Wada Test

What is a Wada test?

The Wada test is a procedure your healthcare provider may perform before epilepsy or brain tumor surgery. The procedure 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) determine whether or not you may be at risk of changes to your speech or memory after your surgery.

Dr. Juhn Wada first performed the procedure in 1949. Other names for the test include:

• Intracarotid amobarbital test.
• Intracarotid sodium amobarbital procedure.
• Sodium amytal test.
• Amytal study.

Other tests your healthcare provider may use before performing epilepsy surgery include:

• Functional magnetic resonance imaging scan (fMRI).
• Transcranial magnetic stimulation.
• Neuropsychiatric testing.

Which side of the brain controls language?

The left side of the brain controls speech for most people. 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. Generally, in left hemisphere language dominant people, the left side of the brain is important for verbal memory and the right side of the brain is important for visual memory. The Wada test tells your healthcare provider which side has better memory function.

Who can be tested?

Both children and adults can get the Wada test. But 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 during the test.

Who performs the Wada test?

A team of specialists will perform the Wada test:

• An epileptologist: A neurologist who specializes in epilepsy.
• An interventional neuroradiologist: A physician who has expertise in performing catheterization procedures. They position the catheter into each carotid artery for delivery of the anesthetic medication during the Wada test.
• A neuropsychologist: A specialist in how brain conditions affect your behavior and cognitive skills.

How do I prepare for a Wada test?

Your healthcare provider may ask you to avoid certain medications up to two weeks before the procedure. These include aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs) and blood thinners. But you should continue to take any prescription medications as scheduled unless your provider tells you otherwise. It’s also important to tell your provider if you have any allergies to any medications.

What happens before the Wada test?

Before your procedure, you’ll change into a gown and a healthcare provider will shave your groin region because they’ll need to access a blood vessel in this area. In the testing room, a 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 providers will then numb the skin in your groin region. Once that area is numb, 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 called the carotid artery. While that’s happening, you may experience a metallic taste in your mouth and a warm sensation. You may feel some pressure, but it shouldn’t be painful.

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 performed?

Your interventional 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’ll momentarily lose your ability to move the opposite side of your body. Your healthcare providers will confirm that your brain is asleep by checking the EEG recordings.

Once your providers are sure that one side of your brain is asleep, your epileptologist or neuropsychologist 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 weakness and difficulty speaking. This is typical. You might also fall asleep.

Sometimes, people are unable to speak during the test. In some circumstances, the test may be less useful:

• When children are younger than 10 years.
• If seizures occur during the testing.
• People who have an IQ (intelligence quotient) below 70.

Healthcare providers will be there to help in case you experience 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 or neuropsychologist will ask what you remember. If you don’t remember, they’ll show you the cards one at a time and ask if you’ve seen them before. It’s OK if you don’t remember what you saw on the cards.

After a while, your healthcare providers will put the other side of your brain to sleep. They’ll pull the catheter back a little and then gently push it 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.

Is the WADA test performed on an awake patient?

Yes, you’ll be awake for the procedure.

How long will the test last?

The length of the Wada test can vary between medical centers, but the total time it takes is typically about three to four hours. In most situations, both sides of your brain are tested during the test. You’ll wait for some small period of time until you have completely recovered before they start the second side

What happens after the test?

You’ll stay in the recovery unit to rest after the test. 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 this to make sure you have your usual circulation in your leg.

You’ll be allowed to go home later in the day. You’ll likely be told to avoid strenuous activities for 24 to 48 hours.

Is the Wada test invasive? Are there any risks or side effects?

The Wada test is safe and low-risk. If you have any Wada test side effects, it’ll likely be pain where the catheter was put in (after the numbing drug wears off). Rare complications include:

• Seizure.
• Encephalopathy.
• Stroke.

Because it’s an invasive procedure, the Wada test does carry a small risk of bleeding and infection. The risk is greater, but still relatively low, if:

• You’re age 65 or older.
• You have atherosclerosis (hardening of the arteries).
• You have a history of high cholesterol.

What do the Wada test results mean?

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 the data is compiled, your surgeon will be able to determine if any additional risks from brain surgery might affect your language and memory functions.