Wada Test
The Wada test, also known as the Intracarotid Amobarbital Procedure (IAP), combines neuroimaging and neuropsychological testing methods to examine memory and language functions. It is used to evaluate patients being considered for epilepsy surgery, by examining the independent functions of the brain.
The Wada test is part of the presurgical evaluation of people being considered for epilepsy surgery. It helps to determine what might be the best type of surgery for an individual. It is useful in determining which hemisphere is "dominant" for speech and if memory is functional on one or both sides of the brain. It is important to know where speech and memory are located in the brain so that surgery does not affect these functions.
It was named after Dr. Juhn Wada, who developed the test.
Before for the Test
- On the day before the test, you will be scheduled to see a specialist who will obtain information about your speech, cognitive and memory functions.
- No jewellery or other metal objects should be worn during the test.
- You will not be able to drive home after the procedure.
- You must arrange with someone to pick you up after the test.
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. Some persons report mild discomfort when the needle is inserted.
- A small incision is made to allow a small tube (catheter) through your skin into the artery. The catheter will move into the vessels. You may feel some mild discomfort when the needle is inserted. Otherwise this procedure is painless.
- A fluoroscopy will be done, which shows the internal structure of your body by means of X-rays, and is 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 through the entire procedure.
- This part of the test takes approximately 1-2 hours depending on the number of blood vessels that need to be examined.
Part 2: Wada Test
- You will be injected with sodium amobarbital into the catheter. This injection 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 and you may not be able to speak immediately after the injection.
- Your may feel some temporary weakness. It is at this point that an assessment of your speech and memory will be made.
- You will be asked by the neurologist 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 5-10 minutes.
- This process is repeated with the other side of the brain.
After the Test
- The catheter will be removed. Pressure will be applied to that spot to prevent bleeding. A bandage will be placed on that spot and no stitches will be required. The nurse will ensure that your leg is kept 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 for you to drink lots of fluids.
- You will remain in the hospital 4-5 hours after the test, and then be able to go home with accompaniment. You will not be able to drive and must arrange with someone to pick you up after the test.
- You will be given 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 sensitivity to drugs such as local anaesthetics, barbiturates, X-ray dyes, etc.
- After the procedure, you may feel some tenderness and bruising at the injection site. Ice packs may be applied 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, a warm wet feeling or swelling in the groin.
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