What is a WADA exam?
A WADA exam is also known as an intracarotid amytal test. It
is one of the “non-invasive” tests used to determine which hemisphere is
language dominant in epileptic patients and also assess the ability of the non-affected
side to maintain memory when isolated. For example, if you were to remove the R
hippocampus – could the L side support language and memory alone?
No test is perfect... here are a couple of the WADA Shortcomings:
- If patient has a high flow AVM – reading can be inaccurate
- A portion of the hippocampus that you are trying to shut down could get its blood supply from posterior circulation making it hard to tell how accurately the patient will respond with full resection.
How is it done?
- Get angiogram (to assess cross flow – which is a contraindication to shutting down the side of primary supply)
- Cath ICA (usually start on lesion side)
- Ask pt to hold opposite arm in the arm as amobarbital is rapidly injected into the ICA
- What should happen? An almost immediate flaccid exam of the arm that begins to wear off in about 8 minutes. If it wears off faster (around 2 minutes) you may think about a high flow AVM.
- Assess language by asking pt to name objects and remember them
- Assess memory by asking pt to recall as many of the objects as possible 15 minutes later
- Procedure can be repeated on the other side if needed
Photo source: http://www.instantanatomy.net/headneck/vessels/articinskull.html
Source: Handbook of Neurosurgery, Greenberg 6th Ed
