What is a hemispherectomy?
A hemispherectomy is an operation that removes or disconnects the cortex (or outer layer) of one half of the brain (or hemisphere) from the other.
The type of hemispherectomy most frequently performed at Great Ormond Street Hospital (GOSH) is a modification of a ‘functional hemispherectomy’. This involves disconnecting the affected side of the brain but not removing all of it.
You should read this information in conjunction with our surgery for epilepsy information, which explains about the epilepsy surgery programme at Great Ormond Street Hospital.
Why might my child need this operation?
Some children with a ‘hemi’ syndrome may suffer from seizures that cannot be controlled by drugs. A small proportion of these children may benefit from having a hemispherectomy. These children may have seizures that originate from one side of the brain.
How do the doctors decide if my child needs this operation?
Your child will previously have had a series of tests and investigations. The Epilepsy team will be able to see where in the brain the seizures are starting and whether these parts of the brain are needed for important functions.
When most children with a hemi syndrome have these tests, the results show that the abnormal side of the brain does nothing else but cause seizures. This means that the operation is unlikely to worsen any physical or learning problems.
When the Epilepsy team has seen all these results, they will decide if surgery is an option. You will then be able to discuss these results with the team at an outpatient appointment at the Epilepsy Surgery Clinic and come to a decision about the operation.
What are the risks of the operation?
Healthy children usually cope well with the anaesthetic, but the risk increases if your child has other problems. Any surgery carries a small risk of infection or bleeding. Fine finger and toe movements, if they were present on the weakened side of the body, may not return after the operation. Your child’s arm and leg on the affected side may get worse, but this is likely to improve.
Your child may develop raised pressure inside his or her head after the operation. A small number of children may need a shunt (pressure valve) inserted to reduce this pressure.
There is a five to ten per cent chance of complications, which could mean your child could have to stay in hospital longer than expected.
What should I expect from this operation?
The doctors will explain the risks and benefits of the operation and the chance of improvement in seizure control to you in more detail before you make a decision.
Generally, when the side of the brain causing seizures is abnormal and the other side is normal, the chance of the operation leading to your child being free from seizures is between 60 and 80 per cent depending on the abnormality in the brain.
As this information is written in general terms, the doctor will confirm the likelihood of success for your own child.
Are there any alternatives to this operation?
The doctors could continue trying to control your child’s seizures with combinations of drugs. However, although there are new drugs available all the time, people who have not responded to them early, have a smaller chance of responding with each new drug tried.
This means that there is only a small chance of drugs controlling your child’s seizures long term.
What happens before the operation?
You will need to come to the ward the day before the operation. This is to make sure that your child is well enough to have the operation.
A doctor will examine your child and take a blood sample to check that his or her blood levels are fine. The doctors will explain about the surgery in more detail, discuss any worries you may have and ask your permission for the operation, by asking you to sign a consent form. Another doctor will also visit you to explain about the anaesthetic. Occasionally, some children need neuropsychology testing before the operation, but we will let you know if this is likely before you come into hospital.
If your child has any medical problems, for instance, allergies, please tell the doctors about these. If your child has had any infectious diseases like chicken pox or head lice recently, please tell the doctors.
The evening or the morning before the operation, your child will need to have a bath and a hair wash with a special soap.
What does the operation involve?
Your child will have this operation under a general anaesthetic. This means that your child will not feel any pain during the operation, which will last between four and five hours.
Your child’s head will not be shaved completely, just a line where the doctors will make the incisions (cuts). This will be done while your child is under the anaesthetic. The doctors will have to open a piece of your child’s skull so that they can operate on the brain, but they will replace and fix it after surgery. After the operation, they will close up your child’s skin and fix it with stitches.
What happens after the operation?
A member of staff will bring your child back to the ward after the operation, when he or she has recovered from the anaesthetic. When your child comes back from the operating theatre there will be no head bandage so you will be able to see where the doctor made the incision. The nurses on the ward will put a head bandage on your child when he or she returns to the ward. Your child may also have a drain coming out from the wound, which looks like a clear, plastic tube. This is removed after 24 hours.
At the end of the day, the doctors will visit you to talk about the operation.
Your child may feel sick after the operation, but the doctors will give him or her medicines to reduce this. The sickness should pass within a couple of days. Children usually come back from theatre with an intravenous infusion (drip) to replace their body fluids when they are unable to drink. The nurses will monitor your child closely for the first few days after the operation to make sure he or she is recovering well.
Your child’s face may be bruised and swollen after the operation, but this is unlikely to show for a few days. This bruising and swelling will gradually reduce. If your child is in any pain, the doctors and nurses will give him or her medicines to reduce this. Your child may also develop a high temperature after the operation. This is expected and not usually due to an infection, but the doctors may carry out some tests to make sure.
Your child is likely to be in hospital for between four and seven days. He or she will be able to gradually return to normal day-to-day life and full activity over the next two to three months. Your child should stay away from school for about six weeks after the operation. Your doctor will give you more specific information before you leave hospital.
When you and your child leave hospital, we will arrange for you to come to outpatient appointments at regular intervals. These will usually be six weeks, six months and a year after the operation. We will check that your child is recovering from the operation well and that his or her seizures are under control.
Twelve months after the operation, your child may need to have a short stay in hospital so we can carry out more tests. It is unlikely that your child’s drugs would be changed for at least six months.
Last reviewed by Great Ormond Street Hospital: June 2009
Ref: 2009F0121 © GOSH Trust June 2009
Compiled by the Epilepsy Surgery Team in collaboration with the Child and Family Information Group
This information does not constitute health or medical advice and will not necessarily reflect treatment at other hospitals. If you have any questions, please ask your doctor. No liability can be taken as a result of using this information.