Focal and generalized EEG paroxysms in childhood absence epilepsy: Topographic associations and distinctive behaviors during the first cycle of non‐REM sleep

Abstract

SUMMARYPurpose: To better understand the nature of the focal spike-wave discharges (FSWDs) and focally led generalized spike-wave discharges (GSWDs) in typical childhood absence epilepsy (CAE) and by implication their nosologic and taxonomic significance. Methods: Twenty-four abnormal video-electroencephalography (EEG) studies from 13 consecutive children with CAE and good response to appropriate antiepileptic drugs (AEDs) were analyzed. We studied the association between the topography of absence onset and the ictal automatisms, and the topographic correlation between FSWDs and GSWDs and their respective behavior during hyperventilation and the different states of phasic and nonphasic non-rapid eye movement (NREM) sleep. GSWDs were considered as of ''focal'' onset if a lead-in could be visibly recognized at a paper speed of 60 mm/s, and were classified by their topography. Key Findings: (1) Multifocal absences occurred in 10 children; anterior onset was noted in 81 absences (73.6%) from 12 children and posterior in 18 (16.4%) from 7 children; there was no association between topography of absence onset and ictal automatisms; (2) FSWDs occurred in 85% of children and were multifocal in 73% of them; 85% of FSWDs were anterior and 14% posterior; (3) there was good topographic association between FSWDs and the leading spike of GSWDs of ''focal'' onset in all children with FSWDs; (4) both FSWDs and GSWDs increased during hyperventilation; (5) FSWDs occurred mainly during noncyclical NREM sleep and during periods of reduced vigilance of cyclical NREM sleep, whereas GSWDs occurred during the periods of enhanced vigilance of NREM sleep; GSWDs occurred significantly more frequently than FSWDs at the transition from reduced to enhanced vigilance of NREM sleep. Significance: Our findings suggest that in CAE focal EEG paroxysms reflect a system of multifocal nonlocalizing electrically unstable cortical areas that under the facilitatory influence of exogenous or endogenous factors like sleep instability can foster a corticothalamic response of sufficient strength to generate 3-Hz GSWDs that are conditionally sustainable and potentially ictal. FSWDs can be viewed as incomplete forms of the GSWDs; together they define the EEG identity of idiopathic ''generalized'' epileptogenesis.

Temporal current-source of spikes suggests initial treatment failure in childhood absence epilepsy

“…These observations demonstrate the involvement of the hippocampus and the interplay between the hippocampal and cortico-thalamocortical circuits in typical absence seizures [34,35]. Some clinical studies have also reported temporal lobe involvement in typical absence seizures [31,32]. Focal spike slow-wave discharges observed in the temporal lobe in CAE patients [31], which suggests that the temporal area may be a part of the epileptic network in CAE.…”

“…Some clinical studies have also reported temporal lobe involvement in typical absence seizures [31,32]. Focal spike slow-wave discharges observed in the temporal lobe in CAE patients [31], which suggests that the temporal area may be a part of the epileptic network in CAE. Focal temporal electroclinical transformation from typical absence seizures was observed in video-EEG monitoring of two CAE patients [32].…”

“…The cortical areas activated by absence seizures may vary according to individual susceptibility [11]. Recent evidence has demonstrated the involvement of the temporal lobe in typical absence seizures [17,[31][32][33][34]. An experimental study showed bilateral synchronization of the hippocampi during GSWDs in a pharmacologically induced animal model of typical absence seizures [34].…”

Primary Sleep Disorders in People with Epilepsy

“…100 Psychogenic nonepileptic events (pseudoseizures) may arise during periods when the patients seem to be sleeping but the EEG showed them awake (a condition called pseudosleep). [101][102][103] Injuries and incontinence do not distinguish between epilepsy and pseudoseizures. 104 Although longer-lasting, NFLE seizures can lead to episodic nocturnal wandering but more often are temporal lobe in origin.…”

Sleep Spindles – As a Biomarker of Brain Function and Plasticity

“…In a further study of childhood absence epilepsy [108] focal SWDs occurred mainly during non-CAP and CAP-B periods (periods of reduced vigilance) of NREM sleep, whereas generalized SWDs occurred during the CAP-A of NREM sleep and especially at the transition from reduced to enhanced vigilance of NREM sleep. Regarding the efforts to understand the relationship between spindles and epilepsy, these studies emphasize the importance of (a) mutual interaction between the two, (b) recognizing that different types of epilepsy may have different mechanisms and (c) the importance of observing the "bigger picture" in both time (i.e.…”