UPDATE: 10/14/16, 11:45 a.m.: After more than 16 hours of surgery, doctors at Children's Hospital at Montefiore Medical Center separated coinjoined twins Anias and Jadon McDonald, CNN reported. Jadon was wheeled out of the operating room on Friday morning. Doctors were continuing to operate on his brother. Nicole McDonald, the boys' mother, wrote on Facebook that lead surgeon Dr. James Goodrich told the parents, "Well, we did it." 

ORIGINAL STORY:

The McDonald family is about to undergo one of the most turbulent and possibly miraculous medical experiences around — the separation of their conjoined sons, 13-month-olds Anias and Jadon.

As detailed in the video above by CNN’s Dr. Sanjay Gupta, the brothers are joined at the head, making them one of the rarest among even their kind, craniopagus twins. Only about one in every 200,000 live births end in conjoined twins, and craniopagus twins occur only one in every 2.5 million births.

Conjoined twins typically live an uncharmed life. Around half are stillbirths, and a third of survivors don’t make it past the first day, according to the University of Maryland Medical Center. And excluding Anias and Jadon, there are fewer than 12 pairs of such twins living today. Craniopagus twins, in particular, have a hard go of it — only 20 percent survive by age 2 without separation, according to research cited by CNN.

That danger and other health risks has compelled the McDonald family to enlist the help of Dr. James Goodrich, one of the few surgeons in the world to have extensive experience with separating conjoined twins.

"This is about as complicated as it gets," Goodrich told CNN, whose surgical team has turned to 3D virtual models of the twins’ shared head to prep for the difficult procedure. To further ready the twins, Goodrich’s team placed four tissue expanders in their heads so their skin can be stretched and sewn back together following the surgery.

Despite having abandoned their jobs in order to move to New York, and despite the risk of either twin dying or surviving with lasting neurological damage, the McDonalds believe the surgery is the best shot their children have at living a healthy, fulfilled life.

"I'm prepared mentally and emotionally," Nicole McDonald told CNN. "It's just the preparation for that day that is hard."

The boys began their surgery early Thursday morning at the Montefiore Medical Center in Bronx, NY.

For more on the incredible lives conjoined twins lead, check out Medical Daily's extensive feature article.