A Wada test is conducted, in some cases, prior to epilepsy surgery to help the treatment team better understand how your child’s brain is organized. The two halves of the brain (the left and right cerebral hemispheres) are associated with different aspects of thinking (cognitive functioning). For example, in the vast majority of right-handed individuals, we know that most aspects of language processing are located on the left side of the brain (the left cerebral hemisphere). We also know that, in some left-handed individuals, language processing may be located on the right side of the brain (the right cerebral hemisphere) or on both sides of the brain.
In addition, research tells us that individuals with abnormalities in brain development may have atypical organization of cognitive functions, which can make it difficult to predict where certain skills are located in the brain. Because of these issues, the epilepsy team will sometimes recommend that a child undergo a Wada test to determine which cerebral hemisphere controls language and memory functioning. This information is used in conjunction with other diagnostic procedures to help determine the safest approach to surgical intervention.
What to Expect
Wada tests (or intracarotid amobarbital studies) are conducted by the neuropsychologist, epileptologist, and neurointerventionalist. Prior to the procedure, you and your child will meet with the neuropsychologist to review the details of the test and rehearse how the test will be conducted. This serves to prepare your child for the procedure, and it allows the neuropsychologist to establish your child’s baseline level of functioning.
On the day of the Wada test, the neurointerventionalist will perform an angiogram on your child, which requires the insertion of a catheter into the femoral artery. The catheter is subsequently maneuvered through the vascular system until it reaches one of the internal carotid arteries. Once your child is ready, a short-acting anesthetic is released into the internal carotid artery that essentially puts to sleep one half of your child’s brain for a period of 3 to 4 minutes. During this time, the epileptologist monitors the EEG to ensure that the anesthetic has the desired effect, and the neuropsychologist presents stimuli to your child, such as pictures, words, and objects. After the anesthetic wears off, the neuropsychologist will ask if your child remembers anything that was presented.
Once the test is completed, your child will be allowed to rest for a short period and then the neurointerventionalist will maneuver the catheter to the internal carotid artery on the opposite side. Once in place, the Wada test is repeated for the other half of the brain. The neuropsychologist will present a second set of stimuli and again ask your child to remember what was presented after the anesthetic wears off.
After both cerebral hemispheres have been evaluated, the Wada test is complete and the neurointerventionalist removes the femoral catheter. The epileptologist will review the EEG, the neurointerventionalist will report on the angiogram, and the neuropsychologist will interpret the functional results of the Wada test.