How do people with drug-resistant mesial temporal lobe epilepsy sleep? A clinical and video-EEG with EOG and submental EMG for sleep staging study

Rapid eye movement sleep and epilepsy: exploring interactions and therapeutic prospects

While research interest in the relationship between sleep and epilepsy is growing, it primarily centres on the effects of non-rapid eye movement (NREM) sleep in favouring seizures. Nonetheless, a noteworthy aspect is the observation that, in the lives of patients with epilepsy, REM sleep represents the moment with the least epileptic activity and the lowest probability of having a seizure. Studies demonstrate a suppressive effect of phasic REM sleep on interictal epileptiform discharges, potentially offering insights into epilepsy localisation and management. Furthermore, epilepsy impacts REM sleep, with successful treatment correlating with improved REM sleep quality. Novel therapeutic strategies aim to harness REM's anti-epileptic effects, including pharmacological approaches targeting orexinergic systems and neuromodulation techniques promoting cortical desynchronisation. These findings underscore the intricate relationship between REM sleep and epilepsy, highlighting avenues for further research and therapeutic innovation in epilepsy management.

The Relationship Between Sleep, Epilepsy, and Development: a Review

PURPOSE OF REVIEW

To review the relationship between sleep, neurodevelopment, and epilepsy and potential underlying physiological mechanisms.

RECENT FINDINGS

Recent studies have advanced our understanding of the role of sleep in early brain development and epilepsy. Epileptogenesis has been proposed to occur when there is a failure of normal adaptive processes of synaptic and homeostatic plasticity. This sleep-dependent transformation may explain the cognitive impairment seen in epilepsy, especially when occurring early in life. The glymphatic system, a recently discovered waste clearance system of the central nervous system, has been described as a potential mechanism underlying the relationship between sleep and seizures and may account for the common association between sleep deprivation and increased seizure risk. Epilepsy and associated sleep disturbances can critically affect brain development and neurocognition. Here we highlight recent findings on this topic and emphasize the importance of screening for sleep concerns in people with epilepsy.

Sleep macrostructure and cyclic alternating pattern in patients who underwent surgery for hippocampal sclerosis: A prospective controlled polysomnographic study

INTRODUCTION

Temporal lobe epilepsy due to hippocampal sclerosis (TLE-HS) is one of the most common drug-resistant epilepsy. Surgery is currently accepted as an effective and safe therapeutic approach compared to antiseizure medications (ASMs). The study aims to evaluate the effect of surgical treatment of TLE-HS on sleep profile and architecture by subjective and objective evaluation of sleep in basal condition after one month and one year.

METHODS

Thirteen patients with TLE-HS were recruited to undergo overnight polysomnography and a subjective evaluation of nocturnal sleep utilizing the Pittsburgh Sleep Quality Index (PSQI) and daytime somnolence through the Epworth Sleepiness Scale (ESS) in basal condition (T0), one month (T1) and one year after surgery (T2), respectively. Thirteen healthy controls (HC) matched for age, sex and BMI were recruited. Scoring and analysis of sleep macrostructure and cyclic alternating pattern (CAP) parameters were performed.

RESULTS

The comparison between patients in basal condition (T0) and HC showed a significant lower sleep efficiency (p = 0.003) and REM percentage (p < 0.001). Regarding CAP, patients at T0 showed higher total CAP rate (p < 0.001), CAP rate in N2 (p < 0.001), higher A3 (%) (p = 0.001), higher mean duration of A1 (p = 0.002), A3 index (p < 0.001), cycle in sequences (p < 0.001), lower B duration (p < 0.001), cycle mean duration (p < 0.001) than HC. Surgery did not induce significant changes in nocturnal macrostructural polysomnographic variables in T1 and T2. Lower CAP rate (T1 vs T0 and T2 vs T0 p < 0.001), CAP rate in N3 (T1 vs T0 and T2 vs T0 p < 0.001), A3 (%) (T1 vs T0 and T2 vs T0 p < 0.001); lower phase A2 index (T1 vs T0 p < 0.001) and A3 index (T1 vs T0 p < 0.001), lower phase A1 index (T2 vs T0 p < 0.001) and cycle in sequences (T2 vs T0 p = 0.002) higher B mean duration (T2 vs T0 p = 0.002). No significant differences were found between T1 and T2 in CAP parameters.

CONCLUSION

We found a significant NREM sleep instability in patients with TLE-HS compared with HC. In addition, anterior temporal lobectomy (ATL) induced a significant improvement in sleep continuity as evaluated by cyclic alternating pattern already one month later and this effect persisted after one year. ALT seems to restore a more resilient sleeping brain.

Interictal epileptiform discharges show distinct spatiotemporal and morphological patterns across wake and sleep

Presurgical evaluation of mesial temporal and neocortical focal pharmacoresistant epilepsy patients using intracranial EEG recordings has led to the generation of extensive data on interictal epileptiform discharges, located within or remotely from seizure onset zones. In this study, we used this data to investigate how interictal epileptiform discharges are modulated and how their spatial distribution changes during wake and sleep and analysed the relationship between these discharge events and seizure onset zones. Preoperative evaluation data from 11 adult patients with focal pharmacoresistant epilepsy were extracted from the Epilepsiae database. Interictal epileptiform discharges were automatically detected during wakefulness and over several hours of continuous seizure-free sleep (total duration of EEG recordings:106.7 h; mean per patient: 9.7 h), and analysed across four brain areas (mesial temporal, lateral neocortical, basal cortical and the temporal pole). Sleep stages were classified manually from scalp EEG. Discharge events were characterized according to their rate and morphology (amplitude, sharpness and duration). Eight patients had a seizure onset zone over mesial areas and three patients over lateral neocortical areas. Overall, discharge rates varied across brain areas during wakefulness and sleep [wake/sleep stages × brain areas interaction; Wald χ 2(df = 6) = 31.1, P < 0.0001]. N2-N3 non-rapid eye movement sleep increased interictal epileptiform discharges in mesial areas compared with wakefulness and rapid eye movement sleep (P < 0.0001), and to other areas (P < 0.0001 for all comparisons). This mesial pattern was observed both within and outside of seizure onset zones. During wakefulness, the rate of interictal epileptiform discharges was significantly higher than during N2-N3 non-rapid eye movement sleep (P = 0.04), and rapid eye movement sleep (P = 0.01) in lateral neocortical areas (referred to as lateral neocortical pattern), a finding that was more pronounced in seizures onset zones (P = 0.004). The morphological characteristics of the discharge events were modulated during wakefulness and sleep stages across brain areas. The effect of seizure onset zones on discharge morphology was conditioned by brain area and was particularly marked in temporal pole areas. Our analysis of discharge patterns in relation to cerebral localization, vigilance state and the anatomical affiliation of seizure onset zones revealed the global and local aspects of the complex relationship between interictal discharges, sleep and seizure onset zones. This novel approach may lead to a better understanding of cognitive decline and responses to therapy, as well as to adaptation of surgical interventions for epileptic patients.

Sleep-wake states change the interictal localization of candidate epileptic source generators

STUDY OBJECTIVES

To compare estimated epileptic source localizations from 5 sleep-wake states (SWS): wakefulness (W), rapid eye movement sleep (REM), and non-REM 1-3.

METHODS

Electrical source localization (sLORETA) of interictal spikes from different SWS on surface EEG from the epilepsy monitoring unit at spike peak and take-off, with results mapped to individual brain models for 75% of patients. Concordance was defined as source localization voxels shared between 2 and 5 SWS, and discordance as those unique to 1 SWS against 1-4 other SWS.

RESULTS

563 spikes from 16 prospectively recruited focal epilepsy patients across 161 day-nights. SWS exerted significant differences at spike peak but not take-off. Source localization size did not vary between SWS. REM localizations were smaller in multifocal than unifocal patients (28.8% vs. 54.4%, p = .0091). All five SWS contributed about 45% of their localizations to converge onto 17.0 ± 15.5% voxels. Against any one other SWS, REM was least concordant (54.4% vs. 66.9%, p = .0006) and most discordant (39.3% vs. 29.6%, p = .0008). REM also yielded the most unique localizations (20.0% vs. 8.6%, p = .0059).

CONCLUSIONS

REM was best suited to identify candidate epileptic sources. sLORETA proposes a model in which an "omni-concordant core" of source localizations shared by all five SWS is surrounded by a "penumbra" of source localizations shared by some but not all SWS. Uniquely, REM spares this core to "move" source voxels from the penumbra to unique cortex not localized by other SWS. This may reflect differential intra-spike propagation in REM, which may account for its reported superior localizing abilities.

Sleep and Temporal Lobe Epilepsy – Associations, Mechanisms and Treatment Implications

In this systematic review, we aim to describe the association between temporal lobe epilepsy (TLE) and sleep, with bidirectional links in mechanisms and therapeutic aspects. Sleep stages may variably impact seizure occurrence, secondary generalization and the development, frequency and distribution of interictal epileptiform discharges. Conversely, epilepsy affects sleep micro- and macroarchitecture. TLE, the most frequent form of drug resistant epilepsy (DRE), shares an enduring relationship with sleep, with some intriguing potential mechanisms specific to anatomic localization, linking the two. Sleep characteristics of TLE may also inform localizing properties in persons with DRE, since seizures arising from the temporal lobe seem to be more common during wakefulness, compared to seizures of extratemporal origin. Polysomnographic studies indicate that persons with TLE may experience excessive daytime somnolence, disrupted sleep architecture, increased wake after sleep onset, frequent shifts in sleep stages, lower sleep efficiency, decreased rapid eye movement (REM) sleep, and possibly, increased incidence of sleep apnea. Limited literature suggests that effective epilepsy surgery may remedy many of these objective and subjective sleep-related concerns, via multipronged effects, apart from reduced seizure frequency. Additionally, sleep abnormalities also seem to influence memory, language and cognitive-executive function in both medically controlled and refractory TLE. Another aspect of the relationship pertains to anti-seizure medications (ASMs), which may contribute significantly to sleep characteristics and abnormalities in persons with TLE. Literature focused on specific aspects of TLE and sleep is limited, and heterogeneous. Future investigations are essential to understand the pathogenetic mechanisms linking sleep abnormalities on epilepsy outcomes in the important sub-population of TLE.

Non-rapid eye movement sleep instability in adults with epilepsy: a systematic review and meta-analysis of cyclic alternating pattern

STUDY OBJECTIVES

Epilepsy is characterized by disrupted sleep architecture. Studies on sleep macro- and microstructure revealed that patients with epilepsy experience disturbed rapid eye movement (REM) sleep; however, no consensus has been reached on non-REM (NREM) sleep changes. Cyclic alternating pattern (CAP) is a marker of sleep instability that occurs only during NREM sleep. This meta-analysis investigated CAP differences between patients with epilepsy and healthy controls.

METHODS

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines in searching PubMed, Embase, and Cochrane Central database for studies comparing polysomnographic sleep microstructures between patients with epilepsy and healthy controls. A meta-analysis using a random-effects model was performed. We compared CAP rates, percentages of phase A1, A2, A3 subtypes, and phase B durations between patients with epilepsy and healthy controls.

RESULTS

A total of 11 studies, including 209 patients with epilepsy and 197 healthy controls, fulfilled the eligibility criteria. Compared with healthy controls, patients with epilepsy had significantly increased CAP rates and decreased A1 subtype percentages, and patients with sleep-related epilepsy had increased A3 subtype percentages. Subgroup analyses revealed that antiseizure medications (ASMs) decreased CAP rates and increased phase B durations but did not affect the microstates of phase A in patients with sleep-related epilepsy.

CONCLUSIONS

This meta-analysis detected statistically significant differences in CAP parameters between patients with epilepsy and healthy controls. Our findings suggest patients with epilepsy experience NREM sleep instability. ASMs treatment may decrease NREM instability but did not alter the microstates of phase A.

Relationship Between Epilepsy and Dreaming: Current Knowledge, Hypotheses, and Perspectives

The interactions between epilepsy and sleep are numerous and the impact of epilepsy on cognition is well documented. Epilepsy is therefore likely to influence dreaming as one sleep-related cognitive activity. The frequency of dream recall is indeed decreased in patients with epilepsy, especially in those with primary generalized seizures. The content of dreams is also disturbed in epilepsy patients, being more negative and with more familiar settings. While several confounding factors (anti-seizure medications, depression and anxiety disorders, cognitive impairment) may partly account for these changes, some observations suggest an effect of seizures themselves on dreams. Indeed, the incorporation of seizure symptoms in dream content has been described, concomitant or not with a focal epileptic discharge during sleep, suggesting that epilepsy might directly or indirectly interfere with dreaming. These observations, together with current knowledge on dream neurophysiology and the links between epilepsy and sleep, suggest that epilepsy may impact not only wake- but also sleep-related cognition.

Quantitative evaluation of the microstructure of rapid eye movement sleep in refractory epilepsy: a preliminary study using electroencephalography and heart rate variability analysis

INTRODUCTION

Patients with epilepsy have a disturbed sleep architecture. Polysomnographic studies have shown that patients with refractory epilepsy have decreased rapid eye movement (REM) sleep and longer REM latency than those with medically controlled epilepsy. However, little is known about the differences in the REM sleep microstructure between these patient groups.

METHODS

We conducted a retrospective case-control study of 20 patients with refractory epilepsy (refractory group) and 28 patients with medically controlled epilepsy (medically controlled group). All patients completed sleep questionnaires and underwent overnight in-lab polysomnography. Five-minute electroencephalogram recordings at the C3 and C4 electrodes from each REM sleep were selected for spectral analysis, and 5-min electrocardiogram segments recorded during REM sleep were used for heart rate variability analysis. The groups' scores on the sleep questionnaires, polysomnographic sleep parameters, indices of sleep-related breathing disorders, and REM sleep electroencephalogram spectra were compared.

RESULTS

The refractory group had decreased REM sleep (p < 0.001) and longer REM latency (p = 0.0357) than those of the medically controlled group. Moreover, electroencephalogram spectral analysis revealed that the refractory group had decreased absolute beta power (p = 0.0039) and relative beta power (p = 0.0035) as well as increased relative delta power (p = 0.0015) compared with the medically controlled group.

CONCLUSIONS

Differences in the polysomnographic macrostructure and REM sleep microstructure between the study groups suggest REM sleep dysregulation in patients with refractory epilepsy.

Regulation of microRNA Expression in Sleep Disorders in Patients with Epilepsy

The effects of epilepsy on sleep and the activating effects of sleep on seizures are well documented in the literature. To date, many sleep-related and awake-associated epilepsy syndromes have been described. The relationship between sleep and epilepsy has led to the recognition of polysomnographic testing as an important diagnostic tool in the diagnosis of epilepsy. The authors analyzed the available medical database in search of other markers that assess correlations between epilepsy and sleep. Studies pointing to microRNAs, whose abnormal expression may be common to epilepsy and sleep disorders, are promising. In recent years, the role of microRNAs in the pathogenesis of epilepsy and sleep disorders has been increasingly emphasized. MicroRNAs are a family of single-stranded, non-coding, endogenous regulatory molecules formed from double-stranded precursors. They are typically composed of 21–23 nucleotides, and their main role involves post-transcriptional downregulation of expression of numerous genes. Learning more about the role of microRNAs in the pathogenesis of sleep disorder epilepsy may result in its use as a biomarker in these disorders and application in therapy.

The impact of antiseizure medications on polysomnographic parameters: a systematic review and meta-analysis

BACKGROUND

Oral antiseizure medications (ASMs) are first-line treatments for patients with epilepsy. However, ASMs may alter sleep architecture, adversely affecting patient outcomes. The meta-analysis aimed to elucidate the effect of ASMs on sleep architecture.

METHODS

PubMed, Embase, and Cochrane Central database (up to Febrary 2021) were searched for randomized control trials (RCT) with effects of ASMs on polysomnography parameters. A meta-analysis using a random-effects model was performed. We did not set limitation to the participants with underlying diagnosis of epilepsy.

RESULTS

Eighteen randomized-controlled trials fulfilled the eligibility criteria. The effects of five main groups of ASMs (sodium channel blockers, calcium channel blockers, GABA enhancers, synaptic vesicle glycoprotein 2A [SV2A] ligand, and broad-spetrum ASMs) on slow-wave sleep (SWS), rapid eye movement (REM) sleep, and sleep efficiency (SE) were analyzed. Compared with placebo, calcium channel blockers and GABA enhancers significantly increased SWS. GABA enhancers also decreased REM sleep percentage, whereas calcium channel blockers significantly increased SE. Sodium channel blockers, SV2A ligand and broad-spectrum ASMs did not affect SWS, REM sleep, or SE. The subgroup analysis revealed that gabapentin, pregabalin, and tiagabine increased the percentage of SWS. Tiagabine also decreased REM sleep, whereas pregabalin increased SE. Finally, levetiracetam did not affect SWS, REM sleep, and SE.

CONCLUSIONS

This meta-analysis indicated that ASMs can have a statistically significant effect on sleep parameters; the effect differs between ASMs.

Sleep profile and Polysomnography in patients with drug-resistant temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS) and the effect of epilepsy surgery on sleep-a prospective cohort study

OBJECTIVES

We analyzed changes in sleep profile and architecture of patients with drug-resistant TLE-HS using three validated sleep questionnaires- Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), NIMHANS Comprehensive Sleep Disorders, and polysomnography (PSG). We studied the effect of epilepsy surgery in a subset of patients.

METHODS

In this prospective observational cohort study, sleep profile of 40 patients with drug-resistant TLE-HS was compared to 40 healthy matched controls. Sleep architecture of 22 patients was studied by overnight PSG and compared to 22 matched controls. Sleep profile was reassessed in 20 patients after a minimum period of three months after epilepsy surgery.

RESULTS

The mean PSQI was higher among patients compared to controls(P=0.0004) while mean ESS showed no difference. NCSDQ showed fewer patients feeling refreshed after a night's sleep compared to controls (p=0.006). PSG revealed a higher time in bed (p=0.0001), longer total sleep time (p=0.006) and more time spent in NREM stage 1 (p=0.001) and stage 2 (p=0.005) while spending less time in stage 3 (p=0.039) among TLE patients. Sleep efficiency was worse in patients on ≥3 ASMs compared to those on 2 ASMs (p-0.044). There was no change in mean ESS (p=0.48) or PSQI (p=0.105) after surgery.

CONCLUSIONS

Patients with drug-resistant TLE-HS have an altered sleep profile and architecture. Patients on ≥3 ASMs have a lower sleep efficiency. Reassessment at short intervals after epilepsy surgery did not reveal significant changes in sleep profile.

Rapid eye movement sleep disturbance in patients with refractory epilepsy: A polysomnographic study

OBJECTIVE/BACKGROUND

Patients with epilepsy have disrupted sleep architecture and a higher prevalence of sleep disturbance. Moreover, obstructive sleep apnea (OSA) is more common among patients with refractory epilepsy. Few studies have compared subjective sleep quality, sleep architecture, and prevalence of OSA between patients with refractory epilepsy and those with medically controlled epilepsy. Therefore, this study aimed to evaluate the differences in sleep quality, sleep architecture, and prevalence of OSA between patients with refractory epilepsy and patients with medically controlled epilepsy.

PATIENTS

This retrospective case-control study included 38 patients with refractory epilepsy and 96 patients with medically controlled epilepsy. Sleep parameters and indices of sleep-related breathing disorders were recorded by standard in-laboratory polysomnography. The scores from sleep questionnaires on sleep quality and daytime sleepiness were compared between the two groups.

RESULTS

Patients with refractory epilepsy versus medically controlled epilepsy had statistically significantly decreased rapid eye movement (REM) sleep (13.5 ± 6.1% vs. 16.2 ± 6.1%) and longer REM latency (152.2 ± 84.1 min vs. 117.2 ± 61.9 min). Further, no differences were found in the prevalence of sleep-related breathing disorders, subjective sleep quality, prevalence of daytime sleepiness, and quality of life. Although not statistically significant, patients with refractory epilepsy have a lower rate of OSA compared with those with medically controlled epilepsy (21.1% vs. 30.2%).

CONCLUSIONS

Patients with refractory epilepsy had more disrupted REM sleep regulation than those with medically controlled epilepsy. Although patients with epilepsy have a higher risk of OSA, in this study patients with refractory epilepsy were not susceptible to OSA.

Electro-Encephalography and Electro-Oculography in Aeronautics: A Review Over the Last Decade (2010-2020)

Electro-encephalography (EEG) and electro-oculography (EOG) are methods of electrophysiological monitoring that have potentially fruitful applications in neuroscience, clinical exploration, the aeronautical industry, and other sectors. These methods are often the most straightforward way of evaluating brain oscillations and eye movements, as they use standard laboratory or mobile techniques. This review describes the potential of EEG and EOG systems and the application of these methods in aeronautics. For example, EEG and EOG signals can be used to design brain-computer interfaces (BCI) and to interpret brain activity, such as monitoring the mental state of a pilot in determining their workload. The main objectives of this review are to, (i) offer an in-depth review of literature on the basics of EEG and EOG and their application in aeronautics; (ii) to explore the methodology and trends of research in combined EEG-EOG studies over the last decade; and (iii) to provide methodological guidelines for beginners and experts when applying these methods in environments outside the laboratory, with a particular focus on human factors and aeronautics. The study used databases from scientific, clinical, and neural engineering fields. The review first introduces the characteristics and the application of both EEG and EOG in aeronautics, undertaking a large review of relevant literature, from early to more recent studies. We then built a novel taxonomy model that includes 150 combined EEG-EOG papers published in peer-reviewed scientific journals and conferences from January 2010 to March 2020. Several data elements were reviewed for each study (e.g., pre-processing, extracted features and performance metrics), which were then examined to uncover trends in aeronautics and summarize interesting methods from this important body of literature. Finally, the review considers the advantages and limitations of these methods as well as future challenges.

Depression is a major determinant of sleep abnormalities in patients with epilepsy

ABSTRACT Introduction: We aimed to identify sleep disorders in patients with epilepsy and compare this group with a healthy population. We also analyzed the features of sleep disorders in patients with epilepsy to demonstrate the effect of seizures and seizure types on sleep. Methods: Our study assessed 43 patients with epilepsy and 53 age- and gender-matched healthy controls. The demographic and clinical data of all participants were recorded. The Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index (PSQI), International Restless Legs Syndrome Study Group Rating Scale, Berlin Questionnaire, and Beck Depression Inventory (BDI) were administered to all study subjects. The interview used to evaluate insomnia is based on the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition - DSM-5 diagnostic criteria. Results: Twenty-four patients (55.8%) and 26 controls (49.1%) are women. The mean age of patients and controls was 34.2±11.37 (16-71) and 34.6±11.28 (16-77), respectively. Patients with epilepsy had depression more often than controls, a result that was statistically significant (p<0.0001). We found no statistically significant difference between sleep parameters of patients and controls with normal BDI scores (p>0.05). Patients with depression had worse results on the Berlin Questionnaire and PSQI total score, with statistical significance (p=0.002). Nocturnal seizures, seizure type, and drug treatment had no effect on sleep (p>0.05). Conclusion: We concluded that depression rather than epilepsy negatively affects sleep, suggesting that all patients should be asked about their mood and sleep complaints.

Can REM Sleep Localize the Epileptogenic Zone? A Systematic Review and Analysis

Epilepsy is a common and debilitating neurological disease. When medication cannot control seizures in up to 40% of cases, surgical resection of epileptogenic tissue is a clinically and cost- effective therapy to achieve seizure freedom. To simultaneously resect minimal yet sufficient cortex, exquisite localization of the epileptogenic zone (EZ) is crucial. However, localization is not straightforward, given relative difficulty of capturing seizures, constraints of the inverse problem in source localization, and possible disparate locations of symptomatogenic vs. epileptogenic regions. Thus, attention has been paid to which state of vigilance best localizes the EZ, in the hopes that one or another sleep-wake state may hold the key to improved accuracy of localization. Studies investigating this topic have employed diverse methodologies and produced diverse results. Nonetheless, rapid eye movement sleep (REM) has emerged as a promising sleep-wake state, as epileptic phenomena captured in REM may spatially correspond more closely to the EZ. Cortical neuronal asynchrony in REM may spatially constrain epileptic phenomena to reduce propagation away from the source generator, rendering them of high localizing value. However, some recent work demonstrates best localization in sleep-wake states other than REM, and there are reports of REM providing clearly false localization. Moreover, synchronistic properties and basic mechanisms of human REM remain to be fully characterized. Amidst these uncertainties, there is an urgent need for recording and analytical techniques to improve accuracy of localization. Here we present a systematic review and quantitative analysis of pertinent literature on whether and how REM may help localize epileptogenic foci. To help streamline and accelerate future work on the intriguing anti-epileptic properties of REM, we also introduce a simple, conceptually clear set-theoretic framework to conveniently and rigorously describe the spatial properties of epileptic phenomena in the brain.

Interictal epileptiform activity in sleep and wakefulness in patients with temporal lobe epilepsy

Sleep is an important activator of epileptiform activity, with epileptiform discharge (ED) probability varying among sleep stages. The aim of our study was to analyze the association between epileptiform activity and sleep stages or wakefulness in adults with temporal discharges. We analyzed 32 long-term overnight EEG recordings. All focal discharges were marked, and the entire sleep was staged. Absolute general epileptiform discharge index (EDI), defined as a ratio of total ED number to the full recording time in hours, as well as absolute EDIs for REM, N1, N2 and N3 stages were calculated. The majority of patients (28) had the highest EDI in N3. EDI increased significantly while sleep progressed to deeper stages, reaching its peak in N3. In REM sleep, EDI sharply declined (p < 0.01) reaching the levels of wakefulness. Increasing synchronization of cortical neurons is thought to be the major mechanism of EDI rise in NREM sleep. Hence, N3 seems to be the most sensitive stage to capture EDs, which highlights the importance of deep sleep recording in patients with temporal epilepsy.

Is self-report sleepiness associated with cognitive performance in temporal lobe epilepsy?

OBJECTIVES

Sleepiness and cognitive impairment are common symptoms observed in patients with epilepsy. We investigate whether self-reported sleepiness is associated with cognitive performance in patients with refractory mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). Seventy-one consecutive patients with MTLE-HS were evaluated with the Stanford Sleepiness Scale (SSS) before neuropsychological evaluation. Their mean SSS scores were compared with controls. Each cognitive test was compared between patients with (SSS ≥ 3) or without sleepiness (SSS < 3). Imbalances were controlled by regression analysis. Patients reported a significantly higher degree of sleepiness than controls (p < 0.0001). After multiple linear regression analysis, only one test (RAVLT total) remained associated with self-reported sleepiness.

CONCLUSION

Self-reported sleepiness was significantly higher in MTLE-HS patients than controls, but did not affect their cognitive performance. If confirmed in other populations, our results may have implications for decision making about sleepiness screening in neuropsychological settings.