Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4533_Библиотеки_им_академика_М_И_Перельмана

Conjoined twins (CT) are a very rare develop­mental accident of uncertain etiology. The preva­lence has been previously estimated to be 1 in 50,000 to 1 in 400,000 births. The process by which monozygotic twins do not fully separate

South American countries. Conjoined twins rarely survive early infancy—approximately 30% dies in utero, 40–60% are stillborn, and 35% survives 1day [7, 8].

1874), Thai brothers born in Siam, now Thailand, traveled widely for many years and became famous as “The Siamese Twins” (Fig. 11.4). Chang and Eng were joined at the torso by a band of esh, cartilage, and their fused livers. In mod­ern times, they could have been easily separated. Due to the brothers’ fame and the rarity of the condition, the term “Siamese twins” came to be used as a synonym for conjoined twins.

In the craniofacial region three different sub- terms (Fig.11.5) are used as various tissues and organ fusions are seen in the head and neck region. When the skull is mainly involved, they are termed crani­opagus, whereas if the face is mainly involved they are termed cephalopagus or facial duplication (diprosopus). If the twinning is asymmetric, they are labeled parasites. There is no precise margin in between these groups. Conjoined twins are known to result from aberrant embryogenesis. Diprosopus, or partial facial duplication, is a very rare congeni­tal abnormality, even in the group of conjoined

twins. Diprosopus, a Greek term meaning duplica­tion of face, is conceptualized as a craniofacial duplication with normal trunk and limbs. The ear­liest description of diprosopus is credited to Ambroise Pare of the sixteenth century. Whereas the underlying biological basis of most craniofa­cial malformations is well understood, the etiol­ogy and pathogenesis of (conjoined) twinning like cranio- facial duplication is rare and enigmatic. This disease entity has about 35 reported cases in the literature [17–20]. It is a rare form of conjoined twins with a reported incidence of 1 case in 180,000 to 15 million births. Advanced maternal age, polyhydramnios, and consanguineous mar­riage are considered high-risk factors for diproso­pus. This extremely rare sub-form of craniofacial malformation gives insight and speculation on this disease development. Partial facial duplication may be symmetric or not and may involve the nose, the maxilla, the mandible, the palate, the tongue, and the mouth. Craniopagus parasiticus (CP) is a rare type of malformation of conjoined twins, with one degenerated or underdeveloped parasite twin united at the cranium with the other fully developed twin. Only a handful of cases have been documented in the literature to date. The inci­dence of this rare deformity is approximately 4–6 out of every 10,000,000 live births.

Boer et al. [5] (2019) rejected in an actual review paper both the fusion and the ssion theo­ries as causative explanations. The authors pro­posed that initial duplication of axially located morphogenetic potent primordia in one inner cell mass of the blastocyst (Fig.11.7) is the initiating factor in the genesis of non-dorsally conjoined twins. Moreover, they mentioned that such a mechanism seems to be responsible for separate twinning, in which they assumed that the initial reciprocal distance between the axial primordia seems to be large enough to prevent mutual developmental interference from occurring.

Diprosopus as an extremely rare form of cranio­facial malformation presents with duplication of face which may be partial or complete. There are different classications of this rare form of malformation.

In 1982, Barr [26] classied duplication into three main forms: