Changes in local and network brain activity after stereotactic thermocoagulation in patients with drug‐resistant epilepsy

Abstract

Objective: 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. Methods:Interictal SEEG recordings from 33 patients with drug-resistant epilepsy (DRE) were analyzed. Therapeutic response was defined as a >50% reduction in seizure frequency for at least 1 month following RF-TC. Local (power spectral density [PSD]) and FC changes were evaluated in 3-min segments recorded shortly before (baseline), shortly after, and 15 min after RF-TC. The PSD and FC strength values after thermocoagulation were compared with baseline as well as between the responder and nonresponder groups. Results:In responders, we found a significant reduction in PSD after RF-TC in channels that were thermocoagulated for all frequency bands (p = .007 for broad, delta and theta, p <.001 for alpha and beta bands). However, we did not observe such PSD decrease in nonresponders. At the network level, nonresponders displayed a significant FC increase in all frequency bands except theta (broad, delta, beta band: p <.001; alpha band: p <.01), although responders showed a significant FC decrease in delta (p <.001) and alpha bands (p <.05). Nonresponders showed stronger FC changes with respect to responders exclusively in TC channels (broad, alpha, theta, beta: p >.05; delta: p = .001).Significance: Thermocoagulation induces both local and network-related (FC) changes in electrical brain activity of patients with DRE lasting for at least 15 min.

Stereoelectroencephalography-Guided Radiofrequency Thermocoagulation: Diagnostic and Therapeutic Implications

“…Changes in interictal epileptiform abnormalities as well as seizure onset and propagation patterns after SgRFTC may give insights into epileptic network organization. Simula et al [59] found acute changes in brain network and local activity after SgRFTC, and these changes differed among patients with significant seizure reduction versus those without. Xu et al [60] have proposed that abolishment of high frequency oscillations by SgRFTC may be a key to success.…”

The Temporal Lobe Club: Newer Approaches to Treat Temporal Lobe Epilepsy

“… 33 - 35 Importantly, it has been demonstrated that there is a reduction of functional connectivity in responders to thermocoagulation. 36 Furthermore, there is by now robust evidence that decrease in functional connectivity correlates with therapeutic response to different modes of neuromodulation (VNS, DBS, transcranial direct current stimulation (tDCS)). 37 - 39 …”

Disrupting the epileptogenic network with stereoelectroencephalography‐guided radiofrequency thermocoagulation

“…Some studies have highlighted the relevance of local tissue destruction in the seizure-onset zone (SOZ), 4,5 and others have focused on the epileptogenic network. [6][7][8] However, the relationship between the location of the ablation within the epileptogenic network and clinical outcomes has not been carefully explored.…”