The eSAM test, also known as a Wada test, is a neuropsychological test that requires your child to answer some questions and do some tasks while half of their brain is “frozen” or put to sleep. They will have an EEG during the test. The test takes about one and a half hours.
To take part, your child will need to be able to lie still and follow instructions for the full test.
Why does my child need an eSAM and EEG?
An eSAM will tell your child’s doctor which side of the brain is responsible for speech or memory. The test is done if your child’s fMRI does not provide clear results.
An EEG measures electrical activity in the brain to help your child’s doctors see more clearly where seizures start.
Together, the eSAM and EEG will help your child’s healthcare team identify which side of the brain is important for your child’s speech and memory. This allows them to better plan your child’s surgery so that those areas of the brain can be left intact.
eSAM testing room
Does the test have any risks or side effects?
There are typically no risks from having an eSAM test. However, the dye for the angiogram may make your child urinate more than usual.
How do I prepare my child for the eSAM test?
- Explain what will happen during the eSAM test in words your child understands.
- Make sure your child’s hair is freshly washed. Check for any signs of head lice and tell the nurse at the hospital if you see anything.
- To help the electrodes stay in place during the test, do not use conditioner or styling products in your child's hair after you wash it.
- Your child may need to have an empty stomach for the test. The doctor or nurse will explain when your child should stop eating and drinking before the test.
A few days or weeks before the test, your child will have a set of neuropsychological tests to let the healthcare team get baseline information about your child’s language, cognitive (thinking) skills and memory. Your child’s healthcare team will schedule these tests with you and explain what is involved.
Will my child need to be sedated before the eSAM test?
Your child will need to be awake to follow the instructions during the test, but if they are very anxious, they can receive a sedative (medicine to help keep them calm).
What happens when my child arrives for the eSAM test?
Before the test, the doctor will explain the procedure to you and your child.
- An EEG technologist will place EEG electrodes on your child’s scalp to monitor the brain activity during the test.
- Your child will be asked to lie down on an X-ray table.
- An interventional radiologist (doctor specializing in scans and x-rays) will inject a local anaesthetic into your child’s groin. Apart from the prick of the needle, your child may feel slight pressure and a mild burning sensation.
- The radiologist will make a small cut and insert a thin catheter (tube) into an artery in the groin so that dye can be injected into the arteries that bring blood to the brain.
What happens during the eSAM test?
The test has two parts:
- an angiogram
- an eSAM test.
1. Angiogram
An angiogram is an x-ray of blood vessels.
Your child’s doctor will inject special dye into your child’s artery to help them monitor blood flow more easily. At first, your child may feel heat or pressure, a metallic taste in their mouth and slight pain. These will all wear off within minutes.
The blood flow in your child’s brain will then be x-rayed over the following 10 minutes. Your child will need to stay still during this time.
2. eSAM test
Following the x-rays, your child will receive an injection of medication called etomidate. This puts one half of the brain to sleep but allows the other side to function normally.
Immediately after the injection, your child will not be able to move one side of their body (the side opposite the location of the injection) and may not be able to speak.
A neuropsychologist will ask your child questions to test their language and memory. Depending on how your child answers, and if they can answer, the healthcare team will see which side of the brain is responsible for language and memory. For instance, if your child is unable to speak while the left side of their brain is asleep, it will be clear that the left side of their brain is crucial for language function.
This information will help the team identify the centres of language and memory in your child’s brain so they can best plan the epilepsy surgery.
Once the etomidate wears off (usually within 10 minutes), the catheter will be moved to the artery that supplies blood to the other side of the brain. Your child will receive a second injection of etomidate and the test will be repeated for the other side of the brain.
What should I expect after the eSAM test?
As soon as both sides of the brain are tested, the interventional radiologist will remove the catheter, apply pressure to stop any bleeding and place a bandage over the injection site. Your child should not normally need any stitches.
Your child may be slightly sore or bruised, but an ice pack can be applied to ease the pain.
Your child will be asked to rest in the hospital for several more hours before going home. If they feel nauseous, cold or numb or have a strange sensation in their groin, tell the nurse right away.
As your child may need to urinate more than usual, give them plenty of fluids over the next few hours.
When will I get the test results?
Your child’s doctor will use the results of the eSAM test alongside other test results to decide on the best treatment or surgery for your child. When your doctor receives the results, they will discuss them with you and your child at a follow-up appointment.
Your child will be sedated for the eSAM to allow testing of each half of their brain. You will receive instructions from the neurology team on when your child should stop eating and drinking before the eSAM appointment.
If you have any questions about the test, contact your child’s neurologist or call the intervention radiology department at 416-813-6054 and choose option 1 or 3.