title: Ictal propagation of high frequency activity is recapitulated in interictal recordings: effective connectivity of epileptogenic networks recorded with intracranial EEG.
abstract: Seizures are increasingly understood to arise from epileptogenic networks across which ictal activity is propagated and sustained. In patients undergoing invasive monitoring for epilepsy surgery, high frequency oscillations have been observed within the seizure onset zone during both ictal and interictal intervals. We hypothesized that the patterns by which high frequency activity is propagated would help elucidate epileptogenic networks and thereby identify network nodes relevant for surgical planning. Intracranial EEG recordings were analyzed with a multivariate autoregressive modeling technique (short-time direct directed transfer function--SdDTF), based on the concept of Granger causality, to estimate the directionality and intensity of propagation of high frequency activity (70-175 Hz) during ictal and interictal recordings. These analyses revealed prominent divergence and convergence of high frequency activity propagation at sites identified by epileptologists as part of the ictal onset zone. In contrast, relatively little propagation of this activity was observed among the other analyzed sites. This pattern was observed in both subdural and depth electrode recordings of patients with focal ictal onset, but not in patients with a widely distributed ictal onset. In patients with focal ictal onsets, the patterns of propagation recorded during pre-ictal (up to 5 min immediately preceding ictal onset) and interictal (more than 24h before and after seizures) intervals were very similar to those recorded during seizures. The ability to characterize epileptogenic networks from interictal recordings could have important clinical implications for epilepsy surgery planning by reducing the need for prolonged invasive monitoring to record spontaneous seizures.
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Meyer 2-147, Baltimore, MD 21287, USA. Electronic address: akorzen@jhmi.edu.
authors.forename: A
authors.initials: A
authors.lastname: Korzeniewska
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Meyer 2-147, Baltimore, MD 21287, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Cervenka
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Meyer 2-147, Baltimore, MD 21287, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Jouny
authors.affiliation: Beckman Institute and Department of Physics, University of Illinois Urbana-Champaign, 405 N. Mathews Ave., Urbana, IL 61801, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Perilla
authors.affiliation: Department of Biostatistics, Richard M. Fairbanks School of Public Health and School of Medicine Indiana University, 410 W 10th St., Suite 3000, Indianapolis, IN 46202, USA.
authors.forename: J
authors.initials: J
authors.lastname: Harezlak
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Meyer 2-147, Baltimore, MD 21287, USA.
authors.forename: G K
authors.initials: GK
authors.lastname: Bergey
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Meyer 2-147, Baltimore, MD 21287, USA; Human Research and Engineering Directorate, US Army Research Laboratory, 459 Mulberry Point Rd, Aberdeen Proving Ground, MD 21005, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Franaszczuk
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Meyer 2-147, Baltimore, MD 21287, USA.
authors.forename: N E
authors.initials: NE
authors.lastname: Crone
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000503:physiopathology*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D004828:Epilepsies, Partial / Q000503:physiopathology; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D012640:Seizures / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
keywords: Brain mapping; ECoG; Epilepsy surgery; Epileptic network; High frequency oscillations (HFOs); Seizure onset zone