Language lateralization by fMRIand Wada testing in 229 patients with epilepsy: Rates and predictors of discordance

Abstract

Summary Purpose To more definitively characterize Wada/fMRI language dominance discordance rates with the largest sample of epilepsy patients to date, and to examine demographic, clinical, and methodological predictors of discordance. Methods 229 epilepsy patients underwent both a standardized Wada test and a semantic-decision fMRI language protocol in a prospective research study. Language laterality indices were computed for each test using automated and double-blind methods, and Wada/fMRI discordance rates were calculated using objective criteria for discordance. Regression analyses were used to explore a range of variables that might predict discordance, including subject variables, Wada quality indices, and fMRI quality indices. Key findings Discordant results were observed in 14% of patients. Discordance was highest among those categorized by either test as having bilateral language. In a multivariate model, the only factor that predicted discordance was the degree of atypical language dominance on fMRI. Significance FMRI language lateralization is generally concordant with Wada testing. The degree of rightward shift of language dominance on fMRI testing is strongly correlated with Wada/fMRI discordance, suggesting that fMRI may be more sensitive than Wada to right hemisphere language processing, though the clinical significance of this increased sensitivity is unknown. The relative accuracy of fMRI vs. Wada testing for predicting post-surgical language outcome in discordant cases remains a topic for future research.

Presurgical language fMRI: Technical practices in epilepsy surgical planning

“…Conversely, it is also frequently seen as opposing standardization, objectivity, and the research method. Note, however, that the best validation studies to date do actually use a highly standardized approach (Bonelli et al, 2012; Janecek et al, 2013; Szaflarski et al, 2017). As in a more comprehensive survey of clinicians' experience of clinical language fMRI (Benjamin et al, 2018), analysts frequently (46%) report that language laterality judged by fMRI has disagreed with that yielded by other methods in at least some instances.…”

“…It is our view that recommending a single paradigm for clinical use is not yet possible; head to head comparison of the existing protocols that have to date been validated for a range of purposes, in a range of populations, remains a priority. Note that teams can obtain and become familiar with many of the best‐studied protocols free of charge by emailing the relevant authors (Bonelli et al, 2012; Janecek et al, 2013). Versions of key tasks are also freely available at cogneuro.net/omfmri.…”

“…Language functional magnetic resonance imaging (fMRI) is an imaging method and neurocognitive assessment validated for predicting language decline after temporal lobe surgery (Bonelli et al, 2012; Sabsevitz et al, 2003). The demonstration of its equivalence or superiority to the Wada test (Intracarotid Amobarbital Testing; IAT) with certain protocols (Janecek et al, 2013), and its noninvasive nature, has led to its widespread adoption in neurosurgical planning. In spite of its ubiquitous use, the lack of comprehensive guidelines on precisely how clinical language fMRI should be executed with respect to cognitive design, imaging, procedure, operator training, and interpretation, has led to marked variation in all aspects of the method.…”

“…For example, software packages often implement different solutions in key analysis steps, and fMRI validation studies have used a range of packages such as AFNI (Sabsevitz et al, 2003), SPM (Bonelli et al, 2012), and custom software (Benjamin et al, 2017). Each step in data preprocessing alters the output; and the literature validating fMRI preprocessing may or may not include explicit realignment of echo‐planar imaging (EPI) data, or involvement of explicit smoothing of 2 mm, 10 mm, or an unspecified amount (Benjamin et al, 2017; Bonelli et al, 2012; Janecek et al, 2013). The approach to identification of task‐related signal also varies, with both general linear modeling and correlation coefficients in use.…”

Contemporary model of language organization: an overview for neurosurgeons

“…7 One particular task, the semantic decision/tone decision contrast developed by Binder and colleagues (2008), is predictive of postoperative verbal memory deficits and is highly concordant with Wada language testing in left hemisphere dominant individuals. 7,53 Furthermore, inclusion of fMRI in preoperative assessments has been shown to alter neurosurgical decision making 87 and is useful in determining the regions of interest that are used during white matter tractography.…”