Abstracts

Rationale: To examine the cortical representation of category (common vs. proper nouns) and modality (auditory vs. visual) specific naming during extra-operative electrical stimulation mapping (ESM) in a series of patients undergoing temporal lobe epilepsy surgery. Our objective was to develop a protocol that is both more sensitive and specific to detecting essential language areas in the brain during cortical stimulation mapping. Methods: 8 consecutive patients (6 L-ATL, 2 R-ATL) underwent ESM for identification of eloquent cortex. Visual naming stimuli were line drawings of common nouns and pictures of Famous Faces/Landmarks (proper nouns). Auditory naming stimuli for both common and proper noun categories were taken from a normative study at our center. ESM parameters followed a standard protocol previously described. Results: Stimulation of numerous cortical areas produced dysnomia with one or more sensory modalities and semantic categories in all patients. Multiple double dissociations as well as several category specific sites were also identified for visual and auditory common/proper noun naming. The extended protocol identified approximately 3 to 7 unique category specific naming sites in each of these patients. In some cases, 90-100% overlap was observed between sites identified with the traditional naming protocol using only auditory and visual naming of common nouns and those identified by the current extended protocol. Conclusions: This case series has a number of important findings for ESM in epilepsy surgery. We found that the inclusion of multimodal and semantic category specific naming stimuli during ESM identifies more language cortex than any previously reported protocol. Also, the multiple double dissociations between modality and semantic category specific language abilities found indicates the importance of using stimuli with multiple semantic categories during mapping. Finally, in addition to identifying a number of unique language areas in the brain, ESM with visual proper noun naming stimuli showed significant site overlap with naming areas identified with traditional stimuli. In some cases, visual proper noun naming was the only stimuli necessary to identify all areas of essential naming cortex. These results demonstrate the utility of implementing a more semantically comprehensive and category specific protocol for identifying more areas of language during ESM in both L-ATL and R-ATL patients with language in the surgical hemisphere. The utility of this protocol for predicting postoperative naming outcome is a critical area of research that is ongoing in our lab.