is a surgical procedure
where one cerebral hemisphere
(half of the brain
) is removed or disabled. This procedure is used to treat a variety of seizure disorders where the source of the epilepsy is localized to a broad area of a single hemisphere of the brain. It is solely reserved for extreme cases in which the seizures have not responded to medications and other less invasive surgeries.
History and changes
Hemispherectomy was first tried on a dog in 1888 by Friedrich Goltz
. The first such operation on humans was done by Walter Dandy
in 1923. In the 1960s and early 1970s, hemispherectomy involved removing half of the brain, but this resulted in unacceptable complications and side effects in many cases, like filling of excessive body fluids in the skull and pressuring the remaining lobe (known as hydrocephalus
). Today, the functional hemispherectomy
has largely replaced this procedure, in which only the temporal lobe
is removed; a procedure known as corpus callosotomy
is performed; and the frontal
and occipital lobes
All hemispherectomy patients suffer at least partial hemiplegia
on the side of the body opposite the removed or disabled portion, and may suffer problems with their vision
This procedure is almost exclusively performed in children because their brains generally display more neuroplasticity, allowing neurons from the remaining hemisphere to take over the tasks from the lost hemisphere. This likely occurs by strengthening neural connections which already exist on the unaffected side but which would have otherwise remained small in a normally functioning, uninjured brain.
One case, demonstrated by Smith & Sugar, 1975; A. Smith 1987, demonstrated that one patient with this procedure had completed college, attended graduate school and scored above average on intelligence tests. Studies have found no significant long-term effects on memory, personality, or humor after the procedure, and minimal changes in cognitive function overall. Generally, the greater the intellectual capacity of the patient prior to surgery, the greater the decline in function. Most patients end up with mild to severe mental retardation, which is usually already present before surgery. When resectioning the left hemisphere, evidence indicates that some advanced language functions (i.e., higher order grammar) cannot be entirely assumed by the right side. The extent of advanced language loss is often dependent on the patient's age at the time of surgery.
- Antonio M. Battro (2001). Half a Brain is Enough : The Story of Nico. Cambridge University Press. (ISBN 0-521-78307-0)
- Christine Kenneally "The Deepest Cut". The New Yorker 36–42.
- Charles Q. Choi (2008). "Do You Need Only Half Your Brain?". Scientific American 298 (3): 104.