Nineteen months ago, Erin and Abby Delaney were dared to operate at the Children's Hospital of Philadelphia to separate their interconnected heads.
The twins are now two and a half years old and live with their parents in Charlotte, NC, a suburb of Mooresville. Heather, 28, and Riley, 25. Girls' weekdays revolve around physical, developmental, linguistic, and other therapies.
How are you? In a word, they thrive, their parents and doctors agree.
"Erin crawls everywhere as if it were her mission," her mother said. "She's starting to get involved in things. She likes to grab the coffee table and reach for the remote control. Abby sits alone and rolls around. Somehow she gets where she wants to be. It's like, if I want that, I understand it. "
On Wednesday, the pigtailed redheads ̵
Publication in a reputed journal is exciting, says reconstructive surgeon Jesse Taylor and neurosurgeon Gregory Heuer, who led the team. But nothing compares to the observation of the steady progress of the twins, who returned to CHOP three times for follow-up examinations.
"I think they are doing much better than we expected. You may have delays, but the separation process is slowing down the development clock, "said Heuer. "We're not sure how good they will be in the end, but that's a good thing, if we do not have any answers [doctors]we feel reasonably good because it tells us the door is wide open."  Heather Delaney with her daughters Erin and Abby at the Children's Hospital of Philadelphia before the twins were separated on June 6, 2017. ” data-src=”http://www.philly.com/resizer/LaXj5BHnJ-rC_CHTb4cB-_Rf-sI=/1400×0/center/middle/arc-anglerfish-arc2-prod-pmn.s3.amazonaws.com/public/MET7ELUJHVFXROOLKHAGCMF3LM.jpg” src=”http://www.philly.com/resizer/ZUy3Xftz1mzztWPAKhU8thFLr-8=/0x10/center/middle/arc-anglerfish-arc2-prod-pmn.s3.amazonaws.com/public/MET7ELUJHVFXROOLKHAGCMF3LM.jpg”/>
Twins melded at the head, known as craniopagus, are the rarest paired pairs that occur in 2.5 million births The World's Most Experienced Craniopagus Surgeon James T. Goodrich at the Montefiore Children's Hospital in New York City pioneered a staged approach in which each quadrant of the brain is operated on for about 10 months.  But Goodrich & # 39; s Twins – including 4-year-old Anias and Jadon McDonald, who were followed by CNN – suffered from persistent wound healing problems and fluid retention called hydrocephalus. Erin and Abby had no such complications.
Shortly after Heather first talked to CHOP when she was about 12 weeks pregnant, Taylor suggested a way to start the breakup. The technique, called distraction osteogenesis, was well established for the correction of cranial deformities, but was never used in the separation of craniopagus. She takes advantage of the paradoxical fact that when a bone is cut and the two ends are slowly and gently pulled apart, the process stimulates bone growth as the tissue attempts to heal.
The twins were just four months old when their skulls were cut at the intersection of the heads. They were equipped with custom padded distraction devices that painlessly pulled their heads apart about seven hundredths of an inch a day for two months.
When the surgeons explained to Inquirer 2017 and now in the journal, this traction served several purposes. It improved the position of the twins' heads, producing additional tissue that was helpful in later reconstructions, and, most importantly, an inch-wide open channel that allowed more favorable access to cranial blood vessels.
These vessels are a major obstacle, even to twins like Erin and Abby, who shared only a small part of the brain. Not only does cranial blood drain off to feed other vital organs, but a twin – in this case Erin – has a disproportionate amount of vessels. The division of this circulatory tissue is particularly risky and potentially debilitating for the mutant twin, in this case Abby.
The doctors decided to separate Erin and Abby at the age of 10 months – younger than any previous Craniopagus twins – in the hope of capitalizing on the resilience or plasticity of infant brains. Theoretically, the team wrote in the journal, this would allow for "a faster and more complete recovery than at an older age".
However, this theoretical advantage had to be weighed against a biological reality: "In infants … even a modest loss of blood can be life threatening."
Originally, the doctors planned to perform a two-stage operation in which the babies were asked three weeks, to heal between treatments. The second stage culminates in the cutting of a large vein, the sagittal sinus, which is a vital channel for blood and cerebrospinal fluid.
However, the first stage was without complications, with minimal blood loss and in less than four hours, "she wrote in the journal. "Therefore, it was decided to continue the separation without delay."
Scientific journals try to be strictly factual and dispassionate, so this seven-hour second stage is simply called "more complicated."
But in 2017, the surgeons said, the race for the tireless blood loss of the twins in this second phase of the operation was a staggering event.
"If Abby's bleeding lasted much longer," said Heuer, "we could have lost her.
In a blog she has shared with the twins since her pregnancy, Heather, a former nanny, confided to one of the hardest parts of her parental journey.  "There is no book to follow," she wrote in September 2018. "I can not read to toddlers what to expect because my toddlers are different."