Analysis of the dynamics and origin of epileptic activity in patients with tuberous sclerosis evaluated for surgery of epilepsy

Abstract

Objective: The epilepsies associated with the tuberous sclerosis complex (TSC) are very often refractory to medical therapy. Surgery for epilepsy is an effective alternative when the critical link between the localization of seizure onset in the scalp and a particular cortical tuber can be established. In this study we perform analysis of ictal and interictal EEG to improve such link. Methods: The ictal and interictal recordings of four patients with TSC undergoing surgery for epilepsy were submitted to independent component analysis (ICA), followed by source analysis, using the sLORETA algorithm. The localizations obtained for the ictal EEG and for the average interictal spikes were compared. Results: The ICA of ictal EEG produced consistent results in different events, and there was good agreement with the tubers that were successfully removed in three of the four patients (one patient refused surgery). In some patients there was a large discrepancy between the localization of ictal and interictal sources. The interictal activity produced more widespread source localizations. Conclusions: The use of ICA of ictal EEG followed by the use of source analysis methods in four cases of epilepsy and TSC was able to localize the epileptic generators very near the lesions successfully removed in surgery for epilepsy. Significance: The ICA of ictal EEG events may be a useful add-on to the tools used to establish the connection between epileptic scalp activity and the cortical tubers originating it, in patients with TSC considered for surgery of epilepsy.

Localization of the Epileptogenic Foci in Tuberous Sclerosis Complex: A Pediatric Case Report

“…Usually, data from several imaging modalities, such as electroencephalography (EEG), magnetoencephalography (MEG), diffusion tensor imaging (DTI), single-photon emission computed tomography (SPECT), and positron emission tomography (PET) must be integrated for an accurate presurgical localization. MEG (Kamimura et al, 2006; Xiao et al, 2006; Widjaja et al, 2010) or EEG data (Leal et al, 2008; Ochi et al, 2011; Kargiotis et al, 2013) are frequently reported in the literature. Very few reports present simultaneous MEG and EEG recordings (Iida et al, 2005; Sugiyama et al, 2009) in TSC-related pediatric epilepsy patients.…”

“…Few other studies report mixed pediatric and adult patient cohorts (Jansen et al, 2006; Wu et al, 2006; Canuet et al, 2008). For source analysis, previous investigations of epileptic foci in TSC patients used various methods for the identification of the epileptic active areas, such as synthetic aperture magnetometry (SAM) (Xiao et al, 2006; Sugiyama et al, 2009), equivalent current dipoles (ECDs) (Iida et al, 2005; Kamimura et al, 2006; Wu et al, 2006; Xiao et al, 2006; Leal et al, 2008; Sugiyama et al, 2009; Widjaja et al, 2010), or multiple signal classification (MUSIC) (Jansen et al, 2006). …”

Source Localization of Temporal Lobe Epilepsy Using PCA—LORETA Analysis on Ictal EEG Recordings

“…This study provides additional support for the contention that componential analysis and source localization methods can be used successfully for noninvasive source localization of ictal activity (Lagerlund et al, 2004;Leal et al, 2006Leal et al, , 2008. In the current study, the sample consisted of five patients who had focal temporal lobe epilepsy with a single epileptic focus as confirmed by a seizure-free history following surgery.…”

On bias and its reduction via standardization in discretized electromagnetic source localization problems

“…It means that each projection [LΓ 1/2 ] k to measurement space is equally many standard deviations away from the mean, which is zero. This is equivalent to Z-scores [39,41], where a set of Gaussian random variables from different scales are unified to ensure a fair comparison.…”