The Wada test is used when you and your healthcare provider are considering brain surgery for your epilepsy. It answers two questions about your brain:
- Which side of your brain (left or right) controls your language functions?
- How important is each side of your brain regarding your memory functions?
The Wada test helps your neurosurgeon (brain surgeon) predict whether or not you’ll have changes to your speech or memory after your surgery. During your surgery, your surgeon will do their best to avoid those language and memory areas.
The Wada test isn’t used as much these days as other less invasive tests such as a functional magnetic resonance imaging scan (fMRI) and transcranial magnetic stimulation.
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| Wada test |
Which side of the brain controls language?
Most people have their speech controlled by the left side of their brain. The Wada test is necessary because this isn’t always the case (particularly in people who are left-handed).
Which side of the brain controls memory?
Both sides of your brain can control memory. The Wada test tells your healthcare provider which side has better memory function.
Can pregnant women get the Wada test?
No, because the test involves radiation.
Who can be tested?
Both children and adults can go through the Wada test. However, your child has to be old enough and mature enough to talk and understand in order to take part in the test. A toddler wouldn’t understand the words shown to them.
Who performs the Wada test?
An epileptologist (a neurologist who specializes in epilepsy) and a neuroradiologist/interventional neurologist/neurosurgeon (who uses imaging devices and substances to study the brain) will carry out your Wada test.
How do I prepare for a Wada test?
You can’t eat or drink anything after midnight.
Should I take my medications before the test?
Yes, take any prescription medications as scheduled.
What happens before the Wada test?
Before your procedure, you’ll change into a gown and your groin regions will get shaved. In the testing room, your healthcare provider will prepare you for an electroencephalogram (EEG) by gluing electrodes to your scalp. The EEG will measure your brain activity during the test.
Your healthcare providers will then numb the skin in your groin regions. Once you can’t feel anything, they’ll insert a needle into a blood vessel located in your leg. Next, they’ll put a long, skinny tube called a catheter into the blood vessel. They’ll advance the catheter into an artery in your neck. While that’s happening you may experience a metallic taste in your mouth and a warm sensation. You may feel some pressure, but it won’t be painful.
The Wada test won’t actually start at that point. Before the Wada test, you’ll get an angiogram. An angiogram looks at the blood flow in your brain to make sure there are no problems with the Wada test.
How is the Wada test done? What happens during the Wada test?
Your neuroradiologist will put half of your brain to sleep by putting an anesthetic medication through the catheter into your left or right carotid artery. If the medicine goes into your right carotid, the right side of your brain won’t be able to communicate with the left side of your body. When that happens you may see stars, feel pressure behind your eye and your face might get warm. You will momentarily lose your ability to move the other side of your body. Your healthcare providers will confirm that your brain is asleep by checking the EEG recordings.
Once your healthcare providers are sure that one side of your brain is asleep, your epileptologist will test your ability to speak and show you cards with words and pictures. They’ll tell you to try to remember what you see.
You may have difficulty with speaking, and weakness. This is normal. You might also fall asleep.
Sometimes, children are unable to speak during the test. If your child is younger than 10, if their seizures come from the dominant side of their brain or if they have an IQ (intelligence quotient) below 70, they’re more likely to struggle with the test. Healthcare providers will be there to help your child with any fear or anxiety.
The anesthetic will wear off after just a few minutes and the sleeping side of your brain will wake up. At that point, the epileptologist will ask what you remember. If you don’t remember, they’ll show you the cards one at a time, and ask if you saw them before.
It’s all right if you don’t remember what you saw on the cards! It doesn’t mean there’s anything bad or wrong with your brain!
After a while, your healthcare providers will put the other side of your brain to sleep. The catheter will be pulled back a little, and then gently pushed into the second internal carotid artery. They’ll do another angiogram.
Again, you’ll see cards – different ones. Once you’re fully awake, you’ll be asked once more what was on the cards.
Will I be awake during the test?
Yes, you should be awake.
How long will the test last?
The length of the Wada test can vary between medical centers. The usual test takes between 30 and 60 minutes to complete.
What happens after the test? What’s the recovery time?
You’ll stay in the recovery unit to rest after the test. Every once in a while your healthcare providers will check your pulse in your leg where the catheter was inserted. They’ll also check the bandages that cover the incision (cut) in your groin region and make sure your sense of touch has completely returned. They do all of this to make sure you have normal circulation in your leg.
You’ll be allowed to go home later in the day. You’ll likely be told to stay away from strenuous activities for about 24 to 48 hours.
Is the Wada test dangerous? Are there any risks or side effects?
The Wada test is safe and low-risk. If you have a side effect, it will likely be pain where the catheter was put in (after the numbing drug wears off). Rare complications include:
- Seizure. The overall risk of stroke is less than 1%.
- Encephalopathy.
- Stroke.
Because it’s an invasive procedure, the Wada test does carry a small risk of bleeding and infection. It’s greater, but still relatively low, if you’re older, if you have atherosclerosis (hardening of the arteries) or a history of high cholesterol.
What do the test results mean? How are they interpreted?
The Wada test helps your treatment team determine which side of your brain is dominant for language, and which side is dominant for memory. They’ll compare the data with past tests that show the location of seizures in your brain. Once all of the data is compiled, your surgeon will be able to determine if the brain surgery might harm your language and memory functions.
