Continuous focal spikes during REM sleep in a case of acquired aphasia (Landau-Kleffner syndrome)

Rapid eye movement sleep affects interictal epileptic activity differently in mesiotemporal and neocortical areas

OBJECTIVE

Rapid eye movement (REM) sleep reduces the rate and extent of interictal epileptiform discharges (IEDs). Breakthrough epileptic activity during REM sleep is therefore thought to best localize the seizure onset zone (SOZ). We utilized polysomnography combined with direct cortical recordings to investigate the influences of anatomical locations and the time of night on the suppressive effect of REM sleep on IEDs.

METHODS

Forty consecutive patients with drug-resistant focal epilepsy underwent combined polysomnography and stereo-electroencephalography during presurgical evaluation. Ten-minute interictal epochs were selected 2 h prior to sleep onset (wakefulness), and from the first and second half of the night during non-REM (NREM) sleep and REM sleep. IEDs were detected automatically across all channels. Anatomic localization, time of night, and channel type (within or outside the SOZ) were tested as modulating factors.

RESULTS

Relative to wakefulness, there was a suppression of IEDs by REM sleep in neocortical regions (median = -27.6%), whereas mesiotemporal regions showed an increase in IEDs (19.1%, p = .01, d = .39). This effect was reversed when comparing the regional suppression of IEDs by REM sleep relative to NREM sleep (-35.1% in neocortical, -58.7% in mesiotemporal, p < .001, d = .39). Across all patients, no clinically relevant novel IED regions were observed in REM sleep versus NREM or wakefulness based on our predetermined thresholds (4 IEDs/min in REM, 0 IEDs/min in NREM and wakefulness). Finally, there was a reduction in IEDs in late (NREM: 1.08/min, REM: .61/min) compared to early sleep (NREM: 1.22/min, REM: .69/min) for both NREM (p < .001, d = .21) and REM (p = .04, d = .14).

SIGNIFICANCE

Our results demonstrate a spatiotemporal effect of IED suppression by REM sleep relative to wakefulness in neocortical but not mesiotemporal regions, and in late versus early sleep. This suggests the importance of considering sleep stage interactions and the potential influences of anatomical locations when using IEDs to define the epileptic focus.

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.

The value of rapid eye movement sleep in the localization of epileptogenic foci for patients with focal epilepsy

PURPOSE

Our aim was to investigate the value of rapid eye movement (REM) during prolonged scalp video-electroencephalography (VEEG) in the localization of epileptogenic foci for patients with focal epilepsy.

METHOD

We retrospectively studied a total of 59 patients with focal epilepsy and 31 of 59 received surgery. We assessed localization of interictal epileptiform discharges (IEDs) during REM, non-rapid eye movement sleep (NREM) and wakefulness to compare with the localization of ictal EEG, clinical semiology, magnetic resonance imaging (MRI) and positron emission tomography (PET) and stereo-electroencephalogram (SEEG). We graded postoperative follow-up outcome according to Engel criteria to further verify the accuracy of localization of epileptogenic foci in REM-IEDs. NREM-IEDs and Wakefulness-IEDs. Stepwise multiple logistic regression was carried out to assess for independent association of good prognosis with REM accurate localization, temporal lobe epilepsy and MRI accurate localization.

RESULTS

Clinical semiology was concordant to REM-IEDs in 40 patients (72.7 %), NREM-IEDs in 27 (49.1 %), and Wakefulness-IEDs in 25 (45.5 %). MRI lesion was concordant with REM-IEDs in 35 patients (81.4 %), Wakefulness-IEDs in 26 (60.5 %), and NREM-IEDs in 25 (58.1 %). PET localization was concordant with REM-IEDs in 20 patients (76.9 %), Wakefulness-IEDs and NREM-IEDs in 11 (42.3 %). SEEG localization was concordant with REM-IEDs in 15 patients (65.2 %), Wakefulness-IEDs in 10 (43.5 %), and NREM-IEDs in 8 (34.8 %). Thirty-one patients received surgery, and 30 (96.8 %) of them achieved good seizure control (Engel I-III). The surgical site was concordant with REM-IEDs in 23 (74.2 %), Wakefulness-IEDs and NREM-IEDs in 14 (45.2 %). In addition, the accuracy of REM-IEDs localization in temporal epilepsy (90 %) was higher than that extra-temporal epilepsy (45.5 %). REM accurate localization of epileptogenic foci was an independent factor contributing to good prognosis (P = 0.025, OR = 12.368).

CONCLUSIONS

Compared with NREM-IEDs and Wakefulness-IEDs, REM-IEDs had most value for localization of epileptogenic foci in patients with focal epilepsy. REM-IEDs- accurate localization of epileptogenic foci was an independent factor contributing to good prognosis for postsurgical patients with focal epilepsy.

REM-sleep related hypermotor seizures: Video documentation and ictal source imaging

INTRODUCTION

Rapid eye movement (REM) sleep has an inhibitory effect on epileptiform EEG discharges, and seizures occur extremely rarely in REM sleep.

CASE STUDY

We present the case and video recordings of a 10-year-old boy, with sleep-related hypermotor seizures starting from REM sleep, identified from videoEEG recordings. The semiology comprised intense fear, tachycardia, tachypnea, followed by hypermotor manifestations. Further investigations included brain MRI and source localization of the EEG signals. Multiple antiepileptic drugs were tried, the patient obtaining a good control of the seizures in the last 2.5 years with eslicarbazepine.

DISCUSSION AND CONCLUSION

The ictal EEG source imaging showed seizure onset in the anterior part of the right insula, with propagation to the orbitofrontal area, confirmed by the semiological sequence. Although rare, focal seizures can be triggered by REM sleep and our findings suggest that deficient maturation of brain areas involved in sleep modulation might induce insufficient desynchronization during REM sleep, thus allowing seizure emergence.

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.

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.

Changing perspectives on Landau-Kleffner syndrome

Landau-Kleffner syndrome (LKS) is a childhood disorder characterized by an acquired aphasia that emerges in association with epileptiform electroencephalographic abnormalities. The language loss is often characterized by a severe disturbance of auditory language comprehension (verbal auditory agnosia) combined with a substantial disruption of expressive language. Comorbid behavioral disturbances commonly involve hyperactivity and attentional problems but sometimes encompass a more pervasive pattern of difficulties resembling an autism spectrum disorder. Now one the most frequently described forms of acquired aphasia in children, LKS has had a profound influence on both neurological practice and cognitive neuroscience. Here, we review current conceptualizations of LKS, consider its pleomorphic manifestations and discuss existing and future diagnostic issues and dilemmas. The potential relevance of LKS to understanding other disorders, including autistic regression, is considered.

The Landau-Kleffner syndrome

Landau-Kleffner Syndrome is a rare childhood disorder which involves seizures and acquired aphasia. Anticonvulsants, or the passage of time, may control the seizures, but speech recovery is variable, and the aphasia may persist.

The Landau-Kleffner Syndrome

Landau-Kleffner syndrome (LKS), or acquired epileptiform aphasia, is an epilepsy syndrome involving progressive neuropsychological impairment related to the appearance of paroxysmal electroencephalograph (EEG) activity. LKS appears to share a common pathophysiologic mechanism with continuous spike-wave of sleep (CSWS), acquired epileptic opercular syndrome (AEOS), and even benign childhood epilepsy with centrotemporal spikes (BECTS), with differentiating factors including age of onset, area of primary epileptogenicity, and severity of clinical presentation. This article covers the clinical, diagnostic, therapeutic, and prognostic features of LKS. In a child with autistic spectrum disorder, the presence of a fluctuating clinical course or regression should raise suspicion for the presence of associated epilepsy.

Sleep-EEG modulation of interictal epileptiform discharges in adult partial epilepsy: a spectral analysis study

INTRODUCTION

In order to define accurately the relationship between EEG components (spindles, delta and theta frequencies) and the occurrence of interictal epileptiform discharges (IED) during sleep in partial epilepsy, a correlation study between spike overnight distribution and EEG spectral power time series was performed.

METHODS

Eighteen patients (mean age: 24.7+/-5.5 years) affected by partial epilepsy underwent continuous EEG-polysomnography. The temporal series of Slow Wave Activity (SWA), Sigma Activity (SA) and Theta Band (TB), derived from spectral analysis, were obtained from a spike-free and pathologic alteration-free derivation, contralateral to the most active lead, where the IED count was performed. Relationships between SA, SWA and TB and time series of IED were tested by means of correlation techniques after data normalization.

RESULTS

Our results revealed a significantly higher correlation between IED and SWA in 12 subjects; a significantly higher correlation between IED and SA in three subjects and a significant correlation with TB in three cases.

CONCLUSIONS

Data suggest that in most adult patients with partial epilepsy IED production during sleep is facilitated by the action of synchronizing mechanisms which are active during NREM sleep and lead to the appearance of EEG delta waves. Nevertheless evidence is given of two smaller groups of patients. In one of them IED are more sensitive to the promoting action of the spindle generating mechanism, active during stage 2 of NREM sleep. In the other one the promoting action of TB, characterizing EEG during stage 1 and REM sleep, is evident.

Spindles-inducing mechanism modulates sleep activation of interictal epileptiform discharges in the Landau-Kleffner syndrome

PURPOSE

Landau-Kleffner syndrome (LKS) is characterized by a marked increase of interictal epileptiform discharges (IEDs) during sleep. During nonrapid eye movement (NREM) sleep, neuronal membrane potential oscillations lead to the appearance of spindles and delta waves in the surface EEG and might develop into paroxysmal synchronization. Spectral analysis allows the quantitative description of the dynamics of delta (slow-wave activity, SWA, 0.5-4.5 Hz) and sigma activity (SA, 12.0-16.0 Hz) and can be used to assess the relation between SA, SWA, and IEDs during sleep.

METHODS

We performed six overnight continuous EEG-polysomnographic studies in three patients with LKS. The temporal series of SWA and SA were obtained from a spike-free derivation lead. The IEDs count was performed on the most active lead. Relations between sigma and SWA and time series of IEDs were tested by means of correlation techniques after data normalization.

RESULTS

Our results revealed a significantly higher correlation between IEDs and SA with respect to SWA in all the subjects, in total sleep time. The same analysis limited to NREM sleep highlights the better correlation between SA and IEDs.

CONCLUSIONS

Our data suggest that neural mechanisms involved in the generation of sleep spindles facilitate IEDs production in LKS.

Landau-Kleffner syndrome (LKS): long-term follow-up and links with electrical status epilepticus during sleep (ESES)

We describe 11 patients affected by Landau-Kleffner syndrome (LKS) with a mean follow-up of 9 years and 8 months. EEG recordings during wakefulness, NREM and REM sleep showed a bitemporal electrical status epilepticus during sleep (BTESES) in all cases; four of them presented a shift from a BTESES towards an 'intercalated electrical status epilepticus during sleep' (IESES) accompanied by a global regression of cognitive and behavioural functions in 3/4 of cases. At the last observation, only 18.2% of cases presented a complete language recovery and mental retardation was evident in 63.6%. The prognosis of LKS in our cases may depend on the interaction of different negative factors such as onset of aphasia before 4 years, its duration for longer than 1 year, long-lasting duration and continuity without fluctuations of BTESES/IESES, probably preexisting mild speech delay. It is important for the prognosis to utilize antiepileptic treatment and possibly neurosurgical techniques to eliminate EEG paroxysmal abnormalities. At present, no similar cases with clinical-EEG evolution from LKS to electrical status epilepticus during sleep (ESES) have ever been described. Our observation demonstrates that LKS and ESES classified as different clinical-EEG syndromes represent two aspects of the same brain dysfunction and they may exist separately or pass one into the other with a change in the clinical-EEG picture. The common origin of the two syndromes is confirmed by recent functional brain imaging, neurophysiological and neurosurgical techniques.

[Continuous spike-wave activity during sleep. Electroencephalographic and clinical features]

Seventeen children were retrospectively evaluated. They exhibited continuous spike-wave activity during slow wave sleep (CSWS). Five of these had only speech problems and seizures (Landau-Kleffner syndrome) (group 1). The other cases had developmental milestones acquisition delay and/or mental retardation (group 2). Epileptic seizures were present in 11 of these, tetraparesis was observed in 5, hemiparesis in 2, microcephaly in 2 and behavior disturbances in 4 cases. The electroencephalogram showed in all cases diffuse CSWS. Group 1 showed diffuse activity, at times accentuated in the centrotemporal region (4/5). Group 2 had widespread discharges, including multifocal activity (5/12), sometimes with anterior predominance (7/12). We concluded that CSWS is a non specific electrographic pattern observed in some types of epilepsy in childhood that have different clinical presentation. It has however some topographic differentiation, depending upon the lesional sites.

The Landau-Kleffner syndrome: increased understanding

The Landau-Kleffner and the continuous spike and wave discharges during slow sleep (CSWS) syndromes are described and possible links between the two are discussed. They certainly overlap, with clinical and electroencephalographic features in common. Potential causes are discussed. There is seldom a definite reason for the seizures but it way well be that the spike and wave discharges seen in the EEG, whatever their origin, may disrupt the development of language and cognitive function at a critical stage. If neurons and axons are involved in this disorganized activity they surely cannot perform normally. The evidence that these discharges in the Landau-Kleffner syndrome can have a focal origin in areas important for language supports this hypothesis. Certain variations among studies quoted may be due to factors such as age of onset, the duration of the paroxysmal activity, its intensity and especially its localization. Also, if development has been distorted subsequent progress is likely to be disturbed after the primary condition has ceased to exist. The diagnosis can sometimes present difficulties, for example from deafness, psychiatric condition, post-ical dysphasia and from progressive degenerative neurological disorders. If the possible role of the epileptic activity is accepted, there are strong reasons for advocating anti-epileptic treatment, even if overt seizures are rare. The response to drugs is varied. Fits will usually stop, but not so often the spike and wave discharges, and it is justifiable to try various regimes. Subpial resection has been reported to be successful, possibly by preventing the cortex generating seizures, and their spread.

Acquired epileptiform aphasia

The acquired epileptiform aphasias, with Landau-Kleffner's syndrome as the example, represent an important group of syndromes in our quest to understand the relationship between epilepsy, language, and behavior. The controversy that truly frames the literature on the acquired epileptiform aphasias is the role of epileptiform activity on language, behavior, and cognition. This review expands the model of Landau-Kleffner's syndrome to include two other encephalopathies with language and behavioral regression in association with an epileptiform electroencephalogram. Both of these encephalopathies, autistic epileptiform regression and disintegrative epileptiform regression, are associated with an acquired language disorder. The developmental period in which the acquired language disorder begins, the type of language disorder, and the location and type of the epileptiform activity are all important variables that may affect clinical manifestations and prognosis.

Sleep and the epilepsies

To review the numerous works concerning sleep and epilepsy, this review considers the effects of sleep, firstly on seizures and secondly on paroxysmal interictal EEG activity (PA), in the different types of epilepsy according to the International League against Epilepsy classification. Apart from the exceptions of the definite nocturnal preponderance of seizures in idiopathic rolandic epilepsy and of the mostly nocturnal occurrence of seizures in some types of familial or sporadic frontal-lobe epilepsy, assessing a seizure according to the time of day it occurs is of no diagnostic or predictive value. In generalised idiopathic epilepsy, as in partial symptomatic or cryptogenic epilepsy, only about 20% of the patients had a sleep increase in PA. This percentage is higher (75%) in idiopathic partial epilepsy. Stereoelectroencephalography demonstrates a relative stability of spiking within the focus across the states of vigilance and an increase in transmitted discharges during stages 3 and 4. In the Landau and Kleffner syndrome, as in the syndromes of continuous spike-waves during sleep, there is a huge, unexplained increase in PA during sleep. The neuropsychological consequences of this PA have some relationship with their localisation and the patient's age at the time of occurrence. Sleep PA has also been reported in several groups of non-epileptic subjects. As regards the effect of epilepsy on sleep, sleep may be lighter and abnormally discontinuous in the absence of seizures, particularly in temporal-lobe epilepsy.

Effect of seizures and epileptiform discharges on cognitive function

Several relationships have been obtained between cognitive impairment and epilepsy-related or treatment-related factors. One of these factors is treatment-related: the central cognitive side effects of the antiepileptic drugs (AEDs). The second and third factors are disease-related factors, i.e., the effect of the seizures and underlying epileptiform discharges in the brain and the localization of the epileptogenic focus in specific areas of the brain. Although most cognitive problems have a multifactorial origin and often several factors combined are responsible for the "make-up" of a cognitive problem, we have attempted to isolate one factor: the effect of seizures and epileptiform EEG discharges on cognitive function. Several studies show the impact of ictal activity, but special attention is required for the postictal and interictal effects of epilepsy on cognitive functions. This may explain substantial cognitive impairments in children with subclinical epileptiform discharges or with infrequent subtle seizures.

Correlation between CSWS and aphasia in Landau-Kleffner syndrome: a study of three cases

We report three typical cases of Landau-Kleffner syndrome with varied courses. The very frequent discharges in sleep EEGs, often showing the patterns of CSWS (continuous spike-waves during slow-wave sleep), either typical (spike-wave complex occupying over 85% of slow-wave sleep duration) or atypical (spike-waves occupying less than 85% of slow-wave sleep), were presented in all our cases. The CSWS seems correlated with aphasia in our cases. Since the disappearance of CSWS might be indicative of a lagged improvement in aphasia, we suggest that sufficiently long-term treatment with anticonvulsants and/or corticosteroids is worthwhile, if the EEG is improved significantly by this treatment.

Alternative epilepsy therapies: the ketogenic diet, immunoglobulins, and steroids

Despite the continued development and release of new antiepileptic drugs (AEDs), many children have seizures that do not respond to conventional therapy or have related side effects that preclude continued use. While some of these children are surgical candidates, the majority do not qualify for surgical resection. In these children alternative therapies are often considered by desperate physicians and parents. Three of the less conventional therapies which are currently used for intractable epilepsy are: the ketogenic diet, immunoglobulins, and steroids. None of these therapies has been adequately studied and it remains unclear which patients may benefit or be harmed by these therapies. Despite the lack of scientific vigor in evaluating these therapies, the television and print media has proclaimed these therapies as miraculous, yet grossly under-utilized by an ignorant medical community. The ketogenic diet has been demonstrated to reduce seizure frequency in some patients, but has an unclear mechanism of action, while immunoglobulins have both unknown efficacy and an unknown mechanism of action. While steroids are accepted as an effective therapy for infantile spasms, their role in the treatment of the Landau-Kleffner syndrome is far less clear. Although the ketogenic diet, immunoglobulins, and steroids may have a role in the treatment of severe childhood epilepsy, all three therapies need to be critically evaluated in regard to efficacy, mechanism of action, and safety.

Possible involvement of an endogenous benzodiazepine receptor ligand of the inverse agonist type in the regulation of rapid-eye movement (REM) sleep: an hypothesis

1. Rapid-eye movement (REM) sleep is a complex behavioral state characterized by desynchronized electroencephalographic (EEG) activity, postural atonia, rapid, saccadic movements of the eyes, and vivid dreaming. 2. A recently developed class of drugs, the inverse agonist beta-carboline-3-carboxylates, elicits a number of effects similar to the properties of REM sleep, such as desynchronized cortical EEG and penile erections. 3. The hypothesis is put forth that an endogenous beta-carboline-3-carboxylate exists which may initiate many aspects of REM sleep. 4. Clinical relevance of this hypothesis is discussed with regard to REM anxiety dreams, night terrors, narcolepsy, and depression.

Syndromes of acquired epileptic aphasia and epilepsy with continuous spike-waves during sleep: models for prolonged cognitive impairment of epileptic origin

Neuropsychological deficits are the common "hallmark" of acquired epileptic aphasia and epilepsy with continuous spike-waves during sleep. Findings from various sources (eg, clinical cases, electrophysiological and positron emission tomography studies) indicate that the aphasia or the behavioral and intellectual deterioration are closely linked to a particular sustained focal epileptic activity. This leads to a wider concept of prolonged cognitive impairment of epileptic origin.

Landau-Kleffner syndrome with continuous spikes and waves during slow-wave sleep

The Landau-Kleffner syndrome is sometimes associated with continuous spike-waves during slow-wave sleep. The clinical significance of this association is unclear. In order to investigate differences in glucose metabolic patterns between awake and sleep states in two children with Landau-Kleffner syndrome and continuous spike-waves during slow-wave sleep, fluorodeoxyglucose positron-emission tomographic (PET) studies were performed in each state. In the first patient, the awake interictal PET study revealed moderate hypometabolism in the thalamus and frontal and temporal cortex and mild hypometabolism in the parietal and anterior cingulate cortex bilaterally. Occipital cortex was severely hypometabolic bilaterally. In a repeat PET study performed during sleep in which continuous spike-waves during slow-wave sleep were present, the only difference noted compared to the awake study was a marked bilateral increase in temporal cortex metabolism. The awake interictal PET in the second child was normal, except for mildly increased relative glucose metabolism in the left inferior temporal cortex. The sleep PET study with continuous spike-waves during slow-wave sleep in this child showed hypermetabolism in both temporal lobes; however, this was more pronounced, with a wider distribution in the left temporal cortex. In normal subjects, PET studies performed during awake and sleep states have not revealed such differences. Whether the temporal lobes are involved in the generation of continuous spike-waves during slow-wave sleep remains to be confirmed in a larger group of patients. The first child was treated surgically with multiple subpial transection, following which continuous spike-waves during slow-wave sleep disappeared and language function improved.(ABSTRACT TRUNCATED AT 250 WORDS)

[Sleep and intra-ictal epileptic electroencephalographic activities]

From this review it appears that the slow wave sleep (SWS) increases the mean density of electroencephalographic paroxysmal activities (PA) whatever the epileptic syndrome. This pattern is not marked according to a bell curve among the epileptic population: about half the patients exhibit few or no PA during SWS, 20% show an increase during waking and another 20% during SWS. Begnin epilepsy with centro-temporal spikes is associated with an important sleep PA increase. In partial epilepsy, stage 3 and 4 sleep should increase the PA transmission. In children, a large increase in PA during SWS defines the continuous spike-wave during sleep syndrome, which is also observed in the syndrome of acquired aphasia with epilepsy of Landau-Kleffner; both conditions raise the issue of the neuropsychological consequences of the sleep PA. The sleep effect on the various epileptic models is analysed, showing a mean increase in PA during SWS and during transition between sleep and waking. This evidence is in agreement with the fact that during light sleep thalamocortical loops are functioning with an oscillatory pattern which facilitates PA expression. More hypothetic is the effect of sleep on the discharge rate of epileptic focus and on the cortical diffusion of the epileptic discharges. Gaba certainly participates in the thalamic influence, but its role on PA by the cortical and brain stem inhibition is speculative. Noradrenaline and acetylcholine, implicated in waking, reduce PA activity. Interindividual variations suggest that each epileptic has his own pathological neuronal organisation in which cortex and thalamocortical connexions are variously sensitive to the neurotransmitters implicated in sleep and waking.