WADA TEST
The WADA test, named after Dr. Jun Wada who first described and implemented the test, was originally designed to determine what side of the brain predominantly held speech and language. Its purpose has expanded to include a test of memory localization as well. The WADA test (now also referred to as the Intracarotid Amobarbital Procedure or IAP) is a minimally invasive study that is performed along with an angiogram; it is a “same-day” procedure (the patient arrives at the hospital in the morning and leaves later in the day). First a routine cerebral angiogram is performed to view the cerebral circulation (arteries and veins). Before the test starts, the patient is shown cards with pictures, symbols, and words to read and remember. Recall is then tested to determine baseline language and memory function. Sodium amytal (amobarbital) is then injected at a pre-measured dose, through a catheter into one carotid artery. It works like anesthesia and puts one cerebral hemisphere (half of the brain) to sleep, mimicking the effects of a surgical resection. The drug’s efficacy is measured by observed arm and facial weakness on the side of the body opposite of the injected cerebral hemisphere. Once this weakness is observed, the test can begin. The patient is again presented with cards to read and view, and then tested for recall 10 minutes later. The effect of the drug is short-lived (few minutes). Approximately 30-60 minutes after the drug has worn off, the opposite carotid artery (brain hemisphere) is injected and the process is repeated. Once the testing is complete, the catheter is removed, a gauze bandage is applied with pressure to the wound, and the patient recovers in the hospital for a brief period of time before being discharged. The information acquired during the WADA test is presented during the epilepsy surgery conference. No other non-invasive modality has been developed or is considered to be reliable enough to implement instead of the WADA test. In most cases, a standard WADA test, as described above, is sufficient. In special circumstances, however, a selective WADA or IAP is performed to study the effects of putting other temporal lobe and extra-temporal lobe structures to sleep.