Brain remaps itself in child with double hand transplant

December 6, 2017
Credit: CC0 Public Domain

The first child to undergo a successful hand transplant also is the first child in whom scientists have detected massive changes in how sensations from the hands are represented in the brain. The brain reorganization is thought to have begun six years before the transplant, when the child had both hands amputated because of a severe infection during infancy. Notably, after he received transplanted hands, the patient's brain reverted toward a more typical pattern.

Each area of the body that receives nerve sensations sends signals to a corresponding site in the . The spatial pattern in which those signals activate the brain's neurons is called somatosensory representation—particular parts of the brain reflect specific parts of the body.

"We know from research in nonhuman primates and from brain imaging studies in adult that, following amputation, the brain remaps itself when it no longer receives input from the hands," said first author William Gaetz, PhD, a radiology researcher in the Biomagnetic Imaging Laboratory at Children's Hospital of Philadelphia (CHOP). "The brain area representing sensations from the lips shifts as much as 2 centimeters to the area formerly representing the hands."

This 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," said Gaetz. "We 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."

Researchers from Children's Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania published their findings today in the Annals of Clinical and Translational Neurology. Their case report described Zion Harvey, now 10 years old, who received worldwide media coverage two years ago as the first child to undergo a successful .

A 40-member team led by L. Scott Levin, MD, FACS, chairman of Orthopaedic Surgery and a professor of Plastic Surgery at Penn Medicine, and director of the Hand Transplantation Program at CHOP, performed that milestone surgery in July, 2015 at CHOP. "Zion has been a child of many firsts here at Penn Medicine and Children's Hospital of Philadelphia, and across the world," said Levin, senior author of the paper. He added, "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. 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 researchers used magnetoencephalography (MEG), which measures magnetic activity in the brain, to detect the location, signal strength and timing of the patient's responses to sensory stimuli applied lightly to his lips and fingers. They performed MEGs four times in the year following the bilateral transplant, performing similar tests on five healthy children who served as age-matched controls.

At the first two visits, the patient's finger tips did not respond to tactile stimulation—being touched with a thin filament. When experimenters touched the patient's lips, the MEG signal registered in the hand area of the brain's cortex, but with a delay of 20 milliseconds compared to controls. At the two later visits, MEG signals from lip stimulation had returned to the lip region of the brain, with a normal response time—an indication that brain remapping was reverting to a more normal pattern.

When experimenters touched the patient's fingertips in the two later visits, the MEG signals appeared in the hand region of the brain, with a shorter delay in response time from visit 3 to visit 4, but with higher-than-normal signal strength. "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."

Gaetz added, "These results have raised many new questions and generated excitement about brain plasticity, particularly in children. Some of those new questions include, what is the best age to get a hand transplant? Does MCR always occur after amputation? How does brain mapping look in people born without hands? Would we see MCR reverse in an adult, as we did in this patient? We are planning new research to investigate some of these questions."

In the meantime, follow-up studies of this patient provide encouraging details on his functional abilities. "Our follow-up studies 18 months after this transplant showed that he is able to write, dress and feed himself more independently than before his operation— important considerations in improving his quality of life," said Levin.

Explore further: World's first child hand transplant a 'success'

More information: Annals of Clinical and Translational Neurology, DOI: 10.1002/acn3.501

Related Stories

World's first child hand transplant a 'success'

July 19, 2017
The first child in the world to undergo a double hand transplant is now able to write, feed and dress himself, doctors said Tuesday, declaring the ground-breaking operation a success after 18 months.

Boy with double-hand transplant's next goal: Play football (Update)

August 23, 2016
It's been just over a year since 9-year-old Zion Harvey received a double-hand transplant, and he said Tuesday what he really wants to do is play football.

Cortical nerve function in former amputees remains poor decades after reconstructive surgery

April 12, 2017
Researchers have found that the nerve cells (neurons) controlling sensation and movement of the hands show injury-induced changes for years after hand amputation, reattachment or transplant. The small study, the first of ...

Boy who lost limbs to infection gets double-hand transplant

July 28, 2015
Surgeons in Philadelphia have performed a double-hand transplant on a boy believed to be the youngest patient to undergo the procedure.

Child with double-hand transplant throws at Camden Yards

August 3, 2016
A boy who underwent a double-hand transplant last summer has shown off his progress by throwing out the ceremonial first pitch at Camden Yards.

First-of-its-kind study shows how hand amputation, reattachment affect brain

May 24, 2017
When a person loses a hand to amputation, nerves that control sensation and movement are severed, causing dramatic changes in areas of the brain that controlled these functions. As a result, areas of the brain devoted to ...

Recommended for you

Gene mutation causes low sensitivity to pain

December 13, 2017
A UCL-led research team has identified a rare mutation that causes one family to have unusually low sensitivity to pain.

Activating MSc glutamatergic neurons found to cause mice to eat less

December 13, 2017
(Medical Xpress)—A trio of researchers working at the State University of New York has found that artificially stimulating neurons that exist in the medial septal complex in mouse brains caused test mice to eat less. In ...

Scientists discover blood sample detection method for multiple sclerosis

December 13, 2017
A method for quickly detecting signs of multiple sclerosis has been developed by a University of Huddersfield research team.

LLNL-developed microelectrodes enable automated sorting of neural signals

December 13, 2017
Thin-film microelectrode arrays produced at Lawrence Livermore National Laboratory (LLNL) have enabled development of an automated system to sort brain activity by individual neurons, a technology that could open the door ...

Intermittent fasting found to increase cognitive functions in mice

December 12, 2017
(Medical Xpress)—The Daily Mail spoke with the leader of a team of researchers with the National Institute on Aging in the U.S. and reports that they have found that putting mice on a diet consisting of eating nothing every ...

Discovery deepens understanding of brain's sensory circuitry

December 12, 2017
Because they provide an exemplary physiological model of how the mammalian brain receives sensory information, neural structures called "mouse whisker barrels" have been the subject of study by neuroscientists around the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.