The Relationship Between Sleep and Epilepsy

Role of the orexin system in the bidirectional relation between sleep and epilepsy: New chances for patients with epilepsy by the antagonism to orexin receptors?

Epilepsy is a common neurological disorder, affecting patients of all ages, reducing the quality of life, and associated with several comorbidities. Sleep impairment is a frequent condition in patients with epilepsy (PWE), and the relation between sleep and epilepsy has been considered bidirectional, as one can significantly influence the other, and vice versa. The orexin system was described more than 20 years ago and is implicated in several neurobiological functions other than in controlling the sleep-wake cycle. Considering the relation between epilepsy and sleep, and the significant contribution of the orexin system in regulating the sleep-wake cycle, it is conceivable that the orexin system may be affected in PWE. Preclinical studies investigated the impact of the orexin system on epileptogenesis and the effect of orexin antagonism on seizures in animal models. Conversely, clinical studies are few and propose heterogeneous results also considering the different methodological approaches to orexin levels quantification (cerebrospinal-fluid or blood samples). Because orexin system activity can be modulated by sleep, and considering the sleep impairment documented in PWE, the recently approved dual orexin receptor antagonists (DORAs) have been suggested for treating sleep impairment and insomnia in PWE. Accordingly, sleep improvement can be a therapeutic strategy for reducing seizures and better managing epilepsy. The present review analyzes the preclinical and clinical evidence linking the orexin system to epilepsy, and hypothesizes a model in which the antagonism to the orexin system by DORAs can improve epilepsy by both a direct and a sleep-mediated (indirect) effect.

Reduced Sleep Quality Is Related to Poor Quality of Life in Patients with Juvenile Myoclonic Epilepsy, a Case-Control Study

Juvenile myoclonic epilepsy (JME) is a primary generalized epilepsy which is closely related to the sleep-wake cycle. This study aimed to investigate whether sleep disturbance is more common among patients with JME and the impact this may have on their quality of life (QOL). Thirty-four patients with JME and age- and gender-matched controls were recruited into this case control study, and assessed using validated sleep questionnaires including the Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), and Stanford Sleepiness Scale (SSS). QOL was assessed using the Quality of Life in Epilepsy Inventory (QOLIE-31). The patients had a significantly higher PSQI score and higher proportion of abnormal PSQI scores than the controls. They also had higher ESS and SSS scores, but without statistical significance. The patients with poor sleep quality had significantly lower overall QOL, emotional well-being, and energy/fatigue subscale scores. The use of a higher number of antiseizure medications, dosage of levetiracetam, and usage of antiseizure medication polytherapy were associated with sleep disorders. Our results showed that sleep disturbance is common in patients with JME, and also that it has an impact on their QOL.

Risk Factors Associated with Refractory Epilepsy in Patients with Tuberous Sclerosis Complex: A Systematic Review

BACKGROUND

Epilepsy affects 70-90% of patients with tuberous sclerosis complex (TSC). In one-third of them, the seizures become refractory to treatment. Drug-resistant epilepsy (DRE) carries a significant educational, social, cognitive, and economic burden. Therefore, determining risk factors that increase the odds of refractory seizures is needed. We reviewed current data on risk factors associated with DRE in patients with tuberous sclerosis.

METHODS

The review was performed according to the PRISMA guidelines. Embase, Cochrane Library, MEDLINE, and ClinicalTrial.gov databases were searched. Only full-text journal articles on patients with TSC which defined risk factors related to DRE were included.

RESULTS

Twenty articles were identified, with a cohort size between 6 and 1546. Seven studies were prospective. Three factors appear to significantly increase DRE risk: TSC2 mutation, infantile spasms, and a high number of cortical tubers.

CONCLUSIONS

A proper MRI and EEG monitoring, along with genetic testing, and close observation of individuals with early onset of seizures, allow identification of the patients at risk of DRE.

Is the glymphatic system the missing link between sleep impairments and neurological disorders? Examining the implications and uncertainties

Until recently, both the purpose of the biological need for sleep and the mechanism by which the central nervous system eliminated metabolic waste products were unknown. The glymphatic system is the recently discovered macroscopic waste clearance system for the CNS, which predominantly functions during sleep states. Important implications for the glymphatic system exist for a significant proportion of neurological disorders, including traumatic brain injury, epilepsy, stroke, migraine, and Alzheimer's disease. Within the limited amount of research pertaining to this novel system there exists controversy regarding several of the key structural and functional aspects of the glymphatic system. In this review we address evidence from both standpoints regarding the prominent debates surrounding the glymphatic system, including the functional differences in wakefulness vs. sleep, the role of glial aquaporin-4 water channels, and whether it reflects a convective flow or a passive diffusion process. The answers that underlie these questions will have crucial and distinct outcomes for the future of the glymphatic system and the disorders it has been implicated in. However, this review also summarizes the potential role of the glymphatic system in the development and progression of the aforementioned neurological disorders. Furthermore, the possible contribution of the orexinergic system to this relationship between the glymphatic system, sleep, and these neurological disorders is also explored. Overall, in order to develop and utilize therapeutic interventions centred around the glymphatic system we must first dedicate further investigation to elucidating these discrepancies and unanswered questions.

Impact of repeated kindled seizures on heart rate rhythms, heart rate variability, and locomotor activity in rats

Although an impact of epilepsy on circadian rhythmicity is well-recognized, there are profound gaps in our understanding of the influence of seizures on diurnal rhythms. The effect on activity levels and heart rate is of particular interest as it might contribute to the disease burden. The kindling model with telemetric transmitter implants provides excellent opportunities to study the consequences of focal and generalized seizures under standardized conditions. Data from kindled rats with generalized seizures revealed an increase in activity and heart rate during the resting phase. Total and short-term heart rate variabilities were not affected by electrode implantation or seizure induction. Ictal alterations in heart rate associated with generalized seizures were characterized by a biphasic bradycardia with an immediate drop of heart rate followed by a transient normalization and a second more steady decrease. In conclusion, the findings demonstrate that once daily generalized seizures can exert significant effects on heart rate rhythms. Respective alterations in patients would be of relevance for patient counselling and therapeutic management. Occurrence of biphasic bradycardia associated with seizure induction suggests that the kindling model is suitable to study the consequences and the prevention of ictal bradycardia, which may pose patients at risk for sudden unexpected death.

Sleep dysfunction following neonatal ischemic seizures are differential by neonatal age of insult as determined by qEEG in a mouse model

Neonatal seizures associated with hypoxic-ischemic encephalopathy (HIE) pose a challenge in their acute clinical management and are often followed by long-term neurological consequences. We used a newly characterized CD-1 mouse model of neonatal ischemic seizures associated with age-dependent (P7 vs. P10) seizure severity and phenobarbital efficacy (i.e.; PB-resistant vs. PB-efficacious respectively) following unilateral carotid ligation. The long-term consequences following untreated neonatal seizures in P7 vs. P10 ligated pups were investigated using neurobehavioral testing, 24 h v- quantitative EEG -EMG (qEEG, qEMG), and western blot analyses in adult mice. Significant hyperactivity emerged in a small sub-set of mice in both age-groups associated with a failure to habituate during open-field (OF) testing. 24 h continuous qEEGs detected significantly altered sleep architecture due to long-wake cycles in both age-groups. Delta power (0.5-4 Hz) quantification during slow-wave-sleep (SWS) revealed significant SWS compensation in P10 ligates following periods of increased sleep pressure which the P7 ligate group failed to show. Theta/beta ratios deemed as negative correlation markers of attentional control were significantly higher only in the P10 ligates. These results indicate that neonatal age-dependent differences in the characteristics of ischemic neonatal seizures in CD-1 pups differentially modulate long-term outcomes, when evaluated with v-qEEG/EMG as adults.

Orexin Receptor Antagonism Improves Sleep and Reduces Seizures in Kcna1-null Mice

STUDY OBJECTIVE

Comorbid sleep disorders occur in approximately one-third of people with epilepsy. Seizures and sleep disorders have an interdependent relationship where the occurrence of one can exacerbate the other. Orexin, a wake-promoting neuropeptide, is associated with sleep disorder symptoms. Here, we tested the hypothesis that orexin dysregulation plays a role in the comorbid sleep disorder symptoms in the Kcna1-null mouse model of temporal lobe epilepsy.

METHODS

Rest-activity was assessed using infrared beam actigraphy. Sleep architecture and seizures were assessed using continuous video-electroencephalography-electromyography recordings in Kcna1-null mice treated with vehicle or the dual orexin receptor antagonist, almorexant (100 mg/kg, intraperitoneally). Orexin levels in the lateral hypothalamus/perifornical region (LH/P) and hypothalamic pathology were assessed with immunohistochemistry and oxygen polarography.

RESULTS

Kcna1-null mice have increased latency to rapid eye movement (REM) sleep onset, sleep fragmentation, and number of wake epochs. The numbers of REM and non-REM (NREM) sleep epochs are significantly reduced in Kcna1-null mice. Severe seizures propagate to the wake-promoting LH/P where injury is apparent (indicated by astrogliosis, blood-brain barrier permeability, and impaired mitochondrial function). The number of orexin-positive neurons is increased in the LH/P compared to wild-type LH/P. Treatment with a dual orexin receptor antagonist significantly increases the number and duration of NREM sleep epochs and reduces the latency to REM sleep onset. Further, almorexant treatment reduces the incidence of severe seizures and overall seizure burden. Interestingly, we report a significant positive correlation between latency to REM onset and seizure burden in Kcna1-null mice.

CONCLUSION

Dual orexin receptor antagonists may be an effective sleeping aid in epilepsy, and warrants further study on their somnogenic and ant-seizure effects in other epilepsy models.

Orexin Receptor Antagonism Improves Sleep and Reduces Seizures in Kcna1-null Mice

STUDY OBJECTIVE

Comorbid sleep disorders occur in approximately one-third of people with epilepsy. Seizures and sleep disorders have an interdependent relationship where the occurrence of one can exacerbate the other. Orexin, a wake-promoting neuropeptide, is associated with sleep disorder symptoms. Here, we tested the hypothesis that orexin dysregulation plays a role in the comorbid sleep disorder symptoms in the Kcna1-null mouse model of temporal lobe epilepsy.

METHODS

Rest-activity was assessed using infrared beam actigraphy. Sleep architecture and seizures were assessed using continuous video-electroencephalography-electromyography recordings in Kcna1-null mice treated with vehicle or the dual orexin receptor antagonist, almorexant (100 mg/kg, intraperitoneally). Orexin levels in the lateral hypothalamus/perifornical region (LH/P) and hypothalamic pathology were assessed with immunohistochemistry and oxygen polarography.

RESULTS

Kcna1-null mice have increased latency to rapid eye movement (REM) sleep onset, sleep fragmentation, and number of wake epochs. The numbers of REM and non-REM (NREM) sleep epochs are significantly reduced in Kcna1-null mice. Severe seizures propagate to the wake-promoting LH/P where injury is apparent (indicated by astrogliosis, blood-brain barrier permeability, and impaired mitochondrial function). The number of orexin-positive neurons is increased in the LH/P compared to wild-type LH/P. Treatment with a dual orexin receptor antagonist significantly increases the number and duration of NREM sleep epochs and reduces the latency to REM sleep onset. Further, almorexant treatment reduces the incidence of severe seizures and overall seizure burden. Interestingly, we report a significant positive correlation between latency to REM onset and seizure burden in Kcna1-null mice.

CONCLUSION

Dual orexin receptor antagonists may be an effective sleeping aid in epilepsy, and warrants further study on their somnogenic and ant-seizure effects in other epilepsy models.

Influence of sleep and sleep deprivation on ictal and interictal epileptiform activity

Sleep is probably one of the most important physiological factors implicated both in epileptic seizures and interictal epileptiform discharges. The neurophysiology concerning the relationship between sleep and epilepsy is well described in the literature; however, the pathological events that culminate in the seizures are poorly explored. The present paper intends to make a rigorous approach to the main mechanisms involved in this reciprocal relation. Knowledge of sleep and sleep deprivation effects in epilepsy stands as crucial in the understanding of how seizures are produced, their possible lines of treatment, and future research.

Treatment initiation in epilepsy: an expert consensus in Spain

OBJECTIVE

The goals of this study were to explore the diverse criteria surrounding indications for antiepileptic therapy and to establish a consensus on drug selection for initial monotherapy in adult patients with epilepsy.

METHODS

The study was performed using the modified Delphi method, which aims to achieve professional consensus by means of a series of questionnaires. Three different groups of items were evaluated: the beginning of antiepileptic treatment, the drug selected for initial monotherapy with respect to the type of epilepsy, and the drug selected for initial monotherapy with respect to comorbidity.

RESULTS

Sixty experts completed two rounds of a questionnaire. In the first round, consensus was reached on 135 of the 194 questions analyzed. After the second round, consensus was reached on 148 items. The main findings of the survey revealed a consensus on beginning treatment after the first seizure when the EEG showed abnormalities such as generalized spike-wave discharges, when MRI demonstrated an epileptogenic brain lesion, and in elderly patients. Regarding to the antiepileptic drug selected for initial monotherapy with respect to type of epilepsy, levetiracetam and lamotrigine were recommended for generalized tonic-clonic seizures regardless of sex or age; levetiracetam was recommended for myoclonic epilepsy regardless of sex; valproic acid, ethosuximide, levetiracetam, and lamotrigine were chosen for absence epilepsy; and carbamazepine, levetiracetam, lamotrigine, and oxcarbazepine were recommended for partial epilepsy regardless of age or sex. Finally, in the evaluation of drug selection with respect to comorbidity, first-generation drugs were less recommended than second-generation drugs, which were clearly preferable. The drugs on which there was a greater consensus were levetiracetam, lamotrigine, valproic acid, and topiramate.

CONCLUSIONS

There is a tendency to begin treatment after the first seizure, depending on the results of additional testing. In general, first-generation drugs are less recommended for different types of epilepsy, especially in the presence of a comorbid condition. However, the authors are conveying perceptions and opinions, the effect of which on treatment outcomes has not been evaluated.

Sleep-dependent directional coupling between human neocortex and hippocampus

Complex interactions between neocortex and hippocampus are the neural basis of memory formation. Two-step theories of memory formation suggest that initial encoding of novel information depends on the induction of rapid plasticity within the hippocampus, and is followed by a second sleep-dependent step of memory consolidation. These theories predict information flow from the neocortex into the hippocampus during waking state and in the reverse direction during sleep. However, experimental evidence that interactions between hippocampus and neocortex have a predominant direction which reverses during sleep rely on cross-correlation analysis of data from animal experiments and yielded inconsistent results. Here, we investigated directional coupling in intracranial EEG data from human subjects using a phase-modeling approach which is well suited to reveal functional interdependencies in oscillatory data. In general, we observed that the anterior hippocampus predominantly drives nearby and remote brain regions. Surprisingly, however, the influence of neocortical regions on the hippocampus significantly increased during sleep as compared to waking state. These results question the standard model of hippocampal-neocortical interactions and suggest that sleep-dependent consolidation is accomplished by an active retrieval of hippocampal information by the neocortex.