Impaired spatial working memory in children with well-controlled epilepsy: an event-related potentials study

Scalp Electroencephalogram-Derived Involvement Indexes during a Working Memory Task Performed by Patients with Epilepsy

Electroencephalography (EEG) wearable devices are particularly suitable for monitoring a subject's engagement while performing daily cognitive tasks. EEG information provided by wearable devices varies with the location of the electrodes, the suitable location of which can be obtained using standard multi-channel EEG recorders. Cognitive engagement can be assessed during working memory (WM) tasks, testing the mental ability to process information over a short period of time. WM could be impaired in patients with epilepsy. This study aims to evaluate the cognitive engagement of nine patients with epilepsy, coming from a public dataset by Boran et al., during a verbal WM task and to identify the most suitable location of the electrodes for this purpose. Cognitive engagement was evaluated by computing 37 engagement indexes based on the ratio of two or more EEG rhythms assessed by their spectral power. Results show that involvement index trends follow changes in cognitive engagement elicited by the WM task, and, overall, most changes appear most pronounced in the frontal regions, as observed in healthy subjects. Therefore, involvement indexes can reflect cognitive status changes, and frontal regions seem to be the ones to focus on when designing a wearable mental involvement monitoring EEG system, both in physiological and epileptic conditions.

Limited Ability to Adjust N2 Amplitude During Dual Task Walking in People With Drug-Resistant Juvenile Myoclonic Epilepsy

Juvenile myoclonic epilepsy (JME) is one of the most common epileptic syndromes; it is estimated to affect 1 in 1,000 people worldwide. Most people with JME respond well to medication, but up to 30% of them are drug-resistant. To date, there are no biomarkers for drug resistance in JME, and the poor response to medications is identified in retrospect. People with JME have frontal dysfunction manifested as impaired attention and difficulties in inhibiting habitual responses and these dysfunctions are more pronounced in drug-resistant individuals. Frontal networks play an important role in walking and therefore, gait can be used to overload the neural system and expose subtle changes between people with drug-responsive and drug-resistant JME. Electroencephalogram (EEG) is a promising tool to explore neural changes during real-time functions that combine a cognitive task while walking (dual tasking, DT). This exploratory study aimed to examine the alteration in electrical brain activity during DT in people with drug-responsive and drug-resistant JME. A total of 32 subjects (14 males and 18 females) participated: 11 drug-responsive (ages: 31.50 ± 1.50) and 8 drug-resistant (27.27 ± 2.30) people with JME, and 13 healthy controls (29.46 ± 0.69). The participants underwent EEG examination during the performance of the visual Go/NoGo (vGNG) task while sitting and while walking on a treadmill. We measured latencies and amplitudes of N2 and P3 event-related potentials, and the cognitive performance was assessed by accuracy rate and response time of Go/NoGo events. The results demonstrated that healthy controls had earlier N2 and P3 latencies than both JME groups (N2: p = 0.034 and P3: p = 0.011), however, a limited ability to adjust the N2 amplitude during walking was noticeable in the drug-resistant compared to drug-responsive. The two JME groups had lower success rates (drug-responsive p < 0.001, drug-resistant p = 0.004) than healthy controls, but the drug-resistant showed longer reaction times compared to both healthy controls (p = 0.033) and drug-responsive (p = 0.013). This study provides the first evidence that people with drug-resistant JME have changes in brain activity during highly demanding tasks that combine cognitive and motor functions compared to people with drug-responsive JME. Further research is needed to determine whether these alterations can be used as biomarkers to drug response in JME.

Perampanel and Visuospatial Skills in Children With Epilepsy

Introduction: Perampanel (PER) is a non-competitive AMPA glutamate receptor antagonist approved for focal and generalized seizures as add-on therapy. PER does not seem to negatively affect the cognitive profile in children and adolescents, but its influence on visuospatial abilities is still to be assessed. The aim of our study was to assess visuospatial skills through a standardized neuropsychological evaluation in adolescents taking PER for 12 months.

Methods: Our sample included 46 adolescents aged 12–18 years with focal and generalized drug-resistant epilepsy already in therapy with one or two antiseizure medications. Changes in visuospatial perception and memory were assessed by the Rey–Osterrieth Complex Figure Test at baseline (before taking PER) and after 12 months of pharmacological treatment. Executive functions and non-verbal intelligence were also assessed at baseline.

Results: After 12 months of PER therapy, the mean scores on the Rey–Osterrieth Complex Figure Test remained almost unchanged for both visuospatial perception and visuospatial memory skills. At baseline, visuospatial memory was related to executive function, and visuospatial perception was related to executive function and non-verbal intelligence.

Conclusions: Adjunctive treatment with PER did not negatively affect visuospatial skills. No adverse event effects have been reported after 12 months of follow-up, and this suggests a good tolerability in the middle-to-long term.

Effects of antiseizure monotherapy on visuospatial memory in pediatric age

INTRODUCTION

Visuospatial abilities are fundamental for good school achievements and good daily functioning. Previous studies showed an impairment of visuospatial skills in pediatric patients with epilepsy; pharmacological treatment, although indispensable for the seizure control, could further affect cognitive functions. The aim of our study was to evaluate the visuospatial skills in children and adolescents with different forms of epilepsy well-controlled by antiseizure monotherapy, both at baseline and after one year follow-up, through a standardized neuropsychological assessment.

METHODS

We recruited 207 children and adolescents (mean age = 10.35 ± 2.39 years) with epilepsy, well controlled by monotherapy with levetiracetam, valproic acid, ethosuximide, oxcarbazepine or carbamazepine and 45 age/sex-matched controls. All the participants performed the Rey-Osterrieth Complex Figure, a standardized test for visuospatial perception and visuospatial memory assessment, at baseline and after 12 month of drug therapy. Age, sex, executive functions, non-verbal intelligence, age at onset of epilepsy, epilepsy duration, epilepsy type, lobe and side of seizure onset were considered in our analysis. EEG, seizure frequency, and drug dose were also recorded.

RESULTS

At baseline, the epilepsy group performed significantly worse than controls in the Immediate Recall test but not the Direct Copy test, without differences between epilepsy subgroups. Immediate Recall scores were related to age of seizure onset and epilepsy duration and executive functions. The re-assessment after 1 year showed that the Immediate Recall mean scores were not significantly changed in the levetiracetam and oxcarbazepine group, while they significantly worsened in the valproic acid, ethosuximide and carbamazepine groups. The Immediate Recall scores were correlated to age, age at onset of epilepsy, epilepsy duration, and executive functions.

CONCLUSIONS

Children with epilepsy may exhibit visuospatial memory impairment compared to their peer, that may be correlated to some features of the epilepsy itself and to the impairment of executive functions. Different antiseizure medications can affect visuospatial memory differently, so it is important monitoring this aspect in pediatric patients.

The Oscillatory Basis of Working Memory Function and Dysfunction in Epilepsy

Working memory (WM) deficits are pervasive co-morbidities of epilepsy. Although the pathophysiological mechanisms underpinning these impairments remain elusive, it is thought that WM depends on oscillatory interactions within and between nodes of large-scale functional networks. These include the hippocampus and default mode network as well as the prefrontal cortex and frontoparietal central executive network. Here, we review the functional roles of neural oscillations in subserving WM and the putative mechanisms by which epilepsy disrupts normative activity, leading to aberrant oscillatory signatures. We highlight the particular role of interictal epileptic activity, including interictal epileptiform discharges and high frequency oscillations (HFOs) in WM deficits. We also discuss the translational opportunities presented by greater understanding of the oscillatory basis of WM function and dysfunction in epilepsy, including potential targets for neuromodulation.

Quantitative EEG biomarkers for epilepsy and their relation to chemical biomarkers

The electroencephalogram (EEG) is the most important method to diagnose epilepsy. In clinical settings, it is evaluated by experts who identify patterns visually. Quantitative EEG is the application of digital signal processing to clinical recordings in order to automatize diagnostic procedures, and to make patterns visible that are hidden to the human eye. The EEG is related to chemical biomarkers, as electrical activity is based on chemical signals. The most well-known chemical biomarkers are blood laboratory tests to identify seizures after they have happened. However, research on chemical biomarkers is much less extensive than research on quantitative EEG, and combined studies are rarely published, but highly warranted. Quantitative EEG is as old as the EEG itself, but still, the methods are not yet standard in clinical practice. The most evident application is an automation of manual work, but also a quantitative description and localization of interictal epileptiform events as well as seizures can reveal important hints for diagnosis and contribute to presurgical evaluation. In addition, the assessment of network characteristics and entropy measures were found to reveal important insights into epileptic brain activity. Application scenarios of quantitative EEG in epilepsy include seizure prediction, pharmaco-EEG, treatment monitoring, evaluation of cognition, and neurofeedback. The main challenges to quantitative EEG are poor reliability and poor generalizability of measures, as well as the need for individualization of procedures. A main hindrance for quantitative EEG to enter clinical routine is also that training is not yet part of standard curricula for clinical neurophysiologists.

P300 development from infancy to adolescence

This article provides an overview of P300 research from infancy through adolescence. First, a brief historical overview is provided highlighting seminal studies that began exploration of the P300 component in developmental groups. Overall, these studies suggest that the P300 can be detected in children and appears to reflect similar cognitive processes to those in adults; however, it is significantly delayed in its latency to peak. Second, two striking findings from developmental research are the lack of a clear P300 component in infancy and differential electrophysiological responses to novel, unexpected stimuli in children, adolescents, and adults. Third, contemporary questions are described, which include P300-like components in infancy, alteration of P300 in atypically developing groups, relations between P300 and behavior, individual differences of P300, and neural substrates of P300 across development. Finally, we conclude with comments regarding the power of a developmental perspective and suggestions for important issues that should be addressed in the next 50 years of P300 research.

Brain responses to auditory oddball task in children with benign childhood epilepsy with centrotemporal spikes: Quantitative analysis and correlation with neuropsychological assessment scores

OBJECTIVE

Variable degrees of cognitive dysfunction have been reported in children with benign childhood epilepsy with centrotemporal spikes (BCECTS). Our aim was to perform quantitative analyses of the brain responses to cognitive tasks using event-related desynchronization (ERD) and event-related synchronization (ERS) and correlating the results with the scores of neuropsychological tests in patients with BCECTS.

METHODS

This case control study included 30 patients with BCECTS and 20 controls. Clinical assessment, neuropsychological tests, the Positive wave at 300 msec (P300) parameters recording, and quantitative electroencephalography (EEG) analysis were carried out for both groups. Alpha power ERD and ERS were measured in six different brain regions during an auditory oddball paradigm.

RESULTS

Children with epilepsy showed a statistically significant poorer performance in verbal intelligence quotient (IQ), performance IQ, and total scale IQ and lower number of correct responses. Moreover, both groups showed diffuse alpha power attenuation in response to the target tones. After summation of the alpha power ERD over all brain regions to get the net diffuse ERD, the patients' group showed a statistically significant smaller net alpha ERD compared with that of the control group (P=0.001). No significant correlations between the alpha ERD percentage, recorded P300 parameters, and neuropsychological tests scores were found.

CONCLUSIONS

Children with BCECTS have subtle cognitive dysfunction proved by significantly lower scores of verbal IQ and performance IQ subtests. The significantly smaller net diffuse alpha power ERD detected in children with epilepsy may be an electrophysiological indicator of disruptive brain activation in relation to cognitive attentional tasks; however, its correlation with neuropsychological tests was insignificant.

Maintenance effects of working memory intervention (Cogmed) in children with symptomatic epilepsy

PURPOSE

To extend previous research documenting the benefits of working memory (WM) intervention (Cogmed) immediately post-intervention in children with epilepsy by assessing the 3-month maintenance effects.

METHODS

Participants involved in a previous randomized clinical trial (RCT) were invited to participate if they completed Cogmed within the last 3months (n=15) and additional participants (n=13) were prospectively recruited. Standardized assessments of near-transfer effects (i.e., visual and auditory attention and WM) were completed prior to and immediately after intervention and at 3-month follow-up. An additional measure assessing the far-transfer effect of fluid reasoning was administered prior to intervention and at 3-month follow-up.

RESULTS

Participants exhibited gains in auditory and visual attention and WM immediately following intervention and gains were generally sustained at 3-month follow-up. Intervention did not improve visual-verbal WM or fluid reasoning. The clinical variables studied (i.e., age of seizure onset, seizure frequency, epilepsy duration, and overall intellectual functioning) did not elucidate reliable relationships with intervention.

CONCLUSIONS

Working memory training is possibly efficacious in improving related skills which are maintained for 3months in children with active epilepsy. No transfer to fluid reasoning was documented. Further investigation by means of a large-scale RCT which includes a placebo and both objective and subjective measures of the impact of training on daily functioning is warranted.

Children with well controlled epilepsy possess different spatio-temporal patterns of causal network connectivity during a visual working memory task

Using spectral Granger causality (GC) we identified distinct spatio-temporal causal connectivity (CC) patterns in groups of control and epileptic children during the execution of a one-back matching visual discrimination working memory task. Differences between control and epileptic groups were determined for both GO and NOGO conditions. The analysis was performed on a set of 19-channel EEG cortical activity signals. We show that for the GO task, the highest brain activity in terms of the density of the CC networks is observed in α band for the control group while for the epileptic group the CC network seems disrupted as reflected by the small number of connections. For the NOGO task, the denser CC network was observed in θ band for the control group while widespread differences between the control and the epileptic group were located bilaterally at the left temporal-midline and parietal areas. In order to test the discriminative power of our analysis, we performed a pattern analysis approach based on fuzzy classification techniques. The performance of the classification scheme was evaluated using permutation tests. The analysis demonstrated that, on average, 87.6 % of the subjects were correctly classified in control and epileptic. Thus, our findings may provide a helpful insight on the mechanisms pertaining to the cognitive response of children with well controlled epilepsy and could potentially serve as "functional" biomarkers for early diagnosis.

Memory in children with epilepsy: a systematic review

PURPOSE

Research suggests an increased risk for cognitive impairment in childhood epilepsy with memory being one area of cognition most likely to be affected. Understanding the prevalence and predictors of memory difficulties may help improve awareness of the difficulties and allow efficacious supports to be put in place.

METHOD

A systematic review was carried out using the search terms 'memory', 'children' and 'epilepsy' in the database PUBMED. Eighty-eight studies met inclusion criteria. The review focuses on comparisons of memory scores of children with epilepsy and controls, and comparison of memory scores of children with epilepsy to normative scores. Predictors of memory impairment and the effect of surgery on memory functioning are also reviewed.

RESULTS

The majority (78%) of studies reviewed revealed that children with epilepsy scored lower than controls and normative scores on measures of memory. Post-surgery, memory scores were reported to improve in 50% of studies. Predictors of memory impairment included a greater number of AEDs used, younger age of onset, increased seizure frequency and longer duration of epilepsy.

CONCLUSION

Children with epilepsy have a high frequency of memory impairments. However, the exact prevalence of difficulties is not clear due to the lack of population-based data. Most studies have not controlled for IQ and thus it is unclear if difficulties are always related to global cognitive difficulties. There is need for future population-based studies and studies focussing on the neurobiology of memory problems in children with epilepsy.

Atypical face processing in children with tuberous sclerosis complex

There is a high incidence of autism in tuberous sclerosis complex. Given the evidence of impaired face processing in autism, the authors sought to investigate electrophysiological markers of face processing in children with tuberous sclerosis complex. The authors studied 19 children with tuberous sclerosis complex under age 4, and 20 age-matched controls, using a familiar-unfamiliar faces paradigm. Of the children, 6 with tuberous sclerosis complex (32%) had autism. Children with tuberous sclerosis complex showed a longer N290 latency than controls (276 ms vs 259 ms, P = .05) and also failed to show the expected hemispheric differences in face processing. The longest N290 latency was seen in (1) children with autism and tuberous sclerosis complex and (2) children with temporal lobe tubers. This study is the first to quantify atypical face processing in children with tuberous sclerosis complex. This functional impairment may provide insight into a mechanism underlying a pathway to autism in tuberous sclerosis complex.

Within-subject variability during spatial working memory in children with ADHD: an event-related potentials study

Working memory (WM) dysfunction and increased within-subject variability are known issues in attention deficit/hyperactivity disorder (ADHD) patients. Little is known about the electrophysiological characteristics of this variability. We evaluated behavioral and electrophysiological within-subject variability taking developmental aspects into account in a group of ADHD patients. Multichannel (n = 31) event-related potentials (ERP) were measured during a visuo-spatial backmatching task; 44 children (8-16 years old) were tested: 22 children with ADHD, combined (n = 17) and inattentive (n = 5) type, and 22 age- and intelligence-matched control children. One-backmatching (BM1) and two-backmatching (BM2) tasks were performed. Classical behavioral parameters and target and nontarget ERP were compared between groups. In addition, motor response variability and ERP amplitude variability were studied. Age-related changes in both motor response and ERP amplitude variability were analyzed in each group. Attention deficit/hyperactivity disorder children made more commission errors, which was more pronounced in the difficult (BM2) task. No difference between groups was found in ERP amplitude and in motor response variability. However, ADHD patients had higher ERP amplitude variability, which was again more pronounced in the difficult WM task. A delayed maturation of amplitude variability was seen in ADHD patients with a slower than in controls decrease in variability with age. This amplitude variability was correlated with the number of commissions, but in an opposite way for ADHD and control children. Our findings indicate an impaired visuo-spatial WM processing in ADHD children with greater ERP amplitude variability compared to controls. Our results also support the view of a delayed cortical development of visuo-spatial WM circuits in this disorder.

Posterior resection for childhood lesional epilepsy: neuropsychological evolution

The aim of this study was to provide information on the neuropsychological evolution of children with symptomatic epilepsy who have undergone surgical resection of posterior (occipitoparietal) lesions. Twelve children with epilepsy with parietal and/or occipital lesions were enrolled in the study and followed after surgical resection: full clinical and epileptic examinations were performed before and after surgery, as was a neuropsychological study of both general and specific cognitive abilities. Epilepsy evolution was generally good (Engel classification IA in nine cases) with persistent selective neurological impairments (eye field defects, sensory unilateral spatial neglect) in some cases, consistent with the lesion site. Neuropsychological defects before surgery in the absence of refractory epilepsy were minimal with a normal global cognitive competence; yet, the relatively low performance scores with some impairment of specific cognitive skills were strictly correlated with defects in visual perceptive skills in both right- and left-sided lesions. Surgery seems to have improved performance abilities, whereas other abnormal specific skills did not change with the exception of working memory that in some cases was defective before surgery and normalized after lesion removal. Our study in this particular cohort of children with epileptogenic occipitoparietal lesions thus confirmed a trend toward a benign epileptic and neurodevelopmental outcome after surgical resection of the lesion.