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Patients considering surgery foe epilepsy undergo the Wada test. This test is officially known as the intracarotid sodium amobarbital procedure (ISAP), but the nickname "Wada test" is commonly used. The name comes from the physician who first performed it, Dr. Juhn Wada.
The Wada test looks at language and memory on one side of the brain at a time. Language (speech) is controlled by one side of the brain (in most people, the left side), and the Wada will tell the doctors which side controls language in your brain. Memory can be controlled by both sides of the brain; the Wada tells which side of your brain has better memory. If the side that controls language or has better memory is where your seizures may be coming from, the surgeon may consider performing an fMRI or brain mapping before surgery.
During a Wada, the neuroradiologist puts one side of your brain to sleep for a few minutes. This is done by injecting sodium amobarbital (also called sodium amytal) into the right or left internal carotid artery. If the right carotid artery is injected, the right side of the brain goes to sleep and can't communicate with the left side. Once the physicians are sure that one side of your brain is asleep, the neuropsychologist shows you objects and pictures. The awake side of the brain tries to recognize and remember what it sees.
After just a few minutes, the sodium amobarbital wears off. The side that was asleep starts to wake up. Once both sides of your brain are fully awake, the neuropsychologist will ask you what was shown. If you don't 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 word-for-word.
After a delay, the other side of the brain is put to sleep.
Functional magnetic resonance imaging (fMRI) of the brain reduces the need for invasive testing of seizure disorder patients being considered for surgical treatment. fMRI can be used to localize seizure foci through detecting these cerebral hemodynamic changes produced by epileptiform discharges. fMRI is also useful in language and memory cognitive function assessment and presurgical assessment of refractory epilepsy.
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