Hemispherectomy is a very rare 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, among other disorders. It is solely reserved for extreme cases in which the seizures have not responded to medications and other less invasive surgeries. Hemispherectomy is considered the most invasive surgical operation in use today, although not the most dangerous.
History and changes 
Hemispherectomy was first tried on a cat in 1888 by Friedrich Goltz. The first such operation on humans was done by Walter Dandy in 1923 for glioblastoma multiforme. 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, predominantly filling of excessive body fluids in the skull with subsequent pressure to the remaining brain (known as hydrocephalus). The procedure was revitalized in children in the 1980s by Dr. Ben Carson at The Johns Hopkins Hospital. In many centers, this procedure has largely been replaced by the functional hemispherectomy, in which the temporal lobe is removed, a procedure known as corpus callosotomy is performed, and the frontal and occipital lobes are disconnected from the rest of the brain. However the traditional "anatomic" hemispherectomy has remained a viable procedure, due to its superiority in preventing future seizures compared with functional hemispherectomy.
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 resecting the left hemisphere, evidence indicates that some advanced language functions (e.g., 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.
Although initially thought to be limited solely to children, a recent study in 2007 by Dr. Shearwood McClelland III and Dr. Robert E. Maxwell indicated the long-term efficacy of anatomic hemispherectomy in carefully selected adults, with seizure control sustainable over multiple decades.
Traumatic hemispherectomy 
There are cases where a person that received major trauma to one side of the brain, such as a gunshot wound, has required a hemispherectomy and survived. The most notable case is that of Ahad Israfil, who lost the right side of his cerebrum in 1987 in a gun-related work accident. He eventually regained most of his faculties, though he still required a wheelchair. It was noted that reconstructive surgery was difficult due to the gunshot shattering his skull, and he is living with a large indentation on that side of his head.
See also 
- Chen, R.; Cohen, L.G.; Hallett, M. (2002). "Nervous system reorganization following injury". Neuroscience 111 (4): 761–73. doi:10.1016/S0306-4522(02)00025-8. PMID 12031403.
- Vining, Eileen P. G.; Freeman, John M.; Pillas, Diana J.; Uematsu, Sumio; Carson, Benjamin S.; Brandt, Jason; Boatman, Dana; Pulsifer, Margaret B. et al. (1997). "Why Would You Remove Half a Brain? The Outcome of 58 Children After Hemispherectomy—The Johns Hopkins Experience: 1968 to 1996". Pediatrics 100 (2): 163–71. doi:10.1542/peds.100.2.163. PMID 9240794.
- Pulsifer, Margaret B.; Brandt, Jason; Salorio, Cynthia F.; Vining, Eileen P. G.; Carson, Benjamin S.; Freeman, John M. (2004). "The Cognitive Outcome of Hemispherectomy in 71 Children". Epilepsia 45 (3): 243–54. doi:10.1111/j.0013-9580.2004.15303.x. PMID 15009226.
- Bayard, Sophie; Lassonde, Maryse (2001). "Cognitive Sensory and Motor Adjustment to Hemispherectomy". In Jambaqué, Isabelle; Lassonde, Maryse; Dulac, Olivier. Neuropsychology of Childhood Epilepsy. Advances in Behavioral Biology 50 (3). pp. 229–44. ISBN 10.1007/0-306-47612-6_25 Check
- McClelland, Shearwood; Maxwell, Robert E. (2007). "Hemispherectomy for intractable epilepsy in adults: The first reported series". Annals of Neurology 61 (4): 372–6. doi:10.1002/ana.21084. PMID 17323346.
- Johns Hopkins Children's Center research findings
- Hopkins Medical News article on the topic
- The Hemispherectomy Foundation
- The Deepest Cut by Christine Kenneally, The New Yorker
Further reading 
- Battro, Antonio M. (2001). Half a Brain is Enough: The Story of Nico. Cambridge University Press. ISBN 0-521-78307-0.
- Kenneally, Christine (July 3, 2006). "The Deepest Cut". The New Yorker: 36–42.
- Choi, Charles Q. (March 2008). "Do You Need Only Half Your Brain?". Scientific American 298 (3): 104. doi:10.1038/scientificamerican0308-104.