Perspectives on the Wada test

Following are some thoughts by Stacy Zaferes, a patient with epilepsy who had a Wada test, ending with the transcript of a conversation between Stacy and Dr. William Barr, a neuropsychologist involved in Wada testing:

Prior to my brain surgery, I was given a test to determine if language and memory reside in the side of my brain not causing seizures. The Wada test is given by injecting sodium amytal [amobarbital] into the left and right internal carotid arteries, at separate times, causing a "freeze" (that is, putting part of the brain to sleep) to determine individual capabilities. The patient is then shown objects and asked for their names. The freeze wears off after approximately 4 minutes. Choosing which objects were shown during the freeze tests memory. The test is repeated on the opposite side. The frozen right side is where I saw beautiful objects. Reality, post-freeze, showed me battered items. Afterwards I was told of representations of past experiences, residing in the left side, which make an individual unique.

I spoke with neuropsychologist Dr. William Barr of the New York University Comprehensive Epilepsy Center. While in graduate school, Dr. Barr found the Wada test to be an interesting angle to study and measure the behavior of the brain.

Q: What does Wada mean?

A: It's a guy's name: Juhn Wada from Japan. The original test was an experiment tried in the late 1940s to look at language and schizophrenia. He figured out a way to put half the brain to sleep and talk to the other [half], which would enable him to determine if language was on that side of the brain or not. It wasn't well known by the western world until later. People in Montreal, where a lot of the early epilepsy surgeries were performed, worked with Dr. Wada to adapt the procedure for use with epilepsy surgery patients in the 1960s.

Q: What was the outcome of early epilepsy surgeries?

A: Considering the lack of the technology used, fairly good. One notable exception was an individual that had epileptic seizure foci on both sides of the brain. They removed the mesial temporal lobes from both sides. They rationalized, "Oh, both sides are [causing seizures]! It's not like a kidney or anything. It's the brain and since both sides are bad, let's take them out." The patient was left without memory. Anything he's supposed to remember after even a short passage of time is gone. They learned at that point that the hippocampus and other parts of the mesial temporal lobes, where most seizures come from, are important for memory. They then decided to do only one side at a time and found that some people [still] had amnesia afterwards. In a couple of the cases [these] people happened to die of other causes. They did autopsies and found that brain structures on the opposite side were abnormal. Now [the physicians] needed a way to determine if the other side is working OK. They found this Wada technique of putting the hemispheres to sleep individually. The hemispheres of the brain work separately only during the Wada test.

Q: Because you're putting one side to sleep?

A: Exactly. The purpose of the Wada test is to mimic the effects of surgery. The two sides of your brain are connected. These two sides are always working together. During the Wada test you put one side to sleep to see if the other can talk and remember. That's the whole basis of the test.

Q: Why put to sleep the side that's not to be touched surgically?

A: To determine if language and memory are represented in both hemispheres. Looking at the relative strengths and weaknesses of both sides provides additional confirmation regarding the side of the seizure focus. The Wada test doesn't tell you exactly where functions reside. It does tell you which hemisphere is more or less involved in a given function and which is functioning better.

Q: Is memory in other areas?

A: Memory takes our whole brain.

Q: What happens when the test results are in?

A: We communicate to the epilepsy surgery team. We take these findings and show whether there is adequate memory to sustain memory functions after the surgery. Essentially, whether the patient is going to miss out on having this part of the brain. Afterwards we need to conduct other procedures to find out exactly where in the left hemisphere is language and whether it is anywhere close to where the surgeon is going to cut. What the surgeon does is try to avoid any area that has language function.

Q: If the seizures start where language is, would the surgery not be performed?

A: It depends on how extensive the epilepsy is and how abnormal that part of the brain is. It may be a difficult decision to make. One needs to determine the positives and negatives here.

Q: Are you a part of that decision process?

A: It's a team decision. I'm the messenger on the potential for problems in these cases.