Effect of seizures and epileptiform discharges on cognitive function

Impact of two ketogenic diet types in refractory childhood epilepsy

BACKGROUND

Ketogenic diet (KD) refers to any diet in which food composition induces a ketogenic state of human metabolism.

OBJECTIVE

To assess short- and long-term efficacy, safety, and tolerability of KD [classic KD and modified Atkins diet (MAD)] in childhood drug-resistant epilepsy (DRE) and to investigate the effect of KD on electroencephalographic (EEG) features of children with DRE.

METHODS

Forty patients diagnosed with DRE according to International League Against Epilepsy were included and randomly assigned into classic KD or MAD groups. KD was initiated after clinical, lipid profile and EEG documentation, and regular follow-up was done for 24 months.

RESULTS

Out of 40 patients with DRE, 30 completed this study. Both classic KD and MAD were effective in seizure control as 60% in classic KD group and 53.33% in MAD group became seizure free, and the remaining showed ≥50% seizure reduction. Lipid profile remained within acceptable levels throughout the study period in both groups. Adverse effects were mild and managed medically with an improvement of growth parameters and EEG during the study period.

CONCLUSIONS

KD is an effective and safe non-pharmacologic, non-surgical therapy for the management of DRE with a positive impact on growth and EEG.

IMPACT

Both common types of KD (classic KD and MAD) are effective for DRE, but unfortunately, nonadherence and dropout rates are frequent. High serum lipid profile (cardiovascular AE) is often suspected in children following a high-fat diet, but lipid profile remained in the acceptable level up to 24 months. Therefore, KD constitutes a safe treatment. KD had a positive impact on growth, despite inconsistent results of the KD's effect on growth. In addition to showing strong clinical effectiveness, KD also considerably decreased the frequency of interictal epileptiform discharges and enhanced the EEG background rhythm.

The Significance of Subclinical Epileptiform Activity in Alzheimer's Disease: A Review

Hyperexcitability is a recently recognized contributor to the pathophysiology of Alzheimer's disease (AD). Subclinical epileptiform activity (SEA) is a neurophysiological sign of cortical hyperexcitability; however, the results of the studies in this field vary due to differences in the applied methodology. The aim of this review is to summarize the results of the related studies aiming to describe the characteristic features and significance of subclinical epileptiform discharges in the pathophysiologic process of AD from three different directions: (1) what SEA is; (2) why we should diagnose SEA, and (3) how we should diagnose SEA. We scrutinized both the completed and ongoing antiepileptic drug trials in AD where SEA served as a grouping variable or an outcome measure. SEA seems to appear predominantly in slow-wave sleep and in the left temporal region and to compromise cognitive functions. We clarify using supportive literature the high sensitivity of overnight electroencephalography (EEG) in the detection of epileptiform discharges. Finally, we present the most important research questions around SEA and provide an overview of the possible solutions.

Spike ripples in striatum correlate with seizure risk in two mouse models

Epilepsy biomarkers from electroencephalogram recordings are routinely used to assess seizure risk and localization. Two widely adopted biomarkers include: (i) interictal spikes, and (ii) high frequency ripple oscillations. The combination of these two biomarkers, ripples co-occurring with spikes (spike ripples), has been proposed as an improved biomarker for the epileptogenic zone and epileptogenicity in humans and rodent models. Whether spike ripples translate to predict seizure risk in rodent seizure models is unknown. Further, recent evidence suggests ictal networks can include deep gray nuclei in humans. Whether pathologic spike ripples and seizures are also observed in the basal ganglia in rodent models has not been explored. We addressed these questions using local field potential recordings from mice with and without striatal seizures after carbachol or 6-hydroxydopamine infusions into the striatum. We found increased spike ripples in the interictal and ictal periods in mice with seizures compared to pre-infusion and post-infusion seizure-free recordings. These data provide evidence of electrographic seizures involving the striatum in mice and support the candidacy of spike ripples as a translational biomarker for seizure risk in mouse models.

Interictal Epileptiform Discharges are Task Dependent and are Associated with Lasting Electrocorticographic Changes

The factors that control the occurrence of interictal epileptiform discharges (IEDs) are not well understood. We suspected that this phenomenon reflects an attention-dependent suppression of interictal epileptiform activity. We hypothesized that IEDs would occur less frequently when a subject viewed a task-relevant stimulus compared with viewing a blank screen. Furthermore, IEDs have been shown to impair memory when they occur in certain regions during the encoding or recall phases of a memory task. Although these discharges have a short duration, their impact on memory suggests that they have longer lasting electrophysiological effects. We found that IEDs were associated with an increase in low-frequency power and a change in the balance between low- and high-frequency oscillations for several seconds. We found that the occurrence of IEDs is modified by whether a subject is attending to a word displayed on screen or is observing a blank screen. In addition, we found that discharges in brain regions in every lobe impair memory. These findings elucidate the relationship between IEDs and memory impairment and reveal the task dependence of the occurrence of IEDs.

A Unifying Theory for Autism: The Pathogenetic Triad as a Theoretical Framework

This paper presents a unifying theory for autism by applying the framework of a pathogenetic triad to the scientific literature. It proposes a deconstruction of autism into three contributing features (an autistic personality dimension, cognitive compensation, and neuropathological risk factors), and delineates how they interact to cause a maladaptive behavioral phenotype that may require a clinical diagnosis. The autistic personality represents a common core condition, which induces a set of behavioral issues when pronounced. These issues are compensated for by cognitive mechanisms, allowing the individual to remain adaptive and functional. Risk factors, both exogenous and endogenous ones, show pathophysiological convergence through their negative effects on neurodevelopment. This secondarily affects cognitive compensation, which disinhibits a maladaptive behavioral phenotype. The triad is operationalized and methods for quantification are presented. With respect to the breadth of findings in the literature that it can incorporate, it is the most comprehensive model yet for autism. Its main implications are that (1) it presents the broader autism phenotype as a non-pathological core personality domain, which is shared across the population and uncoupled from associated features such as low cognitive ability and immune dysfunction, (2) it proposes that common genetic variants underly the personality domain, and that rare variants act as risk factors through negative effects on neurodevelopment, (3) it outlines a common pathophysiological mechanism, through inhibition of neurodevelopment and cognitive dysfunction, by which a wide range of endogenous and exogenous risk factors lead to autism, and (4) it suggests that contributing risk factors, and findings of immune and autonomic dysfunction are clinically ascertained rather than part of the core autism construct.

Reliability of Medical History Reporting in Older Adults With and Without Cognitive Impairment

BACKGROUND

Clinical diagnosis of cognitive disorders depends on accurate reporting of medical history, yet little is known about the reliability and the validity of such reports, particularly in older patients with and without cognitive impairment.

METHODS

In 2 studies, we examined the reliability and the validity of reported histories of select medical events in adults with and without cognitive impairment from a large national cohort.

RESULTS

Information from subjects (N1 = 3664), obtained from 2 time points, 6 to 12  months apart, was consistent across most medical events, regardless of the diagnostic group (range = 97.6%-100% agreement; Cohen κ range = 0.712-0.945), with few exceptions. Validity analyses (N2 = 382) revealed that 3 of 5 medical events assessed showed substantial agreement between self-report information and clinician diagnosis.

CONCLUSIONS

These data represent some of the first to demonstrate the reliability and the validity of reported select medical events in older adults with and without cognitive impairment.

Use of the Modified Atkins Diet in Intractable Pediatric Epilepsy

Background and Purpose

The modified Atkins diet is a less restrictive alternative to the ketogenic diet (KD), allowing unlimited protein, fat, calories, and fluid intake. Moreover, it can be started on an outpatient basis without requiring a fast. This study evaluated the efficacy, tolerability, and compliance of the modified Atkins diet in intractable pediatric epilepsy.

Methods

We retrospectively reviewed the medical records of 26 pediatric patients (10 males and 16 females) with intractable epilepsy who were treated using the modified Atkins diet at Samsung Medical Center from January 2011 to March 2017.

Results

The mean age at initiation of the modified Atkins diet was 10.9 (range, 2–21) years. The diet was continued for a mean duration of 5.9 (range, 1–16) months. After 6 months, 10 (38.5%) remained on the diet, of whom six (60%) had > 50% seizure reduction and two (20%) became seizure free. Four of 26 patients (15.4%) reported side effects of the diet, including constipation (n = 2) and lipid profile elevations (n = 2). Mean body mass index (BMI) was reduced from 22.6 to 20.9 kg/m² (p < 0.05) in 13 patients who continued the diet for ≥ 3 months. Four of these patients (30.8%) were overweight (BMI > 25 kg/m²) before initiating the diet and were satisfied with their BMI changes from a mean of 30.3 to 27 kg/m² (p < 0.05). Food refusal (n = 3) and poor parental compliance (n = 3) were the common reasons cited for cessation.

Conclusions

The modified Atkins diet may be an alternative treatment option for children with intractable epilepsy who are unable to tolerate KD because of food intake-related restrictiveness or adverse effects. The continuous support of healthcare professionals and families plays a key role in diet maintenance.

Prevalence and patterns of anti-epileptic medication prescribing in the treatment of epilepsy in older adults with intellectual disabilities

BACKGROUND

The prevalence of epilepsy is higher in people with intellectual disability (ID) and increases with the degree of ID. Although life expectancy for people with ID is increasing, people with ID coexisting with epilepsy have a higher mortality rate, particularly those who had recent seizures. There have been few observational studies of the prevalence and patterns of anti-epileptic prescribing among older people with ID and epilepsy. The aim of this study was to investigate prevalence and patterns of anti-epileptic prescribing in the treatment of epilepsy in a representative population of older people with ID and epilepsy.

METHODS

This was an observational cross-sectional study from wave 1 (2009/2010) of Intellectual Disability Supplement to the Irish Longitudinal Study on Aging, a nationally representative sample of 753 persons with ID aged between 41 and 90 years. Participants and/or proxies recorded medicines used on a regular basis and reported doctor's diagnosis of epilepsy; medication data were available for 736 (98%). Prescribing of anti-epileptic drugs (AEDs) for epilepsy in those with a doctor's diagnosis of epilepsy (N = 205) was the primary exposure of interest for this study. Participant exposure to these AEDs was then categorised into AED monotherapy and polytherapy. Participants/carers reported seizure frequency, when epilepsy was last reviewed and which practitioner reviewed epilepsy. In addition, medications that may lower the seizure threshold that were listed in the Maudsley prescribing guidelines in psychiatry were examined.

RESULTS

Of the 736 participants with reported medicines use, 38.9% (n = 287) were exposed to AEDs, and 30.6% (225) had a doctor's diagnosis of epilepsy. Of those with epilepsy (n = 225), 90.9% (n = 205) reported concurrent use of AEDs and epilepsy. Of these 205 participants, 50.3% (n = 103) were exposed to AED polytherapy, and 63 different polytherapy regimes were reported. The most frequently reported AEDs were valproic acid (n = 100, 48.7%), carbamazepine (n = 89, 46.3%) and lamotrigine (n = 57, 27.8%). In total, 13.7% had a concurrent psychotropic, which should be avoided in epilepsy, and 32.6% had a psychotropic where caution is required. Antipsychotics with potential epileptogenic potential accounted for 80% of these medications. Of those with AED polytherapy (n = 103), 29.5% (28) reported being seizure free for the previous 2 years.

CONCLUSIONS

Prevalence of epilepsy was high among older people with ID, and half were exposed to two or more AEDs. Despite the use of AED therapy, over half had seizures in the previous 2 years. As the primary goals of optimal AED treatment are to achieve seizure freedom without unacceptable adverse effects, this was not achievable for many older patients with ID and epilepsy. Our findings indicated that people with ID and epilepsy were often exposed to psychotropic medications that may lower the seizure threshold. Regular review of epilepsy and medicines (including medicines that may interact with AEDs or lower the seizure threshold) by multidisciplinary teams working to agreed standards may improve quality of prescribing. Improved exchange of information and coordination of care between specialists and primary care practitioners in line with expert consensus recommendations could bring substantial benefit.

Cognitive function in Nigerian children with newly diagnosed epilepsy: a preliminary report

Introduction

Epilepsy has long been associated with cognitive dysfunction and educational underachievement. The purpose of the study was to describe the baseline findings from a larger prospective study.

Methods

New cases of epilepsy aged 6-16 years seen at a paediatric neurology clinic in Ibadan, Nigeria were evaluated for any evidence of cognitive impairment. Intelligence quotient (IQ) of the participants was measured using the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV). Scores on cognitive subtests and Full Scale IQ (FSIQ) were computed and association between the subsets scores and seizure variables were calculated.

Results

40 children, 24 males and 16 females were studied and their ages ranged from 6 to 16 years with a mean of 10.8 (SD=3.0) years. Global intellectual functioning as measured by the WISC-IV was in the normal range (FSIQ scores <85) for 52.5% (n = 21) of the participants and the remaining participants (47.5%) scored between the borderline and severe category for intellectual disability. The strongest correlation was between ‘caregiver's assessment of school performance’ and FSIQ, (r = 0.70; p< 0.001). Age at onset of epilepsy and seizure type had no significant association with scores on the WISC-IV composite scores.

Conclusion

There is a high prevalence of significant cognitive dysfunction in Nigerian children with epilepsy, even in the absence of any known brain insult. All children with epilepsy should have routine IQ assessment following diagnosis, in order to allow for early intervention when indicated, and thus, improved outcomes.

Long-Term Functional Outcome of Pediatric Stroke Survivors

PURPOSE

To examine the long-term functional, psychosocial, and medical outcome of pediatric stroke survivors.

METHOD

This was a descriptive survey performed on patients with childhood stroke who participated in an earlier study. Measures included the Vineland Adaptive Behavior Scales (VABS) and the Diener Satisfaction with Life Scale. Current information on living situation, school placement, employment, and medical outcome were obtained.

RESULTS

Twenty-nine (58%) patients participated. The mean age was 19.3 years (SD = 6.6), mean age of onset of stroke was 7.0 years (SD = 5.4), and mean follow-up time was 11.9 years (SD = 3.9). Diagnoses included hemorrhagic (31%) and ischemic (69%) stroke. All but one adult had finished high school, and the majority of participants had gone to college. 60% of patients over age 16 were employed. The average VABS levels for communication, daily living skills, socialization, and adaptive behavior fell into the moderately low range. Use of seizure medications and ADL dependence were the predictors for lower VABS levels (p <.05). Younger age, ischemic stroke, and previous dependence in mobility were risk factors for lower scores for the self-care domain, but not for lower life satisfaction. Patients who scored below adequate on VABS tended toward lower life satisfaction.

CONCLUSION

Pediatric stroke survivors had good educational and mobility outcomes, but communication, ADL, and socialization fell into the low-moderate range. The different predictors of functional and subjective quality of life outcomes suggest that functional outcomes may mediate the relations between medical factors and satisfaction with life.

Conceptualizing lennox-gastaut syndrome as a secondary network epilepsy

Lennox–Gastaut Syndrome (LGS) is a category of severe, disabling epilepsy, characterized by frequent, treatment-resistant seizures, and cognitive impairment. Electroencephalography (EEG) shows characteristic generalized epileptic activity that is similar in those with lesional, genetic, or unknown causes, suggesting a common underlying mechanism. The condition typically begins in young children, leaving many severely disabled with recurring seizures throughout their adult life. Scalp EEG of the tonic seizures of LGS is characterized by a diffuse high-voltage slow transient evolving into generalized low-voltage fast activity, likely reflecting sustained fast neuronal firing over a wide cortical area. The typical interictal discharges (runs of slow spike-and-wave and bursts of generalized paroxysmal fast activity) also have a “generalized” electrical field, suggesting widespread cortical involvement. Recent brain mapping studies have begun to reveal which cortical and subcortical regions are active during these “generalized” discharges. In this critical review, we examine findings from neuroimaging studies of LGS and place these in the context of the electrical and clinical features of the syndrome. We suggest that LGS can be conceptualized as “secondary network epilepsy,” where the epileptic activity is expressed through large-scale brain networks, particularly the attention and default-mode networks. Cortical lesions, when present, appear to chronically interact with these networks to produce network instability rather than triggering each individual epileptic discharge. LGS can be considered as “secondary” network epilepsy because the epileptic manifestations of the disorder reflect the networks being driven, rather than the specific initiating process. In this review, we begin with a summation of the clinical manifestations of LGS and what this has revealed about the underlying etiology of the condition. We then undertake a systematic review of the functional neuroimaging literature in LGS, which leads us to conclude that LGS can best be conceptualized as “secondary network epilepsy.”

Alterations of 5-HT1A receptor-induced G-protein functional activation and relationship to memory deficits in patients with pharmacoresistant temporal lobe epilepsy

The 5-hydroxytryptamine-1A (5-HT1A) receptors are known to be involved in the inhibition of seizures in epilepsy. Moreover, studies propose a role for the 5-HT1A receptor in memory function; it is believed that the higher density of this receptor in the hippocampus plays an important role in its regulation. Positron emission tomography (PET) studies in patients with mesial temporal lobe epilepsy (mTLE) have demonstrated that a decrease in 5-HT1A receptor binding in temporal regions may play a role in memory impairment. The evidences lead us to speculate whether this decrease in receptor binding is associated with a reduced receptor number or if the functionality of the 5-HT1A receptor-induced G-protein activation and/or the second messenger cascade is modified. The purpose of the present study is to determine 5-HT1A receptor-induced G-protein functional activation by 8-OH-DPAT-stimulated [(35)S]GTPγS binding assay in hippocampal tissue of surgical patients with mTLE. We correlate functional activity with epilepsy history and neuropsychological assessment of memory. We found that maximum functional activation stimulation values (Emax) of [(35)S]GTPγS binding were significantly increased in mTLE group when compared to autopsy samples. Furthermore, significant correlations were found: (1) positive coefficients between the Emax with the age of patient and frequency of seizures; (2) negative coefficients between the Emax and working memory, immediate recall and delayed recall memory tasks. Our data suggest that the epileptic hippocampus of patients with mTLE presents an increase in 5-HT1A receptor-induced G-protein functional activation, and that this altered activity is related to age and seizure frequency, as well as to memory consolidation deficit.

The challenges and innovations for therapy in children with epilepsy

Major advances have been made in the diagnosis, evaluation and management of children with epilepsy over the past 15 years. There has been a marked increase in genetic diagnoses of a number of key childhood-onset epilepsy syndromes, such as Dravet syndrome, which has been linked to mutations in the SCN1A gene. The reorganization and reclassification of epilepsies, devised by the International League Against Epilepsy, has stimulated specialists to reassess their diagnostic practices; however, many studies have not addressed the global issues in treating children with epilepsy-specifically, the challenges of diagnosis through to optimal, and appropriate, therapeutic management. Also, Class I evidence-based data that are needed as a foundation for the development of treatment guidelines worldwide are lacking. Epilepsy is common, and the impact of this disease crosses age ranges and should be managed at all levels of care from community to quaternary care. In this Review, existing data and new therapeutic management approaches are discussed with the aim of highlighting the incidence of standard practices that may not be based on clinical evidence.

Study of psychiatric comorbidities in epilepsy by using the Mini International Neuropsychiatric Interview

BACKGROUND

Epilepsy is a neurological condition affecting men and women of all age groups and is associated with psychiatric comorbid conditions. There is a paucity of published data available regarding psychiatric comorbid conditions in patients with epilepsy (PWEs) from developing countries.

METHODS

We compared the psychiatric comorbid conditions in 80 PWEs, 80 patients with asthma (asthma control (AC) subjects), and 80 healthy controls (normal control (NC) subjects) using the Mini International Neuropsychiatric Interview (MINI) for the diagnosis of Axis I psychiatric disorders.

RESULTS

Psychiatric comorbid conditions are more common in PWEs (32.50%) as compared with the AC (17.5%) and NC (7.5%) subjects. Longer duration of seizures, increased frequency of seizures, recent recurrence of seizures, anticonvulsant polypharmacy, poor compliance with medications, and family history of seizures were associated with increased psychiatric comorbidity.

CONCLUSION

Patients with epilepsy are more likely to have psychiatric comorbid disorders compared with the other patients with chronic illness or with the healthy controls. It is of immense clinical importance to identify the comorbid psychiatric disorders in PWEs as the treatment of these disorders apart from a good seizure control may significantly improve their quality of life.

Real-life memory and spatial navigation in patients with focal epilepsy: ecological validity of a virtual reality supermarket task

Ecological assessment and training of real-life cognitive functions such as visual-spatial abilities in patients with epilepsy remain challenging. Some studies have applied virtual reality (VR) paradigms, but external validity of VR programs has not sufficiently been proven. Patients with focal epilepsy (EG, n=14) accomplished an 8-day program in a VR supermarket, which consisted of learning and buying items on a shopping list. Performance of the EG was compared with that of healthy controls (HCG, n=19). A comprehensive neuropsychological examination was administered. Real-life performance was investigated in a real supermarket. Learning in the VR supermarket was significantly impaired in the EG on different VR measures. Delayed free recall of products did not differ between the EG and the HCG. Virtual reality scores were correlated with neuropsychological measures of visual-spatial cognition, subjective estimates of memory, and performance in the real supermarket. The data indicate that our VR approach allows for the assessment of real-life visual-spatial memory and cognition in patients with focal epilepsy. The multimodal, active, and complex VR paradigm may particularly enhance visual-spatial cognitive resources.

Specific impairment of "what-where-when" episodic-like memory in experimental models of temporal lobe epilepsy

Episodic memory deficit is a common cognitive disorder in human temporal lobe epilepsy (TLE). However, no animal model of TLE has been shown to specifically replicate this cognitive dysfunction, which has limited its translational appeal. Here, using a task that tests for nonverbal correlates of episodic-like memory in rats, we show that kainate-treated TLE rats exhibit a selective impairment of the "what-where-when" memory while preserving other forms of hippocampal-dependent memories. Assisted by multisite silicon probes, we recorded from the dorsal hippocampus of behaving animals to control for seizure-related factors and to look for electrophysiological signatures of cognitive impairment. Analyses of hippocampal local field potentials showed that both the power of theta rhythm and its coordination across CA1 and the DG-measured as theta coherence and phase locking-were selectively disrupted. This disruption represented a basal condition of the chronic epileptic hippocampus that was linked to different features of memory impairment. Theta power was more correlated with the spatial than with the temporal component of the task, while measures of theta coordination correlated with the temporal component. We conclude that episodic-like memory, as tested in the what-where-when task, is specifically affected in experimental TLE and that the impairment of hippocampal theta activity might be central to this dysfunction.

The cognitive effects of interictal epileptiform EEG discharges and short nonconvulsive epileptic seizures

PURPOSE

Educational difficulties or even severe cognitive deterioration is seen in many childhood epilepsy syndromes. Many of those cognitive deficits are related directly to the brain disorder underlying the epilepsy syndrome. However, in other types of epilepsy, the epileptic seizures and/or epileptiform activity can be the dominant factor. This is especially unknown for the more "subtle" short nonconvulsive seizure types. For this reason, we analyzed a new cohort of children.

METHODS

A cross-sectional study of 188 children with epilepsy. Electroencephalography (EEG)-video recordings and cognitive testing were performed simultaneously. The results of children with short nonconvulsive seizures during a 2-h testing session were compared with all children with epilepsy without seizures during the 2-h cognitive testing session and with controls without epilepsy. In a second analysis the cognitive effects of frequency of epileptiform EEG discharges were analyzed.

KEY FINDINGS

The cognitive effects of short nonconvulsive seizures were large, ranging from 0.5 to 1 standard deviation and concerned global cognitive function, speed of central information processing, and memory function. In children without seizures during cognitive testing, the occurrence of frequent epileptiform discharges showed more subtle effects. These effects were independent from the occurrence of short nonconvulsive seizures.

SIGNIFICANCE

We concluded that although the effect is less pronounced in number of areas involved and magnitude, the type of association between frequent epileptiform activity (>1% of the time) and cognitive function in children with epilepsy is comparable to the association between short nonconvulsive seizures and cognitive function.

An isolated epileptic seizure elicits learning impairment which could be prevented by melatonin

We tested the relation between a single short tonic-clonic seizure elicited by flurothyl vapors and changes of learning in Morris water maze (MWM) in Wistar rats. Oxidative stress usually accompanies seizures. Large melatonin doses were applied immediately before and after seizures to test consequences on learning impairment. One hour of hypobaric hypoxia (8000 m) three days prior to the seizure served as an activator of intrinsic antioxidant systems. Learning in MWM (7 days) started 24 h after seizures. Following seizures, latencies in MWM were longer than in controls and were shortened by hypoxia and preventive melatonin application. Melatonin was also applied before hypoxia to influence free radical (FR) production and intrinsic antioxidant activation. Some behavioral characteristics were changed and preconditioning effect of hypoxia was reduced. Melatonin after seizure (150 s and 6 h) had negligible effect. Results allow us to hypothesize about the role of FR and the beneficial effect of melatonin on the behavioral consequences of seizures.

Cognitive functioning and behaviour of epileptic children in parents' assessment

BACKGROUND AND PURPOSE

Cognitive functioning and behaviour of chronically ill children are affected by many factors, including anxiety due to hospitalization, persistent symptoms of sickness and adverse side effects of medications. The aim of this work was to seek out parents' opinion concerning cognitive functioning and behaviour of children with epilepsy.

MATERIAL AND METHODS

The study comprised 156 children with epilepsy aged 7-18 and treated in the Department of Developmental Neurology at Karol Marcinkowski Poznan University of Medical Sciences and in an outpatient clinic. The research tool used was the questionnaire Quality of Life in Childhood Epilepsy (QOLCE) completed by parents. Assessment of cognitive functioning and behaviour was based on the analysis of the areas V (cognitive processes) and VII (behaviour).

RESULTS

Parents assessed children's functioning in the areas of cognitive processes and behaviour at a similar level - 55 points. In the area of cognitive processes, concentration while performing some tasks and reading was assessed as the worst. A significant difference in caregivers' assessment was found according to age, frequency of seizures and duration of disease. In the area analysing the child's behaviour, parents indicated getting angry easily and not being upset by other people's opinions. The display of aggression towards others got the lowest number of comments.

CONCLUSIONS

The children's functioning was assessed by parents as rather poor in both analysed areas. Parents of children treated with polytherapy noticed more difficulties in cognitive functioning and behaviour than parents of children treated with one medication.

Hippocampal-dependent spatial memory in the water maze is preserved in an experimental model of temporal lobe epilepsy in rats

Cognitive impairment is a major concern in temporal lobe epilepsy (TLE). While different experimental models have been used to characterize TLE-related cognitive deficits, little is known on whether a particular deficit is more associated with the underlying brain injuries than with the epileptic condition per se. Here, we look at the relationship between the pattern of brain damage and spatial memory deficits in two chronic models of TLE (lithium-pilocarpine, LIP and kainic acid, KA) from two different rat strains (Wistar and Sprague-Dawley) using the Morris water maze and the elevated plus maze in combination with MRI imaging and post-morten neuronal immunostaining. We found fundamental differences between LIP- and KA-treated epileptic rats regarding spatial memory deficits and anxiety. LIP-treated animals from both strains showed significant impairment in the acquisition and retention of spatial memory, and were unable to learn a cued version of the task. In contrast, KA-treated rats were differently affected. Sprague-Dawley KA-treated rats learned less efficiently than Wistar KA-treated animals, which performed similar to control rats in the acquisition and in a probe trial testing for spatial memory. Different anxiety levels and the extension of brain lesions affecting the hippocampus and the amydgala concur with spatial memory deficits observed in epileptic rats. Hence, our results suggest that hippocampal-dependent spatial memory is not necessarily affected in TLE and that comorbidity between spatial deficits and anxiety is more related with the underlying brain lesions than with the epileptic condition per se.

Definition of the postictal state: when does it start and end?

The postictal state is the abnormal condition occurring between the end of an epileptic seizure and return to baseline condition. Applying this definition operationally can be difficult, especially for complex partial seizures, where cognitive and sensorimotor impairments merge imperceptibly into the postictal state. Many patients are unaware of even having had a seizure. Electroencephalography sometimes helps to distinguish ictal from postictal periods, but may demonstrate focal slowing both during and after a seizure. Epileptiform electroencephalographic changes do not always correspond precisely to behavioral changes, especially with scalp recordings. The postictal state ends at the interictal state, but this too can be ambiguous. Interictal spikes and spike-waves can be associated with cognitive and behavioral impairments, suggesting that they may represent fragments of ictal episodes. Except where boundaries are clear, it is better to describe a sequence of behaviors and electroencephalographic changes, without labeling arbitrary stages as being ictal or postictal.

The cognitive impact of epileptiform EEG discharges and short epileptic seizures: relationship to characteristics of the cognitive tasks

OBJECTIVE

We analyzed the effect of task dimensions (information processing demand; duration of the test; input modality) on the occurrence and cognitive impact of epileptiform EEG discharges (EEDs) or subtle epileptic seizures.

METHODS

One hundred ninety-nine children, aged 6-17 years, were included consecutively in a prospective standardized study. All children were assessed with EEG, which was synchronized with a computerized cognitive FePsy test system.

RESULTS

No association was found between the occurrence of EEDs or subtle epileptic seizures and the three task dimensions introduced in our study. The Computerized Visual Searching Task (CVST) appeared to be particularly sensitive to direct cognitive effects of EEDs. The CVST and the three memory tests--Corsi's Block Tapping and recognition of words/figures--were sensitive to the cognitive effects of subtle epileptic seizures.

CONCLUSION

Our results do not indicate a distinctive effect of information processing demand, duration of the test, or input modality on the occurrence of EEDs or subtle epileptic seizures. Effects on the impact on cognition are found when these three factors are combined.

Baseline cognition, behavior, and motor skills in children with new-onset, idiopathic epilepsy

AIM

Epilepsy is associated with difficulties in cognition and behavior in children. These problems have been attributed to genetics, ongoing seizures, psychosocial issues, underlying abnormality of the brain, and/or antiepileptic drugs. In a previous study, we found baseline cognitive differences between children with partial versus generalized and convulsive versus non-convulsive seizures. Measures in that study focused primarily on IQ scores. In the present study, we assessed baseline function with respect to new learning, attention, and memory, thus providing a more comprehensive profile than our previous study.

METHOD

We examined 57 children (42 females, 15 males), aged 6 to 17 years (mean 10y 1mo, SD 2y 9mo), with new-onset, idiopathic epilepsy, using tests of cognitive function reflective of new learning, memory, and attention. Seizures were classified as generalized convulsive (n=5), generalized non-convulsive (n=18), or focal (n=34). Focal seizures were divided into unilateral versus bilateral independent foci, and presence versus absence of secondary generalization.

RESULTS

Attention was a particular area of weakness across all groups. The Vocabulary score of an intelligence screen was higher for the focal seizure groups (p=0.012), primarily because of a difference between the unilateral focal and the primary generalized groups (p<0.047). Children with generalized, non-convulsive seizures performed significantly worse than the focal group on a measure of short-term auditory memory (p=0.019). All groups performed poorly on a test of visual-motor speed.

INTERPRETATION

These findings suggest intrinsic abnormalities in children with new-onset, idiopathic epilepsy at baseline.

Correlation between memory, proton magnetic resonance spectroscopy, and interictal epileptiform discharges in temporal lobe epilepsy related to mesial temporal sclerosis

OBJECTIVE

The aim of the study described here was to examine the relationship between memory function, proton magnetic resonance spectroscopy ((1)H-MRS) abnormalities, and interictal epileptiform discharge (IED) lateralization in patients with temporal lobe epilepsy (TLE) related to unilateral mesial temporal sclerosis.

METHODS

We assessed performance on tests of memory function and intelligence quotient (IQ) in 29 right-handed outpatients and 24 controls. IEDs were assessed on 30-minute-awake and 30-minute-sleep EEG samples. Patients had (1)H-MRS at 1.5 T.

RESULTS

There was a negative correlation between IQ (P=0.031) and Rey Auditory Verbal Learning Test results (P=0.022) and epilepsy duration; between(1)H-MRS findings and epilepsy duration (P=0.027); and between N-acetylaspartate (NAA) levels and IEDs (P=0.006) in contralateral mesial temporal structures in the left MTS group. (1)H-MRS findings, IEDs, and verbal function were correlated.

CONCLUSIONS

These findings suggest that IEDs and NAA/(Cho+Cr) ratios reflecting neural metabolism are closely related to verbal memory function in mesial temporal sclerosis. Higher interictal activity on the EEG was associated with a decline in total NAA in contralateral mesial temporal structures.

Recurrent seizures induce a reversible impairment in a spatial hidden goal task

A major question concerning the learning and memory deficits characteristic of epilepsy is the relative importance of the initial insult that leads to recurrent, unprovoked seizures versus the seizures themselves. A related issue is whether seizure-induced cognitive decline is permanent or reversible when convulsions cease. To address these problems, adult rats were extensively trained in the "spatial accuracy task," a dry-land analog of the Morris water maze. This task allows the rat's estimate of the location of a hidden goal zone to be repeatedly measured within each behavioral session. One aim was to measure, in well-trained animals, the time course of any cognitive impairment caused by a daily flurothyl-induced generalized seizure over 11 days. A second aim was to look for possible recovery during 9 subsequent days with no seizures. We saw a cumulative degradation in spatial performance during the seizure days and reversal of the deficit after seizures were stopped such that performance returned to baseline. Interestingly, the rate of learning to an asymptote, the rate of performance decline during one-per-day seizures and the rate of relearning during the recovery period were all similar. Given that the hippocampus plays an important role in spatial memory and that it is the brain structure most vulnerable to abnormal excitation the implication is that the hippocampus remains essential for precise spatial navigation even after prolonged training in locating a fixed goal zone. Clinically, this finding questions the assumption that patients who experience seizures should return to a baseline cognitive level within hours.

Growing up with epilepsy: a two-year investigation of cognitive development in children with new onset epilepsy

PURPOSE

To characterize patterns and determinants of normal and abnormal cognitive development in children with new onset epilepsy compared to healthy controls.

METHODS

Longitudinal (2-year) cognitive growth was examined in 100 children, age 8-18 years, including healthy controls (n = 48) and children with new onset epilepsy (n = 52). Cognitive maturation was examined as a function of the presence/absence of two neurobehavioral comorbitiies (attention deficit hyperactivity disorder and/or academic problems) identified at the time of epilepsy diagnosis. Groups were compared across a comprehensive neuropsychological battery assessing intelligence, academic achievement, language, memory, executive function, and psychomotor speed.

RESULTS

Children with new onset epilepsy without neurobehavioral comorbidities were comparable to healthy controls at baseline, rate of cognitive development, and follow-up assessment across all neuropsychological domains. In contrast, the presence of neurobehavioral comorbidities was associated with significantly worse baseline and prospective cognitive trajectories across all cognitive domains, especially executive functions.

CONCLUSION

The presence of neurobehavioral comorbidities at the time of epilepsy onset is a major marker of abnormal cognitive development both prior to and after the onset of epilepsy.

Epilepsy and suicide: pathogenesis, risk factors, and prevention

Depression and suicide tendencies are common in chronic diseases, especially in epilepsy and diabetes. Suicide is one of the most important causes of death, and is usually underestimated. We have analyzed several studies that compare mortality as a result of suicide in epileptic patients and in the general population. All the studies show that epileptic patients have a stronger tendency toward suicide than healthy controls. Moreover it seems that some kinds of epilepsy have a higher risk for suicide (temporal-lobe epilepsy). Among the risk factors are surgery therapy (suicide tendency five times higher than patients in pharmacological therapy), absence of seizures for a long time, especially after being very frequent, and psychiatric comorbidity (major depression, anxiety-depression disorders, personality disorders, substance abuse, psychoses). The aim of the review was to analyze the relationship between suicide and epilepsy, to identify the major risk factors, and to analyze effective treatment options.

Neuropsychological deficits in monozygotic twins with childhood epilepsy with occipital paroxysms

We report a unique pair of monozygotic twins with childhood epilepsy with occipital paroxysms who showed subtle cognitive deficits. The twin with a more severe epileptic disorder showed a more severe impairment of cognitive functioning. We suggest that epileptic focus may act as an element of disturbance in the development of primary functions and may give rise to a neuropsychological impairment proportionate to the severity of the epileptic activity.

Postictal single-cell firing patterns in the hippocampus

PURPOSE

Patients with epilepsy have varying degrees of postictal impairment including confusion and amnesia. This impairment adds substantially to the disease burden of epilepsy. However, the mechanism responsible for postictal cognitive impairment is unclear. The purpose of this study was to study single-cell firing patterns in hippocampal cells after spontaneous seizures in rats previously subjected to status epilepticus.

METHODS

In this study, we monitored place cells and interneurons in the CA1 region of the hippocampus before and after spontaneous seizures in six epileptic rats with a history of status epilepticus. Place cells fire action potentials when the animal is in a specific location in space, the so-called place field. Place cell function correlates well with performance in tasks of visual-spatial memory and appears to be an excellent surrogate measure of spatial memory.

RESULTS

Twelve spontaneous seizures were recorded. After the seizures, a marked decrease in firing rate of action potentials from place cells was noted, whereas interneuron firing was unchanged. In addition, when place cell firing fields persisted or returned, they had aberrant firing fields with reduced coherence and information content. In addition to postictal suppression of firing patterns, seizures led to the emergence of firing fields in previously silent cells, demonstrating a postictal remapping of the hippocampus.

CONCLUSIONS

These findings demonstrate that postictal alterations in behavior are not due solely to reduced neuronal firing. Rather, the postictal period is characterized by robust and dynamic changes in cell-firing patterns resulting in remapping of the hippocampal map.

Cognitive impairment in juvenile myoclonic epilepsy

BACKGROUND AND PURPOSE

Cognitive impairments are frequent consequences of epilepsy, with intellectual ability reportedly being lower in patients with idiopathic generalized epilepsies than in the general population. However, neuropsychological investigations have been rarely performed in patients with juvenile myoclonic epilepsy (JME). We aimed to quantify the cognitive function in JME patients using various neuropsychological tests.

METHODS

We compared cognitive function in 27 JME patients with that in 27 healthy volunteers using tests examining cognitive performance, such as the verbal and visual memory, frontal function, attention, IQ score, and mood. In the JME group, we examined risk factors for cognitive function such as age, sex, family history, education level, age at seizure onset, seizure frequency, EEG abnormality, disease duration, and previous intake of antiepileptic drugs.

RESULTS

Verbal learning was significantly lower in JME patients than in controls, and attention and verbal fluency were impaired in JME patients compared with controls. However, general intellectual ability and mood did not differ between the groups. Early onset of seizure and long duration of disease were closely related to impaired cognitive function.

CONCLUSIONS

JME patients may exhibit impaired cognitive function, in terms of memory and execution, despite having normal intelligence and mood.

Do recent seizures and recent changes in antiepileptic drugs impact performances on neuropsychological tests in subtle ways that might easily be missed?

PURPOSE

The possibility that a recent seizure or a recent change in antiepileptic medication might produce an occult change in neuropsychological performance is of interest, and especially so in the context of evaluation for epilepsy surgery. Such an evaluation is often done in a setting of video-EEG monitoring where a strong effort is made to produce seizures as quickly as possible with abrupt changes in medication, alterations in sleep, etc., which could impact the validity of neuropsychological findings.

METHODS

A total of 126 adults were studied who had seizures of strictly temporal origin (47 right, 79 left) and whose recent medication history and seizure occurrence prior to testing was as clear as possible. All were tested with an extensive neuropsychological battery with great attention to giving tests only when the patients appeared clinically not to be suffering from recent seizures (seizures occurring on the day of testing or on the day prior to testing) or medication change effects. The cognitive correlates of side of seizures were also evaluated in order to provide a strength-of-effect comparison with recency of AED changes and seizures.

RESULTS

Findings from three-way ANOVA showed a possible slight adverse effect of recent AED change, no effects of recent seizures, and a sizeable relationship with side of seizures. A simultaneous consideration of all three of these variables did not provide additional findings of interest.

CONCLUSIONS

Although it is not possible to completely rule out some subtle cognitive effects of recent changes in medication or recent seizures, this investigation does not provide evidence for such effects when the neuropsychological evaluation is conducted carefully with no testing during any questionable or definite postictal periods.

Neuropsychological profile of patients with juvenile myoclonic epilepsy: a controlled study of 50 patients

The purpose of this study was to verify possible cognitive dysfunction in patients with juvenile myoclonic epilepsy (JME) and its relationship to factors related to epilepsy and schooling. Fifty subjects diagnosed with JME and 50 controls underwent neuropsychological assessment evaluating intellectual functions, attention, memory, executive functions, and language. The patients were further divided into two subgroups on the basis of educational level: < or = 11 and >11 years of formal education. Participants diagnosed with JME scored significantly below age-, education-, and gender-matched controls on neuropsychological measures of attention, immediate verbal memory, mental flexibility, control of inhibition, working memory, processing speed, verbal delayed memory, visual delayed memory, naming, and verbal fluency. A positive correlation was observed between duration of epilepsy and cognitive decline. However, in the group of patients with >11 years of education, this correlation was not significant. In this series of patients with JME, neuropsychological evaluation suggests widespread cognitive dysfunction outside the limits of the frontal lobes. The duration of epilepsy correlated with cognitive decline, and patients with higher education manifested less progression of deficits.

Deterioration

Intellectual deterioration in epilepsy may be real or apparent. The latter refers to delay in cognitive development such that performance against age-related norms appears to drop. The former, real deterioration can occur due to concomitant degenerative neurological disease of which epilepsy is also a symptom, or it may happen as a consequence of one or more of a number of other factors. These include (1) direct effects of seizures and abnormal electroencephalogram activity on brain function, (2) traumatic brain injury secondary to seizures, including status epilepticus, (3) the influence of antiepileptic therapy, both drugs and surgery, on cognitive function, (4) psychosocial sequelae of diagnosis. Some epilepsy syndromes include intellectual deterioration as a frequent feature, with various causes. Developmental factors may also play a part. Cognitive functioning may be impaired by the presence of an epileptogenic lesion, and also in different ways and at different times by other brain areas involved with partial seizures, including irritative and functional deficit zones. Abnormal activity in these areas at critical periods in development may interact and disrupt pathways necessary for maturation of frontal lobe and limbic system functioning, leading to long-term neurological deficits. Increased understanding of the mechanisms by which this may happen raises intriguing possibilities for prevention and remediation.

Gender and suicidality prediction in epilepsy

The current study was carried out to compare the accuracy of suicidal risk prediction in patients with epilepsy for each gender separately and as a group (males+females). The discriminant function analysis was performed to create an algorithm for suicidal risk classification for males and females separately and as a group. The main characteristics of epilepsy, such as type and mean frequency of seizures and kind and mean daily dose of AEDs were used as independent variables. The accuracy of suicidality prediction is higher for each gender than for the joint group. There was a statistically significant difference between the joint group and male epileptic patients and a trend toward more precise suicidality prediction among men than women, although the discrepancies were not significant. It was concluded that gender is an important factor in suicidality prediction, and more precise prediction of suicidal risk is possible for male epileptic patients because of the better differentiation of suicide grades in males than in females.

Idiopathic epileptic syndromes and cognition

Epilepsy is frequently associated with cognitive impairments which result from various interacting factors. The present paper deals with the contribution of neuropsychology to the characterization of the type of epilepsy and the possible mechanisms underlying idiopathic epileptic syndromes. The non-lesional, so-called idiopathic epilepsies, constitute an interesting model for assessing the relationship between epileptiform EEG discharges and cognition. Among the idiopathic generalized epilepsies, disorders of social integration and personality have been frequently reported in juvenile myoclonic epilepsy (JME). Since similar disturbances are observed in frontal-lobe-lesioned patients, impairments in other frontal lobe functions (e.g. executive functions) might be expected in JME. This gives rise to speculation about the possible underlying pathophysiological mechanisms in JME. With regard to partial idiopathic epilepsies, benign childhood epilepsy with centrotemporal spikes (BCECTS) may provide a useful model for the study of the relationship between epileptiform EEG discharges in the peri-sylvian region and language functions. Furthermore, the description of mild cognitive dysfunctions in BCECTS, and their persistence into adulthood, can provide information about compensatory mechanisms and may allow for the generation of remedial strategies. Thus, 'lesional' neuropsychology has given way to 'dynamic' neuropsychology based on specific postulates. By using the cognitive profile to specify the mechanism underlying the behavioral disturbances observed in different types of epilepsy, neuropsychology may eventually contribute to a revision of the present classification of epileptic syndromes. In addition, the neuropsychological data may help predict the extent and limits of functional recovery and cerebral plasticity.

Seizure-related factors and non-verbal intelligence in children with epilepsy. A population-based study from Western Norway

PURPOSE

To study the relationship between seizure-related factors, non-verbal intelligence, and socio-economic status (SES) in a population-based sample of children with epilepsy.

METHODS

The latest ILAE International classifications of epileptic seizures and syndromes were used to classify seizure types and epileptic syndromes in all 6-12 year old children (N=198) with epilepsy in Hordaland County, Norway. The children had neuropediatric and EEG examinations. Of the 198 patients, demographic characteristics were collected on 183 who participated in psychological studies including Raven matrices. 126 healthy controls underwent the same testing. Severe non-verbal problems (SNVP) were defined as a Raven score at or <10th percentile.

RESULTS

Children with epilepsy were highly over-represented in the lowest Raven percentile group, whereas controls were highly over-represented in the higher percentile groups. SNVP were present in 43% of children with epilepsy and 3% of controls. These problems were especially common in children with remote symptomatic epilepsy aetiology, undetermined epilepsy syndromes, myoclonic seizures, early seizure debut, high seizure frequency and in children with polytherapy. Seizure-related characteristics that were not usually associated with SNVP were idiopathic epilepsies, localization related (LR) cryptogenic epilepsies, absence and simple partial seizures, and a late debut of epilepsy. Adjusting for socio-economic status factors did not significantly change results.

CONCLUSIONS

In childhood epilepsy various seizure-related factors, but not SES factors, were associated with the presence or absence of SNVP. Such deficits may be especially common in children with remote symptomatic epilepsy aetiology and in complex and therapy resistant epilepsies. Low frequencies of SNVP may be found in children with idiopathic and LR cryptogenic epilepsy syndromes, simple partial or absence seizures and a late epilepsy debut. Our study contributes to an overall picture of cognitive function and its relation to central seizure characteristics in a childhood epilepsy population and can be useful for the follow-up team in developing therapy strategies that meet the individual needs of the child with epilepsy.

Intelligence functions disorders in patients with complex partial epilepsy

OBJECTIVES: To compare the performance of patients with complex partial epilepsy with the normal controls in the subtests of an instrument used to assess intelligence function. METHOD: Fifty epileptic patients, whose ages ranged from 19 to 49 years and 20 normal controls without any neuropsychiatric disorders. The Wechsler-Bellevue adult intelligence test was applied in groups, epileptic patients and control subjects. This test is composed of several subtests that assess specific cognitive functions. A statistical analysis was performed using non-parametric tests. RESULTS: All the Wechsler-Bellevue subtests revealed that the intelligence functions of the patients were significantly inferior to that of the controls (p<0.05). This performance was supported by the patient's complaints in relation to their cognitive performance. CONCLUSION: Patients with complex partial epilepsy presented poorer results in the intelligence test when compared with individuals without neuropsychiatric disorders.

Study of attentional processes in children with idiopathic epilepsy by Conners' Continuous Performance Test

Before starting antiepilepsy therapy (T1) and after 1 year (T2), 19 children (7 female) affected by focal or generalized idiopathic epilepsy were considered with the aim of studying attention performance. All of the children received a neurological examination and clinical interview, electroencephalography (EEG) in wakefulness or sleep, and a standardized computerized measure of attention (Conners' Continuous Performance Test). At T1, 21% of the patients showed a specific attention disorder, and their percentage rose to 42% after 1 year, despite complete control of seizures. The prognosis was strongly correlated with (1) the presence of active seizures for a period of over 6 months, (2) the persistence of specific interictal abnormalities on an electroencephalogram at T2, and (3) the presence of emotional and behavioral disorders at the diagnosis of epilepsy. Our results confirm that attention disorders are frequent in children with idiopathic epilepsy. The Conners' Continuous Performance Test has proven useful both for diagnosis and follow-up over time.

Benigne epilepsietypische Potentiale des Kindesalters (Rolando-Spikes) - neurobiologische und neuropsychologische Befunde und ihre klinische Bedeutung in der Kinder- und Jugendpsychiatrie

Zusammenfassung: Einleitung: Die Rolando-Epilepsie ist das häufigste Epilepsie-Syndrom im Kindesalter. Sie ist elektroenzephalographisch charakterisiert durch das Auftreten von fokalen epilepsietypischen Potentialen, den sog. Rolando-Spikes (benigne epilepsietypische Potentiale des Kindesalters, BEPK). BEPK treten mit einer Häufigkeit von etwa 1,5 bis 2,4% bei Kindern auf; nur ein Zehntel erleidet epileptische Anfälle. Methoden: Diese Arbeit gibt einen Überblick über genetische, epidemiologische, radiologische, neurophysiologische, metabolische und neuropsychologische Befunde bei Kindern mit BEPK. Resultate: Der epileptologische Verlauf ist günstig, eventuell auftretende Anfälle sistieren spätestens mit der Pubertät; die epilepsietypischen Potentiale sind dann nicht mehr nachweisbar. Entgegen früherer Annahmen erstreckt sich das Symptomenspektrum über seltene Anfälle hinaus auf neuropsychologische Beeinträchtigungen und Verhaltensauffälligkeiten, auch bei Kindern ohne manifeste Anfälle. Der Einfluss der Rolando-Spikes auf die Entwicklung betroffener Kinder und ihr Verhalten ist unklar. Durch zwei Modelle wird versucht, den Zusammenhang von paroxysmaler EEG-Aktivität und neuropsychologischen Auffälligkeiten zu erklären. Das erste betrachtet die beobachtbaren Defizite als vorübergehende kognitive Beeinträchtigung infolge der epileptischen Aktivität; das zweite sieht als Ursache eine genetisch bedingte zerebrale Reifungsstörung mit enger Verwandtschaft zu Teilleistungsstörungen. Schlussfolgerung: Die Behandlungsnotwendigkeit neuropsychiatrischer Symptome bei Kindern mit BEPK ohne manifeste Anfälle wird derzeit kontrovers diskutiert.

The relative influence of epileptic EEG discharges, short nonconvulsive seizures, and type of epilepsy on cognitive function

PURPOSE

This study addressed whether cognitive impairment in children with epilepsy is caused by disease-related stable factors, such as the type of epilepsy, or by acute effects of paroxysmal epileptic activity such as epileptic EEG discharges. We studied a nonselected group with short nonconvulsive seizures, as these seizures may elude detection and may therefore persist over a longer period. In this group, the diagnostic issue is to differentiate between the combined effects of several epilepsy-related factors on cognition.

METHODS

All children were assessed with 32-channel EEG, synchronized with a computerized cognitive test system and a video-monitoring system. Recording time was 2 h. The primary inclusion criteria were unclear seizures and fluctuations in cognitive performance and/or frequent epileptic EEG discharges in a recent EEG.

RESULTS

One hundred fifty-two patients met the inclusion criteria; 31 patients appeared not to have a diagnosis of epilepsy and were used as a nonepilepsy control group. Our results show that type of epilepsy has an impact on stable cognitive functions, such as educational achievement. Paroxysmal epileptic activity (acute effects of seizures and epileptic EEG discharges) affects primarily transient mechanistic cognitive processes (alertness, mental speed).

CONCLUSIONS

These results suggest that the effects of paroxysmal epileptic activity on transient cognitive mechanisms may accumulate over time and consequently affect the more stable aspects of cognitive function such as educational achievement. The clinical relevance is that early detection of the cognitive impact of seizure-related activity and subsequent treatment may prevent its detrimental impact on cognitive and educational development.

Effects of epileptiform EEG discharges on cognitive function: is the concept of "transient cognitive impairment" still valid?

In this article we review the existing evidence on the cognitive impact of interictal epileptiform EEG discharges. Such cognitive impairment occurs exclusively in direct relation to episodes of epileptiform EEG discharges and must be distinguished from (post) ictal seizure effects and from the nonperiodic long-term "stable" interictal effects caused by the clinical syndrome or the underlying etiology. Especially in patients with short nonconvulsive seizures, characterized often by difficult-to-detect symptoms, the ictal or postictal effects may be overlooked and the resulting cognitive effects may be erroneously related to the epileptiform EEG discharges. The existing epidemiological data show that the prevalence of cognitive impairment during epileptiform EEG discharges is low. In one study 2.2% of the patients referred to a specialized epilepsy center for EEG recording showed a definite relationship between epileptiform EEG discharges and cognitive impairments ("transient cognitive impairment"). Several studies have sought to analyze to what extent cognitive impairment can be attributed to epileptiform EEG discharges among the other epilepsy factors (such as the effect of the clinical syndrome). These studies show that epileptiform EEG discharges have an additional and independent effect, but this effect is mild and limited to transient mechanistic cognitive processes (alertness, mental speed). This finding concurs with clinical studies that also reported only mild effects. In only exceptional cases are epileptiform EEG discharges the dominant factor explaining cognitive impairment. In addition, some studies have indicated that such mild effects may accumulate over time (when frequent epileptiform EEG discharges persist over years) and consequently result in effects on stable aspects of cognitive function such as educational achievement and intelligence. Hence, the clinical relevance is that early detection of cognitive effects of epileptiform EEG discharges and subsequent treatment may prevent a definite impact on cognitive and educational development. The disruptive effects of epileptiform EEG discharges on long-term potentiation, as established in animal experiments, may be one of the neurophysiological mechanisms underlying this accumulation. In conclusion the concept of "transient cognitive impairment" is still valid, but refinement of methodology has shown that a large proportion of presumed transient cognitive impairment can be attributed to subtle seizures, while interictal epileptic activity accounts for a much smaller part of the cognitive effects than previously thought. In particular cryptogenic partial epilepsies are associated with the risk of cognitive impairment. We hope that increased clinical awareness of this need for early detection will stimulate longitudinal and prospective research that eventually also will provide an answer to the questions of when and how epileptiform discharges that are not part of a seizure need to be treated.

Effect of the postictal state on visual-spatial memory in immature rats

Postictal cognitive impairment following seizures can last from minutes to days and be disabling to the patient. The purpose of this study was to compare the behavioral features of seizures with postictal memory impairment in young seizure-naive rats and rats with a prior history of status epilepticus (SE) and examine the relationship between postictal EEG changes and cognitive recovery. Following training in the water maze to asymptote levels of learning, rats with a prior history of SE and seizure-naive rats had flurothyl-induced generalized seizures and time to recovery to baseline was then measured. Following generalized seizures rats had impaired performance in the water maze with the duration of the cognitive deficits exceeding the length of the seizure. There was not a close relationship between duration of cognitive impairment and either latency to onset of seizure or duration. The animal's neurological status was a factor in the duration of cognitive impairment following seizures; while there were no differences between SE and seizure-naive rats in latency to seizure onset or duration of the seizures, animals with a prior history of SE had a longer period of impairment following a seizure than animals without such a history. Postictal cognitive impairment was associated with changes in theta activity in animals with a prior history of SEs but not in seizure-naive animals. Caffeine, when administered following the seizure, reduced postictal cognitive impairment in a dose-dependent manner. This study demonstrates that duration of postictal cognitive impairment is not directly related to duration of the seizure. The neurological status of the animal is a determining factor in duration of postictal impairment.

Short bursts of weak pulses break postictal inhibition in the neocortex of Wistar rats

PURPOSE

Postictal inhibition (PI) is a decrease in excitability that follows an epileptic seizure and decreases probability of new seizure occurrence. PI may involve both increased inhibition and persisting elevated excitation. Our experiments tested whether shorter trains of weak stimuli are able to unmask this residual increase of excitability during the PI.

METHODS

Four epileptic afterdischarges (ADs) were evoked by intense electrical stimulation (20 s, 8 Hz, current intensity at 5x threshold) of the neocortex in two groups (A, B) of Wistar rats. Before the first AD and during the 10-min interictal period, 8-Hz trains of four weak pulses (half of the intensity used for the AD triggering; 4P) were applied every 20 s in group B and a single pulse with similar parameters in group A.

RESULTS

The number of interictal epileptiform events evoked by 4P in the group B was significantly higher than that in the group A (evoked by single pulses) except after the second AD. Epileptic events were triggered by 4P also immediately after the AD termination.

CONCLUSIONS

It is apparent that weak stimulation can trigger epileptic phenomena during PI. Our results indicate that it is no longer possible to perceive PI only as persisting extreme and active inhibition. An appropriate stimulation can reveal more subtle (but important) excitatory events contributing to the functional status during the postictal period.

Neuropsychologic effects of frontal lobe epilepsy in children

Most published neuropsychologic studies on frontal lobe epilepsy have been performed on mixed groups of adults and adolescents with epilepsies of varying etiology. The cognitive profile of frontal lobe epilepsy in children has not been defined. The purpose of this study was to assess neuropsychologic performance in children with frontal lobe epilepsy. Intelligence and executive functions were examined in eight children (age 6 7/12 years to 13 11/12 years) with frontal lobe epilepsy. Performance was related to the focus side, seizure frequency, and age of epilepsy onset. Frontal lobe epilepsy was associated with a range of frontal dysfunctions, but IQ was generally spared. Left focus was associated with deficits in categorization, verbal long-term memory, and detailed visuospatial analysis. Frequent seizures correlated with attention difficulties and inability to inhibit impulsive responses. Children whose epilepsy appeared before age 6 years had reduced ability to change behavioral strategies. Frontal epileptic activity alone can cause selective frontal deficits, the severity and nature of which are related to side, seizure frequency, and age of epilepsy onset. These findings require confirmation on larger series of selected children.

Atypical Lennox-Gastaut syndrome successfully treated with removal of a parietal dysembryoplastic tumour

Focal brain lesions may be associated with the atypical form of Lennox-Gastaut syndrome (LGS). We describe a drug resistant LGS patient with daily seizures and a left parietal dysembryoplastic neuroepithelial tumour. Pre-surgical evaluation showed, in addition to diffuse paroxysmal EEG discharges associated with atonic and tonic axial seizures, lateralizing EEG and clinical signs pointing to left hemisphere origin of the seizures. The patient was treated with lesionectomy and after 12 months of follow-up is still seizure free. This case suggests that in patients with LGS and focal lesions the possibility of correct identification of the epileptogenic zone using anatomo-electro-clinical correlations may be the key element for 'curative' surgery.