title: Source localization of ictal epileptic activity based on high-density scalp EEG data.
abstract: Electrical source imaging (ESI) is a well-established approach to localizing the epileptic focus in drug-resistant focal epilepsy. So far, ESI has been used primarily on interictal events. Emerging evidence suggests that ictal ESI is also feasible and potentially useful. We aimed to investigate the diagnostic accuracy of ESI on ictal events using high-density electroencephalography (EEG).
  
  
  
  We performed ictal ESI on 14 patients (9 with temporal lobe epilepsy) admitted for presurgical evaluation who presented seizures during a long-term (≥18 h) high-density EEG recording (13 with 256 electrodes and one with 128 electrodes), and subsequently 8 of them underwent epilepsy surgery (postoperative follow-up >1 year). Artifact-free EEG epochs at ictal οnset were selected for further analysis. The predominant ictal rhythm was identified and filtered (±1 Hz around the main frequency). ESI was computed for each time point using an individual head model and a distributed linear inverse solution, and the average across source localizations was localized. For validation, results were compared with the resection area and postoperative outcome.
  
  
  
  Ictal ESI correctly localized the epileptic seizure-onset zone in the resection area in five of six postoperatively seizure-free patients. Interictal and ictal ESI were concordant in 9 of 14 patients and partially concordant in additional 4 of 14 patients (93%). Divergent solutions were found in only one of the 14 patients (7%).
  
  
  
  Ictal ESI is a promising localization technique in focal epilepsy.
authors.affiliation: Laboratory of Clinical Neurophysiology, AHEPA Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Petros
authors.identifier: 0000-0001-5204-8856
authors.initials: P
authors.lastname: Nemtsas
authors.affiliation: Department of Fundamental Neurosciences, Functional Brain Mapping Lab, University of Geneva, Geneva, Switzerland.
authors.forename: Gwenael
authors.initials: G
authors.lastname: Birot
authors.affiliation: EEG & Epilepsy Unit, Department of Clinical Neurosciences, University Hospital of Geneva, Geneva, Switzerland.
authors.forename: Francesca
authors.initials: F
authors.lastname: Pittau
authors.affiliation: Department of Fundamental Neurosciences, Functional Brain Mapping Lab, University of Geneva, Geneva, Switzerland.|Center for Biomedical Imaging (CIBM) Lausanne, Geneva, Switzerland.
authors.forename: Christoph M
authors.initials: CM
authors.lastname: Michel
authors.affiliation: Department of Clinical Neurosciences, Neurosurgery Clinic, University Hospital of Geneva, Geneva, Switzerland.
authors.forename: Karl
authors.initials: K
authors.lastname: Schaller
authors.affiliation: EEG & Epilepsy Unit, Department of Clinical Neurosciences, University Hospital of Geneva, Geneva, Switzerland.
authors.forename: Serge
authors.initials: S
authors.lastname: Vulliemoz
authors.affiliation: Laboratory of Clinical Neurophysiology, AHEPA Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Vasilios K
authors.initials: VK
authors.lastname: Kimiskidis
authors.affiliation: EEG & Epilepsy Unit, Department of Clinical Neurosciences, University Hospital of Geneva, Geneva, Switzerland.
authors.forename: Margitta
authors.initials: M
authors.lastname: Seeck
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D002648:Child; D000069279:Drug Resistant Epilepsy / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D004569:Electroencephalography / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography / Q000379:methods; D011300:Preoperative Care; D012815:Signal Processing, Computer-Assisted; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult
keywords: Drug-resistant epilepsy; Electrical source imaging; Epilepsy surgery; High-density interictal electroencephalography; Ictal electrical source imaging