Encephalopathy with Electrical Status Epilepticus in Slow Wave Sleep – a review with an emphasis on regional (perisylvian) aspects

Abstract

SUMMARYAim. The aim of this article is to review criticaly the Electrical Status Epilepticus in Slow Sleep (ESES) phenomenon from a neurophysiological mechanisms aspect as well as terminological and classification issues. Methods. The review includes all the relevant papers published during the last 43 years on the subject of ESES and Continous Spike -Wave in Sleep (CSWS).These papers were identified in various large databases via the internet. Rewiev and remarks. ESES/CSWS phenomena can be held as a common final pathway originating from different etiologies, including patients with early brain damage (probably involving thalamic structures), but also patients without structural pathology as in atypical evolution of idiopathic regional childhood hyperexcitability syndromes (with Rolandic epilepsy as a prototype). There are hints that genetic predisposition might be an important factor in the development of this process. The two large patient groups (lesional and non-lesional) show the same EEG evolution and encephalopathic cognitive consequences. The sleep EEG activation can be held as a common endophenotype. ESES represents an extreme sleep activation/potentiation of the local/ regional interictal discharges, enhancing them in frequency, territorial extension, intra and trans-hemispherial propagation, synchrony and continuity. This process is most probably not identical with the development of bilateral spike-wave pattern in "generalized" epilepsies which involves primarily or secondarily the thalamocortical system as it had been explored by Gloor (1979) for idiopathic generalized rpilepsy and Steriade and Amzica (2003) for different types of generalized spike and wave discharges. Conclusions and syndromological embedding of ESES.In an overwhelming majority of the investigated cases, the maps of the single discharges constituting sleep activation are identical; with focal/regional interictal spikes followed by slow closing wave, as it is seen in childhood regional age dependent hyperexcitability syndromes (prototype of the centro-temporal spikes of Rolandic epilepsy). The main mechanism of the developing cognitive impairment is most probably the consequence of interference with plastic function of slow wave sleep by obliterating synaptic decline during sleep. Presently, the consensus and co-operative research is highly obstacled by the terminological chaos, the controversial definitions and views around this still striking and enigmatic phenomenon.

Perisylvian epileptic network revisited

“…1% of cases. Looking into the increasing focus on these conditions in the literature [4,14,[48][49][50][51][52][53][54][55][56][57][58][59][60] and the estimations of involved professionals, it is likely that ESES/LKS is much more prevalent with an even higher heuristic significance.…”

“…A source of contradictions is the interpretation of the electrical patterns of ESES. ESES is considered a synchronous bilateral spike-wave pattern by several authors, but abundant data support the uni-hemispheric, focal/regional localization of discharges [4]. The newly described variants increase the terminological and taxonomic confusion (see in Appendix A).…”

“…As a further development of this story, it has turned out that ESES occurs in brain damaged children with variable aetiologies as well [16][17][18][19]. Several publications reported early thalamic lesions [20][21][22][23][24]3], but few were shown to be isolated [21,4] [25]. It is unclear how different aetiologies can cause the same abnormality.…”

Interictal epileptiform discharges in sleep and the role of the thalamus in Encephalopathy related to Status Epilepticus during slow Sleep

“…Indeed, BECTS, PS, atypical BECTS, LKS and ESES share a similar perisylvian location of IEDs, an important increase in IEDs during sleep, a deterioration of language and executive functions of various intensities as well as common genetic mutations (De Negri, 1997;Doose et al, 2001;Halász et al, 2005;Panayiotopoulos et al, 2008;Lemke et al, 2013;Lesca et al, 2013;Turner et al, 2015). Sleep-related IED activation in ESES is henceforth thought to represent an extreme exaggeration of what is seen in BECTS during sleep, both in space and synchronicity (De Negri, 1997;Halasz et al, 2014). Earlier EEG studies based on visual sleep stage scoring in patients with BECTS had identified slow wave sleep has a potent activator of IEDs (Beaumanoir et al, 1974;Dalla Bernardina et al, 1982;Clemens and Majoros, 1987), with the descending slope of the cycles having the greatest activating properties (Clemens and Majoros, 1987).…”

In response: Neuronal networks in epileptic encephalopathies with CSWS

“…Furthermore, due to the diversity of the epileptiform discharges, which are mainly focal/regional discharges or bilateral spike-waves, 2 he raises doubt about the existence of unitary mechanism of ESES and suggests that most of the discharges might reflect a more confined regional network. 3 A better understanding of the morphology and localization of the epileptiform discharges during ESES is an important issue. However, as noted by Dr. Hal asz, there are only few studies analyzing the potential fields of ESES discharges.…”