Language lateralization in temporal lobe epilepsy: a comparison between fMRI and the Wada Test

Area of Science:

• Neuroimaging
• Epilepsy Research
• Clinical Neurology

Background:

• Presurgical evaluation for epilepsy aims to localize critical brain functions.
• Language lateralization is crucial for surgical planning in temporal lobe epilepsy (TLE).
• The intracarotid amobarbital test (IAT) is the conventional method for assessing speech dominance.

Purpose of the Study:

• To evaluate the diagnostic power of language functional magnetic resonance imaging (fMRI) for detecting language lateralization.
• To compare fMRI findings with the standard IAT in patients with intractable TLE.
• To assess the concordance between fMRI and IAT in identifying speech dominance.

Main Methods:

• A semantic decision fMRI paradigm was used in 68 patients with chronic intractable TLE (28 right, 40 left).
• fMRI results were compared with standard IAT findings for speech dominance.
• Four raters analyzed speech-related fMRI activations to determine laterality.

Main Results:

• Overall congruence between fMRI and IAT was 89.3% in right TLE and 72.5% in left TLE (lTLE).
• fMRI accurately identified right hemisphere speech in lTLE but missed left hemisphere dominance in 17.2%.
• Frontal lobe activations showed higher concordance with IAT than temporoparietal regions.

Conclusions:

• Language fMRI, as applied, demonstrates limited correlation with the IAT, especially in lTLE patients.
• fMRI's effectiveness is constrained in cases of mixed or atypical speech dominance.
• Further research is needed to refine fMRI paradigms and analysis for improved presurgical assessment.