Hemispherectomy is a surgical treatment for epilepsy in which one of the two cerebral hemispheres, which together make up the majority of the brain, is removed.


Hemispherectomy is used to treat epilepsy when it cannot be sufficiently controlled by medications.

The cerebral cortex is the wrinkled outer portion of the brain. It is divided into left and right hemispheres, which communicate with each other through a bundle of nerve fibers called the corpus callosum, located at the base of the hemispheres.

The seizures of epilepsy are due to unregulated electrical activity in the brain. This activity often begins in a discrete brain region called the focus of the seizure, and then spreads to other regions. Removing or disconnecting the focus from the rest of the brain can reduce seizure frequency and intensity.

In some people with epilepsy, there is no single focus. If there are multiple focal points within one hemisphere, or if the focus is undefined but restricted to one hemisphere, hemispherectomy may be indicated for treatment.

Removing an entire hemisphere of the brain is an effective treatment. The hemisphere that is removed is usually quite damaged by the effects of multiple seizures, and the other side of the brain has already assumed many of the functions of the damaged side. In addition, the brain has many "redundant systems," which allow healthy regions to make up for the loss of the damaged side.

Children who are candidates for hemispherectomy usually have significant impairments due to their epilepsy, including partial or complete paralysis and partial or complete loss of sensation on the side of the body opposite to the affected brain region.


Epilepsy affects up to 1% of all people. Approximately 40% of patients are inadequately treated by medications, and so may be surgery candidates. Hemispherectomy is a relatively rare type of epilepsy surgery. The number performed per year in the United States is likely less than 100. Hemispherectomy is most often considered in children, whose brains are better able to adapt to the loss of brain matter than adults.


Hemispherectomy may be "anatomic" or "functional." In an anatomic hemispherectomy, a hemisphere is removed, while in a functional hemispherectomy, some tissue is left in place, but its connections to other brain centers are cut so that it no longer functions.

Several variations of the anatomic hemispherectomy exist, which are designed to minimize complications. Lower portions of the brain may be left relatively intact, or muscle tissue may be transplanted in order to protect the brain's ventricles (fluid-filled cavities) and prevent leakage of cerebrospinal fluid from them.

Most surgical centers perform functional hemispherectomy. In this procedure, the temporal lobe (that region closest to the temple) and the part of the central portion of the cortex are removed. Additionally, numerous connecting fibers within the remaining brain are severed, as is the corpus callosum, which connects the two hemispheres.

During either procedure, the patient is under general anesthesia, lying on the back. The head is shaved and a portion of the skull is removed for access to the brain. After all tissue has been cut and removed and all bleeding is stopped, the underlying tissues are sutured and the skull and scalp are replaced and sutured.


The candidate for hemispherectomy has epilepsy untreatable by medications, with seizure focal points that are numerous or ill defined, but localized to one hemisphere. Such patients may have one of a wide variety of disorders that have caused seizures, including:

The candidate for any type of epilepsy surgery will have had a wide range of tests prior to surgery. These include electroencephalography (EEG), in which electrodes are placed on the scalp, on the brain surface, or within the brain to record electrical activity. EEG is used to attempt to locate the focal point(s) of the seizure activity.

Several neuroimaging procedures are used to obtain images of the brain. These may reveal structural abnormalities that the neurosurgeon must be aware of. These procedures will include magnetic resonance imaging (MRI), x rays, computed tomography (CT) scans, or positron emission tomography (PET) imaging.

Neuropsychological tests may be done to provide a baseline against which the results of the surgery are measured. A Wada test may also be performed, in which a drug is injected into the artery leading to one half of the brain, putting it to sleep. This allows the neurologist to determine where in the brain language and other functions are localized, and may also be useful for predicting the result of the surgery.


Immediately after the operation, the patient may be on a mechanical ventilator for up to 24 hours. Patients remain in the hospital for at least one week. Physical and occupational therapy are part of the rehabilitation program to improve strength and motor function.


Hemorrhage during or after surgery is a risk for hemispherectomy. Disseminated intravascular coagulation, or blood clotting within the circulatory system, is a risk that may be managed with anticoagulant drugs. "Aseptic meningitis," an inflammation of the brain's covering without infection, may occur. Hydrocephalus, or increased fluid pressure within the remaining brain, may occur in 20–30% of patients. Death from surgery is a risk that has decreased as surgical techniques have improved, but it still occurs in approximately 2% of patients.

The patient will lose any remaining sensation or muscle control in the extremities on the side opposite the removed hemisphere. However, upper arm and thigh movements may be retained, allowing adapted function with these parts of the body.

Normal results

Seizures are eliminated in 70–85% of patients, and reduced by 80% in another 10–20% of patients. Patients with Rasmussen disease, which is progressive, will not benefit as much. Medications may be reduced, and some improvement in intellectual function may occur.

Morbidity and mortality rates

Death may occur in 1–2% of patients undergoing hemispherectomy. Serious but treatable complications may occur in 10–20% of patients.


Corpus callosotomy may be an alternative for some patients, although its ability to eliminate seizures completely is much less. Multiple subpial transection, in which several bundles of nerve fibers are cut, is also an alternative for some patients.

See also Corpus callosotomy ; Vagal nerve stimulation .



Devinsky, O. A Guide to Understanding and Living with Epilepsy. Philadelphia: EA Davis, 1994.


Epilepsy Foundation. http://www.epilepsyfoundation.org .

Richard Robinson


Hemispherectomy is performed by a neurosurgical team in a hospital. It is also performed by a relatively small number of specialized centers.


Also read article about Hemispherectomy from Wikipedia

User Contributions:

Is it possible to receive this treatment (although I am not ill, somatically)? If so, where?
What are the top hoptitals in the US for pediatric neurological surgery for epilepsy?
ahmed mostafa

usually the cerebrospinal fluid fills the space
dear sir or madam,

thank you very much for reading my email , and thank every one who work with you , my name Zakaria and my son danial is tow and a half years old and he is ill he complain about disease name sturge weber and eye pressure anda take him to all good Dr. and hospital here in turkey but they can not help my son danial he is still complain about the disease and his health is too bad and some of the Dr. here in turkey told me I have to take my son to good Dr. and good hospital
with my best
Abigael Baker
how long, on average, does it take for the remaining hemisphere to take on the responsibilities of the removed one?
Sara McKechnie
Does the patient loose all function of the opposite side of the body and or language. How long typically does is take to recover with rehab?
hi pls help is there anyone in the uk that you no of or could recommed my child has othahara syndrome would this surgery help my child we are thinking of coming to the usa to get this treatment wot would be the cost of the operation would it be success in wot percentage

please respond many thanks darren

email fluffyduckents@hotmail.co.uk

tel uk 07902 453 675 im not sure of the code to call from the usa to a uk mobile
i have a question that i can't understand and please maybe i'm ignorant but theres not exists dumb questions, why the people that rceive this treatmente survive? if the skull is half empty the brain doesn't have more space for move or receive a impact that hurt them?
i know the body is incredible but i don't understad how some people receive moderate hit in the head and die and with this procedure that is very complex all result in some way allright. i know that is made in an controlate ambient and very carefull and is not like receive a bullet in the head.

but for me is very amazing the capabilities of the body and the brain for reconstruct herself.

please if any one can iluminate me i'm very gratfull
I am writing a paper for school and the only thing this article doesn't tell me that I need to know is what are some of the behavioral changes that occured after the surgery?
What is the age of the oldest person who has had a hemispherectomy to your knowledge, and what was the outcome? I'm interested in brain plasticity at different ages.
If a person say a baby has this operation what is it's life sap after the operation
I have a father who is presently 59 n is living with epilepsy and as he is getting older, da seizures come more often even wen he is on medication and sometimes it becomes so bad he doesn't recognise us(me and my siblings, nor my mother). Is there anything that can be done? Can he still be considered for Hemispherectomy? If yes, what exactly will be needed before the surgury?
My 5 year old has cerebral palsy and has had seizures in the past that were really bad. He has lost over half of his brain due to encephalitis and the seizures. He cannot due anything such as walk, talk, intentionally do anything on his own for that matter. Could he possibly be a candidate and get this procedure done?
Dina Clark
I am asking if a person would survive the complete removal of the upper cortex? If they did how could they continue to function? Would age of the person make a difference?

The help given to epilepsy sufferers by the medical proceedures described are amazing, but it just sounds so radical. I didn't know it was possible to reduce seizures in this way because of quality of life issues. Hence the question asked...Theoretical I hope!
I have a 7 year old that had a hemispherectomy when he was 1 1/2,he has paralysis on his left side,would he be able to get an adjustment to help with the paralysis?
My daughter is 12 ½.
She has been diagnosed with RE in April 2010 when she was 8 ½ , on basis of MRI (a year after her first MRI in 2009).
The problem is with her left hemisphere.
She’s had numerous intra-vein treatments with steroids and immunoglobuline.
The worst changes in the brain were between 2010-2011.
In April 2012 there were no changes in the MRI compared to the MRI of 2011, and in the MRI of 2013 also, but her health is worsening, especially since August 2012, when she lost the ability to write and eat with the right hand.
She’s taking three anti-epilepsy medicaments (Depakine Chronosphere, Keppra, Frisium).
Attacks aren’t frequent (once/twice a month), but she’s got a continuous trembling of the right hand, right side of the face and since three weeks ago – trembling in her voice. She speaks slowly, but grammatically. She has problems with motivation for rehabilitation and schoolwork, but is good at playing cards and games. Since her voice started trembling, she has difficulty in motivating herself to meet with friends. All she wants to do is to watch films and play computer games.
Doctors say it’s time to seriously consider the operation.
I’ve read the questions above and I would like to ask for an answer to some of them, and also add some of mine.

The imagining of the brain is improving dramatically. Perhaps full hemispherectomy is not the only answer for RE?

There are very good neurosurgeons in Poland, but there could be places were possibilities of imagining of the damaged part of the brain are much more advanced, enabling a more precise operation. Could you help me find those places – preferably in Europe/ in the USA?

And the questions which were already asked above:

How long, on average, does it take for the remaining hemisphere to take on the responsibilities of the removed one?

Does the patient loose all function of the opposite side of the body and or language? How long typically does is take to recover with rehab?

I need to know what are some of the behavioral/characterological changes that occurred after the surgery?

What is the age of the oldest person who has had a hemispherectomy to your knowledge, and what was the outcome? I'm interested in brain plasticity at different ages.
Mary Jo Hutson
In the case of Rasmussen's Encephalitis, Anatomical Hemispherectomy is very effective and has completely stopped my Grand Mal Status Epilepticus.

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