Stereoelectroencephalography-guided radiofrequency thermocoagulation (SEEG-guided RF-TC) aims to reduce seizure frequency by modifying epileptogenic networks through local thermocoagulative lesions. Although RF-TC is hypothesized to functionally modify brain networks, reports of changes in functional connectivity (FC) following the procedure are missing. We evaluated, by means of SEEG recordings, whether variation in brain activity after RF-TC is related to clinical outcome.
Interictal SEEG recordings from 33 DRE patients were analyzed. Therapeutic response was defined as more than 50% reduction in seizure frequency for at least one month following RF-TC. Local (power spectral density, PSD) and FC changes were evaluated in three-minute segments recorded shortly before (baseline), shortly after and 15 minutes after RF-TC. The PSD and FC strength values after thermocoagulation were compared with baseline as well as between the responder and non-responder groups.
In responders, we found a significant reduction in PSD after RF-TC in channels that were thermocoagulated (TC) for all frequency bands (p-value =0.007 for broad, delta and theta, p-value <0.001 for alpha and beta bands). However, we did not observe such PSD decrease in non-responders. At the network level, non-responders displayed a significant FC increase in all frequency bands except theta (broad, delta, beta band: p-value < 0.001; alpha band: p-value < 0.01), while responders showed a significant FC decrease in delta (p-value<0.001) and alpha bands (p-value0.05; delta: p= 0.001).
Thermocoagulation induces both local and network-related (FC) changes in electrical brain activity of patients with DRE lasting for at least 15 minutes. This study demonstrates that the observed short-term modifications in brain network and local activity significantly differ between responders and non-responders and opens new perspectives for studying the longer-lasting functional connectivity changes after RF-TC.

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