A boy who lost a large part of his brain to a brain tumor has recovered to a remarkable degree, the rest of his brain having rewired itself to compensate, researchers reported Tuesday.

Surgeons removed a third of one entire lobe of Tanner Collins’ brain to stop seizures caused by a benign brain tumor when he was 6. With it went the entire visual processing center on his right side.

But the remaining part of his brain has adjusted, the team at Carnegie Mellon University in Pittsburgh reported in the journal Cell Reports.

Tanner Collins Courtesy Collins Family

Although he lost the part of his brain that normally processes face recognition, Tanner, now 12, says he recognizes people normally.

“I have definitely been able to adjust,” Tanner told NBC News. “I can recognize faces perfectly.”

Now Tanner, who lives in New Stanton, Pennsylvania, wants to become a neurosurgeon himself.

This type of brain surgery is rare and every patient is different, said Marlene Behrmann, a cognitive scientist who worked on Tanner’s case. With Tanner's regular brain scans, the team watched his brain adapt to losing such an important part of his visual processing.

“We had an unprecedented view of the plasticity at work,” Behrmann told NBC News.

The tumor was on the right side of Tanner’s brain. “I vomited a lot and I had the worst headaches,” Tanner recalled. Then he had a “full-blown seizure,” Tanner’s father, Carl Collins, said. It wasn’t until then that the family even knew he was having seizures, or that a brain tumor was the cause.

The family had a choice: allow surgeons to remove a third of Tanner’s right brain lobe to get the tumor out and maybe ease the seizures, or watch and wait to see what happened.

“We wanted to remove the tumor and still keep Tanner at the same time,” said Collins, who as a nurse understood the risks. “Losing that much brain, we were nervous.”

The part of the brain that was removed accounts for much of a person's visual processing, Behrmann said.

“The visual system in the right hemisphere carries the burden of face recognition,” she said. “The left hemisphere carries the function of recognizing words.”

So while Tanner lost none of his eye function, a large part of the brain that interprets the input was gone.

“In Tanner’s case we saw that the left hemisphere sort of stepped up to the plate,” Behrmann said. “It took on not only word recognition but it also assumed the function for face recognition.”

Much of his visual field disappeared, too.

“I kept running into walls,” Tanner said.

That adjustment was easier, even though that is a permanent loss. Although he lacks peripheral vision on one side, he can move his eyes and head to compensate.

Now Tanner plays chess and volleyball, collects coins and swims. His IQ is above average, his doctors said, and he’s preparing to start seventh grade in a few weeks.

“I can do everything everyone else can for the most part. My parents think I have made a miraculous recovery,” Tanner said.

“It’s almost like it never happened. He is your normal, average 12-year-old,” added his father. The only thing he won’t be able to do is drive. But his brothers and sisters have vowed to drive him around for the rest of his life.”