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Monday, 9 April, 2001, 11:55 GMT 12:55 UK
Joined at the head: medical briefing
interlinked brains
A model of the two interlinked brains (picture: AFP)
Two conjoined twins linked at the head are undergoing a marathon operation in Singapore.

Separating conjoined twins like these is one of the most challenging operations facing a modern surgeon.

There are only a handful of surgeons and centres around the world with experience of this type of operation.

The number of cases which arise each year are tiny - only 2% or 3% of all conjoined twins, of whom there are few enough, are joined in this way.

However, despite the lack of regular practice experienced by surgeons, dozens of these operations have been successfully performed - and the join at the head is no longer the immovable obstacle it used to be.

Every case of this type - called "craniopagus" by surgeons - is unique.

There is no fixed amount of tissue that is shared by the twins - it can be anything from just a few blood vessels to large sections of brain tissue and nerves.

The more tissue that is shared, the less likely it is that a successful operation can take place. The chances of leaving either or both twins with significant - and possibly even fatal - brain damage is too high.

Until quite recently it was harder for surgeons to get a close look at the tissues linking the two babies.

However, the latest 3-D imaging magnetic scans allow doctors an "inside view" of the complicated tangle of blood vessels and other tissues and vessels, such as sinuses.

It means that in more extreme cases than ever before, doctors can spot a potential "plane of separation" - in short, a dotted line weaved through the tissues which, if cut, maximises the chances of safe separation.

Operations that were unthinkable even to attempt a decade ago are now considered by surgeons.

Virtual reality

Dr Benjamin Carson, a surgeon at Johns Hopkins Hospital in Baltimore, US, attempted two craniopagus separations before 1997, both unsuccessfully.

However, then, he was asked for an opinion on Joseph and Luka Banda, South African twins joined at the head.

The scans suggested their brains were not fused together, and Dr Carson used the 3D technology to plot his course between their skulls, practising every slice with his scalpel in virtual reality.

Having researched the operation in detail in Baltimore, he returned to South Africa to carry out the operation.

He told the BBC: "There came a point when looking at their brains it appeared there was no plane and that we wouldn't be able to get them apart - except that I knew from having done the virtual surgery before, that there was a plane and I remembered where the plane was.

"So I began to tease in that direction and eventually the plane showed itself."

Such operations are always marathons, and this one took 28 hours - but both boys recovered and although may suffer some mental impairment, are doing well.

The brain is by no means the final frontier in twin separation surgery. Surgeons are now attempting to separate twins who are sharing a single heart - an enormous challenge.

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See also:

09 Apr 01 | Asia-Pacific
Siamese operation into fourth day
10 Apr 01 | Asia-Pacific
Singapore twins stable but sleepy
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