Twins' Two-day Operation Under Way

Neurosurgeons in Singapore worked through last night to open the skull bone shared by Iranian twins in the second stage of an unprecedented and risky operation to separate the sisters.

Ladan and Laleh Bijani, 29, from Shiraz, who share a skull cavity but have individual brains, are the first adults to undergo such surgery. They are going through with the marathon operation, despite doctors warning that chances of total success are slim.

The operation, which is expected to last at least two days, began just after 8am yesterday when the sisters underwent magnetic resonance imaging tests. They were accompanied by seven close friends, part of a growing army of well-wishers who have set up camp at Singapore's Raffles Hospital.

"The scans were completed at 9.45am and the twins were in good spirits and were laughing with their friends after they were wheeled out from the radiology department," said Prem Kumar Nair, the hospital's corporate services manager.

After hugs and kisses, the Bijanis were wheeled into the theatre. The law school graduates had previously vowed to walk in, but doctors felt they were too tired.

Eight international experts, 18 local doctors and more than 100 support staff are performing the operation.

They are led by Keith Goh, from Singapore, who in 2001 led the team that successfully separated the Nepali babies, Jamuna and Ganga Shrestha, who were also joined at the head.

Chia Kok Hoong and Eric The began the operation by removing two sections of veins from the right thigh of Ladan to be used as a graft into her head. This was necessary because the girls share a vein to drain blood from their brains, and it was decided to leave this with Laleh.

The twins, who had been face down, were then repositioned into a special support frame so they could be in the preferred sitting position for the rest of the operation.

At 8.15pm the plastic and reconstructive team took over and began peeling back the twins' scalp, the hospital said, before neurosurgeons took over. Doctors estimate the neurosurgical separation of the conjoined brains will take at least 12 hours.

Dr Prem said last night that doctors were a couple of hours behind schedule. "We haven't really met any problems so far, but I would anticipate that the next 12 to 24 hours will be a critical period."

On Saturday, Dr Goh said after the tests that the reasons for undertaking the operation had risen "significantly" after doctors discovered the pressure inside the twins' brains was more than twice what it should be.

Benjamin Carson, from Johns Hopkins Children's Centre in Baltimore, who is on the surgical team, gave the sisters each a 50-50 chance of survival.

All the doctors are waiving their fees for the operation, expected to cost around £175,000.

Iranian president Mohammad Khatami said he prayed for the twins and wished them success.

If the operation is successful, the sisters plan to live in separate cities. Ladan intends to stay at home and fulfil her legal ambitions, while Laleh hopes to become a journalist in Tehran.