Wada Test

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Determining if surgery is the appropriate treatment for epilepsy

Patients with seizures that begin from a single "hot spot" or seizure focus may benefit from a surgical treatment to remove the hot spot, if this can be done without injury to other parts of the brain. At the UC San Diego Epilepsy Center we perform intense evaluations to determine whether epilepsy surgery may help control seizures that cannot be controlled by medicine alone. One evaluation is called the Wada test, named after neurologist Juhn Wada. The purpose of the Wada test is to ensure that epilepsy surgery will not result in language or memory deficits. The series of images and captions below show the steps of the Wada test.

Dr. Khalessi, neurosurgeon and neurointerventionalist, prepares the patient for the Wada test by running an intra-arterial catheter from his femoral artery (in the thigh) to the first carotid artery.
The doctors use an imaging technique called angiography to watch as the catheter reaches its destination in the arteries that supply blood to the brain.
The patient is awake during the Wada test. Electrodes placed on his head monitor electrical activity in his brain.
When the catheter has reached the first carotid artery, Dr. Khalessi and Dr. Tecoma, neurologist and epileptologist, watch as contrast is injected into the arteries of the brain to make sure the medication will be injected in exactly the right place. Then the medication is injected into one hemisphere of the patient's brain. The drug temporarily shuts down language and memory function in that hemisphere in order for the physicians to evaluate the language and memory function of the other half of the brain.
Dr. Norman, neuropsychologist, begins the test, asking the patient to raise his right arm.
A neuropsychologist asks the patient to identify various household objects including a toothbrush and a roll of tape.
The patient reads a sentence from a notebook.
The medical team watches as the patient works to read, identify objects, count backwards and engage in other language and memory related tasks.
Dr. Tecoma examines the electroencephalograph (EEG) which is measuring the electrical activity in the brain.
Dr. Tecoma records her observations on the EEG changes as the anesthesia is injected into the carotid artery. She confirms that the anesthesia has produced the desired effect in targeted brain areas.
After completing the test on one hemisphere of the brain, the medication quickly dissipates, and the patient recovers full brain function in a few minutes. Then the patient is prepared for the second half of the test, where the anesthesia is injected in the other hemisphere through a catheter in the opposite carotid artery. The tasks are repeated to evaluate the patient's language and memory function when the other half of his brain is “shut down.”