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 for the Test
- On the day before the test, you must schedule an appointment for your child to see a specialist. The specialist will gather information about your child’s speech, cognitive and memory functions.
- Remove any jewellery or other metal objects your child may be wearing during the test.
During the Test
Part 1: Angiography
- Your child will lie on his/her 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. Inform your child that s/he 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 child’s 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.
- Inform your child that s/he may experience a feeling of heat, pressure and sometimes pain for approximately 10 to 20 seconds.
- Your child may get a metallic taste in his/her mouth, but this taste will subside.
- Inform your child that s/he may hear noises from the X-ray machine as it takes images of the dye passing through the blood vessels.
- Your child must remain still through 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.
- Your child will not be able to move the side of the body opposite the injection immediately after the injection.
- Your child may not be able to speak immediately after the injection.
- Your child may feel some temporary weakness. This is the time to assess his/her speech and memory.
- The neurologist will ask your child to identify pictures, words, objects, shapes and numbers. Your child 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 Testthe 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 your child keep his/her leg straight or elevated to prevent the puncture site from bleeding.
- The X-ray dye will cause your child to urinate more than usual. It is important for your child to drink plenty of fluids.
- Your child will remain in the hospital four to five hours after the test before you can take him/her home.
- You will get written information for your child’s home care after leaving the hospital.
- physicians (neurologists and neuroradiologists)
- neuroradiology technologists
- physician assistants
- EEG technicians
The test is covered by the Ontario Health Insurance Plan (OHIP).
- Notify the doctor if your child has any allergies, or sensitivity to drugs such as local anaesthetics, barbiturates, X-ray dyes, etc.
- After the procedure, your child may feel some tenderness and bruising at the injection site. Ice packs may be applied to this area to ease the pain.
- Let your child know that if s/he feels any discomfort such as nausea, coldness, headache, numbness in the foot, a warm wet feeling or swelling in the groin, s/he should tell the nurse immediately.