Brain network characteristics of favorable outcomes following radiofrequency thermocoagulation for drug-resistant epilepsy in periventricular nodular heterotopia patients

This study investigated the brain network characteristics that are associated with favorable outcomes following radiofrequency thermocoagulation (RF-TC) treatment in patients with drug-resistant epilepsy related to periventricular nodular heterotopia (PNH). The goal of the study was to elucidate the potential alterations exhibited by the epileptic networks of PNH patients and provide insights for optimizing surgical strategies. Seven PNH patients were enrolled. Stereoelectroencephalography data collected from four patients were analyzed. The channels were categorized as thermocoagulated (TC; n = 107) or non-thermocoagulated (non-TC; n = 368). Two 200-second epochs were selected for analysis purposes: one preceding RF-TC and one commencing 15 min after RF-TC. The power spectral density (PSD) and functional connectivity (FC) changes were compared between these epochs. To mitigate the potential volume conduction effects amplified by post-RF-TC lesions, the phase lag index (PLI) was employed alongside mutual information (MI) for the FC analysis, providing a more robust assessment of network changes. At the 12-month follow-up point, all seven patients achieved Engel class I outcomes. After RF-TC, the PSD decreased significantly across all frequency bands in both TC channels (p < 0.01 for all bands) and only θ band (p < 0.001) in non-TC channels with a more pronounced reduction observed in the TC channels. An MI-based FC analysis revealed increased FC across almost all bands in the TC channels after RF-TC (δ band: p = 0.542; other bands: p < 0.01). Conversely, the non-TC channels exhibited decreased FC in all bands except δ and ripple bands. A PLI-based analysis revealed a significant differences between TC and non-TC channels in the β (p = 0.001) and low-ripple band (p = 0.011) for the post-TC period. Nodules and/or the overlying cortex exhibiting epileptic network connectivity may function as a seizure generation unit, potentially facilitated and augmented by other networks. PLI-detected β and ripple band changes may constitute the key phase-synchronous pathway through which RF-TC modulates brain networks. Clinical trial number: not applicable.