Differentiation of Tumor vs. Peritumoral Cortex in Gliomas by Intraoperative Electrocorticography.

Brain diffuse gliomas are highly epileptic and infiltrative tumors. Glioma surgery consists in the resection of the tumor core and the maximum of the peritumoral zone, infiltrated by tumor cells, guided by the intraoperative assessment of brain functionality and connectivity. However, its electrophysiological characteristics are poorly characterized. We studied the characteristics of Electrocorticographic (ECoG) signals, in the context of glioma surgery in awake condition on 29 patients, using EEG activity sampled on the tumor itself versus on its borders and in healthy areas. We assessed the features of frequency bands and aperiodic components (offset and slope) of ECoG power spectra during awake glioma surgery, according to cortical tumoral vs peritumoral and healthy status. We found that tumor contacts present a decrease in activity for all the frequency bands except for delta activity, which was increased. Second, the peritumoral cortex was characterized by an increase in relative beta activity and slopes between 20-40 Hz. Low cortical tumor cell infiltration was directly correlated with a reduction in the production of physiological brain rhythms. Finally, an automatic classifier based on neural networks allowed the classification of the electrodes based on their power spectrum characteristics. This intraoperative study shows that ECoG during glioma surgery in awake condition may characterize the peritumoral cortices, key for pathophysiology and therapy, and deepens our knowledge of the effects of tumor cells infiltration on nervous tissue activity. Its assessment during the surgical procedure should better delineation of the cortical areas to be removed.