Abstracts

Recent studies have reported a high rate of concordance between magnetoencephalography/magnetic source imaging (MSI) and the Intracarotid Amobarbital Procedure (IAP) in identifying patients with left hemisphere language dominance, despite the frequent co-occurrence of some right hemisphere activation on MSI. This study examines the anatomical activation patterns in the right hemisphere in response to an auditory word recognition task in patients who were classified with bilateral language based on the IAP. Data from four patients diagnosed with chronic epilepsy and/or brain tumor who had been classified with bilateral language representation on IAP and who also underwent language mapping with MSI were retrospectively reviewed. MSI data were obtained with a 148-channel Magnes 2500 WH system (4-D Neuroimaging, SanDiego, CA) and analyzed using the single equivalent dipole model. For each patient, the number and anatomic location of right hemisphere dipoles were examined in relation to modality-specific IAP language responses scored for the right hemisphere. Evidence of correct responses on automatic speech tasks and/or at least one correct naming response was present in all four patients during maximum drug effect following the left injection on IAP. Two of 4 patients demonstrated some auditory comprehension in the right hemisphere as well. Right hemisphere MSI language activation sites included the superior temporal gyrus and/or angular gyrus in 3 of 4 patients. The fourth patient showed activation in the right inferior frontal region and a portion of the insula. This patient had the highest right hemisphere language score on IAP of the 4 cases reviewed. For all patients, activation of classical temporal lobe language areas in the left hemisphere significantly exceeded that seen on the right. These data appear to confirm independent activation of specific right hemisphere language areas in patients with unambiguous language function in both hemispheres. Results will be considered in relation to MSI activation in exclusively left language dominant cases and other neuropsychological variables.