Abstracts

Rationale: In our previous case study, we demonstrated feasibility of applying paradigms used in functional magnetic resonance (fMRI) and electrical cortical stimulation mapping (ESM) for real-time functional mapping (RTFM) with electrocorticography (Korostenskaja, 2013). However, the results of the study were limited to one patient. In the current study, we expanded our patient population in order to overcome previous limitations and to perform an objective comparison between the results of RTFM, ESM and fMRI mappings.Methods: Twenty one patients, 10 male-11 female (ages 7-48 mean-18.47; SD- 10.61) with a diagnosis of intractable epilepsy underwent RTFM testing. The tasks administered were a variation among motor, sensory and language based activities (e.g., open-close hand, clapping, hand sensory, story listening, picture naming, verb generation, counting, reading comprehension, and reciting). Using g. USBamps, brain activity during the task performance in a real time was acquired, recorded and analyzed by BCI2000 software, using the SIGFRIED module (Schalk et al. 2004; Brunner et al. 2009). A topographic interface allowed the visualization of activity at different electrodes during task performance, which were represented by varying circle sizes. SIGFRIED results obtained in a real-time were used to compare against ESM and fMRI results.Results: Comparative analysis of the RTFM, ESM and fMRI data was done using the next-neighbor approach in order to calculate both sensitivity and specificity. Eleven subjects presented with both RTFM and ESM data and four with both RTFM and fMRI data. Preliminary data analysis demonstrated the following results: (1) RTFM against ESM for motor activity showed 72.5% sensitivity and 98.15% specificity; (2) RTFM against ESM for sensory activity showed 83% sensitivity and 97.51% specificity; (3) RTFM against ESM for receptive language tasks showed 65.76% sensitivity and 98.81% specificity; (4) RTFM against fMRI for receptive language tasks showed 85.71% sensitivity and 98.33% specificity. Conclusions: Our preliminary data analysis indicates that RTFM is a viable method for producing analogous results to those determined by golden standard of functional mapping ESM as well as fMRI. The RTFM specificity for all functional modalities is high. Sensitivity of RTFM procedure varies between different functional modalities. In this way, the highest sensitivity is obtained in sensory modality and the lowest - in language modality. Sensitivity of mapping motor function is intermediate. The results of the current study must be confirmed by using off-line analysis approaches. Future studies need to focus on increasing RTFM sensitivity for mapping of eloquent language cortex. Relation of RTFM mapping results to surgical outcomes must be evaluated.