The Wada test helps surgeons identify areas of the brain responsible for language and memory before epilepsy surgery. An anesthetic is injected into one of two carotid arteries to put one hemisphere of the brain to sleep at a time, and the patient’s response to speech and ability to recall details are observed. The test has a low risk of stroke, but patients may experience headaches and localized pain.
Doctors and surgeons use certain tests to find out more details about specific diseases. The Wada test, named after the doctor who devised it, is used with patients who are about to undergo brain surgery for epilepsy. Using a combination of anesthetic and behavioral observation, the test helps surgeons pinpoint areas of the brain that patients use for language and memory. This information helps your doctor evaluate whether the brain tissue causing epilepsy can be removed without harming these functions.
Epilepsy involves a malfunction of the brain’s electrical signals that can be improved with surgery. Different areas of the brain are responsible for certain functions, ranging from movement to emotions. A surgeon must balance the possibility of improvement in epilepsy against the risk of damage to important brain functions when considering surgery. The areas responsible for using language and remembering the past may be present mainly in one side, or hemisphere, of the brain; or they can be present in both.
When a candidate for epilepsy surgery has most of both of these functions on one side of the brain, then the surgeon has a lower risk of creating permanent damage to these functions when operating on the other hemisphere. To verify this, he performs a Wada test, which involves putting one hemisphere of the brain to sleep at a time. Typically, doctors inject an anesthetic into one of two carotid arteries, both of which supply blood to different hemispheres of the brain.
With each hemisphere asleep, one at a time, the doctor checks how the patient responds to speech and whether he is able to speak normally. The patient’s ability to recall details from the flashcards is also observed. Normally, the patient also wears electrodes on their head which ensure that the brain is sufficiently asleep for the Wada test to be valid. Since the carotid artery is an important blood vessel, the risk of serious blood loss is high, so the patient should lie down for several hours after completing the Wada test.
A low risk of stroke is associated with this procedure, but less serious effects such as headache and pain localized to the injection site are more common. To make the test as accurate and safe as possible, a doctor who specializes in epilepsy and a doctor experienced in brain imaging may be present. Typically, the patient can go home the same day and only needs to take care of themselves for two days after the test.
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