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Conjoined Twins
Chapter
40
Conjoined Twins David A. Staffenberg, MD, DSc (Hon), and James T. Goodrich, MD, PhD, DSc (Hon)
1. What is the incidence of conjoined twins? Conjoined twins occur as often as once in every 40,000 births but only once in every 200,000 live births. 2. What are the types of conjoined twins? •• Craniopagus: Cranial union only. Simple cases may involve only scalp and calvarium, whereas more complete cases involve scalp, calvarium, dura, venous sinuses, and brain (Fig. 40-1A ). •• Pygopagus: Posterior union of the buttocks (Fig. 40-1B ). •• Thoracopagus: Anterior union of the upper portion of the trunk. This form of conjoining is the most common type of conjoined twinning (Fig. 40-1C ). •• Cephalopagus: Anterior union of the upper half of the body with two faces on opposite sides of a conjoined head (extremely rare); the heart may be involved (Fig. 40-1D ). •• Rachipagus: Dorsal union of the trunk with fused vertebral columns (Fig. 40-1E ). •• Parapagus (sometimes called Diprosopus): Lateral union of the lower half of the body, extending variable distances upward; heart may be conjoined to varying degrees (Fig. 40-1F ). •• Ischiopagus: Union of the lower half of the body; heart is not involved, but conjoined spines are not uncommon and increase the difficulty of separation (Fig. 40-1G ). •• Omphalopagus: Anterior union of the midtrunk (Fig 40-1H ). •• Craniopagus/Thoracopagus Parasiticus Parasitic Twins: Asymmetrical conjoined twins; one twin is small and less developed. The less developed twin survives only as a parasite upon the other. •• Fetus-in-fetu: An imperfect fetus is contained completely within the body of its sibling. 3. What are the relative percentages of each type of conjoined twin? •• Craniopagus: 2% •• Pygopagus: 19% •• Thoracopagus: 35% •• Cephalopagus: Rare •• Rachipagus: Rare •• Parapagus: 5% •• Ischiopagus: 6% •• Omphalopagus: 30% •• Parasitic twins: Rare •• Fetus-in-fetu: Rare 4. What percentage of conjoined twins are the same sex? One hundred percent. All conjoined twins are identical twins who develop with a single placenta from a single fertilized ovum. Female conjoined twins appear to be about three times more common than male conjoined twins. 5. What are the embryologic issues that lead to the formation of conjoined twins? Approximately 2 weeks after fertilization, during the primitive streak stage, the embryonic axis incompletely splits. This occurs much later than the split that leads to separate monozygotic twinning. Conjoined twinning occurs exclusively in monoamniotic, monochorionic twins and, with the exception of parasitic conjoined twins, is generally symmetrical and the same parts are always united to the same parts. Although some omphalopagus twins appear to be oriented head to toe, careful examination reveals a twist where they are conjoined. 6. How did conjoined twins become known as “Siamese twins”? Conjoined twins throughout history have captivated people. They have been worshipped as gods or feared as bad omens, leading them to be abandoned, exiled, or even killed. As time passed, they were viewed as curiosities, and those who survived became sideshow acts, performed in circuses, or even became stage performers. Until the late 1800s conjoined twins were called “monsters.” The term Siamese twins comes from the twin conjoined brothers Chang and Eng Bunker who were born in Siam, now Thailand. When they first arrived in England to become circus exhibits, they were called “The Siamese Twins.” 268
CRANIOFACIAL SURGERY I—CONGENITAL
A
B
E
C
D
F
F
G
H
Figure 40-1. A, Craniopagus. B, Pygopagus. C, Thoracopagus. D, Cephalopagus. E, Rachipagus. F, Parapagus. G, Ischiopagus tripus. H, Omphalopagus. (Copyright © 2006 Medical Modeling LLC. Reproduced with permission.)
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7. Who were some of the historically noted conjoined twins? The Biddenden Maids (1100–1134 ). Eliza and Mary Chalkhurst were born in England and were known as the Biddenden Maids. When one of the parapagus twins died, the remaining twin is said to have refused an attempt at separation, saying, “As we came together, we will also go together.” The twins left 20 acres of land to the poor, and every Easter biscuits decorated with their image are given to visitors of the village. Lazarus and Joannes Baptista Colloredo (1617–1640s or 1650s). Lazarus and Joannes Baptista Colloredo are an example of parasitic twinning. Joannes grew as a parasitic appendage that grew out of Lazarus’s torso. These twins toured Europe as circus performers and become quite wealthy as a result. Chang and Eng Bunker (1811–1874). Chang and Eng Bunker are the most famous of all conjoined twins. They were born in 1811 in Siam (what is now Vietnam/Thailand). The King initially threatened them with death because they were believed to represent bad omen, but ultimately they were given permission to travel the world. They joined an English touring circus and eventually joined Barnum’s Circus. They became quite wealthy as circus performers. Chang and Eng married sisters and had 21 children between the two of them. They each ran separate farms, spending a few days on one farm before moving to the other. Chang died of pneumonia at 63 years of age; Eng refused separation and died hours later. Millie and Christine McCoy (1851–1912). The “Two-Headed Nightingale” were slaves born in North Carolina. In infancy they were separated from their family and sold. Four years later they were reunited with their mother. These rachipagus twins toured the world as a Vaudeville act, singing, dancing, and playing the piano. Income from their circus performances allowed them to buy the original property on which they were born as slaves. At the age of 61 years, Millie died of tuberculosis, and Christine died hours later. Simplico and Lucio Godina (1908–1936). These twins from the Philippines were conjoined at the back. They married twin sisters, and the foursome made a living as entertainers. After Lucio died of pneumonia, Simplico was separated but soon died of an infection. 8. What were some of the historical separations? Although surgeons have always been captivated by the exceptional challenges posed by separation, few have had the opportunity to operate on conjoined twins. Before the 1950s the indications for separation were as follows:
•• A simple conjoining without shared viscera, and the conjoining was remote from the head, heart, or pelvis. •• The children would have to survive the first few months. The first successful separation (both twins survived) on record was performed in 1689. A ligament 2.5 cm long × 12 cm wide joined the twins. In 1860 a physician separated his conjoined twin daughters, but only one survived. In 1955, Dr. Rowena Spencer separated the Duckworth twins 18 hours after delivery in an effort to save the stronger twin. In 1952–1953, Dr. Oscar Sugar separated the Brodie boys, who were craniopagus conjoined twins. One of the 14-month-old twins died 34 days after surgery. The second twin survived with a temporary hemiparesis but died at age 11 years due to complications of hydrocephalus. In 1957, Voris et al. described the long-term survival of a set of 7-month-old craniopagus twin girls with minimal parietal union and a thin sheet of bone across the plane of union. One twin reportedly survived the separation neurologically intact while the other was severely impaired. Twenty-eight years later, the neurologically impaired sister donated a kidney to her twin. In 2004, we successfully separated a set of craniopagus twins at The Children’s Hospital at Montefiore. The junction included the skull, dura, a large venous plexus, and brain. A staged technique over 10 months was designed, which allowed successful separation without cerebrospinal fluid leak, meningitis, or hydrocephalus. While twin A has no postsurgical issues, twin B developed epilepsy and left-side neglect approximately 1.5 years after surgical separation. Although advances in technology have led to more frequent attempts at separation, the discussion of medical, ethical, religious, and cultural questions continue. Parents of conjoined twins and the physicians caring for them are constantly trying to provide the best care to ensure the long-term well-being for these children.
CRANIOFACIAL SURGERY I—CONGENITAL
9. If not separated, why does the surviving twin die soon after the first dies? The dead twin loses vascular tone, and the surviving twin loses his/her blood volume into the first. 10. What is the plastic surgical technique that has allowed the most reliable separation and reconstruction of conjoined twins? Tissue expansion has revolutionized conjoined twin separation. Free tissue transfer in infants does not provide enough tissue for coverage. The key to favorable outcome is durable soft tissue coverage of each twin after separation. Each twin will have a deficit of soft tissue across the conjoined plane, and after separation vital structures must be covered with viable tissue. When dura is involved (e.g., in craniopagus twins), this requirement is obvious; if soft tissue coverage is not complete and viable, cerebrospinal fluid leak will lead to meningitis. Except for simple conjoining, conjoined twins who are to undergo separation surgery usually undergo a preliminary operation to insert tissue expanders. Another possible exception is the separation of parasitic conjoined twins in which the parasitic twin is not sufficiently developed to survive separation. In these cases, flaps using tissue from the parasitic twin can be applied to the “viable twin.” 11. Why is ethics concerning the possible separation of conjoined twins a particularly difficult issue? An ethics committee must consider each case of conjoined twins separately. The decisions that must be made are occasionally complicated by problems involving patient privacy, the treatment of shared organs, and the possibility of one twin dying to save the other. The risk of not separating the twins as well as their projected quality of life if they remain conjoined also must be taken into account. Bibliography A ird I: Conjoined twins: Further observations. Br Med J 1:1313–1315, 1959. Aird I, Hamilton WJ, Wijthoff JPS, LordJM: The surgery of conjoined twins. Proc R Soc Med 47:681–688, 1954. Cameron DE, Reitz BA, Carson BS, et al: Separation of craniopagus Siamese twins using cardiopulmonary bypass and hypothermic circulatory arrest. J Thorac Cardiovasc Surg 98:961–967, 1989. Cameron HC: A craniopagus. Lancet 1:284–285, 1928. Drummond G, Scott P, Mackay D, Lipschitz R: Separation of the Baragwanath craniopagus twins. Br J Plast Surg 44:49–52, 1991. Gaist G, Piazza G, Galassi E, et al: Craniopagus twins: an unsuccessful separation and a clinical review of the entity. Childs Nerv Syst 3:327–333, 1987. Goodrich JT, Staffenberg DA: Craniopagus twins: Clinical and surgical management. Childs Nerv Syst 20:618–624, 2004. Grossman HJ, Sugar O, Greeley PW, Sadove MS: Surgical separation in craniopagus. JAMA 153:201–207, 1953. Hoyles RM: Surgical separation of conjoined twins. Surg Gynecol Obstet 170: 549–561, 1990. O’Connell JEA: Craniopagus twins: Surgical anatomy and embryology and their implications. J Neurol Neurosurg Psychiatr 39:1–22, 1976. O’Neill JA Jr, Holcomb GWIII, Schnaufer L, et al: Surgical experience with 13 conjoined twins. Ann Surg 208:299–312, 1988. Raffensperger J: A philosophical approach to conjoined twins. Pediatr Surg 12:249–255, 1997. Roberts TS: Cranial venous abnormalities in craniopagus twins. In Kapp JP, Schmidek HH (eds): The Cerebral Venous System and its Disorders. Orlando, FL, Grune & Stratton, 1984, pp 355–371. Spencer R: Conjoined twins: Developmental Malformations and Clinical Implications. Baltimore, The Johns Hopkins University Press, 2003, pp 293–311. Staffenberg DA, Goodrich JT: Separation of craniopagus conjoined twins: An evolution in thought. Clin Plast Surg 32:25–34, 2005. Todorov AB, Cohen KI, Spilotro V, Landau E: Craniopagus twins. J Neurol Neurosurg Psychiatr 37:1291–1298, 1974. Voris HC, Slaughter WB, Christian JR, Cayia ER: Successful separation of craniopagus twins. J Neurosurg 14:548–560, 1957. Winston KR, Rockoff MA, Mulliken JB, et al: Surgical division of craniopagi. Neurosurgery 21:782–791, 1987. Wolfowitz J, Kerr EM, Levin SE, et al: Separation of craniopagus. S Afr Med J 42:412–424, 1968. Wong KC, Ohmura A, Roberts TH, et al: Anesthetic management for separation of craniopagus twins. Anesth Analg 59:883–886, 1980. Wu J, Staffenberg DA, Mulliken JB, Shanske AL: Diprosopus: A unique case and review of the literature. Teratology 66:282–287, 2002. Zubowicz VN, Ricketts R: Use of skin expanders in separation of conjoined twins. Ann Plast Surg 20:272–276, 1988.
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Conjoined Twins David A. Staffenberg, MD, DSc (Hon), and James T. Goodrich, MD, PhD, DSc (Hon)
1. What is the incidence of conjoined twins? Conjoined twins occur as often as once in every 40,000 births but only once in every 200,000 live births. 2. What are the types of conjoined twins? •• Craniopagus: Cranial union only. Simple cases may involve only scalp and calvarium, whereas more complete cases involve scalp, calvarium, dura, venous sinuses, and brain (Fig. 40-1A ). •• Pygopagus: Posterior union of the buttocks (Fig. 40-1B ). •• Thoracopagus: Anterior union of the upper portion of the trunk. This form of conjoining is the most common type of conjoined twinning (Fig. 40-1C ). •• Cephalopagus: Anterior union of the upper half of the body with two faces on opposite sides of a conjoined head (extremely rare); the heart may be involved (Fig. 40-1D ). •• Rachipagus: Dorsal union of the trunk with fused vertebral columns (Fig. 40-1E ). •• Parapagus (sometimes called Diprosopus): Lateral union of the lower half of the body, extending variable distances upward; heart may be conjoined to varying degrees (Fig. 40-1F ). •• Ischiopagus: Union of the lower half of the body; heart is not involved, but conjoined spines are not uncommon and increase the difficulty of separation (Fig. 40-1G ). •• Omphalopagus: Anterior union of the midtrunk (Fig 40-1H ). •• Craniopagus/Thoracopagus Parasiticus Parasitic Twins: Asymmetrical conjoined twins; one twin is small and less developed. The less developed twin survives only as a parasite upon the other. •• Fetus-in-fetu: An imperfect fetus is contained completely within the body of its sibling. 3. What are the relative percentages of each type of conjoined twin? •• Craniopagus: 2% •• Pygopagus: 19% •• Thoracopagus: 35% •• Cephalopagus: Rare •• Rachipagus: Rare •• Parapagus: 5% •• Ischiopagus: 6% •• Omphalopagus: 30% •• Parasitic twins: Rare •• Fetus-in-fetu: Rare 4. What percentage of conjoined twins are the same sex? One hundred percent. All conjoined twins are identical twins who develop with a single placenta from a single fertilized ovum. Female conjoined twins appear to be about three times more common than male conjoined twins. 5. What are the embryologic issues that lead to the formation of conjoined twins? Approximately 2 weeks after fertilization, during the primitive streak stage, the embryonic axis incompletely splits. This occurs much later than the split that leads to separate monozygotic twinning. Conjoined twinning occurs exclusively in monoamniotic, monochorionic twins and, with the exception of parasitic conjoined twins, is generally symmetrical and the same parts are always united to the same parts. Although some omphalopagus twins appear to be oriented head to toe, careful examination reveals a twist where they are conjoined. 6. How did conjoined twins become known as “Siamese twins”? Conjoined twins throughout history have captivated people. They have been worshipped as gods or feared as bad omens, leading them to be abandoned, exiled, or even killed. As time passed, they were viewed as curiosities, and those who survived became sideshow acts, performed in circuses, or even became stage performers. Until the late 1800s conjoined twins were called “monsters.” The term Siamese twins comes from the twin conjoined brothers Chang and Eng Bunker who were born in Siam, now Thailand. When they first arrived in England to become circus exhibits, they were called “The Siamese Twins.” 268
CRANIOFACIAL SURGERY I—CONGENITAL
A
B
E
C
D
F
F
G
H
Figure 40-1. A, Craniopagus. B, Pygopagus. C, Thoracopagus. D, Cephalopagus. E, Rachipagus. F, Parapagus. G, Ischiopagus tripus. H, Omphalopagus. (Copyright © 2006 Medical Modeling LLC. Reproduced with permission.)
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Conjoined Twins
7. Who were some of the historically noted conjoined twins? The Biddenden Maids (1100–1134 ). Eliza and Mary Chalkhurst were born in England and were known as the Biddenden Maids. When one of the parapagus twins died, the remaining twin is said to have refused an attempt at separation, saying, “As we came together, we will also go together.” The twins left 20 acres of land to the poor, and every Easter biscuits decorated with their image are given to visitors of the village. Lazarus and Joannes Baptista Colloredo (1617–1640s or 1650s). Lazarus and Joannes Baptista Colloredo are an example of parasitic twinning. Joannes grew as a parasitic appendage that grew out of Lazarus’s torso. These twins toured Europe as circus performers and become quite wealthy as a result. Chang and Eng Bunker (1811–1874). Chang and Eng Bunker are the most famous of all conjoined twins. They were born in 1811 in Siam (what is now Vietnam/Thailand). The King initially threatened them with death because they were believed to represent bad omen, but ultimately they were given permission to travel the world. They joined an English touring circus and eventually joined Barnum’s Circus. They became quite wealthy as circus performers. Chang and Eng married sisters and had 21 children between the two of them. They each ran separate farms, spending a few days on one farm before moving to the other. Chang died of pneumonia at 63 years of age; Eng refused separation and died hours later. Millie and Christine McCoy (1851–1912). The “Two-Headed Nightingale” were slaves born in North Carolina. In infancy they were separated from their family and sold. Four years later they were reunited with their mother. These rachipagus twins toured the world as a Vaudeville act, singing, dancing, and playing the piano. Income from their circus performances allowed them to buy the original property on which they were born as slaves. At the age of 61 years, Millie died of tuberculosis, and Christine died hours later. Simplico and Lucio Godina (1908–1936). These twins from the Philippines were conjoined at the back. They married twin sisters, and the foursome made a living as entertainers. After Lucio died of pneumonia, Simplico was separated but soon died of an infection. 8. What were some of the historical separations? Although surgeons have always been captivated by the exceptional challenges posed by separation, few have had the opportunity to operate on conjoined twins. Before the 1950s the indications for separation were as follows:
•• A simple conjoining without shared viscera, and the conjoining was remote from the head, heart, or pelvis. •• The children would have to survive the first few months. The first successful separation (both twins survived) on record was performed in 1689. A ligament 2.5 cm long × 12 cm wide joined the twins. In 1860 a physician separated his conjoined twin daughters, but only one survived. In 1955, Dr. Rowena Spencer separated the Duckworth twins 18 hours after delivery in an effort to save the stronger twin. In 1952–1953, Dr. Oscar Sugar separated the Brodie boys, who were craniopagus conjoined twins. One of the 14-month-old twins died 34 days after surgery. The second twin survived with a temporary hemiparesis but died at age 11 years due to complications of hydrocephalus. In 1957, Voris et al. described the long-term survival of a set of 7-month-old craniopagus twin girls with minimal parietal union and a thin sheet of bone across the plane of union. One twin reportedly survived the separation neurologically intact while the other was severely impaired. Twenty-eight years later, the neurologically impaired sister donated a kidney to her twin. In 2004, we successfully separated a set of craniopagus twins at The Children’s Hospital at Montefiore. The junction included the skull, dura, a large venous plexus, and brain. A staged technique over 10 months was designed, which allowed successful separation without cerebrospinal fluid leak, meningitis, or hydrocephalus. While twin A has no postsurgical issues, twin B developed epilepsy and left-side neglect approximately 1.5 years after surgical separation. Although advances in technology have led to more frequent attempts at separation, the discussion of medical, ethical, religious, and cultural questions continue. Parents of conjoined twins and the physicians caring for them are constantly trying to provide the best care to ensure the long-term well-being for these children.
CRANIOFACIAL SURGERY I—CONGENITAL
9. If not separated, why does the surviving twin die soon after the first dies? The dead twin loses vascular tone, and the surviving twin loses his/her blood volume into the first. 10. What is the plastic surgical technique that has allowed the most reliable separation and reconstruction of conjoined twins? Tissue expansion has revolutionized conjoined twin separation. Free tissue transfer in infants does not provide enough tissue for coverage. The key to favorable outcome is durable soft tissue coverage of each twin after separation. Each twin will have a deficit of soft tissue across the conjoined plane, and after separation vital structures must be covered with viable tissue. When dura is involved (e.g., in craniopagus twins), this requirement is obvious; if soft tissue coverage is not complete and viable, cerebrospinal fluid leak will lead to meningitis. Except for simple conjoining, conjoined twins who are to undergo separation surgery usually undergo a preliminary operation to insert tissue expanders. Another possible exception is the separation of parasitic conjoined twins in which the parasitic twin is not sufficiently developed to survive separation. In these cases, flaps using tissue from the parasitic twin can be applied to the “viable twin.” 11. Why is ethics concerning the possible separation of conjoined twins a particularly difficult issue? An ethics committee must consider each case of conjoined twins separately. The decisions that must be made are occasionally complicated by problems involving patient privacy, the treatment of shared organs, and the possibility of one twin dying to save the other. The risk of not separating the twins as well as their projected quality of life if they remain conjoined also must be taken into account. Bibliography A ird I: Conjoined twins: Further observations. Br Med J 1:1313–1315, 1959. Aird I, Hamilton WJ, Wijthoff JPS, LordJM: The surgery of conjoined twins. Proc R Soc Med 47:681–688, 1954. Cameron DE, Reitz BA, Carson BS, et al: Separation of craniopagus Siamese twins using cardiopulmonary bypass and hypothermic circulatory arrest. J Thorac Cardiovasc Surg 98:961–967, 1989. Cameron HC: A craniopagus. Lancet 1:284–285, 1928. Drummond G, Scott P, Mackay D, Lipschitz R: Separation of the Baragwanath craniopagus twins. Br J Plast Surg 44:49–52, 1991. Gaist G, Piazza G, Galassi E, et al: Craniopagus twins: an unsuccessful separation and a clinical review of the entity. Childs Nerv Syst 3:327–333, 1987. Goodrich JT, Staffenberg DA: Craniopagus twins: Clinical and surgical management. Childs Nerv Syst 20:618–624, 2004. Grossman HJ, Sugar O, Greeley PW, Sadove MS: Surgical separation in craniopagus. JAMA 153:201–207, 1953. Hoyles RM: Surgical separation of conjoined twins. Surg Gynecol Obstet 170: 549–561, 1990. O’Connell JEA: Craniopagus twins: Surgical anatomy and embryology and their implications. J Neurol Neurosurg Psychiatr 39:1–22, 1976. O’Neill JA Jr, Holcomb GWIII, Schnaufer L, et al: Surgical experience with 13 conjoined twins. Ann Surg 208:299–312, 1988. Raffensperger J: A philosophical approach to conjoined twins. Pediatr Surg 12:249–255, 1997. Roberts TS: Cranial venous abnormalities in craniopagus twins. In Kapp JP, Schmidek HH (eds): The Cerebral Venous System and its Disorders. Orlando, FL, Grune & Stratton, 1984, pp 355–371. Spencer R: Conjoined twins: Developmental Malformations and Clinical Implications. Baltimore, The Johns Hopkins University Press, 2003, pp 293–311. Staffenberg DA, Goodrich JT: Separation of craniopagus conjoined twins: An evolution in thought. Clin Plast Surg 32:25–34, 2005. Todorov AB, Cohen KI, Spilotro V, Landau E: Craniopagus twins. J Neurol Neurosurg Psychiatr 37:1291–1298, 1974. Voris HC, Slaughter WB, Christian JR, Cayia ER: Successful separation of craniopagus twins. J Neurosurg 14:548–560, 1957. Winston KR, Rockoff MA, Mulliken JB, et al: Surgical division of craniopagi. Neurosurgery 21:782–791, 1987. Wolfowitz J, Kerr EM, Levin SE, et al: Separation of craniopagus. S Afr Med J 42:412–424, 1968. Wong KC, Ohmura A, Roberts TH, et al: Anesthetic management for separation of craniopagus twins. Anesth Analg 59:883–886, 1980. Wu J, Staffenberg DA, Mulliken JB, Shanske AL: Diprosopus: A unique case and review of the literature. Teratology 66:282–287, 2002. Zubowicz VN, Ricketts R: Use of skin expanders in separation of conjoined twins. Ann Plast Surg 20:272–276, 1988.
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