Personalized multichannel transcranial direct current electrical stimulation guided by SEEG in epilepsy: Clinical and neurophysiological effects

International audienc

Personalized multichannel transcranial direct current electrical stimulation guided by SEEG in epilepsy: Clinical and neurophysiological effects

International audienc

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

International audienceOBJECTIVE: In epilepsy, multichannel transcranial direct electrical stimulation (tDCS) is applied to decrease cortical activity through the delivery of weak currents using several scalp electrodes. We investigated the long-term effects of personalized, multisession, stereotactic-EEG (SEEG)-targeted multichannel tDCS on seizure frequency (SF) and functional connectivity (Fc) as measured by EEG in patients with drug-resistant epilepsy (DRE). METHODS: Ten patients suffering from DRE were recruited. Multichannel tDCS (Starstim, Neuroelectrics) was applied during three cycles (one cycle every 2 months) of stimulation. Each cycle consisted of five consecutive days where patients received tDCS daily in two 20 min sessions separated by 20 min. The montages were personalized to target epileptogenic area of each patient as defined by SEEG recordings. SF during and after treatment was compared with baseline. Fc changes were analysed using scalp EEG recordings. RESULTS: After the last tDCS session, five patients experienced a SF decrease of 50% or more compared with baseline (R: responders, average SF decrease of 74%). We estimated Fc changes between cycles and across R and non-responder (NR) patients. R presented a significant decrease in Fc (p < 0.05) at the third session in alpha and beta frequency bands compared to the first one. CONCLUSIONS: Multichannel tDCS guided by SEEG is a promising therapeutic approach. Significant response was associated with a decrease of Fc after three stimulation cycles. SIGNIFICANCE: Such results suggest that tDCS-induced functional plasticity changes that may underlie the clinical response

Effect of Vagus Nerve Stimulation on Electroencephalogram Synchronization: A Longitudinal Study Using a Clinical-Research Response Scale

Objectives: No reliable biomarkers exist for predicting and assessing the Vagus Nerve Stimulation (VNS) response. While VNS induces acute electroencephalogram (EEG) desynchronization post-implantation, longitudinal evaluations of EEG synchronization changes are lacking. This study constitutes the first prospective investigation evaluating EEG synchronization before and after VNS implantation and correlating it with the clinical response to VNS. Materials and Methods: High-density EEG recordings were obtained from 12 adults with drug-resistant epilepsy before and after VNS implantation (1, 3, and 6 months). EEG resting state (180s), with eyes open (EO) and closed (EC), was recorded in VNS ON and OFF conditions. The global weighted Phase Lag Index (wPLI) was computed as an EEG phase-synchronization measure and correlated with the VNS response using various assessment methods: binary (more or less than 50% seizure frequency reduction), percentage of seizure reduction, and a newly developed Clinical-Research Response Scale (CRRS). Results: We observed a progressive decrease of wPLI in the delta band for the EC- VNS OFF condition, which correlated with the VNS response over time, particularly using the new CRRS compared to other assessment methods. Additionally, a higher pre-implant global wPLI predicted a better outcome to VNS, as did an early magnet response. Conclusion: Overall, VNS may positively influence specific brain states, with a time-dependent evolution of EEG synchronization reflecting therapeutic efficacy. Pre-implantation synchronization of the EEG and an early magnet response may predict VNS response. Moreover, the CRRS could constitute a more sensitive method for characterizing VNS response compared to traditional assessment methods

Automated Electrical Source Imaging with scalp EEG to define the insular irritative zone: comparison with simultaneous intracranial EEG

Objective To evaluate the accuracy of automated interictal low-density electrical source imaging (LD-ESI) to define the insular irritative zone (IZ) by comparing the concomitant interictal ESI localization with the SEEG interictal activity. Methods Long-term concomitant scalp electroencephalography (EEG) and stereo-EEG (SEEG) with at least one depth electrode exploring the operculo-insular region(s) were analyzed. Automated interictal ESI was performed on the scalp EEG using standardized low-resolution brain electromagnetic tomography and individual head models. A two-step analysis was performed: i) sublobar concordance between cluster-based ESI localization and SEEG-based IZ; ii) time-locked ESI-/SEEG analysis. Diagnostic accuracy values were calculated using SEEG as reference standard. Subgroup analysis was carried out, based on the involvement of insular contacts in the seizure onset and patterns of insular interictal activity. Results Thirty patients were included in the study. ESI showed an overall accuracy of 53% (C.I. 29-76%). Sensitivity and specificity were calculated as 53% (C.I. 29-76%), 55% (C.I. 23-83%) respectively. Higher accuracy was found in patients with frequent and dominant interictal insular spikes. Conclusions LD-ESI defines with good accuracy the insular implication in the IZ, which is not possible with classical interictal scalp EEG interpretation. Significance Automated LD-ESI may be a valuable additional tool to characterize the epileptogenic zone in epilepsies with suspected insular involvement