When Sierra and Dustin Yoder of Ohio went for a routine prenatal ultrasound, they were in for a shock. Their son Bentley had an encephalocele, meaning a large portion of his brain was growing outside his skull. He wasn't expected to live past birth.

But Bentley came out kicking and surprised all his doctors by thriving and meeting most of his baby milestones. Except for one: The large protuberance on his head was preventing him from holding his head up for more than a few seconds. And it was getting larger. Local neurosurgeons wanted to remove the encephalocele, but Sierra wondered, "What if he's using what's up there?"

When the Yoders eventually found their way to Boston Children's Hospital, the surgeons agreed with her. Bentley's displaced brain tissue couldn't be cut off: It was alive and working. The team developed a plan to ease the tissue back inside Bentley's skull, helped by intricate 3D-printed models of his brain, skull and the encephalocele itself — all with the touch and feel of the real thing. Prepared for any possible complication, the team successfully removed the encephalocele. Today, one year later, Bentley is doing well and just went on his first family vacation to Florida.