Interictal EEG spikes identify the region of electrographic seizure onset in some, but not all, pediatric epilepsy patients

Abstract

SUMMARYPurpose: The role of sharps and spikes, interictal epileptiform discharges (IEDs), in guiding epilepsy surgery in children remains controversial, particularly with intracranial electroencephalography (IEEG). Although ictal recording is the mainstay of localizing epileptic networks for surgical resection, current practice dictates removing regions generating frequent IEDs if they are near the ictal onset zone. Indeed, past studies suggest an inconsistent relationship between IED and seizure-onset location, although these studies were based upon relatively short EEG epochs. Methods: We employ a previously validated, computerized spike detector to measure and localize IED activity over prolonged, representative segments of IEEG recorded from 19 children with intractable, mostly extratemporal lobe epilepsy. Approximately 8 h of IEEG, randomly selected 30-min segments of continuous interictal IEEG per patient, were analyzed over all intracranial electrode contacts. Results: When spike frequency was averaged over the 16-time segments, electrodes with the highest mean spike frequency were found to be within the seizure-onset region in 11 of 19 patients. There was significant variability between individual 30-min segments in these patients, indicating that large statistical samples of interictal activity were required for improved localization. Low-voltage fast EEG at seizure onset was the only clinical factor predicting IED localization to the seizure-onset region. Conclusions: Our data suggest that automated IED detection over multiple representative samples of IEEG may be of utility in planning epilepsy surgery for children with intractable epilepsy. Further research is required to better determine which patients may benefit from this technique a priori.

Electric source imaging of interictal activity accurately localises the seizure onset zone

“…However, because this zone cannot be defined unambiguously before surgery, the IZ and SOZ must be used as surrogates in clinical practice. Of these, the SOZ is often considered to be the better one,23 but the vast majority of non-invasive localising techniques are based on interictal activity, as seizures can generally only be recorded serendipitously or with long-term recordings and are frequently accompanied by motion artefacts. Our finding that the IZ colocalised with the SOZ in most cases is in line with previous research and affects ESI and magnetic source imaging (MSI) or EEG-fMRI 16 24 25.…”

Generation of a Mouse Model of Atypical Teratoid/Rhabdoid Tumor of the Central Nervous System through Combined Deletion of Snf5 and p53

“…Mice carrying the Cre alleles were used as controls. The methods for implantation and recording have been previously published (28,29) and details are presented in Supplemental data. EEG tracings were visually reviewed for the presence of electrographic seizures.…”

The role of the interictal EEG in selecting candidates for resective epilepsy surgery

“…If the epileptogenic region is either too small (b6 cm 3 ), too deep (depth of sulcus), or located in an "invisible" region such as orbitofrontal cortex or the interhemispheric fissure, discharges may not be seen on the surface EEG. In addition, the Epilepsy & Behavior 20 (2011) 167-171 presence of IEDs on a particular EEG varies depending on the duration of the recording [13]. A single EEG may be completely normal in a person with epilepsy, increasing the yield to 92% by the fourth routine study [14].…”

“…Any information that can provide strong evidence for localization of the seizure onset zone, especially if it is noninvasively obtained, is critical. Research efforts devoted to other properties of interictal waveforms such as phase coherence [82], local hypersynchrony [83], automated quantification of spike discharges [13,16], computer-assisted spike voltage topography, and dipole modeling [84][85][86] are underway and hold promise. In addition, techniques that link interictal EEG activity with neuroimaging have been promising [87].…”