Non-invasive Electrophysiological Signatures of the Epileptogenic Zone Using Conventional Scalp EEG in Children with Focal Drug-Resistant Epilepsy
Abstract number :
3.177
Submission category :
3. Neurophysiology / 3G. Computational Analysis & Modeling of EEG
Year :
2021
Submission ID :
1825707
Source :
www.aesnet.org
Presentation date :
12/6/2021 12:00:00 PM
Published date :
Nov 22, 2021, 06:50 AM
Authors :
Georgios Ntolkeras, MD - Baystate Medical Center / Boston Children's Hospital; Assia Chericoni, MSc - University Campus Bio-Medico of Rome; Joseph Madsen, MD - Epilepsy Surgery Program, Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School, Boston, MA; P. Ellen Grant, MD - Director, Fetal-Neonatal Neuroimaging and Developmental Science Center, Newborn Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA; Phillip Pearl, MD - Director, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA; Christos Papadelis, PhD - Jane and John Justin Neurosciences Center, Cook Children's Health Care System, Fort Worth, TX; Eleonora Tamilia, PhD - Fetal-Neonatal Neuroimaging and Developmental Science Center, Newborn Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA
Rationale: Children with drug-resistant epilepsy (DRE) need neurosurgery for seizure control. To delineate the epileptogenic zone (the brain region indispensable for seizure generation), multiple presurgical evaluation techniques are used. Among those, the conventional scalp electroencephalography (EEG) is the most accessible and widely used across all epilepsy centers. Interictal EEG is traditionally reviewed seeking visually identifiable epilepsy biomarkers (i.e., spikes); however, sophisticated EEG analysis can provide additional information on the underlying epileptogenicity albeit not visibly identifiable by the human reader.
Recent studies suggest that epileptogenicity is a complex property of the brain depending on the interplay between high excitability and high connectivity. Thus, we propose a novel source imaging approach to optimize scalp EEG analysis, that is able to quantify both brain excitability (via phase-amplitude coupling, PAC) and functional connectivity using interictal data with or without epileptiform activity. The goal of this study is to identify novel non-invasive EEG measures that characterize the epileptogenic tissue in children with DRE and can potentially improve the presurgical localizing value of EEG.
Methods: We analyzed sleep scalp-EEG (19-24 channels) from children who had epilepsy surgery at Boston Children’s Hospital and were seizure-free (Engel1) after at least one year. We distinguished between EEG epochs with and without spikes (spike-epochs vs. silent-epochs, Figure 1A). We defined the epileptogenic tissue (EpiTissue) as the area resected during surgery, and non-epileptogenic tissue (Non-EpiTissue) as the homotopic region in the contralateral hemisphere (Figure 1B). Using electric source imaging (beamformer technique), we placed virtual sensors (20-mm apart) in the EpiTissue and non-EpiTissue and reconstructed their cortical activity, as shown in Figure 1C. We computed regional functional connectivity (rConn) within EpiTissue and non-EpiTissue (in delta, theta, alpha, beta, and gamma bands) as well as their PAC (between delta and gamma frequencies). PAC and connectivity values were compared between EpiTissue and non-EpiTissuefor silent-epochs and spike-epochs (Wilcoxon-sign-rank).
Results: Scalp EEG data of 19 children were analyzed. Our results showed increased beta rConn in the EpiTissue compared to non-EpiTissue in silent-epochs (p=0.01) and spike-epochs (p-value=0.007, Figure 2A&B), and increased gamma rConn in spike-epochs (p=0.009). In both EpiTissue and non-EpiTissue, rConn (p< 0.001, p=0.02, Figure 2B) and PAC (p< 0.001, p< 0.001) were higher, and showed more variability, during spike-epochs compared to silent-epochs. We also found increased PAC in the EpiTissue compared to non-EpiTissue in silent-epochs (p=0.014, Figure 2C).
Conclusions: Non-invasive measures of increased connectivity and PAC (estimated via scalp-EEG source imaging) help identify the epileptogenic tissue in children with focal DRE. The proposed approach could potentially provide the surgical team with an additional presurgical tool to assess resection or implantation strategies, which is non-invasive and independent of epileptiform discharges.
Funding: Please list any funding that was received in support of this abstract.: -
Neurophysiology