“How the Brain Can Rewire Itself After Half of It Is Removed: New Scans Showed How the Brains of People Who Had a Hemisphere Removed in Childhood Continue to Function”, 2019-11-19 (; backlinks; similar):
Her son, Henry, endured hundreds of seizures a day. Despite receiving high doses of medication, his little body seemed like a rag doll as one episode blended into another. He required several surgeries, starting when he was 3 1⁄2 months old, eventually leading to a complete anatomical hemispherectomy, or the removal of half of his brain, when he turned 3. The procedure was first developed in the 1920s to treat malignant brain tumors. But its success in children who have brain malformations, intractable seizures or diseases where damage is confined to half the brain, has astonished even seasoned scientists. After the procedure, many of the children are able to walk, talk, read and do everyday tasks. Roughly 20% of patients who have the procedure go on to find gainful employment as adults.
Now, research published Tuesday in the journal Cell Reports suggests that some individuals recover so well from the surgery because of a reorganization in the remaining half of the brain. Scientists identified the variety of networks that pick up the slack for the removed tissue, with some of the brain’s specialists learning to operate like generalists. “The brain is remarkably plastic”, said Dorit Kliemann, a cognitive neuroscientist at the California Institute of Technology, and the first author of the study. “It can compensate for dramatic loss of brain structure, and in some cases the remaining networks can support almost typical cognition.”
…Instead, researchers found that while the type of connections remained the same in the individuals with just one hemisphere, different regions responsible for processing sensorimotor information, vision, attention and social cues strengthened existing connections, communicating more frequently with each other compared with ordinary brains. It was almost as if parts of the brain that may have normally been specialized, say, as trumpet players, had talked to the rest of the band and taken additional responsibilities to play percussion instruments as well, Dr. Behrmann said. “Their brain networks seem to be multitasking.”
The results are encouraging for researchers and families trying to understand how the brain adapts and functions after a hemispherectomy. “I think there’s more and more evidence to suggest that brain plasticity is a really long-lasting phenomena”, said Dr. Ajay Gupta, a pediatric neurologist at the Cleveland Clinic, who has followed nearly 200 children after the surgery. Until recently, the scientific consensus has been that hemispherectomy surgery is best performed at a very young age, before a child reaches the age of 4 or 5. That way, they can regain normal function as they grow older. While neuroplasticity is stronger in early childhood, the new study suggests that surgery should not be withheld after an arbitrary end date, Dr. Gupta said. Adults in the study had undergone hemispherectomy surgery at ages ranging from 3 months to 11 years old.
A factor that may play a more important role in patient outcomes is the age at which seizures begin to occur. The surgery is still considered a last resort after medical treatment. But if the duration of seizures and resulting brain damage can be limited, patients may recover more function. “The other hemisphere is already having to handle extra responsibilities before patients get treated”, said Lynn K. Paul, a neuroscientist at California Institute of Technology and a co-author of the study. “It continues to do so when you take out the damaged hemisphere. So what we really want is to protect the hemisphere that’s working.”
…After the operation, children become substantially weaker in their hands and arms on the side opposite the operation. Their vision becomes blocked on that side, and they may also lose some ability to recognize where sounds are coming from. “There are some things that definitely require a higher level of rehab and learning. For example, reading and writing and math”, Dr. Gupta said. In many cases, however, those skills have already been compromised by the underlying diseases…For now, she is happy that her son can walk independently, communicate with an iPad and eat meals without a feeding tube.