Language Lateralization in Temporal Lobe Epilepsy: A Comparison between fMRI and the Wada Test

Abstract

Summary:Purpose: Recent studies have claimed that language functional magnetic resonance imaging (f MRI) can identify language lateralization in patients with temporal lobe epilepsy (TLE) and that f MRI-based findings are highly concordant with the conventional assessment procedure of speech dominance, the intracarotid amobarbital test (IAT).Methods: To establish the power of language f MRI to detect language lateralization during presurgical assessment, we compared the findings of a semantic decision paradigm with the results of a standard IAT in 68 patients with chronic intractable right and left temporal lobe epilepsy (rTLE, n = 28; lTLE, n = 40) who consecutively underwent a presurgical evaluation program. The patient group also included 14 (20.6%) subjects with atypical (bilateral or right hemisphere) speech. Four raters used a visual analysis procedure to determine the laterality of speech-related activation individually for each patient.Results: Overall congruence between f MRI-based laterality and the laterality quotient of the IAT was 89.3% in rTLE and 72.5% in lTLE patients. Concordance was best in rTLE patients with left speech. In lTLE patients, language f MRI identified atypical, right hemisphere speech dominance in every case, but missed left hemisphere speech dominance in 17.2%. Frontal activations had higher concordance with the IAT than did activations in temporoparietal or combined regions of interest (ROIs). Because of methodologic problems, recognition of bilateral speech was difficult.Conclusions: These data provide evidence that language f MRI as used in the present study has limited correlation with the IAT, especially in patients with lTLE and with mixed speech dominance. Further refinements regarding the paradigms and analysis procedures will be needed to improve the contribution of language f MRI for presurgical assessment.

Working memory representation in atypical language dominance

“…In general, frontal regions show a higher correlation with Wada results than temporal areas [Benke et al, 2006;Lehéricy et al, 2000]. However, it has been suggested that left inferior frontal activation during semantic language paradigms may not be due to language processes in the narrow sense, but rather due to retrieval, selection and evaluation in the semantic executive system [Poldrack et al, 1999].…”

“…All LIs in the left dominant subjects were positive, and all LIs in the right dominant subjects were negative (see Supplementary Table I for an overview of all subjects). Moreover, to test whether mixed speech dominance was present [i.e., divergent lateralization within prefrontal, Broca's, and Wernicke's areas; Benke et al, 2006;Ries et al, 2004;Rutten et al, 2002], we calculated correlation coefficients between the LIs in the three regions both in the sample investigated in our study and in a more extended group of 132 healthy subjects. We found that for both groups, LIs were highly correlated (group of 32 subjects from the current study: Broca-Wernicke: Spearman's correlation coefficient R 5 0.682; P < 10…”

Localization of Broca's Area Using Functional MR Imaging: Quantitative Evaluation of Paradigms

“…Although this modality has been a gold standard for lateralizing language hemispheres, the major drawback of the Wada test is that it is invasive with inherent risks 1) . Many studies have shown that fMRI is at least comparable to the Wada test in terms of lateralizing language function 5,6,12,25) . Thus, fMRI appears to be a promising modality for the evaluation of language function, especially in terms of preoperative planning in order to preserve essential language areas.…”

“…Various modalities, such as the Wada test, fMRI, functional PET, and magnetoencephalography, can be used for non-invasive localization or lateralization of language area(s) for presurgical purposes. The Wada test and fMRI are the most popular of these modalities 5,6,12,24) . Although the Wada test can serve as a useful index of language laterality, it is less useful for localizing language areas.…”

“…Functional magnetic resonance imaging (fMRI) has been frequently used to localize language areas in the brain in a non-invasive manner [1][2][3][4][5][6][7][8]12,13,15,16,18,19,[24][25][26] . Various paradigms for the presurgical localization of language areas have been developed to replace invasive brain mapping.…”