Conjoined twins share one body; can they be separated?

Conjoined twins were recently born in northern Brazil with a rare form of the condition called dicephalic parapagus, which refers to twins who have one body and two heads.

The twins, named Jesus and Emanuel, have separate brains and spinal cords, according to the Associated Press, but they share vital organs such as a heart, liver and lungs.

Conjoined twins occur once in every 200,000 births, according to the University of Maryland Medical Center website, but there are no statistics for the frequency of this particular kind of twinning. As for how conjoined twins are formed, there are two theories: fusion and fission, says Dr. James Stein, associate chief of surgery at Children’s Hospital Los Angeles. In 2003 Stein led the surgical team that separated conjoined twins Macey and MacKenzie Garrison.

In the fusion theory, he says, two zygotes form and then come together, with the joining happening in a number of ways. In the fission theory, cells divide into two separate entities but never do so completely, remaining attached.

From what he knows about the twins, Stein says separating them wouldn’t be recommended, since they share vital organs. “In this particular case the kids lack a second body, so they don’t have that component,” he said.

Neurological tests would show if both heads are functioning normally, Stein added, and if so, the twins may develop normally, perhaps building the type of synergy that 21-year-old dicephalic parapagus twins Abigail and Brittany Hensel have.

The twins, born in Minnesota, were the subject of a 2006 show on TLC documenting their lives. Although each twin controls the half of the body she is on, they type, drive a car and do everything else with perfect coordination. (The Hensel twins also have some separate organs, such as hearts and stomachs.)

“It’s a synergy that’s unique to conjoined twins who cannot be separated,” Stein said. “It’s an amazing level of coordination that is predominantly a learned behavior, rather than something that’s innate.”

In the case of Jesus and Emanuel, Stein said, “They have one functional body and hopefully they’ll be able to develop pretty successfully.”