A 56-year-old US man, recovering after hand transplant, is offering scientists new lessons in the adaptability of human brain.
David Savage has lived most of his life with a hook in place of a right hand.
It was 37 years ago that his hand was mangled in a metal-stamping machine, and doctors had to amputate.
"It's like you're waking up from a bad dream," he says. "You've had this dream all night long, you know, like you're falling or whatever. And you wake up and you're just laying in bed. It's that kind of feeling."
Savage's new hand is still gaining strength, but he can swing a hammer with it, and he can throw a football or baseball. "I couldn't do that with a hook," he says. He can now turn doorknobs and do "the everyday things in life."
Savage's story is remarkable enough, but he's also teaching scientists remarkable new things about the adaptability of the human brain, Richard Knox said on NPR radio station.
When a limb is amputated, the parts of the brain that control it and register feeling — hot and cold, pressure and pain — go blank. It's almost like deleting a computer program. Gradually, the brain uses that empty real estate for other things. Animal studies suggest the part of the brain that registers sensation in the face often expands to the area devoted to a missing limb.
Experts have long assumed that this brain reorganization is irreversible, especially years after an amputation. But Savage is proving them wrong.
Neuroscientist Scott Frey of the University of Oregon is using magnetic resonance scanning to study Savage's brain. The first results are in the Oct. 14 issue of the journal Current Biology.
Frey says shortly after Savage's hand transplant, his brain began remapping itself — again. The brain area responsible for sensation in his original right hand is performing the same function for the new hand.
"What was remarkable is really that after 35 years of complete deprivation, this sensory map of the hand could be that reversible in a mere four months after a hand transplant," Frey says.
Savage is only one patient, and many more studies will be needed to confirm the results, but researchers think the fact that Savage's middle-aged brain could rewire itself this way has big implications. Frey says it could point the way toward better artificial limbs.
"We're entering a really exciting era right now where the ability to marry technology to the human brain is becoming a very real thing," Frey says.
Frey thinks the brain's newfound adaptability might lead to prostheses that function more naturally, and maybe even have a sense of touch.
Dr. Warren Breidenbach, the surgeon at Jewish Hospital in Louisville, Ky., who did Savage's hand transplant — as well as the other three done so far in the U.S. since 1999 — sees other implications in Savage's brain scans.
"It means that a stroke victim who has lost the ability to function could possibly recapture it, as long as the brain was not scarred or actually dead tissue," he says.
Scientists don't know yet why Savage's brain has responded to the hand transplant, while other patients with either brain or limb injuries have not responded as well to rehabilitation. Frey thinks it may have something to do with the intensive, long-lasting physical therapy that hand-transplant patients get.
"There's a real revolution taking place right now in the way we think about the capacity of a fully developed brain to reorganize itself," Frey says. "Those insights are starting to penetrate the world of rehabilitation."
Breidenbach thinks the brain's ability to adapt might one day open a door for people born without a hand, a relatively common congenital defect.
"Here's the question: If someone is born without a hand and I put a new hand on, will they be able to feel?" he says. "The first step of answering that question will be doing patients like Mr. Savage."
Researchers may soon have more patients like Savage to study. So far, 44 hands have been transplanted around the world, almost all with good results. Breidenbach says other U.S. centers are gearing up to do more.
One reason may be the growing number of military amputees — it's no accident that much of this research is funded by the Department of Defense.