Most epilepsy patients considering surgery undergo the Wada (WAH-dah) test. The "Wada test" is named after the Japanese physician who first performed it, Juan Wada, MD.
The Wada test is used to determine which side of the brain controls language function and how important each side of the brain is in regard to memory function.
In most people, language (speech) is controlled by one side of the brain, the left side.
The Wada test will tell the doctors which side controls language in your brain. Memory can be controlled by both sides of the brain. The Wada test tells doctors which side of your brain has better memory function.
The Wada test looks at language and memory function on each side of the brain, one side at a time.
Below, find frequently asked questions about the Wada test.
Who performs the Wada test?»
Two doctors are usually involved in performing a Wada test: a neuroradiologist/interventional neurologist (who uses imaging devices and substances to study the brain) and an epileptologist (a neurologist who specializes in epilepsy).
What is an angiogram?»
An angiogram is conducted before the Wada test. This looks at blood flow within the brain to make sure that there are no obstacles to performing the Wada.
The neuroradiologist inserts a catheter (a long, narrow tube) into an artery in the leg. The catheter is directed to the right or left internal carotid artery in the neck, which supplies the brain with blood.
Once the catheter is in place, a dye is injected. Some patients report a warm sensation when this happens. The dye can be seen on a special x-ray machine. This machine takes pictures of the dye as it flows through the blood vessels of the brain. Once the angiogram is done, the catheter will stay in place for the Wada test.
What happens during the Wada test?»
During the Wada test, the neuroradiologist puts one side of your brain to sleep for a few minutes. This is done by injecting an anesthetic medication into the right or left internal carotid artery. If the right carotid is injected, the right side of the brain goes to sleep and cannot communicate with the left side.
In order to confirm that the injected side of the brain is asleep, EEG (brain wave) recordings are done at the same time with the neurological examination that is performed by the neurologist.
Once the physicians are sure that one side of your brain is asleep, the epileptologist will evaluate your ability to speak and will also show you individual cards of pictures and words. The awake side of the brain tries to recognize and remember what it sees.
After just a few minutes, the anesthetic wears off. The side that was asleep starts to wake up. Once both sides of your brain are fully awake, the epileptologist will ask you what was shown. If you do not remember what you saw, items are shown one at a time, and you are asked whether you saw each one before. Your responses will be recorded.
After a delay, the other side of your brain is put to sleep. To do this, the catheter is withdrawn part of the way and threaded into the internal carotid artery on the other side. A new angiogram is done for that side of the brain.
Different objects and pictures are shown, and the awake side (which was asleep before) tries to recognize and remember what it sees. Once both sides are awake again, you will be asked what was shown the second time. Then you are shown items one at a time and asked whether you just saw each item.
How long does the Wada test take in total?»
The length of the Wada test can vary between medical centers. The usual test takes between 30 and 60 minutes to complete.
What do the test results mean? How are they interpreted?»
Your doctors will compare language and memory function results obtained from each side of your brain to determine which is the dominant side for these functions. They will compare this information with other tests that show the location of your seizures in your brain.
If the side of the brain that controls language, or has better memory, is where your seizures may be coming from, the surgeon may consider performing brain mapping before (or during) surgery. [Brain mapping is a method, using various technologies, to "map out" the exact location of the brain's functions and brain disorders.]
All the information considered helps your doctors determine if surgery can be performed without harm to your language and memory functions after surgery.
Is the Wada test safe?»
A Wada test is generally a safe procedure with very few risks. There is a small risk of some complications. These complications can be as minor as pain where the catheter is inserted or as serious as a potential stroke.
Because it is considered an invasive procedure, it does carry the risk of bleeding and infection. The overall risk of stroke is less than 1 percent. It is greater, but still relatively low, if you are older, if you have atherosclerosis (hardening of the arteries) or a history of high cholesterol.
Can the Wada test be performed in both children and adults?»
Yes, the test can be performed in children as well as adults providing they are of a sufficient age and maturity to participate in this interactive test.
Is there any special preparation for the Wada test?»
You cannot have anything to eat or drink after midnight the night before this test. Do continue to take any prescription drugs as scheduled.
What is the recovery time after the procedure?»
You will be on bed rest with bathroom privileges the remainder of the day in the hospital. The nurses and doctors will be checking the pulses in the leg where the catheter was inserted and will also check under the dressing.
Sensory checks will also be done throughout the day. This is done to ensure there has not been a disruption in circulation to the affected leg.
You will be discharged later in the day and will be given an at-home instruction sheet. You are asked to avoid strenuous activity for at least 24 to 48 hours after the procedure.
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