A methohexitone suppression test is used in children with Landau-Kleffner syndrome, which is a rare form of epilepsy. The test is used to find out in which area of the brain seizures (fits) originate, and to help doctors decide whether brain surgery could help your child.
Seizures (fits) of epilepsy
occur when the brain’s normal electrical activity becomes disordered. This test suppresses (damps down) all the brain’s electrical activity and doctors then assess in which area of the brain the abnormal activity returns first. This area may be the area that is primarily responsible for your child’s epilepsy.
Why does my child need this test?
This test may confirm the area of your child’s brain from which his or her epilepsy originates. Previous tests may have already given doctors some idea about which area of your child’s brain needs closer observation, and the methohexitone suppression test will help to clarify this.
Are there any alternatives to this test?
The doctors can tell a lot from the EEG
(electroencephalogram; a test of your child’s brain wave activity) and brain scans, but a methohexitone suppression test can provide important additional information.
What happens before the test?
You will need to come into hospital the day before the test so that your child can have an EEG. Before you come into hospital, please make sure your child’s hair is clean and free from mousse, gel and hairspray. The doctors may also need to stop your child’s medication so that he or she has seizure activity during the test. Your child needs to have seizure activity during the test for it to be successful. Not all children will have an obvious seizure but they may have an abnormal EEG.
If your child is taking a drug called clobazam, this will need to be reduced over a number of weeks before he or she comes into hospital.
The doctors will explain about the test in more detail, discuss any worries you may have and ask you to sign a consent form, giving permission for your child to have the test. Another doctor will also visit you to explain about the anaesthetic.
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. If your child is taking any medicines, please bring these with you and show them to the doctor.
What does the test involve?
Your child will be given a general anaesthetic so that they are deeply asleep for the test. They will then be given an EEG to measure the electrical activity in their brain before the test. Once this recording is finished, the doctors will check the results for any seizure activity. They will use this as a baseline with which to compare the results of the methohexitone suppression test.
When the first EEG test has been done, your child will be given an injection of methohexitone into a vein in their hand, through a cannula (small plastic tube). When the doctors can no longer see any electrical activity on the EEG monitor, they stop the injection. The EEG is then watched as the medication wears off. When the test is complete, the team will wake your child up and remove the electrodes. The test takes approximately an hour.
What happens after the test?
Once your child has woken up and is back on the ward, the doctors will start his or her medication again if it has been stopped. Your child should be able to go home the following afternoon. An outpatient appointment will be arranged for you to bring your child back to the hospital, where you will be told the results of the test. At this stage, the possibility of surgery to help your child’s epilepsy may be discussed with you.
What are the risks of this procedure?
Healthy children usually cope well with the anaesthetic, but the risk increases if your child has other health problems. However, the specialist doctors (anaesthetists) who look after your child during the operation will keep any risks to a minimum. Your child may feel sleepy, dizzy or sick afterwards but this usually doesn’t last long.
It is sometimes necessary to reduce or stop your child’s anticonvulsant drugs temporarily so that electrical activity increases during the test and can be picked up on the EEG. The doctors will decide this when you and your child come into hospital for the test, and may also discuss this with you beforehand. If your child is taking a drug called clobazam, this may need to be reduced over a number of weeks before he or she comes into hospital.
Last reviewed by Great Ormond Street Hospital: June 2009
Ref: 2009F0570 © 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.