Differentiation of tumor versus peritumoral cortex in gliomas by intraoperative electrocorticography

Background

Brain diffuse gliomas are highly epileptic and infiltrative tumors. Glioma surgery consists of 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.

Methods

We studied the characteristics of electrocorticographic (ECoG) signals, in the context of glioma surgery in awake conditions 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 versus peritumoral and healthy status.

Results

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 and 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.

Conclusions

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 cell infiltration on nervous tissue activity. Its assessment during the surgical procedure should better delineation of the cortical areas to be removed.