The relationship between sleep and epilepsy

Sleep Deprivation and Neurological Disorders

Sleep plays an important role in maintaining neuronal circuitry, signalling and helps maintain overall health and wellbeing. Sleep deprivation (SD) disturbs the circadian physiology and exerts a negative impact on brain and behavioural functions. SD impairs the cellular clearance of misfolded neurotoxin proteins like α-synuclein, amyloid-β, and tau which are involved in major neurodegenerative diseases like Alzheimer's disease and Parkinson's disease. In addition, SD is also shown to affect the glymphatic system, a glial-dependent metabolic waste clearance pathway, causing accumulation of misfolded faulty proteins in synaptic compartments resulting in cognitive decline. Also, SD affects the immunological and redox system resulting in neuroinflammation and oxidative stress. Hence, it is important to understand the molecular and biochemical alterations that are the causative factors leading to these pathophysiological effects on the neuronal system. This review is an attempt in this direction. It provides up-to-date information on the alterations in the key processes, pathways, and proteins that are negatively affected by SD and become reasons for neurological disorders over a prolonged period of time, if left unattended.

Sleep onset uncovers thalamic abnormalities in patients with idiopathic generalised epilepsy

The thalamus is crucial for sleep regulation and the pathophysiology of idiopathic generalised epilepsy (IGE), and may serve as the underlying basis for the links between the two. We investigated this using EEG-fMRI and a specific emphasis on the role and functional connectivity (FC) of the thalamus. We defined three types of thalamic FC: thalamocortical, inter-hemispheric thalamic, and intra-hemispheric thalamic. Patients and controls differed in all three measures, and during wakefulness and sleep, indicating disorder-dependent and state-dependent modification of thalamic FC. Inter-hemispheric thalamic FC differed between patients and controls in somatosensory regions during wakefulness, and occipital regions during sleep. Intra-hemispheric thalamic FC was significantly higher in patients than controls following sleep onset, and disorder-dependent alterations to FC were seen in several thalamic regions always involving somatomotor and occipital regions. As interactions between thalamic sub-regions are indirect and mediated by the inhibitory thalamic reticular nucleus (TRN), the results suggest abnormal TRN function in patients with IGE, with a regional distribution which could suggest a link with the thalamocortical networks involved in the generation of alpha rhythms. Intra-thalamic FC could be a more widely applicable marker beyond patients with IGE.

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Sleep onset modifies thalamic FC in generalised epilepsy differently to controls.

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Differences are regionally specific.

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Regions connected to somatomotor/occipital cortices are consistently affected.

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Intra-thalamic FC may be a surrogate marker of thalamic reticular nucleus function.

The Usefulness of Nap Sleep Recording During Routine Electroencephalography: An Audit Study

OBJECTIVES

A measure to increase the electroencephalogram (EEG) outcome includes a short period of nap sleep during a routine standard EEG with the aim of increasing its sensitivity to interictal abnormalities or provoking seizures. As part of an ongoing auditing of our EEG data, we aimed to investigate the contribution of nap sleep during routine outpatient department based EEGs requested for a variety of reasons.

METHODS

EEG data at the Department of Clinical Physiology at Sultan Qaboos University Hospital, Oman, from July 2006 to December 2007 and from January 2009 to December 2010 (total 42 months) were reviewed. The EEGs were for patients older than 13-years referred for possible epilepsy, blackouts, headache, head trauma, and other non-specified attacks. The recording period was between 20 to 40 minutes. Abnormalities were identified during waking and nap sleep periods.

RESULTS

A total of 2 547 EEGs were reviewed and 744 were abnormal (29.2%). Of those abnormal EEGs, nap sleep was obtained in 258 (34.7%) EEGs, and 39 (15.1%) showed abnormalities during nap sleep. Nineteen out of the 39 (48.7%) EEGs were abnormal during awake and nap sleep; and 20 (51.3%) were abnormal during nap sleep, which represented only 2.7% of the total abnormal EEGs (n = 744).

CONCLUSIONS

The contribution of the short nap sleep to the pickup rate of interictal abnormalities in EEG was minimal. We recommend the EEG service to include one cycle of spontaneous sleep EEG directed at patients with a history suggestive of epilepsy if their awake EEGs are normal.

Clinical characterization of the pre-ictal state in the pediatric population: A caretaker's perspective

The unpredictability of seizures causes distress to patients with epilepsy and their caretakers. To date, no studies have explored seizure prediction specifically in the pediatric population. If the period of time preceding a seizure can be reliably identified, either by child or caretaker, there may be a role for pre-emptive interventions. The aim of this study was to investigate caretaker seizure prediction. A questionnaire was distributed to caretakers of patients with epilepsy. The patients were 0-21years old and experienced ≥1 seizure within the past year. We excluded patients with non-epileptic seizures or daily seizures. One hundred and fifty of 240 questionnaires met criteria. Of these, 32 (21.6%) caretakers indicated a positive report of seizure prediction. Age of seizure onset was earlier in the positive predictive group (3.3±3.3years) than in the non-predictor group (5.3±4.8years) (p=0.01). The most common pre-ictal symptoms reported were being tired, hazy look, and sleepiness. A total of 76.6% of caretakers reported at least one seizure precipitant. The prevalence of positive caretaker seizure prediction in this study is similar to that of seizure self-prediction in adult studies. These findings will be used to design prospective online or electronic diary studies to further investigate the caretaker's, as well as children's, perspectives on seizure prediction. We anticipate that this investigation may lead to novel treatments during times of high seizure risk.

Slow wave sleep and accelerated forgetting

We investigated whether the benefit of slow wave sleep (SWS) for memory consolidation typically observed in healthy individuals is disrupted in people with accelerated long-term forgetting (ALF) due to epilepsy. SWS is thought to play an active role in declarative memory in healthy individuals and, furthermore, electrographic epileptiform activity is often more prevalent during SWS than during wakefulness or other sleep stages. We studied the relationship between SWS and the benefit of sleep for memory retention using a word-pair associates task. In both the ALF and the healthy control groups, sleep conferred a memory benefit. However, the relationship between the amount of SWS and sleep-related memory benefits differed significantly between the groups. In healthy participants, the amount of SWS correlated positively with sleep-related memory benefits. In stark contrast, the more SWS, the smaller the sleep-related memory benefit in the ALF group. Therefore, contrary to its role in healthy people, SWS-associated brain activity appears to be deleterious for memory in patients with ALF.

Sleep and Epilepsy

Sleep and epilepsy are common bedfellows. Sleep can affect frequency and occurrence of interictal spikes and occurrence, timing, and threshold of seizure. Epilepsy can worsen sleep architecture and severity of sleep disorders. Thus, a vicious cycle is set. Certain epilepsy syndromes are so intertwined with sleep that they are considered sleep-related epilepsies. Poor sleep in epilepsy is multifactorial and is worsened by poorly controlled seizures. On the contrary, poor sleep is associated with worsened quality of life, psychological function, and memory. Improving sleep has been noted to improve seizure frequency and an overall well-being in patients with epilepsy. Hence, an emphasis should be given to address sleep in patients with epilepsy. These interactions are discussed in detail in this review.

Does abnormal glycogen structure contribute to increased susceptibility to seizures in epilepsy?

Epilepsy is a family of brain disorders with a largely unknown etiology and high percentage of pharmacoresistance. The clinical manifestations of epilepsy are seizures, which originate from aberrant neuronal synchronization and hyperexcitability. Reactive astrocytosis, a hallmark of the epileptic tissue, develops into loss-of-function of glutamine synthetase, impairment of glutamate-glutamine cycle and increase in extracellular and astrocytic glutamate concentration. Here, we argue that chronically elevated intracellular glutamate level in astrocytes is instrumental to alterations in the metabolism of glycogen and leads to the synthesis of polyglucosans. Unaccessibility of glycogen-degrading enzymes to these insoluble molecules compromises the glycogenolysis-dependent reuptake of extracellular K(+) by astrocytes, thereby leading to increased extracellular K(+) and associated membrane depolarization. Based on current knowledge, we propose that the deterioration in structural homogeneity of glycogen particles is relevant to disruption of brain K(+) homeostasis and increased susceptibility to seizures in epilepsy.

Sleep-dependent memory consolidation and accelerated forgetting

Accelerated long-term forgetting (ALF) is a form of memory impairment in which learning and initial retention of information appear normal but subsequent forgetting is excessively rapid. ALF is most commonly associated with epilepsy and, in particular, a form of late-onset epilepsy called transient epileptic amnesia (TEA). ALF provides a novel opportunity to investigate post-encoding memory processes, such as consolidation. Sleep is implicated in the consolidation of memory in healthy people and a deficit in sleep-dependent memory consolidation has been proposed as an explanation for ALF. If this proposal were correct, then sleep would not benefit memory retention in people with ALF as much as in healthy people, and ALF might only be apparent when the retention interval contains sleep. To test this theory, we compared performance on a sleep-sensitive memory task over a night of sleep and a day of wakefulness. We found, contrary to the hypothesis, that sleep benefits memory retention in TEA patients with ALF and that this benefit is no smaller in magnitude than that seen in healthy controls. Indeed, the patients performed significantly more poorly than the controls only in the wake condition and not the sleep condition. Patients were matched to controls on learning rate, initial retention, and the effect of time of day on cognitive performance. These results indicate that ALF is not caused by a disruption of sleep-dependent memory consolidation. Instead, ALF may be due to an encoding abnormality that goes undetected on behavioural assessments of learning, or by a deficit in memory consolidation processes that are not sleep-dependent.

Pediatric sleep pharmacology

This article reviews common sleep disorders in children and pharmacologic options for them. Discussions of pediatric sleep pharmacology typically focus on treatment of insomnia. Although insomnia is a major concern in this population, other conditions of concern in children are presented, such as narcolepsy, parasomnias, restless legs syndrome, and sleep apnea.

Rats with different thresholds for DMCM-induced clonic convulsions differ in the sleep-time of diazepam and [(3)H]-Ro 15-4513 binding

The current study investigated the possible inherent relationship between convulsions and sleep involving the GABA(A)/benzodiazepine site complex. The aim of this study was to determine if rats with high (HTR) and low (LTR) thresholds for clonic convulsions induced by DMCM, a benzodiazepine inverse agonist, differ in the following aspects: (1) sensitivity to the hypnotic effects of the GABA(A) positive allosteric modulators diazepam, pentobarbital and ethanol and (2) in the binding of [(3)H]-flunitrazepam, a benzodiazepine agonist, measured by autoradiography, and [(3)H]-Ro 15-4513, a benzodiazepine partial inverse agonist, to membranes from discrete brain regions. The LTR subgroup presented a shorter diazepam-induced sleeping time compared to that of the HTR subgroup. Biochemical assays revealed that the LTR subgroup did not differ in [(3)H]-flunitrazepam binding compared to the HTR subgroup. With respect to the binding of [(3)H]-Ro 15-4513, the LTR subgroup had higher binding in the brainstem and lower binding in the striatum compared to the HTR subgroup. These results suggest that differences in the benzodiazepine site on the GABA(A) receptor may underlie the susceptibility to DMCM-induced convulsions and sensitivity to the hypnotic effect of diazepam.

Continuous spike and waves during sleep and electrical status epilepticus in sleep

Continuous spike and waves during sleep is an age-related epileptic encephalopathy that presents with neurocognitive regression, seizures, and an EEG pattern of electrical status epilepticus during sleep. Patients usually present around 5 years of age with infrequent nocturnal unilateral motor seizures that progress within 1 to 2 years to a severe epileptic encephalopathy with frequent seizures of different types, marked neurocognitive regression, and an almost continuous spike-wave EEG pattern during slow-wave sleep. The pathophysiology of continuous spike and waves during sleep is not completely understood, but the corticothalamic neuronal network involved in physiologic oscillating patterns of sleep is thought to be switched into a pathologic discharging mode. Early developmental injury and/or genetic predisposition may play a role in the potentiation of age-related hyperexcitability in the immature brain. A better understanding of the mechanisms leading to electrical status epilepticus during sleep may provide additional therapeutic targets that can improve the outcome of seizures, EEG pattern, and cognitive development in patients with continuous spike and waves during sleep.

North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition consensus statement on the diagnosis and management of cyclic vomiting syndrome

Cyclic vomiting syndrome (CVS) is a disorder noted for its unique intensity of vomiting, repeated emergency department visits and hospitalizations, and reduced quality of life. It is often misdiagnosed due to the unappreciated pattern of recurrence and lack of confirmatory testing. Because no accepted approach to management has been established, the task force was charged to develop a report on diagnosis and treatment of CVS based upon a review of the medical literature and expert opinion. The key issues addressed were the diagnostic criteria, the appropriate evaluation, the prophylactic therapy, and the therapy of acute attacks. The recommended diagnostic approach is to avoid "shotgun" testing and instead to use a strategy of targeted testing that varies with the presence of 4 red flags: abdominal signs (eg, bilious vomiting, tenderness), triggering events (eg, fasting, high protein meal), abnormal neurological examination (eg, altered mental status, papilledema), and progressive worsening or a changing pattern of vomiting episodes. Therapeutic recommendations include lifestyle changes, prophylactic therapy (eg, cyproheptadine in children 5 years or younger and amitriptyline for those older than 5), and acute therapy (eg, 5-hydroxytryptamine receptor agonists, termed triptans herein, as abortive therapy, and 10% dextrose and ondansetron for those requiring intravenous hydration). This document represents the official recommendations of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition for the diagnosis and treatment of CVS in children and adolescents.

Epilepsy in women: special considerations for adolescents

Adolescence is a time of many changes. It is a time of growing independence, physical and emotional change, accompanied by social insecurity. Girls tend to enter puberty ahead of their male peers, growing and changing physically. Our culture tells adolescents that they are still immature, but their bodies are saying otherwise. The adolescents are also becoming aware of themselves as individuals, separate from their parents, and are presented with the challenges of independent thinking and action. If, in the midst of all of these changes, an adolescent is given the diagnosis of a chronic disease such as epilepsy, there is an additional burden. Often the adolescent must go through a variety of emotions, including shame, denial, anger, and sadness. Our role as medical providers is to provide some perspective to the illness and help guide our adolescent patient through the tumultuous emotions of grieving and acceptance. We must provide a foundation of assistance and emotional support, as well as medical knowledge. With a firm but compassionate hand, we can help them cope with their disorder. In this chapter, Drs. Haut and Zupanc explore some of the unique considerations in adolescent women with epilepsy. The first part of the chapter deals with the epidemiologic diagnosis of epilepsy in adolescence, the effect of epilepsy on reproductive health, hormonal influences on epilepsy (including catamenial seizures), and the effects of antiepileptic drugs (AEDs) on hormones, contraception, and bone health. In the second part of the chapter, we deal with the very real psychosocial issues and comorbidities of epilepsy, including quality of life, school performance, depression, migraine headaches, social stigma, and lifestyle changes. In the final section, the authors suggest strategies for clinical patient management.

Diurnal gene expression patterns of T-type calcium channels and their modulation by ethanol

The transient (T-type) calcium channel participates in the generation of normal brain rhythms as well as abnormal rhythms associated with a range of neurological disorders. There are three different isoforms of T-type channels and all are particularly enriched in the thalamus, which is involved in generating many of these rhythms. We report a novel means of T-type channel regulation in the thalamus that involves diurnal regulation of gene expression. Using real time polymerase chain reaction we detected a diurnal pattern of gene expression for all T-type channel transcripts. The peak of gene expression for the CaV3.1 transcript occurred close to the transition from active to inactive (sleep) states, while expression for both CaV3.2 and CaV3.3 peaked near the transition of inactive to active phase. We assessed the effect of chronic consumption of ethanol on these gene expression patterns by examining thalamic tissues of ethanol-consuming cohorts that were housed with the controls, but which received ethanol in the form of a liquid diet. Ethanol consumption resulted in a significant shift of peak gene expression of approximately 5 h for CaV3.2 toward the normally active phase of the mice, as well as increasing the overall gene expression levels by approximately 1.7-fold. Peak gene expression was significantly increased for both CaV3.2 and CaV3.3. Measurements of CaV3.3 protein expression reflected increases in gene expression due to ethanol. Our results illustrate a novel regulatory mechanism for T-type calcium channels that is consistent with their important role in generating thalamocortical sleep rhythms, and suggests that alterations in the pattern of gene expression of these channels could contribute to the disruption of normal sleep by ethanol.

Daytime behavior and sleep disturbance in childhood epilepsy

The purpose of this research is to further explore the relationship between sleep disturbance and daytime behavior in children with epilepsy. Parent-rating questionnaires and child symptom self-report measures were employed to evaluate daytime behavior in 30 children with epilepsy and sleep-disordered symptoms. Overnight polysomnography was used to assess for nocturnal sleep problems such as obstructive sleep apnea, nocturnal seizures, periodic leg movements, and sleep fragmentation. We hypothesized that children with epilepsy would exhibit both clinically significant behavioral and sleep problems. Results indicate that 80% of children with epilepsy exhibited sleep disruption because of either clinically significant obstructive apnea syndrome, disturbance of sleep architecture, or sleep fragmentation. These findings further suggest that daytime behavior problems encountered in children with epilepsy may be attributed to specific disruptions in sleep regulation.

Sleep disorders in childhood

Childhood sleep-wake disorders are common and associated with significant impairment of quality of life. The recent discovery of hypocretin deficiency as the pathophysiologic basis for narcolepsy-cataplexy is likely to spur the development of hypocretin analogs for definitive treatment [82,83]. The link between disrupted sleep and daytime learning and childhood inattention is a challenging area of mind-brain interaction in which further progress is likely, once methodologic issues have been sorted out. The recent recognition of genetic influences in the control of circadian rhythms also may spur the development of specific therapies for circadian rhythm disorders. In many ways, sleep medicine is benefiting from recent progress in the basic neurosciences, genetics, and technology.

Paroxysms of excitement: sodium channel dysfunction in heart and brain

Inherited disorders of ion-channels are associated with paroxysmal dysfunction of excitable tissues and manifest as diseases of the brain, heart and skeletal muscle. These so-called channelopathies have now been described for most of the major categories of voltage-dependent ion-channels including those selectively permeable to sodium. Sodium channelopathies affecting the heart and brain are reviewed in this essay. They show striking differences and similarities including, for example, their responsiveness to changes in body temperature and sleep state. They represent a paradigm for efforts to trace disturbed behaviour of physiological systems back to its molecular origins and understanding their molecular basis may provide clues to important health issues such as cardiac side effects of drugs and response to medication used to treat epilepsy.