Medicine's one chance in 100,000 challenge

Siamese twins can now be separated and live happy lives. WARREN GAMBLE looks at the progress medical science has made in handling this rare malformation.

For all its advances medical science cannot yet explain why Siamese twins occur.

The problem happens early in the foetal cycle. In cases of identical twins a single fertilised egg splits into two masses. In Siamese twins - known medically as conjoined twins - the separation is not completed for as yet unknown reasons.

Every case is different, and it is fortunately rare - about one in 100,000 births, although unexplained global variations occur.

New Zealand has had only been five recorded cases, including the twin girls now at National Womens Hospital.

The most common position for Siamese twins is known as thoracopagus (understood to be the condition of the Auckland twins). In this position the twins are face-to-face and commonly share a chest wall, diaphragm and upper abdominal wall.

Other forms involve connections at the pelvis and skull.

While doctors cannot pinpoint why it happens, medical improvements mean that the chances of successful separation are much greater today than in past centuries when they were regarded as monsters.

Doctors say the Siam born twins, Eng and Chang Bunker, whose circus shows popularised the Siamese name for the condition in the mid-1800s, in fact could have been successfully separated using modern techniques.

Dr Alex Auldist, a senior surgeon at Melbourne's Royal Children's Hospital, said before modern obstetrics Siamese twins usually resulted in a triple tragedy, killing the mother in childbirth as well.

But he said now through advances such as early ultra-sound detection and teams of paediatric specialists there was a realistic chance of separation offering normal lives for each twin.

Dr Auldist was the chief surgeon at the successful 1996 separation of two Papua New Guinea twins who were joined from chest to navel and had connected livers.

Crucially although their heart cavities were pressed against each other, they did not share any heart muscle.

He saw the twins again last year as three-year-olds and they were "very well, very beautiful little girls".

A Starship paediatric surgeon, Dr Anne Kolbe, co-ordinated the medical team for Solomon Island Siamese twin girls who died at Auckland Hospital in 1987 after an Air Force rescue flight.

The girls had separate hearts but shared some cardiac chambers. The hearts were also diseased and very small giving no hope for separate survival.

Dr Kolbe said the management of such cases required extremely detailed and careful planning, keeping the parents informed about every option.

"It often takes a while to know realistically if the babies can be separated.

"Once you get to that stage it's like a lot of other things in medicine; one needs to be honest, take into account the family's feelings and be sure they understand the potential for what might happen."

A Waikato Hospital paediatric surgeon, Dr Stuart Brown, said separation could be a straightforward operation if shared organs were able to be divided and still function effectively.

He was involved in the successful separation of twin girls at Waikato Women's Hospital in 1987. In that case the girls' had joined livers,bowel and bladder but there was enough organ and duct systems for both to be divided and function individually.

"Where you get into real difficulties is where you have a shared organ that it's impossible to divide it so each is good enough to function individually."

Of the four cases of Siamese twins have been recorded in New Zealand, the first was in 1936 when two girls joined at the chest died at birth in Waikato Hospital. The 22-year-old mother was seriously ill during the delivery but survived.

In 1967 two girls were also stillborn to a 22-year-old mother at Taumarunui Hospital.

Twenty years later there was a happier ending for another pair of girls joined "top-to-tail" at the lower chest and upper abdomen. Crucially, both had their own vital internal organs.

In a two-and-a-half hour operation doctors at Waikato Hospital successfully separated them. Apart from a zig-zag scar and a later operation to give them navels, the twins had no other physical reminder of their shared beginning.

Their parents' wish for strict anonymity was preserved, and today, aged 13, they are understood to be living normal lives.

The previous most recent case of New Zealand conjoined twins, two girls born at National Women's Hospital in Auckland in 1989, also survived past birth but died three months later.

The pair were connected at the lower chest and upper abdomen. Both had separate, but joined hearts, and they were also connected at the liver.

At the time doctors said the shared organs made surgical separation almost impossible.

But they had been progressing well before their condition suddenly worsened after they had been admitted to hospital as a precautionary measure because one was suffering from a cold.

It was thought their death was not directly related to their being conjoined twins, although that was a complicating factor.

Although Siamese twins have been documented for several hundred years the term came into use after the most famous pair, Chang and Eng Bunker.

They were born in Thailand, then Siam, in 1811, of Chinese extraction. They were joined from the chest to navel but were eventually able to stand side-by-side.

As children they learned to walk, run, and swim in perfect combination. It was while swimming that they caught the attention of a British merchant and American sea captain who bought the pair, and took them to the United States.

For 10 years the two appeared as showmen in concert halls across the States and in Europe performing gymnastic and strongmen feats. It included a stint at a museum run by famed circus magnate P.T. Barnum where they earned the name "Siamese".

Their lives became even more remarkable when they settled down on a Wilkesboro, North Carolina farm. There they married two sisters, and fathered a total of 21 children.

Domestic quarrels meant they had two houses, spending three days at a time with each wife. They often argued with each other and had different dispositions: Chang drank sometimes to excess, while Eng was a teetotaller.

They died with hours of each other, aged 62.