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Thursday 2 July 2015


Diprosopus – Craniofacial Duplication 

Diprosopus tends to take place in combination with other congenital disorders especially anencephaly, neural tube defect as well as cardiac malformations. Being a congenital defect, it is also known as craniofacial duplication and the exact description is referred to a foetus with a single truck, normal limbs with facial features that are duplicated to certain degree.

 Less severe example is when the foetus tends to have a duplicated nose and eyes are spread out, far apart. In most cases, the complete face is duplicated and hence the name diprosopus has been used. The term `diprosopus’ is derived from the Greek word `di’ meaning `two’ while `prosopon’ – `face’ meaning `two faced’.When it takes place, the brain could possibly show abnormalities from partial to total duplication of brain structures and/or underdevelopment of the brain tissues.

Though this disorder is classically considered to be conjoined twinning, this irregularity is not usually due to the incomplete separation or fusion of two embryos and is the outcome of abnormal activity of the protein known as sonic-hedgehog – SHH. This name of the protein was motivated by the Sonic the Hedgehog video game character and part of a characteristic naming tradition in molecular biology research.

Major Role in Signalling Craniofacial Patterning - SHH

SHH, together with the corresponding gene is considered to play a major role in signalling craniofacial patterning at the time of embryonic development. Besides, SHH also governs the width of the facial features and greater the widening, the more structures tend to get duplicated mostly in a mirror image form.

 The same has been confirmed in the laboratory on introducing pellets of the SHH protein in chicken embryos, the outcome of which was, chickens having duplicate beaks. Insufficient quantities of this protein could lead to opposite situations like cyclopia wherein the facial features tend to be inadequately developed.

Development of healthy brain is also dependent on the signalling function of SHH and during the development process of the embryonic, SHH tends to direct embryonic cells to establish in precise areas which at a later stage become specialized neural tissue enabling the controlling of the size and shape of the brain structures. Most of the infants having diprosopus tend to be stillborn and known instances of diprosopus humans surviving for longer than a few minutes to hours after birth are rare with only a few recorded.

Various Mechanisms – Phenomenon of Craniofacial Duplication

Researchers have suggested various mechanisms in explaining the phenomenon of craniofacial duplication and often class diprosopus as a rare variant of conjoined twinning when two completed identical faces are present. They are of the opinion that two faces are the outcome of cranial bifurcation of the notochord during neurulation where the bifurcation result in two vertebral axes and neural plates, developing alongside each other, complete with neural crest derivatives.

 Around only 0.4% or conjoined twins tend to have diprosopus. Another possibility of the abnormality could be an increase in the expression of the protein SHH that is needed for craniofacial patterning during the development process. While in the case of chickens, researchers imitated several of the phenotypes connected with craniofacial duplication by exposing the embryos to excess of SHH where the chicks were born with two beaks and eyes spaced wide apart.

Less of SHH could also affect midline facial structure causing the developing eyes to fuse together. This disorder can be identified in utero with the use of technology like ultrasound, computer tomography – CT scanning, magnetic resonance imaging – MRI and MR angiography. The first warning of craniofacial duplication is known as polyhydramnios, which is a condition wherein there is an abnormally high content of amniotic fluid existing within the amniotic sac.

Few Treatment Options/Corrective Surgery Techniques

No treatment exists in the cure of diprosopus though therapeutic abortion is at times an option if the condition is identified in the initial stage of pregnancy. Due to this disorder being rare, there are few treatment options or corrective surgery techniques that are documented. Duplication of face together with its structure allows embryologist to assume about the mechanism of the duplication.

The varied range of expression connecting craniofacial duplication differs to such an extent that there could be a possibility that more than one mechanism could explain the phenomenon. Additional examination of the case could clarify the mechanism which could be responsible for this disorder and also the mechanisms accountable for normal development. Diprosopus is evidently a distressing condition for those who suffer from it and though human cases are rare, it is known in several animal species.

In the case of feline, they are known as Janus Cats while a relatively popular pig with this disorder was known as `Ditto the pig’, who survived several years under the care of her owner. Generally people and also animals that are born with these forms of serious defects have to put up with mixed gloomy curiosity and religious damnation. Individuals with serious disfigurements are often despised by the society and also exploited. However with advancement in research, there could be some solutions offered for the future cases instead of despise and mockery

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