Wada test

Brain surgery is a highly invasive procedure and many parents express concern about how the surgery will affect their child’s function. Fortunately, there are tests to predict whether a child will experience changes in language or memory after surgery. The most common of these is called the Wada test.

The Wada test is performed by a team of specialists in neurology, neuropsychology and neurophysiology. During the test, most of the left or right side of the brain is numbed with a heavy sedative known as a baribituate. This is done by injecting the barbituate into the body through the carotid artery in the neck while the child is alert and lying on a table. The barbituate creates a temporary injury on the brain that mimics the type of reaction that could occur after surgery. The specialists then test the child’s language and memory skills.

If the test predicts language or verbal memory delays, the child will likely experience issues on the dominant side of the brain following surgery. If the test predicts delays in visuospatial memory, the child may have issues on the non-dominant side. Delays in all three areas (language, verbal memory and visuospatial memory) suggest the child may experience issues on both sides of the brain.

The Wada test has several advantages over other predictive tests. For example, it can evaluate each side of the brain separately, which allows specialists to identify where seizures begin in the brain. However, the test stumbles over certain limitations—in some cases, children are not able to speak because of the simulated damage, which makes it difficult to assess language. The test is least helpful in children with an IQ below 70, those younger than 10 years or if seizures come from their dominant hemisphere, especially the left side.

Because the test simulates the effects of brain surgery, children may become scared or uncomfortable during the test. Coaching and behavioral intervention can help with anxiety, but is less helpful in young children or those with existing cognitive delays. Sedation may help children with sensory issues, but sedatives can cause disorientation and make Wada testing difficult.

In rare circumstances, children experience seizures, encephalopathy or stroke during the test. Because of these concerns, many doctors opt for less invasive ways of predicting a child’s outcome. Many treatment centers are now transitioning to fMRI instead of Wada tests.