Functional Network Alterations as Markers for Predicting the Treatment Outcome of Cathodal Transcranial Direct Current Stimulation in Focal Epilepsy

Abstract

Background and PurposeTranscranial direct current stimulation (tDCS) is an emerging non-invasive neuromodulation technique for focal epilepsy. Because epilepsy is a disease affecting the brain network, our study was aimed to evaluate and predict the treatment outcome of cathodal tDCS (ctDCS) by analyzing the ctDCS-induced functional network alterations.MethodsEither the active 5-day, −1.0 mA, 20-min ctDCS or sham ctDCS targeting at the most active interictal epileptiform discharge regions was applied to 27 subjects suffering from focal epilepsy. The functional networks before and after ctDCS were compared employing graph theoretical analysis based on the functional magnetic resonance imaging (fMRI) data. A support vector machine (SVM) prediction model was built to predict the treatment outcome of ctDCS using the graph theoretical measures as markers.ResultsOur results revealed that the mean clustering coefficient and the global efficiency decreased significantly, as well as the characteristic path length and the mean shortest path length at the stimulation sites in the fMRI functional networks increased significantly after ctDCS only for the patients with response to the active ctDCS (at least 20% reduction rate of seizure frequency). Our prediction model achieved the mean prediction accuracy of 68.3% (mean sensitivity: 70.0%; mean specificity: 67.5%) after the nested cross validation. The mean area under the receiver operating curve was 0.75, which showed good prediction performance.ConclusionThe study demonstrated that the response to ctDCS was related to the topological alterations in the functional networks of epilepsy patients detected by fMRI. The graph theoretical measures were promising for clinical prediction of ctDCS treatment outcome.

Stereo-EEG based personalized multichannel transcranial direct current stimulation in drug-resistant epilepsy

“…Conversely, for the latest, we observed a tendency to an increase of Fc at the end of the study. In line with these findings, a recent study has used Fc with fMRI as a quantitative measure of tDCS effects on brain activity in patients with epilepsy (Hao et al, 2021). This study showed that the response to the cathodal tDCS was linked to functional network alterations with a decreasing Fc in patients responding to the active cathodal tDCS.…”

Transcranial current stimulation in epilepsy: A systematic review of the fundamental and clinical aspects

“…They considered that tDCS induced a cumulative clinical benefit with reduction in SF in epileptic patients, associated with a decrease in synchronization. A more recent study aimed to evaluate and predict the potential clinical efficacy of cathodal tDCS by analyzing the induced functional network alterations (Hao et al, 2021 ). The 27 epileptic patients were separated in two groups of stimulation: sham group and active cathodal tDCS group with 20-min stimulation at −1 mA, for 5 consecutive days, targeting the regions with higher IEDs rate.…”

“…Recent studies focusing on functional brain network changes have highlighted interesting results between the response to tDCS therapy and functional disturbances in global brain networks (Lin et al, 2018 ; Tecchio et al, 2018 ; Daoud et al, 2022 ). Measuring FC changes may thus be a possible predictor of the tES clinical efficacy in epileptic patients (Hao et al, 2021 ). However, measuring changes in functional connectivity after tDCS in epilepsy has some limitations.…”