WEDNESDAY, Dec. 6, 2017 (HealthDay News) -- Two years ago, Zion Harvey was the first child to undergo a successful double hand transplant. Now he's gaining notoriety for another milestone: the way his brain reorganized itself in response to the amputation and transplantation.
Harvey, now 10, lost both hands because of a severe infection in infancy. The brain rewired itself after the amputations -- but reversed those changes after he received his transplanted hands, according to his doctors at Children's Hospital of Philadelphia.
"With the changes observed in his brain, which our collaborative team has been closely evaluating since his transplant two years ago, Zion is now the first child to exhibit brain mapping reorientation," said study senior author Dr. L. Scott Levin. He led the 40-member team that performed the hand transplant.
Each part of the body that receives nerve sensations sends signals to a corresponding site in the brain, Zion's doctors explained in a newly published case study.
Study first author William Gaetz said, "We know from research in nonhuman primates and from brain imaging studies in adult patients that, following amputation, the brain remaps itself when it no longer receives input from the hands."
Brain remapping that occurs after upper limb amputation is called massive cortical reorganization (MCR).
"We had hoped to see MCR in our patient, and indeed, we were the first to observe MCR in a child," Gaetz, a radiology researcher, said in a hospital news release.
"The brain area representing sensations from the lips shifts as much as 2 centimeters to the area formerly representing the hands," he explained.
But Gaetz said they were even more excited to observe what happened next -- when the patient's new hands started to recover function.
"For our patient, we found that the process is reversible," he added.
Using advanced imaging, the researchers measured magnetic activity in Zion's brain to detect the location, strength and timing of his responses to stimuli applied to his lips and fingers. The investigators performed these tests four times in the year following the transplant.
Significant changes were detected in the two later visits that indicated better response time to the stimuli -- a sign that brain remapping was reverting to a more normal pattern.
"The sensory signals are arriving in the correct location in the brain, but may not yet be getting fully integrated into the somatosensory network," said Gaetz. "We expect that over time, these sensory responses will become more age-typical."
Zion has been a child of many firsts at Penn Medicine and across the world, said Levin, director of the hospital's hand transplantation program.
"This is a tremendous milestone not only for our team and our research, but for Zion himself," said Levin. "It is yet another marker of his amazing progress, and continued advancement with his new limbs."
Gaetz said these results have generated new questions and excitement about brain plasticity, particularly in children.
Some of those new questions include, what is the best age to get a hand transplant? Does brain reorganization always occur after amputation? How does brain mapping look in people born without hands?
"We are planning new research to investigate some of these questions," Gaetz said.
As for Zion, he can now write, dress and feed himself more independently than before his operation. These are "important considerations in improving his quality of life," Levin said.
The report was published Dec. 6 in the journal Annals of Clinical and Translational Neurology.
The Amputee Coalition has more on limb loss.