Does sleep benefit memory consolidation in children with focal epilepsy?

Memory Consolidation and Sleep in Children With Epilepsy: A Systematic Review

BACKGROUND

Sleep is essential in the process of memory consolidation. Children and adolescents with epilepsy hold a significantly higher risk for memory impairment. Understanding the relationship between sleep and memory impairment in adolescents with epilepsy will help us to develop effective support services for this patient population. The present study provides a summary of the current research on the influence of epilepsy-related altered sleep patterns on memory consolidation in children and adolescents with epilepsy. The aim of this systematic review is to investigate the influence of epilepsy-related altered sleep conditions in children and adolescents and their impact on memory performance.

MATERIALS

A systematic review was conducted according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses using the search terms "memory," "sleep," "epilepsy," "children," and "adolescents." A total of 4 studies met the inclusion criteria. The review focused on the association of sleep disorders and memory performance in children and adolescents aged up to 21 years without psychiatric comorbidities.

RESULTS

The reviewed studies highlight a higher risk of sleep disturbance and lower sleep quality in children with epilepsy in comparison to control groups. Group differences in memory consolidation were found before, but not after one night of sleep. Three studies reported a significant association between sleep and memory performance. Two studies demonstrated an association between nocturnal interictal epileptiform discharges and memory performance in adolescents.

CONCLUSION

Children and adolescents with epilepsy have a higher risk of sleep and memory disorders. Nocturnal interictal epileptiform discharges have been shown to interfere with memory consolidation. Conclusions on underlying mechanisms remain unclear. Further case-control studies addressing sleep and its influence on memory problems in pediatric epilepsy patients are needed.

Sleep and functional outcomes in children and adolescents with epilepsy: A scoping review

AIM

In children and adolescents with epilepsy (CAWE), disturbed sleep and functional difficulties are frequently present, but their relationship is unclear. In this scoping review we aimed to explore associations between sleep and functional outcomes in CAWE.

METHOD

We registered the protocol with open science framework and conducted the review according to the PRISMA Extension for Scoping Reviews. We searched Medline, Embase, PsycINFO and PubMed for original studies reporting on relations between sleep and functional outcomes (adaptive/quality of life, behavioural/mood, cognitive & academic) in CAWE. To assess the quality of studies we used an extended version of the checklist employed by Winsor and colleagues [1].

RESULTS

We identified 14 studies that included 1,785 CAWE and 1,260 control children, with a mean age of 9.94 and 10.13 years, respectively. The studies were highly heterogeneous with respect to samples, epilepsy variables, and methods used to assess sleep and functional outcomes. The quality of studies was medium. Associations between sleep and adaptive/quality of life, behavioural/mood, cognitive and academic outcomes were examined in 2, 10, 6, and 0 studies, respectively. Across studies, in CAWE, greater sleep disturbances were related to worse behavioural/mood outcomes, ranging from depression/anxiety to ADHD symptoms. Sleep disturbances did not consistently relate to cognitive outcomes, but they related to worse adaptive outcomes in both studies that examined their relationship.

CONCLUSIONS

Our study provides evidence of relationship between disturbed sleep and behavioural/mood difficulties, which alerts to the need for careful evaluation and treatment of sleep disturbances in CAWE. Our study also highlights the need to examine relationships between sleep and other functional outcomes in CAWE, as studies conducted in the general population suggest that sleep disturbances may be modifiable and associated with improved functional outcomes.

Long-term memory consolidation of new words in children with self-limited epilepsy with centro-temporal spikes

Accelerated long-term forgetting has been studied and demonstrated in adults with epilepsy. In contrast, the question of long-term consolidation (delays > 1 day) in children with epilepsy shows conflicting results. However, childhood is a period of life in which the encoding and long-term storage of new words is essential for the development of knowledge and learning. The aim of this study was therefore to investigate long-term memory consolidation skills in children with self-limited epilepsy with centro-temporal spikes (SeLECTS), using a paradigm exploring new words encoding skills and their long-term consolidation over one-week delay. As lexical knowledge, working memory skills and executive/attentional skills has been shown to contribute to long-term memory/new word learning, we added standardized measures of oral language and executive/attentional functions to explore the involvement of these cognitive skills in new word encoding and consolidation. The results showed that children with SeLECTS needed more repetitions to encode new words, struggled to encode the phonological forms of words, and when they finally reached the level of the typically developing children, they retained what they had learned, but didn't show improved recall skills after a one-week delay, unlike the control participants. Lexical knowledge, verbal working memory skills and phonological skills contributed to encoding and/or recall abilities, and interference sensitivity appeared to be associated with the number of phonological errors during the pseudoword encoding phase. These results are consistent with the functional model linking working memory, phonology and vocabulary in a fronto-temporo-parietal network. As SeLECTS involves perisylvian dysfunction, the associations between impaired sequence storage (phonological working memory), phonological representation storage and new word learning are not surprising. This dual impairment in both encoding and long-term consolidation may result in large learning gap between children with and without epilepsy. Whether these results indicate differences in the sleep-induced benefits required for long-term consolidation or differences in the benefits of retrieval practice between the epilepsy group and healthy children remains open. As lexical development is associated with academic achievement and comprehension, the impact of such deficits in learning new words is certainly detrimental.

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.

Focal epilepsy impacts rapid eye movement sleep microstructure

STUDY OBJECTIVES

Whereas there is plenty of evidence on the influence of epileptic activity on non-rapid eye movement (NREM) sleep macro- and micro-structure, data on the impact of epilepsy on rapid eye movement (REM) sleep remains sparse. Using high-density electroencephalography (HD-EEG), we assessed global and focal disturbances of sawtooth waves (STW) as cortically generated sleep oscillations of REM sleep in patients with focal epilepsy.

METHODS

Twenty-two patients with drug-resistant focal epilepsy (13 females; mean age, 32.6 ± 10.7 years; 12 temporal lobe epilepsy) and 12 healthy controls (3 females; 24.0 ± 3.2 years) underwent combined overnight HD-EEG and polysomnography. STW rate, duration, frequency, power, spatial extent, IED rates and sleep homeostatic properties were analyzed.

RESULTS

STW rate and duration were reduced in patients with focal epilepsy compared to healthy controls (rate: 0.64/min ± 0.46 vs. 1.12/min ± 0.41, p = .005, d = -0.98; duration: 3.60 s ± 0.76 vs. 4.57 ± 1.00, p = .003, d = -1.01). Not surprisingly given the fronto-central maximum of STW, the reductions were driven by extratemporal lobe epilepsy patients (rate: 0.45/min ± 0.31 vs. 1.12/min ± 0.41, p = .0004, d = -1.35; duration: 3.49 s ± 0.92 vs. 4.57 ± 1.00, p = .017, d = -0.99) and were more pronounced in the first vs. the last sleep cycle (rate first cycle patients vs. controls: 0.60/min ± 0.49 vs. 1.10/min ± 0.55, p = .016, d = -0.90, rate last cycle patients vs. controls: 0.67/min ± 0.51 vs. 0.99/min ± 0.49, p = .11, d = -0.62; duration first cycle patients vs. controls: 3.60s ± 0.76 vs. 4.57 ± 1.00, p = .003, d = -1.01, duration last cycle patients vs. controls: 3.66s ± 0.84 vs. 4.51 ± 1.26, p = .039, d = -0.80). There was no regional decrease of STWs in the region with the epileptic focus vs. the contralateral side (all p > .05).

CONCLUSION

Patients with focal epilepsy and in particular extratemporal lobe epilepsy show a global reduction of STW activity in REM sleep. This may suggest that epilepsy impacts cortically generated sleep oscillations even in REM sleep when epileptic activity is low.

Perceived impact of epilepsy on sleep: Views of children with epilepsy, parents and school staff

OBJECTIVE

To gain an understanding of the views of school-aged children with epilepsy, their parents, and school staff regarding the impact of epilepsy on sleep.

METHODS

As part of the What I Need in School (WINS) study, school-aged children (n = 18) with 'active epilepsy' (taking Anti-Seizure Medications, ASMs, for epilepsy), their parents (n = 68) and school staff (n = 56) were interviewed or completed bespoke questionnaires. Questions focussed on the potential impact of epilepsy on the child's sleep or tiredness in school and the potential impact of sleep/tiredness on learning and behavior.

RESULTS

Fifty-six percent of children believed that epilepsy affects their sleep while 65% of parents believed that their child had more difficulties with sleep than other children of their age. Seventy-eight percent of parents believed that their child's difficulties were due to epilepsy and 95% believed that their child's difficulties impacted their learning and behavior. Fifty-four percent of school staff believed that the child with epilepsy they supported was more tired/fatigued than their peers, and 86% of school staff believed that the child's increased tiredness affected their learning/behavior. Parents of children with intellectual disabilitiy were significantly more likely to indicate that they felt that their child had more sleep difficulties than other children (p = 0.016). Regarding the impact on their sleep, participating children felt that epilepsy contributed to difficulties in falling and staying asleep and daytime tiredness. Their parents reported a range of potential sleep difficulties and potential impacts on the child's learning and behavior. Parental reported difficulties included daytime tiredness, difficulty falling and staying asleep, and the impact of nocturnal seizures. In terms of impact, parents felt that sleep difficulties impacted negatively cognition and emotional-behavioral functioning. Additionally, parents reported that ASMs and medication for ADHD can contribute to sleep difficulties. School staff felt that many of the children appeared tired/fatigued during the day and this could lead to less engagement with classroom activities, impact attention and processing speed negatively, and contribute to behavioral and emotional difficulties.

CONCLUSION

The majority of children and parents who responded believed that epilepsy affects the child's sleep. Most parents and school staff also believed that the child's sleep difficulties/excess tiredness were due to the child's epilepsy and that the difficulties significantly impacted the child's learning and behavior. There is a need to better understand the role epilepsy plays in sleep difficulties and associated learning and behavioral impairments. There is also a need to develop interventions to reduce the subsequent impact on child learning and behavior.

Does epileptic activity impair sleep-related memory consolidation in epilepsy? A critical and systematic review

STUDY OBJECTIVES

People with epilepsy often complain about disturbed sleep and cognitive impairment. Beyond seizures, the occurrence of interictal epileptic activity during sleep is also increasingly recognized to negatively impact cognitive functioning, including memory processes. The aim of this study was to critically review the effect of interictal epileptic activity on sleep-related memory consolidation.

METHODS

PubMed and PsychINFO databases were systematically searched to identify experimental studies that investigated sleep-related memory consolidation and the relationships between sleep-related epileptic activity and memory in adults and children with epilepsy. This review also highlights hypotheses regarding the potential pathophysiological mechanisms.

RESULTS

A total of 261 studies were identified; 27 of these met selection criteria. Only 13 studies prospectively assessed the effect of sleep on memory in epilepsy. Most studies reported no alteration of sleep-related memory consolidation in patients, with either similar retention levels following a period containing sleep (n = 5) or improved memory performance postsleep (n = 4). Two studies in children with epilepsy found impaired sleep-related memory consolidation. Ten studies, of which 6 were in childhood epilepsy syndromes, reported a debilitating effect of sleep-related epileptic activity on memory functioning.

CONCLUSIONS

Conclusions from existing studies were hampered by small sample sizes, heterogeneous patient groups, and variations in memory assessment techniques. Overall, results to date preclude any definitive conclusions on the alteration of sleep-related memory consolidation in epilepsy. We discuss methodological considerations specific to people with epilepsy and provide suggestions on how to best investigate the relationship between epileptic activity, sleep, and memory consolidation in future studies.

CITATION

Latreille V, Schiller K, Peter-Derex L, Frauscher B. Does epilepticimpair sleep-related memory consolidation in epilepsy? A critical and systematic review. J Clin Sleep Med. 2022;18(10):2481-2495.

Sleep homeostasis, seizures, and cognition in children with focal epilepsy

AIM

To investigate the link between sleep disruption and cognitive impairment in childhood epilepsy by studying the effect of epilepsy on sleep homeostasis, as reflected in slow-wave activity (SWA).

METHOD

We examined SWA from overnight EEG-polysomnography in 19 children with focal epilepsy (mean [SD] age 11 years 6 months [3 years], range 6 years 6 months-15 years 6 months; 6 females, 13 males) and 18 age- and sex-matched typically developing controls, correlating this with contemporaneous memory consolidation task scores, full-scale IQ, seizures, and focal interictal discharges.

RESULTS

Children with epilepsy did not differ significantly from controls in overnight SWA decline (p = 0.12) or gain in memory performance with sleep (p = 0.27). SWA was lower in patients compared to controls in the first hour of non-rapid eye movement sleep (p = 0.021), although not in those who remained seizure-free (p = 0.26). Full-scale IQ did not correlate with measures of SWA in patients or controls. There was no significant difference in SWA measures between focal and non-focal electrodes.

INTERPRETATION

Overnight SWA decline is conserved in children with focal epilepsy and may underpin the preservation of sleep-related memory consolidation in this patient group. Reduced early-night SWA may reflect impaired or immature sleep homeostasis in those with a higher seizure burden.

Sleep in children with refractory epilepsy and epileptic encephalopathies: A systematic review of literature

Children with epilepsy have more sleep disorders compared to healthy children. The bidirectional interaction between epilepsy and sleep is not completely understood. However, disruption of sleep architecture during childhood may have consequences for cognitive development. As children with drug-refractory epilepsy often have intellectual disability, sleep disruption could be an important contributing factor in severity of their cognitive impairment. To better understand these interactions, sleep architecture in children with drug-refractory epilepsy and epileptic encephalopathies should be investigated. In this review, we conducted a systematic literature search on this topic. Articles that investigated sleep macro- and/or microstructure by means of electroencephalogram/polysomnography were included, as well as articles that used validated questionnaires. Sixteen articles were reviewed, eight of which used polysomnography. Only 2 articles examined sleep in children with epileptic encephalopathies. Consistent findings on measures of sleep architecture were a reduction in REM percentage and an increase in sleep fragmentation when comparing drug-refractory patients with non-refractory and healthy subjects. The findings on slow wave sleep were less clear. Studies with questionnaires unambiguously confirmed subjectively more sleep problems in children with drug-refractory epilepsy. This is the first review of literature in this patient population. More good quality sleep studies in children with drug-refractory epilepsy are warranted. The use of wearables in the home setting together with automatic sleep staging could provide more insights.

"Is this normal after such a major surgery?" Memory complaint after right temporal lobe excision in an adolescent

Memory deficits are commonly associated with temporal-lobe epilepsy. Memory may worsen after surgical resection of the temporal lobe. Risk factors for decline are structural integrity of the mesial temporal lobe structures and intact pre-operative memory. Subjective memory complaints are influenced by depression or other psychological disorders. A 16-year-old girl underwent resection from the right lateral and medial temporal lobe and after surgery she complained of a significant memory impairment, which was unexpected given her baseline assessment. Before undertaking a neuropsychological assessment, she was referred for a psychiatric consultation which revealed depression, leading to treatment with anditdepressant medication. Over time she also admitted to severe headaches and inadequate sleep. With these issues addressed, assessment indicated memory performance had not changed relative to her preoperative baseline with stability or improvement in memory across longitudinal assessments. This case illustrates the contribution of mood state and other potential factors in contributing to subjective memory complaints.

Hypothalamic Hamartomas: Evolving Understanding and Management

Hypothalamic hamartomas (HH) are rare, basilar developmental lesions with widespread comorbidities often associated with refractory epilepsy and encephalopathy. Imaging advances allow for early, even prenatal, detection. Genetic studies suggest mutations in GLI3 and other patterning genes are involved in HH pathogenesis. About 50%-80% of children with HH have severe rage and aggression and a majority of patients exhibit externalizing disorders. Behavioral disruption and intellectual disability may predate epilepsy. Neuropsychological, sleep, and endocrine disorders are typical. The purpose of this article is to provide a summary of the current understanding of HH and to highlight opportunities for future research.

Relationship between sleep quality and cognitive performance in patients with epilepsy

PURPOSE

To investigate the relationship between self-reported sleep quality and cognitive function in patients with epilepsy (PWE), as well as anxiety and depressive symptoms and patient quality of life (QoL).

METHODS

This multicenter cross-sectional study included PWE aged ≥12 years who were receiving ≥1 anti-seizure medication (ASM) and had not been diagnosed with a sleep disorder. Patients completed the Pittsburgh Sleep Quality Index (PSQI), the Epworth Sleepiness Scale (ESS), the Montreal Cognitive Assessment test (MoCA), the Hospital Anxiety and Depression Scale (HADS), and the Quality of Life in Epilepsy Inventory-10 (QOLIE-10).

RESULTS

The study enrolled 150 patients aged 16-83 years, mean age (standard deviation [SD]) 40.6 (15.2) years; 58.7% were female and 75.3% had focal epilepsy. Mean (SD) PSQI score was 4.71 (3.08), 44.4% of patients had impaired sleep quality (PSQI score ≥5), 19.9% had pathologic excessive daytime sleepiness (ESS score >12), and 32.7% had mild cognitive impairment (MoCA score <26). Within the PSQI, sleep disturbance (P = 0.036) and use of sleep medication (P = 0.006) scores were significantly higher in patients with mild cognitive impairment. Multiple regression analysis showed older age (regression coefficient [B], -0.086; 95% confidence interval [CI], -0.127, -0.045; P < 0.001) and the use of sleep medication component of the PSQI [B, -1.157; 95% CI, -2.064, -0.220; P = 0.013) were independently associated with lower MoCA score. Poor sleep quality was associated with probable anxiety and depression symptoms, and directly correlated with reduced QoL.

CONCLUSIONS

In PWE, sleep quality was not significantly independently associated with mild cognitive impairment, although poor sleep quality had a negative effect on mood and QoL.

Altered Sleep-Related Consolidation and Neurocognitive Comorbidity in CECTS

Our aim is to use neurophysiological sleep-related consolidation (SRC) phenomena to identify putative pathophysiological mechanisms in CECTS linked to diffuse neurocognitive deficits. We argue that there are numerous studies on the association between seizure aspects and neurocognitive functioning but not as many on interictal variables and neurocognitive deficits. We suggest two additional foci. First, the interictal presentation in CECTS and second, neuronal oscillations involved in SRC processes. Existing data on mechanisms through which interictal epileptiform spikes (IES) impact upon SRC indicate that they have the potential to: (a) perturb cross-regional coupling of neuronal oscillations, (b) mimic consolidation processes, (c) alter the precision of the spatiotemporal coupling of oscillations, and (d) variably impact upon SRC performance. Sleep spindles merit systematic study in CECTS in order to clarify: (a) the state of the slow oscillations (SOs) with which they coordinate, (b) the precision of slow oscillation-spindle coupling, and (c) whether their developmental trajectories differ from those of healthy children. We subsequently review studies on the associations between IES load during NREM sleep and SRC performance in childhood epilepsy. We then use sleep consolidation neurophysiological processes and their interplay with IES to help clarify the diffuse neurocognitive deficits that have been empirically documented in CECTS. We claim that studying SRC in CECTS will help to clarify pathophysiological mechanisms toward diverse neurocognitive deficits. Future developments could include close links between the fields of epilepsy and sleep, as well as new therapeutic neurostimulation targets. At the clinical level, children diagnosed with CECTS could benefit from close monitoring with respect to epilepsy, sleep and neurocognitive functions.

Sleep disruption in children and adolescents with epilepsy: A systematic review and meta-analysis

This systematic review and meta-analysis aims to assess and quantify putative differences in sleep architecture, sleep efficiency, sleep timing and broadly-defined sleep difficulties between children with and without epilepsy. Databases were searched systematically, and studies identified in PubMed, EMBASE, PsychINFO and Medline. The meta-analysis included 19 studies comparing a total of 901 children with epilepsy to 1470 healthy children. Relative to healthy children, children with epilepsy experienced reduced sleep time, sleeping on average 34 mins less across self-report, actigraphy, 24-h video-EEG and polysomnography measures. They had more sleep difficulties specifically in the domains of night waking, parasomnias and sleep disordered breathing. The analysis also revealed a significantly increased percentage of N2 sleep and decreased sleep efficiency in children with epilepsy compared to healthy children. These results illustrate that children with epilepsy are vulnerable to more sleep difficulties compared to healthy children. This suggests that screening for sleep difficulties should be an integral part in a diagnosis of epilepsy to ensure that clinically relevant sleep difficulties are identified and treated. Such an approach may ultimately aid in the development of treatment strategies which can contribute to improvements in both developmental and diagnostic outcomes for children with epilepsy.

Sleep-dependent memory consolidation in children with self-limited focal epilepsies

OBJECTIVE

Children with self-limited focal epilepsies of childhood (SLFE) are known to show impaired memory functions, particularly in the verbal domain. Interictal epileptiform discharges (IED) in these epilepsies are more pronounced in nonrapid eye movement (NREM) sleep. Nonrapid eye movement sleep is crucial for consolidation of newly-encoded memories. Therefore, we hypothesize that sleep-dependent memory consolidation is altered in relation to IED in children with SLFE.

METHODS

We conducted a prospective case-control study. We applied a verbal (word pair) and a visuospatial (two-dimensional [2D] object location) learning task, both previously shown to benefit from sleep in terms of memory consolidation. Learning took place in the evening, and retrieval was tested in the morning after a night of sleep. Electroencephalogram (EEG) was recorded across night. After sleep-stage scoring, the spike-wave index (SWI) was assessed at the beginning and the end of sleep. Fourteen patients with SLFE (age: 5.5 to 11.6 years) were compared with 15 healthy controls (age: 6.8 to 9.1 years) examined in a previous study.

RESULTS

In contrast to healthy controls (mean: +12.9% recalled word pairs, p = .003, standard deviation (SD) = 12.4%), patients did not show overnight performance gains in the verbal memory task (mean: +6.4% recalled word pairs, p > .05, SD = 17.3) Neither patients nor controls showed significant overnight changes in visuospatial task performance. Spike-wave index was negatively correlated with recall performance in the verbal but not in the visuospatial task.

SIGNIFICANCE

We found evidence for impaired overnight improvement of performance in children with SLFE in a verbal learning task, with high SWI rates predicting low recall performance. We speculate that spike-waves hamper long-term memory consolidation by interfering with NREM sleep.

'In the best case seizure-free' - Parental hopes and worries before and satisfaction after their child's epilepsy surgery

OBJECTIVE

The objective of this study was to gain a better understanding of parental hopes and worries before and subsequent experiences two years after their child had undergone epilepsy surgery.

METHODS

The parents of 107 children and young people who underwent epilepsy surgery at a single center completed surveys focusing on hopes and concerns before surgery and subsequent experiences at two-year follow-up. Responses were analyzed by thematic analysis.

RESULTS

Before surgery, parental hopes focus on not only seizure freedom or reduction but also potential improvements in child development and emotional-behavioral functioning. Worries before surgery include not only potential injury or loss of skills but also a concern that the surgical procedure would not lead to an improvement in the child's seizures. The vast majority of parents experienced positive aspects at the two-year follow-up including seizure freedom or reduction but also perceived improvements in behavior, development, and sleep. This suggests that for many, expectations for the surgery were met. A small number of parents reported negative effects of surgery including loss of skills, worsening/lack of improvement in seizure frequency, or negative impact on development.

SIGNIFICANCE

For the majority of parents whose children undergo surgery, expectations are met, and fears are not realized. Knowledge of parental hopes and worries before surgery as well as experiences after the operation is useful for improving pre- and postsurgical counseling.

Sleep architecture and homeostasis in children with epilepsy: a neurodevelopmental perspective

Although the influence of sleep on epilepsy has long been recognized, this relationship has yet to be fully exploited to benefit patients. The past decade has seen significant advances in understanding paediatric sleep, providing a framework by which to properly evaluate the sleep of children with epilepsy, which itself has been subject to increasing scrutiny. The role of sleep in learning and the potential for interictal discharges to disrupt sleep-related memory consolidation provide a novel perspective for understanding the association of childhood epilepsy with a high rate of intellectual disability. In this review, I outline the evolution of sleep duration, architecture, and homeostasis across childhood, relating this to the development of cognitive functions. I describe how these may be disrupted or preserved in children with epilepsy; in particular, collating data from polysomnography. Finally, I explore how sleep may, in the future, be modulated to improve cognitive outcome in these patients. WHAT THIS PAPER ADDS: Children with epilepsy have less rapid eye movement sleep than controls, but this improves with seizure cessation. Deep or slow-wave sleep is highly conserved in children with epilepsy. Sleep homeostasis may be disrupted either at a local or global level by the presence of interictal epileptiform discharges.

Generalized quasiperiodic epileptiform activity in sleep is associated with cognitive impairment in children with drug-resistant focal lesional epilepsy

OBJECTIVE

To evaluate the impact of generalized quasiperiodic epileptiform discharges ("hurdles") observed in non-rapid eye movement (NREM) sleep on cognitive function in children with intractable focal epilepsy. "Hurdles" pattern does not meet the criteria of the electrical status epilepticus in slow-wave sleep (ESES).

METHODS

In a retrospective analysis, 24 patients with "hurdles" and their 24 peers matched for demographic and epilepsy-related variables were compared in terms of neuropsychological domains and electroencephalography (EEG)-derived quantifiers. Both "hurdles" and controls were children between 2 and 19 years of age who had intractable focal epilepsy evaluated as candidates of resective epilepsy surgery.

RESULTS

Full-scale intelligence quotient/developmental quotient (FSIQ/DQ) (P = .002) and visuoconstructional skills (P = .004) were significantly lower in children with "hurdles" compared to controls. Patients with "hurdles" presented with higher interictal spike indexes in sleep (P < .001, median difference -0.9, 95% confidence interval [CI] -1.4, -0.6) and wakefulness (P < .001, median difference -0.3, 95% CI -0.5, -1). Relative time of sleep spindles in NREM sleep was significantly reduced (P < .001, median difference 0.1, 95% CI 0.0, 0.1) in the "hurdles" group. The time proportion of sleep spindles represented a significant positive (P = .008) and spike index of generalized spikes in sleep a significant negative explanatory variable (P = .004) of FSIQ/DQ scores. The proportion of seizure-free patients 2 years after epilepsy surgery did not differ significantly between the two groups (P = .19).

SIGNIFICANCE

Although the "hurdles" pattern does not fulfill the criteria of ESES, it is associated with a pronounced cognitive dysfunction. Disturbed sleep structure marked by reduced sleep spindles and generalized spiking in sleep is associated with worse cognitive performance. Despite having a generalized nature, we did not find a lower probability of postsurgical seizure freedom in patients with "hurdles" pattern.

Epilepsy as a derailment of sleep plastic functions may cause chronic cognitive impairment - A theoretical review

We report on a peculiar way of chronic cognitive impairment associated with interictal epileptic activity during NREM sleep. We review three major groups of epilepsy: mesiotemporal epilepsy (MTLE) involving the epileptic derailment of the hippocampal declarative memory system; childhood developmental epileptic encephalopathies; and the spectrum disorders of the perisylvian communication network with the centrotemporal spike phenomenon, overarching child- and adulthood epilepsies, totaling up the majority of epilepsies in childhood. We outline high impact research-lines on the cognitive harm of epilepsy; causing specific or global cognitive decline through its interference with sleep plastic functions. We highlight the key role of interictal activity in the development of cognitive impairment and the fact that we are unarmed against this harm, antiepileptic pharmaco-therapy being ineffective against the interictal process marked by spikes and high frequency oscillations.

Strong relationship between NREM sleep, epilepsy and plastic functions - A conceptual review on the neurophysiology background

The aim of this review is to summarize and discuss the strong bond between NREM sleep and epilepsy underlain by the shared link and effect on brain plasticity. Beyond the seizure occurrence rate, sleep relatedness may manifest in the enhancement of interictal epileptic discharges (spikes and pathological ripples). The number of the discharges as well as their propagation increase during NREM sleep, unmasking the epileptic network that is hidden during wakefulness. The interictal epileptic discharges associate with different sleep constituents (sleep slow waves, spindling and high frequency oscillations); known to play essential role in memory and learning. We highlight three major groups of epilepsies, in which sleep-related plastic functions suffer an epileptic derailment. In absence epilepsy mainly involving the thalamo-cortical system, sleep spindles transform to generalized spike-wave activity. In mesio-temporal epilepsy affecting the hippocampal declarative memory system, the sharp wave ripples derail to dysfunctional epileptic oscillations (spikes and pathological ripples). Idiopathic childhood epilepsies affecting the perisylvian network may progress to catastrophic status electricus during NREM sleep. In these major epilepsies, NREM sleep has a pivotal role in the development and course of the disorder. Epilepsy is born in-, and exhibits its pathological properties during NREM sleep. Interictal discharges are important causative agents in this process.