Refractory Epilepsy: Clinical Overview

Polymorphism of ABCB1/MDR1 C3435T in children and adolescents with partial epilepsy is due to different criteria for drug resistance - preliminary results

Background

The diagnosis of “drug resistance” in epilepsy can be defined and interpreted in various ways. This may be due to discrepant definitions of drug resistance to pharmacotherapy.

The aim of our study was to investigate the relationship between C3435T polymorphism of the MDR1 gene and drug resistance in epilepsy with the consideration of 4 different criteria for qualification to groups sensitive and resistant to applied pharmacotherapy.

Material/Methods

Evaluation of C3435T polymorphism of MDR1/ABCB1 gene was conducted on a group of 82 white children and young adolescents up to 18 years old. While qualifying the patients to the group of sensitive or drug resistant, the following 4 definitions of drug resistance were applied: the ILAE’s, Appleton’s, Siddiqui’s, and Berg’s.

Results

A detailed analysis of genotypes of the MDR1 gene did not show any significant discrepancies between the groups of patients resistant and sensitive to antiepileptic drugs (AEDs) in 4 consecutive comparisons taking into consideration various criteria of sensitivity and resistance to pharmacotherapy.

Conclusions

The obtained results clearly confirm the lack of a connection between the occurrence of drug-resistant epilepsy and C435T polymorphism of the MDR1 gene irrespective of the definition of drug resistance applied to the patient.

Focus on desynchronization rather than excitability: a new strategy for intraencephalic electrical stimulation

Epilepsy is a severely debilitating brain disease, often associated with premature death, which has an urgent need for alternative methods of treatment. In fact, roughly 25% of patients with epilepsy do not have seizures satisfactorily controlled by pharmacological treatment, and 30% of these patients with treatment-refractory seizures are not even eligible for ablative surgery. Epilepsy is most readily identifiable by its seizures and/or paroxysmal events, mostly viewed as spontaneously recurrent and unpredictable, which are caused by stereotyped changes in neurological function associated with hyperexcitability and hypersynchronicity of the underlying neural networks. Treatment has strongly been based on the fixed goal of depressing neuronal activity, working under the veiled assumption that hyperexcitability would lead to synchronous neuronal activity and, therefore, to seizure. Over the last 20-30 years, the emergence of electrical (ES) of deep brain structures, a practicable option for treating patients with otherwise untreatable seizures, has broadened our understanding of anticonvulsant mechanisms that conceptually differ from those of pharmacological treatment. Conversely, the research on ES therapy applied to epilepsy is contributing significantly to untwine the phenomena of excitation from that of synchronization as potential target mechanisms for abolishing seizures and predicting paroxysmal events. This paper is, thus, an addendum to other reviews on the subject of ES therapy in epilepsy which focuses on the desynchronization effect ES has on epileptogenic neural networks rather than its effect on overall brain excitability.

Exposure to rufinamide and risks of CNS adverse events in drug-resistant epilepsy: a meta-analysis of randomized, placebo-controlled trials

AIM

Epilepsy is a complex disease necessitating continuous development of new therapeutic strategies to encounter drug-resistant cases. Among new adjuvant antiepileptic drugs, rufinamide is structurally distinct from other antiepileptic drugs. It is used to treat partial-onset seizures and seizures associated with Lennox-Gastaut syndrome (LGS) in adult and children. To date, there has been no attempt to evaluate systematically the risks of adverse events with rufinamide.

METHODS

We performed a quantitative risk analysis of central nervous system (CNS) adverse events of rufinamide from all randomized, double-blind, add-on, placebo-controlled trials. The meta-analysis was undertaken with fixed effects models.

RESULTS

Of the 886 publications reviewed, 99 papers were retrieved and five articles met the inclusion criteria. One thousand two hundred and fifty-two patients were included. Our study showed that exposure to rufinamide was associated with a significant increase in risk of somnolence [relative ratio (RR) 1.87; 95% confidence interval (CI) 1.33, 2.62; P = 0.0003], dizziness (RR 2.66; 95% CI 2.00, 3.55; P = 0.00001), fatigue (RR 2.14; 95% CI 1.57, 2.91; P = 0.01) and headache (RR 1.28; 95% CI 1.02, 1.59, P = 0.03). In addition, exposure to rufinamide was associated with higher treatment discontinuation rates as compared with placebo (RR 2.65; 95% CI 1.74, 4.03; P = 0.00001).

CONCLUSIONS

The risk of CNS adverse events appears to be increased in patients exposed to rufinamide as well as the treatment discontinuation rates. However, although statistical associations were significant, additional long term safety studies are required to confirm the clinical significance of these findings, as most reports described only mild and moderate adverse events.

The practical impact of altered dosing on perampanel plasma concentrations: pharmacokinetic modeling from clinical studies

RATIONALE

Perampanel is a selective AMPA receptor antagonist approved for adjunctive therapy in patients with refractory partial-onset seizures. Perampanel is metabolized primarily via CYP3A4, yet it has a relatively long half-life of 105h; it is, therefore, recommended that perampanel be given once daily (preferably at bedtime). Many patients occasionally have less-than-perfect adherence to their drug regimen, and given the known pharmacokinetic interactions of perampanel with commonly used enzyme-inducing antiepileptic drugs (EIAEDs), we explored the effects of a missed dose on steady-state perampanel plasma concentrations and the ramifications of "make up" doses in these patients. Although perampanel is approved for once-daily dosing, some clinicians may elect to give perampanel as a divided dose (i.e., twice daily), so we also sought to examine the pharmacokinetic impact of twice- versus once-daily dosing.

METHODS

Pharmacokinetic simulations were performed using validated perampanel pharmacokinetic parameters, derived from 19 phase I studies in 606 subjects, to investigate the effect on perampanel plasma concentration of (1) missing a dose of perampanel followed by delayed replacement of the missed dose, (2) missing a dose followed by resumption of scheduled therapy, and (3) missing a dose in the presence/absence of carbamazepine. Simulations were done for a typical patient receiving an 8-mg once-daily or a 4-mg twice-daily dose using the nonlinear mixed effects program, NONMEM v7.2, in conjunction with PDx-pop v5.

RESULTS

Our results corroborate that given the pharmacokinetic characteristics of perampanel, a missed dose is unlikely to cause as much fluctuation in plasma concentration as would be expected for a drug with a short half-life. Importantly, simulations suggest that supplementing a missed dose 6-12h later, followed by continuation of the regular schedule, may not result in any significant "spikes" in perampanel plasma concentrations. Simulations demonstrated that twice-daily dosing offered little advantage in further flattening the concentration-time profile of perampanel in the adherent patient. However, fluctuations in plasma concentrations are minimized by twice-daily dosing in patients receiving concomitant EIAEDs.

CONCLUSIONS

These pharmacokinetic simulations suggest that the long half-life of perampanel may be advantageous in conferring a relatively smooth concentration-time profile with a once-daily or twice-daily dosing, even in the presence of concomitant EIAEDs. However, the results of the present study suggest that perampanel replacement is recommended for patients taking an EIAED to mitigate the potential risks associated with reduced exposure. Confirmation of the ultimate clinical impact of these findings will require further study.

Antiepileptic efficacy of lamotrigine in phenobarbital-resistant and -responsive epileptic rats: a pilot study

About 25% of patients with epilepsy are refractory to treatment, so that new, more effective antiepileptic drugs (AEDs) are urgently needed. Animal models that simulate the clinical situation with individuals responding and not responding to treatment are important to determine mechanisms of AED resistance and develop novel more effective treatments. We have previously developed and characterized such a model in which spontaneous recurrent seizures (SRS) develop after a status epilepticus induced by sustained electrical stimulation of the basolateral amygdala. In this model, prolonged treatment of epileptic rats with phenobarbital (PB) results in two subgroups, PB responders and PB nonresponders. When PB nonresponders were treated in previous experiments with phenytoin (PHT), 83% of the PB-resistant rats were also resistant to PHT. In the present study we examined if rats with PB resistant seizures are also resistant to lamotrigine (LTG), using continuous EEG/video recording of spontaneous seizures over 10 consecutive weeks. For this purpose, a new group of epileptic rats was produced and selected by treatment with PB into responders and nonresponders. As in previous studies, PB nonresponders had a significantly higher seizure frequency before onset of treatment. During subsequent treatment with LTG, all PB nonresponders and 60% of the PB responders exhibited >75% reduction of seizure frequency and were therefore considered as LTG responders. Plasma levels of LTG did not differ significantly between responders and nonresponders. The data of this pilot study indicate that LTG is more effective than PHT to suppress seizures in PB nonresponders in this model, but that not all PB responders also respond to LTG. Overall, our data provide further evidence that AED studies in post-SE TLE models are useful in determining and comparing AED efficacy and investigating predictors and mechanisms of pharmacoresistance.

Long-term safety and efficacy of eslicarbazepine acetate in patients with focal seizures: results of the 1-year ESLIBASE retrospective study

BACKGROUND

Eslicarbazepine acetate (ESL) is a new antiepileptic drug (AED) licensed as adjunctive therapy in adults with partial-onset or focal seizures.

OBJECTIVE

To evaluate in a clinical practice setting the long-term efficacy and safety of ESL in patients with focal seizures.

METHODS

ESLIBASE was a retrospective study that included all patients with focal seizures who started ESL between January 2010 and July 2012 at 12 hospitals. ESL was prescribed individually according to real-life practice. Efficacy and safety were evaluated over 1 year. Switching from carbamazepine (CBZ) and oxcarbazepine (OXC) was assessed.

RESULTS

Three hundred and twenty-seven patients were included; 78% of patients were taking ≥2 other AEDs at baseline. Most (87%) began ESL because of poor seizure control and 13% because of adverse events (AEs) with CBZ or OXC. After 1 year, 237 patients (72.4%) remained on ESL. At 3, 6 and 12 months, the responder rate was 46.3%, 57.9%, and 52.5%, and 21.0%, 28.0%, and 25.3% of patients were seizure free. The responder rate significantly increased when ESL was combined with a non-sodium channel-targeting drug (non-SC drug) (66.7%) versus an SC drug (47.7%; p<0.001). At 12 months, 40.7% of patients had ≥1 AE; AEs led to treatment discontinuation in 16.2%. Dizziness, nausea, and somnolence were the most common AEs. The tolerability profile improved in >50% of the patients who switched from CBZ or OXC to ESL because of AEs.

CONCLUSIONS

ESL was well tolerated and effective in a real-world setting over 1 year. Side-effect profile improved when OXC and CBZ recipients were switched to ESL.

Elevated expression of pleiotrophin in pilocarpine-induced seizures of immature rats and in pentylenetetrazole-induced hippocampal astrocytes in vitro

Pleiotrophin (PTN) is a secreted extracellular matrix (ECM)-associated cytokine that has emerged as an important neuromodulator with multiple neuronal functions. In the present study, we detected and compared the dynamic expression of PTN in the hippocampus and adjacent cortex of immature rats with pilocarpine-induced epilepsy. Moreover, we also confirmed the results by examining PTN expression in hippocampal astrocytes cultured in the presence of pentylenetetrazole (PTZ). Immunohistochemistry showed faint immunostaining of PTN in the control hippocampus and adjacent cortex. Notably, PTN immunoreactivity began to increase in relatively small cells in the hippocampus and adjacent cortex at 2h and 3 weeks after seizures, and the labeling intensity reached the maximum level in the hippocampus and adjacent cortex at 8 weeks after seizures. Furthermore, we also found that PTZ treatment significantly reduced astrocytic viability in a dose-dependent manner and time-dependently increased expression levels of PTN in hippocampal astrocytes. In conclusion, our data suggest that increased expression of PTN in the brain tissues may be involved in epileptogenesis.

Trigeminal nerve stimulation: A new way of treatment of refractory seizures

Background:

Refractory epilepsy is a significant problem in clinical practice. Sometimes, multiple antiepileptic drugs are required to control the attacks. To avoid various complications ensuring from these drugs, new methods of treatment such as vagus nerve stimulation (VNS) have been recommended. Trigeminal nerve stimulation (TNS) is a new method under evaluation. The purpose of this paper is to determine whether this method is effective or not.

Materials and Methods:

Percutaneous simulation of supraorbital branches of the trigeminal nerve by an electrical device was planned in 18 patients over a six-month period. Participants who fulfilled the research criteria were selected randomly from epileptic patients referred to the clinic. (November 2011-December 2012). T-test was used for data analysis.

Results:

Only eight of 18 patients stayed in the study during all 6 months. A 47.9% reduction in daily seizure frequency was seen in this group (P = 0.022). Other subjects left the study earlier. In this group, seizure frequency increased by 10.6% (P = 0.82).

Conclusions:

The mechanism of the antiepileptic effects of TNS is not yet clear. In animal studies, it is suggested that the trigeminal nucleus and its projection to nucleus tractus solitarius (NTS) and the locus ceruleus, are involved in seizure modulation. Although in comparison with seizure frequency prior to the study there was significant seizure reduction, according to the usual criteria for VNS i.e. 50% seizure frequency reduction, the effect of TNS per se may not yet be adequate for treatment of seizures. Trigeminal nerve stimulation may be an effective “adjuvant” method for treatment of intractable seizure.

Multidrug resistance 1 (MDR1) 3435C/T genotyping in childhood drug-resistant epilepsy

INTRODUCTION

A mutation at nucleotide position 3435 in exon 26 of the multidrug resistance 1 (MDR1) gene is the most frequently studied polymorphism in relation to multidrug resistance. However, there are conflicting data as to whether the CC or TT genotype of the 3435C>T polymorphism is associated with drug resistance.

METHODS AND RESULTS

We investigated the association between this polymorphism in drug-resistant childhood epilepsy by comparison with drug-responsive patients. In total, 59 patients with drug-resistant epilepsy, defined as having four or more seizures within a 12-month period while using three or more AEDs, 60 children with drug-responsive epilepsy who had remained seizure-free for 12months on their current AED regimen and 76 healthy children were involved in this study. Genotype frequencies in drug-resistant patients were as follows: 32.2% CC, 44.1% CT, 23.7% TT; in the drug-responsive group: 20.0% CC, 50.0% CT, 30.0% TT; in the control group: 24.3% CC, 50.0% CT, 25.7% TT. Comparison of drug-resistant and drug-responsive patients revealed no significant difference in genotype frequency. The findings of the epilepsy patients were not significantly different from those of the healthy control subjects.

CONCLUSIONS

Our study does not support any significant association between the MDR1 polymorphism and drug-resistant childhood epilepsy.

Unique behavioral characteristics and microRNA signatures in a drug resistant epilepsy model

BACKGROUND

Pharmacoresistance is a major issue in the treatment of epilepsy. However, the mechanism underlying pharmacoresistance to antiepileptic drugs (AEDs) is still unclear, and few animal models have been established for studying drug resistant epilepsy (DRE). In our study, spontaneous recurrent seizures (SRSs) were investigated by video-EEG monitoring during the entire procedure.

METHODS/PRINCIPAL FINDINGS

In the mouse pilocarpine-induced epilepsy model, we administered levetiracetam (LEV) and valproate (VPA) in sequence. AED-responsive and AED-resistant mice were naturally selected after 7-day treatment of LEV and VPA. Behavioral tests (open field, object exploration, elevated plus maze, and light-dark transition test) and a microRNA microarray test were performed. Among the 37 epileptic mice with SRS, 23 showed significantly fewer SRSs during administration of LEV (n = 16, LEV sensitive (LS) group) or VPA (n = 7, LEV resistant/VPA sensitive (LRVS) group), while 7 epileptic mice did not show any amelioration with either of the AEDs (n = 7, multidrug resistant (MDR) group). On the behavioral assessment, MDR mice displayed distinctive behaviors in the object exploration and elevated plus maze tests, which were not observed in the LS group. Expression of miRNA was altered in LS and MDR groups, and we identified 4 miRNAs (miR-206, miR-374, miR-468, and miR-142-5p), which were differently modulated in the MDR group versus both control and LS groups.

CONCLUSION

This is the first study to identify a pharmacoresistant subgroup, resistant to 2 AEDs, in the pilocarpine-induced epilepsy model. We hypothesize that modulation of the identified miRNAs may play a key role in developing pharmacoresistance and behavioral alterations in the MDR group.

Temporal rearrangement of pre-ictal PTZ induced spike discharges by low frequency electrical stimulation to the amygdaloid complex

BACKGROUND

Epilepsy is a common neurological disease affecting over 40 million people worldwide. The foremost important challenge of epileptologists has been to control and predict the recurrent and spontaneous seizures of epileptic patients. The application of low frequency electrical stimulation (LFS) in deep brain structures has shown promising results in seizure control. However, the use of LFS as a probing strategy for seizure prediction, thus contributing to a closed loop solution, is still poorly explored.

OBJECTIVE

To improve seizure prediction by producing gradually increasing phase-locked pre-ictal electrographical responses, due to the short-term plastic changes in epileptogenic neural networks, thus behaving as a "programmed" surrogate marker.

METHODS

Urethane anesthetized rats were divided into 3 groups: the PTZ-noES group was injected with pentylenetetrazole (PTZ 4 mg/ml/min flow rate) i.v. without electrical stimulation (ES); the ES-noPTZ group received ES (0.5 Hz, 0.1 ms pulse width and 0.6 mA) to the amygdaloid complex and the PTZ + ES group received simultaneously i.v. PTZ infusion and ES. After each condition, electrographical parameters and c-Fos expression of regions of interest were evaluated.

RESULTS

Although the PTZ + ES group had no evident change in the sustained electrographic seizure onset, duration and/or frequency spectrum; c-Fos labeling showed a different expression pattern when compared to the PTZ-noES and ES-noPTZ. Also, PTZ + ES formed a gradually increasing evoked potential; confirming the strong coupling of reverberant neural networks induced by ES - phase locked to stimuli.

CONCLUSION

ES induces a detectable temporal rearrangement of pre-ictal activity, which has suggestive applicability to seizure prediction.

Efficacy of verapamil as an adjunctive treatment in children with drug-resistant epilepsy: a pilot study

PURPOSE

Verapamil, a voltage-gated calcium channel blocker, has been occasionally reported to have some effect on reducing seizure frequency in drug-resistant epilepsy or status epilepticus. We aimed to investigate the efficacy of verapamil as add-on treatment in children with drug-resistant epilepsy.

METHODS

Seven children with drug-resistant structural-metabolic, unknown or genetic (e.g., Dravet syndrome [DS]) epilepsy received verapamil as an add-on drug to baseline antiepileptic therapy. Verapamil was slowly introduced at the dosage of 1mg/kg/day and titrated up to 1.5mg/kg/day. After completing the titration period, patients entered a 14-month maintenance period and were followed up at 3, 8, and 14 months. Heart monitoring was performed at baseline and at each follow-up. The primary outcome measure was the response of seizures to verapamil.

RESULTS

Three subjects with genetically determined DS showed a partial (reduction of 50-99%) response for all types of seizures. A patient with DS without known mutation showed a partial control of all types of seizures in the first 13 months; then seizures worsened and verapamil was suspended. Two patients with structural epilepsy and one with Lennox-Gastaut syndrome showed no improvement. Any side effects were recorded.

CONCLUSIONS

Add-on treatment with verapamil seems to have some effect in controlling seizures in patients with genetically determined DS. Our observations justify further research on the relationship between calcium channels, calcium channel blockers, and channelopathies.

Suppression of epileptogenesis-associated changes in response to seizures in FGF22-deficient mice

In the developing hippocampus, fibroblast growth factor (FGF) 22 promotes the formation of excitatory presynaptic terminals. Remarkably, FGF22 knockout (KO) mice show resistance to generalized seizures in adults as assessed by chemical kindling, a model that is widely used to study epileptogenesis (Terauchi et al., 2010). Repeated injections of low dose pentylenetetrazol (PTZ) induce generalized seizures ("kindled") in wild type (WT) mice. With additional PTZ injections, FGF22KO mice do show moderate seizures, but they do not kindle. Thus, analyses of how FGF22 impacts seizure susceptibility will contribute to the better understanding of the molecular and cellular mechanisms of epileptogenesis. To decipher the roles of FGF22 in the seizure phenotype, we examine four pathophysiological changes in the hippocampus associated with epileptogenesis: enhancement of dentate neurogenesis, hilar ectopic dentate granule cells (DGCs), increase in hilar cell death, and formation of mossy fiber sprouting (MFS). Dentate neurogenesis is enhanced, hilar ectopic DGCs appeared, and hilar cell death is increased in PTZ-kindled WT mice relative to PBS-injected WT mice. Even in WT mice with fewer PTZ injections, which showed only mild seizures (so were not kindled), neurogenesis, hilar ectopic DGCs, and hilar cell death are increased, suggesting that mild seizures are enough to induce these changes in WT mice. In contrast, PTZ-injected FGF22KO mice do not show these changes despite having moderate seizures: neurogenesis is rather suppressed, hilar ectopic DGCs do not appear, and hilar cell death is unchanged in PTZ-injected FGF22KO mice relative to PBS-injected FGF22KO mice. These results indicate that FGF22 plays important roles in controlling neurogenesis, ectopic migration of DGCs, and hilar cell death after seizures, which may contribute to the generalized seizure-resistant phenotype of FGF22KO mice and suggests a possibility that inhibition of FGF22 may alleviate epileptogenesis.

Perampanel: expanding therapeutic options for patients with medically refractory secondary generalized convulsive seizures

To evaluate the efficacy of adjunctive, once-daily perampanel against secondarily generalized (SG) seizures in three Phase III trials (studies 304, 305, and 306) and their extension (study 307). The Phase III studies enrolled patients (≥ 12 years) with uncontrolled partial-onset seizures despite treatment with 1-3 concomitant antiepileptic drugs. Patients completing the core Phase III studies were eligible for the extension study. Endpoints included median percent change in SG seizure frequency, 50% responder (proportion of patients achieving a ≥ 50% reduction in SG seizure frequency), 75% response, and seizure-freedom rates. In total, 1480 patients were randomized and treated in the three perampanel Phase III trials. At baseline, 71.9% of placebo-treated and 68.4% of perampanel-treated patients had a history of SG seizures. In the individual core Phase III studies, perampanel (4-12 mg) reduced seizure frequency and improved responder rates. Consistent with this, in pooled analyses of the Phase III data, the median percent change in SG seizure frequency was -48.6%, -62.9%, and -53.3% with perampanel 4, 8, and 12 mg, respectively, vs -19.4% with placebo; 50% responder rates were 49.3%, 60.5%, and 53.7% vs 37.0% with placebo. More perampanel-treated patients had ≥ 75% reductions in SG seizure frequency, and seizure-freedom rates improved, compared with placebo. Improvements in seizure frequency and responder rate were maintained during the extension study. Perampanel consistently demonstrated efficacy against SG seizures when assessed using various endpoints. Furthermore, reductions in seizure frequency and improvements in responder rate were sustained with long-term perampanel treatment.

Development of perampanel in epilepsy

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors play a key role in mediating glutamatergic transmission in the cortex. Perampanel (2-[2-oxo-1-phenyl-5-pyridin-2-yl-1,2-dihydropyridin-3-yl] benzonitrile) is a potent, orally active, highly selective, non-competitive AMPA-type glutamate receptor antagonist, identified via a focused discovery program at Eisai Research Laboratories. Development of perampanel as adjunctive therapy for the treatment of partial-onset seizures was planned in keeping with regulatory guidance and guidelines on antiepileptic drug (AED) development. This is the first AED with a specific action on glutamate-mediated excitatory neurotransmission to show evidence of efficacy and tolerability in reducing treatment-refractory partial-onset seizures in Phase III clinical trials. Perampanel (Fycompa(®)) has been approved in the EU and the United States for adjunctive treatment of partial-onset seizures.

Open study of pranlukast add-on therapy in intractable partial epilepsy

Innovative treatments of epileptic seizures are needed to improve the outcome of epilepsy. We studied the effect of pranlukast on seizure outcome in patients with intractable partial epilepsy. An open study was conducted to evaluate the clinical efficacy of 24-week pranlukast add-on therapy in 50 patients with intractable partial seizures. Serum concentrations of matrix metalloproteinase (MMP)-9 were determined using Biotrak Activity Assay System. Cytokines in cerebrospinal fluid (CSF) were measured by the BioPlex (BioRad) system and soluble TNF receptor1 (sTNFR1) in CSF was measured by the ELISA. Surface markers of lymphocytes in CSF were examined by cell-sorter. Seizure-free rate (SFR) was 13.6%, responder rate (RR) was 47.7%, and aggravation rate (AR) was 18.2% at the 13-24 week period after starting pranlukast. In patients with increased serum MMP-9 before pranlukast therapy (baseline), comparison of paired serum levels showed a significant decrease after pranlukast therapy. Baseline CSF levels of IL-1β and IL-6 were elevated in patients compared with disease controls. Of four patients with paired data, three (including a responder to pranlukast) showed decreased pro-inflammatory cytokines (IL-1β, IL-6, and TNFα), and four showed decreased sTNFR1, after pranlukast treatment, and only a responder had markedly decreased frequency of CD8+ T cells in CSF. Pranlukast reduces seizure frequencies probably by pleiotropic effects including normalization of MMP-9 in sera, reduced leakage of pro-inflammatory cytokines into CNS, and inhibition of extravasation of leucocytes from brain capillaries. Further investigations by double-blind control study and animal models are warranted.

Vigabatrin inhibits seizures and mTOR pathway activation in a mouse model of tuberous sclerosis complex

Epilepsy is a common neurological disorder and cause of significant morbidity and mortality. Although antiseizure medication is the first-line treatment for epilepsy, currently available medications are ineffective in a significant percentage of patients and have not clearly been demonstrated to have disease-specific effects for epilepsy. While seizures are usually intractable to medication in tuberous sclerosis complex (TSC), a common genetic cause of epilepsy, vigabatrin appears to have unique efficacy for epilepsy in TSC. While vigabatrin increases gamma-aminobutyric acid (GABA) levels, the precise mechanism of action of vigabatrin in TSC is not known. In this study, we investigated the effects of vigabatrin on epilepsy in a knock-out mouse model of TSC and tested the novel hypothesis that vigabatrin inhibits the mammalian target of rapamycin (mTOR) pathway, a key signaling pathway that is dysregulated in TSC. We found that vigabatrin caused a modest increase in brain GABA levels and inhibited seizures in the mouse model of TSC. Furthermore, vigabatrin partially inhibited mTOR pathway activity and glial proliferation in the knock-out mice in vivo, as well as reduced mTOR pathway activation in cultured astrocytes from both knock-out and control mice. This study identifies a potential novel mechanism of action of an antiseizure medication involving the mTOR pathway, which may account for the unique efficacy of this drug for a genetic epilepsy.

A Case of Refractory Seizures Caused by an Unusual Zoonosis

A 29-year-old female presented to the intensive care unit with refractory status epilepticus. Despite treatment with anticonvulsants and sedation, she continued to have EEG evidence of seizure activity that terminated only with volatile anaesthetic agents. There was serological evidence of exposure to a flavivirus. In the UK the only endemic flavivirus is Louping ill, which is closely related to tick-borne encephalitis. It was likely that this was the cause. She remained on intensive care for almost six months and failed to regain consciousness.

Several new diverse anticonvulsant agents discovered in a virtual screening campaign aimed at novel antiepileptic drugs to treat refractory epilepsy

A virtual screening campaign was conducted in order to discover new anticonvulsant drug candidates for the treatment of refractory epilepsy. To this purpose, a topological discriminant function to identify antiMES drugs and a sequential filtering methodology to discriminate P-glycoprotein substrates and nonsubstrates were jointly applied to ZINC 5 and DrugBank databases. The virtual filters combine an ensemble of 2D classifiers and docking simulations. In the light of the results, 10 structurally diverse compounds were acquired and tested in animal models of seizure and the rotorod test. All 10 candidates showed some level of protection against MES test.

Ezogabine: An Evaluation of Its Efficacy and Safety as Adjunctive Therapy for Partial-Onset Seizures in Adults

Objective:

To evaluate the safety, efficacy, pharmacokinetics, pharmacodynamic properties, and clinical application of ezogabine (retigabine. INN), an antiepileptic drug approved in 2011.

Data Sources:

Published data from in vitro, animal, and clinical studies were obtained from PubMed and CINAHL searches, from January 1980 to March 31, 2012. Other relevant data regarding the safety and efficacy of ezogabine were obtained from the Food and Drug Administration and the European Medication Agency Web sites.

Study Selection and Data Extraction:

Selected articles were prospective in vitro, animal, and controlled clinical studies of ezogabine. Non-English-language articles were excluded.

Data Synthesis:

In vitro and animal studies show that ezogabine activates voltage-gated potassium channels, leading to reduction of seizure frequency by inhibiting hyperexcitability activity in the central nervous system. Additionally, ezogabine enhances γ-aminobutyric acid (GABA) activity and de novo GABA synthesis. Eight clinical studies of ezogabine have been published, 5 being Phase 1 clinical trials in healthy subjects and 3 being Phase 3 clinical trials in patients with pharmacoresistant partial-onset seizures. Phase 3 clinical trials demonstrated the safety and efficacy of ezogabine in patients with partial-onset seizures.

Conclusions:

Clinical trials have shown that ezogabine is efficacious as an adjunctive agent in patients with pharmacoresistant partial seizures. Careful monitoring of drug interactions and adverse reactions is necessary. While ezogabine is efficacious (or partial seizures, its precise role in the management of patients with epilepsy is yet to be determined.

Perampanel, a selective, noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist, as adjunctive therapy for refractory partial-onset seizures: interim results from phase III, extension study 307

PURPOSE

To evaluate safety, tolerability, and seizure outcome data during long-term treatment with once-daily adjunctive perampanel (up to 12 mg/day) in patients with refractory partial-onset seizures.

METHODS

Study 307 was an extension study for patients completing the double-blind phase of three pivotal phase III trials (studies 304, 305, and 306). The study consisted of two phases: an open-label treatment phase (including a 16-week blinded conversion period and a planned 256-week maintenance period) and a 4-week follow-up phase. Patients were blindly titrated during the conversion period to their individual maximum tolerated dose (maximum 12 mg/day). Adverse events (AEs) were monitored throughout the study and seizure frequency recorded. The interim data cutoff date for analyses was December 1, 2010.

KEY FINDINGS

In total, 1,218 patients were enrolled in the study. At the interim cutoff date, 1,186 patients were in the safety analysis set; 1,089 (91.8%) patients had >16 weeks of exposure to perampanel, 580 (48.9%) patients had >1 year of exposure, and 19 (1.6%) patients had >2 years of exposure. At the interim analysis, 840 (70.8%) patients remained on perampanel treatment. The large majority of patients (n = 1,084 [91%]) were titrated to 10 mg or 12 mg/day. Median (range) duration of exposure was 51.4 (1.1-128.1) weeks. Treatment-emergent AEs were reported in 87.4% of patients. The most frequent were dizziness (43.9%), somnolence (20.2%), headache (16.7%), and fatigue (12.1%). Serious AEs were reported in 13.2% of patients. In the intent-to-treat analysis set (n = 1,207), the frequency of all seizures decreased over the first 26 weeks of perampanel treatment in patients with at least 26 weeks of exposure to perampanel (n = 1,006 [83.3%]); this reduction was maintained in patients with at least 1 year of exposure (n = 588 [48.7%]). The overall median percent changes in seizure frequency in patients included in each 13-week interval of perampanel treatment were -39.2% for weeks 14-26 (n = 1,114), -46.5% for weeks 40-52 (n = 731), and -58.1% for weeks 92-104 (n = 59). Overall responder rates in patients included in each 13-week interval of perampanel treatment were 41.4% for weeks 14-26 (n = 1,114), 46.9% for weeks 40-52 (n = 731), and 62.7% for weeks 92-104 (n = 59). During the blinded conversion period, the reduction in seizure frequency in patients previously randomized to placebo (-42.4%, n = 369) was similar to that in patients previously randomized to perampanel (-41.5%, n = 817).

SIGNIFICANCE

Consistent with pivotal phase III trials, these interim results demonstrated that perampanel had a favorable tolerability profile in patients with refractory partial-onset seizures over the longer term. The decrease in seizure frequency was consistent and maintained in those patients over at least 1 year of perampanel exposure.

Cerebral expression of drug transporters in epilepsy

Over-expression of drug efflux transporters at the level of the blood-brain barrier (BBB) has been proposed as a mechanism responsible for multidrug resistance. Drug transporters in epileptogenic tissue are not only expressed in endothelial cells at the BBB, but also in other brain parenchymal cells, such as astrocytes, microglia and neurons, suggesting a complex cell type-specific regulation under pathological conditions associated with epilepsy. This review focuses on the cerebral expression patterns of several classes of well-known membrane drug transporters such as P-glycoprotein (Pgp), and multidrug resistance-associated proteins (MRPs) in the epileptogenic brain. Both experimental and clinical evidence of epilepsy-associated cerebral drug transporter regulation and the possible mechanisms underlying drug transporter regulation are discussed. Knowledge of the cerebral expression patterns of drug transporters in normal and epileptogenic brain will provide relevant information to guide strategies attempting to overcome drug resistance by targeting specific transporters.

Functional MRI applications in epilepsy surgery

Functional magnetic resonance imaging (fMRI) is a non-invasive neuroimaging technique that has grown rapidly in popularity over the past decade. It is already prevalent in psychology, cognitive and basic neuroscience research and is being used increasingly as a tool for clinical decision-making in epilepsy. It has been used to determine language location and laterality in patients, sometimes eliminating the need for invasive tests. fMRI can been used pre-surgically to guide resection margins, preserving eloquent cortex. Other fMRI paradigms assessing memory, visual and somatosensory systems have limited clinical applications currently, but show great promise. Simultaneous recording of electroencephalogram (EEG) and fMRI has also provided insights into the networks underlying seizure generation and is increasingly being used in epilepsy centres. In this review, we present some of the current clinical applications for fMRI in the pre-surgical assessment of epilepsy patients, and examine a number of new techniques that may soon become clinically relevant.

Anticonvulsant activity of artificial sweeteners: a structural link between sweet-taste receptor T1R3 and brain glutamate receptors

A virtual screening campaign based on application of a topological discriminant function capable of identifying novel anticonvulsant agents indicated several widely-used artificial sweeteners as potential anticonvulsant candidates. Acesulfame potassium, cyclamate and saccharin were tested in the Maximal Electroshock Seizure model (mice, ip), showing moderate anticonvulsant activity. We hypothesized a probable structural link between the receptor responsible of sweet taste and anticonvulsant molecular targets. Bioinformatic tools confirmed a highly significant sequence-similarity between taste-related protein T1R3 and several metabotropic glutamate receptors from different species, including glutamate receptors upregulated in epileptogenesis and certain types of epilepsy.

Noninvasive approach to focal cortical dysplasias: clinical, EEG, and neuroimaging features

Purpose. The main purpose is to define more accurately the epileptogenic zone (EZ) with noninvasive methods in those patients with MRI diagnosis of focal cortical dysplasia (FCD) and epilepsy who are candidates of epilepsy surgery. Methods. Twenty patients were evaluated prospectively between 2007 and 2010 with comprehensive clinical evaluation, video-electroencephalography, diffusion tensor imaging (DTI), and high-resolution EEG to localize the equivalent current dipole (ECD). Key Findings. In 11 cases with white matter asymmetries in DTI the ECDs were located next to lesion on MRI with mean distance of 14.63 millimeters with topographical correlation with the EZ. Significance. We could establish a hypothesis of EZ based on Video-EEG, high-resolution EEG, ECD method, MRI, and DTI. These results are consistent with the hypothesis that the EZ in the FCD is complex and is often larger than visible lesion in MRI.

Epileptiform activity in the CA1 region of the hippocampus becomes refractory to attenuation by cannabinoids in part because of endogenous γ-aminobutyric acid type B receptor activity

The anticonvulsant properties of marijuana have been known for centuries. The recently characterized endogenous cannabinoid system thus represents a promising target for novel anticonvulsant agents; however, administration of exogenous cannabinoids has shown mixed results in both human epilepsy and animal models. The ability of cannabinoids to attenuate release of both excitatory and inhibitory neurotransmitters may explain the variable effects of cannabinoids in different models of epilepsy, but this has not been well explored. Using acute mouse brain slices, we monitored field potentials in the CA1 region of the hippocampus to characterize systematically the effects of the cannabinoid agonist WIN55212-2 (WIN) on evoked basal and epileptiform activity. WIN, acting presynaptically, significantly reduced the amplitude and slope of basal field excitatory postsynaptic potentials as well as stimulus-evoked epileptiform responses induced by omission of magnesium from the extracellular solution. In contrast, the combination of omission of magnesium plus elevation of potassium induced an epileptiform response that was refractory to attenuation by WIN. The effect of WIN in this model was partially restored by blocking γ-aminobutyric acid type B (GABA(B) ), but not GABA(A) , receptors. Subtle differences in models of epileptiform activity can profoundly alter the efficacy of cannabinoids. Endogenous GABA(B) receptor activation played a role in the decreased cannabinoid sensitivity observed for epileptiform activity induced by omission of magnesium plus elevation of potassium. These results suggest that interplay between presynaptic G protein-coupled receptors with overlapping downstream targets may underlie the variable efficacy of cannabinoids in different models of epilepsy.

Anatomically dependent anticonvulsant properties of temporally-coded electrical stimulation

In the PTZ animal model of epilepsy, electrical stimulation applied to the amygdaloid complex may result in either pro-convulsive or anticonvulsant effect, depending on the temporal pattern used (i.e. periodic-PS and non-periodic-NPS electrical stimulation). Our hypothesis is that the anatomical target is a determinant factor for the differential effect of temporally-coded patterns on seizure outcome. The threshold dose of PTZ to elicit forelimb clonus and generalized tonic-clonic seizure behavior was measured. The effect of amygdaloid complex PS on forelimb clonus threshold showed a pro-convulsive effect while NPS was anticonvulsant. NPS also significantly increased generalized tonic-clonic threshold; while PS, although at lower threshold levels, did not present statistical significance. Thalamus stimulation did not affect forelimb clonus threshold and showed similar anticonvulsant profiles for both PS and NPS on generalized tonic-clonic threshold. In summary, the anatomical target is a determinant factor on whether temporally-coded ES differentially modulates seizure outcome.

Evaluation of anticonvulsant and nootropic effect of ondansetron in mice

The role of serotonin receptors have been implicated in various types of experimentally induced seizures. Ondansetron is a highly selective 5-hydroxytryptamine 3 (5-HT3) receptor antagonist used as antiemetic agent for chemotherapy-, and radiotherapy-induced nausea and vomiting. The present study was carried out to examine the effect of ondansetron on electroshock, pentylenetetrazole (PTZ)-induced seizures and cognitive functions in mice. Ondansetron was administered intraperitoneally (i.p.) at doses of 0.5, 1.0 and 2.0 mg/kg (single dose) to observe its effect on the increasing current electroshock seizure (ICES) test and PTZ-induced seizure test. In addition, a chronic study (21 days) was also performed to assess the effects of ondansetron on electroshock-induced convulsions and cognitive functions. The effect on cognition was assessed by elevated plus maze and passive avoidance paradigms. Phenytoin (25 mg/kg, i.p.) was used as a standard anticonvulsant drug and piracetam (200 mg/kg) was administered as a standard nootropic drug. The results were compared with an acute study, wherein it was found that the administration of ondansetron (1.0 and 2.0 mg/kg) significantly raised the seizure-threshold current as compared to control group in the ICES test. Similar results were observed after chronic administration of ondansetron. In PTZ test, ondansetron in all the three tested doses failed to show protective effect against PTZ-induced seizure test. Administration of ondansetron for 21 days significantly decreased the transfer latency (TL) and prolonged the step-down latency (SDL). The results of present study suggest the anticonvulsant and memory-enhancing effect of ondansetron in mice.

Alleviation of Ferric Chloride-Induced Seizures and Retarded Behaviour in Epileptic Rats by Cortical Electrical Stimulation Treatment

OBJECTIVE: To study the effects of low-frequency cortical electrical stimulation (CES) on seizures and behaviour in a rat model of epilepsy induced by ferric chloride (FeCl3). METHODS: Rats were randomly assigned into four groups ( n = 8 per group): normal healthy rats; saline-treated control rats; FeCl3-induced epileptic rats; CES-treated FeCl3-induced epileptic rats. Behavioural tests, analysis of the levels of brain-derived neurotrophic factor (BDNF) protein in brain tissue, and ultrastructural studies using transmission electron microscopy (TEM) were undertaken. RESULTS: CES significantly decreased the number and grade of seizures, and improved rat behaviour, compared with untreated epileptic rats. CES reduced levels of BDNF protein in the forebrain and increased levels of BDNF protein in the hippocampus compared with untreated epileptic rats. TEM showed less damage and ultrastructural changes in the neurons of CES-treated epileptic rats. CONCLUSIONS: CES inhibited seizures in FeCl3-induced epileptic rats and improved their behaviour. These effects might be mediated by altering BDNF protein levels in the brain.

The anticonvulsant response to valproate in kindled rats is correlated with its effect on neuronal firing in the substantia nigra pars reticulata: a new mechanism of pharmacoresistance

Resistance to antiepileptic drugs (AEDs) is a major problem in epilepsy treatment. However, mechanisms of resistance are only incompletely understood. We have recently shown that repeated administration of the AED phenytoin allows selecting resistant and responsive rats from the amygdala kindling model of epilepsy, providing a tool to study mechanisms of AED resistance. We now tested whether individual amygdala-kindled rats also differ in their anticonvulsant response to the major AED valproate (VPA) and which mechanism may underlie the different response to VPA. VPA has been proposed to act, at least in part, by reducing spontaneous activity in the substantia nigra pars reticulata (SNr), a main basal ganglia output structure involved in seizure propagation, seizure control, and epilepsy-induced neuroplasticity. Thus, we evaluated whether poor anticonvulsant response to VPA is correlated with low efficacy of VPA on SNr firing rate and pattern in kindled rats. We found (1) that good and poor VPA responders can be selected in kindled rats by repeatedly determining the effect of VPA on the electrographic seizure threshold, and (2) a significant correlation between the anticonvulsant response to VPA in kindled rats and its effect on SNr firing rate and pattern. The less VPA was able to raise seizure threshold, the lower was the VPA-induced reduction of SNr firing rate and the VPA-induced regularity of SNr firing. The data demonstrate for the first time an involvement of the SNr in pharmacoresistant experimental epilepsy and emphasize the relevance of the basal ganglia as target structures for new treatment options.

Neurofibrillary tangle pathology and Braak staging in chronic epilepsy in relation to traumatic brain injury and hippocampal sclerosis: a post-mortem study

The long-term pathological effects of chronic epilepsy on normal brain ageing are unknown. Previous clinical and epidemiological studies show progressive cognitive decline in subsets of patients and an increased prevalence of Alzheimer's disease in epilepsy. In a post-mortem series of 138 patients with long-term, mainly drug-resistant epilepsy, we carried out Braak staging for Alzheimer's disease neurofibrillary pathology using tau protein immunohistochemistry. The stages were compared with clinicopathological factors, including seizure history and presence of old traumatic brain injury. Overall, 31% of cases were Braak Stage 0, 36% Stage I/II, 31% Stage III/IV and 2% Stage V/VI. The mean age at death was 56.5 years and correlated with Braak stage (P < 0.001). Analysis of Braak stages within age groups showed a significant increase in mid-Braak stages (III/IV), in middle age (40-65 years) compared with data from an ageing non-epilepsy series (P < 0.01). There was no clear relationship between seizure type (generalized or complex partial), seizure frequency, age of onset and duration of epilepsy with Braak stage although higher Braak stages were noted with focal more than with generalized epilepsy syndromes (P < 0.01). In 30% of patients, there was pathological evidence of traumatic brain injury that was significantly associated with higher Braak stages (P < 0.001). Cerebrovascular disease present in 40.3% and cortical malformations in 11.3% were not significantly associated with Braak stage. Astrocytic-tau protein correlated with the presence of both traumatic brain injury (P < 0.01) and high Braak stage (P < 0.001). Hippocampal sclerosis, identified in 40% (bilateral in 48%), was not associated with higher Braak stages, but asymmetrical patterns of tau protein accumulation within the sclerotic hippocampus were noted. In over half of patients with cognitive decline, the Braak stage was low indicating causes other than Alzheimer's disease pathology. In summary, there is evidence of accelerated brain ageing in severe chronic epilepsy although progression to high Braak stages was infrequent. Traumatic brain injury, but not seizures, was associated with tau protein accumulation in this series. It is likely that Alzheimer's disease pathology is not the sole explanation for cognitive decline associated with epilepsy.

Up-regulation of apelin in brain tissue of patients with epilepsy and an epileptic rat model

Prolonged epileptic seizures or SE can cause neuronal cell death. However, the exact role of neuroprotectant against brain injury during epileptic seizure needs to be further elucidated. The aim of this study was to investigate the expression of the apelin, a novel neuroprotective peptide, in brain tissues of the patients with temporal lobe epilepsy (TLE) and experimental rats using immunohistochemistry, immunofluorescence and Western blotting analysis and to discuss the possible role of apelin in TLE. Thirty temporal neocortical tissue samples from the patients with drug-refractory TLE underwent surgical therapy and nine histologically normal temporal lobes tissues as controls were used in our study. Fifty-six Sprague-Dawley rats were randomly divided into seven groups, including one control group and six groups with epilepsy induced by lithium-pilocarpine. Hippocampus and adjacent cortex were taken from the controls and epileptic rats at 1, 3, 7, 14, 30, and 60 days after onset of seizures. Apelin was mainly expressed in the neurons of TLE patients and controls, and was significantly increased in TLE patients compared with the controls. Apelin was also expressed in the neurons of experimental and control rats, it was gradually increased in the experimental rat post-seizure and reached a stable high level in chronic epileptic phase. Our results demonstrated that the increased expression of apelin in the brain may be involved in human TLE.

Treatment options for refractory and difficult to treat seizures: focus on vigabatrin

Complex partial seizures are often refractory to current pharmacological therapies. These difficult to treat seizures are typically managed using multiple antiepileptic drugs (AEDs). AEDs as a group are frequently associated with significant adverse drug effects, multiple drug interactions, and numerous potential clinical complications due to their individual pharmacokinetic profiles and unique drug properties. Recently, the approval of vigabatrin by the US Food and Drug Administration has necessitated that clinicians re-evaluate these risk-benefit relationships and determine where the drug fits within the treatment scheme for the management of complex partial seizures. This review will facilitate that re-evaluation through a brief review of AEDs used in the treatment of complex partial seizures, followed by a focused discussion on vigabatrin.

Drug resistance in epilepsy and the ABCB1 gene: The clinical perspective

Multidrug resistance is one of the most serious problems in the treatment of epilepsy that is likely to have a complex genetic and acquired basis. Various experimental data support the hypothesis that over-expression of antiepileptic drug (AED) transporters may play a pivotal role in drug resistance. Hyyt 6however, key questions concerning their functionality remain unanswered. The idea that P-glycoprotein, encoded by the ABCB1 gene, might mediate at least part of the drug resistance was met with both enthusiasm and skepticism. As in oncology, initial optimism has been clouded subsequently by conflicting results. The first study reporting a positive association between genetic variation in the P-glycoprotein and multidrug-resistant epilepsy was published in 2003. Since then, several other genetic association studies have attempted to verify this result. However, taken overall, the role of P-glycoprotein in drug resistance in epilepsy still remains uncertain. We intend to critically review the inherent problems associated with epilepsy pharmacogenetic studies in general and with ABCB1 polymorphisms studies in particular. The lessons learnt from the ABCB1 studies can help us to guide future association genetics studies to investigate AED resistance, and thereby taking us closer to the cherished dream of personalized AED therapy.

Medically refractory epilepsy in autism

PURPOSE

Epilepsy and electroencephalographic abnormalities are frequent in idiopathic autism, but there is little information regarding treatment-resistant epilepsy (TRE) in this group. We sought to define the clinical and electrophysiologic characteristics and treatment outcomes in these patients.

METHODS

We retrospectively reviewed clinical and laboratory data of patients with idiopathic autism evaluated at NYU Epilepsy Center during a 20-year period.

KEY FINDINGS

One hundred twenty-seven patients had idiopathic autism and at least one epileptic seizure; 33.9% had TRE and 27.5% were seizure free. The remaining 38.6% of patients had infrequent seizures or insufficient data to categorize. Patients with TRE had a significantly earlier onset of seizures than seizure-free patients, and a trend for more developmental regression and motor and language delays. Three patients had surgical resection (two had limited improvement and one had no improvement) and one had an anterior callosotomy (no improvement). Vagus nerve stimulator (VNS) implantation provided limited improvement (2 patients) and no improvement (7).

SIGNIFICANCE

This study found that TRE is common in idiopathic autism and more common with early age of seizure onset. Relatively few patients underwent surgical resection due to multifocal partial epilepsy, comorbid generalized epilepsy, or limited impact of ongoing partial seizures given other problems related to autism. Our small sample suggests that surgical and VNS outcomes in this group are less favorable than in other TRE populations.