Date: July 10, 2010
All the while teens are lolling in Starbucks, drinking lattes, their brains are being pruned. Unneeded neurons fade away, leaving room for the great meet-and-greet of white matter that develops as fibers from remaining cells make new contacts. Millions of them.
The changes underlie the switchover to the quickened mental processing, the ability to multitask and plan that mark adult thinking.
“It’s an especially unfortunate time, however, to be treated for a brain tumor,” says pediatric neuropsychologist Mark Mahone who knows whereof he speaks. For some two decades, Mahone and his colleagues have assessed cognitive and other abilities in children at various ages, after they’ve received combinations of surgery, chemotherapy or radiation for brain tumors or leukemia.
It’s the sort of work that, in the 1980s, led Hopkins—and then other hospitals—to phase out whole-brain radiation for children as a primary leukemia therapy.
Today, radiation use is far more judicious, thanks to the sharper focus and lowered dosage that new technology allows. Chemotherapy is also advancing. But, says Mahone, he still wrestles with basic questions. Mahone is with both Hopkins Psychiatry and the Kennedy Krieger Institute.
The literature on children receiving chemotherapy or cranial radiation isn’t conclusive, he says. Young patients vary greatly—by age, background, overall health, their tumor’s location, its aggressiveness, therapy dosage and its route of delivery, presence of seizures or other complications—and that makes large-scale research on identical groups a challenge. “Studies can also be more complicated than in adults,” he says, “because children’s brains are developing.” Still Mahone and colleagues advance understanding.
“I couldn’t tell you today, for example, if a particular 12-year-old child receiving radiation for a brain tumor would definitely suffer from a loss of skill in, say, three years.”
But Mahone’s research on radiation shows a pattern that guides prediction: After an initial, not-unexpected dip in cognitive and motor function, patients gain some skills back roughly a year later. “But when you follow children farther out,” he says, “you see that, unlike with chemotherapy, there’s a continued skill loss in some of them.”
“Brain growth is essentially interrupted,” says Mahone, and effects can surface with each new developmental demand. That’s why treatment at puberty is especially fraught with decisions.
“Still, we have enough certainty to give a family a sense of what struggles lie ahead and what we can do to help, Mahone says.
“My clinical role is in assessment,” he explains. “It’s testing to be able to tie a child’s medical and neurological condition to what he or she can do bodily, mentally and socially. If we know, for example, that motor skills, working memory or attention are the main issues, we have behavioral approaches that can make a difference.”
A child who’s had chemotherapy in first grade might show memory problems, but it’s not so bad because nobody expects him then to remember all he’s read. It will be a problem when he gets to fourth grade, though, and Mahone can alert both family and the rehab team to begin working on memory strategies.
A family’s relief at having understanding and a plan, he says, is often almost palpable.
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