Wada test
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The Wada test, also known as the "intracarotid sodium amobarbital procedure" (ISAP), is used to establish which cerebral functions are localised to which hemisphere.
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Method
The test is conducted with the patient awake. Essentially, an anesthetic (which is usually sodium amobarbital) is introduced into one of the internal carotid arteries via a cannula or intra-arterial catheter from the femoral artery. This has the effect of anesthetising one side of the brain (hemisphere). The patient then undergoes a neuropsychological assessment.
Uses
The test is usually performed prior to ablative surgery for epilepsy. The aim is to determine which side of the brain is responsible for certain vital functions including speech and memory. The risk of damaging such structures during surgery can then be assessed.
The Wada test has several interesting side-effects. Drastic personality changes are often noted in test subjects depending on which hemisphere is shut down. It is also the case that although the patient may not be able to talk, their ability to sing is preserved.
History
It is named after Dr Juhn Wada, who first described the procedure.