High-frequency neuronal network modulations encoded in scalp EEG precede the onset of focal seizures

Abstract

Modulations of neuronal network interactions by seizure precursors are only partially understood and difficult to measure, in part due to inherent intra- and inter-patient seizure heterogeneity and EEG variability. This study investigated preictal neuromodulations associated with seizures originating in the temporal and/or frontal lobes, using information theoretic parameters estimated from awake scalp EEGs in two frequency ranges, ≤100 Hz and >100 Hz, respectively. Seizure-related activity at high frequencies has not been extensively estimated in awake scalp EEGs. Based on the statistical similarity of preictal and ictal information parameters, preictal network interactions appeared to be specifically modulated at frequencies >100 Hz, but not at lower frequencies. The dynamics of these parameters varied distinctly according to the origin of seizure onset (temporal versus frontal). Although preliminary, and based on a small patient sample for which the potential heterogeneity of multiple anticonvulsive medications was difficult to control, these results suggest that preictal modulations may be estimated from high-frequency scalp EEGs using directional information measures with high specificity to ictal events, and may thus be promising for improving seizure prediction.

EEG seizure detection and prediction algorithms: a survey

“…To solve this problem, Stamoulis et al studied the pre-ictal neuro-modulations corresponding to temporal and/or frontal lobe seizures. They used information theoretic features like entropy and mutual information extracted from two frequency ranges (the range that is less than or equal to 100 Hz and the range that is greater than 100 Hz) of awake scalp EEGs [29]. They succeeded to measure pre-ictal modulations at frequencies greater than 100 Hz with high specificity.…”

On the proper selection of preictal period for seizure prediction

“…Therefore, we investigated high-quality iEEG and sEEG recordings (with the sampling rates of 1024 Hz and 2500 Hz) and divided the gamma band into several narrower subbands to study the spectral behavior more precisely. Instead of using the well-known frequency bands, the subbands were selected as (0.5-4], (4)(5)(6)(7)(8), (8)(9)(10)(11)(12)(13)(14)(15), (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48) The spectral powers were obtained using power spectral density (PSD) estimated through Welch's method [47]. The PSD ...…”

Information theoretic measures of network coordination in high-frequency scalp EEG reveal dynamic patterns associated with seizure termination

“…In contrast, no measurable HFOs in the immediate postictal period have been detected [43]. Recent studies have also reported seizure-related and spasm-related high-frequency waveforms and aberrant network synchrony in scalp EEG [2, 44, 12, 15, 13, 31]. However, for this activity to be measurable at the scalp, it probably originates from areas of the brain beyond the epileptogenic region, and may represent a more spatially distributed phenomenon.…”

“…Recent studies of seizure-related scalp EEGs at frequencies >100 Hz suggest that neural activity, in the form of oscillations and/or neuronal network interactions, may play an important role in preictal/ictal seizure evolution [2, 31]. However, the role of high-frequency activity in seizure termination, is unknown, if it exists at all.…”