Hemispherotomy

This page explains about an operation called a hemispherotomy and explains what to expect when your child comes in to Great Ormond Street Hospital (GOSH) for the operation. 

A hemispherotomy is an operation that disconnects the cortex (or outer layer) of one half of the brain
(or hemisphere) from the other without removing it.

Some children have a significant abnormality affecting all or most of one hemisphere of their brain. There are a number of different reasons for this. If all the seizures appear to be coming from the abnormal side of the brain and they cannot be controlled by drugs, these children may benefit from having a hemispherotomy.

Your child will previously have had a series of tests and investigations to see where in the brain the seizures are starting and whether these parts of the brain are needed for important functions. All these results are discussed at the multi-disciplinary team epilepsy surgery meeting.

The team 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. We will send you a letter following your epilepsy surgery clinic appointment summarising the benefits and risks of surgery for your child.

Healthy children usually cope well with the anaesthetic, but the risk increases if your child has other problems. All surgery carries a small risk of infection or bleeding. Your child possibly already has weakness on one side of the body. This may get worse after surgery, but is then likely to improve with time (fine finger and toe movements, if they were present on the weakened side of the body, may not return after the operation). If your child does not already have a weakness, the risk of post-operative weakness will be discussed with you in detail.

Your child may develop raised pressure inside his or her head after the operation. A small number of children (up to one in 10) may need a shunt (pressure valve) inserted to reduce this pressure. If the doctors feel that a shunt is needed then the risks and benefits of this procedure will be discussed with you.

Your child’s brain abnormality may mean that they are not able to see to one side. If they have normal vision before surgery then the surgery will reduce their visual field looking to one side and they may not see objects coming from this side. This will not improve after surgery but most children learn to adapt to this very well.

Overall, 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.

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.

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.

If the ketogenic diet is suitable for your child, your doctor will have discussed this with you. Vagus Nerve Stimulation (VNS) therapy or corpus callosotomy may also be an option. This may be discussed with you by your consultant or by the team at your epilepsy surgery clinic appointment. Further information about these options is available.

Before admission, we will ask you to arrange with your family doctor (GP) for your child to have a blood test to ensure they are well for surgery.

You will need to come to Koala 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 repeat 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.

Before the operation, your child will need to have a bath and a hair wash with a special soap.

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 incision (cut). This will be done while your child is under the anaesthetic. The doctors will have to remove 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.

A member of staff will bring your child back to Koala Ward after the operation, when he or she has recovered from the anaesthetic.

When your child comes back from the operating theatre they will have a head bandage in place. 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 a little bruised and swollen after the operation. This may get worse over the first two to three days but will then start to improve.

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 four weeks after the operation. Your nurse will give you more specific information before you leave hospital.

Some children need a period of neuro-rehabilitation after hemispherotomy. If your child needs this, it will be discussed with you and plans made in advance of surgery.

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 will have a few visits to hospital so we can carry out follow-up tests. It is unlikely that your child’s drugs would be changed for about six months.