Craniopagus Parasiticus is a type of parasitic twinning in which conjoined twins are connected at the skull. While the genetic condition of craniopagus twinning is seen in around 2-6% of all conjoined twins, the much more rare parasiticus variation has only been documented between 7 to 10 times. In parasiticus twinning the embryos are conjoined at the cranium, however, one of the fetuses generally fails to develop organs and forms little more than a head and “stump” of a thorax. In most documented cases, the second head is capable of blinking, smiling, and other basic functions. However, it most often has no organs to perform actions necessary to survive on its own without attachment to the autosite. It is parasitic in that it relies on the other twin for blood supply and nutrients to sustain life. In multiple cases, this has shown harmful on the small autosite twin as it put a massive demand on their bodies to supply for both twins. Of the documented cases, all but three have been stillborn.
During gestation, a fertilized egg goes through cellular division in the blastocyst phase. In most cases of twinning, the blastocyst will have one chorion and two amnions. (Basically, placenta and “water sack” that the fetus floats in) In conjoined twins, the blastocyst phase results in the cells dividing but having one inner cell mass (two twins formed as a conjoined, improperly divided group of cells), one amnion, and one chorion. There are two current theories on what happens when one of those twins suddenly stops growing during gestation and the other continues to grow as normal. However, researchers are still unsure of the exact mechanism that causes the condition to exist because of the extremely rare nature of it.
The Fission Theory:
One zygote leads the development of the two fetuses but separation fails during the second or fourth week of gestation. Due to this lack of separation the continued independent development of the second fetus is halted.
Blood Supply Theory:
This idea theorizes that lack of blood supply to the second twin by degeneration of the umbilical cord halts development of the second fetus. Hypoplasia found in the umbilical cord seems to support this hypothesis. There are two arteries and one vein in all umbilical cords which provide important nutrients to the fetus and provide fetal circulation via the placenta until birth. They also remove wastes from fetal circulation via the placenta. Improper formation or damage to the cord can result in damage to the fetus and/or fetal demise. In craniopagus parasiticus there is more of a demand on fetal circulation as well.
The Two-Headed Boy of Bengal:
The first documented case of Craniopagus Parasiticus was a boy in Mindal Gait, Bengal in 1783. When the boy was born he was so terrifying to the midwife that he was thrown into a nearby fire and was badly burned on the face and trunk. The parasite twin rested almost perfectly upside down atop the autosite twin’s head, consisting of a skull and neck. It seemed to function separately from the main head and upon examination following the boy’s death had a separate functioning brain. The child lived to the age of 4 when he died of a snake bite. His body was exhumed later to be studied and his skull now resides in the Hunterian Museum of Royal College of Surgeons in London. Although the family resided in a small farming community at the time of his birth it is reported that the child’s peculiar anomaly quickly drew the attention of many and they took the boy to Calcutta and beyond, showing his condition to fascinated onlookers for money. There are no records from the boy’s life, however, as to whether the condition affected him from day to day.
On December 1o, 2003 Rebecca Martinez was born in the Dominican Republic with a parasitic twin attached to the superior aspect of her cranium. Prenatal tests had shown what doctors believed was a tumor prior to birth. On February 7, 2004, an 11-hour surgery was performed in an attempt to remove the parasitic twin from little autosite twin Rebecca. Unfortunately, she died in the operating room from massive hemorrhage leading to an imbalance in blood pressure. Doctors believe that loss of blood caused a heart attack because her body was still trying to perfuse the parasitic head that was once there, making it less able to clot. Although multiple transfusions were done they were unable to keep up with the blood loss.
On examination, Rebecca’s parasitic head had its own partially developed brain, ears, eyes, and lips. It appeared that it was growing faster than the autosite twin in some respects.
In 2005, 10-month-old Manar became the first successful separation of a Craniopagus Parasiticus twin at the Benha Pediatric Hospital just north of Cairo, Egypt. Bleeding was stated to be the most serious complication of the surgery again as the parasite and autosite were connected through the middle cerebral artery, which is one of the main arteries supplying blood to the brain. The autosite’s (Manar) dura was repaired with artificial dural grafts. Free bone grafts from the parasite (Islaam) were used to cover the osseous defect left in the autosite from the removal of the twin. Grafts of skin from the parasite were also used to cover the cranium.
Manar seemed to be doing well, but unfortunately succumbed to a bacterial infection of the brain and heart problems on March 25 of the following year.
Craniopagus Parasiticus is a difficult condition to study because it is such a rare genetic condition. Unfortunately, separation rarely bodes well for either the autosite or the parasite due to the intricate vascular bond between the two. However, advances are being made with every surgery. Surgeons from previous surgeries are finding tactics with each procedure that will help with the next one to control bleeding, decrease intracranial pressure following the surgery, and improve outcomes. Much like other conjoined twins, however, craniopagus parasiticus twins are often varied in the degree and location of attachment. No two cases are the same. Each case involves a detailed study of the vasculature, bone structure, and other connected organs that the autosite and parasite share in order to perform a successful separation.
I find this anomaly absolutely fascinating and hope that you do as well. I encourage you to look into it more and welcome any questions that you may have. Please note that any rude or discriminatory comments will be deleted. This is not my intent on posting these in the least. These children are beautiful and it breaks my heart that their lives were so short. I think it is interesting to discuss, however, just what happened here.
Nega W, Damte W, Girma Y, Desta G, Hailemariam M. Craniopagus parasiticus – a parasitic head protruding from temporal area of cranium: a case report. J. Med. Case Reports. 2016: (1) 12. doi 10.1186/s13256-016-1023-3 [PUBMED]
Kansal R, Kale C, Goel A. Craniopagus parasiticus: A rare case. J Clin Neurosci. 2010;17(10):1351–2. doi: 10.1016/j.jocn.2010.01.053. [PubMed]
Aquino DB, Timmons C, Burns D, Lowichik A. Craniopagus parasiticus: a case illustrating its relationship to craniopagus conjoined twinning. Pediatr Pathol Lab Med. 1997;17(6):939–44. doi: 10.1080/15513819709168757. [PubMed]
Bondeson J, Allen E. Everard Home’s famous two-headed boy of Bengal and some other cases of craniopagus parasiticus. Surg Neurol. 1991;35(6):483. doi: 10.1016/0090-3019(91)90185-C. [PubMed]
Bondeson J. Two Headed Boy of Bengal and Other Medical Marvels. 2004: (9) 9. Cornell University Press.
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