The Wada Test
Wada Testing | VNSC
The Wada test can be used by epilepsy doctors to evaluate how important each side of the brain is for a patient’s language and memory functions. The test is named after the Canadian neurologist and epileptologist, Dr. Juhn Atsushi Wada, of the University of British Columbia, who first wrote about it in 1949.
Data from the Wada test helps determine the best approach to address the patient’s seizures while protecting those areas of the brain associated with speech and memory. In most people, language is controlled by the left side of the brain, whereas both sides of the brain can control memory. By examining each side of the brain, one side at a time, the Wada test lets doctors know which side of your brain has better language and memory function.
Who Performs My Wada Test?
Neuroradiologists, interventional neurologists, and epileptologists specializing in epilepsy will typically perform your test.
Dr. M. Asif Taqi is a quadruple-board-certified neurointerventionalist with many years of experience. He has extensive expertise in neurology, vascular and critical care neurology, and neuroendovascular surgery. His advanced skills and caring manner make him one of Southern California’s most sought-after physicians.
What Are the Risks Associated with My Wada Test?
While risks are minimal, Dr. Taqi is fully prepared to help you through any situation. These include:
Reactions to the contrast dye may include hives, nausea, and itching. It is rare for patients to experience difficulty breathing. Be sure to let Dr. Taqi know if you are allergic to any dyes or have asthma.
Inserting a catheter requires the puncture of an artery. If blood leaks around the catheter into the tissue, a hematoma (a swollen blood-filled area) may result. It will initially be black and blue but will disappear in time as the body absorbs it.
While sodium amytal is a strong sedative, it rarely causes difficulty in breathing or low blood pressure.
How Do I Prepare for My Wada Test?
First, Dr. Taqi will discuss the procedure with you, and you will be asked to sign a consent form.
You may need to avoid certain medications containing aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and blood thinners for up to two weeks before your Wada test.
A “practice test” will be conducted the day before the procedure. At this time, Dr. Taqi will explain the test to you and rehearse the steps of the actual test.
What Happens on the Day of My Wada Test?
Make sure you wear comfortable clothing, do not wear makeup, and do not drink anything past midnight the night before. Take your morning prescription medications with as little water as possible.
On the day of your Wada test, you will have an angiogram, where x-ray pictures are taken of the arteries that supply blood to your brain. For this, a catheter will be inserted into an artery, usually in the groin area. A dye will then be administered through the catheter so that the blood vessels will show up on the angiogram, where they can be examined to make sure that there are no obstacles to performing the test.
Small, adhesive discs may be applied to your chest to monitor your heart, and Velcro strips placed across your head to prevent movement during the x-rays.
After the x-ray, and with the catheter still in place, the radiologist will administer a short-acting sedative (sodium amytal) through the catheter into the right and then left internal carotid arteries. When the right carotid is injected, the brain’s right side goes to sleep and cannot communicate with the left side. While this half of the brain is asleep, the other side of the brain continues to function as usual.
This way, each side of the brain can be tested separately for speech and memory. The sedative is applied in turn to each half of the brain, where it usually wears off entirely in 10-15 minutes.
After receiving the sedative, you will not be able to move one side of your body and may not be able to speak. To confirm that the sedated side of the brain is asleep, EEG (electroencephalogram) recordings are taken at the same time as the neurological examination.
What Happens During My Wada Test?
During the 10—15 minutes that each side of the brain is sedated, the testing team assesses your speech, memory, and other functions. Here, you will be asked to perform a set of tasks such as reading words and identifying objects, pictures, shapes, and numbers.
You will then answer a series of questions to assess your ability to recall or recognize the items described. Muscle responses in the strength of your hand or arm are also examined to determine motor function.
A video camera or sound recorder will record your speech and movements for further study.
The Wada test usually takes between 30—60 minutes to complete.
What Happens After My Wada Test?
At the end of your test, Dr. Taqi will remove the catheter and apply pressure to the blood vessel for 10—15 minutes until clotting at the incision forms a firm seal to prevent bleeding. The small incision will not need any stitches — only a small bandage.
To ensure full closure of the incision and reduce the risk of bleeding, you’ll need to stay where you are for 4—5 hours. Written instructions to follow at home are provided before you leave the medical facility.
After the test, your injection site may be tender and bruised. Elevating the leg and applying ice packs should help.
Things to Be Aware Of
Although the test is proven to be safe, Dr. Taqi will discuss possible complications before the procedure. To avoid complications, you must inform Dr. Taqi of any allergies or sensitivities to sleeping pills, barbiturates, local anesthesia, X-ray dye, etc.
While the Wada test is an outpatient procedure, it involves anesthesia. Therefore, you must bring someone to drive you home afterward. The Wada test will typically start in the morning, and you should go home by mid-to-late afternoon. Be sure to prepare everything you need at home beforehand.
Contact Dr. Taqi with Issues
Once you are at home, you or your family should inform Dr. Taqi or his team of any discomfort or unusual developments without delay.