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Hemispherectomy Fact Sheet courtesy of the
Johns Hopkins Children's Center
Winter, 2000
What is a hemispherectomy?
A hemispherectomy is an operation in which half of the brain is removed. The deep structures of the brain (the thalamus, brain stem and basal ganglia) are left intact.
When is a hemispherectomy indicated?
A hemispherectomy is a radical operation. It is only considered in patients with severe seizure disorders coming from one side of the brain. Even then, the procedure is considered only when drugs cannot control the seizures, and the patient is increasingly handicapped. While Hopkins physicians perform a hemispherectomy for Rasmussen's syndrome, they also operate on children with developmental abnormalities on one side of the brain, and children who have had severe disabling strokes.
What is Rasmussen's syndrome?
Rasmussen's syndrome, named after Dr. Theodore Rasmussen of the Montreal Neurologic Institute, is a condition of childhood in which seizures often start in one part of the brain and spread into neighboring areas. The seizures become progressively more severe and difficult to control. A child loses mobility on the side opposite the affected side of the brain. Pathologically, Rasmussen's syndrome looks as if a virus is present. However, despite vigorous attempts by researchers, no virus has been isolated. Many believe it is caused by an immunologic reaction. In the natural couse of Rasmussens's syndrome, seizures continue for many years. Most patients become increasingly disabled.
At what age can a hemispherectomy be performed?
A hemispherectomy can be performed at any age. However, it appears that younger children do better because the remaining side of the brain takes over functions from the lost side. Although it's not clear as to what age transference for speech to the remaining hemisphere occurs, it may take place up to age 14, and sometimes later. For many children, the damage in the speech area causes language to be transferred to the opposite side even before the operation.
What are the risks of surgery?
Surgery may take as long as 12 hours. There are always risks of infections and bleeding into the empty space, and there is even a small risk of death. On two occasions there were apparent shifts of the brain, causing coma which lasted for weeks before the children completely recovered. There are also risks of hydrocephalus which may require a shunt.
Do hemispherectomy patients suffer any long-term disability?
Patients with hemispherectomies always have some paralysis on the side of the body opposite the removed hemisphere. They are usually able to walk with only a limp, and perhaps an ankle brace. They are able to move the elbow and shoulder on the paralyzed side, but do not have normal function in the hand and fingers, or normal sensation. Therefore, the paralyzed hand becomes a “helper” hand and never completely recovers. However, all the children have some paralysis before the operation. Surgery does not appear to decrease a child's intellect. Intelligence sometimes, in fact, improves due, partly, to a lack of seizures and elimination of anti-seizure medications. Where there are no complications, many of these children leave the hospital for rehabilitation within two weeks of surgery.
The future
Writing about their experience, in the August 1997 issue of Pediatrics, “Why Would You Remove Half a Brain? The Outcome of 58 Children After Hemispherectomy - The Johns Hopkins Experience: 1968 to 1996,” Johns Hopkins Children's Center neurologists John M. Freeman, M.D., and Eileen P.G. Vining, M.D., look toward the future. “Awed” by the apparent retention of memory after removal of half of the brain, either half, and by the retention of the child's personality and sense of humor, they look foward to the time when there are less radical approaches to these problems, for which hemispherectomies are at present the surgery of last resort. Today, Drs. Freeman and Vining and their colleagues are investigating promising new treatments for Rasmussen's syndrome, which might one day make hemispherectomies obsolete.