High-frequency changes during interictal spikes detected by time-frequency analysis

Abstract

Objective-High-frequency (HF) changes were analysed in relation to anatomical origin of spikes, shape and occurrence within the seizure onset zone (SOZ). We evaluated whether HF changes are linked to the SOZ, as established for distinct high-frequency oscillations.Methods-SEEG was filtered at 500 Hz and sampled at 2000 Hz. Spikes were selected by shape (spike/spike-slow wave) and location (SOZ/non-SOZ and neocortex/amygdala/hippocampus) in 15 patients. About 50 spikes were averaged for each set. Changes compared to baseline were quantified with false discovery rate controlled t-statistics using time-frequency spectra. Counts of increased or decreased time-frequency values were compared across spike categories in the 80-250 and 250-500 Hz bands.Results-Seventy-seven spike types were analysed. Differences between spike categories were most prominent between 250 and 500 Hz. HF changes were more frequent and larger in mesial temporal than in neocortical spikes and for spikes with slow waves than spikes alone. HF changes above 250 Hz were more frequent in spikes within than outside the SOZ. Conclusions-HF increases above 250Hz show regional differences and are very prominent in the SOZ. Hippocampal spikes have the strongest HF components.Significance-Analysis of HF changes during spikes may provide information on differing pathophysiological mechanisms of spikes and on epileptogenicity of the tissue.

Electrocorticographic correlates of overt articulation of 44 English phonemes: Intracranial recording in children with focal epilepsy

“…The exclusion criteria consisted of (i) presence of structural lesion, seizure onset zone, or interictal spike discharges originating from the Rolandic area, inferior frontal gyrus or superior temporal gyrus; (ii) history of previous epilepsy surgery; (iii) history of hearing impairment; and (iv) evidence of language delays based on the standard neuropsychological assessment. Such strict criteria were employed in this study, partly because interictal spike discharges may contaminate measurement of the amplitude of gamma activity on ECoG (Jacobs et al, 2011; Zijlmans et al, 2011). Two right-handed native English speakers (Patient 1: 12 year old girl, and Patient 2: 9 year old girl) were studied.…”

Does interictal synchronization influence ictogenesis?

“…Interictal discharges are not associated with detectable clinical symptoms and are valuable both for diagnosing the epileptic condition and for localizing the epileptogenic area (Jacobs et al, 2010;de Curtis and Avanzini, 2001).…”

Suppression of acute seizures by theta burst electrical stimulation of the hippocampal commissure using a closed-loop system

“…High frequency neural activity decreased after spike-and-slow waves and even spikes (Jacobs et al, 2011;Kobayashi et al, 2009). This phenomenon is similar to a strong stimulus that could cause a synchronous activation of pyramidal cells and subsequently GABA release followed by GABA B receptor stimulation and after-hyperpolarization to suppress seizure activity (Toprani and Durand, 2013).…”