A child that received the first successful double hand transplant was also the first whose brain has been seen to remap itself to adapt to the changes, a study reveals.
Zion Harvey, now 10 years old, underwent the procedure in July 2015 at the Children’s Hospital of Philadelphia (CHOP), and has since made a remarkable recovery. A team of 40 people, led by Dr Scott Levin, performed the groundbreaking operation.
However, in this latest study published in the Annals of Clinical and Translational Neurology, scientists show how the child’s brain began remapping itself six years before the operation, when his hands were amputated due to a severe infection.
"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," said first author Dr William Gaetz from CHOP in a statement. "The brain area representing sensations from the lips shifts as much as 2 centimeters to the area formerly representing the hands."
The findings were made using magnetoencephalography (MEG), which measures magnetic activity in the brain when researchers apply sensory stimuli to the lips and fingers. The tests were performed four times on Harvey in the year after his operation, alongside similar tests on five healthy children.
At first, Harvey’s brain incorrectly attributed lip stimulation to the hand area. In the next two visits, however, the MEG signals returned to the lip region, showing that the brain was remapping itself into a more normal pattern.
Brain mapping that occurs after upper limbs have been amputated is called massive cortical reorganization (MCR). This was the first time MCR has been seen in a child. They then found that when the new hands were transplanted, the process reversed.
"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 Dr Levin. “This is a tremendous milestone not only for our team and our research, but for Zion himself. It is yet another marker of his amazing progress, and continued advancement with his new limbs."
The scientists now want to know if MCR always occurs after amputation, and see how such brain mapping occurs in people born without hands.