Craniopagus parasiticus

Drawing of a skull of a child born in 1783 in Bengal, affected by craniopagus parasiticus.
Drawing of the Boy of Bengal, affected by craniopagus parasiticus.

Craniopagus parasiticus is an extremely rare type of parasitic twinning occurring in about 4 to 6 of 10,000,000 births.[1] In craniopagus parasiticus, a parasitic twin head with an undeveloped body is attached to the head of a developed twin. Fewer than a dozen cases of this type of conjoined twin have been documented in the literature. Most infants with this condition are stillborn, or die shortly after birth.

Terminology

In the past, the use of terminology when describing parasitic twins has been somewhat inconsistent. By definition, a parasitic twin is joined to another twin in a certain anatomical location or position on the developed twin's body. The underdeveloped twin is termed the parasite, and the developed twin is termed the autosite. The autosite can have some abnormalities, as well. For the most part, however, it has developed enough to where it can live on its own.[2]

History

Only ten cases of craniopagus parasiticus have been reported in the medical research literature. Of those cases, only three have survived birth.[3] The first case on record is that of Everard Home's Two-Headed Boy of Bengal, whose head is now preserved at the Hunterian Museum at the Royal Society of Surgeons.

Development

The exact development of craniopagus parasiticus is not well known. However, it is known that the underdeveloped twin is a parasitic twin. Parasitic twins are known to occur in utero when monozygotic twins start to develop as an embryo, but the embryo fails to completely split. When this happens, one embryo will dominate development, while the other's development is severely altered. The key difference between a parasitic twin and conjoined twins is that in parasitic twins, one twin, the parasite, stops development during gestation, whereas the other twin, the autosite, develops completely.[4]

In normal monozygotic twin development, one embryo is fertilized by a single sperm. The egg will then completely split into two, normally at the two-cell stage. If the egg splits in the early blastocyst stage, two inner cell masses will be present, eventually leading to the twins sharing the same chorion and placenta, but with separate amnions. However, the egg can split into two, but still have one blastocyst. This will lead to one inner cell mass and one blastocyst. Then, as the twins develop, they will share the same placenta, chorion, and amnion.[5] This is thought to be the most likely reason why conjoined twins occur,[5] and could possibly play a role in the development of craniopagus parasiticus.

One hypothesis is that craniopagus parasiticus starts with the development of two fetuses from a single zygote that fail to separate at the head region around the second week of gestation.[1] Some believe, however, that it occurs later in development, around the fourth week of gestation, at which time the two embryos fuse together near the anterior open neuropore.[1]

Another hypothesis is that there is joining of the somatic and placental vascular system of the twins, as well as a degeneration of the umbilical cord of the parasitic twin. This suggests that craniopagus parasiticus develops due to the lack of blood supply to one of the twins.[6]

The condition also seems to be more predominant in males than females, with seven of the nine (78%) reported cases being male. With the number of cases being so small, it is hard to say whether this data has any significance. However, it might provide some insight into the possibility of a genetic predisposition to the condition.

Treatment

With so few individuals actually surviving until birth, the only treatment option is surgery to try to remove the parasitic twin. Surgery, however, is very dangerous and has been successful only once. The problem with surgical intervention is that the arterial supplies of the head are so intertwined that it is very hard to control the bleeding, and it has been suggested that cutting off the parasitic twin's arterial supply might improve the odds of the developed twin's survival.[1]

Cases

Only ten cases of craniopagus parasiticus have been documented, out of a total of at least eighty known cases of craniopagus in general.[3]

Only three cases have been documented by modern medicine to have survived birth:

Related conditions

In addition to craniopagus parasiticus, a few other conditions involve a child's, or animal's, birth with two heads or faces.

Dicephalic parapagus

Dicephalic parapagus is a condition where two heads are side by side on a single torso, with varying degrees of twinning of organs and structures within the torso.[10]

Diprosopus

Diprosopus occurs when a single body and neck are present, but there is a duplication of the structures of the face. This is different from craniopagus parasiticus in that there is only one head, although there is a duplication of the craniofacial features. Diprosopus can range from having two fully formed faces to just a duplication of the nose or eyes.

See also

References

  1. 1 2 3 4 "Craniopagus parasiticus: A rare case". Journal of Clinical Neuroscience. October 2010. Retrieved 2012-10-16.
  2. ↑ "Heteropagus (parasitic) twins: a review". Journal of Pediatric Surgery. October 2010. Retrieved 2012-11-27.
  3. 1 2 3 Bondeson, Jan. "The Two-Headed Boy of Bengal | Articles | Features | Fortean Times UK". Forteantimes.com. Archived from the original on April 5, 2012. Retrieved 2012-05-02.
  4. ↑ Parasitic twin
  5. 1 2 Schoenwolf, Gary (2008). Larsen's Human Embryology, 4th Edition.
  6. ↑ "Craniopagus parasiticus: a case illustrating its relationship to craniopagus conjoined twinning". MEDLINE Journals. 1997. Retrieved 2012-10-16.
  7. ↑ "Two-Headed Baby Dies After Surgery". CBS News. 2009-02-11. Retrieved 2012-05-02.
  8. ↑ "In Depth | Two-head girl dies of infection". BBC News. 2006-03-26. Retrieved 2012-05-02.
  9. ↑ "Manar Maged Dies From Brain Infection". Multiples.about.com. Retrieved 2012-05-02.
  10. ↑ Harma, M.; Oksuzier, C. (Feb 2005). "Vaginal delivery of dicephalic parapagus conjoined twins: case report and literature review". Tohoku J. Exp. Med. (205): 179–85.

Bibliography

  • Aquino DB, Timmons C, Burns D, Lowichik A (1997). "Craniopagus parasiticus: a case illustrating its relationship to craniopagus conjoined twinning". Pediatr Pathol Lab Med 17 (6): 939–44. doi:10.1080/107710497174381. PMID 9353833. 
  • Bondeson J, Allen E (1991). "Everard Home's famous two-headed boy of Bengal and some other cases of craniopagus parasiticus". Surg Neurol 35 (6): 483. doi:10.1016/0090-3019(91)90185-C. PMID 2053064. 
  • Bondeson J, Allen E (1989). "Craniopagus parasiticus. Everard Home's Two-Headed Boy of Bengal and some other cases". Surg Neurol 31 (6): 426–34. doi:10.1016/0090-3019(89)90087-6. PMID 2655135. 
  • Gilbert-Barness E, Debich-Spicer D, Opitz JM, (2003). "Conjoined twins: Morphogenesis of the heart and a review". Am. J. Med. Genet. 120A: 568. doi:10.1002/ajmg.a.10195. 
  • Nair KR (1990). "Craniopagus parasiticus". Surg Neurol 33 (2): 159. doi:10.1016/0090-3019(90)90033-L. PMID 2406987. 
  • Okazaki JR, Wilson JL, Holmes SM, Vandermark LL (1987). "Diprosporus: Diagnosis in utero". American Journal of Roentgeneology 149 (1): 147. doi:10.2214/ajr.149.1.147. 
  • Schoenwolf, Gary (2008). Larsen's Human Embryology, 4th Edition. 
  • Sharmaa G, Mobina S, Lypkaa M, Urata, (2010). "Heteropagus (parasitic) twins: a review". Pediatric Surgery 45 (12): 2454. doi:10.1016/j.jpedsurg.2010.07.002. 
  • Wang DM, Zhang PL (1985). "[A case report of craniopagus parasiticus (clinical features and the histological study of the accessory brain)]". Zhonghua Zheng Xing Shao Shang Wai Ke Za Zhi 1 (1): 31–3. PMID 3939788. 
  • Wang TM, Li BQ, Li-Che, Fu CL (1982). "Craniopagus parasiticus: a case report of a parasitic head protruding from the right side of the face". Br J Plast Surg 35 (3): 304–11. doi:10.1016/0007-1226(82)90119-9. PMID 7150854. 

External links

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