Abstract
The sodium amytal test, or Wada test, named after Juhn Wada, has remained a pillar of presurgical planning and is used to identify the laterality of the dominant language and memory areas in the brain. What is perhaps less well known is that the original intent of the test was to abort seizure activity from an affected hemisphere and also to protect that hemisphere from the effects of electroconvulsive treatment. Some 80 years after Paul Broca described the frontal operculum as an essential area of expressive language and well before the age of MRI, Wada used the test to determine language dominance. The test was later adopted to study hemispheric memory dominance but was met with less consistent success because of the vascular anatomy of the mesial temporal structures. With the advent of functional MRI, the use of the Wada test has narrowed to application in select patients. The concept of selectively inhibiting part of the brain to determine its function, however, remains crucial to understanding brain function. In this review, the authors discuss the rise and fall of the Wada test, an important historical example of the innovation of clinicians in neuroscience.
Highlights
The sodium amytal test, or Wada test, named after Juhn Wada, has remained a pillar of presurgical planning and is used to identify the laterality of the dominant language and memory areas in the brain
Paul Broca (Fig. 1) published the earliest anatomical evidence that language function localized to the left frontal lobe in the posterior part of the third convolution (Fig. 2), known as “Broca’s area.”[3,7] Broca arrived at his theory based on clinical examinations and subsequent cortical damage found on autopsy
Understanding the cortical localization of language and memory in patients has remained a challenge for neuroscientists
Summary
Understanding the cortical localization of language and memory in patients has remained a challenge for neuroscientists. As Juhn Wada himself commented regarding its use in evaluating patients for MTL surgery, “while we await the arrival of validated safe alternative(s), judicious and innovative use of the carotid amytal deactivation by a skilled hand, when justified, can continue to help patients and create new information and hypotheses on the mechanism of function and dysfunction of the human brain in the behavioral state.”[30] continued improvement in agents and techniques to aid in determining language dominance and memory localization will provide help to those with epilepsy but potentially contribute significantly to our understanding of neuroanatomy and functional neuroscience
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