶结构移位组成，包括尾侧第三脑室、小脑蚓部和第四脑室，通过扩大的后囟门而非枕部颅骨裂挤出，因此更准确地称为脑膨出。后颅窝结构不同程度的发育不全，一些人将其描述为具有Chiari畸形特征的Dandy-Walker囊肿的一种变体，常与这种枕部脑膨出相关。这种中枢神经系统异常模式代表了一种畸形三联征，可能与脊索前中胚层对发育中的中枢神经系统的腹侧诱导缺陷有关。
