Abstracts

We used magnetoencephalography (MEG) to examine brain activation associated with receptive language in patients with left temporal lobe epilepsy (TLE) before and after an anterior temporal lobectomy. We evaluated which patients were most likely to show a change in the lateralization and localization of the mechanisms supporting receptive language and if such changes were associated with neuropsychological function. Fifteen patients with left TLE underwent pre-operative Wada testing, and pre- and post-operative neuropsychological testing and MEG language mapping. The anatomical location of receptive language-related activity sources observed with MEG was determined by co-registering MEG data with structural MRI scans. Language laterality indices were calculated based on the number of activity sources in each hemisphere. The location of language-specific activity was also examined in relation to its proximity to Wernicke[rsquo]s area. Patients with atypical (bilateral) language lateralization on the Wada test were significantly more likely than patients with left-hemisphere dominance to show a shift in language representation toward greater right hemispheric activity after surgery. Patients with left hemispheric dominance pre-operatively were more likely to show intrahemispheric changes involving a slight inferior shift of the putative location of Wernicke[rsquo]s area. Patients with bilateral representation tended to perform worse on neuropsychological test measures pre- and post-operatively. MEG can contribute significantly not only to the precise localization of Wernicke[apos]s area for presurgical planning, but is also an important tool for documenting post-operative language reorganization. (Supported by NINDS grant (NS 37941) to Andrew C. Papanicolaou and Austrian Science Fund (J2224-B02) to Ekaterina Pataraia.)