Epilepsy, cognition, and behavior: The clinical picture

Altered Rolandic gamma-band activation associated with motor impairment and ictal network desynchronization in childhood epilepsy

Epilepsy is associated with an abnormal expression of neural oscillations and their synchronization across brain regions. Oscillatory brain activation and synchronization also play an important role in cognition, perception and motor control. Childhood epilepsy is associated with a variety of cognitive and motor deficits, but the relationship between altered functional brain responses in various frequency ranges and functional impairment in these children remains poorly understood. We investigated functional magnetoencephalographic (MEG) responses from motor cortex in multiple functionally relevant frequency bands following median nerve stimulation in twelve children with epilepsy, including four children with motor impairments. We demonstrated that children with motor impairments exhibit an excessive gamma-band response from Rolandic cortex, and that the magnitude of this Rolandic gamma response is negatively associated with motor function. Abnormal responses from motor cortex were also associated with ictal desynchronization of oscillations within Rolandic cortex measured using intracranial EEG (iEEG). These results provide the evidence that ictal disruption of motor networks is associated with an altered functional response from motor cortex, which is in turn associated with motor impairment.

Epilepsy in four genetically determined syndromes of intellectual disability

BACKGROUND

Epilepsy occurs with increased frequency in people with an intellectual disability (ID) compared to the rest of the population. A variety of research has in recent years shed light on genetic and biochemical aetiologies of epilepsy and, often in a different literature, on syndromes of ID. The aims of this annotation are to review developments in understanding of the pathophysiology of several ID syndromes in which epilepsy is a frequent co-occurrence and to relate these observations to recent advances in understanding of how these pathophysiological disturbances may lead to epilepsy.

METHOD

The ID syndromes selected for review were fragile X (FXS), Rett (RTT) and Angelman syndromes (AS) and tuberous sclerosis complex (TSC). Epilepsy is a significant aspect of these syndromes and relevant research into the genetic and biochemical pathophysiology of these four ID syndromes may be informative in establishing the association between epilepsy and ID. Employing a structured approach the authors initially searched the PubMed database for large case series describing the characteristics of epilepsy as manifested in these ID syndromes. The criteria for inclusion of the case series in the review were a sample size of greater than 50 and the description of several of the characteristic features of epilepsy, namely prevalence of seizures, age of seizure onset, seizure frequency, seizure semiology, severity and treatment. Following this, studies of the genetic and biochemical pathophysiology of these four ID syndromes were reviewed and the potential relevance of this research in understanding the association with epilepsy highlighted. Findings were considered in a focused manner in terms of effects on excitatory and inhibitory neurotransmitter systems and on glial function.

RESULTS

Diverse genetic pathologies underlying several ID syndromes can lead to alterations in the functioning of the glutamatergic and GABAergic neurotransmitter systems. The mechanisms involved include transcriptional regulation in RTT, translational regulation in FXS and TSC, and UBE3A-mediated proteolysis in AS. Expression or functioning of receptor subunits, uptake sites and enzymes involved in neurotransmitter metabolism are often affected by these changes, and may lead to modifications in network excitability and neuronal plasticity that may contribute to epileptogenesis and ID. Dysfunction in astrocytes may also contribute to epileptogenesis and ID in FXS, RTT and TSC with potential mechanisms including failure of astrocytic support functions, glial inflammation and homeostatic disturbances that affect the excitability and architecture of neuronal networks.

CONCLUSIONS

The annotation highlights research describing disturbances in excitatory and inhibitory neurotransmitter systems, neuronal ion channel and glial functions that provide possible explanations for the co-occurrence of seizures within several ID syndromes, in some cases suggesting possible avenues for research into novel therapeutic targets. Phenotypic overlaps between syndromes may also relate to roles for the implicated genes in different disturbances in linked biochemical pathways.

Age-dependent decline in learning and memory performances of WAG/Rij rat model of absence epilepsy

Recent clinical studies revealed emotional and cognitive impairments associated with absence epilepsy. Preclinical research with genetic models of absence epilepsy however have primarily focused on dysfunctional emotional processes and paid relatively less attention to cognitive impairment. In order to bridge this gap, we investigated age-dependent changes in learning and memory performance, anxiety-like behavior, and locomotor activity of WAG/Rij rats (a valid model of generalized absence epilepsy) using passive avoidance, Morris water maze, elevated plus maze, and locomotor activity cage. We tested 5 month-old and 13 month-old WAG/Rij rats and compared their performance to age-matched Wistar rats. Results revealed a decline in emotional and spatial memory of WAG/Rij rats compared to age-matched Wistar rats only at 13 months of age. Importantly, there were no significant differences between WAG/Rij and Wistar rats in terms of anxiety-like behavior and locomotor activity at either age. Results pointed at age-dependent learning and memory deficits in the WAG/Rij rat model of absence epilepsy.

Developmental outcomes of childhood-onset temporal lobe epilepsy: a community-based study

PURPOSE

To assess the impact of childhood-onset temporal lobe epilepsy (TLE) on the attainment of normative developmental tasks and identify predictors of long-term developmental outcomes.

METHODS

In 1992-1993, a prospective longitudinal cohort study of childhood-onset TLE was commenced in the State of Victoria, Australia. At review in 2004-2006, we assessed developmental tasks, which are age-specific individual psychosocial achievements tied to particular phases of the lifespan. The cohort comprised 54 individuals (33 female) with a mean age of 20 years (range 12-29), and mean age at TLE onset of 6 years (range 0.2-15).

KEY FINDINGS

Individuals were clustered into three groups representing distinct developmental trajectories: (1) a Normal group (52%) who achieved most of their developmental tasks, (2) an Altered group (37%) who achieved some, and (3) a Delayed group (11%) who achieved few. The groups showed significant cognitive differences, with the Normal group outperforming the Altered and Delayed groups on a range of measures (p < 0.05). Multiple discriminant function analysis indicated that membership of the groups was independently predicted by the chronicity of seizures, cognitive functioning, having surgically remediable epilepsy, and gender (p < 0.001). Seizure chronicity and cognition discriminated between all three trajectories, while surgical intervention and gender primarily discriminated between the Altered and Delayed trajectories.

SIGNIFICANCE

Childhood-onset TLE can disrupt achievement of normative developmental tasks that is independently predicted by medical, biologic, and cognitive factors. Assessment of developmental tasks across the lifespan provides a practical framework for guiding prognostic counseling of patients and families.

Social competence in children with epilepsy--a review

This systematic review focuses on definitions of social competence and assessment methods and provides an overview of the main findings in childhood epilepsy. A total of 45 studies drawn from MEDLINE and PsycINFO (1998-2010) and their reference lists met the selection criteria. Social competence was not defined in the studies reviewed. The study samples varied and consisted mostly of school-aged children. The majority of the studies focused on social adjustment and addressed problems in this area. Little is known about other aspects of social competence, namely social skills or social performance. A broader perspective on and definition of the assessment of social competence in children with epilepsy are proposed. More studies of the abilities underlying social competence, such as social and socio-cognitive skills, are needed in order to gain insight into the developmental pathways of social competence and protective factors for later development.

Molecular bases and clinical spectrum of early infantile epileptic encephalopathies

Epilepsy can be a challenging diagnosis to make in the neonatal and infantile periods. Seizures in this age group may be due to a serious underlying cause that results in an epileptic encephalopathy. Early infantile epileptic encephalopathy (EIEE) is a progressive neurologic condition that exhibits concomitant cognitive and motor impairment, and is often associated with severe intellectual disability. This condition belongs to the group of age-dependent epileptic encephalopathies, and thus the clinical and electro-encephalographic features change with age as the central nervous system evolves. The molecular bases and the clinical spectrum associated with the early infantile epileptic encephalopathies continue to expand as new genetic discoveries are made. This review will highlight the molecular etiologies of early infantile epileptic encephalopathy, and the clinical and electro-encephalographic changes that take place in these epileptic phenotypes as the brain develops.

Epilepsy and autism: is there a special relationship?

Increasingly, there has been an interest in the association between epilepsy and autism. The high frequency of autism in some of the early-onset developmental encephalopathic epilepsies is frequently cited as evidence of the relationship between autism and epilepsy. While these specific forms of epilepsy carry a higher-than-expected risk of autism, most, if not all, of the association may be due to intellectual disability (ID). The high prevalence of interictal EEG discharges in children with autism is also cited as further evidence although errors in the diagnosis of epilepsy seem to account for at least part of those findings. The prevalence of ID is substantially elevated in children with either epilepsy or autism. In the absence of ID, there is little evidence of a substantial, if any, increased risk of autism in children with epilepsy. Further, although the reported prevalence of autism has increased over the last several years, much of this increase may be attributable to changes in diagnostic practices, conceptualization of autism in the presence of ID, and laws requiring provision of services for children with autism. In the context of these temporal trends, any further efforts to tease apart the relationships between epilepsy, ID, and autism will have to address head-on the accuracy of diagnosis of all three conditions before we can determine whether there is, indeed, a special relationship between autism and epilepsy.

Hypoxia-induced neonatal seizures diminish silent synapses and long-term potentiation in hippocampal CA1 neurons

Neonatal seizures can lead to epilepsy and long-term cognitive deficits into adulthood. Using a rodent model of the most common form of human neonatal seizures, hypoxia-induced seizures (HS), we aimed to determine whether these seizures modify long-term potentiation (LTP) and silent NMDAR-only synapses in hippocampal CA1. At 48-72 h after HS, electrophysiology and immunofluorescent confocal microscopy revealed a significant decrease in the incidence of silent synapses, and an increase in AMPARs at the synapses. Coincident with this decrease in silent synapses, there was an attenuation of LTP elicited by either tetanic stimulation of Schaffer collaterals or a pairing protocol, and persistent attenuation of LTP in slices removed in later adulthood after P10 HS. Furthermore, postseizure treatment in vivo with the AMPAR antagonist 2,3-dihydroxy-6-nitro-7-sulfonyl-benzo[f]quinoxaline (NBQX) protected against the HS-induced depletion of silent synapses and preserved LTP. Thus, this study demonstrates a novel mechanism by which early life seizures could impair synaptic plasticity, suggesting a potential target for therapeutic strategies to prevent long-term cognitive deficits.

Cognitive and adaptive development of patients with tuberous sclerosis complex: a retrospective, longitudinal investigation

OBJECTIVE

The aim of the work described here was to systematically analyze the developmental trajectory of patients with tuberous sclerosis complex (TSC).

METHODS

A retrospective longitudinal chart review was performed, selecting patients who received multiple neuropsychological assessments. Intellectual/Developmental Quotients, Adaptive Behavior Composite scores, and clinical data were collected. On available EEGs, interictal epileptiform discharges were counted.

RESULTS

Sixty-six (18%) patients with TSC received multiple cognitive and adaptive development assessments. The mean intelligence of this study group remained relatively stable, albeit variable. Significant decline in adaptive functioning was observed, associated with lower age at seizure onset. Patients who underwent neurosurgery prior to baseline testing showed cognitive improvement. Developmental declines were significantly associated with increased numbers of antiepileptic drugs, with a trend toward association with mutation type and interictal epileptiform discharges.

CONCLUSION

This study suggests that the developmental course of patients with TSC may be altered by epilepsy comorbidity and neurosurgery, underlining the need for early and effective interventions in this population.

Behavioral problems in children with epilepsy in rural Kenya

The aims of this study were to record behavioral problems in children with epilepsy (CWE), compare the prevalence with that reported among healthy children without epilepsy, and investigate the risk factors. A child behavioral questionnaire for parents comprising 15 items was administered to the main caregiver of 108 CWE and 108 controls matched for age in Kilifi, Kenya. CWE had a higher mean score for reported behavioral problems than controls (6.9 vs 4.9, t=4.7, P<0.001). CWE with active epilepsy also recorded more behavioral problems than those with inactive epilepsy (8.2 vs 6.2, t=-2.9, P=0.005). A significantly greater proportion of CWE (49% vs 26% of controls) were reported to have behavioral problems. Active epilepsy, cognitive impairment, and focal seizures were the most significant independent covariates of behavioral problems. Behavioral problems in African CWE are common and need to be taken into consideration in planning comprehensive clinical services in this region.

Migraine- and dystonia-related disease-mutations of Na+/K+-ATPases: relevance of behavioral studies in mice to disease symptoms and neurological manifestations in humans

The two autosomal dominantly inherited neurological diseases: familial hemiplegic migraine type 2 (FHM2) and familial rapid-onset of dystonia-parkinsonism (Familial RDP) are caused by in vivo mutations of specific alpha subunits of the sodium-potassium pump (Na(+)/K(+)-ATPase). Intriguingly, patients with classical FHM2 and RDP symptoms additionally suffer from other manifestations, such as epilepsy/seizures and developmental disabilities. Recent studies of FHM2 and RDP mouse models provide valuable tools for dissecting the vital roles of the Na(+)/K(+)-ATPases, and we discuss their relevance to the complex patient symptoms and manifestations. Thus, it is interesting that mouse models targeting a specific α-isoform cause different, although still comparable, phenotypes consistent with classical symptoms and other manifestations observed in FHM2 and RDP patients. This review highlights that use of mouse models have broad potentials for future research concerning migraine and dystonia-related diseases, which will contribute towards understanding the, yet unknown, pathophysiologies.

Seizures in early life suppress hippocampal dendrite growth while impairing spatial learning

Impaired learning and memory are common in epilepsy syndromes of childhood. Clinical investigations suggest that the developing brain may be particularly vulnerable to the effects of intractable seizure disorders. Magnetic resonance imaging (MRI) studies have demonstrated reduced volumes in brain regions involved in learning and memory. The earlier the onset of an epilepsy the larger the effects seem to be on both brain anatomy and cognition. Thus, childhood epilepsy has been proposed to interfere in some unknown way with brain development. Experiments reported here explore these ideas by examining the effects of seizures in infant mice on learning and memory and on the growth of CA1 hippocampal pyramidal cell dendrites. Fifteen brief seizures were induced by flurothyl between postnatal days 7 and 11 in mice that express green fluorescent protein (GFP) in hippocampal pyramidal cells. One to 44days later, dendritic arbors were reconstructed to measure growth. Spatial learning and memory were also assessed in a water maze. Our results show that recurrent seizures produced marked deficits in learning and memory. Seizures also dramatically slowed the growth of basilar dendrites while neurons in littermate control mice continued to add new dendritic branches and lengthen existing branches. When experiments were performed in older mice, seizures had no measureable effects on either dendrite arbor complexity or spatial learning and memory. Our results suggest that the recurring seizures of intractable childhood epilepsy contribute to associated learning and memory deficits by suppressing dendrite growth.

Health perception and socioeconomic status following childhood-onset epilepsy: the Dutch study of epilepsy in childhood

PURPOSE

Epilepsy may have far-reaching consequences for patients, other than having seizures and medication. At 15 years after diagnosis, this study investigates health perception, restrictions due to epilepsy, living arrangements (including marital status and offspring), and the educational and occupational attainment of patients with childhood-onset epilepsy.

METHODS

A total of 453 patients with epilepsy had a 5-year follow-up since diagnosis with regular visits and data collection. Ten years later, a questionnaire addressing epilepsy was completed by 413 patients, resulting in a mean follow-up of 15 years. Subjects were compared with age peers of the Dutch population for each etiologic group separately, and also for subjects with/without a 5-year terminal remission regardless of treatment. Age-adjusted standardized incidence rates were calculated for each variable.

KEY FINDINGS

Subjects with normal intelligence had a health perception comparable with that of the general population, but significantly more subjects without remission had a worse health perception, especially those still using medication. Restrictions and symptoms due to epilepsy were reported by 14% of the subjects, mainly by those without remission or with ongoing medication. The living arrangement of subjects with idiopathic or cryptogenic etiology was similar to that of Dutch persons of the same age (age peers). Subjects with remote symptomatic etiology less often lived independently or with a partner, and more frequently resided in an institution or living group for the disabled. Those with and without remission were more often part of another household, mainly due (in both groups) to having a remote symptomatic etiology. Rates of having a partner and offspring were significantly reduced only for subjects with remote symptomatic etiology. Fewer students with idiopathic/remote symptomatic etiology and students in remission followed higher vocational or scientific education. In these latter groups, the highest attained education of employees was lower than expected. The employment status of subjects with idiopathic or cryptogenic etiology was comparable with that of their Dutch age peers, but fewer subjects with remote symptomatic etiology were employed and more of them were part of the dependent population. However, for those in the labor force (employed/unemployed) all employment rates were ≥90%, even for those with remote symptomatic etiology. Nevertheless, fewer employees than expected had a higher vocational or scientific level of occupation, even those with idiopathic etiology and those in remission.

SIGNIFICANCE

Health perception, living arrangement, and socioeconomic status were influenced by epilepsy, comorbidities, or treatment, particularly for subjects with remote symptomatic etiology or no remission. The group in remission fared less well than expected, mainly due to the numbers of subjects with remote symptomatic etiology in this group. In line with others, we conclude that childhood-onset epilepsy is associated with lower educational attainment, even for subjects with idiopathic etiology and subjects in remission; probably related to this, their occupational level was also lower than expected.