Boston brain surgeon Ed Smith points to a tangle of delicate gray shadows on his computer screen. It's an X-ray of the blood vessels on the left side of 13-year-old Maribel Ramos' brain.
"If we follow this blood vessel up here, you see that right there it gets pinched off almost to nothing," Smith explains, "and then this little puff of smoke right here, which are these little narrow blood vessels that don't fill the rest of the brain as it normally should." Maribel's brain is starved for oxygen, he says.
Those spidery blood vessels represent an effort by the girl's body to compensate for the pinched section of her major cerebral artery. In fact, "puff of smoke" is the actual name of Maribel's disorder — "moyamoya" in Japanese — because the researchers who named it thought that's what it looked like on X-rays.
The disorder is just one of many conditions that can make a child more prone to strokes. One in 10,000 kids will suffer a stroke, causing disability or even death. But surgeons can now prevent strokes in some of these children — children like Maribel.
Moyamoya is not Maribel's only health condition. She also suffers from sickle cell disease, a much more common disorder that causes red blood cells to be spiky and misshapen — and prone to form blood clots in the dangerously narrow blood vessels of her brain. Sickle cell disease is the most common cause of strokes in children.
Smith, who works at Children's Hospital in Boston, says the combination gives Maribel a 95 percent chance of suffering a disabling or possibly fatal stroke. In fact, a few months ago she suffered a warning stroke.
"My legs started to get numb and my tongue got numb and my hands were shaking a lot," she says. "I did not know what was going on."
Fortunately, that stroke didn't leave her with lasting damage. But it heightened the urgency for an operation that Smith is preparing to do to stave off the almost inevitable.
Maribel's father, Luis Ramos, says they didn't hesitate to have the surgery Smith proposes. "We just want to fix it," he says. "We want to do whatever we can so it doesn't happen again. It's very scary."
Smith aims to give Maribel's brain a new blood supply.
It's an ingenious bit of surgery. He plans to take a fat, healthy blood vessel that now runs up the outside of Maribel's skull and reroute it so it's next to the section of her brain that's chronically starved for blood.
Once Maribel is asleep, Smith shaves a section of scalp behind her left ear and takes up a pencil-like wand. It uses ultrasound waves to locate the blood vessel, lying beneath skin and muscle, that Smith plans to use. He takes a marker and traces the vessel's path on her scalp so he knows exactly where it runs from her ear to the top of her head.
Next, Smith and surgeon Sarah Jernigan sit down next to Maribel's head and peer through a big microscope. Painstakingly, they slice through scalp and muscle. The pulsing artery comes into view.
Rare as moyamoya is, Smith operates on a child with the disease about once a week. And, much more often, doctors at Children's and other major pediatric hospitals see children suffering strokes for different reasons: other malformations of blood vessels in the brain; too little oxygen during birth; congenital heart defects; infections like meningitis and chickenpox. The cause is unknown in one-third of childhood strokes.
Pretty much every midsize town in America has at least one child who has suffered a stroke, Smith says as he works on Maribel. And the problem is growing.
"One of the newer conditions, unfortunately, that we think is becoming increasingly a cause for stroke in kids is the same cause that affects adults — obesity," he adds. "Kids are getting ... diabetes, blood pressure problems."
Finally, the surgeons have freed up the blood vessel that will be redirected underneath Maribel's skull to her oxygen-starved brain tissue. It looks like a jump rope that's 5 inches long. The ends are still attached and the middle part is free.
"That's the part we're going to swing under a piece of bone to put it in contact with the brain," Smith explains as he starts what he calls "the construction work."
"Kind of like digging a trough in the middle of downtown Boston," he says as he removes a section of Maribel's skull the diameter of a hockey puck. "It allows us to get this blood vessel where it's needed."
The blood vessel needs to be in direct contact with the brain. That involves removing the innermost protective layer, a cobwebby membrane called the arachnoid. When that's done, there it is: Maribel's exposed brain.
Next, Smith sews the blood vessel to the surface of the brain. This is the real key to the operation. Once the artery is in contact with the brain, it will start putting down new blood vessels, like roots from a tree.
"It's remarkable how quickly the brain can respond favorably to this graft when it really needs one," Smith says. In a sense, he's enabling Maribel's body to cure her moyamoya disease.
Once the new blood vessel is sewn firmly in place, the surgeons reverse course, carefully replacing layers of tissue one by one. Smith replaces the circle of bone, using tiny screws to fix it in place. He leaves two small holes so the rerouted artery can dive under Maribel's skull and exit on the other side. Finally, the soft tissue is replaced and the incision neatly sutured up.
"So, guys, we're done," he announces. And a few minutes later, Maribel is awake again — more or less.
"Hey, Maribel, hey, sweetie, it's Dr. Smith," he says. "Wiggle your toes, sweet pea. That's a good girl."
A few weeks later, I visit Maribel at home in Nashua, N.H. She's wearing an elaborate bow to hide the place where her hair hasn't grown in yet.
Her father says a recent MRI scan brought good news. "It was, what, two, three weeks after surgery, and you could already see the new veins growing into the brain," Luis Ramos says. "Everything looks good."
And now, instead of an almost 100 percent chance of a major stroke, Smith says Maribel's risk has been reduced drastically, to around 5 percent.
Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.