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Arriving at the skull, Bingaman puts down the scalpel. With a high-speed air drill, he cuts a 4-inch-by-4-inch door through the bone. Under that shelter, the brain has only paper-thin protection a gray membrane called the dura. With the scalpel, Bingaman breaches that layer as well.
Once he has pulled up the dura, Bingaman sees his first glimpse of the brain. Healthy brain tissue is a creamy tan, with a texture that's a little softer than Jell-O.
Olivia's brain was different.
Her stroke had burrowed a hole, like a tunnel, that was now filled with clear spinal fluid. Around it, the scar tissue was stiff and ghostly pale. That's the tissue Bingaman was after.
Instead of cutting it out with his scalpel, Bingaman used a device that looks like a small flashlight, which uses ultrasonic waves to dissolve the tissue. Then he sucked the matter out of the brain cavity.
"The brain itself is pretty suckable," he says.
Eager to save any sliver of healthy brain matter, he melted away all but a small section of the frontal lobe. Next, he directed the small tool to the parietal lobe until that tissue disappeared.
Then he moved on to the temporal and occipital lobes. Finally, he came to Olivia's corpus callosum, a complex network that ties a healthy brain's two hemispheres together. Careful not to damage the healthy half, Bingaman snipped that connection; with the right hemisphere gone, Olivia's corpus callosum becomes a biological bridge to nowhere.
He poured saline solution into the now-vacant space on the right side of the cranium. If Olivia was lucky, that space would be constantly replenished by her body's natural production of spinal fluid. If too much fluid built up, she would need a shunt to direct the liquid elsewhere.
Bingaman began to reconstruct the brain's protective layers. He stitched the dura back into place, retrieved the chunk of bone and, with titanium staples, sealed the door in her skull. He replaced her chewing muscle and finally smoothed her scalp back into place.
Downstairs, in a waiting area, the Johnson family watched their buzzer the type that restaurant hostesses hand diners waiting for tables. At 2 p.m., it vibrated.
The surgery was over, but Bingaman couldn't declare it a success.
The only proof would be the passage of time. For a patient who makes it through the first year without seizures, the chances that they will return drop to 10 percent. After five years, the chance becomes almost negligible.
"I can't make that time pass any more quickly," Bingaman says.
He deals with the inner working of the human brain every day. But he's still mystified by it. "It's a huge thing to remove half the brain," he says, "especially because we don't understand how the other side compensates."
But it does. Physicians can tell families like the Johnsons that hemispherectomies work. What they don't know is how the brain reorganizes itself when half its matter has been replaced with spinal fluid and empty space. Schlaggar and his team at Washington University in St. Louis are trying to figure that out.
In the late 19th century, French scientist Paul Broca discovered that a patient with an injury to his left frontal lobe could understand what people were telling him but couldn't form words to respond.
Building on Broca's discovery, Dr. Carl Wernicke, a German neurologist, found that a patient with an injury to his rear parietal lobe had the physical ability to speak but couldn't comprehend language.