Abstracts

Rationale: In our previous study (Korostenskaja, 2013), we demonstrated the first application of paradigms used in functional magnetic resonance (fMRI) and electrical cortical stimulation mapping (ESM) studies for shared functional cortical mapping in the context of real-time functional mapping (RTFM). Results from all three functional modalities were qualitatively compared. We demonstrated the feasibility and usefulness of a new RTFM stimulation paradigm implementation during pre-surgical evaluation with block design paradigms used in fMRI. However, quantitative analysis of the three methods has not yet been performed. In this study, we performed quantitative comparison between the results of RTFM, ESM and fMRI mapping. The newly developed functional mapping system cortiQ (g.tec, Austria) was used to provide RTFM results.Methods: The study was approved by IRB of Florida Hospital. Three male patients with diagnosis of intractable epilepsy underwent RTFM testing following prolonged intracranial EEG monitoring to localize the ictal onset zone. The ECoG activity was recorded with g.USBamp, g.tec, Austria (sampling frequency 1200 Hz). The following tasks were administered: open/close the left hand, feel the touch to the palm and inner side of the fingers, and listen to a story. After an initial delay of 10 seconds, the paradigm started with a 15 second resting period in which the instruction for the patient presented on the display was relax followed by task for 15 sec. Each task was repeated three times. The brain signals were transferred to the computer running cortiQ (g.tec, Austria), and then analyzed in real-time. Activation was determined by comparing the power of the high-gamma frequency band (60-170 Hz) excluding power-line and its higher level harmonics. In order to find significant activation (p<0.001) on specific electrodes, a student s t-test was performed off-line over all channels. The sensitivity and specificity of RTFM were tested against ESM mapping and fMRI results.Results: When next-neighbor approach was used, the following sensitivity and specificity values were observed: (1) RTFM against ESM for hand motor 100% sensitivity and 95.93% specificity, for hand sensory 100% sensitivity and 93.30% specificity; (2) RTFM against fMRI for hand motor 100% sensitivity and 97.45% specificity, for hand sensory 66.70% sensitivity and 96.25% specificity, and for receptive language 75% sensitivity and 96.90% specificity.Conclusions: The results of the quantitative next-neighbor evaluation of cortiQ-based RTFM mapping were highly concordant to those determined by ESM and fMRI procedures. However, the cortiQ-based RTFM procedure itself was less time consuming and easier to perform than ESM and/or fMRI. Thus, the RTFM approach has the potential to be used as a guide to ESM to reduce the overall mapping time. Further validation of this method with larger patient cohort and long-term outcome is underway. References: Korostenskaja et al. EEG and Clinical Neuroscience (2013, Accepted for publication).