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Joshi RB, Duckrow RB, Goncharova II, Gerrard JL, Spencer DD, Hirsch LJ, Godwin DW, Zaveri HP. Seizure susceptibility and infraslow modulatory activity in the intracranial electroencephalogram. Epilepsia 2018; 59:2075-2085. [PMID: 30187919 DOI: 10.1111/epi.14559] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 08/12/2018] [Accepted: 08/13/2018] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Studies of infraslow amplitude modulations (<0.15 Hz) of band power time series suggest that these envelope correlations may form a basis for distant spatial coupling in the brain. In this study, we sought to determine how infraslow relationships are affected by antiepileptic drug (AED) taper, time of day, and seizure. METHODS We studied intracranial electroencephalographic (icEEG) data collected from 13 medically refractory adult epilepsy patients who underwent monitoring at Yale-New Haven Hospital. We estimated the magnitude-squared coherence (MSC) at <0.15 Hz of traditional EEG frequency band power time series for all electrode contact pairs to quantify infraslow envelope correlations between them. We studied, first, hour-long background icEEG epochs before and after AED taper to understand the effect of taper. Second, we analyzed the entire record for each patient to study the effect of time of day. Finally, for each patient, we reviewed the clinical record to find all seizures that were at least 6 hours removed from other seizures and analyzed infraslow envelope MSC before and after them. RESULTS Infraslow envelope MSC increased slightly, but significantly, after AED taper, and increased on average during the night and decreased during the day. It was also increased significantly in all frequency bands up to 3 hours preseizure and 1 hour postseizure as compared to background icEEG (61 seizures studied). These changes occurred for both daytime and nighttime seizures (28 daytime, 33 nighttime). Interestingly, there was significant spatial variability to these changes, with the seizure onset area peaking at 3 hours preseizure, then showing progressive desynchronization from 3 hours preseizure to 1 hour postseizure. SIGNIFICANCE Infraslow envelope analysis may be used to understand long-term changes over the course of icEEG monitoring, provide unique insight into interictal electrophysiological changes related to ictogenesis, and contribute to the development of novel seizure forecasting algorithms.
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Affiliation(s)
- Rasesh B Joshi
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine, Winston-Salem, North Carolina.,Computational Neurophysiology Laboratory, Comprehensive Epilepsy Center, Department of Neurology, Yale University, New Haven, Connecticut
| | - Robert B Duckrow
- Computational Neurophysiology Laboratory, Comprehensive Epilepsy Center, Department of Neurology, Yale University, New Haven, Connecticut.,Comprehensive Epilepsy Center, Department of Neurology, Yale University, New Haven, Connecticut
| | - Irina I Goncharova
- Computational Neurophysiology Laboratory, Comprehensive Epilepsy Center, Department of Neurology, Yale University, New Haven, Connecticut.,Comprehensive Epilepsy Center, Department of Neurology, Yale University, New Haven, Connecticut
| | - Jason L Gerrard
- Comprehensive Epilepsy Center, Department of Neurosurgery, Yale University, New Haven, Connecticut
| | - Dennis D Spencer
- Comprehensive Epilepsy Center, Department of Neurosurgery, Yale University, New Haven, Connecticut
| | - Lawrence J Hirsch
- Comprehensive Epilepsy Center, Department of Neurology, Yale University, New Haven, Connecticut
| | - Dwayne W Godwin
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Hitten P Zaveri
- Computational Neurophysiology Laboratory, Comprehensive Epilepsy Center, Department of Neurology, Yale University, New Haven, Connecticut.,Comprehensive Epilepsy Center, Department of Neurology, Yale University, New Haven, Connecticut
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