Two in 10 million: the conjoined twins saved by British surgeons

A team of 25 British specialists have successfully separated twins who were born joined at the head, in one of the most complex medical procedures ever attempted in this country.

Rital and Ritag Gaboura, now aged 11 months, are thriving after undergoing four operations at Great Ormond Street Hospital for Children in London. The girls were born with the tops of their skulls fused together – an extremely rare condition with a survival rate of one in 10 million.

The specialists will reveal today how they separated the infants' skulls and shared blood vessels despite encountering "innumerable challenges" during the marathon surgery, in which surgeons and nurses worked in shifts.

Conjoined twins are extremely rare, occurring in as few as one in every 100,000 live births. They are more common in South-west Asia and Africa, and are three times more likely to be girls. Only between 3 and 5 per cent of cases involve a fused skull, known as craniopagus twins, and of those most are stillborn or survive less than 24 hours.

Rital and Ritag were born with one of the most serious forms of the condition, because they shared blood vessels, and there was significant blood flow between their brains. Ritag supplied half her sister's brain with blood, and drained most of it back to her own body to re-oxygenate – which meant her tiny heart was doing most of the work for both of them.

Their condition posed a huge risk during surgery, as any significant drop in blood pressure could cause brain damage. So far the signs are good, with both girls reacting to stimuli in the same way they did before surgery. But it will be months or even years before their parents and doctors will know whether they have suffered any long-term problems.

The Sudanese twins, whose parents are both doctors, were born by caesarean section in Khartoum in October 2010. In April they were flown to the UK and have been treated at the expense of the Facing the World charity because the specialist care they needed was not available in Sudan.

This is the 23rd separation to be undertaken by the GOSH team, which is one of only a few in the world to take on such complex surgery, which typically involves several surgeons and anaesthetists.

Last April, four-month-olds Hassan and Hussein Benhaffaf, from Cork in Ireland, were successfully separated after being born joined at the chest. Bangladeshi girls Krishna and Trishna, now 5, were the last craniopagus twins to be successfully separated, in Melbourne, Australia in 2009.

Rital and Ritag are expected to return home soon but will need further plastic surgery on their skulls.

The girls' parents last night thanked the medical team for their work. "We are very thankful to be able to look forward to going home with two separate, healthy girls. We are very grateful to all the doctors who volunteered their time and to Facing the World for organising all the logistics and for paying for the surgery," they said.