NIMG-99. REAL-TIME DELINEATION OF THE CENTRAL SULCUS WITH THE SPATIAL PROFILE OF SSEPS CAPTURED WITH HIGH-DENSITY ECOG GRID

Abstract

Abstract OBJECTIVE Cortical mapping during tumor resection is critical to reducing the risk of neurological complications. While the somatosensory evoked potential (SSEPs) is widely employed to delineate the central sulcus, the evoked response can be misconstrued from the manual peak interpretation. This is due to the poor spatial resolution of the strip electrode as well as a result of edema or tumor infiltration of the overlying cortex. We present a real-time computer-based visualization system that uses recorded SSEPs with a subdural grid to aid in cortical mapping. Method: The neural data during electrical stimulation of the median nerve at 0.6Hz are picked up with a bio-amplifier. The stimulation artifact recorded from the bipolar electromyogram (EMG) is used as the stimulation onset. The ECoG data are assessed online with MATLAB Simulink to process and visualize the SSEPs waveform. The visualization system is programmed to display the SSEP's peak activation as a heat map on a 2D grid and projected onto a screen, showcasing the nature of the cortical activities over the contact surface area in real-time. RESULTS SSEPs were recorded from 3 patients during their awake craniotomies. The ECoG grid occupied a large cortical surface where the heatmap delineated the central sulcus. The color-coding of the heatmap revealed the anterior and posterior channels, providing a consistently high separation accuracy in each patient (accuracy = 98%). The map could be viewed at any time point along the SSEP trace without peak interpretation. CONCLUSION We believe that this visualization system will aid in the rapid definition of the sensorimotor area during surgical planning to provide additional information during cortical mapping and facilitate interpreting ECoG grid data.