Combined influence of cyclic arousability and EEG synchrony on generalized interictal discharges within the sleep cycle

Restless sleep disorder in children with epileptic and non-epileptic nocturnal attacks

Restless sleep disorder (RSD) is an important sleep disorder characterised by the presence of frequent large muscle movements (LMM) during sleep, which may be comorbid to other conditions/diseases. In this study, we investigated the frequency and the characteristics of RSD among children who were evaluated by polysomnography (PSG) due to epileptic and non-epileptic nocturnal attacks. We analysed consecutively children younger than 18 years who were referred for PSG recording due to abnormal motor activities during sleep. The diagnosis of nocturnal events as sleep-related epilepsy was made based on the current consensus. Patients who were referred with suspicion of sleep-related epilepsy, but who were diagnosed to have non-epileptic nocturnal events and children with a definitive diagnosis of NREM sleep parasomnias were also enrolled. Sixty-two children were analysed in this study (17 children with sleep-related epilepsy, 20 children with NREM parasomnia, and 25 children with nocturnal events not otherwise classified [neNOS]). The mean number of LMM, LMM index, LMM-associated with arousal and its index were all significantly higher in children with sleep-related epilepsy. Restless sleep disorder was present in 47.1% of patients with epilepsy, 25% of patients with parasomnia, and in 20% of patients with neNOS. The mean A3 duration and the A3 index were higher in children with sleep-related epilepsy and RSD compared with those with parasomnia and restless sleep disorder. Patients with RSD had lower ferritin levels than those without RSD in all subgroups. Our study demonstrates a high prevalence of restless sleep disorder in children with sleep-related epilepsy, associated with an increased cyclic alternating pattern.

NREM Sleep and Antiepileptic Medications Modulate Epileptiform Activity by Altering Cortical Synchrony

INTRODUCTION

The activating role of non-rapid eye movement (NREM) sleep on epileptic cortex and conversely, the seizure remission brought about by antiepileptic medications, has been attributed to their effects on neuronal synchrony. This study aims to understand the role of neural synchrony of NREM sleep in promoting interictal epileptiform discharges (IEDs) in patients with epilepsy (PWE) by assessing the peri-IED phase synchrony during awake and sleep states. It also studies the role played by antiepileptic drugs (AEDs) on EEG desynchronization in the above cohort.

METHODS

A total of 120 PWE divided into 3 groups (each n = 40; juvenile myoclonic epilepsy [JME], temporal lobe epilepsy [TLE]. and extratemporal lobe epilepsy [Ex-TLE]) were subjected to overnight polysomnography. Each patient group was subdivided into drug-naive and on treatment (Each n = 20). EEG phase synchronization analysis was performed to compare peri-IED phase synchronization indices (SI) during awake and sleep stages and between drug naïve and on treatment groups in 4 frequency bands, namely delta, theta, alpha, and beta. The mean ± SD of peri-IED SI among various subgroups was compared employing a multilevel mixed effects modeling approach.

RESULTS

Patients with JME had increased peri-IED cortical synchrony in N3 sleep stage, whereas patients with partial epilepsy had increased IED cortical synchrony in N1 sleep stage. On the other hand, peri-IED synchrony was lower during wake and REM sleep. We also found that peri-IED synchronization in patients with JME was higher in drug-naive patients compared with those on sodium valproate monotherapy in theta, alpha, and beta bands.

CONCLUSION

The findings of this study suggest that sleep stages can alter cortical synchrony in patients with JME and focal epilepsy, with NREM IEDs being more synchronized and wake/REM IEDs being less synchronized. Furthermore, it also suggests that AEDs alleviate seizures in PWE by inhibiting cortical synchrony.

Epileptiform K-Complexes and Sleep Spindles: An Underreported Phenomenon in Genetic Generalized Epilepsy

PURPOSE

To study the frequency of epileptiform K-complexes and sleep spindles as well as clinical variables influencing those abnormalities.

METHODS

We prospectively performed 24-hour ambulatory EEGs in a cohort of patients with genetic generalized epilepsy diagnosed and classified according to the International League against Epilepsy criteria. Overlapping of epileptiform discharges with K-complexes and sleep spindles was defined as epileptiform K-complexes and epileptiform sleep spindles. The presence of epileptiform K-complexes and sleep spindles was tabulated for each patient, and frequencies were calculated. We performed multiple regression analysis to study the influence of clinical predictors on the occurrence of epileptiform K-complexes and sleep spindles. The predictor variables tested in the model were seizure-free duration, epilepsy duration, genetic generalized epilepsy syndrome, number of antiepileptic drugs, use of sodium valproate, and use of lamotrigine.

RESULTS

A total of 107 patients (37 males and 70 females) were studied. The mean age was 28.5 ± 10.7 years (range, 13-58). Juvenile absence epilepsy was the most common epilepsy syndrome in the cohort (31.8%), followed by generalized epilepsy with tonic-clonic seizures only (26.2%), juvenile myoclonic epilepsy (26.2%), and childhood absence epilepsy (14%). Epileptiform K-complexes and sleep spindles were seen in 65.4% and 10.3% of patients, respectively. None of the clinical variables had any significant impact on the occurrence of epileptiform K-complexes and sleep spindles in our multivariable analysis.

CONCLUSIONS

Epileptiform K-complexes are common in the sleep EEGs of patients diagnosed with genetic generalized epilepsy. This underreported phenomenon highlights the important association of arousals and epileptiform discharges in genetic generalized epilepsy.

Why are seizures rare in rapid eye movement sleep? Review of the frequency of seizures in different sleep stages

Since the formal characterization of sleep stages, there have been reports that seizures may preferentially occur in certain phases of sleep. Through ascending cholinergic connections from the brainstem, rapid eye movement (REM) sleep is physiologically characterized by low voltage fast activity on the electroencephalogram, REMs, and muscle atonia. Multiple independent studies confirm that, in REM sleep, there is a strikingly low proportion of seizures (~1% or less). We review a total of 42 distinct conventional and intracranial studies in the literature which comprised a net of 1458 patients. Indexed to duration, we found that REM sleep was the most protective stage of sleep against focal seizures, generalized seizures, focal interictal discharges, and two particular epilepsy syndromes. REM sleep had an additional protective effect compared to wakefulness with an average 7.83 times fewer focal seizures, 3.25 times fewer generalized seizures, and 1.11 times fewer focal interictal discharges. In further studies REM sleep has also demonstrated utility in localizing epileptogenic foci with potential translation into postsurgical seizure freedom. Based on emerging connectivity data in sleep, we hypothesize that the influence of REM sleep on seizures is due to a desynchronized EEG pattern which reflects important connectivity differences unique to this sleep stage.

Interrelationship of sleep and juvenile myoclonic epilepsy (JME): a sleep questionnaire-, EEG-, and polysomnography (PSG)-based prospective case-control study

We studied the effects of 'epilepsy on sleep and its architecture' and 'sleep on the occurrence and distribution of interictal epileptiform discharges (ED)' using 'sleep questionnaires', 'EEG', and 'PSG' in patients with JME. Forty patients with JME [20 on valproate (Group I - 20.8±4.0 years; M: F=9:11) and 20 drug-naïve (Group II - 24.4±6.7 years; M: F=9:11)] and 20 controls (M: F=9:11; age: 23.5±4.7 years) underwent assessment with Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), overnight PSG, and scalp-EEG. Epileptiform discharges (EDs) were quantified in different sleep stages. The 'ED Index' was derived as number of EDs/min per stage. Statistical Package for the Social Sciences (SPSS) vs. 11 was used for statistical analysis. A 'p' <0.05 was considered as statistically significant. There was poor sleep quality in patients compared to controls (p=0.02), while there was no significant difference in ESS scores between the groups. The PSG parameters were comparable in both groups. Routine EEG revealed EDs in 22/40 (Group I: 7 and Group II: 15) patients. Thirty-five patients had EDs in various sleep stages during PSG (Group I: 17 and Group II: 18): N1 - Group I: 9 and Group II: 14, N2 - Group I: 14 and Group II: 14, N3 - Group I: 14 and Group II: 10, and REM - Group I: 9 and Group II: 11. The ED Index was higher during N2/N3 in Group I and N1/REM in Group II. The epileptiform discharges were frequently associated with arousals in N1/REM and K-complexes in N2. There was no other significant difference between Groups I and II. In conclusion, there was poor sleep quality in patients with JME compared to controls, especially those on valproate who had altered sleep architecture. Epileptiform activity was observed more often in sleep than wakefulness. Sleep stages had variable effect on epileptiform discharges with light sleep having a facilitatory effect in the drug-naïve group and slow wave sleep having a facilitatory effect in the valproate group.

The sleep phenotypes of attention deficit hyperactivity disorder: the role of arousal during sleep and implications for treatment

About 25-50% of children and adolescents with attention-deficit hyperactivity disorder (ADHD) experience sleep problems. An appropriate assessment and treatment of such problems might improve the quality of life in such patients and reduce both the severity of ADHD and the impairment it causes. According to data in the literature and to the overall complexity of the interaction between ADHD and sleep, five sleep phenotypes may be identified in ADHD: (i) a sleep phenotype characterized mainly by a hypo-arousal state, resembling narcolepsy, which may be considered a "primary" form of ADHD (i.e. without the interference of other sleep disorders); (ii) a phenotype associated with delayed sleep onset latency and with a higher risk of bipolar disorder; (iii) a phenotype associated with sleep disordered breathing (SDB); (iv) another phenotype related to restless legs syndrome (RLS) and/or periodic limb movements; (v) lastly, a phenotype related to epilepsy/or EEG interictal discharges. Each sleep phenotype is characterized by peculiar sleep alterations expressed by either an increased or decreased level of arousal during sleep that have important treatment implications. Treatment with stimulants is recommended above all in the primary form of ADHD, whereas treatment of the main sleep disorders or of co-morbidities (i.e. bipolar disorders and epilepsy) is preferred in the other sleep phenotypes. All the sleep phenotypes, except the primary form of ADHD and those related to focal benign epilepsy or focal EEG discharges, are associated with an increased level of arousal during sleep. Recent studies have demonstrated that both an increase and a decrease in arousal are ascribable to executive dysfunctions controlled by prefrontal cortical regions (the main cortical areas implicated in the pathogenesis of ADHD), and that the arousal system, which may be hyperactivated or hypoactivated depending on the form of ADHD/sleep phenotype.

Polysomnographic assessment of sleep disturbances in children with developmental disabilities and seizures

The aim of this study was to assess the presence of sleep breathing disorder and periodic leg movements during sleep (PLMS), and to evaluate NREM sleep instability in a group of children with mental retardation (MR) and epilepsy. Eleven subjects with MR and epilepsy (6 males, age range 9-17 years) were recruited for this study. A control group was formed by 11 age-matched normal children. Three children with MR and epilepsy showed an apnea-hypopnea index > 5, two of them had also a PLMS index > 5. Another subject had only a PLMS index > 5. Children with MR showed many sleep architecture differences compared to controls. They also showed higher cyclic alternating pattern (CAP) rate, increased A1 index, long and less numerous CAP sequences than controls. A detailed investigation and treatment of sleep disorders in children affected by MR and epilepsy may have a positive impact on seizure control.

Reduced NREM sleep instability in benign childhood epilepsy with centro-temporal spikes

OBJECTIVE

To analyze sleep architecture and NREM sleep instability by means of the cyclic alternating pattern (CAP) in children with benign epilepsy with rolandic spikes (BERS).

METHODS

Ten children with BERS, drug free at the time of the study and 10 age-matched normal controls were included in this study. Sleep was visually scored for sleep architecture and CAP using standard criteria.

RESULTS

Sleep architecture in BERS showed only few significant differences vs. controls with a reduction of total sleep time, sleep efficiency, and REM sleep percentage. CAP analysis revealed several significant differences: reduced total CAP rate, mainly in sleep stage 2, and reduced EEG slow oscillations and arousals during stages N1 and N2.

CONCLUSIONS

Sleep architecture is not importantly affected in BERS but CAP analysis reveals a decrease of NREM instability, mainly in sleep stage 2. Since there is a spindle-related spike activation in BERS, we speculate that the decrease of CAP and of EEG slow oscillations and arousals might be linked with the inhibitory action of spindling activity and spikes on arousals.

SIGNIFICANCE

CAP analysis discloses sleep structure abnormalities in children with BERS not shown by the classical sleep scoring. Spike activity and CAP A1 subtypes seem to be mutually exclusive probably because centro-temporal spikes disturb the physiological synchronization mechanisms needed for the generation of slow-wave components of CAP.

Epileptic discharges and phasic sleep phenomena in patients with juvenile myoclonic epilepsy

PURPOSE

Epileptiform discharges (EDs) may be part of the internal arousing stimuli that affect the quality of sleep in patients with epilepsies. We studied the association between EDs and sleep phasic phenomena, and its relevance to seizure control in 19 patients with juvenile myoclonic epilepsy (JME).

METHODS

We analyzed the first cycle of non-REM (rapid eye movement) sleep in 22 sleep-deprived electroencephalography (EEG) studies and classified EDs within the cyclical alternating pattern (CAP) frame, grouping separately the EDs that occurred at the transition between phases (B to A and A to B).

RESULTS

Within CAP periods, 36.7% of EDs occurred in A phase, 26.7% in B phase, 31.5% at "B to A" transition, and 3% at "A to B" transition. Poor seizure control was strongly associated with increased EDs in phase B (p = 0.0016) and at the "B to A" transition (p = 0.002), but marginally with increased EDs in phase A (p = 0.03). Focal spikes were increased in phase B.

DISCUSSION

EDs are facilitated by increased vigilance (A phase), but they may also enhance CAP cycling by generating A phases when those that occur at the "B to A" transition are interpreted as successfully breaking through the state of reduced arousal (phase B) because of increased epileptic pressure. This promotes sleep instability and further fosters epileptic activity, and conceivably seizures. This hypothesis is also supported by the strong correlation between EDs during phase B (including "B" and "B to A") and poor seizure control. The enhanced nonlocalizing focal spikes in phase B may reflect successful inhibition of generalized EDs.

Prevalence of EEG paroxysmal activity in a population of children with obstructive sleep apnea syndrome

STUDY OBJECTIVES

Sleep breathing disorders may trigger paroxysmal events during sleep such as parasomnias and may exacerbate preexisting seizures. We verified the hypothesis that the amount of EEG paroxysmal activity (PA) may be high in children with obstructive sleep apnea syndrome (OSAS).

DESIGN

Prospective study.

SETTINGS

Sleep unit of an academic center.

PARTICIPANTS

Polysomnographic studies were performed in a population of children recruited prospectively, for suspected OSAS, from January to December 2007, with no previous history of epileptic seizures or any other medical conditions. All sleep studies included > or = 8 EEG channels, including centrotemporal leads. We collected data about clinical and respiratory parameters of children with OSAS and with primary snoring, then we performed sleep microstructure analysis in 2 OSAS subgroups, matched for age and sex, with and without paroxysmal activity.

MEASUREMENTS AND RESULTS

We found 40 children who met the criteria for primary snoring, none of them showed PA, while 127 children met the criteria for OSAS and 18 of them (14.2%) showed PA. Children with PA were older, had a predominance of boys, a longer duration of OSAS, and a lower percentage of adenotonsillar hypertrophy than children without PA. Moreover, PA occurred over the centrotemporal regions in 9 cases, over temporal-occipital regions in 5, and over frontocentral regions in 4. Children with PA showed a lower percentage of REM sleep, a lower CAP rate and lower A1 index during slow wave sleep, and lower total A2 and arousal index than children without EEG abnormalities.

CONCLUSIONS

We found a higher percentage of paroxysmal activity in children with OSAS, compared to children with primary snoring, who did not exhibit EEG abnormalities. The children with paroxysmal activity have peculiar clinical and sleep microstructure characteristics that may have implications in the neurocognitive outcome of OSAS.

CAP, epilepsy and motor events during sleep: the unifying role of arousal

Arousal systems play a topical neurophysiologic role in protecting and tailoring sleep duration and depth. When they appear in NREM sleep, arousal responses are not limited to a single EEG pattern but are part of a continuous spectrum of EEG modifications ranging from high-voltage slow rhythms to low amplitude fast activities. The hierarchic features of arousal responses are reflected in the phase A subtypes of CAP (cyclic alternating pattern) including both slow arousals (dominated by the <1Hz oscillation) and fast arousals (ASDA arousals). CAP is an infraslow oscillation with a periodicity of 20-40s that participates in the dynamic organization of sleep and in the activation of motor events. Physiologic, paraphysiologic and pathologic motor activities during NREM sleep are always associated with a stereotyped arousal pattern characterized by an initial increase in EEG delta power and heart rate, followed by a progressive activation of faster EEG frequencies. These findings suggest that motor patterns are already written in the brain codes (central pattern generators) embraced with an automatic sequence of EEG-vegetative events, but require a certain degree of activation (arousal) to become visibly apparent. Arousal can appear either spontaneously or be elicited by internal (epileptic burst) or external (noise, respiratory disturbance) stimuli. Whether the outcome is a physiologic movement, a muscle jerk or a major epileptic attack will depend on a number of ongoing factors (sleep stage, delta power, neuro-motor network) but all events share the common trait of arousal-activated phenomena.

Sleep and epilepsy: what we know, don't know, and need to know

Long-term video-EEG and, more recently, video-polysomnography, have provided the means to confirm and expand on the interconnections between sleep and epilepsy. Some of these relationships have become firmly established. When one of the authors (N.F.S.) presented part of this paper at a symposium on the Future of Sleep in Neurology at an American Clinical Neurophysiology Society annual meeting in 2004, the purpose was to summarize what we know, don't know, and need to know about the effects of sleep on epilepsy and epilepsy on sleep. Here we seek to summarize some of the more firmly established relationships between sleep and epilepsy and identify intriguing associations that require further elucidation.

Parasomnias in childhood

Pediatric parasomnias comprise a wide variety of often confusing behaviors during sleep. This article discusses the classification, differential diagnosis, and evaluation of some of the most common pediatric parasomnias. The characteristics that distinguish different parasomnias from more serious medical problems are addressed carefully. Treatment strategies with useful caveats are reviewed.

Spike-wave discharge and the microstructure of sleep-wake continuum in idiopathic generalised epilepsy

This review summarises all the evidences about the influence of different vigilance states on the occurrence of spike wave discharge (SWD) in idiopathic generalised epilepsy (IGE) patients. Numerous converging observations showed that full REM-sleep and alert wakefulness exert strong inhibition. A critical zone of vigilance which is a transitional state between waking and non-REM (NREM) sleep, and NREM sleep and REM sleep, has a promoting effect on the absence type spike wave discharge. Spike wave discharges are associated with phasic arousals without awakening and are attached to oscillation son the microstructural level of sleep, perpetuated by cyclic arousal events known as 'cyclic alternating pattern' (CAP), especially within the critical zone, but also along the whole sleep process. More specifically SWD seems to be attached to the 'A-phase' of CAP which is a reactive one and reflects synchronised NREM sleep EEG elements, like K-complexes, spindles and delta groups. The more slow wave elements are found in phase A--like in subtype A1--the more the coincidence with SWD occurs, and the more it is characterised by fast rhythms--as in subtype A2 and A3--the less the association with SWD could be observed. Since subtype A1 is associated with the first sleep cycle and with the descending branches of cycles, it is concluded that SWD appear in those dynamic moments of vigilance level oscillations which were characterised by strong sleep-like answers to arousal influences in high sleep pressure periods of sleep cyclicity. These data harmonize with another line of evidence suggesting that SWD represent the epileptic variant of the complex thalamocortical system function which is the substrate of NREM sleep EEG phenomena. In idiopathic generalised epilepsy there is a growing body of evidence that--as it was assumed by Gloor--spindles transform to SWD pattern. These data explain why those dynamic changes which evoke sleep responses are promoting for the occurrence of SWD. Adapting these data we offer a new interpretation to explain the strong activation effect of sleep deprivation in this kind of epilepsy. We assume that it is mainly due to the forced vigilance level oscillations, especially in morning, when elevated sleep pressure and circadian wake promoting forces, representing opposite tendencies, increase the amount of oscillations.