fMRI wada test: Prospects for presurgical mapping of language and memory

Abstract

Since the inception of functional magnetic resonance imaging (fMRI) in the early 1990s, clinicians and researchers have been interested in the potential utility of this technology for replacement of the intracarotid amobarbital test (IAT or Wada test). The IAT is an invasive angiographic procedure that has traditionally been considered the conventional procedure for preoperative lateralization of language and memory in neurosurgical populations with lesions affecting brain regions critical for these functions. As fMRI is a repeatable, noninvasive procedure with no significant known health risks for most individuals, it would be advantageous to create validated paradigms to allow its use in place of the IAT. To date, the available literature strongly suggests that fMRI paradigms can be successfully used to replace the IAT in terms of language lateralization. While the status of appropriately reliable and valid memory assessment paradigms is not as advanced, significant progress has been made in this area as well. Despite the apparent advantages of fMRI in presurgical assessment, including more specific localization of task-related brain regions, which is not possible with IAT, there remain methodological challenges and issues of interpretation that have thus far prevented widespread use of fMRI in place of the IAT. This chapter discusses the background of the IAT and its risks and benefits compared to fMRI and reviews the body of literature examining the capacity of fMRI to lateralize and localize expressive and receptive language functions effectively, as well as more recent advances in utilizing fMRI findings to predict postsurgical outcome.