Abstracts

Rationale: To describe the use of a subdural circular grid as compared to subdural electrode strips in detection of after-discharges during intraoperative electrical stimulation during functional brain mapping in patients with grade II-IV cerebral astrocytomas. Methods: Between 2016 and 2019 we performed a retrospective analysis of 65 consecutive patients undergoing awake craniotomy for resection of grade II-IV astrocytomas during functional brain mapping using direct electrocortical stimulation (DECS). Simultaneous intraoperative electrocorticography was performed and individualized. Visual interpretation of ECoG was performed by board-certified electroencephalographers.  Results: Sixty-five patients (mean age 49.0 years; r=18-78) underwent surgery for cerebral astrocytomas grades II-IV. MRI of the brains revealed a structural lesion in patients. For the patients, final pathology analysis revealed 12 had grade II-III astrocytomas and 20 had grade IV lesions (gliomas). Despite a lower mean number of stimulations (38.9 vs 47.9), after-discharges (ADs) were detected in 12/20 (60%) of patients in the circle grid compared to 5/12 (42%) of patients in subdural electrode strips. Electrographic ADs greater than ten seconds were detected in 11/20 of circle grid cases and 5/12 of subdural strip cases.  Conclusions: The Circle Grid is a new novel electrophysiological sensing device that was more effective at detecting ADs and electrographic seizures in patients undergoing grade II-IV astrocytoma resections. Applications of the Circular Grid to brain disorders, such as epilepsy and brain tumor-related epilepsy, may improve the intraoperative epileptogenic detection accuracy and functional outcomes while decreasing postoperative complications.  Funding: Dr. Tatum and Dr. Feyissa have received Mayo Clinic grants using high-density ECoG used in this study following data acquisition.