Uses
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.
The Wada test has several interesting side-effects. Drastic personality changes are rarely noted, but disinhibition is common. Also, contralateral hemiplegia, hemineglect and shivering are often seen. During one injection, typically the left hemisphere, the patient will have impaired speech and language or be completely unable to express or understand language. Although the patient may not be able to talk, sometimes their ability to sing is preserved. This is because music and singing utilizes a different part of the brain than speech and language. Recovery from the anesthesia is rapid, and EEG recordings and distal grip strength may be used to determine when the medication has worn off. Generally, recovery of speech is dysphasic (contains errors in speech or comprehension) after a language dominant hemisphere injection. Although generally considered a safe procedure, there are at least minimal risks associated with the angiography procedure used to guide the catheter to the internal carotid artery which may be related to experience. As such, efforts to utilize non-invasive means to determine language and memory laterality (e.g. fMRI, magnetoencephalography and near-infrared spectroscopy) are being researched.
Read more about this topic: Wada Test