The periventricular crossroads have been described as transient structures of the fetal brain where major systems of developing fibers intersect. The triangular parietal crossroad constitutes one major crossroad region. By combining in vivo and post-mortem fetal MRI with histological and immunohistochemical methods, we aimed to characterize these structures. Data from 529 in vivo and 66 post-mortem MRI examinations of fetal brains between gestational weeks (GW) 18-39 were retrospectively reviewed. In each fetus, the area adjacent to the trigone of the lateral ventricles at the exit of the posterior limb of the internal capsule (PLIC) was assessed with respect to signal intensity, size, and shape on T2-weighted images. In addition, by using in vivo diffusion tensor imaging (DTI), the main fiber pathways that intersect in these areas were identified. In order to explain the in vivo features of the parietal crossroads (signal intensity and developmental profile), we analyzed 23 post-mortem fetal human brains, between 16 and 42 GW of age, processed by histological and immunohistochemical methods. The parietal crossroads were triangular-shaped areas with the base in the continuity of the PLIC, adjacent to the germinal matrix and the trigone of the lateral ventricles, with the tip pointing toward the subplate. These areas appeared hyperintense to the subplate, and corresponded to a convergence zone of the developing external capsule, the PLIC, and the fronto-occipital association fibers. They were best detected between GW 25-26, and, at term, they became isointense to the adjacent structures. The immunohistochemical results showed a distinct cellular, fibrillar, and extracellular matrix arrangement in the parietal crossroads, depending on the stage of development, which influenced the MRI features. The parietal crossroads are transient, but important structures in white matter maturation and their damage may be indicative of a poor prognosis for a fetus with regard to neurological development. In addition, impairment of this region may explain the complex neurodevelopmental deficits in preterm infants with periventricular hypoxic/ischemic or inflammatory lesions.

中文翻译：

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胎儿大脑中生长皮质通路的脑室周围顶叶十字路口的发育动力学——具有组织学相关性的体内胎儿 MRI

脑室周围的十字路口被描述为胎儿大脑的瞬时结构，在那里发育的主要纤维系统相交。三角形顶叶十字路口构成了一个主要的十字路口区域。通过将体内和死后胎儿 MRI 与组织学和免疫组织化学方法相结合，我们旨在表征这些结构。对妊娠周 (GW) 18-39 之间的 529 次体内胎儿大脑和 66 次死后 MRI 检查的数据进行了回顾性审查。在每个胎儿中，在内囊后肢 (PLIC) 出口处与侧脑室三角区相邻的区域根据 T2 加权图像上的信号强度、大小和形状进行评估。此外，通过使用体内扩散张量成像 (DTI)，确定了在这些区域相交的主要纤维通路。为了解释顶叶十字路口的体内特征（信号强度和发育特征），我们分析了 23 位 16 至 42 GW 年龄的死后人类胎儿大脑，通过组织学和免疫组织化学方法处理。顶叶十字路口为三角形区域，基部与PLIC相连，邻近生发基质和侧脑室三角区，尖端指向底板。这些区域对于底板显得高信号，对应于发育中的外囊、PLIC 和额枕联合纤维的会聚区。它们最好在 GW 25-26 之间检测到，并且在术语中，它们变得与相邻结构等信号。免疫组化结果显示明显的细胞、纤维状、和细胞外基质在顶叶十字路口的排列，取决于发育阶段，这影响了 MRI 特征。顶叶十字路口是短暂的，但白质成熟中的重要结构及其损伤可能表明胎儿在神经发育方面的预后不佳。此外，该区域的损伤可以解释具有脑室周围缺氧/缺血或炎症病变的早产儿复杂的神经发育缺陷。