An international team of five neurosurgeons successfully attached a new vein and began separating 29-year-old Ladan and Laleh Bijani's brains in the unprecedented operation expected to last two to four days, a Raffles Hospital official said on condition of anonymity.
"Separation surgery began at 5 p.m." local time, the official said.
Tackling the shared vein was considered the biggest obstacle in the surgery: Other than sharing the vein, the women's brains are not joined — although they touch inside their skulls. Their bodies are otherwise distinct.
German doctors told the twins in 1996 that the shared vein, which drains blood from their brains, made surgery too dangerous.
"There may still be some difficulties encountered, but up until now we are quite satisfied with the progress of the whole surgery," hospital spokesman Dr. Prem Kumar told a news conference earlier Monday.
"They are stable, the anesthesia is working quite well, so we are cautiously optimistic," he said.
The operation could kill one or both of the sisters, but after a lifetime of compromising on everything from when to wake up to what career to pursue, the Bijani sisters said they would rather face those dangers than continue living joined.
Before dawn, surgeons began stitching a vein taken from Ladan's thigh to one of the twin's brains to compensate for the removal of the shared vein, Kumar said. He would not say who received the original, finger-thick shared vein.
Classical music played softly as surgeons worked simultaneously in tight spaces in front of and behind the twins, who are sitting in a custom-built brace connected to an array of lines feeding them intravenously and monitoring their vital signs, Kumar said.
"Nothing is going on at a hurried pace," he said. "Everything is quite calm and measured. There's lots of discussion."
Surgeons had earlier encountered unexpected delays cutting through their skulls when the bone turned out to be denser than previously thought, Kumar said.
"The procedure took six hours — longer than originally expected
because the bones were thick and compact, especially in the areas where the two skull bones fuse," Kumar said.
The twins spent months training at a gym to build up strength for the surgery and Kumar said they could be kept asleep for four days if necessary.
The twins said they wanted to walk into the operating room as a sign of courage, but they were brought in by wheelchair because they were too tired to stand, Kumar said.
Participating neurosurgeon Dr. Benjamin Carson, the director of pediatric neurosurgery at Johns Hopkins Children's Center in Baltimore has successfully separated three sets of craniopagus twins — siblings born joined at the head.
However, this is the first time surgeons have tried to separate adult craniopagus twins. The surgery has only been performed successfully since 1952 on infants, whose brains can more easily adapt and recover.
"If God wants us to live the rest of our lives as two separate, independent individuals, we will," Ladan Bijani said before the operation.
The Bijani sisters were born in Firouzabad in southern Iran in 1974. In a statement read on state-run Iran television late Sunday, President Mohammad Khatami hoped for success.
"The prayers of the Iranian nation are with you," Khatami said in a message addressed to the medical team. "I hope to see my patient daughters Laleh and Ladan healthy and fresh as soon as possible."
An international team of 28 doctors and about 100 medical assistants were enlisted for the surgery. The $288,000 cost of the operation surgery is being underwritten by Raffles Hospital, and the doctors' fees are being waived.