Abstracts

Rationale: Intraoperative monitoring of brain electrical activity using electrocorticography (ECoG) is often used as a means of verifying the resection margins of epileptic tissue (1). We combined the capability of the neuronavigation system to create landmarks to indicate ECoG electrode locations with structural and functional imaging during epilepsy resective surgeries. This combination allowed us to precisely localize electrode locations intraoperatively, and to assess resection margins with regard to ECoG data in postoperative MRI imaging. Methods: We retrospectively examined neuronavigation landmark data collected during resection surgeries that included intraoperative electrocorticography (ECoG), and the associated imaging performed as part of a standard epilepsy protocol for pediatric epilepsy patients. Inclusion criteria required that the patient had epilepsy surgery with ECoG electrode location landmarks collected intraoperatively, and imaging that included an epilepsy protocol MRI, a resting state and a tasked-based fMRI. Most subjects also had preoperative PET and postoperative MRI imaging. Data from each patient were processed according to modality. Functional MRI scans were post-processed using FSL. In BioImage Suite (2), PET and fMRI data were co-registered to the structural T1 MRI. Further, the ECoG electrode landmarks were transformed into image space and displayed on 3D renderings of the structural T1 MRI, and fMRI and PET data that was thresholded and overlaid on the structural T1 MRI. When available, postoperative MRI imaging was co-registered to the preoperative MRI such that the specific resection margins could be compared to the intraoperative ECoG data. Results: We reviewed a three year period (7/11 - 5/14), where data from 11 patients (6M/5F; range 0.7-16 yr) were evaluated using intraoperative ECoG landmarks and 3D volume renderings of imaging data. Of the 11 patients, 9 had preoperative PET scans, all had preoperative fMRI and 10 had postoperative MRI imaging. All patients had at least 2 ECoG locations identified, with a range of 2-13 ECoG locations recorded. These retrospective reviews of patient data were utilized by neurologists and surgeons to visualize intraoperative electrode locations with respect to resection margins and functional data. Conclusions: Co-registration of ECoG electrode locations to 3D volume renderings of imaging data allows the care team to reliably assess results from intraoperative and imaging studies in a comprehensive and intuitive fashion. Assessing the ECoG data following pathology investigations can provide insight into the electrophysiology associated with specific neuropathological disorders. This record of ECoG electrode locations can be valuable when used in conjunction with electrophysiological data with regard to a patient's clinical course and outcomes, and underlying pathology.