The Wada test, also known as the Intracarotid Amobarbital Procedure (IAP), was named after Dr. Juhn Wada. He developed the combination of neuro-imaging and neuropsychological testing methods to examine independent functions of the brain such as memory and language. It is useful in determining which hemisphere is “dominant” for speech and if memory is functional on one or both sides of the brain.
The Wada test is part of the pre-surgical evaluation for people being considered for epilepsy surgery. It helps to determine what might be the best type of surgery for an individual. It is important to know where speech and memory are located in the brain so that surgery does not affect these functions.
Before the Test
- A specialist will schedule an appointment with you to gather information about your speech, cognitive and memory functions.
- Do not wear jewellery or other metal objects during the test.
- You must arrange someone to pick you up after the test as you will not be able to drive home after the procedure
During the Test
Part 1: Angiography
- You will lie on your back on the X-ray table.
- A local anaesthetic will be injected into the groin.
- This injection may cause a slight pressure and burning sensation.You may feel some mild discomfort when the needle is inserted. Otherwise this procedure is painless.
- A small incision allows a small tube (catheter) to enter through your skin into the artery. The catheter will move into the vessels.
- A fluoroscopy will show the internal structure of your body by means of X-rays. This will be visible on a monitor.
- Dye will be injected through the catheter as the X-rays are taken.
- You may experience a feeling of heat, pressure and sometimes pain for approximately 10 to 20 seconds.
- You may have a metallic taste in your mouth, but this taste will subside.
- You may hear noises from the X-ray machine as it takes images of the dye passing through the blood vessels.
- It is important that you remain still throughout the entire procedure.
- This part of the test takes approximately one to two hours depending on the number of blood vessels that need to be examined.
Part 2: Wada Test
- Sodium amobarbital will be injected into the catheter. This will cause one side of the brain to “sleep” while the other side continues to function as usual.
- Immediately following the injection, you will not be able to move the side of the body opposite the injection.
- You may not be able to speak immediately after the injection.
- You may feel some temporary weakness. This is the time to assess your speech and memory.
- The neurologist will ask you to identify pictures, words, objects, shapes and numbers. You will have to answer questions and remember what is shown.
- The effects of the drug will wear off in about five to 10 minutes.
- This process is repeated with the other side of the brain.
After the Test
- The catheter will be removed.
- Pressure and a bandage will be applied to the puncture site to prevent bleeding. No stitches will be required.
- The nurse will ensure that you keep your leg straight or elevated to prevent the puncture site from bleeding.
- The X-ray dye will cause you to urinate more than usual. It is important to drink plenty of fluids.
- You will remain in the hospital four to five hours after the test before you are able to go home with accompaniment.
- You will not be able to drive. Arrange with someone to pick you up after the test.
- You will get written information for home care after leaving the hospital.
Personnel
- physicians (neurologists and neuroradiologists)
- neuroradiology technologists
- nurses
- physician assistants
- neuropsychologists
- EEG technicians
Payment
The test is covered by the Ontario Health Insurance Plan (OHIP).
Important Considerations
- Notify the doctor if you have any allergies or sensitivities to drugs (local anaesthetics, barbiturates, X-ray dyes, etc.).
- After the procedure, you may feel some tenderness and bruising at the injection site. You may apply ice packs to this area to ease the pain.
- You should inform the nurse if you feel any discomfort such as nausea, coldness, headache, numbness in the foot or a warm wet feeling or swelling in the groin.
