A Comparison of Electrode Recordings in Electrocorticography During Functional Brain Mapping in Awake Craniotomy: More Is Better

Introduction: Awake craniotomy with functional brain mapping (FBM) and bedside neurological testing is crucial for optimizing awake craniotomy. FBM is often performed concomitantly with electrocorticography (ECoG) and direct electrical stimulation (DES). The ECoG electrode design is under-appreciated in its importance in enhancing ECoG. In this study we compare sensitivity and utility of novel circular grid, standard strip, and high-density (HD) grid electrodes in performing FBM.

Methods: This retrospective study, approved by the institutional review board at Mayo Clinic Florida, analyzed patients who underwent FBM during awake craniotomy for lesionectomy. We compared data obtained from different electrodes including a novel 22-contact circular grid, 6-contact strip, and HD grid (>22 contacts). Demographic and clinical data were collected, including details related to ECoG. data.

Results: A total of 170 patients were included, with 199 surgical cases analyzed. There were no significant differences in baseline demographic or clinical data among the groups. Circular grid and HD grid electrodes were similar in their sensitivity in capturing spontaneous ictal (11/86, 12.7% vs. 1/25, 4.0%, p=0.29) and interictal activity (35/86, 40.7% vs 9/25, 36.0%, p=0.672). There was a greater detection of spontaneous interictal activity using the circular grid (p < 0.001) or HD grid (p < 0.05) when compared to the strip electrode (13/88, 14.7%). More surgeries were also performed using stimulation during FBM with the circular grid (59/86, p< 0.001) and strip (41/88, p< 0.001) electrodes when compared to the HD grid (2/25, 8.0%).

Conclusion : This study demonstrates higher sensitivity in detecting spontaneous interictal activity on ECoG when using electrodes with a greater number of contacts with improved spatial resolution. Further, electrode design is crucial in determining the electrode used for performing FBM, with surgeon preference demonstrated for a circular grid and strip electrode over HD grid electrode.