The circadian distribution of interictal epileptiform EEG activity

Neurostimulation for Generalized Epilepsy: Should Therapy be Syndrome-specific?

Current applications of neurostimulation for generalized epilepsy use a one-target-fits-all approach that is agnostic to the specific epilepsy syndrome and seizure type being treated. The authors describe similarities and differences between the 2 "archetypes" of generalized epilepsy-Lennox-Gastaut syndrome and Idiopathic Generalized Epilepsy-and review recent neuroimaging evidence for syndrome-specific brain networks underlying seizures. Implications for stimulation targeting and programming are discussed using 5 clinical questions: What epilepsy syndrome does the patient have? What brain networks are involved? What is the optimal stimulation target? What is the optimal stimulation paradigm? What is the plan for adjusting stimulation over time?

ECoG spiking activity and signal dimension are early predictive measures of epileptogenesis in a translational mouse model of traumatic brain injury

The latency between traumatic brain injury (TBI) and the onset of epilepsy (PTE) represents an opportunity for counteracting epileptogenesis. Antiepileptogenesis trials are hampered by the lack of sensitive biomarkers that allow to enrich patient's population at-risk for PTE. We aimed to assess whether specific ECoG signals predict PTE in a clinically relevant mouse model with ∼60% epilepsy incidence. TBI was provoked in adult CD1 male mice by controlled cortical impact on the left parieto-temporal cortex, then mice were implanted with two perilesional cortical screw electrodes and two similar electrodes in the hemisphere contralateral to the lesion site. Acute seizures and spikes/sharp waves were ECoG-recorded during 1 week post-TBI. These early ECoG events were analyzed according to PTE incidence as assessed by measuring spontaneous recurrent seizures (SRS) at 5 months post-TBI. We found that incidence, number and duration of acute seizures during 3 days post-TBI were similar in PTE mice and mice not developing epilepsy (No SRS mice). Control mice with cortical electrodes (naïve, n = 5) or with electrodes and craniotomy (sham, n = 5) exhibited acute seizures but did not develop epilepsy. The daily number of spikes/sharp waves at the perilesional electrodes was increased similarly in PTE (n = 15) and No SRS (n = 8) mice vs controls (p < 0.05, n = 10) from day 2 post-injury. Differently, the daily number of spikes/sharp waves at both contralateral electrodes showed a progressive increase in PTE mice vs No SRS and control mice. In particular, spikes number was higher in PTE vs No SRS mice (p < 0.05) at 6 and 7 days post-TBI, and this measure predicted epilepsy development with high accuracy (AUC = 0.77, p = 0.03; CI 0.5830-0.9670). The cut-off value was validated in an independent cohort of TBI mice (n = 12). The daily spike number at the contralateral electrodes showed a circadian distribution in PTE mice which was not observed in No SRS mice. Analysis of non-linear dynamics at each electrode site showed changes in dimensionality during 4 days post-TBI. This measure yielded the best discrimination between PTE and No SRS mice (p < 0.01) at the cortical electrodes contralateral to injury. Data show that epileptiform activity contralateral to the lesion site has the the highest predictive value for PTE in this model reinforcing the hypothesis that the hemisphere contralateral to the lesion core may drive epileptogenic networks after TBI.

Epilepsy with eyelid myoclonias (Jeavons syndrome): An electro-clinical study of 40 patients from childhood to adulthood

PURPOSE

To describe the typical and atypical clinical and electroencephalographic (EEG) features of 40 patients with Jeavons syndrome (JS).

METHOD

Retrospective analysis from two French tertiary centers.

RESULTS

Forty patients were enrolled (31 females and 9 males; sex ratio F/M = 3.44; mean age at epilepsy onset: 6.2 ± 3.4 years [range: 1-15 years]). A positive family history of generalized genetic epilepsy was reported by 13 patients (32.5 %). Eyelid myoclonias with or without absence were the seizure onset in 29 patients (72.5 %), and generalized tonic-clonic seizures in 11 (27.5 %). Over the course of the disease, all had absences. Intellectual disability and psychiatric disorders were reported in 14 (35 %) and 18 patients (45 %), respectively. Focal EEG abnormalities were observed in 65 % of patients, with a posterior (57.7 %) or anterior (30 %) distribution. Generalized EEG discharges were identified in 37 patients (92.5 %). Epileptiform abnormalities were activated during NREM sleep and increased upon awakening. Response to intermittent light stimulation (ILS) was observed in 34 patients (85 %), with an unusual pattern of epileptiform abnormalities at the same frequency of the flashes in 20 patients. Patients with all seizure types were more likely to have this response (p = 0.017).

CONCLUSION

JS is a lifelong genetic epileptic syndrome with onset in childhood, female preponderance, and a positive family history of epilepsy in one-third of the cases. Focal EEG abnormalities are frequent. Response to ILS appears different from other photosensitive syndromes, with an unusual pattern of photo-induced abnormal synchronization. Intellectual disability and psychiatric disorders are not rare.

Factors correlated with intracranial interictal epileptiform discharges in refractory epilepsy

OBJECTIVE

This study was undertaken to evaluate the influence that subject-specific factors have on intracranial interictal epileptiform discharge (IED) rates in persons with refractory epilepsy.

METHODS

One hundred fifty subjects with intracranial electrodes performed multiple sessions of a free recall memory task; this standardized task controlled for subject attention levels. We utilized a dominance analysis to rank the importance of subject-specific factors based on their relative influence on IED rates. Linear mixed-effects models were employed to comprehensively examine factors with highly ranked importance.

RESULTS

Antiseizure medication (ASM) status, time of testing, and seizure onset zone (SOZ) location were the highest-ranking factors in terms of their impact on IED rates. The average IED rate of electrodes in SOZs was 34% higher than the average IED rate of electrodes outside of SOZs (non-SOZ; p < .001). However, non-SOZ electrodes had similar IED rates regardless of the subject's SOZ location (p = .99). Subjects on older generation (p < .001) and combined generation (p < .001) ASM regimens had significantly lower IED rates relative to the group taking no ASMs; newer generation ASM regimens demonstrated a nonsignificant association with IED rates (p = .13). Of the ASMs included in this study, the following ASMs were associated with significant reductions in IED rates: levetiracetam (p < .001), carbamazepine (p < .001), lacosamide (p = .03), zonisamide (p = .01), lamotrigine (p = .03), phenytoin (p = .03), and topiramate (p = .01). We observed a nonsignificant association between time of testing and IED rates (morning-afternoon p = .15, morning-evening p = .85, afternoon-evening p = .26).

SIGNIFICANCE

The current study ranks the relative influence that subject-specific factors have on IED rates and highlights the importance of considering certain factors, such as SOZ location and ASM status, when analyzing IEDs for clinical or research purposes.

Light-emitting-diode and Grass PS 33 xenon lamp photic stimulators are equivalent in the assessment of photosensitivity: Clinical and research implications

The assessment of the effect of photic stimulation is an integral component of an EEG exam and is especially important in patients referred for ascertained or suspected photosensitivity with or without a diagnosis of epilepsy. A positive test result relies on eliciting a specific abnormality defined as the "photoparoxysmal response". Reliability of this assessment is strongly influenced by technical and procedural variables, a critical one represented by the physical properties of the stimulators used. Established clinical norms are based on data acquired with the "gold-standard" Grass PS stimulators. These are no longer commercially available and have been replaced by stimulators using light emitting diode (LED) technology. To our knowledge no comparative study on their efficacy has been conducted. To address this gap, we recruited 39 patients aged 5-54 years, referred to two specialized centers with confirmed of suspected diagnosis of photosensitive epilepsy or generalized epilepsy with photosensitivity in a prospective randomized single-blind cross-over study to compare two commercially available LED-bases stimulation systems (FSA 10® and Lifeline® stimulators) against the Grass PS 33 xenon lamp device. Our findings indicate that the LED systems tested are equivalent to the Grass stimulator both in identifying the PPR in affected individuals.

The effect of antiepileptic drugs on epileptiform discharges in genetic generalized epilepsy: A systematic review

OBJECTIVE

The objective of this study was to evaluate the current evidence regarding the effect of antiepileptic drugs (AEDs) on epileptiform discharge (ED) burden in genetic generalized epilepsy (GGE).

METHODS

We conducted a comprehensive literature search of PubMed, Embase, PsycINFO, and the Web of Science Core Collection databases using the keywords 'genetic generalized epilepsy', 'antiepileptic drugs' and 'epileptiform discharge'. Primary human studies published in English that reported the effect of AEDs on EDs captured on electroencephalogram (EEG) recordings of at least 24 h in duration in patients with GGE were included.

RESULTS

Six studies published between 1984 and 2017, which reported the effect of AEDs on EDs, involving a total of 116 patients with GGE, were analyzed. Our systematic review found a tendency for AEDs to reduce ED density, frequency, cumulative duration, and burst duration in GGE. Furthermore, we found evidence that the AED-mediated reduction in ED burden was associated with improved seizure control and cognitive outcomes.

CONCLUSIONS

Antiepileptic drugs tend to reduce ED burden in GGE, but the significance of this association remains uncertain.

A forward-looking review of seizure prediction

PURPOSE OF REVIEW

Seizure prediction has made important advances over the last decade, with the recent demonstration that prospective seizure prediction is possible, though there remain significant obstacles to broader application. In this review, we will describe insights gained from long-term trials, with the aim of identifying research goals for the next decade.

RECENT FINDINGS

Unexpected results from these studies, including strong and highly individual relationships between spikes and seizures, diurnal patterns of seizure activity, and the coexistence of different seizure populations within individual patients exhibiting distinctive dynamics, have caused us to re-evaluate many prior assumptions in seizure prediction studies and suggest alternative strategies that could be employed in the search for algorithms providing greater clinical utility. Advances in analytical approaches, particularly deep-learning techniques, harbour great promise and in combination with less-invasive systems with sufficiently power-efficient computational capacity will bring broader clinical application within reach.

SUMMARY

We conclude the review with an exercise in wishful thinking, which asks what the ideal seizure prediction dataset would look like and how these data should be manipulated to maximize benefits for patients. The motivation for structuring the review in this way is to create a forward-looking, optimistic critique of the existing methodologies.

Diagnostic yield of standard-wake and sleep EEG recordings

OBJECTIVE

To investigate whether Posterior Dominant Rhythm (PDR) can be reliably assessed in sleep-EEG recordings and to investigate the diagnostic yield of standard-wake and sleep-recordings.

METHODS

EEG recordings of 303 consecutive patients aged 18-88 years were analyzed. All patients had both standard-wake and sleep-recordings, including patients who had abnormal standard recordings. Melatonin was used in 6% of sleep EEGs, and sleep deprivation in 94%. The mean duration of sleep was 41 min. We measured the PDR frequency in standard and sleep-recordings, both before and after sleep. We compared the diagnostic yield of standard-wake and sleep EEG recordings.

RESULTS

Compared to standard EEG, sleep-recordings showed a significantly lower PDR frequency, both when measured before and after sleep (p < 0.001). One-hundred-fifty-six patients (51%) had normal standard recordings, and 35 of them (22%) had abnormal findings in the sleep-recording. One-hundred-forty-seven patients had abnormal standard recordings and in 16 of them (11%) these abnormalities were not present in sleep-recording.

CONCLUSIONS

PDR is significantly slower in the wake periods of sleep-recordings, compared to standard wake recordings.

SIGNIFICANCE

Sleep and standard wake recordings are complementary.

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.

Temporal patterns of epileptiform discharges in genetic generalized epilepsies

OBJECTIVE

We sought to investigate the temporal patterns and sleep-wake cycle-related epileptiform discharges (EDs) in genetic generalized epilepsies (GGEs).

METHODS

We studied 24-hour ambulatory electroencephalography (EEG) recordings of patients with GGE, diagnosed and classified according to the International League against Epilepsy criteria. We manually coded the type of discharge, time of occurrence, duration, and arousal state of each ED. We employed mixed effects Poisson regression modeling to study the temporal distribution of epileptiform discharges. Additionally, we used multinomial regression analysis to explore the significance of the relationship between different states of arousal and types of epileptiform discharges.

RESULTS

We analyzed 6923 EDs from 105 abnormal 24-hour EEGs. Mixed effects Poisson regression analysis demonstrated significant changes in ED counts across time blocks. This distribution was largely influenced by the state of arousal. Generalized fragments (duration<2s) and focal discharges were more frequent during non-REM sleep while paroxysms (duration≥2s) were more frequent in wakefulness. Overall, 67% of epileptiform discharges occurred in non-REM sleep and only 33% occurred in wakefulness. Twenty-four patients (23%) had ED exclusively in sleep. Epileptiform discharges peaked from 23:00 through 07:00h.

SIGNIFICANCE

There is a time-of-day dependency of ED with a significant influence exerted by the state of arousal. Our observations suggest that the generation of epileptiform discharges is not a random process but is the result of complex interactions among biological rhythms such as the sleep-wake cycle and the intrinsic circadian pacemaker. High density of ED in sleep suggests that 24-hour EEG recording with the capture of natural sleep may be more useful than routine EEG to diagnose GGE.

Presence of a Chaotic Region at the Sleep-Wake Transition in a Simplified Thalamocortical Circuit Model

Sleep and wakefulness are characterized by distinct states of thalamocortical network oscillations. The complex interplay of ionic conductances within the thalamo-reticular-cortical network give rise to these multiple modes of activity and a rapid transition exists between these modes. To better understand this transition, we constructed a simplified computational model based on physiological recordings and physiologically realistic parameters of a three-neuron network containing a thalamocortical cell, a thalamic reticular neuron, and a corticothalamic cell. The network can assume multiple states of oscillatory activity, resembling sleep, wakefulness, and the transition between these two. We found that during the transition period, but not during other states, thalamic and cortical neurons displayed chaotic dynamics, based on the presence of strange attractors, estimation of positive Lyapunov exponents and the presence of a fractal dimension in the spike trains. These dynamics were quantitatively dependent on certain features of the network, such as the presence of corticothalamic feedback and the strength of inhibition between the thalamic reticular nucleus and thalamocortical neurons. These data suggest that chaotic dynamics facilitate a rapid transition between sleep and wakefulness and produce a series of experimentally testable predictions to further investigate the events occurring during the sleep-wake transition period.

24-hour rhythmicity of seizures in refractory focal epilepsy

The occurrence of seizures in specific types of epilepsies can follow a 24-hour nonuniform or nonrandom pattern. We described the 24-hour pattern of clinical seizures in patients with focal refractory epilepsy who underwent video-electroencephalography monitoring. Only patients who were candidates for epilepsy surgery with an unequivocal seizure focus were included in the study. A total of 544 seizures from 123 consecutive patients were analyzed. Specific time of seizures were distributed along 3- or 4-hour time blocks or bins throughout the 24-hour period. The mean age of the subjects was 37.7 years, with standard deviation of 11.5 years, median of 37. The majority were females (70/56%). The majority of patients had a seizure focus located in the mesial temporal lobe (102/83%) and in the neocortical temporal lobe (13/11%). The remaining patients had a seizure focus located in the extratemporal lobe (8/6%). The most common etiology was mesial temporal sclerosis (86/69.9%). Nonuniform seizure distribution was observed in seizures arising from the temporal lobe (mesial temporal lobe and neocortical temporal lobe), with two peaks found in both 3- and 4-hour bins: 10:00-13:00/16:00-19:00 and 08:00-12:00/16:00-20:00 respectively (p=0.004). No specific 24-hour pattern was identified in seizures from extratemporal location. The 24-hour rhythmicity of seizure distribution is recognized in certain types of epilepsy, but studies on the topic are scarce. Their replication and validation is therefore needed. Our study confirms the bimodal pattern of temporal lobe epilepsy independently of the nature of the lesion. However, peak times differ between different studies, suggesting that the ambient, rhythmic exogenous factors or environmental/social zeitgebers, may modulate the 24-hour rhythmicity of seizures. Characterization of these 24-hour patterns of seizure occurrence can influence diagnosis and treatment in selected types of epilepsy, such as the case of temporal lobe epilepsy, the most common drug-resistant epilepsy.

Effects of antiepileptic drugs on interictal epileptiform discharges in focal epilepsies: an update on current evidence

Interictal epileptiform discharges (IEDs), occurring in the electroencephalograms (EEG) of patients with focal epilepsy, are crucial for diagnosis, while their relationship with seizure severity and recurrence is controversial. The effects of antiepileptic drugs (AEDs) on IEDs are even more debated. In general, it is currently believed by experts in the field that most of the classical AEDs do not significantly affect IEDs occurrence in these patients, and that monitoring their EEG effects during treatment is useless. In this review, we update the existing literature on the effects of classical and newer AEDs on focal IEDs, emphasizing the scarcity of data concerning the latter. We also discuss potential limits of available clinical and experimental data and future perspectives.

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.

Early EEG improvement after ketogenic diet initiation

PURPOSE

This study examines electroencephalographic (EEG) changes in children with medication resistant epilepsy treated with the ketogenic diet (KD).

METHODS

Routine EEGs were obtained prior to KD initiation, then one month and three months later. Changes in EEG background slowing and frequency of interictal epileptiform discharges (IEDs) were evaluated using power spectrum analysis and manual determination of spike index. KD responders were compared to non-responders to determine if baseline or early EEG characteristics predicted treatment response (>50% seizure reduction) at three months.

RESULTS

Thirty-seven patients were evaluated. No differences in baseline EEG features were found between responder groups. Frequency of IEDs declined in 65% of patients as early as one month, by a median of 13.6% (IQR 2-33). Those with a ten percent or greater improvement in IED frequency at one month were greater than six times more likely to be KD responders (OR 6.5 95% CI 0.85-75 p=0.03). Qualitative and quantitative measures of EEG background slowing improved in the whole cohort, but did not predict responder status.

CONCLUSION

Baseline predictors of KD response remain elusive. Most patients experienced a reduction in IEDs and improvement in EEG background slowing after KD initiation. Reduction of IEDs at one month strongly predicted KD responder status at three months.

EEG spike activity precedes epilepsy after kainate-induced status epilepticus

PURPOSE

Chronic epilepsy frequently develops after brain injury, but prediction of which individual patient will develop spontaneous recurrent seizures (i.e., epilepsy) is not currently possible. Here, we use continuous radiotelemetric electroencephalography (EEG) and video monitoring along with automated computer detection of EEG spikes and seizures to test the hypothesis that EEG spikes precede and are correlated with subsequent spontaneous recurrent seizures.

METHODS

The presence and pattern of EEG spikes was studied during long recording epochs between the end of status epilepticus (SE) induced by three different doses of kainate and the onset of chronic epilepsy.

RESULTS

The presence of spikes, and later spike clusters, over several days after SE before the first spontaneous seizure, was consistently associated with the development of chronic epilepsy. The rate of development of epilepsy (i.e., increase in seizure frequency) was strongly correlated with the frequency of EEG spikes and the cumulative number of EEG spikes after SE.

CONCLUSIONS

The temporal features of EEG spikes (i.e., their presence, frequency, and pattern [clusters]) when analyzed over prolonged periods, may be a predictive biomarker for the development of chronic epilepsy after brain injury. Future clinical trials using prolonged EEG recordings may reveal the diagnostic utility of EEG spikes as predictors of subsequent epilepsy in brain-injured humans.

Cardiovascular protective effect of melatonin in sudden unexpected death in epilepsy: A hypothesis

Epilepsy is the most common neurological disorder, approximately 1% of the population worldwide have epilepsy. Moreover, sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. Information concerning risk factors for SUDEP is conflicting, but potential risk factors include: age, early onset of epilepsy, duration of epilepsy, uncontrolled seizures, seizure frequency, AED number and winter temperatures. Additionally, the cause of SUDEP is still unknown; however, the most commonly suggested mechanisms are cardiac abnormalities during and between seizures. Furthermore, the evidence from the last 10 years suggests that melatonin has an important role in the epileptogenesis process and influences the cardiovascular system as well. The positive effect of melatonin has been demonstrated against different convulsive stimuli in several rodents, including seizures induced by pentylenetetrazole kainate, glutamate, maximal electrical shock and electrically kindled stimulation of amygdala. Clinical studies have also demonstrated a positive role of melatonin on the seizure frequency in children and reduced spiking activity and seizure frequency in patients with intractable epilepsy. In the rat hearts, studies in vivo and in vitro using pharmacological concentrations of melatonin confirmed an anti-arrhythmic effect of this hormone and studies in humans have been shown that chronic heart disease patients have significantly lower melatonin levels in their blood stream than do normal individuals. Thus, caution should be taken in generalization of these findings to epileptic population. Moreover, it is important to note that when dealing with intractable epilepsy that do not respond to any conventional treatment, the additional of melatonin may be evaluated. Taken together, in this paper we suggested a possible relationship between cardiac abnormalities, melatonin and SUDEP.

Effects of pinealectomy and the treatment with melatonin on the temporal lobe epilepsy in rats

The aim of the present work was to analyze the effects of pinealectomy in the development of the epilepsy model induced by pilocarpine in adult male rats. Group I: Wistar male adult rats were submitted to pinealectomy, and 7 days after surgery, these animals received pilocarpine (350 mg/kg, i.p.) to induce three distinct behavioral phases: status epilepticus, seizure-free, and chronic phases. This late, as well as all control groups were continuously video-recorded for 60 days, to study behavior parameters. These animals were killed and the brain sections were processed for Nissl and neo-Timm. Group II: Another group, also submitted to pinealectomy, received several injections of melatonin (2.5 mg/kg): 20 min before, concomitantly with pilocarpine, 30 min, 1 h, and 2 h after pilocarpine administration. Some animals from group I and all from group II were sacrificed 48 h following status epilepticus onset to perform TUNEL assay. The latency for status epilepticus onset, status epilepticus length as well as mortality rate during status epilepticus were similar for pinealectomized and control groups. On the other hand, pinealectomized rats presented minor duration of the silent period, a higher number of spontaneous seizures during the chronic phase, increased number of TUNEL-positive cells (acute phase), increased neuronal loss, and marked supragranullar mossy fibers sprouting (chronic phase) in the hippocampal formation, when compared with control groups. Our data show that the pinealectomy facilitates the epileptogenic process that follows the long-lasting status epilepticus. This facilitation can be partially reverted by the simultaneous administration of melatonin.

Sleep and sleep deprivation as EEG activating methods

OBJECTIVES

We examined retrospectively 19 patients with a history of clinical seizures, but normal activity or unclear epileptiform abnormalities in wake EEG recordings and obtained preliminary data for a controlled cohort study to evaluate the effects of sleep deprivation (SD) on interictal epileptic activity.

METHODS

Nineteen patients referred to our EEG department for diagnostic or follow-up purposes were divided in two groups on the basis of the different EEG protocols applied. The first group (n=5) underwent two laboratory polysomnographies during afternoon naps, after SD, but the patients failed to fall asleep in one of the two occasions. The second group (n=14) was submitted to two polysomnographies, the first without SD and the second after SD.

RESULTS

The first group of patients demonstrated focal epileptic discharges in 4 patients in which wake after SD appeared to be less activated that sleep after SD. In the second group the results obtained from the waking part of the recordings suggest a lack of activating effect due to SD.

CONCLUSIONS

SD does not seem to offer greater activation than sleep alone. However, a mild SD may be a convenient activating method for inducing sleep and drowsiness without using any drug.

Sleep and EEG interictal epileptiform abnormalities in partial epilepsy

The relationship between sleep and EEG interictal epileptiform abnormalities (IEA) has been studied from different perspectives. One of the most followed orientations regards the investigation of the effects of IEA on sleep organization, while another approach considers the modulation of IEA caused by sleep. Only the latter approach, for its practical diagnostic implications, is covered by the present review. In particular, on the basis of the literature and of personal studies, we review some relevant aspects of the relationship between the different stages of the sleep and the EEG epileptic abnormalities in partial epilepsy. In addition, the modulation of IEA by fluctuations of the level of arousal and by sleep microstructure is reviewed. Finally, the information obtained on localization of epileptic foci from recordings during wakefulness and different sleep stages is discussed.

Cyclic alternating pattern (CAP) and epilepsy during sleep: how a physiological rhythm modulates a pathological event

OBJECTIVES

Epileptic susceptibility is triggered by the sleeping condition. However, both ictal and interictal events are not equally affected by the different sleep states. Besides the well-known dichotomy between non-REM sleep (high activation) and REM sleep (low activation), epileptic phenomena are deeply sensitive to the ongoing level of arousal.

METHODS

During non-REM sleep the arousal level can be either unstable, as expressed by the repetitive sequences of the cyclic alternating pattern (CAP), or stable, as reflected by non-CAP. Phase A (arousal complex) and phase B (post-arousal rebound response) are the two basic components of the CAP cycle, which presents a 20-40 s periodicity. Three subtypes of A phases can be recognized: the A1 subtypes, which are thoroughly composed of K-complexes and delta bursts, and subtypes A2 and A3 dominated by moderate (A2) or prominent (A3) EEG desynchrony.

RESULTS

As a manifestation of unstable sleep, CAP offers a favorable background for the occurrence of nocturnal motor seizures that in most cases arise in concomitance with a phase A. In primary generalized epilepsy (PGE) and in lesional epilepsies with fronto-temporal focus, activation of interictal discharges is high during CAP reaching the climax during phase A and the strongest inhibition during phase B. A lack of modulation is observed instead in epilepsy with benign rolandic spikes. In PGE, the interictal bursts are mostly associated with the highly synchronized phase A1 subtypes.

CONCLUSIONS

The analysis of sleep microstructure based on CAP parameters offers a sensitive framework for exploring the linkage between dynamic EEG events and epileptic phenomena.

Reduction of epileptiform activity in response to low-dose clonazepam in children with epilepsy: a randomized double-blind study

PURPOSE

To evaluate the effect of low-dose clonazepam (CZP) on the amount of epileptiform activity in children with focal and generalized epilepsy.

METHODS

In a single-blind pilot study, followed by a double-blind, placebo-controlled, randomized, crossover study, 15 children with epilepsy were evaluated by using 24-h long-term EEG recordings during baseline days and days after injections of placebo and CZP. The drug was given as a single i.m. injection of 0.02 mg/kg BW. Blood samples were obtained regularly for analysis of plasma concentrations of CZP. The number of epileptiform discharges was determined during corresponding periods with the individual child in the same state of alertness, the same real time of day, and with concomitant antiepileptic drugs (AEDs) unchanged.

RESULTS

In the double-blind study, low-dose CZP produced a highly significant (p = 0.0015) decrease in the amount of epileptiform activity (mean, -69% vs. placebo, -2%) obtained during periods when median plasma concentrations ranged from 18 to <14 nM. The maximal plasma level (median, 24 nM) was reached before the start of the analysis periods. The pilot study showed reductions of epileptiform discharges within the same range as the double-blind study. In the children with daily seizures, a parallel decrease in seizures and the number of epileptiform discharges was seen after the administration of CZP.

CONCLUSIONS

Our data demonstrate a significant reduction of epileptiform discharges on long-term EEGs after a single low dose of CZP with concomitant low plasma levels, which were considerably lower than the doses and plasma levels usually recommended. A concomitant reduction of seizures also was seen.

Variability of epileptiform activity in long-term EEGs with short and long intervals in children with epilepsy

OBJECTIVE

To evaluate the impact of the time factor on the amount of epileptiform activity in long-term EEG recordings in children with epilepsy.

METHODS

Ten children with epilepsy of different types underwent three 24 h EEG examinations during two consecutive days and with a month's interval. The number of epileptiform discharges during selected corresponding periods of time was counted.

RESULTS

The number of epileptiform discharges on three repeated examination days showed no significant difference (ANOVA P = 0.88) as intraindividual increases and decreases on different days counterbalanced each other within the group. However the standard deviations of the relative changes were larger between recordings with a month's interval compared to those for consecutive days (86% and 33%). The mean magnitude of change was 55% between days separated by a month compared to 24% on consecutive days. The difference was non-significant but showed a trend towards larger changes with a longer interval (P = 0.07).

CONCLUSIONS

The variability of epileptiform activity was larger when the interval between recordings was 1 month compared to consecutive days. The magnitude of the relative changes between intervals of 1 and 30 days showed a trend towards a difference although not statistically significant. When evaluating repeated long-term EEGs in relation to therapy in children, these variations should be considered.

Melatonin's role as an anticonvulsant and neuronal protector: experimental and clinical evidence

The pineal gland classically has been considered as a vestigial and mystic organ. In the last decades, and with the incorporation of new methodologic procedures, it could be proved that it also has physiologic actions that vary depending on the level of the phylogenetic scale. Its best-known secretion, melatonin, has been related to many different actions, such as sleep promotion, control of biologic rhythms, hormonal inhibition, and an inhibiting action on central nervous system regulation mechanisms. In animal experimentation, there are papers even accepting an anticonvulsant effect. In humans, evidence is reduced to few experiences. In addition to this clinical experience, there is other evidence that clearly relates melatonin to convulsive phenomena. This relationship must be mediated by the following mechanisms attributed to melatonin: altered brain GABAergic neurotransmission, its known interaction with benzodiazepinic brain receptors, through tryptophan metabolite activity (kynurenine, kynurenic acid), or even by its efficacy as a free-radical scavenger.

Predictive value of interictal epileptiform discharges during non-REM sleep on scalp EEG recordings for the lateralization of epileptogenesis

PURPOSE

EEG recording during sleep is widely used in the assessment of epilepsy, particularly in candidates for surgery, yet the diagnostic value of this procedure is not well established. We evaluated the predictive reliability of interictal epileptiform discharges (IEDs) for localization in presurgical patients with temporal lobe epilepsy (TLE) during non-REM sleep.

METHODS

Preoperative scalp EEG recordings with waking and sleep states were assessed in 83 patients with TLE in whom localization of the epileptogenic zone was subsequently confirmed by successful surgical treatment (patient seizure-free >1 year).

RESULTS

The accuracy of EEG recordings for prediction of lateralization significantly changed from 51.8% during waking to 78.3% during sleep. After exclusion of patients who showed no discharges, the predictive value changed from 74.1 to 86.7%. However, in patients in whom the waking scalp EEG lateralized incorrectly, no improvement in reliability was achieved by sleep recording.

CONCLUSIONS

Our results suggest that IEDs occurring in non-REM sleep provide more accurate information for lateralization of epileptogenesis than do those occurring during waking. This gain of diagnostic information was obtained in patients who showed either bilateral or no discharges in waking records, because unilateral discharges arising de novo in sleep were always correctly lateralizing. On the other hand, in patients who showed unilateral discharges in the awake state, whether ipsilateral or contralateral to the epileptogenic zone, the findings were generally unchanged during sleep.

Time distribution of epileptic seizures during video-EEG monitoring. Implications for health insurance systems in developing countries

An attempt was made to identify guidelines to help establish epilepsy monitoring units in developing countries. We assessed the time distribution of seizures during video-EEG monitoring and we also estimated the minimum time required for such a procedure and the impact of these variables upon the health insurance system. Mean time for recording five stereotyped clinical events was 72 hours, with a significant number of events recorded between midnight and 0600 hours (P < 0.05). This pilot study may help to establish local policies that will warrant an adequate work-up for our patients.

[Indications for emergency EEG in disease, a brief loss of consciousness in generalized epileptic seizures in the adult]

EEG provides essential information for the management of patients in whom a first epileptic seizure is suspected because of transient alteration of consciousness. Postictal or interictal EEG abnormalities are useful to the clinician even when the diagnosis of epileptic seizure appears clinically evident. EEG is especially useful when recordings are performed immediately after the episode, in the absence of benzodiazepine therapy, and repeated later. After a transient loss or alteration of consciousness, the EEG should be considered as part of the emergency management, and thus rapidly obtained, whenever the evolution and/or the clinical signs of the episode are consistent with a focal epileptic seizure, especially if gestual or oro-facial automatisms, or bizarre deambulatory behavior have preceded the episode. EEG should also be considered as an emergency examination when a tonic-clonic seizure is suspected clinically, eg, when loss of consciousness is prolonged and inconsistent with a syncopal attack; when it is accompanied by clonic movements or spasms and followed by postictal confusion or stertor; when it entails a head injury or a tongue biting, or when it is preceded by premonitory signs or symptoms consistent with epilepsy. In the absence of such clinical suspicion, an EEG is not justified.

Reliability of automatic and visual analysis of interictal spikes in lateralising an epileptic focus during video-EEG monitoring

We evaluated 2 h of two night recordings of surface EEG of 10 patients with drug-resistant focal epilepsy using video-EEG monitoring, giving 40 h of EEG. The raw data of the automatic spike analysis according to the Gotman algorithm was visually corrected by rejecting false detections. Furthermore, the complete EEG recordings were analysed independently visually by two experienced electroencephalographers. For each method we analysed the total count of detections and the topographical distribution (left-right) of spikes. The total number of detections was significantly higher (243%) in the raw data and significantly lower after elimination of false detections (57%) in comparison to conventional analysis (100%). Lateralisation was concordant between the methods in 9/10 patients. The extent (< 75%, 75-90%, > or = 90%) was concordant in 80% between the two human raters. The automatic analysis with elimination of false detections was concordant with each of the human raters in 60% of patients. Extent of concordance was dependent of the total number of spikes with patients having more spikes being more reliably lateralised. Our results suggest that visually corrected automatic spike analysis is an economical method to use interictal epileptogenic activity as an independent indicator of the side of the epileptogenic focus in the setting of non-invasive presurgical evaluation. This is especially true in patients with many spikes.

Neuronal complexity loss in temporal lobe epilepsy: effects of carbamazepine on the dynamics of the epileptogenic focus

Analysis methods derived from the theory of non-linear dynamics have been shown to provide new information about the complex spatio-temporal behaviour of neuronal networks involved in temporal lobe epilepsy. To test whether day to day alterations in neuronal complexity are influenced by changes in serum level of carbamazepine (CBZ), a moving-window correlation dimension analysis was applied to electrocorticographic and stereoelectroencephalographic recordings of 10 patients with unilateral temporal lobe epilepsy. Data sets (n = 78) were obtained from interictal states at subsequent days during the presurgical evaluation with strongly variant CBZ serum levels. The so-called neuronal complexity loss L* was used to quantify the change of dimensionality in brain electrical activity recorded under different levels of medication. We found a significant inverse relationship between L* and CBZ serum level spatially restricted to the primary epileptogenic area. This finding can be assumed to reflect the mechanism of action of CBZ attributed to an inhibition of sustained high-frequency firing of bursting neurons.

The epidemiology of epilepsy. Past, present, and future

Much has been learned from epidemiologic studies about the frequency, causes, natural history, and prognosis of epilepsy and other seizure disorders. This knowledge has resulted in significant changes in the clinical management of individuals who have seizures and epilepsy. Recent changes in the known causal factors and diagnostic technologic advances, among other factors, will affect the epidemiology and prognosis of epilepsy. Continued epidemiologic monitoring of this common neurologic condition is necessary to ensure an accurate understanding of the current forms of the disorder.

Circadian rhythm, sleep, and epilepsy

This review article: (1) describes the circadian distribution of ictal and interictal events; (2) differentiates transitional arousal, non-rapid eye movement and rapid eye movement sleep components and their substrates; (3) suggests the means by which the neural generators of these seizure-prone vs. seizure-resistant sleep and arousal states modulate the timing of different seizure manifestations; (4) considers clinical and mechanistic findings for the reciprocal effects of seizures and antiepileptic drugs upon the sleep-wake cycle; and (5) assesses clinical and basic mechanisms of sleep deprivation effects upon seizures.

Melatonin response in active epilepsy

Urinary excretion of 6-sulfatoxymelatonin (aMT.6S), the hepatic metabolite of melatonin, was measured for three consecutive 8-h intervals, beginning at 0600 h, in 30 patients with untreated active epilepsy and in 19 healthy subjects. Excretion of aMT.6S in a 24-h period in patients with active epilepsy was 77.3 +/- 55 nmol (median 68.0, range 8.7-280 nmol), significantly higher (p < 0.05) than that of healthy subjects (49.1 +/- 14 nmol, median 49.0, range 19.7-68.0 nmol). Sequential 8-h urinary aMT.6S excretion rates in patients with active epilepsy were 2.45 +/- 2.8 nmol/h (0600-1400 h), 0.83 +/- 0.5 nmol (1400-2200 h) and 6.38 +/- 5.0 nmol/h (2200-0600 h) as compared with 1.43 +/- 0.8, 1.10 +/- 0.8 and 3.81 +/- 1.3 nmol/h, respectively, in healthy subjects. Analysis of variance (ANOVA) indicated that the difference in total output resulted from greater nocturnal excretion (F = 5.58, p = 0.018). Melatonin production in untreated patients with active epilepsy is increased and has a circadian pattern with a phase difference as compared with that of normal subjects.

Extracranial EEG work-up in epilepsy surgery: usefulness and limitations

Extracranial interictal and ictal EEG provide essential information to diagnosis, seizure/syndrome classification and focus localization. Combined with structural and dynamic neuro-imaging and neuropsychological data, extracranial EEG will often provide sufficient information in preoperative work-up for temporal lobectomy. Ictal EEG recordings are essential to confirm the diagnosis and classification and, above all, to exclude patients with significant non-epileptic seizures from further surgical evaluation. The advantage of sphenoidal electrodes lies first and foremost in a more favorable signal/noise ratio, while their superiority to closely placed special scalp electrodes are more debatable.

The effect of oral flumazenil on interictal epileptic activity: results of a double-blind, placebo-controlled study

The effect on interictal EEG epileptic activity (IEA) of oral flumazenil, a benzodiazepine antagonist and potential antiepileptic drug, was studied in 12 adults with refractory epilepsy. Comparisons were made with placebo and 15 mg diazepam using a double-blind, randomised, cross-over design. A significant reduction in IEA from the baseline epileptic discharges was observed after flumazenil administration (at a dose of 30 or 100 mg) with a low incidence of adverse events. In patients who achieved > 50% reduction in the frequency of IEA, the median duration and extent of action of flumazenil (at either dose) were greater than for diazepam 15 mg or placebo. The frequency of response and duration of action with oral flumazenil were comparable to those obtained via the intravenous route. These results suggest that oral flumazenil may have an intrinsic antiepileptic activity and provide a rationale for a new approach in the treatment of intractable epilepsy.

Primary generalized seizure disorder: correlation of epileptiform discharges with seizure frequency

The role of routine follow-up EEG in assessment of severity of a seizure disorder is not known. This retrospective chart review study of patients with primary generalized seizure disorders explored the relation between parameters of epileptiform discharge bursts on EEG and number of seizures experienced in the preceding months. Eighty-seven such patients were found, each with one to seven EEGs and corresponding clinical records, comprising a total of 201 clinicoelectrographic epochs. The 56 chronically attending patients (more than two attendances) differed from the 31 nonchronic attenders in receiving more antiepileptic drugs (AEDs) and having fewer EEG polyspikes; otherwise, the two groups were similar and were analyzed together. We noted a strong relation between number and maximum length of epileptiform bursts in the resting EEG record and number of absence seizures reported in the months preceding the EEG. Age did not affect this relation. After stepdown regression analysis, only the maximum length of epileptiform bursts remained significantly related to the reported number of absence seizures. These findings may prove useful in assessing clinical progress, e.g., in patients whose ability to estimate numbers of attacks is suspect. Neither number nor maximum length of epileptiform bursts in the resting EEG record had a significant relation with the number of generalized tonic-clonic seizures. Presence of polyspikes on resting or "activated" EEG had no added predictive value. The presence of epileptiform bursts after activation by sleep, hyperventilation, or photic stimulation was not associated with an increased likelihood of having had seizures.

Genetic models of absence epilepsy, with emphasis on the WAG/Rij strain of rats

In this review, the main characteristics of genetic models of absence epilepsy, in particular with respect to WAG/Rij rats, are presented. Genetic models are important and relevant, since evidence exists that these models mimic spontaneously occurring human epilepsy more than models in which epilepsy is artificially induced. Genetic models can be divided into models in which seizures are elicited and into those in which epilepsy appears without any sensory stimulation. The majority of genetic models show that absence type of epilepsy; during the last few years, we and others have noticed that rats of various strains exhibit spontaneously occurring spike-wave discharges in the EEG. Among the strains highly affected is the WAG/Rij strain, which is a fully inbred strain. Individuals are homozygous and because of this property, genetic studies are meaningful. Electrophysiological studies have indicated that abnormal discharges in the cortical EEG are generalized and that the hippocampus is not involved. Parts of the thalamus, together with the thalamic reticular nucleus, apparently act as a pacemaker for the abnormal discharges. There is a circadian modulation in the number of spike-wave discharges. Discharges mainly occur during intermediate levels of vigilance such as passive wakefulness and light slow-wave sleep and at transitions of sleep states. Pharmacological studies with clinically effective antiepileptic drugs have shown a close agreement in seizure response between man and rat. Studies with new compounds have emphasized the role of the GABAergic and glutamatergic system in this type of epilepsy. Particularly striking is the role of the GABAergic system. GABA agonists enhance and GABA antagonists reduce the occurrence of spike-wave discharges, which deviates from the effects of GABAergic drugs in non-convulsive epilepsy. Even more striking is the role of the benzodiazepines, generally seen as GABA agonists; these drugs do not act as such in absence epilepsy since they reduce spike-wave discharges. Also good evidence for an involvement of other neurotransmitters such as noradrenaline, dopamine and opioid peptides exists in absence epilepsy. Genetic data obtained from the WAG/Rij model for absence epilepsy show a relatively simple pattern of inheritance with one gene determining whether an individual is epileptic or not, and with other genes regulating the number and duration of seizures. This is in good agreement with the more restricted human data. Cognitive studies have shown two important features of epilepsy in the WAG/Rij strain: modulation of the number of spike-wave discharges by mental or physical activity and on the other hand, the disruption of cognitive activity by spike-wave discharges.(ABSTRACT TRUNCATED AT 400 WORDS)

Activation of partial seizures with motor signs during cyclic alternating pattern in human sleep

Both interictal and ictal EEG phenomena are commonly activated by functional instability. The different non-REM sleep stages comprise long-lasting periods of cyclic alternating pattern (CAP) in which arousal fluctuates between 'A phases' of greater arousal and 'B phases' of less arousal, and periods in which vigilance maintains a tonic stability (non-CAP). Previous studies have revealed that phase A induces a marked enhancement of generalized EEG paroxysms, a minor though significant activation of focal lesional bursts, but no effect on rolandic functional spikes. Conversely, phase B exerts an inhibitory modulation, especially on bilateral interictal phenomena. Because of the opposite influence of phase A and phase B also on muscle tone, we assessed the amount and distribution of nocturnal partial motor seizures in 6 subjects affected by focal epilepsy. The polysomnograms included 45 motor seizures, 43 of which occurred during non-REM sleep. Nocturnal fits were significantly more frequent in stages 1 and 3 (P less than 0.0001). Among the non-REM seizures, 42 appeared in CAP (P less than 0.0001) and always in phase A. The transient arousal and the concomitant muscle tone activation expressed by phase A of CAP is likely to support the motor components of nocturnal seizures. Sleep analysis in terms of CAP and non-CAP provides a better understanding of the continuum from subclinical EEG paroxysms to clinical manifestations and of the relations between vigilance and seizure disorders.

Spike-wave discharges and sleep-wake states in rats with absence epilepsy

The occurrence of spike-wave discharges was studied in relation to the daily fluctuations of vigilance level in rats. Eight rats of the WAG/Rij strain, an animal model for idiopathic generalized epilepsy of the absence type, which were equipped with cortical EEG and nuchal EMG electrodes, served as subjects. It was found that spike-wave discharges predominantly occur during light slow wave sleep and passive wakefulness. REM sleep, active wakefulness, and deep slow wave sleep are less susceptible to the occurrence of spike-wave discharges. Finally, spike-wave discharges tend to prevail in transitional states. A crucial role for the degree of stability of the level of vigilance in the genesis of absence seizures is suggested.

Absence epilepsy and the level of vigilance in rats of the WAG/Rij strain

In man, a relationship exists between sleep-wake states and absence epilepsy. During wakefulness, spike-wave discharges predominantly occur when the level of vigilance is not high, while during sleep they have a preference to occur during slow-wave sleep. During this latter type of sleep, spike-wave discharges prevail in periods where slow-wave sleep is light. In a series of experiments, the WAG/Rij rat model for absence epilepsy was characterized with respect to the relationships between the level of vigilance, sleep-wake states and the occurrence of spike-wave discharges. In the first experiment, continuous recordings were made for a period of 48 h and a clear circadian rhythm was established for the number of spike-wave discharges. A maximum appeared during the middle of the dark period of the rat, whereas a minimum was detected directly after the onset of the light period, the time period during which deep slow-wave sleep predominates. The relationship of spike-wave discharges with states of vigilance was elaborated in a second study. Spike-wave discharges were mainly found during light slow-wave sleep, during passive wakefulness and in transition phases from sleep to wakefulness. During REM sleep no spike-wave discharges were found. In the last three experiments, the level of alertness was enhanced by various procedures as photostimulation, a learning task and deprivation of REM sleep. In all cases, an increase of alertness decreased the amount of epilepsy.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of intravenous flumazenil on interictal electroencephalographic epileptic activity: results of a placebo-controlled study

The effect on interictal electroencephalographic epileptic activity of intravenous flumazenil (Ro 15-1788), a benzodiazepine antagonist and potential antiepileptic drug, was studied in 10 patients. Comparison was made with intravenous diazepam (10 mg) and placebo using a single-blind, single-dose, cross-over design. A dose of 3 mg flumazenil was well tolerated and produced a significantly greater reduction in the number of epileptic transients during the first 40 minutes after injection than did placebo (p less than 0.05). This effect was similar to that of diazepam in magnitude and duration. When flumazenil (3 mg) was administered immediately after intravenous diazepam (10 mg), the reduction in interictal epileptic activity was not significantly different from that produced by diazepam alone. The results suggest that either flumazenil has intrinsic antiepileptic activity and in this respect acts as a partial agonist at the benzodiazepine receptor, or that it is antagonising an endogenous proconvulsant ligand in these patients.

Modulation of the interictal epileptiform EEG activity during sleep: from oscillations to complex dynamics

Polygraphic sleep recordings (EEG, EMG, and EOG) were performed in two groups of epileptic subjects, six with fragile-X syndrome and six with symptomatic epilepsy. Recordings were visually scored for sleep stages and number of spikes/min. Subjects with fragile-X syndrome showed a well defined pattern of production of interictal epileptiform activity with the lowest values during REM sleep; symptomatic epileptic subjects showed less defined and more variable spike/min diagrams. The spectral analysis of the outline of such diagrams confirmed these differences showing shorter periodicities (80-100 min) in the fragile-X group compared to those of the symptomatic group (160-220 min). Finally, a model with multiple feedback circuits is proposed in order to explain the different patterns observed.

Wakefulness-sleep modulation of EEG-EMG epileptiform activities: a quantitative study on a child with intractable epilepsia partialis continua

Continuous all night recordings of epileptiform EEG activities from right frontal scalp and thalamic Centromedian regions and EMG activities from left deltoid muscular region were performed on a child with intractable epilepsia partialis continua, with depth stimulating-recording electrodes used for neuroaugmentive seizure control. In addition, "normal" and "mature" sleep indicators in the same child were simultaneously recorded according to the International Procedures. During wakefulness (W), type B seizures consisted of isolated, high amplitude, negative-positive EEG sharp waves recorded from the right Centromedian region (RCM sharp) correlated with isolated bursts of high amplitude EMG potentials recorded from the left deltoid muscle (LEMG jerks). Type C seizures consisted of clusters of repetitive RCM sharp and LEMG jerks, where individual EEG-EMG activities showed poor correlations. Number and amplitude of type B RCM sharp and LEMG jerks significantly decreased when patient directly shifted from W to slow wave sleep I and II (SWSI and II). Number and amplitude of RCM sharp increased while those of LEMG jerks decreased directly from SWS I and II to slow wave sleep III (SWS III); all forms of EEG-EMG epileptiform type B activities significantly decreased directly or indirectly from W and SWS to paradoxical sleep (PS). Scalp EEG spikes from right frontal and central regions showed almost parallel changes to those of RCM sharp, except during SWS II, when amplitude increased in the former and decreased in the later. Occurrence of type C seizures only decreased during PS and duration decreased directly from SWS I to II and indirectly from SWS I to SWS II and PS; and from W to SWS II and III and PS.

Effects of the removal of phenytoin, carbamazepine, and valproate on the electroencephalogram

We report the EEG changes that occurred on discontinuance of phenytoin (PHT), carbamazepine (CBZ), and valproate (VPA) in patients with active epilepsy. Discontinuation of CBZ was associated with an increase in mean frequency of dominant rhythm and reduction in amount of slow activity. Patients who had a marked increase in seizures on discontinuation of an antiepileptic drug had a slower mean dominant rhythm at baseline than did patients who did not have an increase in seizures. Subsequent EEGs, during and at the end of drug reduction, showed an increase in bursts of interictal epileptiform activity (IEA) and in slow activity in patients who had a marked increase in seizures. The amount of slow activity and IEA did not alter in patients who did not have an increase in seizures. No patients developed photosensitivity.

Sleep, epilepsy, and the EEG in infancy and childhood

Each of the major epileptic syndromes that occur in infants and children demonstrates relationships to sleep and wakefulness that are particular to that syndrome. These relationships include activation or suppression of clinical seizures during certain portions of the sleep-wake cycle, differences in symptomatology of the seizures or in seizure type, alterations in distribution or morphology of epileptiform waveforms, and changes in duration and composition of sleep stages. Knowledge of the interactions between sleep and seizures helps to increase understanding of the physiological mechanisms underlying epilepsy, as well as to improve clinical diagnosis.

Preliminary evaluation of potential anti-epileptic drugs by single dose electrophysiological and pharmacological studies in patients

In phase 1 evaluation of potential anti-epileptic drugs (AEDs), insufficient attention has perhaps been directed to the transition from single, and multi-dose studies in normal volunteers to clinical trials of some weeks duration in patients. Acute single dose studies in epileptic patients already receiving AEDs may reduce avoidable errors in early controlled trials. Acute single dose studies provide the opportunity of obtaining some preliminary evidence of efficacy by observing the effects of the drug on quantified epileptiform EEG discharges, both those occurring spontaneously in long term telemetric recordings and those elicited by standardised photic stimulation in susceptible subjects. The pharmacokinetics of the new drug may be profoundly influenced by the comedication (as illustrated by lamotrigine, the half life of which varies by a factor of 10 depending on comedication). Conversely, the new drug may so influence metabolism of the comedication that the results of add-on trials may be virtually uninterpretable, unless steps are taken to maintain blood levels of the other AEDs. A method of addressing this problem is illustrated in the case of an imidazole, R57720. Adverse experiences may also occur more readily when a new drug is added to comedication than when it is given to normal volunteers and these problems in chronic trials can be anticipated from acute studies.