From the Scientific American Sidebar (May 24, 2007): Strange but True: When Half a Brain Is Better than a Whole One, by Charles Choi
The operation known as hemispherectomy — where half the brain is removed — sounds too radical to ever consider, much less perform. In the last century, however, surgeons have performed it hundreds of times for disorders uncontrollable in any other way. Unbelievably, the surgery has no apparent effect on personality or memory…
One side effect Canadian neurosurgeon Kenneth McKenzie reported in 1938 after a hemispherectomy on a 16-year-old girl who suffered a stroke was that her seizures stopped. Nowadays, the surgery is performed on patients who suffer dozens of seizures every day that resist all medication, and which are due to conditions that mostly afflict one hemisphere…
Most Hopkins hemispherectomy patients are five to 10 years old. Neurosurgeons have performed the operation on children as young as three months old. Astonishingly, memory and personality develop normally. A recent study found that 86 percent of the 111 children who underwent hemispherectomy at Hopkins between 1975 and 2001 are either seizure-free or have nondisabling seizures that do not require medication. The patients who still suffer seizures usually have congenital defects or developmental abnormalities, where brain damage is often not confined to just one hemisphere, Freeman explains.
Another study found that children that underwent hemispherectomies often improved academically once their seizures stopped. “One was champion bowler of her class, one was chess champion of his state, and others are in college doing very nicely,” Freeman says.
Of course, the operation has its downside: “You can walk, run—some dance or skip—but you lose use of the hand opposite of the hemisphere that was removed. You have little function in that arm and vision on that side is lost,” Freeman says.
Remarkably, few other impacts are seen. If the left side of the brain is taken out, “most people have problems with their speech, but it used to be thought that if you took that side out after age two, you’d never talk again, and we’ve proven that untrue,” Freeman says. “The younger a person is when they undergo hemispherectomy, the less disability you have in talking. Where on the right side of the brain speech is transferred to and what it displaces is something nobody has really worked out.”…
