Craniopagus twins are twins that are conjoined at the head. This happens to about one in every 2.5 million births. Twins in the United States occur about one in every thirty-one births. The operation of separating conjoined twins, let along craniopagus twins, is a very risky procedure. However, it is one that needs to be done. Blood supply is often shared between the two twins. The stronger twin ends up having to pump it's heart harder in order to make up for the weaker twin. The stronger child then suffers from the extra effort.
These twins, Rital and Ritag Gaboura, from Sudan traveled to London to be separated. It is a procedure that would take four different operations. The first of which was one to stretch their skin so it could fit over their head once the separation is complete. Luckily for these twins the operation went smoothly and both girls are alive and healthy. Operations of this sort are not often done, and very often not successful.
I did not realize that one twin would have to make up for the other. I would also like to know if both of their brain are complete in mass and function. The article said that they will not know if either of the girls are going to be brain damaged until they get older. Science has come a long way since the 1950's when the first successful operation of this sort was reported. It gives families everywhere a hope, not to mention anyone with a deformity, in their brain or not. http://www.cbsnews.com/8301-504763_162-20108161-10391704.html
A different article looked back on different twins after their surgery and noted that both twins were well. One just had some hearing problems from a deficient from the surgery and her brain fluid did not drain well. It also just said that her development is slower than that of her sister's. http://faculty.washington.edu/chudler/ctwins.html