The Wada test (named after Dr. Juhn Wada), also known as the intracarotid amobarbital procedure, is an important part of the pre-surgical evaluation in patients being considered for epilepsy surgery. It is especially important in patients with temporal lobe epilepsy. The main purposes of the Wada test are to determine if the right or left brain is dominant for language abilities, and to assess memory function on both sides of the brain. Because the test includes angiography it also provides a very accurate picture of blood vessels in the brain, which can help guide future brain surgery. The results of the test help the epilepsy team determine a surgical approach that minimizes the chances that language or memory will be affected by the epilepsy surgery.
The procedure is performed in the interventional radiology suite of the Radiology Department. The Wada test requires a multidisciplinary team consisting of a neuropsychologist, neurologist and a neuroradiologist. Throughout the procedure the patient is lying face up on a table. First, the neuroradiologist inserts a thin, flexible tube called a catheter into an artery in the groin area (the femoral artery), after numbing this area with a local anesthetic. With fluoroscopic (X-ray) guidance, the neuroradiologist carefully advances the catheter through several arteries until it reaches the internal carotid artery in the neck. The neuroradiologist then obtains a “cerebral angiogram” which is a detailed picture of the blood vessels in the brain.
Then, an anesthetic drug (usually sodium amobarbital) is slowly injected through the catheter into the left or right internal carotid artery, which puts the left or right brain to sleep for about five minutes. During this period of anesthesia the neurologist monitors the patient’s medical and neurological condition. At the same time, the neuropsychologist performs the memory and language testing. Once the patient has completely recovered from the amobarbital, the test is repeated with the drug injected into the other internal carotid artery. The neuropsychologist compares memory and language abilities on each side of the brain to help plan a surgery that will reduce the chances of memory or language problems.
Preparing for the Wada Test
A few weeks before the procedure you will have an appointment with the neuroradiologist, Dr. Sundeep Mangla. He will ask about your current medications, allergies, and medical conditions. He will ask you to have some blood tests in the week before the procedure. He will also give you specific instructions to follow beginning the night before the procedure, such as no eating or drinking after midnight, except for taking your medications with small sips of water.
Do not wear jewelry, or other non essential articles of clothing such as hair clips and pins. You may wear your glasses and dentures. Most patients are ready to go home 8 – 10 hours after the procedure. Be sure to arrange to have a friend drive you home, as using public transportation is strongly discouraged.