Effect of sleep deprivation on spike-wave discharges in idiopathic generalised epilepsy: a 4 x 24 h continuous long term EEG monitoring study

Prospective study of epilepsy with generalized tonic-clonic seizures alone: Clinical features, response to treatment, and likelihood of medication withdrawal

OBJECTIVE

This prospective study aimed to delineate the demographics, natural progression, and treatment response of patients newly diagnosed with epilepsy with generalized tonic-clonic seizures alone (EGTCA). Furthermore, our objective includes assessing the seizure recurrence rate post antiseizure medication (ASM) discontinuation within this cohort, alongside exploring predictive factors for seizure relapse.

METHODS

The study cohort, derived from an ongoing, prospective, multicenter investigation on children and adults with new-onset unprovoked seizures, included consecutive patients enrolled between March 2010 and March 2020, and meeting mandatory ILAE criteria for EGTCA diagnosis. Participants underwent a 3-h sleep-deprived video-EEG recording along with an epilepsy protocol brain magnetic resonance imaging (MRI) with repeat EEG at each follow-up. Cumulative time-dependent probabilities of seizure recurrence were calculated using Kaplan-Meier survival analysis. Logistic regression identified variables associated with seizure recurrence following ASM taper.

RESULTS

Eighty-nine patients with a median age of 16 years were included, constituting 31% of those diagnosed with an idiopathic generalized epilepsy. Regarding the circadian distribution of seizures, 59.6% of patients exclusively experienced diurnal seizures, 12.4% exclusively nocturnal, and 28.1% experienced both diurnal and nocturnal seizures. Generalized spike-wave discharges (GSWD) were present in the initial EEG of 88% of patients. A GTC recurred in 14% of patients treated with ASM compared with 73% of untreated patients (p < 0.00001). ASM discontinuation was attempted in 50 patients after a median treatment duration of 3 years, with 44% experiencing a recurrence. Patient-initiated taper and a mixed circadian seizure pattern independently predicted a higher likelihood of recurrence post-ASM discontinuation.

SIGNIFICANCE

Our findings underscore the importance of prompt treatment upon the diagnosis of EGTCA. Notably, lifelong treatment may not be imperative; patients seizure-free for at least 2 years, with the absence of GSWD on EEG, often maintained seizure freedom after ASM withdrawal, especially with physician-initiated tapering.

PLAIN LANGUAGE SUMMARY

Seizures in individuals diagnosed with "epilepsy with generalized tonic-clonic seizures alone" (EGTCA) typically start during adolescence and often respond well to antiseizure medications. An electroencephalogram, which measure brain waves, will show abnormal discharges in most patients with EGTCA. Lifelong treatment with antiseizure medication is not necessary for everyone with EGTCA; approximately, 40% can successfully stop treatment without facing seizure recurrence. Patients who stop medication on their own have a higher risk of seizures returning compared with those who undergo cessation under a doctor's supervision.

Circadian distribution of epileptiform discharges in epilepsy: Candidate mechanisms of variability

Epilepsy is a serious neurological disorder characterised by a tendency to have recurrent, spontaneous, seizures. Classically, seizures are assumed to occur at random. However, recent research has uncovered underlying rhythms both in seizures and in key signatures of epilepsy-so-called interictal epileptiform activity-with timescales that vary from hours and days through to months. Understanding the physiological mechanisms that determine these rhythmic patterns of epileptiform discharges remains an open question. Many people with epilepsy identify precipitants of their seizures, the most common of which include stress, sleep deprivation and fatigue. To quantify the impact of these physiological factors, we analysed 24-hour EEG recordings from a cohort of 107 people with idiopathic generalized epilepsy. We found two subgroups with distinct distributions of epileptiform discharges: one with highest incidence during sleep and the other during day-time. We interrogated these data using a mathematical model that describes the transitions between background and epileptiform activity in large-scale brain networks. This model was extended to include a time-dependent forcing term, where the excitability of nodes within the network could be modulated by other factors. We calibrated this forcing term using independently-collected human cortisol (the primary stress-responsive hormone characterised by circadian and ultradian patterns of secretion) data and sleep-staged EEG from healthy human participants. We found that either the dynamics of cortisol or sleep stage transition, or a combination of both, could explain most of the observed distributions of epileptiform discharges. Our findings provide conceptual evidence for the existence of underlying physiological drivers of rhythms of epileptiform discharges. These findings should motivate future research to explore these mechanisms in carefully designed experiments using animal models or people with epilepsy.

Sleep quality and architecture in Idiopathic generalized epilepsy: A systematic review and meta-analysis

Idiopathic generalized epilepsies are a group of sleep related epilepsy syndromes with sleep deprivation as a strong trigger for seizures and increased spike-wave activity during sleep and transition to sleep. Neuropsychological deficits are common in Idiopathic generalized epilepsy patients. Learning and memory processes are closely linked to sleep. Therefore, this systematic review and meta-analysis investigates the evidence of sleep disturbances in Idiopathic generalized epilepsy patients. A search of the databases EMBASE, Medline and Scopus identified 22 studies comparing polysomnographic parameters and scores of sleep questionnaires between Idiopathic generalized epilepsy patients and healthy controls. Random effect univariate meta-analyses revealed reduced sleep efficiency, total sleep time, proportion of N2 stage and prolonged REM onset latency in Idiopathic generalized epilepsy patients. Self-assessed sleep quality of patients measured by the Pittsburgh sleep quality index was lower in two thirds of reporting studies. Considering the influence on behavioral issues, cognitive performance and quality of life, the revealed alteration in sleep architecture and lower subjective sleep quality emphasizes the importance of screening for sleep disturbances in the medical care of patients with Idiopathic generalized epilepsy.

Pretreatment electroencephalographic features in patients with childhood absence epilepsy

OBJECTIVE

To analyze the ictal and interictal electroencephalographic (EEG) features in newly diagnosed childhood absence epilepsy (CAE) and determine the association between seizure onset topography, interictal focal spike-wave discharges (FSWDs) and accompanying clinical features of absence seizures.

METHODS

The authors searched the EEG database for a definite diagnosis of CAE according to ILAE 2017 criteria. Video-EEGs of untreated pediatric patients during sleep and wakefulness were evaluated retrospectively.

RESULTS

The study included 47 patients (25 males, 22 females). Interictal FSWDs were observed in 49% of patients with CAE during wakefulness and in 85.1% during sleep (p = 0.001). Interictal FSWDs were most frequently observed in the frontal regions (awake: 34%; asleep: 74.5%), followed by the posterior temporoparietooccipital region (awake: 21.2%; asleep: 36.1%), and the centrotemporal region (awake: 6.4%; asleep: 8.5%). Eleven patients (23.4%) had polyspikes during sleep. Both bilateral symmetric and asymmetric seizure onset were noted in 32%, whereas focal seizure onset was observed in 14.9% of the patients. Absence seizures with and without motor components were seen in 72.3% and 61.7% of patients, respectively, and in 33% of patients both occurred. There were no associations between the existence of interictal FSWDs, focal/asymmetric seizure onset, and absence seizures with and/or without motor components.

CONCLUSION

Asymmetric and/or focal seizure onset, interictal FSWDs, and absence seizures with motor components are commonly observed in drug-naive CAE. This study found no association between seizure onset topography, interictal FSWDs, and semiological features of absence seizures.

From Physiology to Pathology of Cortico-Thalamo-Cortical Oscillations: Astroglia as a Target for Further Research

The electrographic hallmark of childhood absence epilepsy (CAE) and other idiopathic forms of epilepsy are 2.5-4 Hz spike and wave discharges (SWDs) originating from abnormal electrical oscillations of the cortico-thalamo-cortical network. SWDs are generally associated with sudden and brief non-convulsive epileptic events mostly generating impairment of consciousness and correlating with attention and learning as well as cognitive deficits. To date, SWDs are known to arise from locally restricted imbalances of excitation and inhibition in the deep layers of the primary somatosensory cortex. SWDs propagate to the mostly GABAergic nucleus reticularis thalami (NRT) and the somatosensory thalamic nuclei that project back to the cortex, leading to the typical generalized spike and wave oscillations. Given their shared anatomical basis, SWDs have been originally considered the pathological transition of 11-16 Hz bursts of neural oscillatory activity (the so-called sleep spindles) occurring during Non-Rapid Eye Movement (NREM) sleep, but more recent research revealed fundamental functional differences between sleep spindles and SWDs, suggesting the latter could be more closely related to the slow (<1 Hz) oscillations alternating active (Up) and silent (Down) cortical activity and concomitantly occurring during NREM. Indeed, several lines of evidence support the fact that SWDs impair sleep architecture as well as sleep/wake cycles and sleep pressure, which, in turn, affect seizure circadian frequency and distribution. Given the accumulating evidence on the role of astroglia in the field of epilepsy in the modulation of excitation and inhibition in the brain as well as on the development of aberrant synchronous network activity, we aim at pointing at putative contributions of astrocytes to the physiology of slow-wave sleep and to the pathology of SWDs. Particularly, we will address the astroglial functions known to be involved in the control of network excitability and synchronicity and so far mainly addressed in the context of convulsive seizures, namely (i) interstitial fluid homeostasis, (ii) K⁺ clearance and neurotransmitter uptake from the extracellular space and the synaptic cleft, (iii) gap junction mechanical and functional coupling as well as hemichannel function, (iv) gliotransmission, (v) astroglial Ca²⁺ signaling and downstream effectors, (vi) reactive astrogliosis and cytokine release.

Commonalities and Differences in NREM Parasomnias and Sleep-Related Epilepsy: Is There a Continuum Between the Two Conditions?

Introduction: Differential diagnosis between disorders of arousal (DoA) and sleep-related hypermotor epilepsy (SHE) often represents a clinical challenge. The two conditions may be indistinguishable from a semiological point of view and the scalp video-polysomnography is often uninformative. Both disorders are associated with variable hypermotor manifestations ranging from major events to fragments of a hierarchical continuum of increasing intensity, complexity, and duration. Given their semiological overlap we decided to explore the sleep texture of DoA and SHE seeking for similarities and differences.

Methods: We analyzed sleep macrostructure and CAP (cyclic alternating pattern) parameters in a cohort of 35 adult DoA patients, 40 SHE patients and 24 healthy sleepers, all recorded and scored in the same sleep laboratory. Nocturnal behavioral manifestations included minor motor events, paroxysmal arousals and major attacks in SHE, and simple, rising, or complex arousal movements in DoA.

Results: Compared to healthy controls, DoA and SHE showed similar amounts of sleep efficiency, light sleep, deep sleep, REM sleep, CAP subtypes. Both groups also showed slow wave sleep fragmentation and an increased representation of stage N3 in the second part of the night. The only discriminating elements between the two conditions regarded sleep length (more reduced in DoA) and sleep instability (more elevated in SHE). In DoA recordings, all motor episodes arose from NREM sleep: 37% during light NREM stages and 63% during stage N3 (simple arousal movements: 94%). In SHE recordings, 57% of major attacks occurred during stage N3.

Conclusions: So far, emphasis has been placed on the differentiation of sleep-related epilepsy and NREM arousal disorders. However, the impressive analogies between DoA and SHE suggest the existence of an underestimated continuum across the conditions, linked by increased levels of sleep instability, higher amounts of slow wave sleep and NREM/REM sleep imbalance. Sleep texture is extremely similar in the two conditions, although CAP metrics disclose quantitative differences. In particular, SHE patients show a higher arousal instability compared to DoA subjects. Given their clinical and epidemiological overlap, a common genetic background is also hypothesized. In such a perspective, we suggest that the consolidated dichotomy DoA vs. SHE should be reappraised.

Sleep and Epilepsy Link by Plasticity

We aimed to explore the link between NREM sleep and epilepsy. Based on human and experimental data we propose that a sleep-related epileptic transformation of normal neurological networks underlies epileptogenesis. Major childhood epilepsies as medial temporal lobe epilepsy (MTLE), absence epilepsy (AE) and human perisylvian network (PN) epilepsies - made us good models to study. These conditions come from an epileptic transformation of the affected functional systems. This approach allows a system-based taxonomy instead of the outworn generalized-focal classification. MTLE links to the memory-system, where epileptic transformation results in a switch of normal sharp wave-ripples to epileptic spikes and pathological high frequency oscillations, compromising sleep-related memory consolidation. Absence epilepsy (AE) and juvenile myoclonic epilepsy (JME) belong to the corticothalamic system. The burst-firing mode of NREM sleep normally producing sleep-spindles turns to an epileptic working mode ejecting bilateral synchronous spike-waves. There seems to be a progressive transition from AE to JME. Shared absences and similar bilateral synchronous discharges show the belonging of the two conditions, while the continuous age windows - AE affecting schoolchildren, JME the adolescents - and the increased excitability in JME compared to AE supports the notion of progression. In perisylvian network epilepsies - idiopathic focal childhood epilepsies and electrical status epilepticus in sleep including Landau-Kleffner syndrome - centrotemporal spikes turn epileptic, with the potential to cause cognitive impairment. Postinjury epilepsies modeled by the isolated cortex model highlight the shared way of epileptogenesis suggesting the derailment of NREM sleep-related homeostatic plasticity as a common step. NREM sleep provides templates for plasticity derailing to epileptic variants under proper conditions. This sleep-origin explains epileptiform discharges' link and similarity with NREM sleep slow oscillations, spindles and ripples. Normal synaptic plasticity erroneously overgrowing homeostatic processes may derail toward an epileptic working-mode manifesting the involved system's features. The impact of NREM sleep is unclear in epileptogenesis occurring in adolescence and adulthood, when plasticity is lower. The epileptic process interferes with homeostatic synaptic plasticity and may cause cognitive impairment. Its type and degree depends on the affected network's function. We hypothesize a vicious circle between sleep end epilepsy. The epileptic derailment of normal plasticity interferes with sleep cognitive functions. Sleep and epilepsy interconnect by the pathology of plasticity.

EEG autoregressive modeling analysis: A diagnostic tool for patients with epilepsy without epileptiform discharges

OBJECTIVE

Numerous types of nonepileptic paroxysmal events, such as syncopes and psychogenic nonepileptic seizures, may imitate epileptic seizures and lead to diagnostic difficulty. Such misdiagnoses may lead to inappropriate treatment in patients that can considerably affect their lives. Electroencephalogram (EEG) is a commonly used tool in assisting diagnosis of epilepsy. Although the appearance of epileptiform discharges (EDs) in EEG recordings is specific for epilepsy diagnosis, only 25%-56% of patients with epilepsy show EDs in their first EEG examination.

METHODS

In this study, we developed an autoregressive (AR) model prediction error-based EEG classification method to distinguish EEG signals between controls and patients with epilepsy without EDs. Twenty-three patients with generalized epilepsy without EDs in their EEG recordings and 23 age-matched controls were enrolled. Their EEG recordings were classified using AR model prediction error-based EEG features.

RESULTS

Among different classification methods, XGBoost achieved the highest performance in terms of accuracy and true positive rate. The results showed that the accuracy, area under the curve, true positive rate, and true negative rate were 85.17%, 87.54%, 89.98%, and 81.81%, respectively.

CONCLUSIONS

Our proposed method can help neurologists in the early diagnosis of epilepsy in patients without EDs and might help in differentiating between nonepileptic paroxysmal events and epilepsy.

SIGNIFICANCE

EEG AR model prediction errors could be used as an alternative diagnostic marker of epilepsy.

Circadian Rhythms and Epilepsy: A Suitable Case for Absence Epilepsy

Many physiological processes such as sleep, hormonal secretion, or thermoregulation, are expressed as daily rhythms orchestrated by the circadian timing system. A powerful internal clock mechanism ensures proper synchronization of vital functions within an organism on the one hand, and between the organism and the external environment on the other. Some of the pathological processes developing in the brain and body are subjected to circadian modulation as well. Epilepsy is one of the conditions which symptoms often worsen at a very specific time of a day. Variation in peak occurrence depends on the syndrome and localization of the epileptic focus. Moreover, the timing of some types of seizures is closely related to the sleep-wake cycle, one of the most prominent circadian rhythms. This review focuses on childhood absence epilepsy (CAE), a genetic generalized epilepsy syndrome, in which both, the circadian and sleep influences play a significant role in manifestation of symptoms. Human and animal studies report rhythmical occurrence of spike-wave discharges (SWDs), an EEG hallmark of CAE. The endogenous nature of the SWDs rhythm has been confirmed experimentally in a genetic animal model of the disease, rats of the WAG/Rij strain. Well-known detrimental effects of circadian misalignment were demonstrated to impact the severity of ongoing epileptic activity. SWDs are vigilance-dependent in both humans and animal models, occurring most frequently during passive behavioral states and light slow-wave sleep. The relationship with the sleep-wake cycle seems to be bidirectional, while sleep shapes the rhythm of seizures, epileptic phenotype changes sleep architecture. Circadian factors and the sleep-wake states dependency have a potential as add-ons in seizures' forecasting. Stability of the rhythm of recurrent seizures in individual patients has been already used as a variable which refines existing algorithms for seizures' prediction. On the other hand, apart from successful pharmacological approach, circadian hygiene including sufficient sleep and avoidance of internal desynchronization or sleep loss, may be beneficial for patients with epilepsy in everyday management of seizures.

Awareness and current knowledge of epilepsy

Epilepsy is a severe neural disorder that affects approximately fifty million individuals globally. Despite the fact that for most of the people with epilepsy, convulsions are better controlled by current accessible antiepileptic medicines, yet there are more than 30% of individuals affected with medically intractable epilepsy and around 30-40% of all patients with epilepsy affected by many adverse reactions and convulsion resistance to the present antiepileptic drugs. Consequently, various scientists attempt to develop new strategies to treat epilepsy, for instance, to find out novel antiepileptic ingredients from traditional medicines. This work aims to present a complete summary of natural medicines prescribed as antiepileptic agents all over the world by ethnic groups and different tribes. We undertook an extensive bibliographic analysis by searching peer reviewed papers and classical textbooks and further consulting well accepted worldwide scientific databases. We carried out PubMed, EMbase and CENTRAL searches by means of terms such as "antiepileptic" and "anti-convulsant" activity of plants. Medicinal plants have been prescribed to treat epilepsy and have been recognized as antiepileptic medicines. In this review, a variety of herbs have been reviewed for thorough studies such as Cuminum cyminum, Butea monosperma, Solanum americanum, Anacyclus pyrethrum, Leonotis leonurus, Elaeocarpus ganitrus and Angelica archangelica. This paper shows that it was high time experimental studies are increased to obtain novel potential active principles from medicinal plants. Plant extracts and their chemical constituents should be further evaluated to clarify their mechanisms of action. This paper provides a solid base upon which to further investigate the clinical efficacy of medicinal plants that are both currently prescribed by physicians as traditional antiepileptic agents, but also could be effective as an antiepileptic drug with further research and study.

Can absence seizures be predicted by vigilance states?: Advanced analysis of sleep-wake states and spike-wave discharges' occurrence in rats

Spike-wave discharges (SWDs) are the main manifestation of absence epilepsy. Their occurrence is dependent on the behavioral state, and they preferentially occur during unstable vigilance periods. The present study investigated whether the occurrence of SWDs can be predicted by the preceding behavioral state and whether this relationship is different between the light and the dark phases of the 24-h day. Twenty-four-hour (12:12 light/dark phases) electroencephalographic (EEG) recordings of 12 Wistar Albino Glaxo, originally bred in Rijswijk (WAG/Rij) rats, a well-known genetic model of absence epilepsy, were analyzed and transformed into sequences of 2-s length intervals of the following 6 possible states: active wakefulness (AW), passive wakefulness (PW), deep slow-wave sleep (DSWS), light slow-wave sleep (LSWS), rapid eye movement (REM) sleep, and SWDs, given discrete series of categorical data. Probabilities of all transitions between states and Shannon entropy of transitions were calculated for the light and dark phases separately and statistically analyzed. Common differences between the light and the dark phases were found regarding the time spent in AW, LSWS, DSWS, and SWDs. The most probable transitions were that AW was preceded and followed by PW and vice versa regardless of the phase of the photoperiod. A similar relationship was found for light and deep slow-wave sleep. The most probable transitions to and from SWDs were AW and LSWS, respectively, with these transition likelihoods being consistent across both circadian phases. The second most probable transitions around SWDs appeared more variable between light and dark. During the light phase, SWDs occurred around PW and participated exclusively in sleep initiation; in the dark phase, SWDs were seen on both, ascending and descending steps towards and from sleep. Conditional Shannon entropy showed that AW and DSWS are the most predictable events, while the possible prediction horizon of SWDs is not larger than 4 s and despite the higher occurrence of SWDs in the dark phase, did not differ between phases. It can be concluded that although SWDs show a stable, strong circadian rhythm with a peak in number during the dark phase, their occurrence cannot be reliably predicted by the preceding behavioral state, except at a very short time base.

Alternative Diagnosis of Epilepsy in Children Without Epileptiform Discharges Using Deep Convolutional Neural Networks

Numerous nonepileptic paroxysmal events, such as syncope and psychogenic nonepileptic seizures, may imitate seizures and impede diagnosis. Misdiagnosis can lead to mistreatment, affecting patients’ lives considerably. Electroencephalography is commonly used for diagnosing epilepsy. Although on electroencephalograms (EEGs), epileptiform discharges (ED) specifically indicate epilepsy, only approximately 50% of patients with epilepsy have ED in their first EEG. In this study, we developed a deep convolutional neural network (ConvNet)-based classifier to distinguish EEG between patients with epilepsy without ED and controls. Overall, 25 patients with epilepsy without ED in their EEGs and 25 age-matched patients with Tourette syndrome or syncope were enrolled. Their EEGs were classified using the deep ConvNet. When the EEG data without overlapping were used, the accuracy, sensitivity, and specificity were 65.00%, 48.00%, and 82.00%, respectively. The performance measures improved when the input EEG data were augmented through overlapping. With 95% EEG data overlapping, the accuracy, sensitivity, and specificity increased to 80.00%, 70.00%, and 90.00%, respectively. The proposed method could be regarded as a pilot study to demonstrate a proof of concept of a potential diagnostic value of deep ConvNet in patients with epilepsy without ED. Further studies are needed to assist neurologists in distinguishing nonepileptic paroxysmal events from epilepsy.

The Mutual Interaction Between Sleep and Epilepsy on the Neurobiological Basis and Therapy

BACKGROUND

Sleep and epilepsy are mutually related in a complex, bidirectional manner. However, our understanding of this relationship remains unclear.

RESULTS

The literatures of the neurobiological basis of the interactions between sleep and epilepsy indicate that non rapid eye movement sleep and idiopathic generalized epilepsy share the same thalamocortical networks. Most of neurotransmitters and neuromodulators such as adenosine, melatonin, prostaglandin D2, serotonin, and histamine are found to regulate the sleep-wake behavior and also considered to have antiepilepsy effects; antiepileptic drugs, in turn, also have effects on sleep. Furthermore, many drugs that regulate the sleep-wake cycle can also serve as potential antiseizure agents. The nonpharmacological management of epilepsy including ketogenic diet, epilepsy surgery, neurostimulation can also influence sleep.

CONCLUSION

In this paper, we address the issues involved in these phenomena and also discuss the various therapies used to modify them.

Electroencephalography in the Diagnosis of Genetic Generalized Epilepsy Syndromes

Genetic generalized epilepsy (GGE) consists of several syndromes diagnosed and classified on the basis of clinical features and electroencephalographic (EEG) abnormalities. The main EEG feature of GGE is bilateral, synchronous, symmetric, and generalized spike-wave complex. Other classic EEG abnormalities are polyspikes, epileptiform K-complexes and sleep spindles, polyspike-wave discharges, occipital intermittent rhythmic delta activity, eye-closure sensitivity, fixation-off sensitivity, and photoparoxysmal response. However, admixed with typical changes, atypical epileptiform discharges are also commonly seen in GGE. There are circadian variations of generalized epileptiform discharges. Sleep, sleep deprivation, hyperventilation, intermittent photic stimulation, eye closure, and fixation-off are often used as activation techniques to increase the diagnostic yield of EEG recordings. Reflex seizure-related EEG abnormalities can be elicited by the use of triggers such as cognitive tasks and pattern stimulation during the EEG recording in selected patients. Distinct electrographic abnormalities to help classification can be identified among different electroclinical syndromes.

Sleep onset uncovers thalamic abnormalities in patients with idiopathic generalised epilepsy

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

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

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Differences are regionally specific.

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Regions connected to somatomotor/occipital cortices are consistently affected.

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

An EEG-fMRI Study on the Termination of Generalized Spike-And-Wave Discharges in Absence Epilepsy

Introduction

Different studies have investigated by means of EEG-fMRI coregistration the brain networks related to generalized spike-and-wave discharges (GSWD) in patients with idiopathic generalized epilepsy (IGE). These studies revealed a widespread GSWD-related neural network that involves the thalamus and regions of the default mode network. In this study we investigated which brain regions are critically involved in the termination of absence seizures (AS) in a group of IGE patients.

Methods

Eighteen patients (6 male; mean age 25 years) with AS were included in the EEG-fMRI study. Functional data were acquired at 3T with continuous simultaneous video-EEG recording. Event-related analysis was performed with SPM8 software, using the following regressors: (1) GSWD onset and duration; (2) GSWD offset. Data were analyzed at single-subject and at group level with a second level random effect analysis.

Results

A mean of 17 events for patient was recorded (mean duration of 4.2 sec). Group-level analysis related to GSWD onset respect to rest confirmed previous findings revealing thalamic activation and a precuneus/posterior cingulate deactivation. At GSWD termination we observed a decrease in BOLD signal over the bilateral dorsolateral frontal cortex respect to the baseline (and respect to GSWD onset). The contrast GSWD offset versus onset showed a BOLD signal increase over the precuneus-posterior cingulate region bilaterally. Parametric correlations between electro-clinical variables and BOLD signal at GSWD offset did not reveal significant effects.

Conclusion

The role of the decreased neural activity of lateral prefrontal cortex at GSWD termination deserve future investigations to ascertain if it has a role in promoting the discharge offset, as well as in the determination of the cognitive deficits often present in patients with AS. The increased BOLD signal at precuneal/posterior cingulate cortex might reflect the recovery of neural activity in regions that are “suspended” during spike and waves activity, as previously hypothesized.

Are Absence Epilepsy and Nocturnal Frontal Lobe Epilepsy System Epilepsies of the Sleep/Wake System?

System epilepsy is an emerging concept interpreting major nonlesional epilepsies as epileptic dysfunctions of physiological systems. I extend here the concept of reflex epilepsy to epilepsies linked to input dependent physiological systems. Experimental and clinical reseach data were collected to create a coherent explanation of underlying pathomechanism in AE and NFLE. We propose that AE should be interpreted as epilepsy linked to the corticothalamic burst-firing mode of NREM sleep, released by evoked vigilance level oscillations characterized by reactive slow wave response. In the genetic variation of NFLE the ascending cholinergic arousal system plays an essential role being in strong relationship with a gain mutation of the nicotinic acethylcholin receptors, rendering the arousal system hyperexcitable. I try to provide a more unitary interpretation for the variable seizure manifestation integrating them as different degree of pathological arosuals and alarm reactions. As a supporting hypothesis the similarity between arousal parasomnias and FNLE is shown, underpinned by overlaping pathomechanism and shared familiarity, but without epileptic features. Lastly we propose that both AE and NFLE are system epilepsies of the sleep-wake system representing epileptic disorders of the antagonistic sleep/arousal network. This interpretation may throw new light on the pathomechanism of AE and NFLE.

A new model to study sleep deprivation-induced seizure

BACKGROUND AND STUDY OBJECTIVES

A relationship between sleep and seizures is well-described in both humans and rodent animal models; however, the mechanism underlying this relationship is unknown. Using Drosophila melanogaster mutants with seizure phenotypes, we demonstrate that seizure activity can be modified by sleep deprivation.

DESIGN

Seizure activity was evaluated in an adult bang-sensitive seizure mutant, stress sensitive B (sesB(9ed4)), and in an adult temperature sensitive seizure mutant seizure (sei(ts1)) under baseline and following 12 h of sleep deprivation. The long-term effect of sleep deprivation on young, immature sesB(9ed4) flies was also assessed.

SETTING

Laboratory.

PARTICIPANTS

Drosophila melanogaster.

INTERVENTIONS

Sleep deprivation.

MEASUREMENTS AND RESULTS

Sleep deprivation increased seizure susceptibility in adult sesB(9ed4)/+ and sei(ts1) mutant flies. Sleep deprivation also increased seizure susceptibility when sesB was disrupted using RNAi. The effect of sleep deprivation on seizure activity was reduced when sesB(9ed4)/+ flies were given the anti-seizure drug, valproic acid. In contrast to adult flies, sleep deprivation during early fly development resulted in chronic seizure susceptibility when sesB(9ed4)/+ became adults.

CONCLUSIONS

These findings show that Drosophila is a model organism for investigating the relationship between sleep and seizure activity.

How sleep activates epileptic networks?

Background. The relationship between sleep and epilepsy has been long ago studied, and several excellent reviews are available. However, recent development in sleep research, the network concept in epilepsy, and the recognition of high frequency oscillations in epilepsy and more new results may put this matter in a new light. Aim. The review address the multifold interrelationships between sleep and epilepsy networks and with networks of cognitive functions. Material and Methods. The work is a conceptual update of the available clinical data and relevant studies. Results and Conclusions. Studies exploring dynamic microstructure of sleep have found important gating mechanisms for epileptic activation. As a general rule interictal epileptic manifestations seem to be linked to the slow oscillations of sleep and especially to the reactive delta bouts characterized by A1 subtype in the CAP system. Important link between epilepsy and sleep is the interference of epileptiform discharges with the plastic functions in NREM sleep. This is the main reason of cognitive impairment in different forms of early epileptic encephalopathies affecting the brain in a special developmental window. The impairment of cognitive functions via sleep is present especially in epileptic networks involving the thalamocortical system and the hippocampocortical memory encoding system.

Neurophysiology of juvenile myoclonic epilepsy

Juvenile myclonic epilepsy (JME) can be firmly diagnosed by a careful interview of the patient focusing on the seizures and by the EEG with the help, if necessary, of long-term video-EEG monitoring using sleep and/or sleep deprivation. Background activity is normal. The interictal EEG shows diffuse or generalized spike-wave (SW) and polyspike-wave (PSW) discharges. In some patients, non-specific changes or misleading features such as focal changes are found. Changes are mostly seen at sleep onset and at awakening. Provoked awakenings are more likely to activate interictal paroxysmal abnormalities than spontaneous awakenings. The presence of a photoparoxysmal response with or without myoclonic jerks (MJ) is common (30% of the cases). Myoclonic jerks are associated with a discharge of fast, irregular, generalized PSWs that predominate anteriorly. Myoclonic jerks appear to be associated with rhythmic EEG (spike) potentials at around 20Hz. These frequencies are in the range of movement-related fast sensorimotor cortex physiological rhythms. The application of jerk-locked averaging technique has provided findings consistent with a cortical origin of MJ. Paired TMS (transcranial magnetic stimulation) studies showed a defective intracortical inhibition, due to impaired GABA-A mediated mechanisms. In this review, we present the EEG characteristics of JME with particular emphasis on the pathophysiology of MJ and on the role of sleep deprivation on interictal and ictal changes.

Usefulness of a simple sleep-deprived EEG protocol for epilepsy diagnosis in de novo subjects

OBJECTIVE

In case series concerning the role of EEG after sleep deprivation (SD-EEG) in epilepsy, patients' features and protocols vary dramatically from one report to another. In this study, we assessed the usefulness of a simple SD-EEG method in well characterized patients.

METHODS

Among the 963 adult subjects submitted to SD-EEG at our Center, in the period 2003-2010, we retrospectively selected for analysis only those: (1) evaluated for suspected epileptic seizures; (2) with a normal/non-specific baseline EEG; (3) still drug-free at the time of SD-EEG; (4) with an MRI analysis; (5) with at least 1 year follow-up. SD-EEG consisted in SD from 2:00 AM and laboratory EEG from 8:00 AM to 10:30 AM. We analyzed epileptic interictal abnormalities (IIAs) and their correlations with patients' features.

RESULTS

Epilepsy was confirmed in 131 patients. SD-EEG showed IIAs in 41.2% of all patients with epilepsy, and a 91.1% specificity for epilepsy diagnosis; IIAs types observed during SD-EEG are different in generalized versus focal epilepsies; for focal epilepsies, the IIAs yield in SD-EEG is higher than in second routine EEG.

CONCLUSIONS

This simple SD-EEG protocol is very useful in de novo patients with suspected seizures.

SIGNIFICANCE

This study sheds new light on the role of SD-EEG in specific epilepsy populations.

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.

Controversial issues on EEG after sleep deprivation for the diagnosis of epilepsy

EEG after sleep deprivation (SD-EEG) is widely used in many epilepsy centers as an important tool in the epilepsy diagnosis process. However, after more than 40 years of use, there are a number of issues which still need to be clarified concerning its features and role. In particular, the many scientific papers addressing its role in epilepsy diagnosis often differ remarkably from each other in terms of the type of patients assessed, their description and study design. Furthermore, also the length and the type of EEG performed after SD, as well as the length of SD itself, vary dramatically from one study to another. In this paper we shortly underscore the abovementioned differences among the different reports, as well as some interpretations of the findings obtained in the different studies. This analysis emphasizes, if needed, how SD-EEG still represents a crucial step in epilepsy diagnosis, and how additional, controlled studies might further shape its precise diagnostic/prognostic role.

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.

Modern electroencephalography

Electroencephalography (EEG) has been in continuous development over at least 70 years and is firmly established as a tool in the management of epilepsy. For a while, the technique fell into disregard because of difficulties with interpretation, specificity and sensitivity. Whilst clinicians have to be aware of these problems, they have been largely addressed by recent computer digitization of signals, which permits longer standard recordings and monitoring linked to a simultaneous video. These techniques are not only an essential component of a specialist epilepsy service, where inpatient video-EEG telemetry is vital both for diagnosis and assessment before neurosurgical treatment, but also in general and acute medical settings, particularly for the management of status epilepticus. Further developments in computing will extend the use of EEG in all of these roles and long-term monitoring for diagnosis and management of coma will become more widely available.

EEG-fMRI validation studies in comparison with icEEG: a review

Simultaneous EEG-fMRI is a non-invasive investigation technique developed to localize the generators of interictal epileptiform discharges (IED) in patients with epilepsy. Although the value of EEG-fMRI in epilepsy presurgical evaluation is being assessed clinically, its utility is still controversial. In this review, we considered EEG-fMRI applications in epilepsy presurgical evaluation with a focus on validation studies that compared the results of EEG-fMRI with those of the current "gold standard" intracranial EEG (icEEG) in order to assess its utility of seizure focus localization and the possibility for EEG-fMRI to reduce the need for invasive techniques such as icEEG. Since the advances of EEG-fMRI partially rely on the maturation of its data analysis, we also reviewed the methodological developments in EEG-fMRI analysis. It is possible that combining with other neuroimaging modalities such as MEG/MSI and ESI, EEG-fMRI may play a greater role in epilepsy presurgical evaluation.

The electroencephalogram of idiopathic generalized epilepsy

Idiopathic generalized epilepsy (IGE) is classified into several subsyndromes based on clinical and electroencephalography (EEG) features. The EEG signature of IGE is bisynchronous, symmetric, and generalized spike-wave complex; although focal, irregular, and so called "fragments" of discharges are not uncommon. Other characteristic EEG features include polyspikes, polyspike-wave discharges, occipital intermittent rhythmic delta activity, and photoparoxysmal response. Both human and animal data suggest involvement of the thalamus and the cortex in the generation of spike-wave discharges in IGE. Circadian variations of generalized epileptiform discharges are well described, and these can be useful in diagnostic confirmation. Those discharges tend to occur more often after awakening and during cyclic alternating pattern phase-A of non-rapid eye movement sleep. Activation procedures such as hyperventilation, intermittent photic stimulation, eye closure, and fixation-off are useful techniques to increase the yield of both interictal and ictal EEG abnormalities. Although not in routine use, specific triggers such as pattern stimulation and cognitive tasks may also be of value in eliciting rare reflex seizure-related EEG abnormalities. Variations of EEG abnormalities are evident between different electroclinical syndromes. EEG is also affected by certain external as well as internal factors, which should be borne in mind when interpreting EEG studies in IGE.

The complementary value of sleep-deprived EEG in childhood onset epilepsy

BACKGROUND

Although EEG is an important diagnostic tool in suspected childhood onset epilepsy, as many as 50% of wakefulness records remain normal. Sleep-deprived EEG has been reported in adults to serve as an activator of epileptic discharges but such effect is still not agreed upon in children reporting small series.

PURPOSE

Assess the complementary diagnostic value of sleep deprivation on the induction of epileptic discharges in childhood onset epilepsy having a normal awake record within a period of 5 years. EEG recording was performed during the awake, drowsiness and sleep states following sleep deprivation of 6h. BACKGROUND RESULTS: Fifty five children of whom the initial record failed to detect epileptiform discharges, were assessed at age 5-17 years (mean: 10+/-3.7), 27 boys and 28 girls. Sleep occurred in 51 (92.7%) after sleep deprivation and in only 1 (1.8%) during an awake record. Epileptic discharges were detected in 15 of 55 (27.2%) previous non-epileptic awake records during the sleep-deprived EEG either during wakefulness and more frequent during sleep. Eight abnormal records were detected in 18 (44%) children presenting with a focal seizure and 7 of 35 (20%) associated with generalized seizures. Epileptic discharges were recorded mainly and more frequent during sleep.

CONCLUSIONS

Our data suggests that sleep deprivation imposes an apparent activating impact uncovering epileptic discharges children corroborating with overt clinical seizures even beyond the sampling effect of repeat records.

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.

Idiopathic generalized epilepsies: clinical and electroencephalogram diagnosis and treatment

This review concentrates on the principles of the clinical and electroencephalogram diagnosis of idiopathic generalized epilepsies and their treatment. The electroclinical variability of the main seizure types is detailed and particular emphasis is placed on the differential diagnosis from other seizures and nonepileptic conditions that is essential for the optimal management of these patients. The authors review the various idiopathic generalized epilepsy subsyndromes and conditions that are included in both the 1989 International League Against Epilepsy classification system and the recently proposed International League Against Epilepsy scheme, but also syndromes and forms that have not been formally recognized. Finally, the authors describe the principles of antiepileptic drug treatment with the old and newer drugs, and their specific indications and contraindications in the various syndromes and seizure types.

Use and Abuse of EEG in the Diagnosis of Idiopathic Generalized Epilepsies

This article concentrates on the role of electroencephalograms (EEGs) in the diagnosis and management of patients with idiopathic generalized epilepsies (IGEs). We review the morphologic and behavioral characteristics of the interictal and ictal EEG markers of IGE that should guide recording strategies to augment its diagnostic yield, and we attempt to delineate those particular features that may be relevant to different IGE syndromes. We also explore the electrographic boundaries between IGEs and cryptogenic/symptomatic generalized and focal epilepsies, and focal/secondary generalized epilepsies, with particular relevance to the phenomena of focal abnormalities and secondary bilateral synchrony, commenting on possible diagnostic pitfalls and areas of uncertainty.

K-complex, a reactive EEG graphoelement of NREM sleep: an old chap in a new garment

This review summarises data gathered on the KC phenomenon over the past 70 yr. The following issues are discussed: definitions, morphology and topography of KC, the regular participation in NREM sleep, elicitability features of evoked KC, autonomic and motor concomitants, relationship of KC with information processing during NREM sleep, relationship of KC and deltas of NREM sleep, and relationship of KC with sleep cyclicity. KC is a complex multifunctional phenomenon of the sleeping brain involved in information processing and defence against the arousal effect of sensory stimuli. To put the old chap in a new garment, the relationship of KC with synchronisation-type and desynchronisation-type micro-arousals, and the 'cyclic alternating pattern', will be discussed, with an emphasis on the sleep-protecting role of KC and synchronisation-type answers in sleep regulation executed by phasic events. Lastly, the role of KC providing gating functions in idiopathic generalized epilepsies and other, different, sleep disorders are characterised. A 'theoretical epilogue' is appended to show some system theoretical and regulational aspects.

[EEG recording after sleep deprivation in a series of patients with juvenile myoclonic epilepsy]

Seizures in Juvenile Myoclonic Epilepsy (JME) are dependent on the sleep-wake cycle and precipitant factors, among which sleep deprivation (SD) is one of the most important. Still an under diagnosed syndrome, misinterpretation of the EEGs contributes to diagnostic delay. Despite this, a quantitative EEG investigation of SD effects has not been performed. We investigated the effect of SD on EEGs in 41 patients, aged 16-50 yr. (mean 25.4), who had not yet had syndromic diagnosis after a mean delay of 8.2 yr. Two EEG recordings separated by a 48-hour interval were taken at 7 a.m. preceded by a period of 6 hours of sleep (routine EEG) and after SD (sleep-deprived EEG). The same protocol was followed and included a rest wakefulness recording, photic stimulation, hyperventilation and a post-hyperventilation period. The EEGs were analyzed as to the effect of SD on the number, duration, morphology, localization and predominance of abnormalities in the different stages. A discharge index (DI) was calculated. Out of the 41 patients, 4 presented both normal EEG recordings. In 37 (90.2%) there were epileptiform discharges (ED). The number of patients with ED ascended from 26 (70.3%) in the routine EEG to 32 (86.5%) in the sleep-deprived exam. The presence of generalized spike-wave and multispike-wave increased from 20 (54.1%) and 13 (35.1%) in the first EEG to 29 (78.4%) and 19 (51.4%) in the second, respectively (p<0.05 and p<0.01). As to localization, the number of generalized, bilateral and synchronous ED increased from 21 (56.8%) to 30 (81.1%) (p<0.01). The DI also increased; while 8 patients (21.6%) presented greater rate in the routine EEG, 25 (67.6%) did so in the sleep-deprived EEG mainly during somnolence and sleep (p<0.01). Moreover, the paroxysms were also longer in the sleep-deprived EEG. Sleep-deprived EEG is a powerful tool in JME and can contribute significantly to the syndromic characterization of this syndrome.

Comparison of clonidine to sleep deprivation in the potential to induce spike or sharp-wave activity

OBJECTIVE

This study aimed to investigate previously observed side effects, i.e. increased epileptic activity during clonidine medication. The safety and effectiveness of clonidine as spike inducing agent compared to sleep deprivation were tested.

METHODS

Patients suffering from drug-resistant localization related epilepsy took part in 3 magnetoencephalography (MEG) sessions. One session was recorded without any activating measures. The other two sessions were either performed after sleep deprivation or after medication with clonidine. Target parameter was the number of spikes or sharp-waves during a 30 min recording period.

RESULTS

About 67% of the patients showed increased spike activity after clonidine, whereas sleep deprivation increased the number of spikes in 33%, and 29% of the patients did not show any activation at all. Clonidine was most effective in temporal lobe epilepsy, when the focus was located in the right hemisphere, and when clonidine serum concentrations were ranging between 0.6 and 1.0 ng/ml.

CONCLUSIONS

This study showed for the first time that clonidine can be considered an effective spike or sharp-wave inducing drug that is superior to the potency of sleep deprivation.

SIGNIFICANCE

The administration of clonidine increases the probability of recording ictal and interictal epileptic activity during limited acquisition time.

Factors affecting spiking related to sleep and wake states in temporal lobe epilepsy (TLE)

The aim of the study was to investigate the influence of different clinical factors on spiking during sleep and wakefulness in temporal lobe epilepsy. The study included 38 temporal lobe epilepsy (TLE) patients who underwent long-term electroencephalography (EEG) monitoring. In addition to traditional sleep scoring, waking was subdivided into eyes opened (WEO) and eyes closed (WEC) states. The following spike measures were investigated: spiking rates for each state, mean spike rate, spiking stability across wake and sleep states and relative spike density for each state. These measures were investigated according to clinical variables, such as age, age at epilepsy onset, duration of epilepsy, seizure frequency, the presence of secondarily generalised tonic-clonic (SGTC) seizures and the data on epileptogenic lesions based on MRI. Spiking rates during most states and spiking stability showed a significant positive correlation with epilepsy duration. Relative spike density during sleep stage NREM3,4 significantly increased with age at epilepsy onset. Relative spike density during WEC was significantly higher in the presence of hippocampal sclerosis (HS). Spiking rate during REM was significantly higher if a patient had SGTC seizures. Our data provide evidence that different aspects of spiking are associated with different aspects of TLE. We suggest that spike behaviour analysis offer new aspects both for diagnosis and research.