Conjoined twins attached at head separated after surgery in New York

NEW YORK -- Doctors in the Bronx have finished a rare operation to separate conjoined twin boys who were attached at the head.

One-year-olds Jaden and Anais McDonald from Illinois were sharing brain tissue nearly an inch in diameter. The boys' mother posted updates on Facebook Friday morning:

The risky surgery started early Thursday at the children's hospital at Montefiore Medical Center. Doctors told WABC-TV that the operation ended shortly after 2 a.m. Friday - the boys then underwent individual surgery.

It took a little longer for Anais, but his mother posted to Facebook later in the day saying he was out of surgery.

Anias and Jadon's birth was rare; science says the boys are one in millions.

They were moved from their hospital room on the 10th floor to the operating room around 7:15 a.m. on Thursday. Their 3-year-old brother Aza rode on the gurney with them, leading up to the OR, where mom and dad gave them a kiss.

It is the culmination of a 13-month journey that brought the McDonald family from Illinois to the Bronx. The twins had three preliminary operations to prepare them for the big day.

As is often the case with conjoined twins, one is stronger than the other. Anias has suffered a number of problems, including heart failure and seizures.

At 13 months, Jadon is described as the rambunctious one. He runs in place and tries to roll off the bed to get away from his brother. When his brother plays with a toy, Jadon rocks back and forth until he can snatch it away.

Anias is the contemplative one who loves listening to his mom read. He's struggled more in infancy than his brother. He is the silent warrior, his mother says, with a gaze so captivating it's as if "he looks at your soul."

Their surgery lasted 20 hours - all with the hope two healthy boys will return together, but forever separated.

At the invitation of the McDonald family and Montefiore hospital, CNN was given exclusive access to the remarkable and rare journey of Jadon and Anias. You can see the full story on CNN.com.

The surgeon leading the operation is Dr. James Goodrich. Considered by many to be the world's leading neurosurgeon for twins conjoined at the head, he hoped to become the man successfully separated Jadon and Anias.

"This is about as complicated as it gets," Goodrich said while holding 3-D printed models of the boys' conjoined brains.

State of the art renderings have provided a guide for the medical staff as they worked to separate the boys' brains at the most crucial spot: a 2-inch area shared by both.

Twins joined at the head, called craniopagus twins, are exceedingly rare, occurring in one out of every 2.5 million births. About 40 percent of the twins are stillborn, and another one-third die within 24 hours of birth. Studies have shown 80 percent of twins joined at the head die of medical complications by the age of 2 if not separated.

Simply making it to this point has been quite a feat for the McDonald boys, who share 1.5 to 2 inches in diameter of brain tissue. While meaningful statistics are hard to gather with something so rare, it is safe to say the separation procedure carries major risks, including the possibility of death or long-term brain damage for one or both boys.