Grassi Roberto, Esposito Vincenzo, Scaglione Mariano, Cirillo Mario, Cappabianca Salvatore, Guglielmi Giuseppe, Sasso Francesco Silvano, Rotondo Antonio
Department of Clinical and Experimental Surgery, Seconda Università, Piazza Miraglia, 80100, Naples, Italy.
Radiographics. 2004 Sep-Oct;24(5):e21. doi: 10.1148/rg.e21. Epub 2004 Jul 12.
Conjoined twins can be classified on the basis of the site of union; thus, three main types can be described: (a) ventral union, (b) dorsal union, and (c) rarer forms of union. Ventral union is characterized by the fusion of the two embryos on the ventral side (eg, the abdomen). Dorsal union twins are joined on the dorsal aspect (eg, the vertebral column or occipital bone). Ventral union twins include the group of crucipage twins (ventral midline structures at 90 degrees to the dorsal midline structures), which show interesting features in the organization of the midline. Twins conjoined at the head and chest are called cephalothoracopagus twins. The cephalothoracopagus variety called "Janus" is characterized by the presence of two opposite faces, which are composite structures half of which belong to one twin and half to the other. A complete set of five variants of cephalothoracopagus is presented and, to the authors' knowledge, analyzed for the first time with multi-detector row helical computed tomography. This modality is an invaluable tool for obtaining high-resolution images of the brain, chest, abdomen, and spine and for demonstrating organ position, shared viscera, and limited vascular anatomy. In addition, data acquired in three-dimensional volumes can further be manipulated and then reconstructed. For this purpose, the authors developed dedicated software for three-dimensional reconstruction to analyze data from specimens preserved in formalin. The anatomic findings are discussed here for their embryologic value and to revise the classification of cephalothoracopagus twins. These data offer detailed information for accurate comprehension of imaging studies and for theoretical studies concerning the formation of several anatomic structures.
联体双胎可根据联体部位进行分类；因此，可以描述出三种主要类型：(a) 腹侧联体，(b) 背侧联体，以及 (c) 较罕见的联体形式。腹侧联体的特征是两个胚胎在腹侧（如腹部）融合。背侧联体双胎在背侧（如脊柱或枕骨）相连。腹侧联体双胎包括十字交叉联体双胎组（腹侧中线结构与背侧中线结构呈90度角），其在中线结构的组织方面呈现出有趣的特征。头部和胸部相连的双胎称为头胸联体双胎。名为“雅努斯”的头胸联体双胎变种的特征是有两张相对的脸，它们是复合结构，其中一半属于一个双胎，另一半属于另一个双胎。本文首次展示了一套完整的五种头胸联体双胎变体，并使用多排螺旋计算机断层扫描进行了分析。这种检查方式是获取大脑、胸部、腹部和脊柱高分辨率图像以及显示器官位置、共享脏器和有限血管解剖结构的宝贵工具。此外，从三维容积中获取的数据可以进一步处理并重建。为此，作者开发了专门的三维重建软件来分析福尔马林固定标本的数据。本文讨论了这些解剖学发现的胚胎学价值，并对头胸联体双胎的分类进行了修订。这些数据为准确理解影像学研究以及有关几种解剖结构形成的理论研究提供了详细信息。
