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Hemispherectomy is a very rare neurosurgical procedure in which a cerebral hemisphere (half of the upper brain, or cerebrum) is removed, disconnected, 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, notably Rasmussen's encephalitis. About one in three patients with epilepsy will continue to have persistent seizures despite epileptic drug therapy.[1] Hemispherectomy is reserved for the most extreme cases of this one-third in which the individual’s seizures are irresponsive to medications or other less invasive surgeries and significantly impair functioning or put the patient at risk of further complications. The procedure successfully cures seizures in about 85–90% of patients. Additionally, it is also known to often markedly improve the cognitive functioning and development of the individual.[2] Subtotal hemispherectomy sparing sensorimotor cortex can be performed with successful seizure control expected in 70–80% of patients. Even with the presence of widespread unilateral epileptogenicity or anatomic/functional imaging abnormalities, complete hemispherectomy can often be avoided, particularly when there is little hemiparesis.[3]

History and development[edit]

Hemispherectomy was first performed on a dog in 1888 by Friedrich Goltz. The first such operation on humans was done by Walter Dandy in 1928[4] for glioblastoma multiforme. Hemispherectomy was revitalized in children in the 1980s by John M. Freeman and Ben Carson[5] at Johns Hopkins Hospital.[6]

In the 1960s and early 1970s, hemispherectomy involved essentially removing an entire half of the brain. This procedure is known as anatomical hemispherectomy. Anatomical hemispherectomy decreases the likelihood that seizures will return, as there is no longer any part of the identified epileptic brain area left to cause seizures. A second type of hemispherectomy, known as functional hemispherectomy, has become more prevalent in recent years. In this procedure, only the epileptic portions of that side of the brain are removed, as opposed to the entire hemisphere. If a functional hemispherectomy is chosen over an anatomical hemispherectomy, it is likely because it allows for less blood loss and greater chance of resilience for the patient.[7][8] Additionally, functional hemispherectomy is less likely to cause hydrocephalus, the “excessive accumulation of [cerebrospinal fluid] in the brain,” which leads to complications from harmful pressure on brain tissues.[9]

Within the last fifteen years, a few types of functional hemispherectomies have emerged typically involving removal of less brain tissue. One such procedure is known as peri-insular hemispherotomy. Peri-insular hemispherotomy has been developed to allow for seizure relief with minimal brain tissue removal. In this procedure, the surgeon aims to disconnect (rather than remove) the hemisphere, hence termed hemispherotomy, in order to minimize long term complications.[10] This procedure continues to be refined and is now performed more commonly than classical hemispherectomy.[11][12] Another procedure relatively new to epilepsy surgery is endoscopic surgery (see endoscopy), surgery performed using small camera scopes and little incision sites. Its appeal lies in its minimally invasive nature, which generally decreases chance of infection and increases speed of physical recovery.[13][14]

Patient criteria[edit]

Because of the dramatic alteration of brain composition and the inherent risk that hemispherectomies pose, there are criteria that must be met in order for a person to qualify for the procedure. Criteria include no successful control of seizures throughout a variety of drug trials, and a reasonable to high chance of procedural success.[15]

One such predictor of success is often the age of the patient. 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.[16] In one study of children under 5 who had this surgery to treat catastrophic epilepsy, 73.7% were freed of all seizures.[17]

The success of the procedure is not, however, limited to children. A study in 2007 indicated the long-term efficacy of anatomic hemispherectomy in carefully selected adults, with seizure control sustainable over multiple decades.[18] A case study published in 2015 of 2 adults aged 48 and 38 demonstrated the success of functional hemispherectomy in treating status epilepticus (SE), an epileptic condition in which seizures are prolonged or occur closely together.[19] In 2012, a case study following 30 individuals having undergone some form of hemispherectomy in adulthood found that 81% of individuals were seizure free post-procedure. Furthermore, almost all participating patients reported improved quality of life. The conclusion: “adult patients do not have to expect more problems with new deficits, appear to cope quite well, and most profit from surgery in several quality of life domains.”[20]

Ultimately, the chances of benefit and improvement to the individual must outweigh the costs. For example, a neurosurgeon would not recommend hemispherectomy in a patient who still possessed significant functionality, despite frequent seizures. Such a patient would risk losing their remaining functionality. Likewise, hemispherectomy likely would be recommended to a patient with debilitating seizures. A patient with little or severely deteriorating functioning does not have as much to risk by having the procedure, thus the chance of benefit to them is greater.[21] Depending on the case, a recommendation for a hemispherectomy could be more risky for a child than for an adult. Thus, age is not always the deciding success factor for hemispherectomies.[citation needed]


Overall, hemispherectomy is a successful procedure. A 1996 study of 52 individuals who underwent the surgery found that 96% of patients experienced reduced or completely ceased occurrence of seizures post-surgery.[22] Studies have found no significant long-term effects on memory, personality, or humor,[23] and minimal changes in cognitive function overall.[24] For example, one case followed a patient who had completed college, attended graduate school and scored above average on intelligence tests after undergoing this procedure at age 5. This patient eventually developed "superior language and intellectual abilities" despite the removal of the left hemisphere, which contains the classical language zones.[25]

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.[26] One study following the cognitive development of two adolescent boys who had undergone hemispherectomy found that “brain plasticity and development arise, in part, from the brain’s adaption of behavioral needs to fit available strengths and biases…The boy adapts the task to fit his brain more than he adapts his brain to fit the task.”[27] Neuroplasticity after hemispherectomy does not imply complete regain of previous functioning, but rather the ability to adapt to the current abilities of the brain in such a way that the individual may still function, however differently the new way of functioning is.[citation needed]

Christina Santhouse (now Paravecchia) underwent a Hemispherectomy on February 13, 1996, performed by Ben Carson when she was eight years old. Previously, she had suffered from Rasmussen's encephalitis, which caused her to experience around 150 seizures a day. After the surgery, her family was told that she would never be able to do many normal activities, such as driving a car or holding a normal job. However, she far surpassed everyone's expectations by going on to earn a master's degree in speech pathology and by getting married and having children of her own.[28][29]

Traumatic hemispherectomy[edit]

There are cases where a person that received major trauma to one side of the brain, such as a gunshot wound, and 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 lived with a large indentation on that side of his head.[citation needed]

See also[edit]


  1. ^ Kraemer, Diana L., MD, and David Vossler Gregg, MD. "Epilepsy Surgery." emedicine.medscape.com/. Ed. Brian H. Kopell. Medscape, 11 Apr. 2014. Web. 21 Sept. 2016.
  2. ^ Blume, H. "Hemispherectomy." Epilepsy Foundation. N.p., Jan. 2004. Web. 21 Sept. 2016.
  3. ^ Chugani, HT; Asano, E; Juhász, C; Kumar, A; Kupsky, WJ; Sood, S (2014). ""Subtotal" hemispherectomy in children with intractable focal epilepsy" (PDF). Epilepsia. 55 (12): 1926–33. doi:10.1111/epi.12845. hdl:2027.42/109835. PMID 25366422.
  4. ^ Neurological Institute, Cleveland Clinic (February 8, 2017). "Hemispherectomy". CHASA.ORG. Retrieved February 8, 2017.
  5. ^ "Johns Hopkins Medicine Community Mourns the Death of Internationally Renowned Pediatric Neurologist John M. Freeman – 01/06/2014".
  6. ^ Collins, Jessica; Mullins, Wendy (December 9, 2002). "Hemispherectomy End Seizures In Many Older Children With Rare Seizure Disorder". hopkinsmedicine.org. John M. Freeman contributed to study. Archived from the original on April 2, 2014. Retrieved April 1, 2014.
  7. ^ Choi, Charles. "Strange but True: When Half a Brain Is Better than a Whole One." Scientific American. N.p., 24 May 2007. Web. 21 Sept. 2016.
  8. ^ Danielpour M, von Koch C, S, Ojemann S, G, Peacock W, J, Disconnective Hemispherectomy. Pediatr Neurosurg 2001;35:169–172
  9. ^ National Institute of Health. "Hydrocephalus Fact Sheet." National Institute of Neurological Disorders and Stroke. U.S. National Library of Medicine, May 2013. Web. 21 Sept. 2016.
  10. ^ Villemure, Jean-Guy, MD, and Christopher Mascott R., MD. "Peri‐insular Hemispherotomy: Surgical Principles and Anatomy." Neurosurgery 37.5 (1995): 975–81. Neurosurgery: The Register of the Neurosurgical Meme. Congress of Neurological Surgeons. Web. 21 Sept. 2016.
  11. ^ De Ribaupierre, Sandrine; Delalande, Olivier (September 2008). "Hemispherotomy and other disconnective techniques". Neurosurgical Focus. 25 (3): E14. doi:10.3171/FOC/2008/25/9/E14. PMID 18759615. S2CID 20348774.
  12. ^ Young, Christopher C.; Williams, John R.; Feroze, Abdullah H.; McGrath, Margaret; Ravanpay, Ali C.; Ellenbogen, Richard G.; Ojemann, Jeffrey G.; Hauptman, Jason S. (2020-04-01). "Pediatric functional hemispherectomy: operative techniques and complication avoidance". Neurosurgical Focus. 48 (4): E9. doi:10.3171/2020.1.FOCUS19889. ISSN 1092-0684. PMID 32234987.
  13. ^ Chandra SP, Tripathi M. Endoscopic epilepsy surgery: Emergence of a new procedure. Neurol India 2015;63:571‑82.
  14. ^ Sood, S; Marupudi, NI; Asano, E; Haridas, A; Ham, SD (2015). "Endoscopic corpus callosotomy and hemispherotomy". J Neurosurg Pediatr. 16 (6): 681–6. doi:10.3171/2015.5.PEDS1531. PMID 26407094.
  15. ^ Kraemer, Diana L., MD, and David Vossler Gregg, MD. "Epilepsy Surgery." emedicine.medscape.com/. Ed. Brian H. Kopell. Medscape, 11 Apr. 2014. Web. 21 Sept. 2016.
  16. ^ Chen, R.; Cohen, L.G.; Hallett, M. (2002). "Nervous system reorganization following injury". Neuroscience. 111 (4): 761–73. CiteSeerX doi:10.1016/S0306-4522(02)00025-8. PMID 12031403. S2CID 16507957.
  17. ^ Lettori, D.; Battaglia, A.; Sacco, A.; Veredice, C.; Chieffo, D.; Massimi, L.; Tartaglione, T.; Chiricozzi, F.; Staccioli, S.; Mittica, A.; Di Rocco, C.; Guzzetta, F. (2008). "Early hemispherectomy in catastrophic epilepsy". Seizure. 17 (1): 49–63. doi:10.1016/j.seizure.2007.06.006. PMID 17689988.
  18. ^ 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. S2CID 434053.
  19. ^ McGinity, Michael, Nicholas Andrade, Kameel Karkar, Jean-Louis Caron, and Charles Szabo. "Functional Hemispherectomy for Refractory Status Epilepticus in 2 Adults." World Neurosurgery 93 (2016): 489.e11-89.e16. Science Direct. Elsevier, Sept. 2016. Web. 21 Sept. 2016.
  20. ^ Schramm, J., Delev, D., Wagner, J. et al. Acta Neurochir (2012) 154: 1603. doi:10.1007/s00701-012-1408-z
  21. ^ Kraemer, Diana L., MD, and David Vossler Gregg, MD. "Epilepsy Surgery." emedicine.medscape.com/. Ed. Brian H. Kopell. Medscape, 11 Apr. 2014. Web. 21 Sept. 2016.
  22. ^ Carson, Benjamin S., MD, Sam Javedan P., John Freeman M., MD, Eileen Vining P.G., MD, Aaron Zuckerberg L., MD, Jeremy Lauer A., MS, and Michael Guarnieri, PhD. "Hemispherectomy: A Hemidecortication Approach And Review of 52 Cases." Journal of Neurosurgery 1996th ser. 84.June (n.d.): 903-11. Print.
  23. ^ Vining, Eileen P. G.; Freeman, John M.; Pillas, Diana J.; Uematsu, Sumio; Carson, Benjamin S.; Brandt, Jason; Boatman, Dana; Pulsifer, Margaret B.; Zuckerberg, Aaron (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. S2CID 6703956.
  24. ^ 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. S2CID 15894321.
  25. ^ Smith, A and Sugar O. Development of above normal language and intelligence 21 years after left hemispherectomy. [1] Neurology, 1975 September; 25(9):813-8.
  26. ^ Bayard, Sophie; Lassonde, Maryse (2001). "Cognitive Sensory and Motor Adjustment to Hemispherectomy". In Jambaqué, Isabelle; Lassonde, Maryse; Dulac, Olivier (eds.). Neuropsychology of Childhood Epilepsy. Advances in Behavioral Biology. 50. pp. 229–44. ISBN 978-0-306-47612-9.
  27. ^ Coch, Donna, Kurt Fischer W., and Geraldine Dawson. "Dynamic Development of the Hemispheric Biases in Three Cases: Cognitive/Hemispheric Cycles, Music, and Hemispherectomy." Human Behavior, Learning, and the Developing Brain. New York: Guilford, 2007. 94–97. Print.
  28. ^ "20 years after surgery, a full life with half a brain".
  29. ^ "For brain surgery patient, greatest challenge is motherhood". Associated Press. 18 May 2019.

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