| Craniopagus parasiticus | |
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| Drawing of a skull of a child born in 1783 in 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]
In addition to craniopagus parasiticus, a few other conditions involve a child's, or animal's, birth with two heads or faces.
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]
There have been at least eighty known cases of craniopagus parasiticus. Only ten cases of craniopagus have been documented in medical research literature. [6]
Only four cases have been documented by modern medicine to have survived birth: [6]
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]
Twins are two offspring produced by the same pregnancy. Twins can be either monozygotic ('identical'), meaning that they develop from one zygote, which splits and forms two embryos, or dizygotic, meaning that each twin develops from a separate egg and each egg is fertilized by its own sperm cell. Since identical twins develop from one zygote, they will share the same sex, while fraternal twins may or may not. In very rare cases twins can have the same mother and different fathers.
Conjoined twins, popularly referred to as Siamese twins, are twins joined in utero. It is a very rare phenomenon, estimated to occur in anywhere between one in 49,000 births to one in 189,000 births, with a somewhat higher incidence in Southwest Asia and Africa. Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1.
A genetic chimerism or chimera is a single organism composed of cells with more than one distinct genotype. In animals and human chimeras, this means an individual derived from two or more zygotes, which can include possessing blood cells of different blood types, and subtle variations in form (phenotype). Animal chimeras are produced by the merger of two embryos. In plant chimeras, however, the distinct types of tissue may originate from the same zygote, and the difference is often due to mutation during ordinary cell division. Normally, genetic chimerism is not visible on casual inspection; however, it has been detected in the course of proving parentage. In contrast, an individual where each cell contains genetic material from two organisms of different breeds, varieties, species or genera is called a hybrid.
Apoplexy refers to the rupture of an internal organ and the associated symptoms. Informally or metaphorically, the term apoplexy is associated with being furious, especially as "apoplectic". Historically, it was used to describe what is now known as a hemorrhagic stroke, involving a ruptured blood vessel in the brain. However, modern health care professionals typically specify the anatomical location of the bleeding, such as cerebral, ovarian, or pituitary.
The blastocyst is a structure formed in the early embryonic development of mammals. It possesses an inner cell mass (ICM) also known as the embryoblast which subsequently forms the embryo, and an outer layer of trophoblast cells called the trophectoderm. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoel. In the late blastocyst, the trophectoderm is known as the trophoblast. The trophoblast gives rise to the chorion and amnion, the two fetal membranes that surround the embryo. The placenta derives from the embryonic chorion and the underlying uterine tissue of the mother.
A parasitic twin, also known as an asymmetrical twin or unequal conjoined twin, occurs when a twin embryo begins developing in utero, but the pair does not fully separate, and one embryo maintains dominant development at the expense of the other. It results from the same processes that also produces vanishing twins and conjoined twins, and may represent a continuum between the two. In parasitic twins, one ceases development during gestation and is vestigial to a mostly fully formed, otherwise healthy individual twin. The undeveloped twin is termed as parasitic, because it is incompletely formed or wholly dependent on the body functions of the complete fetus. The independent twin is called the autosite.
In biology, a blastomere is a type of cell produced by cell division (cleavage) of the zygote after fertilization; blastomeres are an essential part of blastula formation, and blastocyst formation in mammals.
Embryo transfer refers to a step in the process of assisted reproduction in which embryos are placed into the uterus of a female with the intent to establish a pregnancy. This technique - which is often used in connection with in vitro fertilization (IVF) - may be used in humans or in other animals, in which situations and goals may vary.
A skull fracture is a break in one or more of the eight bones that form the cranial portion of the skull, usually occurring as a result of blunt force trauma. If the force of the impact is excessive, the bone may fracture at or near the site of the impact and cause damage to the underlying structures within the skull such as the membranes, blood vessels, and brain.
Ischiopagi comes from the Greek word ischio- meaning hip (ilium) and -pagus meaning fixed or united. It is the medical term used for conjoined twins who are united at the pelvis. The twins are classically joined with the vertebral axis at 180°. The conjoined twins usually have four arms; two, three or four legs; and typically one external genitalia and anus.
Clarence and Carl Aguirre are former conjoined twins born in Manila. They were conjoined at the top of the head and shared 8 centimetres (3.1 in) of brain. More than 1–2 centimetres (0.4–0.8 in) will affect brain functionality in one or both of twins. Without separation, they were expected to live around 6–8 months.
Edward Mordake is the apocryphal subject of an urban legend who was born in the 19th century as the heir to an English peerage with a face at the back of his head. According to legend, the face could whisper, laugh or cry. Mordake repeatedly begged doctors to remove it, claiming it whispered bad things to him at night. Mordake died by suicide at the age of 23.
Polycephaly is the condition of having more than one head. The term is derived from the Greek stems poly meaning "many" and kephalē meaning "head". A polycephalic organism may be thought of as one being with a supernumerary body part, or as two or more beings with a shared body.
Diprosopus, also known as craniofacial duplication, is an extremely rare congenital disorder whereby parts (accessories) or all of the face are duplicated on the head.
Implantation, also known as nidation, is the stage in the embryonic development of mammals in which the blastocyst hatches, attaches, adheres, and invades into the wall of the female's uterus. Implantation is the first stage of gestation, and, when successful, the female is considered to be pregnant. An implanted embryo is detected by the presence of increased levels of human chorionic gonadotropin (hCG) in a pregnancy test. The implanted embryo will receive oxygen and nutrients in order to grow.
Lakshmi Tatma is an Indian girl born in 2005 in a village in Araria district, Bihar, with four arms and four legs. She was actually one of a pair of ischiopagus conjoined twins, one of which was headless because its head had atrophied and chest had not fully developed in the womb, causing the appearance of one child with four arms and four legs. She has undergone surgery to remove these extra limbs.
Dicephalic parapagus is a rare form of partial twinning with two heads side by side on one torso. Infants conjoined this way are sometimes called "two-headed babies" in popular media. The condition is also called parapagus dicephalus.
Craniopagus twins are conjoined twins who are fused at the cranium. The union may occur on any portion of the cranium, but does not primarily involve either the face or the foramen magnum; their brains are usually separate, but they may share some brain tissue. Conjoined twins are genetically identical and always share the same sex. The thorax and abdomen are separate and each twin has their own umbilicus and umbilical cord.
The Dextroscope is a medical equipment system that creates a virtual reality (VR) environment in which surgeons can plan neurosurgical and other surgical procedures.
András Csókay, is a Hungarian neurosurgeon with international recognition in the field of neurosurgery for his development of a technique to enhance microsurgical precision in the vascular tunnel and for the separation of a pair of Bangladeshi (Islam) Craniopagus Twins.