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How the brain can reward itself after half of it is removed



Shortly after the birth of her first son, Monika Jones was told that he had a rare neurological condition that made a side of his brain abnormally large. Her son Henry endured hundreds seizures per day. Despite receiving large doses of medication, his small body seemed like a rag doll when one episode was mixed into another. He required multiple surgeries, starting when he was 3 1/2 months old, which eventually led to a complete anatomical hemispherectomy, or the removal of half of his brain when he turned 3.

The procedure was first developed in the 1

920s for to treat malignant brain tumors. But the success of children with brain malformations, severe seizures or illnesses where injuries are limited to half the brain has surprised even experienced researchers. Following the procedure, many of the children can walk, talk, read and do everyday tasks. About 20 percent of patients who have the procedure continue to find profitable employment as adults.

Now, research published Tuesday in the journal Cell Reports shows that some individuals are recovering so well from the surgery due to a reorganization in the remaining half of the brain. Researchers identified the various networks that take up slack for the removed tissue, with some of the brain's specialists learning to function as generalists.

"The brain is remarkably plastic," says Dorit Kliemann, a cognitive neuroscientist at the California Institute of Technology and the study's first author. "It can compensate for a dramatic loss of brain structure, and in some cases the remaining networks can support almost typical cognition."

The study was partially funded by a nonprofit organization that Ms. Jones and her husband set up to advocate for others in need of surgery to stop seizures. The study's findings may provide encouragement for those seeking hemispectomies beyond early childhood.

When individuals who had hemispectomies came to have their brains scanned for the study, they appeared to behave like other commonly developed adults, shaking Dr. Kliemann's hands and small talk. But the results of magnetic resonance, or MRI, showed that individuals had half of their brains removed during childhood.

"When we looked at their brain scans, we would go," Wow, this brain really shouldn't "can't work," says Ralph Adolphs, a cognitive neuroscientist at the California Institute of Technology and co-author of the study. take any other system that has a number of parts whose functions all depend on each other, like the heart, and you split it in half it won't work. You take my laptop and cut it in half, it won't work. "

Most brain networks use both hemispheres to function, for example facial recognition involves both sides of the cerebral cortex, other skills, such as the ability to move the limbs, are processed by opposite sides of the brain. The right hemisphere controls the movement on the left side of the body. the left hemisphere controls the right arm and leg.

"It's like you need all the different members of a band to play together to get sewn synchronized and coherent music, "said Marlene Behrmann, a cognitive neuroscientist at Carnegie Mellon University, who was not involved in the study.

Instead, researchers found that although the type of connections remained the same in individuals with only a hemisphere, different regions responsible for processing sensorimotor information, vision, attention, and social cues strengthened existing connections, communicated more frequently to each other than ordinary brains. .

It was almost as if parts of the brain that would normally have specialized, say, as trumpet players, had talked to the rest of the band and taken additional responsibility for playing percussion as well, Dr. Sa Behrmann. "Their brain network seems to be multitasking."

The results are encouraging for researchers and families trying to understand how the brain adapts and functions after a hemispectomy.

"I believe there is more and more evidence to suggest that the plasticity of the brain is a really long-lasting phenomenon," said Dr. Ajay Gupta, a pediatric neurologist at the Cleveland Clinic who has followed nearly 200 children after surgery. [19659003] Until recently, the scientific consensus has been that hemispectomy surgery is best performed at a very young age, before a child turns 4 or 5. This allows them to regain normal function as they age, while neuroplasticity is stronger in early childhood, suggests said the new study that surgery should not be held after an arbitrary end date, said Dr. Gupta. Adults in the study had undergone hemispectomy surgery in ages ranging from 3 months to 11 years.

A factor that may play a more important role in the patient's result is the age at which the onset of seizure occurs. The operation is still considered as a last resort after medical treatment. brain damage can be limited, patients can have more function.

"The other hemisphere must already deal with extra responsibility before treating patients," said Lynn K. Paul a neuroscientist at the 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 working hemisphere. "

Eight hours of operation is not without risks. Brain tissue must be carefully removed, one section at a time, Dr. Gupta. If even a small fiber remains, it can eventually lead to cramping again and affect the healthy side of the brain. There is also a risk of continued headache and fluid buildup in the brain.

After the operation, children become much weaker in their hands and arms on the side opposite the surgery. Their vision is blocked on that side, and they may also lose some ability to recognize where sound comes from. “There are some things that definitely require a higher level of rehabilitation and learning. For example, reading and writing and math, "Dr. Gupta said.

However, in many cases, these skills have already been compromised by the underlying diseases.

Mrs. Jones hopes to further research, and after more patients over time, will help researchers understand how the brain develops and organizes, so that information can help inform targeted efforts for a wide range of individuals with brain injuries and diseases.

now she is happy that her son can walk independently, communicate with an iPad and eating meals without feeding tubes.

"He really loves McDonalds," she said.


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