Wada test Wada test (amytal test)
It is a study that was described by Dr. Jung Wada (an epilepsy specialist from Canada). This study is another part of the pre-surgical evaluation to assess speech and memory in order to prevent damage from the surgery.
Technically the patient undergoes an angiogram (a study of the brain arteries). A catheter (long, thin tube) is inserted in the groin area and is guided up into one of the two carotid arteries (artery in the neck that takes the blood to the brain). Each side of the brain is studied separately through this procedure. A barbiturate (usually amytal) is injected into the carotid artery and the blood carries it to one half of the brain (hemisphere). This barbiturate is short acting (few minutes) and puts that half of the brain to sleep. This produces paralysis of the opposite side of the body (remember anatomic rules) and paralysis of the speech area and memory area (if these areas are on that side of the brain). This procedure allows the doctors to assess how the other half of the brain (the one that is not asleep) functions all by itself. Then, after some time (the length of time differs from center to center; for us it is about an hour) the same procedure is repeated on the other half of the brain. During the time that the half of the brain is asleep (usually a few minutes) testing of speech and memory is performed. Speech is assessed by talking to the patient. If the speech area is asleep the patient will not be able to speak or respond to commands. For example, if the left half of the brain is asleep and the patient cannot speak, but can speak when the right half is asleep it tells us that the left side is the one that holds the speech center (called left sided dominance for speech). Memory is assessed by showing objects to the patient while he/she is under the effect of the barbiturate. Once the effect of the barbiturate is gone (when the brain “wakes up”), the patient is asked to recall and recognize the objects. This information is very important to understand how memory works for the patient. For example, if we plan to remove part of the left half of the brain, we want to make sure that the right side of the brain has healthy memory functions so the patient will have memory that is acceptable after the surgery