Wada test
| Wada test | |
|---|---|
| Intervention | |
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| ICD-9-CM | 89.10 |
The Wada test, also known as the intracarotid sodium amobarbital procedure (ISAP) establishes cerebral language and memory representation of each hemisphere.
Medical professionals conduct the test with the patient awake. Essentially, they introduce a barbiturate (usually sodium amobarbital) into one of the internal carotid arteries via a cannula or intra-arterial catheter from the femoral artery. They inject the drug into one hemisphere at a time into the right or left internal carotid artery. If the right carotid is injected, the right side of the brain is inhibited and cannot communicate with the left side. The effect shuts down any language and or memory function in that hemisphere in order to evaluate the other hemisphere ("half of the brain"). An EEG recording at the same time confirms that the injected side of the brain is inactive as a neurologist performs a neurological examination. The neurologist engages the patient in a series of language and memory related tests. They evaluate the memory by showing a series of items or pictures to the patient and—within a few minutes, as soon as the effect of the medication dissipates—testing the patient's ability to recall. The test is typically administered by a neuropsychologist as a result of expertise in psychometric testing. Correlation with formal neuropsychological testing has some predictive power regarding seizure outcome following anterior temporal lobectomy.
There is currently great variability in the processes used to administer the test, and so it is difficult to compare results from one patient to the other.
The test is usually performed prior to ablative surgery for epilepsy and sometimes prior to tumor resection. The aim is to determine which side of the brain is responsible for certain vital cognitive functions, namely speech and memory. The risk of post-operative cognitive change can be estimated, and depending on the surgical approach employed at the epilepsy surgery center, the need for awake craniotomies can be determined as well.
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