Memory consolidation in children with epilepsy: Does sleep matter?

IntroductionChildren with epilepsy have frequent sleep disturbance and challenges in learning and memory. There is little research on the consolidation of memory during sleep in this population. The goal of this pilot study was to determine whether children with epilepsy are able to consolidate memories better after a sleep versus wake period as has been demonstrated in typically developing children.MethodsThis study was a prospective evaluation of children with epilepsy to determine if sleep improved episodic memory (using word lists) as compared with memory following a wake period of similar duration. The study was conducted in patients in the Epilepsy Monitoring Unit at a single academic health science center. In the sleep recall condition, the learning trials were presented in the evening, and delayed recall of the words was tested in the morning. In the wake condition, the learning took place in the morning, and the delayed recall took place later in the day. Subjects wore an actigraph to evaluate sleep/wake patterns. Data regarding the children's epilepsy, antiepileptic medications, and frequency of interictal epileptiform discharges were also documented.ResultsTen children (agd 8–17 years) participated in the study. For the entire sample, recall after sleep was better than recall after awake (p = 0.03), and 7 of the 10 children showed this effect. However, reanalyses removing an outlier showed no difference between the two recall conditions. The mean number of interictal epileptiform discharges was 8.8 during the recall after sleep and 7.8 during the recall after awake. Three children had seizures during the evaluation.ConclusionIn this pilot study, we demonstrated that a small cohort of children with epilepsy, with similar interictal epileptiform discharges during sleep and wake, showed no advantage in memory for a word list after a period of sleep than after a period of being awake. This finding requires further study in a larger cohort. Poor memory consolidation during sleep may contribute to the cognitive deficits in children with epilepsy.     

A reduction of sleep spindles heralds seizures in focal epilepsy

ObjectivesSleep has profound effects on epilepsy. It may alter the occurrence of interictal discharges (IEDs) and seizures. Vice versa, an active epilepsy changes sleep. Sleep spindles are typically associated with an increase of IEDs. We examined whether seizures change the number and power of spindles preceding nightly seizures.MethodsWe retrospectively examined the nightly EEG recordings of presurgical epilepsy patients from our EEG-video-monitoring unit. We evaluated the 200 s before the EEG seizure onset for spindle density (spindles per minute) and spindle power and compared that to the interictal baseline sleep.ResultsThe spindle density and the spindle power decreased significantly before the first seizure. The reduction before secondarily generalized seizures (8.7 ± 2.5; p = 0.001) was more pronounced than before focal seizures (10.5 ± 2.5; p = 0.003) compared to baseline (12.2 ± 2.7). This finding was more pronounced in extratemporal lobe epilepsies than in temporal lobe epilepsies. The reduction of spindle power was also significant and was more pronounced in XTLE. These results were consistent for all other seizures during sleep, the mean spindle density decreased significantly in all focal (10.2 ± 1.9; p = 0.001) and generalized preictal period (8.8 ± 2.4; p = 0.001) compared to the mean interictal period (12.1 ± 2.1). These were also more significant in XTLE than TLE group.ConclusionsOur data demonstrate that the occurrence of seizures and propensity of seizure generalisation in focal epilepsy is modulated by specific characteristics of light sleep such as sleep spindles.SignificanceThis study supports the notion that changes in the epileptic network precede the seizure onset and have an influence on seizure generation and termination.     

Spontaneous ripples in the hippocampus correlate with epileptogenicity and not memory function in patients with refractory epilepsy

IntroductionHigh-frequency oscillations (HFOs, 80–500 Hz) are newly-described EEG markers of epileptogenicity. The proportion of physiological and pathological HFOs is unclear, as frequency analysis is insufficient for separating the two types of events. For instance, ripples (80–250 Hz) also occur physiologically during memory consolidation processes in medial temporal lobe structures. We investigated the correlation between HFO rates and memory performance.MethodsPatients investigated with bilateral medial temporal electrodes and an intellectual capacity allowing for memory testing were included. High-frequency oscillations were visually marked, and rates of HFOs were calculated for each channel during slow-wave sleep. Patients underwent three verbal and three nonverbal memory tests. They were grouped into severe impairment, some impairment, mostly intact, or intact for verbal and nonverbal memory. We calculated a Pearson correlation between HFO rates in the hippocampi and the memory category and compared HFO rates in each hippocampus with the corresponding (verbal — left, nonverbal — right) memory result using Wilcoxon rank-sum test.ResultsTwenty patients were included; ten had bilateral, five had unilateral, and five had no memory impairment. Unilateral memory impairment was verbal in one patient and nonverbal in four. There was no correlation between HFO rates and memory performance in seizure onset areas. There was, however, a significant negative correlation between the overall memory performance and ripple rates (r = − 0.50, p = 0.03) outside the seizure onset zone.ConclusionOur results suggest that the majority of spontaneous hippocampal ripples, as defined in the present study, may reflect pathological activity, taking into account the association with memory impairment. The absence of negative correlation between memory performance and HFO rates in seizure onset areas could be explained by HFO rates in the SOZ being generally so high that differences between areas with remaining and impaired memory function cannot be seen.     

Multiple sleep latency measures in narcolepsy and behaviourally induced insufficient sleep syndrome

BackgroundShort mean latencies to the first epoch of non-rapid eye movement sleep stage 1 (NREM1) and the presence of ?2 sleep onset REM (SOREM) periods on multiple sleep latency test (MSLT) occur in both narcolepsy–cataplexy (NC) and behaviourally induced insufficient sleep syndrome (BIISS). It is not known whether specific MSLT findings help differentiate the two disorders.MethodsWe analyzed MSLT data including sleep latencies to and between different sleep stages of 60 age-, gender- and body mass index (BMI)-matched subjects (hypocretin-deficient NC, actigraphy-confirmed BIISS, healthy controls: each 20).ResultsMean latency (in minutes) to NREM1 sleep was significantly shorter in NC (1.8 ± 1.5) than in BIISS (4.7 ± 2.1, p < 0.001) and controls (11.4 ± 3.3, p < 0.001). Mean latency to NREM2 sleep was similar in NC (8.6 ± 4.7) and BIISS (8.1 ± 2.7, p = 0.64); latency to either NREM2 or rapid eye movement (REM) sleep (i.e., the sum of the sleep latency to NREM1 and the duration of the first NREM1 sleep sequence), however, was shorter in NC (4.4 ± 2.9) than in BIISS (7.9 ± 3.5, p < 0.001). Referring to all naps with SOREM periods, the sequence NREM1–REM–NREM2 was more common (71%) in NC than in BIISS (15%, p < 0.001), reflecting the shorter latency from NREM1 to NREM2 in BIISS (3.7 ± 2.5) than in NC (6.1 ± 5.9, p < 0.001).ConclusionsOur findings show that both sleepiness (as measured by NREM1 sleep latency) and REM sleep propensity are higher in NC than in BIISS. Furthermore, our finding of frequent REM sleep prior to NREM2 sleep in NC is in line with the recent assumption of an insufficient NREM sleep intensity in NC. Together with detailed clinical interviews, sleep logs, actigraphy, and nocturnal polysomnography, mean sleep latencies to NREM1 ?2.5 min, the presence of multiple SOREM periods, and the sequence NREM1–REM–NREM2 may be the best MSLT measures to discriminate NC from BIISS.     

Paroxysmal activity and seizures associated with sleep breathing disorder in children: A possible overlap between diurnal and nocturnal symptoms

PurposeSleep breathing disorders (SBD) can trigger paroxysmal events. We recently found a higher percentage of paroxysmal activity (PA) in a sample of Italian children with obstructive sleep apnea syndrome (OSAS) and no history of epilepsy. The signs of nocturnal seizures can overlap with sleep respiratory events. The aim of this study was to confirm the high frequency of PA or interictal epileptiform discharges (IEDs) during sleep in a cohort of Spanish children who underwent polysomonography (PSG) for suspected SBD and to ascertain the eventual presence of seizures by means of a video-PSG with an extended electroencephalogram (EEG).MethodsPSG was performed in a population of children with no previous history of epileptic seizures recruited prospectively for suspected OSAS from January to December 2007. Recordings included at least 13 EEG channels.ResultsIn total, 25 children (mean age, 6.6 ± 3.8 years, 14 males) were diagnosed with SBD, and 4/25 (16%) children met the criteria for OSAS and epilepsy, with IEDs and/or seizures during sleep. We diagnosed benign epilepsy with centro-temporal spikes in 2 cases, partial symptomatic epilepsy in one, and nocturnal frontal lobe epilepsy in another, while we found PA in 2 patients. The body mass index and the apnea–hypopnea index were significantly higher in children without IEDs/PA.ConclusionsOur study demonstrated a close relationship between pediatric SBD, PA during sleep, and epilepsy that may aggravate the prognosis of SBD. Due to the possibility of an overlap of symptoms, a video-PSG with extended EEG montage is necessary.     

Interictal epileptic discharge correlates with global and frontal cognitive dysfunction in temporal lobe epilepsy

ObjectiveTemporal lobe epilepsy (TLE) with hippocampal sclerosis has widespread effects on structural and functional connectivity and often entails cognitive dysfunction. EEG is mandatory to disentangle interactions in epileptic and physiological networks which underlie these cognitive comorbidities. Here, we examined how interictal epileptic discharges (IEDs) affect cognitive performance.MethodsThirty-four patients (right TLE = 17, left TLE = 17) were examined with 24-hour video-EEG and a battery of neuropsychological tests to measure intelligence quotient and separate frontal and temporal lobe functions. Hippocampal segmentation of high-resolution T1-weighted imaging was performed with FreeSurfer. Partial correlations were used to compare the number and distribution of clinical interictal spikes and sharp waves with data from imagery and psychological tests.ResultsThe number of IEDs was negatively correlated with executive functions, including verbal fluency and intelligence quotient (IQ). Interictal epileptic discharge affected cognitive function in patients with left and right TLE differentially, with verbal fluency strongly related to temporofrontal spiking. In contrast, IEDs had no clear effects on memory functions after corrections with partial correlations for age, age at disease onset, disease duration, and hippocampal volume.ConclusionIn patients with TLE of long duration, IED occurrence was strongly related to cognitive deficits, most pronounced for frontal lobe function. These data suggest that IEDs reflect dysfunctional brain circuitry and may serve as an independent biomarker for cognitive comorbidity.     

Nocturnal autonomic function in preschool children with sleep-disordered breathing

BackgroundObstructive sleep apnea (OSA) is associated with autonomic dysfunction in adults and school-aged children; however, this association has not been investigated in preschool children. We aimed to analyze heart rate variability (HRV) and catecholamine levels in preschool children with OSA.MethodsOne hundred and forty-two snoring children aged 3–5 years and 38 nonsnoring control group children underwent overnight polysomnography (PSG). Nocturnal urinary catecholamines were measured in 120 children. Children were grouped according to their obstructive apnea–hypopnea index (OAHI) (control [no snoring], OAHI ⩽ 1 event/h; primary snoring, OAHI ⩽ 1 event/h; mild OSA OAHI > 1 ⩽ 5 events/h; moderate to severe [MS] OSA, OAHI > 5 events/h). The HRV parameters for each child were averaged during rapid eye movement (REM) and non-REM (NREM) sleep.ResultsDuring stable sleep, low-frequency (LF) HRV was similar between groups. High-frequency (HF) HRV was higher in the MS OSA group compared with the control group during all sleep stages (NREM sleep stages 1 and 2 [NREM1/2], 4234 ± 523 ms² vs 2604 ± 457 ms²; NREM sleep stages 3 and 4 [NREM3/4], 4152 ± 741 ms² vs 3035 ± 647 ms²; REM, 1836 ± 255 ms² vs 1456 ± 292 ms²; P < .01 for all). The LF/HF ratio was lower in the MS OSA group compared with the control group (NREM1/2, 0.4 ± 0.06 vs 0.7 ± 0.05; NREM3/4, 0.3 ± 0.06 vs 0.4 ± 0.05; REM, 0.8 ± 0.1 vs 1.3 ± 0.1; P < .01 for all). Catecholamine levels were not different between groups.ConclusionsIn preschool children, OSA is associated with altered HRV, largely due to the HF fluctuations in heart rate (HR) which occur during respiratory events and are still evident during stable sleep. The preschool age may represent a window of opportunity for treatment of OSA before the onset of the severe autonomic dysfunction associated with OSA in adults and older children.     

Effects of long-term use of clonazepam on nonrapid eye movement sleep patterns in rapid eye movement sleep behavior disorder

ObjectiveWe aim to analyze in detail the characteristics of nonrapid eye movement (NREM) sleep in drug-free patients with idiopathic rapid eye movement sleep behavior disorder (iRBD). We compare drug-free iRBD patients to both normal controls and drug-free patients with narcolepsy/RBD and evaluate the changes following the long-term use of bedtime clonazepam.Participants and methodsForty-six participants were recruited: 15 with iRBD (13 men, 2 women; mean age, 65.8 ± 4.39 years), 13 with narcolepsy/RBD (10 men, 3 women; mean age, 63.0 ± 6.73 years), and 18 normal controls (10 men, 8 women; mean age 69.4 ± 7.72 years). Sleep was video polysomnographically recorded and the RBD severity scale (RBDSS) was obtained. Chin electromyography (EMG) amplitude was quantitatively assessed and the atonia index was computed. Additionally, NREM sleep instability was evaluated using an automatic quantitative analysis. Participants with iRBD were re-evaluated after 2.75 ± 1.62 years of regular therapy with 0.5 to 1-mg clonazepam at bedtime.ResultsSlow transient electroencephalography (EEG) events were increased in iRBD and decreased in narcolepsy/RBD, while fast transient events decreased in iRBD and increased in narcolepsy/RBD. During rapid eye movement (REM) sleep the atonia index was reduced in both iRBD and narcolepsy/RBD groups and during NREM sleep atonia index was increased in iRBD participants, remaining low in narcolepsy/RBD participants. After long-term therapy with clonazepam, wakefulness after sleep onset was decreased together with an increase in both slow-wave sleep (SWS) and sleep stage 2, in which the latter reached statistical significance; sleep stages 1 and 2 instability significantly decreased and the duration of EEG transients also slightly but significantly decreased. Finally, chin tone was not modified by clonazepam.ConclusionsOur study confirms that clonazepam modifies some aspects of NREM sleep in iRBD participants with a decrease in its instability. Moreover, we also show that a complex modification of sleep chin atonia exists in these participants, which also involves NREM sleep; for iRBD more complex neuropathologic models encompassing REM sleep and NREM sleep mechanisms are needed.     

Sleep-disordered breathing does not affect nocturnal dipping,as assessed by pulse transit time,in preschool children: evidence for early intervention to prevent adverse cardiovascular effects?

ObjectiveSleep-disordered breathing (SDB) is associated with reduced nocturnal dipping of blood pressure (BP) and sleep disruption in adults, and these features confer an increased risk of cardiovascular events. As SDB prevalence in children peaks during the preschool years, we investigated nocturnal dipping and sleep fragmentation in preschool children with SDB.MethodsChildren (3–5 years; n = 163) grouped by obstructive apnoea hypopnoea index (OAHI): control, no snoring history and OAHI ⩽1 event/h; primary snoring, OAHI ⩽1 event/h; mild SDB, >1–⩽5 events/h; moderate–severe SDB, >5 events/h. Pulse transit time (PTT), an inverse continuous indicator of BP changes, and heart rate (HR) during total sleep time and the first period of rapid eye movement (REM), non-REM (NREM)1/2 and NREM3/4 sleep were expressed as percentage change from wake before sleep onset. The sleep fragmentation index (SFI) was calculated as the number of sleep stage transitions or awakenings per hour of sleep.ResultsThere were no group differences in the change in PTT or HR from wake to total sleep time or to individual sleep stages or in the proportion of children in the quartile with the smallest change in PTT during total sleep. Children with moderate–severe SDB had higher SFI than primary snoring (PS) or mild SDB groups (p < 0.05 for both) and controls (p = 0.07).ConclusionsIn contrast to adults, nocturnal dipping is preserved in young children with SDB, despite increased sleep fragmentation. As there is evidence that nocturnal dipping is similarly preserved at the school age, childhood may pose a window of opportunity for resolution of SDB when the cardiovascular effects are less marked.     

A preliminary study of slow-wave EEG activity and insulin sensitivity in adolescents

ObjectiveThe objective was to evaluate the relationship between the time course of slow wave EEG activity (SWA) during NREM sleep and insulin sensitivity in adolescents.MethodsNine normal weight and nine overweight (BMI > 85th percentile) adolescents (13–18 years of age) participated. None of the participants had a history of sleep disordered breathing, confirmed by sleep study. Participants maintained a regularized sleep wake cycle for five days followed by overnight polysomnography in the lab or at home. An oral glucose tolerance test (OGTT) was administered after a 12 h fast and within two weeks of the sleep study. Whole body insulin sensitivity (WBISI) and homeostasis model assessment (HOMA-IR) determined insulin resistance. Power spectral analysis quantified slow-wave EEG activity (.05–3.9 Hz) and exponential regression evaluated SWA across successive NREM periods.ResultsThose who were insulin resistant and had low insulin sensitivity had less Stages 2, 3 and 4 of NREM sleep, more Stage 1, but did not sleep less than those with low resistance and high sensitivity. SWA power was significantly lower in the first NREM period and the decay rate of SWA across NREM sleep was significantly slower in the low insulin sensitivity group. Similar results were obtained after removing the influence of BMI and Tanner score.ConclusionsInsulin sensitivity in adolescents is related to SWA power and its time course, not total sleep time, regardless of BMI.     

Vagus nerve stimulation: Outcome and predictors of seizure freedom in long-term follow-up

ObjectivesTo present long-term outcome and to identify predictors of seizure freedom after vagus nerve stimulation (VNS).MethodsAll patients who had undergone VNS implantation in the Epilepsy Centre Bethel were retrospectively reviewed. There were 144 patients who had undergone complete presurgical evaluation, including detailed clinical history, magnetic resonance imaging, and long-term video-EEG with ictal and interictal recordings. After implantation, all patients were examined at regular intervals of 4 weeks for 6–9 months. During this period the antiepileptic medication remained constant. All patients included in this study were followed up for a minimum of 2 years.ResultTen patients remained seizure-free for more than 1 year after VNS implantation (6.9%). Seizures improved in 89 patients (61.8%) but no changes were observed in 45 patients (31.3%). The following factors were significant in the univariate analysis: age at implantation, multifocal interictal epileptiform discharges, unilateral interictal epileptiform discharge, cortical dysgenesis, and psychomotor seizure. Stepwise multivariate analysis showed that unilateral interictal epileptiform discharges (IEDs), P = 0.014, HR = 0.112 (95% CIs, 0.019–0.642), cortical dysgenesis P = 0.007, HR = 0.065 (95% CIs, 0.009–0.481) and younger age at implantation P = 0.026, HR = 7.533 (95% CIs 1.28–44.50) were independent predictors of seizure freedom in the long-term follow-up.ConclusionVNS implantation may render patients with some forms of cortical dysgenesis (parietooccipital polymicrogyria, macrogyria) seizure-free. Patients with unilateral IEDs and earlier implantation achieved the most benefit from VNS.     

Do sphenoidal electrodes aid in surgical decision making in drug resistant temporal lobe epilepsy?

ObjectiveThe utility of sphenoidal electrodes (SPh) in analyzing interictal epileptiform discharges (IEDs) and ictal electrography remains controversial, despite its widespread use.MethodsOne hundred and twenty-two consecutive patients with presumed temporal lobe epilepsy (TLE) who underwent presurgical evaluation were prospectively studied. SPh and Silverman’s electrodes were placed, in addition to routine electrodes in 10–20 international system. IEDs and ictal electroencephalography (EEG) were analyzed separately in bipolar and referential montages. The proportion of patients selected for surgery after adjusting for SPh placement based on the earlier ictal onset and IEDs were analyzed.ResultsOf the 8701 IEDs in SPh, only 65% were seen over the scalp bipolar montage; 1392 (16%) IEDs were confined to SPh electrodes, and were not seen at scalp bipolar montage (p < 0.001). Spike amplitudes were highest at SPh (p < 0.001). Of the 592 seizures analyzed, 62 (61%) had simultaneous SPh and scalp onset, while in 26 (25%) SPh onset preceded the scalp.ConclusionsOut of the 35 patients with unilateral mesial temporal sclerosis (MTS) with additional neocortical changes and/or non-lateralized bitemporal IEDs and/or diffuse ictal onset (group 1), 27 were selected for surgery (77%). About 7% was selected for surgery in this group by SPh placement. Also, in patients with bilateral MTS (group 2), 25% (5/20) were chosen for anterior temporal lobectomy, SPh provided an additional benefit in 11% (p < 0.001). Patients with normal magnetic resonance imaging (group 3) and temporal plus epilepsy (group 4) had a lower surgical yield, only 12% and 9.5% could undergo surgery. They were denied surgical candidacy with SPh (p < 0.001).SignificanceOne-third of patients after SPh placement were selected for resective surgery obviating the need for invasive monitoring. The maximum yield was noted in unilateral MTS (associated with additional neocortical features or non-lateralized bilateral temporal interictal IEDs or diffuse ictal onset in scalp EEG) and in bilateral MTS. Those with normal MRI/temporal plus epilepsy could be excluded from direct resective surgery.     

Sleep architecture in school-aged children with primary snoring

ObjectiveWe aimed to examine if sleep architecture was altered in school-aged children with primary snoring (PS).MethodsChildren ages 6 to 13 years from 13 primary schools were randomly recruited. A validated obstructive sleep apnea (OSA) screening questionnaire was completed by their parents. Children at high risk for OSA and a randomly chosen low-risk group were invited to undergo overnight polysomnography (PSG) and clinical examination. Participants were classified into healthy controls, PS, mild OSA, and moderate to severe OSA (MS OSA) groups for comparison.ResultsA total of 619 participants underwent PSG (mean age, 10.0 ± 1.8 years; 396 (64.0%) boys; 524 (84.7%) prepubertal). For the cohort as a whole, there were no significant differences in measures of sleep architecture between PS and nonsnoring healthy controls. In the multiple regression model, percentage of nonrapid eye movement (NREM) stage 1 (N1) sleep had a significantly positive association, whereas percentage of slow-wave sleep (SWS) had a significantly negative association with sleep-disordered breathing (SDB) severity after controlling for age, gender, body mass index (BMI) z score, and pubertal status. In prepubertal children with PS, no significant disruption of sleep architecture was found. However, pubertal adolescent PS participants had significantly higher adjusted percentage of N1 sleep and wake after sleep onset (WASO) compared to healthy controls.ConclusionsPS did not exert significant adverse influences on normal sleep architecture in prepubertal school-aged children. Nevertheless, pubertal adolescents with PS had increased N1 sleep and WASO.     

Can an early 24-hour EEG predict the response to the ketogenic diet? A prospective study in 34 children and adults with refractory epilepsy treated with the ketogenic diet

PurposeWe examined whether early EEG changes in a 24-h EEG at 6 weeks of treatment were related to the later clinical response to the ketogenic diet (KD) in a 6-month period of treatment.MethodsWe examined 34 patients with heterogeneous epilepsy syndromes (21 children, 13 adults) and found 9 clinical responders (≥50% seizure reduction); this is a responder rate of 26%. We visually counted the interictal epileptic discharge index (IED index) in % during 2 h of wakefulness and in the first hour of sleep (method 1), and also globally reviewed EEG changes (method 2), while blinded to the effect of the KD.ResultsAt group level we saw a correlation between nocturnal reduction of IED-index at 6 weeks and seizure reduction in the follow-up period. A proportional reduction in IED index of 30% from baseline in the sleep EEG, was associated with being a responder to the diet (Pearson Chi-square p = 0.04). EEG scoring method 2 observed a significantly larger proportion of patients with EEG-improvement in sleep in KD responders than in non-responders (p = 0.03). At individual level, however, EEG changes did not correlate very strongly to the response to the diet, as IED reduction in sleep was also seen in 15% (method 1) to 26% (method 2) of the non-responders.ConclusionNocturnal reduction of IEDs is related to the response to the KD, however in daily clinical practice, an early EEG to predict seizure reduction should not be advised for individual patients.     

Let there be no light: the effect of bedside light on sleep quality and background electroencephalographic rhythms

ObjectivesArtificial lighting has been beneficial to society, but unnecessary light exposure at night may cause various health problems. We aimed to investigate how whole-night bedside light can affect sleep quality and brain activity.Patients and methodsTen healthy sleepers underwent two polysomnography (PSG) sessions, one with the lights off and one with the lights on. PSG variables related to sleep quality were extracted and compared between lights-off and lights-on sleep. Spectral analysis was performed to rapid eye movement (REM) sleep and non-REM (NREM) sleep epochs to reveal any light-induced differences in background brain rhythms.ResultsLights-on sleep was associated with increased stage 1 sleep (N1), decreased slow-wave sleep (SWS), and increased arousal index. Spectral analysis revealed that theta power (4–8 Hz) during REM sleep and slow oscillation (0.5–1 Hz), delta (1–4 Hz), and spindle (10–16 Hz) power during NREM sleep were decreased in lights-on sleep conditions.ConclusionsSleeping with the light on not only causes shallow sleep and frequent arousals but also has a persistent effect on brain oscillations, especially those implicated in sleep depth and stability. Our study demonstrates additional hazardous effect of light pollution on health.     

No Effects of Slow Oscillatory Transcranial Direct Current Stimulation (tDCS) on Sleep-Dependent Memory Consolidation in Healthy Elderly Subjects

BackgroundStudies in young healthy volunteers provided evidence of a beneficial impact of an anodal time-varied transcranial direct current stimulation (tDCS) during early slow wave rich sleep on declarative memory but not on procedural memory.Objective/hypothesisThe present study investigated whether sleep-dependent memory consolidation can also be affected by slow oscillating tDCS in a population of elderly subjects.Methods26 subjects (69.1 years ± 7.7 years) received bi-frontal anodal stimulation (max. current density: 0.331 mA/cm²) during early NREM sleep in a double-blind placebo-controlled randomized crossover study. Stimulation effects on offline consolidation were tested by using a declarative and a procedural memory task. Furthermore, sleep stages were scored, EEG power was analyzed and spindle densities were assessed.ResultsIndependently from stimulation condition, performance in both memory tasks significantly decreased overnight. Stimulation revealed no significant effect on sleep-dependent memory consolidation. Verum tDCS was accompanied by significantly more time awake and significantly less NREM stage 3 sleep during five 1-min stimulation free intervals.ConclusionsThe results of the present study are in line with other studies showing that offline consolidation during sleep varies with age and is less pronounced in the elderly than in young or middle-aged subjects. Contrary to an almost identical positive study in young adults, slow oscillatory tDCS applied to the elderly failed to show a beneficial effect on memory consolidation in the present study.     

A four year follow-up of sleep and respiratory measures in elementary school-aged children with sleep disordered breathing

ObjectiveLittle is known of the long-term prognosis of children treated for sleep disordered breathing (SDB) and even less of children with milder forms of SDB who remain untreated. We aimed to investigate the long-term sleep and respiratory outcomes of children with a range of SDB severities.Methods41 children with SDB and 20 non snoring controls (mean age, 12.9 ± 0.2 y), underwent repeat overnight polysomnography (PSG) 4.0 ± 0.3 years after initial diagnosis. SDB severity, presence of snoring, sleep and respiratory parameters, sleep fragmentation index (SFI), the Pediatric Daytime Sleepiness Scale (PDSS), Sleep Disturbance Scale for Children (SDSC), and obstructive sleep apnea 18-item quality of life questionnaire were re assessed. Children with SDB were grouped into resolved (no snoring and obstructive apnea–hypopnea index [OAHI] <1) and unresolved (snoring or an OAHI ⩾1).ResultsAt follow-up OAHI was reduced in both SDB groups (p < 0.05); however, 54% (n = 22) of children still continued to snore, having either persistent or new OSA (n = 4). In this unresolved group, sleep was significantly disrupted; % nonrapid eye movement stage 1 (NREM1) sleep and SFI were increased (p < 0.05), and total sleep time (TST) and sleep efficiency were decreased compared to the resolved and control groups (p < 0.05). Overall, 29% of children were treated, and of these, 67% had resolved SDB. SDB groups had higher PDSS, SDSC, and OSA-18 scores compared to controls at follow-up (p < 0.01).ConclusionsOur study demonstrated that although SDB improved in the long-term, more than 50% of children had residual SDB (mostly primary snoring) and sleep disturbance. As even mild forms of SDB are known to have adverse cardiovascular, learning, and behavioral outcomes, which have implications for the health of these children.     

Neuropsychological profile in new-onset benign epilepsy with centrotemporal spikes (BECTS): Focusing on executive functions

PurposeIncreased evidence of subnormal neuropsychological functioning in new-onset childhood epilepsy has been obtained, although results are still rare and controversial. With a prospective study, we aimed to define the very early neuropsychological profile of children with benign epilepsy with centrotemporal spikes (BECTS), including executive functions (EF) because of their key role in learning. Additionally, we enrolled drug-naïve children, with a NREM sleep frequency of discharges < 85% and with a Performance Intelligence Quotient equal or superior to 85, in order to exclude additional effects on the neuropsychological functioning.MethodsFifteen school-aged children with BECTS (mean age: 8.8 years, standard deviation [SD]: 2.4 years) and fifteen healthy children (mean age: 9.2 years, [SD]: 2.5 years) were enrolled and assessed with a comprehensive neuropsychological battery. The assessment included domain-specific standardized tests of language, EF, academic skills, visuomotor and visuospatial skills, and short-term memory. A p-value < 0.05 was considered significant.ResultsSignificant differences between patients and controls emerged with respect to 3 domains. Language was affected in color naming (p = .026), spoonerism (p = .003), and phonemic synthesis (p = .009). Executive functions appeared inadequate in the five point test with respect to the number of correct figures (p = .003) and errors (p = .008). In the domain of academic skills, significant differences between groups emerged regarding the number of mistakes in nonword writing (p = .001), nonword reading speed (p = .027), nonword reading number of mistakes (p = .019), and word reading errors (p = .023).DiscussionResults showed that children with new-onset BECTS may demonstrate a range of neuropsychological dysfunctions, particularly affecting executive attention, despite a normal IQ, a low frequency of NREM sleep discharges, and the absence of drugs. These difficulties indicate a frontal dysfunction with cascading effects on language and academic skills. The inclusion of EF in the assessment battery and in the intervention since the very onset is warranted in order to avoid further and persistent academic difficulties.     

Decreased sleep spindle density in patients with idiopathic REM sleep behavior disorder and patients with Parkinson’s disease

ObjectiveTo determine whether sleep spindles (SS) are potentially a biomarker for Parkinson’s disease (PD).MethodsFifteen PD patients with REM sleep behavior disorder (PD + RBD), 15 PD patients without RBD (PD − RBD), 15 idiopathic RBD (iRBD) patients and 15 age-matched controls underwent polysomnography (PSG). SS were scored in an extract of data from control subjects. An automatic SS detector using a Matching Pursuit (MP) algorithm and a Support Vector Machine (SVM) was developed and applied to the PSG recordings. The SS densities in N1, N2, N3, all NREM combined and REM sleep were obtained and evaluated across the groups.ResultsThe SS detector achieved a sensitivity of 84.7% and a specificity of 84.5%. At a significance level of α = 1%, the iRBD and PD + RBD patients had a significantly lower SS density than the control group in N2, N3 and all NREM stages combined. At a significance level of α = 5%, PD − RBD had a significantly lower SS density in N2 and all NREM stages combined.ConclusionsThe lower SS density suggests involvement in pre-thalamic fibers involved in SS generation. SS density is a potential early PD biomarker.SignificanceIt is likely that an automatic SS detector could be a supportive diagnostic tool in the evaluation of iRBD and PD patients.     

Effect of chronic vagal nerve stimulation on interictal epileptiform discharges

We evaluated the effect of vagus nerve stimulation (VNS) on interictal epileptiform discharges (IEDs) in 32 epileptic patients (18 females; 14 males) with an average age of 42.2 ± 11.4 years, all of whom had been suffering from epilepsy for an average of 29.2 ± 14.5 years. All of the patients had received VNS for 5 years. The first EEG was performed prior to the initiation of stimulation; the second EEG was performed at the 5-year follow-up visit. The duration of each EEG was 30 min. We compared these two EEGs in terms of the number of IEDs present in each patient and correlated them to other variables.The average total number of IEDs during EEG and the total number of seconds in which IEDs were present decreased significantly after 5 years of stimulation from 97.3 ± 106.9 resp. 80.6 ± 86.1 to 49.4 ± 94.0 resp. 37.8 ± 65.0. Although there was no positive correlation between the reduction of IEDs and the percent of seizure reduction, we found a greater decrease of IEDs in patients who responded to VNS in comparison to those who did not. The decrease of IEDs was more pronounced in patients suffering from temporal lobe epilepsy than in patients suffering from extratemporal epilepsy. No other significant correlations were found.VNS reduced IEDs in patients chronically simulated for epilepsy. The reduction of IEDs was greater in patients who responded to VNS and in patients suffering from temporal lobe epilepsy.