Epilepsy syndromes of childhood with sleep activation: Insights from functional imaging

Continuous Spike-Waves during Slow Sleep Today: An Update

In the context of childhood epilepsy, the concept of continuous spike-waves during slow sleep (CSWS) includes several childhood-onset heterogeneous conditions that share electroencephalograms (EEGs) characterized by a high frequency of paroxysmal abnormalities during sleep, which have negative effects on the cognitive development and behavior of the child. These negative effects may have the characteristics of a clear regression or of a slowdown in development. Seizures are very often present, but not constantly. The above makes it clear why CSWS have been included in epileptic encephalopathies, in which, by definition, frequent EEG paroxysmal abnormalities have an unfavorable impact on cognitive functions, including socio-communicative skills, causing autistic features, even regardless of the presence of clinically overt seizures. Although several decades have passed since the original descriptions of the electroclinical condition of CSWS, there are still many areas that are little-known and deserve to be further studied, including the EEG diagnostic criteria, the most effective electrophysiological parameter for monitoring the role of the thalamus in CSWS pathogenesis, its long-term evolution, the nosographic location of Landau-Kleffner syndrome, standardized neuropsychological and behavioral assessments, and pharmacological and non-pharmacological therapies.

How the Spreading and Intensity of Interictal Epileptic Activity Are Associated with Visuo-Spatial Skills in Children with Self-Limited Focal Epilepsy with Centro-Temporal Spikes

This paper investigates brain-behaviour associations between interictal epileptic discharges and cognitive performance in a population of children with self-limited focal epilepsy with centro-temporal spikes (SeLECTS). Sixteen patients with SeLECTS underwent an extensive neuropsychological assessment, including verbal short-term and episodic memory, non-verbal short-term memory, attentional abilities and executive function. Two quantitative EEG indices were analysed, i.e., the Spike Wave Index (SWI) and the Spike Wave Frequency (SWF), and one qualitative EEG index, i.e., the EEG score, was used to evaluate the spreading of focal SW to other parts of the brain. We investigated associations between EEG indices and neuropsychological performance with non-parametric Spearman correlation analyses, including correction for multiple comparisons. The results showed a significant negative correlation between (i) the awake EEG score and the Block Tapping Test, a visuo-spatial short-term memory task, and (ii) the sleep SWI and the Tower of London, a visuo-spatial planning task (pcorr < 0.05). These findings suggest that, in addition to the usual quantitative EEG indices, the EEG analysis should include the qualitative EEG score evaluating the spreading of focal SW to other parts of the brain and that neuropsychological assessment should include visuo-spatial skills.

Encephalopathy related to status epilepticus during slow sleep (ESES). Pathophysiological insights and nosological considerations

Encephalopathy related to Status Epilepticus during slow Sleep (ESES) is a childhood epilepsy syndrome characterized by the appearance of cognitive, behavioral, and motor disturbances in conjunction with a striking activation of EEG epileptic abnormalities during non-REM sleep. After more than 50 years since the first description, the pathophysiological mechanisms underlying the appearance of encephalopathy in association with a sleep-related enhancement of epileptic discharges are incompletely elucidated. Recent experimental data support the hypothesis that the development of the ESES encephalopathic picture depends on a spike-induced impairment of the synaptic homeostasis processes occurring during normal sleep and that is particularly pronounced during the developmental age. During sleep, synaptic homeostasis is promoted by synaptic weakening/elimination after the increment of synaptic strength that occurs during wakefulness. The EEG can display modifications in synaptic strength by changes in sleep slow wave activity (SWA). Recent studies during active ESES have failed to show changes in sleep SWA, while these changes occurred again after recovery from ESES, thus supporting a spike-related interference on the normal homeostatic processes of sleep. This impairment, during the developmental period, can lead to disruption of cortical wiring and brain plastic remodeling, which lead to the, often irreversible, neuropsychological compromise typical of ESES. From the nosographic point of view, these pathophysiological data lend support to the maintenance of the term ESES, i.e., "encephalopathy related to status epilepticus during sleep". Indeed, this term conveys the concept that the extreme activation of epileptic discharges during sleep is directly responsible for the encephalopathy, hence the importance of defining this condition as an encephalopathy related to the exaggerated activation of epileptic activity during sleep. In this respect, ESES represents a genuine example of a "pure" epileptic encephalopathy in which sleep-related epileptic activity "per se" has a crucial role in determining the encephalopathic picture. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022.