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Preictal surrender of post–spike slow waves to spike‐related high‐frequency oscillations (80–200 Hz) is associated with seizure initiation
Author(s) -
Sato Yosuke,
Doesburg Sam M.,
Wong Simeon M.,
Boelman Cyrus,
Ochi Ayako,
Otsubo Hiroshi
Publication year - 2014
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/epi.12728
Subject(s) - ictal , spike (software development) , spike and wave , electroencephalography , epilepsy , medicine , neuroscience , physics , psychology , computer science , software engineering
Summary Objective Spike and slow waves consist of a “spike” including high‐frequency oscillations ( HFO s), which are linked to epileptogenicity and a “post–spike slow wave ( PSS )” related to inhibitory activity. The aim of this study was to elucidate the spatiotemporal relationship between spike‐related HFO s and PSS in patients with focal cortical dysplasia ( FCD ) type II . Methods We studied 10 pediatric patients with FCD type II , who underwent extraoperative video–electroencephalography ( EEG) . We selected spike and slow waves, which included HFO s (80–200 Hz), and performed spike peak–locked averaging 10 times during both 30 s interictal (>1 h apart from seizures) and 30 s preictal periods. We calculated the power of spike‐related HFO s and PSS during both periods for the following three areas: (1) inside the seizure‐onset zone ( SOZ ), (2) inside the resection area ( RA ) but outside SOZ ( RA ‐ SOZ ), and (3) outside the RA . Between the interictal and preictal periods we performed correlation (Spearman's coefficient) and simple linear regression analyses comparing HFO and PSS power within each area. Results A total of 1,614 averaged spike and slow waves were analyzed during both periods. During the interictal periods, there were significant positive correlations between HFO and PSS power in all areas (inside SOZ , r = 0.568; RA ‐ SOZ , r = 0.700; outside RA , r = 0.320). During the preictal periods, the correlation became weaker inside SOZ (r = 0.149) and remained unchanged both inside the RA ‐ SOZ (r = 0.704) and outside RA (r = 0.346). From the interictal to preictal period, the slope (Δ PSS power/Δ HFO power) of the simple regression line decreased inside SOZ (0.349 to 0.051) but increased in RA ‐ SOZ (0.534 to 0.734) and outside RA (0.267 to 0.435). Significance Relative power reduction of PSS to spike‐related HFO s in SOZ is relevant for seizure initiation. Our analysis will contribute to future studies of seizure prediction and distinction between pathologic and physiologic HFO s. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here .