Hemispherectomy

Hemispherectomy 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.

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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 disconnected.

Results

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 as well.

This procedure is almost exclusively performed in children, since 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.^[1] One case, demonstrated by Smith & Sugar, 1975; A. Smith 1987, showed that one patient with this procedure had completed college, had attended graduate school and scored above average on intelligence tests. Studies have found no significant long-term effects on memory, personality, or humour after the procedure^[2], and minimal changes in cognitive function overall.^[3] Generally, the greater the intellectual capacity of the patient prior to surgery; the greater the decline. Most patients end up with a mild to severe mental retardation, although this usually constitutes no change to intellectual function before surgery. When resection of the left hemisphere, there is some evidence indicating that some advanced language functions (i.e. higher order grammar) cannot be entirely assumed by the right side. The extent of this however being somewhat dependant of age at surgery.^[4]

In the Media

A hemispherectomy is performed on a patient played by Dave Matthews in the Season 3 episode of House, M.D., "Half Wit." His right hemisphere was severely damaged in a car accident when he was 10 years old.

In the Season 1 episode called "The Self-Destruct Button" on Grey's Anatomy, Dr. Shepherd performs a hemispherectomy on a 2 year old girl with a seizure disorder.

References

See also

• Rasmussen's encephalitis

Further reading

• Antonio M. Battro (2001). Half a Brain is Enough : The Story of Nico. Cambridge University Press.  (ISBN 0-521-78307-0)
• Christine Kenneally (July 3, 2006). "The Deepest Cut". The New Yorker.