Abstracts

Rationale: Accurate language localization in children provides critical information for surgical planning, thereby expanding surgical epilepsy treatment options and allowing more aggressive resection of epileptogenic tissue while reducing the risk of post-surgical language deficit and benefiting children's quality of life. The objective of this research is to evaluate the electrocorticography (ECoG)-based real-time functional mapping (RTFM) technique (Schalk et al. 2008) for localizing language-specific regions in children. The central hypothesis of our proposed research is that that RTFM can be used as a tool for pre-surgical mapping of language function in pediatric patients. Methods: Seven patients with intractable epilepsy underwent RTFM testing since the inception of Epilepsy Program at Florida Hospital in August 2011. Here we present the data from representative subject #3 (13 yo right-handed female). Baseline ECoG activity was first recorded (g.USBamp, g.tec, Austria, sampling frequency 1200 Hz) for about 6 minutes followed by administration of paradigms, assessing receptive and expressive language function (Fig. 1). The sensitivity and specificity of RTFM were calculated only for sites where both RTFM and ESM were tested. RTFM sensitivity was calculated as the percentage of sites that were both RTFM(+) and ESM(+) among all ESM(+) sites, and RTFM specificity was calculated as the percentage of sites that were both RTFM(-) and ESM(-) among all ESM(-) sites. Results: RTFM demonstrated low sensitivity (25%) and high specificity (90%) when compared to ESM. RTFM showed several areas of activation related to expressive language function that were ESM negative. The patient underwent standard temporal lobectomy that included areas that were ESM negative but RTFM positive. The majority of the posterior superior temporal gyrus was left intact in order to avoid possible postsurgical expressive language deficits predicted by ESM mapping (Fig. 1). However, two month post-surgical neuropsychological testing showed expressive language decline. The patient demonstrated very low performance in visual confrontation naming when compared to same-aged peers. A mild decline was observed in phonemic fluency. A more noticeable decline in semantic fluency was found. Maternal report also suggested a decline in language functioning within the patient's everyday environment. It is possible to speculate that this resection based only on ESM results is associated with observed post-surgical expressive language deficits. The pediatric neurosurgeon indicated that if RTFM was a validated technique, he would use information provided by it to avoid post-surgical language decline. Conclusions: Preliminary results indicate that RTFM has the potential to make a substantial contribution to surgical planning. Post-operative language outcome showed acute decline in a patient whose surgery included areas that were ESM negative but RTFM positive. Further validation of this method is underway. References: Schalk G et al. (2008) Real-time detection of event-related brain activity. NeuroImage 43: 245-9