Background: Functional MRI (fMRI) is of potential value in determining hemisphere dominance for language in epileptic patients.
Objective: To develop and validate an fMRI-based method of determining language dominance for patients with a wide range of potentially operable brain lesions in addition to epilepsy.
Methods: Initially, a within-subjects design was used with 19 healthy volunteers (11 strongly right-handed, 8 left-handed) to determine the relative lateralizing usefulness of three different language tasks in fMRI. An automated, hemispheric analysis of laterality was used to analyze whole brain fMRI data sets. To evaluate the clinical usefulness of this method, we compared fMRI-determined laterality with laterality determined by Wada testing or electrocortical stimulation mapping, or both, in 23 consecutive patients undergoing presurgical evaluation of language dominance.
Results: Only the verb generation task was reliably lateralizing. fMRI, using the verb generation task and an automated hemispheric analysis method, was concordant with invasive measures in 22 of 23 patients (12 Wada, 11 cortical stimulation). For the single patient who was discordant, in whom a tumor involved one-third of the left hemisphere, fMRI became concordant when the tumor and its reflection in the right hemisphere were excluded from laterality analysis. No significant negative correlation was obtained between lesion size and strength of laterality for the patients with lesions involving the dominant hemisphere.
Conclusion: This fMRI method shows potential for evaluating language dominance in patients with a variety of brain lesions.