Conjoined twins

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"Siamese twins" redirects here. For other uses, see Siamese twins (disambiguation).
Conjoined twins
Classification and external resources
A painting of Chang and Eng Bunker, circa 1836
ICD-10 Q89.4
ICD-9 759.4
DiseasesDB 34474
eMedicine ped/2936 
MeSH D014428

Conjoined twins are identical twinshttp://en.wikipedia.org/wiki/Twin#f2f1ffcal_twins whose bodies are joined in utero. It is a rare phenomenon; it is estimated to range from 1 in 50,000 births to 1 in 200,000 births, with a somewhat higher incidence in Southwest Asia and Africa.[1] Approximately half are stillborn, and a smaller fraction of pairs born alive have abnormalities incompatible with life. The overall survival rate for conjoined twins is approximately 25%.[2]

Approximately 75% of conjoined twin pairs are female.[3]

Two contradicting theories exist to explain the origins of conjoined twins. The older and most generally accepted theory is fission, in which the fertilized egg splits partially. The second theory is fusion, in which a fertilized egg completely separates, but stem cells (which search for similar cells) find like-stem cells on the other twin and fuse the twins together.

Perhaps the most famous pair of conjoined twins was Chang and Eng Bunker (1811–1874), Chinese brothers born in Siam, now Thailand. They traveled with P.T. Barnum's circus for many years and were billed as the Siamese Twins; due to their fame and the rarity of the condition, the term came to be used as a synonym for conjoined twins, although in recent years the term has fallen out of favor and is considered a pejorative term.[4] Chang and Eng were joined by a band of flesh, cartilage, and their fused livers at the torso. In modern times, they could have been easily separated.[5]

Contents

[edit] Conjoined twins in history

Conjoined twin sisters from the Nuremberg Chronicle (1493).
Conjoined twin sisters from the Nuremberg Chronicle (1493).
Moche ceramics depicting conjoined twins. AD 300 Larco Museum Collection Lima, Peru.
Moche ceramics depicting conjoined twins. AD 300 Larco Museum Collection Lima, Peru.

The earliest known documented case of conjoined twins dates from the year 945, when a pair of conjoined twin brothers from Armenia were brought to Constantinople for medical evaluation. It was here that they were determined to be acts of God and the birth of conjoined twins was considered a proof that the male's sexual prowess was truly twice that of the average man. However, the Moche culture of ancient Peru depicted conjoined twins in their ceramics dating back to AD 300.[6] The English twin sisters Mary and Eliza Chulkhurst, who were conjoined at the back (pygopagus), lived from 1100 to 1134 and were perhaps the best-known early example of conjoined twins. Other early conjoined twins to attain notice were the "Scottish brothers", allegedly of the dicephalus type, essentially two heads sharing the same body (1460–1488, although the dates vary); the pygopagus Helen and Judith of Szőny, Hungary (1701–1723), who enjoyed a brief career in music before being sent to live in a convent; and Rita and Cristina of Parodi of Sardinia, born in 1829. Rita and Cristina were dicephalus tetrabrachius (one body with four arms) twins and although they died at only eight months of age, they gained much attention as a curiosity when their parents exhibited them in Paris.

Grave of Eng and Chang Bunker near Mt. Airy, North Carolina
Grave of Eng and Chang Bunker near Mt. Airy, North Carolina

Several sets of conjoined twins lived during the nineteenth century and made careers for themselves in the performing arts, though none achieved quite the same level of fame and fortune as Chang and Eng. Most notably, Millie and Christine McCoy (or McKoy), pygopagus twins, were born into slavery in North Carolina in 1851. They were sold to a showman, J.P. Smith, at birth, but were soon kidnapped by a rival showman. The kidnapper fled to England but was thwarted because England had already banned slavery. Smith traveled to England to collect the girls and brought with him their mother, Monimia, from whom they had been separated. He and his wife provided the twins with an education and taught them to speak five languages, play music, and sing. For the rest of the century the twins enjoyed a successful career as "The Two-Headed Nightingale" and appeared with the Barnum Circus. In 1912 they died of tuberculosis, 17 hours apart.

Giovanni and Giacomo Tocci, from Locana, Italy, were immortalized in Mark Twain's short story "Those Extraordinary Twins" as fictitious twins Angelo and Luigi. The Toccis, born in 1877, were dicephalus tetrabrachius twins, having one body with two legs, two heads, and four arms. From birth they were forced by their parents to perform and never learned to walk, as each twin controlled one leg (in modern times physical therapy allows twins like the Toccis to learn to walk on their own). They are said to have disliked show business. In 1886, after touring the United States, the twins returned to Europe with their family, where they fell very ill. They are believed to have died around this time, though some sources claim they survived until 1940, living in seclusion in Italy.

The life of Abd Manaf ibn Qusai includes a legend that he separated his conjoined sons with a sword.

Conjoined twins who appeared in the public eye during the 20th and 21st centuries include:

[edit] Types of conjoined twins

Conjoined twins are typically classified by the point at which their bodies are joined. The most common types of conjoined twins are:

  • Thoraco-omphalopagus (28% of cases)[8]: Two bodies fused from the upper chest to the lower chest. These twins usually share a heart, and may also share their liver or digestive system.[9]
  • Thoracopagus (18.5%)[8]: Two bodies fused from the upper thorax to lower belly. The heart is always involved in these cases.[9]
  • Omphalopagus (10%)[8]: Two bodies fused at the lower chest. Unlike thoracopagus, the heart is never involved in these cases; however, the twins often share a liver, digestive system, diaphragm and other organs.[9]
  • Parasitic twins (10%)[8]: Twins that are asymmetrically conjoined, resulting in one twin that is small, less formed, and dependent on the larger twin for survival.
  • Craniopagus (6%)[8]: Fused skulls, but separate bodies. These twins can be conjoined at the back of the head, the front of the head, or the side of the head, but not on the face or the base of the skull.[9]

Other less-common types of conjoined twins include:

  • Cephalopagus: Two faces on opposite sides of a single, conjoined head; the upper portion of the body is fused while the bottom portions are separate. These twins generally cannot survive due to severe malformations of the brain. Also known as janiceps (after the two-faced god Janus) or syncephalus.[9]
  • Synecephalus: One head with a single face but four ears, and two bodies.[9]
  • Cephalothoracopagus: Bodies fused in the head and thorax. In this type of twins, there are two faces facing in opposite directions, or sometimes a single face and an enlarged skull. [9][1]
  • Xiphopagous: Two bodies fused in the xiphoid cartilage, which is approximately from the navel to the lower breastbone. These twins almost never share any vital organs, with the exception of the liver.[9] A famous example is Chang and Eng Bunker.
  • Ischiopagus: Fused lower half of the two bodies, with spines conjoined end-to-end at a 180° angle. These twins have four arms; two, three or four legs; and typically one external genitalia and anus.[9]
  • Omphalo-Ischiopagus: Fused in a similar fashion as ischiopagus twins, but facing each other with a joined abdomen akin to omphalopagus. These twins have four arms, and two, three, or four legs.[9]
  • Parapagus: Fused side-by-side with a shared pelvis. Twins that are dithoracic parapagus are fused at the abdomen and pelvis, but not the thorax. Twins that are diprosopic parapagus have one trunk and one head with two faces. Twins that are dicephalic parapagus have one trunk and two heads, and two (dibrachius), three (tribrachius), or four (tetrabrachius) arms.[9]
  • Craniopagus parasiticus: Like craniopagus, but with a second bodiless head attached to the dominant head.
  • Pygopagus (Iliopagus): Two bodies joined back-to-back at the buttocks.[9]

[edit] Separation

Surgery to separate conjoined twins may range from relatively simple to extremely complex, depending on the point of attachment and the internal parts that are shared. Most cases of separation are extremely risky and life-threatening. In many cases, the surgery results in the death of one or both of the twins, particularly if they are joined at the head. This makes the ethics of surgical separation, where the twins can survive if not separated, contentious. Dreger found the quality of life of twins who remain conjoined to be higher than is commonly supposed.[10] Lori and George Schappell are a good example.

[edit] Conjoined twins in popular culture

[edit] References

  1. ^ [http://www.scielo.br/scielo.php?pid=S1807-59322006000200013&script=sci_arttext Importance of angiographic study in preoperative planning of conjoined twins
  2. ^ The craniopagus malformation: classification and implications for surgical separation. James L. Stone and James T. Goodrich. Brain 2006 129(5):1084-1095 Abstract and free fullt text PDF
  3. ^ [http://www.scielo.br/scielo.php?pid=S1807-59322006000200013&script=sci_arttext Importance of angiographic study in preoperative planning of conjoined twins
  4. ^ Comment: Hate that dare not speak its name | Guardian daily comment | guardian.co.uk
  5. ^ BBC - h2g2 - Twins - A369434
  6. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
  7. ^ "Many-limbed India girl in surgery". BBC News (2007-11-06).
  8. ^ a b c d e The embryology of conjoined twins, 2008-06-21
  9. ^ a b c d e f g h i j k l Duplicata incompleta, dicephalus dipus dibrachius, 2008-06-20
  10. ^ One of Us: Conjoined Twins and the Future of Normal by Alice Dreger, Harvard, 2004

[edit] See also

[edit] External links

Wikimedia Commons has media related to:
v • d • e
Congenital abnormality - multiple abnormalities (Q87, 759.7)
Facial
Short stature
Limbs
Overgrowth
Collagen
Combined/other,
known locus
Combined/other,
unknown locus
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