Craniopagus parasiticus

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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 2 to 3 of 5,000,000 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 literature.


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.[2]

In normal monozygotic twin development, one egg 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.[3] This is thought to be the most likely reason why conjoined twins occur,[3] and could possibly play a role in the development of craniopagus parasiticus.[citation needed]

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] Another is 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]

A third 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.[4]


Related conditions[edit]

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

Dicephalic parapagus[edit]

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.[5]


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.[citation needed] Cats with the condition are referred to as 'Janus cats'. A cat named Frankenlouie was a famous example noted by the Guinness Book of World Records in 2012 for being the longest surviving Janus cat.


Few individuals survive until birth. For those who do, the only treatment available is to surgically remove the parasitic twin. Of the two documented attempts, however, one child died within hours and neither reached their second birthday.[citation needed] 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, but it has been suggested that cutting off the parasitic twin's arterial supply might improve the odds of the developed twin's survival.[1]


Only ten cases of craniopagus parasiticus have been documented, out of a total of at least eighty known cases of craniopagus in general.[6]

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

  • An earlier case was the so-called "Two-Headed Boy of Bengal", who was born in 1783 at the village of Mandal Ghat in the New Jalpaiguri district of the Indian state of West Bengal and died of a cobra bite in 1787. His skull remains in the collection of the Hunterian Museum of the Royal College of Surgeons of London.[6]
  • On December 10, 2003, Rebeca Martínez was born in the Dominican Republic. She was the first baby born with the condition to undergo an operation to remove the second head. She died on February 7, 2004, after an 11-hour operation.[7]
  • On March 30, 2004, Manar Maged was born. On February 19, 2005, 10-month-old Manar underwent a successful 13-hour surgery in Egypt. The underdeveloped conjoined twin, Islaam, was attached to Manar's head and was facing upward. Islaam could blink and even smile, but doctors determined she had to be removed, and that she could not survive on her own.[8] Manar was featured on an episode of The Oprah Winfrey Show and in the British documentary series Body Shock. Manar died on March 26, 2006, fourteen months after the surgery, just days before her second birthday, due to a severe infection in her brain.[9][10]
  • On January 20, 2021, a baby was born at the Elias Hospital in Bucharest, Romania, but died some hours after being born.[11]


Only ten cases of craniopagus parasiticus have been reported in the medical research literature. Of those cases, only four have survived birth.[6] The first case on record is that of Everard Home's Two-Headed Boy of Bengal, whose skull is preserved at the Hunterian Museum at the Royal Society of Surgeons.[12]


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, they have developed enough that they can live on their own.[13]

See also[edit]


  1. ^ a b c d Kansal, Ritesh; Kale, Chirag; Goel, Atul (October 2010). "Craniopagus parasiticus: A rare case". Journal of Clinical Neuroscience. 17 (10): 1351–1352. doi:10.1016/j.jocn.2010.01.053. PMID 20655232. S2CID 206313125.
  2. ^ Parasitic twin
  3. ^ a b Schoenwolf, Gary (2008). Larsen's Human Embryology, 4th Edition.
  4. ^ "Craniopagus parasiticus: a case illustrating its relationship to craniopagus conjoined twinning". MEDLINE Journals. 1997. Retrieved 2012-10-16.
  5. ^ Harma, M.; Oksuzier, C. (Feb 2005). "Vaginal delivery of dicephalic parapagus conjoined twins: case report and literature review". Tohoku J. Exp. Med. 205 (2): 179–85. doi:10.1620/tjem.205.179. PMID 15673976.
  6. ^ a b c Bondeson, Jan. "The Two-Headed Boy of Bengal | Articles | Features | Fortean Times UK". Archived from the original on April 5, 2012. Retrieved 2012-05-02.
  7. ^ "Two-Headed Baby Dies After Surgery". CBS News. 4 February 2004. Archived from the original on 21 October 2012. Retrieved 2 May 2012.
  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". Retrieved 2012-05-02.
  10. ^ "Two-head girl dies of infection". BBC News. March 26, 2006.
  11. ^ "Copil cu două capete, născut în România. Caz extrem de rar". Știri Diaspora. January 20, 2021. Retrieved January 21, 2021.
  12. ^ "RCSHC/P 1535 - Skull, craniopagus, asymmetrical, Morbid Anatomy of Monsters, Mounted dry bone". Royal College of Surgeons Online Catalogue (Surgicat). Retrieved 24 April 2017.
  13. ^ Sharma, Gaurav; Mobin, Sheila S. Nazarian; Lypka, Michael; Urata, Mark (2010). "Heteropagus (parasitic) twins: A review". Journal of Pediatric Surgery. 45 (12): 2454–63. doi:10.1016/j.jpedsurg.2010.07.002. PMID 21129567.


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