Do seizures cause irreversible cognitive damage? Evidence from animal studies

Pergularia daemia hydro-ethanolic extract protects against pentylenetetrazole kindling-induced seizures, oxidative stress, and neuroinflammation in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Current antiepileptic drugs fail to control approximately 30% of epilepsies. Therefore, there is a need to develop more effective antiepileptic drugs, and medicinal plants provide an attractive source for new compounds. Pergularia daemia (Asclepiadaceae) is used in Cameroon traditional medicine to treat stroke, anemia, inflammation, and epilepsy. Recently, traditional healers claim that an hydro-ethanolic extract of the roots of P. daemia is more effective than an aqueous extract on refractory seizures.

AIM OF THE STUDY

The antiepileptic effect of P. daemia hydro-ethanolic extract was investigated on the pentylenetetrazole kindling model of temporal lobe epilepsy in mice and possible mechanisms of action.

MATERIALS AND METHODS

Mice were divided into 8 groups treated as follows: normal group received distilled water (10 ml/kg, p.o.), control group received distilled water (10 ml/kg, p.o.), ethanol group received ethanol (5%, p.o.), positive control received sodium valproate (300 mg/kg, p.o.), and test groups received P. daemia hydro-ethanolic (HE) extract (1.6, 4, 8 and 16 mg/kg, p.o.). All groups were kindled by 11 injections of pentylenetetrazole (PTZ) (35 mg/kg, i.p.), once every alternate day (48 ± 2 h), until the development of kindling, i.e., the occurrence of stage 5 seizures for two consecutive trials. One week later, i.e., 29^th day, mice were challenged with a single and lower dose of PTZ (25 mg/kg, i.p.) that does not induce seizures in normal mice but causes seizures in mice prone to seizures and behavioral alterations. After completion of the kindling procedure, Morris water maze, passive avoidance, and open field tests were performed. Afterward, animals were euthanized, and hippocampi were removed for the estimation of the levels of GABA-transaminase (GABA-T), L-glutamate decarboxylase (L-GAD), and γ-aminobutyric acid (GABA). Oxidative stress and neuroinflammation markers also were quantified. Finally, histological analysis of the hippocampus was carried out.

RESULTS

PTZ-kindling induced myoclonic jerks and generalized tonic-clonic seizures in control mice. However, the HE extract of P. daemia (4-16 mg/kg), compared to sodium valproate, significantly protected mice against myoclonic jerks and generalized tonic-clonic seizures. Also, the HE extract (1.6-16 mg/kg) significantly increased the seizure score. Furthermore, the HE extract of P. daemia significantly reduced seizure-induced cognitive impairments. PTZ-kindling induced significant alterations in GABA, GABA-T, and L-GAD contents as well as oxidative stress, and neuroinflammation, and the HE extract significantly reversed these effects, suggesting possible mechanisms. All these activities of the HE extract were confirmed by its protective effect against neuronal loss in the hippocampus.

CONCLUSIONS

The HE extract of P. daemia protected mice against kindled seizures and cognitive impairments, and these effects were greater than those of sodium valproate, a widely used antiepileptic drug. These effects may be mediated by neuromodulatory, anti-oxidant, and anti-inflammatory activities, thus suggesting a neuroprotective effect. These findings help to explain the beneficial use of these HE extracts of P.daemia in traditional medicine to treat epilepsy in Cameroon.

Pentylenetetrazol and Morphine Interaction in a State-dependent Memory Model: Role of CREB Signaling

Introduction:

State-dependent (STD) memory is a process, in which the learned information can be optimally retrieved only when the subject is in the state similar to the encoding phase. This phenomenon has been widely studied with morphine. Several studies have reported that Pentylenetetrazole (PTZ) impairs memory in experimental animal models. Due to certain mechanistic interactions between morphine and PTZ, it is hypothesized that PTZ may interfere with the morphine-STD. The cyclic adenosine monophosphate Response Element-Binding (CREB) is considered as the main downstream marker for long-term memory. This study was designed to determine the possible interaction between PTZ and morphine STD and the presumable changes in CREB mRNA.

Methods:

In an Inhibitory Avoidance (IA) model, posttraining morphine (2.5, 5, and 7.5 mg/ kg-i.p.) was used. The pre-test morphine was evaluated for morphine-induced STD memory. Moreover, the effect of a pre-test PTZ (60 mg/kg-i.p.) was studied along with morphine STD. Locomotion testing was carried out using open-field. Eventually, using real-time-PCR, the CREB mRNA changes in the hippocampus were evaluated.

Results:

Posttraining MOR (7.5 mg/kg-i.p.) impaired IA memory (P<0.001). The pre-test injection of similar doses of morphine recovered the morphine-induced memory impairment (P<0.001). The pre-test PTZ impaired the IA memory recall (P<0.001); however, the pre-test PTZ along with morphine STD potentiated the morphine-induced STD (P<0.001). Alterations in CREB mRNA were observed in all groups. No difference was seen in the locomotor activity.

Conclusion:

Presumably, the certain interactive effect of PTZ on morphine-induced STD is mediated through gamma-aminobutyric acid and opioid systems via CREB signaling.

Anxiety-like features and spatial memory problems as a consequence of hippocampal SV2A expression

The Synaptic Vesicle Protein 2A (SV2A) is a transmembrane protein whose presence is reduced both in animal models and in patients with chronic epilepsy. Besides its implication in the epileptic process, the behavioural consequences of the changes in its expression remain unclear. The purpose of our research is to better understand the possible role(s) of this protein through the phenotype of cKO (Grik4 Cre+/-, SV2A lox/lox) mice, male and female, which present a specific decrease of SV2A expression levels in the hippocampal glutamatergic neurons but without any epileptic seizures. In this study, we compare the cKO mice with cHZ (Grik4 Cre+/-, SV2A lox/+) and WT (Grik4 Cre+/+, SV2A lox/lox) mice through a battery of tests, used to evaluate different features: the anxiety-related features (Elevated Plus Maze), the locomotor activity (Activity Chambers), the contextual fear-related memory (Contextual Fear Conditioning), and the spatial memory (Barnes Maze). Our results showed statistically significant differences in the habituation to a new environment, an increase in the anxiety levels and spatial memory deficit in the cHZ and cKO groups, compared to the WT group. No statistically significant differences due to the genotype appeared in the spontaneous locomotor activity or the fear-linked memory. However, sexual differences were observed in this last feature. These results highlight not only an important role of the SV2A protein in the cognitive and anxiety problems typically encountered in epileptic patients, but also a possible role in the symptomatology of other neurodegenerative diseases, such as the Alzheimer’s disease.

The Free Radical Scavenger N-Tert-Butyl-α-Phenylnitrone (PBN) Administered to Immature Rats During Status Epilepticus Alters Neurogenesis and Has Variable Effects, Both Beneficial and Detrimental, on Long-Term Outcomes

Status epilepticus (SE), especially in immature animals, is known to produce recurrent spontaneous seizures and behavioral comorbidities later in life. The cause of these adverse long-term outcomes is unknown, but it has been hypothesized that free radicals produced by SE may play a role. We tested this hypothesis by treating immature (P25) rats with the free radical scavenger N-tert-butyl-α-phenylnitrone (PBN) at the time of lithium chloride (LiCl)/pilocarpine (PILO)-induced SE. Later, long-term outcomes were assessed. Cognitive impairment (spatial memory) was tested in the Morris water maze (MWM). Emotional disturbances were assessed by the capture test (aggressiveness) and elevated plus maze's (EPM) test (anxiety). Next, the presence and severity of spontaneous seizures were assessed by continuous video/EEG monitoring for 5 days. Finally, immunochemistry, stereology and morphology were used to assess the effects of PBN on hippocampal neuropathology and neurogenesis. PBN treatment modified the long-term effects of SE in varying ways, some beneficial and some detrimental. Beneficially, PBN protected against severe anatomical damage in the hippocampus and associated spatial memory impairment. Detrimentally, PBN treated animals had more severe seizures later in life. PBN also made animals more aggressive and more anxious. Correlating with these detrimental long-term outcomes, PBN significantly modified post-natal neurogenesis. Treated animals had significantly increased numbers of mature granule cells (GCs) ectopically located in the dentate hilus (DH). These results raise the possibility that abnormal neurogenesis may significantly contribute to the development of post-SE epilepsy and behavioral comorbidities.

Cognition and adaptive functioning in older people attending drug and alcohol services

BACKGROUND

Substance use disorders in older adults are expected to increase dramatically in the coming years. Given the increased susceptibility to cognitive deficits in older substance users (defined here as aged 50+ years due to the accelerated health decline observed in this population), it is important to consider the functional correlates of cognitive impairment in these older adults. This study details the cognitive status of older individuals attending outpatient drug and alcohol (D&A) treatment services and seeks to determine of the association of cognitive impairment to self-reported daily functioning.

METHODS

Ninety nine clients aged 50 years or over attending outpatient D&A treatment services in Sydney, Australia participated. Cognition was assessed using the Addenbrooke's Cognitive Examination - Revised (ACE-R). Recent substance use (Australian Treatment Outcome Profile), physical and mental health (SF12, Geriatric Depression Scale), social isolation (Lubben Social Network Scale), and activities of daily living (Bayer ADL Scale) were also assessed.

RESULTS

Nearly two-thirds of participants screened positive for cognitive impairment on the ACE-R; 41% and 65% of clients met the cut-off scores for mild cognitive impairment (MCI) and more severe cognitive impairment, respectively. Self-reported seizure history was a predictor of cognitive impairment.

CONCLUSIONS

The results suggest that cognitive impairment in this group is common. The assessment of cognitive status for this older group of patients should not only include the identification of cognitive impairment but also encompass mental health and social functioning. A greater understanding of the needs of this cohort will also enable better co-ordination with other health and welfare services tailored to this population.

Reduced thalamic volume in patients with Electrical Status Epilepticus in Sleep

PURPOSE

To test whether patients with Electrical Status Epilepticus in Sleep (ESES) and normal neuroimaging have a smaller thalamic volume than expected for age and for total brain volume.

METHODS

Case-control study comparing three groups of subjects of 4-14 years of age and normal magnetic resonance imaging: 1) ESES patients, 2) patients with refractory epilepsy control group, and 3) healthy controls. Thalamic and total brain volumes were calculated using an algorithm for automatic segmentation and parcellation of magnetic resonance imaging.

RESULTS

Eighteen ESES patients, 29 refractory epilepsy controls and 51 healthy controls were included. The median (p25-p75) age was 8.8 (7.5-10.3) years for ESES patients, 11 (7-12) years for healthy controls, and 9 (6.3-11.2) years for refractory epilepsy controls. After correcting for total brain volume and age, the left thalamus was not statistically significantly smaller in ESES patients than in healthy controls (p=0.077), in ESES patients than in refractory epilepsy controls (p=0.056); but the right thalamus was smaller in ESES patients than in healthy controls (p=0.044), and in ESES patients than in refractory epilepsy controls (p=0.033).

CONCLUSION

Patients with ESES and normal magnetic resonance imaging have smaller relative thalamic volume controlling for age and total brain volume.

Neuroprotective mechanism of Coenzyme Q10 (CoQ10) against PTZ induced kindling and associated cognitive dysfunction: Possible role of microglia inhibition

BACKGROUND

Neuroinflammation, oxidative stress and mitochondrial dysfunction play a significant role to explain the pathophysiology of epilepsy. Neuroinflammation through microglia activation has been documented in epileptogenesis. Compounds which inhibit activation of glial cells have been suggested as one of the treatment approaches for the effective treatment of epilepsy. The present study has been designed to investigate the role of coenzyme Q10 and its interaction with minocycline (microglia inhibitor) against pentylenetetrazol (PTZ) induced kindling epilepsy.

METHODS

Laca mice received Coenzyme Q10 and minocycline for a period of 29 days. PTZ (40mg/kg ip) injection has been given on alternate days. Various behavioural parameters (kindling score and elevated plus maze), biochemical parameters (lipid peroxidation, superoxide dismutase, reduced glutathione, catalase, nitrite and acetylcholinesterase) and mitochondrial enzyme complex activities of (I, II and IV) were assessed in the discrete areas of the brain.

RESULTS

Administration of a subconvulsive dose of PTZ (40mg/kg) repeatedly increased significantly kindling score, oxidative damage and impaired mitochondrial enzyme complex activities (I, II and IV) and pro-inflammatory marker (TNF-α) as compared to naive animals. Coenzyme Q10 (10, 20 and 40mg/kg) and minocycline (50 and 100mg/kg) for a duration of 29days significantly attenuated kindling score, reversed oxidative damage, TNF-α and restored mitochondrial enzyme complex activities (I, II and IV) as compared to control. Further, combinations of CoQ10 (10, 20mg/kg) with minocycline (50 and 100mg/kg) significantly modulate the protective effect of CoQ10 which was significant as compared to their effect per se in PTZ treated animals.

CONCLUSION

The present study suggests the involvement of microglia inhibition in the protective effect of CoQ10 in PTZ induced kindling in mice.

MicroRNA-328a regulates water maze performance in PTZ-kindled rats

The down-regulation of microRNA-328a (miR-328a) in pentylenetetrazole (PTZ)-kindled rats with memory impairment was demonstrated in our previous study, while any contribution of miR-328a to cognitive dysfunction of PTZ-kindled rats remains unknown. In this study we have investigated the effect and the underlying mechanism of miR-328a on the cognitive function in PTZ-kindled rats. 48 SD male rats were divided into 4 groups as follows: a PTZ kindled group, a miR-328a antagomir group, an antagomir-control group, and a sham group (n=12 for each). All rats except those from the sham group were treated with PTZ 14 times at intervals of 48h to establish the temporal lobe epilepsy (TLE) models, and miR-328a antagomir was given to the antagomir group as a treatment by lateral-ventricle injection the day after the first injection of PTZ. Morris water maze (MWM) test was performed to assay their learning and memory abilities. The down-regulation of miR-328a in the PTZ group was confirmed using RT-qPCR and the expression of miR-328a was diminished after antagomir treatment (P<0.05). In the probe test of water maze, the time and distance of the PTZ group were both shorter than those of the sham group (P<0.05), and those of the antagomir-control group were both longer than those of the antagomir group (P<0.05). In addition, we found that with the down-regulation of miR-328a, the levels of Beta-site APP-cleaving enzyme (BACE), which is a bioinformatics-predicted target of miR-328a, were up-regulated. These findings suggest that miR-328a may play a role in memory dysfunction in PTZ-kindled rats by regulating the BACE levels and this links the PTZ model with Alzheimer's disease.

Time course evaluation of behavioral impairments in the pilocarpine model of epilepsy

Epilepsy is a brain function disorder characterized by unpredictable and recurrent seizures. The majority of patients with temporal lobe epilepsy (TLE), which is the most common type of epilepsy, have to live not only with seizures but also with behavioral alterations, including anxiety, psychosis, depression, and impaired cognitive functioning. The pilocarpine model has been recognized as an animal model of TLE. However, there are few studies addressing behavioral alterations in the maturation phase when evaluating the time course of the epileptogenic process after pilocarpine administration. Therefore, the present work was designed to analyze the neurobehavioral impairments of male adult Wistar rats during maturation and chronic phases in the pilocarpine model of epilepsy. Behavioral tests included: open-field tasks, olfactory discrimination, social recognition, elevated plus maze, and the forced swimming test. The main behavioral alterations observed in both maturation and chronic phases of the pilocarpine model were olfactory and short-term social memory deficits and decrease in the immobility time in the forced swimming test. Moreover, increased anxiety-like responses were only observed in the maturation phase. These findings indicate that early behavioral impairments can be observed in the pilocarpine model during the maturation phase, and these behavioral deficits also occur during the acquired epilepsy (chronic phase). Several of the neurobehavioral impairments that are associated with epilepsy in humans were observed in the pilocarpine-treated rats, thus, rendering this animal model a useful tool to study neuroprotective strategies as well as neurobiological and psychopathological mechanisms associated with epileptogenesis.

Grouping Pentylenetetrazol-Induced Epileptic Rats According to Memory Impairment and MicroRNA Expression Profiles in the Hippocampus

Previous studies have demonstrated a close relationship between abnormal regulation of microRNA (miRNA) and various types of diseases, including epilepsy and other neurological disorders of memory. However, the role of miRNA in the memory impairment observed in epilepsy remains unknown. In this study, a model of temporal lobe epilepsy (TLE) was induced via pentylenetetrazol (PTZ) kindling in Sprague-Dawley rats. First, the TLE rats were subjected to Morris water maze to identify those with memory impairment (TLE-MI) compared with TLE control rats (TLE-C), which presented normal memory. Both groups were analyzed to detect dysregulated miRNAs in the hippocampus; four up-regulated miRNAs (miR-34c, miR-374, miR-181a, and miR-let-7c-1) and seven down-regulated miRNAs (miR-1188, miR-770-5p, miR-127-5p, miR-375, miR-331, miR-873-5p, and miR-328a) were found. Some of the dysregulated miRNAs (miR-34c, miR-1188a, miR-328a, and miR-331) were confirmed using qRT-PCR, and their blood expression patterns were identical to those of their counterparts in the rat hippocampus. The targets of these dysregulated miRNAs and other potentially enriched biological signaling pathways were analyzed using bioinformatics. Following these results, the MAPK, apoptosis and hippocampal signaling pathways might be involved in the molecular mechanisms underlying the memory disorders of TLE.

Impaired neuronal operation through aberrant intrinsic plasticity in epilepsy

OBJECTIVE

Patients with temporal lobe epilepsy often display cognitive comorbidity with recurrent seizures. However, the cellular mechanisms underlying the impairment of neuronal information processing remain poorly understood in temporal lobe epilepsy. Within the hippocampal formation neuronal networks undergo major reorganization, including the sprouting of mossy fibers in the dentate gyrus; they establish aberrant recurrent synapses between dentate granule cells and operate via postsynaptic kainate receptors. In this report, we tested the hypothesis that this aberrant local circuit alters information processing of perforant path inputs constituting the major excitatory afferent pathway from entorhinal cortex to dentate granule cells.

METHODS

Experiments were performed in dentate granule cells from control rats and rats with temporal lobe epilepsy induced by pilocarpine hydrochloride treatment. Neurons were recorded in patch clamp in whole cell configuration in hippocampal slices.

RESULTS

Our present data revealed that an aberrant readout of synaptic inputs by kainate receptors triggered a long-lasting impairment of the perforant path input-output operation in epileptic dentate granule cells. We demonstrated that this is due to the aberrant activity-dependent potentiation of the persistent sodium current altering intrinsic firing properties of dentate granule cells.

INTERPRETATION

We propose that this aberrant activity-dependent intrinsic plasticity, which lastingly impairs the information processing of cortical inputs in dentate gyrus, may participate in hippocampal-related cognitive deficits, such as those reported in patients with epilepsy.

Early life status epilepticus and stress have distinct and sex-specific effects on learning, subsequent seizure outcomes, including anticonvulsant response to phenobarbital

AIMS

Neonatal status epilepticus (SE) is often associated with adverse cognitive and epilepsy outcomes. We investigate the effects of three episodes of kainic acid-induced SE (3KA-SE) and maternal separation in immature rats on subsequent learning, seizure susceptibility, and consequences, and the anticonvulsant effects of phenobarbital, according to sex, type, and age at early life (EL) event.

METHODS

3KA-SE or maternal separation was induced on postnatal days (PN) 4-6 or 14-16. Rats were tested on Barnes maze (PN16-19), or lithium-pilocarpine SE (PN19) or flurothyl seizures (PN32). The anticonvulsant effects of phenobarbital (20 or 40 mg/kg/rat, intraperitoneally) pretreatment were tested on flurothyl seizures. FluoroJadeB staining assessed hippocampal injury.

RESULTS

3KA-SE or separation on PN4-6 caused more transient learning delays in males and did not alter lithium-pilocarpine SE latencies, but aggravated its outcomes in females. Anticonvulsant effects of phenobarbital were preserved and potentiated in specific groups depending on sex, type, and age at EL event.

CONCLUSIONS

Early life 3KA-SE and maternal separation cause more but transient cognitive deficits in males but aggravate the consequences of subsequent lithium-pilocarpine SE in females. In contrast, on flurothyl seizures, EL events showed either beneficial or no effect, depending on gender, type, and age at EL events.

Electroconvulsive stimulation reverses anhedonia and cognitive impairments in rats exposed to chronic mild stress

Electroconvulsive therapy remains the most effective treatment for depression including a fast onset of action. However, this therapeutic approach suffers from some potential drawbacks. In the acute phase this includes amnesia. Electroconvulsive stimulation (ECS) has previously been shown to reverse a depression-like state in the chronic mild stress model of depression (CMS), but the effect of ECS on cognition has not previously been investigated. In this study the CMS model was used to induce a depressive-like condition in rats. The study was designed to investigate the acute effect of ECS treatment on working memory and the chronic effect of repeated ECS treatments on depression-like behavior and working memory. The results indicated that, in the acute phase, ECS treatment induced a working memory deficit in healthy controls unexposed to stress, while repeated treatments reversed stress-induced decline in working memory, as well as recovering rats submitted to the CMS paradigm from the anhedonic-like state. Like in the clinical setting, a single ECS exposure was ineffective in inducing remission from a depression-like state.

Therapeutic potential of agomelatine in epilepsy and epileptic complications

Epilepsy is a chronic neurologic disorder which often induces numerous adverse long-term neurologic effects, such as behavioral and cognitive deficits, increased predisposition to additional seizures, and cell injury or death. Cognitive dysfunction, depression, anxiety and sleep disorders are some of the highly prevalent and most disabling complications of epilepsy. The mechanisms that lead to the generation of epileptic comorbidities are poorly understood. Treatment for epileptic complications still remains a challenge because of the poor adherence and drug interactions associated with multi drug prescriptions and also for the fear of worsening seizures by the individual medications for complications. Melatonin, an endogenous hormone secreted by pineal gland has a prominent role in epilepsy. Agomelatine is a novel antidepressant which acts as melatonin MT1 and MT2 receptor agonist and serotonin 5Ht2C receptor antagonist. The combined action at MT1/2 and 5HT2C receptors, reduction in the depolarization-evoked release of glutamate, strong neuroprotective action and possible antioxidant properties of agomelatine could make it a potential agent in the treatment of epilepsy. The effect of agomelatine on hippocampal neuronal cell survival and neurogenesis, neuroprotective effect in hippocampus and frontal cortex and the antioxidant potential may contribute to the protective action of agomelatine against epilepsy induced memory decline. Agomelatine is proven to be an antidepressant and it has relieved anxiety symptoms and improved the quality of sleep in patients with depressive disorder. The action of agomelatine as a melatonin agonist and the consequent circadian resynchronizing property as well as its action as 5-HT2C receptor antagonist, could possibly suggest an antidepressant and anxiolytic action of agomelatine in epilepsy induced depressive behavior and anxiety. Since one of the many causes of sleep disruption in epilepsy is circadian rhythm disturbances and sleep promoting and circadian effects of melatonin is attributed to the MT1 and MT2 subtypes of human melatonin receptors, agomelatine may also have a promising effect on epilepsy induced sleep disruptions. Thus with all these potential pharmacological actions, agomelatine could be recommended as a potential drug to treat epilepsy and its complications.

Long-term response to high-dose diazepam treatment in continuous spikes and waves during sleep

BACKGROUND

This study evaluated whether the reduction in epileptiform activity after treatment with high-dose diazepam in continuous spikes and waves during sleep persists over time.

PATIENTS

Patients aged 1 to 21 years with continuous spikes and waves during sleep who received high-dose nocturnal diazepam and who had electroencephalogram follow-up were included. Twenty-nine patients met the inclusion criteria and underwent a total of 48 high-dose diazepam treatment cycles.

RESULTS

An overnight reduction of the spike wave percentage of at least 25% (i.e., 75-50%) occurred in 29 cycles (20 patients), and persisted within 6 months in 16 of 29 cycles (12 patients), but returned to baseline in three of 29 cycles (three patients). An overnight reduction of at least 50% (i.e., 75-25%) occurred in 15 cycles (13 patients), and persisted within 6 months in eight of 15 cycles (eight patients), but returned to baseline in three cycles (three patients). Twenty of 29 cycles that responded in the short term had persistent response on follow-up. Thirteen cycles of treatment were associated with mild side effects that did not recur with repeated treatment cycles.

CONCLUSIONS

Treatment with high-dose diazepam reduced epileptiform activity in continuous spikes and waves during sleep in the short term, and improvement persisted for several months in most cycles. Short-term response predicted persistence of this effect on subsequent follow-up.

Continuous Spikes and Waves during Sleep: Electroclinical Presentation and Suggestions for Management

Continuous spikes and waves during sleep (CSWS) is an epileptic encephalopathy characterized in most patients by (1) difficult to control seizures, (2) interictal epileptiform activity that becomes prominent during sleep leading to an electroencephalogram (EEG) pattern of electrical status epilepticus in sleep (ESES), and (3) neurocognitive regression. In this paper, we will summarize current epidemiological, clinical, and EEG knowledge on CSWS and will provide suggestions for treatment. CSWS typically presents with seizures around 2-4 years of age. Neurocognitive regression occurs around 5-6 years of age, and it is accompanied by subacute worsening of EEG abnormalities and seizures. At approximately 6-9 years of age, there is a gradual resolution of seizures and EEG abnormalities, but the neurocognitive deficits persist in most patients. The cause of CSWS is unknown, but early developmental lesions play a major role in approximately half of the patients, and genetic associations have recently been described. High-dose benzodiazepines and corticosteroids have been successfully used to treat clinical and electroencephalographic features. Corticosteroids are often reserved for refractory disease because of adverse events. Valproate, ethosuximide, levetiracetam, sulthiame, and lamotrigine have been also used with some success. Epilepsy surgery may be considered in a few selected patients.

Issues related to symptomatic and disease-modifying treatments affecting cognitive and neuropsychiatric comorbidities of epilepsy

Many symptoms of neurologic or psychiatric illness--such as cognitive impairment, depression, anxiety, attention deficits, and migraine--occur more frequently in people with epilepsy than in the general population. These diverse comorbidities present an underappreciated problem for people with epilepsy and their caregivers because they decrease quality of life, complicate treatment, and increase mortality. In fact, it has been suggested that comorbidities can have a greater effect on quality of life in people with epilepsy than the seizures themselves. There is increasing recognition of the frequency and impact of cognitive and behavioral comorbidities of epilepsy, highlighted in the 2012 Institute of Medicine report on epilepsy. Comorbidities have also been acknowledged, as a National Institutes of Health (NIH) Benchmark area for research in epilepsy. However, relatively little progress has been made in developing new therapies directed specifically at comorbidities. On the other hand, there have been many advances in understanding underlying mechanisms. These advances have made it possible to identify novel targets for therapy and prevention. As part of the International League Against Epilepsy/American Epilepsy Society workshop on preclinical therapy development for epilepsy, our working group considered the current state of understanding related to terminology, models, and strategies for therapy development for the comorbidities of epilepsy. Herein we summarize our findings and suggest ways to accelerate development of new therapies. We also consider important issues to improve research including those related to methodology, nonpharmacologic therapies, biomarkers, and infrastructure.

Pediatric focal epilepsy syndromes

Benign epilepsy with centrotemporal spikes, early-onset childhood occipital epilepsy (Panayiotopoulos syndrome [PS]) and late-onset childhood occipital epilepsy (Gastaut type [LOCE-G]) are the principal pediatric focal epilepsy syndromes. They share major common characteristics: the appearance and resolution of electroclinical features are age related, there is a strong genetic predisposition, the clinical course is often mild with infrequent and easy to control seizures, interictal epileptiform activity is disproportionately abundant when compared with the clinical correlate, and tends to potentiate and generalize during sleep. In this review, we outline the relevant pathophysiology underlying this electroclinical spectrum. Then, the initial description of individual syndromes is followed by a summary of overlapping features and intermediate presentations that question the boundaries between these entities and provide the basis for the concept of a childhood seizure susceptibility syndrome. Additionally, we outline the main features of the related epileptic encephalopathies. An outlook on potential future lines of research completes this review.

Automated quantification of spikes

Methods for rapid and objective quantification of interictal spikes in raw, unprocessed electroencephalogram (EEG) samples are scarce. We evaluated the accuracy of a tailored automated spike quantification algorithm. The automated quantification was compared with the quantification by two board-certified clinical neurophysiologists (gold-standard) in five steps: 1) accuracy in a single EEG channel (5 EEG samples), 2) accuracy in multiple EEG channels and across different stages of the sleep-wake cycles (75 EEG samples), 3) capacity to detect lateralization of spikes (6 EEG samples), 4) accuracy after application of a machine-learning mechanism (11 EEG samples), and 5) accuracy during wakefulness only (8 EEG samples). Our method was accurate during all stages of the sleep-wake cycle and improved after the application of the machine-learning mechanism. Spikes were correctly lateralized in all cases. Our automated method was accurate in quantifying and detecting the lateralization of interictal spikes in raw unprocessed EEG samples.

A single pentylenetetrazole-induced clonic-tonic seizure episode is accompanied by a slowly developing cognitive decline in rats

According to different studies, between 5% and 10% of people suffer a single isolated seizure episode at some time in their life. However, little is known about the effects of a single seizure episode on cognitive function, and clinical investigations of this issue are not easy to perform. In this situation, animal models may be a reasonable choice. The aim of our study was to follow the time course of delayed effects of generalized clonic-tonic convulsions on learning and memory functions in rats. A clonic-tonic seizure episode was induced by a single i.p. injection of pentylenetetrazole (70 mg/kg). Different behavioral tests were performed between days 10 and 100 after the convulsant administration. A single seizure episode resulted in a gradual decline in short-term memory function as assessed by novel object recognition and social recognition tests. The seizure episode induced a quick increase in hippocampal cell proliferation; however, the excessive newly generated cells seemed to be eliminated by the time of obvious cognitive impairment. These observations are indicative of a slowly developing and long-lasting influence of a single seizure episode on cognitive function. A rather long time period between the seizure episode and the manifestations of cognitive decline provides a window for a possible therapeutic intervention, and an elaboration of such "post-conditioning" treatments may be a promising opportunity to prevent subsequent mental impairments in patients.

Electrical status epilepticus in sleep: clinical presentation and pathophysiology

Electrical status epilepticus in sleep involves an electroencephalographic pattern where interictal epileptiform activity is potentiated in the transition from wakefulness to sleep. Near-continuous spikes and waves that occupy a significant proportion of nonrapid eye movement sleep appear as a result of sleep-potentiated epileptiform activity. This electroencephalographic pattern appears in different electroclinical syndromes that present three common characteristics with different degrees of severity: seizures, sleep-potentiated epileptiform activity, and neuropsychologic regression. Continuous spikes and waves during sleep comprise the severest epileptic encephalopathy in the electroclinical spectrum. Landau-Kleffner syndrome presents with intermediate severity. Some "benign" pediatric focal epileptic syndromes represent the mildest end of this continuum. Based on published data, we provide a framework for clinical and electrical events. The underlying mechanisms leading to sleep potentiation of epileptiform activity in electrical status epilepticus in sleep are incompletely understood. A genetic basis or acquired early developmental insult may disrupt the normal maturation of neuronal networks. These factors may dynamically alter normal processes of brain development, leading to an age-related pattern of electroclinical expression of electrical status epilepticus in sleep.

Cognitive outcome of status epilepticus in children

Epileptic encephalopathy encompasses conditions in which cognitive, motor, or sensory deficits result as a consequence of epileptic activity defining certain syndromes. It therefore represents a more severe subset of epilepsy, which can be generally characterized as frequent or severe seizures leading to cerebral dysfunction. This disturbance in cerebral functioning can in turn hinder, somewhat dramatically, cognitive development and further impact the future lives of patients. In this paper, we describe the cognitive consequences of status epilepticus in children and in adults in the context of plasticity theories. Recent studies maintain that consequences of SE may be severe cognitive sequelae, especially in early life. Since the residual consequences of SE in adulthood seem less detrimental and long-lasting, we argue that early life insults, such as those created by SE, during a rapid period of development and functional specialization, result in specific cognitive deficits dependent on the sensitive period at which SE occurred.

G9a/GLP histone lysine dimethyltransferase complex activity in the hippocampus and the entorhinal cortex is required for gene activation and silencing during memory consolidation

Learning triggers alterations in gene transcription in brain regions such as the hippocampus and the entorhinal cortex (EC) that are necessary for long-term memory (LTM) formation. Here, we identify an essential role for the G9a/G9a-like protein (GLP) lysine dimethyltransferase complex and the histone H3 lysine 9 dimethylation (H3K9me2) marks it catalyzes, in the transcriptional regulation of genes in area CA1 of the rat hippocampus and the EC during memory consolidation. Contextual fear learning increased global levels of H3K9me2 in area CA1 and the EC, with observable changes at the Zif268, DNMT3a, BDNF exon IV, and cFOS gene promoters, which occurred in concert with mRNA expression. Inhibition of G9a/GLP in the EC, but not in the hippocampus, enhanced contextual fear conditioning relative to control animals. The inhibition of G9a/GLP in the EC induced several histone modifications that include not only methylation but also acetylation. Surprisingly, we found that downregulation of G9a/GLP activity in the EC enhanced H3K9me2 in area CA1, resulting in transcriptional silencing of the non-memory permissive gene COMT in the hippocampus. In addition, synaptic plasticity studies at two distinct EC-CA1 cellular pathways revealed that G9a/GLP activity is critical for hippocampus-dependent long-term potentiation initiated in the EC via the perforant pathway, but not the temporoammonic pathway. Together, these data demonstrate that G9a/GLP differentially regulates gene transcription in the hippocampus and the EC during memory consolidation. Furthermore, these findings support the possibility of a role for G9a/GLP in the regulation of cellular and molecular cross talk between these two brain regions during LTM formation.

Clinical staging and electroencephalographic evolution of continuous spikes and waves during sleep

PURPOSE

Currently, in continuous spikes and waves during sleep (CSWS) there is a lack of systematic assessments of the clinically relevant stages and the evolution of the electroencephalographic features. The aim of this study is to describe the evolution over time of clinical and electroencephalographic features in CSWS.

METHODS

We enrolled patients from our video-electroencephalography (EEG) monitoring unit with CSWS and with overnight EEG studies with at least one overnight assessment per year over a minimum period of 3 years. We studied clinical presentation and electroencephalographic features. We calculated the (1) spike-wave percentage (SWP) as the percentage of 1-s bins containing at least one spike-wave complex and (2) spike frequency (SF) as the number of spikes per 100 s.

KEY FINDINGS

Nine children (six boys) met the inclusion criteria during a 15-year period. Seven (78%) had an abnormal development prior to the epilepsy onset, and in two (22%) seizures were the only presenting symptom. Median age at epilepsy onset was 2 years (range 2 days to 4 years), at neuropsychological regression 5.1 years (4-7.7 years), and at seizure freedom 8.6 years (6.5-11.4 years). Median duration and range of clinically relevant stages were as follows: dormant stage (birth-epilepsy onset median 2 years, range 2 days-4 years), prodromal stage (epilepsy onset-neuropsychological regression 3.9 years, range 0.9-7.7 years), acute stage (neuropsychological regression-seizure freedom 2.9 years, range 2.1-6.6 years), and residual stage (after seizure freedom). Seven patients (78%) had a structural lesion on neuroimaging. At last follow-up (median 11.4 years, range 7.2-20.3 years), eight patients (89%) were receiving antiepileptic treatment, and all patients had residual neurocognitive deficits. During the acute stage, SWP was <85% in 13 (42%) of 31 assessments, and after seizure freedom, 3 of 5 patients (60%) had SWP >85%. Evolution of electroencephalographic patterns included increasing-decreasing, continuously elevated, and fluctuating patterns (33.3% each). There was good correlation between SWP and SF (Spearman correlation-coefficient = 0.942; p < 0.0001). SF, which can exceed 100%, reflected changes in electroencephalography pattern in more detail than SWP, which cannot exceed 100% and therefore has a ceiling effect.

SIGNIFICANCE

Our series systematically studied the age of occurrence of the significant clinical events. These may assist in defining clinical stages, which can provide a useful framework for future clinical trials in patients with CSWS. The severity of the epileptiform discharges on EEG did not always correlate with seizure frequency and severity; epileptiform discharges could be prominent after seizure freedom and fluctuated along the course of the disease. The values of SWP and SF correlated well, but SWP based on 1-s bins has the potential disadvantage of a ceiling effect.

Short-term response of sleep-potentiated spiking to high-dose diazepam in electric status epilepticus during sleep

We describe the short-term effects of high-dose oral diazepam on sleep-potentiated epileptiform activity in patients with electric status epilepticus during sleep. We enrolled patients treated with high-dose oral bedtime diazepam from 2001-2009. We defined spike percentage as the percentage of 1-second bins containing at least one spike, and calculated it during three randomly selected 5-minute samples of wakefulness throughout the day and during the first 5 minutes of every hour of non-rapid eye movement sleep at night. In this study, patients were considered to demonstrate sleep-potentiated epileptiform activity when their spike percentage during sleep was increased by ≥50% compared with wakefulness. Twenty-nine children (18 boys) were included (median age, 7.4 years). Twenty-four hours after receiving high-dose diazepam, epileptiform activity was significantly reduced (76.7% at baseline vs 40.8% 24 hours after high-dose diazepam; Wilcoxon signed ranks test, Z = -4.287, P < 0.0001). Seven patients (24.1%) manifested mild, reversible side effects during the first 48 hours after diazepam administration. High-dose oral diazepam effectively and safely reduced epileptiform activity in patients with electric status epilepticus during sleep.

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.

IGF-I ameliorates hippocampal neurodegeneration and protects against cognitive deficits in an animal model of temporal lobe epilepsy

Epilepsy is a major neurological disease, and patients often show spatial memory deficits. Thus, there is a need of effective new therapeutic approaches. IGF-I has been shown to be neuroprotective following a number of experimental insults to the nervous system, and in a variety of animal models of neurodegenerative diseases. In the present work, we investigated the possible neuroprotective effects of IGF-I following unilateral intrahippocampal administration of kainic acid (KA), an animal model of temporal lobe epilepsy (TLE). KA induced cell death, as shown by FluoroJade B, and extensive cell loss in both the ipsilateral and contralateral CA3 and CA4 areas, as well as granule cell dispersal in the DG, as revealed by Cresyl violet staining. KA also resulted in intense astrogliosis and microgliosis, as assessed by the number of GFAP and CD11b immunopositive cells, respectively, and increased hippocampal neurogenesis. Exposure to the Morris Water Maze task revealed that mice injected with KA were deficient in spatial learning and both short- and long-term memories, when tested in a larger diameter pool, which requires the use of allocentric strategies. When tested in a smaller pool, only long-term memory was impaired. Administration of IGF-I decreased seizure severity, hippocampal neurogenesis, and protected against neurodegeneration at the cellular level as assessed by FluoroJade B and Cresyl violet staining, as well as the number of GFAP and CD11b immunopositive cells. Furthermore, IGF-I abolished the cognitive deficits. Our results support that IGF-I could have a possible therapeutic potential in TLE.

Functional outcome after convulsive status epilepticus

OBJECTIVES

Few outcome data are available about convulsive status epilepticus managed in the intensive care unit. We studied 90-day functional outcomes and their determinants in patients with convulsive status epilepticus.

DESIGN

Two hundred forty-eight convulsive status epilepticus patients admitted to 18 intensive care units in 2005-2007 were included in a prospective observational cohort study. The main outcome measure was a Glasgow Outcome Scale score of 5 (good recovery) on day 90.

MAIN RESULTS

Convulsive status epilepticus occurred out of hospital in 177 (67%) patients, and all but 15 patients were still seizing at medical team arrival. The median time from convulsive status epilepticus onset to anticonvulsant drug initiation was 40 mins (interquartile range, 5-80). Total seizure duration was 85 mins (interquartile range, 46.5-180). Convulsive status epilepticus was refractory in 49 (20%) patients. The most common causes of convulsive status epilepticus were anticonvulsive agent withdrawal (36.4%) in patients with previous epilepsy and stroke (27.7%) in inaugural convulsive status epilepticus. Mechanical ventilation was needed in 210 (85%) patients. On day 90, 42 (18.8%) patients were dead, 87 (38.8%) had marked functional impairments (Glasgow Outcome Scale score, 2-4), and 95 (42.4%) had a good recovery (Glasgow Outcome Scale score, 5). Factors showing independent positive associations with poor outcome (Glasgow Outcome Scale score, <5) were older age (odds ratio, 1.04/year; 95% confidence interval, 1.02-1.05; p=.0005), cerebral insult (odds ratio, 2.70; 95% confidence interval, 1.37-5.26; p=.007), longer seizure duration (odds ratio, 1.72/120 min; 95% confidence interval, 1.05-2.86; p=.03), on-scene focal neurologic signs (odds ratio, 2.08; 95% confidence interval, 1.03-4.16; p=.04), and refractory convulsive status epilepticus (odds ratio, 2.70; 95% confidence interval, 1.02-7.14; p=.045).

CONCLUSIONS

Ninety days after intensive care unit admission for convulsive status epilepticus, half the survivors had severe functional impairments. Longer seizure duration, cerebral insult, and refractory convulsive status epilepticus were strongly associated with poor outcomes, suggesting a role for early neuroprotective strategies.

Effects of pentylenetetrazol-induced brief convulsive seizures on spatial memory and fear memory

Previous studies have demonstrated that in the pentylenetetrazol (PTZ) kindling model, recurrent seizures either impair or have no effect on learning and memory. However, the effects of brief seizures on learning and memory remain unknown. Here, we found that a single injection of a convulsive dose of PTZ (50 mg/kg, ip) induced brief seizures in Sprague-Dawley rats. Administration of PTZ before training impaired the acquisition of spatial memory in the Morris water maze (MWM) and fear memory in contextual fear conditioning. However, the administration of PTZ immediately after training did not affect memory consolidation in either task. These findings suggest that brief seizures have different effects on acquisition and consolidation of spatial and fear memory.

Behavioral and cognitive alterations, spontaneous seizures, and neuropathology developing after a pilocarpine-induced status epilepticus in C57BL/6 mice

Many patients with epilepsy suffer from psychiatric comorbidities including depression, anxiety, psychotic disorders, cognitive, and personality changes, but the mechanisms underlying the association between epilepsy and psychopathology are only incompletely understood. Animal models of epilepsy, such as the pilocarpine model of acquired temporal lobe epilepsy (TLE), are useful to study the relationship between epilepsy and behavioral dysfunctions. In the present study, we examined behavioral and cognitive alterations, spontaneous seizures, and neuropathology developing after a pilocarpine-induced status epilepticus in the C57BL/6 (B6) inbred strain of mice, which is commonly used as background strain for genetically modified mice. For this study, we used the same pilocarpine ramping-up dosing protocol and behavioral test battery than in a previous study in NMRI mice, thus allowing direct comparison between these two mouse strains. All B6 mice that survived SE developed epilepsy with spontaneous recurrent seizures. Epileptic B6 mice exhibited significant increases of anxiety-related behavior in the open field and light-dark box, increased locomotor activity in the open field, elevated plus maze, hole board, and novel object exploration tests, and decreased immobility in the forced swimming and tail suspension tests. Furthermore, spatial learning and memory were severely impaired in the Morris water maze, although hippocampal damage was much less severe than previously determined in NMRI mice. B6 mice in which pilocarpine did not induce SE but only single seizures did not exhibit any detectable neurodegeneration, but differed behaviorally from sham controls in several tests of the test battery used. Our data indicate that the pilocarpine model of TLE in B6 mice is ideally suited to study the neurobiological mechanisms underlying the association between seizures, brain damage and psychopathology.

Early deficits in spatial memory and theta rhythm in experimental temporal lobe epilepsy

Patients with temporal lobe epilepsy (TLE), the most common form of epilepsy in adults, often display cognitive deficits. The time course and underlying mechanisms of cognitive decline remain unknown during epileptogenesis (the process leading to epilepsy). Using the rat pilocarpine model of TLE, we performed a longitudinal study to assess spatial and nonspatial cognitive performance during epileptogenesis. In parallel, we monitored interictal-like activity (ILA) in the hippocampal CA1 region, as well as theta oscillations, a brain rhythm central to numerous cognitive processes. Here, we report that spatial memory was altered soon after pilocarpine-induced status epilepticus, i.e., already during the seizure-free, latent period. Spatial deficits correlated with a decrease in the power of theta oscillations but not with the frequency of ILA. Spatial deficits persisted when animals had spontaneous seizures (chronic stage) without further modification. In contrast, nonspatial memory performances remained unaffected throughout. We conclude that the reorganization of hippocampal circuitry that immediately follows the initial insult can affect theta oscillation mechanisms, in turn, resulting in deficits in hippocampus-dependent memory tasks. These deficits may be dissociated from the process that leads to epilepsy itself but could instead constitute, as ILA, early markers in at-risk patients and/or provide beneficial therapeutic targets.

Neurobiological mechanisms of developmental epilepsy: translating experimental findings into clinical application

Although seizures are very common during early brain development, consequences of seizures during this age period are less severe than in the mature brain. Reasons for this discrepancy relate to both the sequential development of neural elements (ion channels, neurotransmitters, synapses, and circuits) and the effects of seizures on these ongoing processes at different ages. In this review, I critically discuss 2 recent experimental trends in developmental neurobiology that impact seizures and their consequences. First, the paradoxic excitatory effects of gamma-aminobutyric acid early in life are related to seizure susceptibility in this developmental period. Second, the plasticity of immature neuronal circuits and the effects of seizures on subsequent cognition and behavior as a function of age are considered. These topics are relevant to the pediatric neurologist when evaluating and treating a young child with seizures.

Epileptogenesis in experimental models

Epileptogenesis refers to a phenomenon in which the brain undergoes molecular and cellular alterations after a brain-damaging insult, which increase its excitability and eventually lead to the occurrence of recurrent spontaneous seizures. Common epileptogenic factors include traumatic brain injury (TBI), stroke, and cerebral infections. Only a subpopulation of patients with any of these brain insults, however, will develop epilepsy. Thus, there are two great challenges: (1) identifying patients at risk, and (2) preventing and/or modifying the epileptogenic process. Target identification for antiepileptogenic treatments is difficult in humans because patients undergoing epileptogenesis cannot currently be identified. Animal models of epileptogenesis are therefore necessary for scientific progress. Recent advances in the development of experimental models of epileptogenesis have provided tools to investigate the molecular and cellular alterations and their temporal appearance, as well as the epilepsy phenotype after various clinically relevant epileptogenic etiologies, including TBI and stroke. Studying these models will lead to answers to critical questions such as: Do the molecular mechanisms of epileptogenesis depend on the etiology? Is the spectrum of network alterations during epileptogenesis the same after various clinically relevant etiologies? Is the temporal progression of epileptogenesis similar? Work is ongoing, and answers to these questions will facilitate the identification of molecular targets for antiepileptogenic treatments, the design of treatment paradigms, and the determination of whether data from one etiology can be extrapolated to another.

Behavioral alterations in the pilocarpine model of temporal lobe epilepsy in mice

Psychiatric disorders frequently occur in patients with epilepsy, but the relationship between epilepsy and psychopathology is poorly understood. Frequent comorbidities in epilepsy patients comprise major depression, anxiety disorders, psychosis and cognitive dysfunction. Animal models of epilepsy, such as the pilocarpine model of acquired epilepsy, are useful to study the relationship between epilepsy and behavioral dysfunctions. However, despite the advantages of mice in studying the genetic underpinning of behavioral alterations in epilepsy, mice have only rarely been used to characterize behavioral correlates of epilepsy. This prompted us to study the behavioral and cognitive alterations developing in NMRI mice in the pilocarpine model of epilepsy, using an anxiety test battery as well as tests for depression, drug-induced psychosis, spatial memory, and motor functions. In order to ensure the occurrence of status epilepticus (SE) and decrease mortality, individual dosing of pilocarpine was performed by ramping up the dose until onset of SE. This protocol was used for studying the consequences of SE, i.e. hippocampal damage, incidence of epilepsy with spontaneous recurrent seizures, and behavioral alterations. SE was terminated by diazepam after either 60, 90 or 120 min. All mice that survived SE developed epilepsy, but the severity of hippocampal damage varied depending on SE length. In all anxiety tests, except the elevated plus maze test, epileptic mice exhibited significant increases of anxiety-related behavior. Surprisingly, a decrease in depression-like behavior was observed in the forced swimming and tail suspension tests. Furthermore, epileptic mice were less sensitive than controls to most of the behavioral effects induced by MK-801 (dizocilpine). Learning and memory were impaired in epileptic mice irrespective of SE duration. Thus, the pilocarpine-treated mice seem to reflect several of the behavioral and cognitive disturbances that are associated with epilepsy in humans. This makes these animals an ideal model to study the neurobiological mechanisms underlying the association between epilepsy and psychopathology.

Epileptogenesis after cortical photothrombotic brain lesion in rats

We investigated epileptogenesis after cortical photothrombotic stroke induced with Rose Bengal dye in adult Sprague-Dawley rats. To detect spontaneous seizures, video-electroencephalograms were recorded at 2, 4, 6, 8, and 10 months for 7-14 days (24 h/day). At the end, spatial and emotional learning and memory were assessed using the Morris water-maze and fear-conditioning test, respectively, and the brains were processed for histologic analysis. Seizures were detected in 18% of rats that received photothrombosis. The average seizure frequency was 0.39 seizures per recording day and mean seizure duration was 117 s. Over 60% of seizures occurred during the dark hours. Rats with photothrombotic lesions were impaired in the water-maze (P<0.05) but not in the fear-conditioning test as compared with controls. Histology revealed that lesion depth varied from cortical layers I to VI in photothrombotic rats with epilepsy. Epileptic rats had light mossy fiber sprouting in the inner molecular layer of the dentate gyrus both ipsilateral and contralateral to the lesion. This study extends the current understanding of epileptogenesis and functional impairment after cortical lesions induced by photothrombosis. Our observations support the hypothesis that photothrombotic stroke in rats is a useful animal model for investigating the mechanisms of post-stroke epileptogenesis.

Assessing developmental outcomes in children from Kilifi, Kenya, following prophylaxis for seizures in cerebral malaria

The purpose of the study was to develop a culture-informed measure of developmental outcome and to apply it to detect differences in developmental level between children with cerebral malaria enrolled in a clinical trial to control seizures during the acute phase of the illness. The instrument was administered to a sample of 180 children, three and 12 months after discharge from hospital. The measure demonstrated high internal consistency, good inter-observer reliability, age sensitivity and strong relations with parental report of child functioning. No association was found between performance, or change in performance, with the prophylactic regime administered. The results suggested that the use of Phenobarbital in controlling provoked seizures has no observable effect on cognitive function.

Kindling increases aversion to saccharin in taste aversion learning

Kindling is a model in which an initially subconvulsive electrical stimulation of certain brain areas eventually develops a generalized seizure that produces behavioral and long term neuronal changes. In the present study we evaluated if kindling can modify conditioning taste aversion (CTA). In this paradigm animals acquire aversion to saccharin when it is presented as the conditioned stimulus (CS) followed by an injection of lithium chloride (LiCl) that induces a gastric irritation as the unconditioned stimulus (US). Male Wistar rats were implanted with bipolar electrodes aimed at the right amygdala (AMG) or at the right insular cortex (IC). The animals were stimulated daily until they reached stages 2-4 (intermediate) or until kindling was fully established (three consecutive stage 5 seizures). At least two weeks after kindling stimulation had ceased the animals were deprived of water for 24 h and given 10-min drinking sessions twice a day for 4 days. On day 5 (morning session) tap water was replaced by saccharin solution (0.1%), 20 min later the animals were injected with LiCl (7.5 ml/kg i.p., 0.2 M) to induce gastric malaise or taste aversion. After three more days of baseline consumption, water was substituted by a fresh 0.1% saccharin solution to test the aversion. AMG-kindling delayed the extinction of CTA. Animals with kindling in the IC had a higher retention than the sham kindling group; that is, they drank significantly less saccharin solution than the other groups. The results of the present experiment show that local modification of brain function induced by kindling stimulation can prolong the aversive effects of CTA.

A neuropsychological study of patients with temporal lobe epilepsy and chronic interictal psychosis

PURPOSE

To characterize the pattern of cognitive deficits in patients with temporal lobe epilepsy (TLE) and interictal (schizophrenia-like) psychosis and to examine the relationship between neuropsychological deficits and Magnetization transfer imaging.

METHODS

Twenty patients with TLE and interictal psychosis were compared to 20 non-psychotic TLE patients. Patients were matched with respect to premorbid IQ, age and conventional MRI findings. A battery of neuropsychological tests was administered. The neuropsychological tests which showed significant group differences were used for correlational analysis with magnetization transfer ratio (MTR) which provides a quantitative measure of macromolecular structural integrity.

RESULTS

Patients with interictal psychosis were significantly more impaired on executive and semantic memory tasks than the non-psychotic TLE group. Vocabulary test scores correlated significantly with MTR reduction in the left fusiform gyrus in the psychotic but not the non-psychotic group.

DISCUSSION

In this study, patients with TLE and interictal psychosis were more cognitively impaired than non-psychotic TLE patients. Our findings suggest that the cognitive deterioration in these patients may occur as the illness progresses and the causes for this are probably multifactorial. Our study also provides further evidence that MTR may be useful in investigating structural correlates of cognitive impairment.

Region-specific loss of zinc in the brain in pentylentetrazole-induced seizures and seizure susceptibility in zinc deficiency

The hippocampus is thought to be an epileptic focus in human temporal lobe epilepsy. Kainate-induced seizures decrease zinc concentrations in the hippocampus, which is also decreased in young mice fed a zinc-deficient diet for 4 weeks, and is enhanced by zinc deficiency. To understand zinc movement in the brain in epileptic seizures, zinc concentrations in the brain were measured in young mice after administration of pentylentetrazole, a GABAA receptor antagonist. Zinc concentration in the hippocampus and Timm's stain, with which histochemically reactive zinc in the presynaptic vesicle is detected, were decreased after the administration, suggesting that excessive excitation of zinc-containing glutamatergic neurons is induced in the hippocampus with pentylentetrazole. To clarify whether the decrease in zinc concentration in the hippocampus in zinc deficiency alter seizure susceptibility, furthermore, susceptibility to pentylentetrazole-induced seizures was examined in young mice fed the zinc-deficient diet for 4 weeks. The susceptibility, unlike susceptibility to kainate-induced seizures, was not appreciably enhanced by zinc deficiency. These results suggest that the decrease in zinc concentration in the hippocampus in zinc deficiency does not influence susceptibility to pentylentetrazole-induced seizures.