Stiripentol: efficacy and tolerability in children with epilepsy

Stiripentol for focal refractory epilepsy

BACKGROUND

Nearly 30%of people with epilepsy do not have their seizures controlled with current treatments. Stiripentol is a new antiepileptic drug(AED) developed in France and recently approved by the European Medicines Agency (EMA) for the treatment of Dravet syndrome as an adjunctive therapy with valproate and clobazam, with a promising effect.

OBJECTIVES

To evaluate the efficacy and tolerability of stiripentol as add-on treatment for patients with focal refractory epilepsy taking any AEDs.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (19 August 2013), Cochrane Central Register of Controlled Trials(CENTRAL Issue 7, The Cochrane Library July 2013), MEDLINE (Ovid) (1946 to 19 August 2013) and EMBASE (31 May 2012).(The last search in EMBASE was made on 31th May 2012. Since then we no longer have access to that database.) We also contacted Biocodex (the manufacturer of stiripentol) and epilepsy experts to identify published, unpublished and ongoing trials.

SELECTION CRITERIA

Randomised controlled add-on trials of stiripentol in patients with focal refractory epilepsy.

DATA COLLECTION AND ANALYSIS

Review authors independently selected trials for inclusion and extracted data. The outcomes investigated included 50% or greater reduction in seizure frequency, seizure freedom, adverse effects, treatment withdrawal and changes in quality of life.

MAIN RESULTS

Using our selection criteria, one study was included (32 children with focal epilepsy). This study adopted a 'responder enriched' design.There was no clear evidence of a reduction in seizure reduction 50% seizure reduction) (RR 1.51, 95% CI 0.81 to 2.82) or in seizure freedom (RR 1.18, 95% CI 0.31 to 4.43) with add on stiripentol compared with placebo. Add-on stiripentol led to a greater risk of adverse effects considered as a whole (RR 2.65, 95% CI 1.08 to 6.47) compared with placebo. When considered as specific adverse events, the confidence intervals are very wide and include the possibility of substantial increases and small reductions in the risk of neurological (RR 2.65, 95% CI 0.88 to 8.01) or gastrointestinal adverse effects (RR 11.56, 95% CI 0.71 to 189.36). There was no clear reduction in the risk of study withdrawal (RR 0.66, 95% CI 0.30 to 1.47), which was high in both groups (35.0% in add-on placebo and 53.3% in stiripentol group). The external validity of the study was limited because only responders to stiripentol (that is patients experiencing at least a 50% decrease in seizure frequency compared with baseline) were included in the randomised add on placebo-controlled double-blind phase. Furthermore, a carry-over and a withdrawal effect probably affected the outcome related to seizure frequency. Although restricted by the very limited information derived by the only one included study, adverse effects considered as a whole seemed to occur significantly more often with add-on stiripentol compared with add-on placebo.

AUTHORS' CONCLUSIONS

No conclusions can be drawn to support the use of stiripentol as add-on treatment for focal refractory epilepsy. Further large, randomised,well-conducted trials are needed.

Novel de novo SCN2A mutation in a child with migrating focal seizures of infancy

BACKGROUND

Migrating focal seizures of infancy are characterized by seizure onset within 7 months of age, migrating focal motor seizures with multifocal ictal electroencephalography discharges intractable to conventional antiepileptic drugs, and poor prognosis. Reported genetic etiologies include SCN1A and KCNT1 mutations and homozygous deletion of the PLCB1 gene. Here we report a novel SCN2A mutation in a child with this syndrome.

PATIENT

A 7-week-old girl was admitted to our hospital for management of status epilepticus. She was the product of a full-term unremarkable pregnancy. Seizures started around 5 weeks of age and remained medically refractory. Electroencephalography showed multifocal epileptiform discharges as well as seizures arising from multifocal regions in both cerebral hemispheres. Based on her phenotype, a diagnosis of migrating focal seizures of infancy was made.

RESULT

A novel de novo missense mutation was identified in the SCN2A gene, exon 22 (coding for voltage-gated sodium channel type II): c.3977T>A (p.V1326D). This mutation affects a highly evolutionarily conserved area of the gene and replaces hydrophobic nonpolar valine with polar aspartic acid; thus, it is predicted to affect protein function and is presumed pathogenic.

DISCUSSION

This report expands our knowledge of the genetic basis of migrating focal seizures of infancy to include mutations in SCN2A gene.

Antiepileptic drugs for the treatment of severe myoclonic epilepsy in infancy

BACKGROUND

Severe myoclonic epilepsy in infants (SMEI), also known as Dravet syndrome, is a rare, refractory form of epilepsy, for whose treatment stiripentol (STP) has been recently licensed for add-on use.

OBJECTIVES

To evaluate the efficacy and tolerability of STP and other antiepileptic drug treatments (including ketogenic diet) as therapy for patients with SMEI.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialised Register (15 May 2013), the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 4 of 12, The Cochrane Library, April 2013), MEDLINE (1946 to May 2013) and SCOPUS (1823 to May 2013). The online trials registries ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform were systematically searched. The bibliographies of any identified study were searched for further references. We handsearched selected journals and conference proceedings. No language restrictions were imposed.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-randomised controlled trials; double- or single-blinded or unblinded trials; and parallel-group studies. Administration of at least one antiepileptic drug therapy given singly (monotherapy) or in combination (add-on therapy) compared with add-on placebo or no add-on treatment.

DATA COLLECTION AND ANALYSIS

Review authors independently selected trials for inclusion according to predefined criteria, extracted relevant data and evaluated the methodological quality of trials. The following outcomes were assessed: at least 50% seizure reduction, seizure freedom, adverse effects, proportion of dropouts and quality of life. Outcomes were assessed using a Mantel-Haenszel meta-analysis to calculate risk ratio (RR) with 95% confidence intervals (95% CIs).

MAIN RESULTS

No RCTs assessing drugs other than STP were found. Two RCTs evaluating the use of STP (total of 64 children) were included. Both studies were generally at unclear risk of bias. A significantly higher proportion of participants had 50% or greater reduction in seizure frequency in the STP group compared with the placebo group (22/33 vs 2/31; RR 10.40, 95% CI 2.64 to 40.87). A significantly higher proportion of participants achieved seizure freedom in the STP group compared with the placebo group (12/33 vs 1/31; RR 7.93, 95% CI 1.52 to 41.21). No significant difference in the proportion of dropouts was found in the STP group compared with the placebo group (2/33 vs 8/31; RR 0.24, 95% CI 0.06 to 1.03). Only one study explicitly reported the occurrence of side effects; higher proportions of participants were reported to experience side effects in the STP group compared with the placebo group (100% vs 25%; RR 3.73, 95% CI 1.81 to 7.67).

AUTHORS' CONCLUSIONS

Data derived from two small RCTs indicate that STP is significantly better than placebo with regards to 50% or greater reduction in seizure frequency and seizure freedom. Adverse effects occurred more frequently with STP. Further adequately powered studies with long-term follow-up should be conducted to unequivocally establish the long-term efficacy and tolerability of STP in the treatment of SMEI.

Stiripentol exhibits higher anticonvulsant properties in the immature than in the mature rat brain

PURPOSE

After the first positive experimental data in rodents in the early 1970s demonstrating the anticonvulsant effect of stiripentol (STP), in vitro studies showed that STP acts directly on γ-aminobutyric acid A (GABAA ) receptors. Chloride influx is higher when these receptors contain an α3 subunit, leading to the hypothesis that STP might exhibit higher efficacy in the immature brain.

METHODS

We explored this issue by studying the efficacy of STP in P21 and P75 rats using the pentylenetetrazol model of acute seizures or the lithium-pilocarpine status epilepticus model. P21 and adult rats received vehicle, 150, 250, or 350 mg/kg of STP, i.p., 1 h before evaluating the anticonvulsant. We also studied the blood and brain levels of STP as well as the expression and the messenger RNA (mRNA) levels of the α3 subunit of the GABAA receptors at both ages.

KEYS FINDINGS

STP exhibited anticonvulsant properties in both models at both ages, but STP was more effective in P21 than in P75 rats. This was shown by the significant suppression of seizure or status epilepticus occurrence in P21 with 350 mg/kg STP, whereas the same dose had no significant effect at P75. The blood level, brain level, and blood/brain ratio of STP did not explain these differences between the two age groups. Moreover, the higher anticonvulsant properties in the immature brain were not explained by the mRNA level or protein expression of the GABAA α3 subunit at either age.

SIGNIFICANCE

Stiripentol exhibits higher anticonvulsant properties in the immature than in the mature brain. These findings require further investigation because it might lead to new clinical developments.

Diagnosis and management of epileptic encephalopathies in children

Epileptic encephalopathies refer to a group of disorders in which the unremitting epileptic activity contributes to severe cognitive and behavioral impairments above and beyond what might be expected from the underlying pathology alone, and these can worsen over time leading to progressive cerebral dysfunction. Several syndromes have been described based on their electroclinical features (age of onset, seizure type, and EEG pattern). This review briefly describes the clinical evaluation and management of commonly encountered epileptic encephalopathies in children.

The long-term safety of antiepileptic drugs

Antiepileptic drugs (AEDs) are used by millions of people worldwide for the treatment of epilepsy, as well as in many other neurological and psychiatric conditions. They are frequently associated with adverse effects (AEs), which have an impact on the tolerability and success of treatment. Half the people who develop intolerable AEs discontinue treatment early on after initiation, while the majority of people will continue to be exposed to their effects for long periods of time. The long-term safety of AEDs reflects their potential for chronic, cumulative dose effects; rare, but potentially serious late idiosyncratic effects; late, dose-related effects; and delayed, teratogenic or neurodevelopmental effects. These AEs can affect every body system and are usually insidious. With the exception of delayed effects, most other late or chronic AEs are reversible. To date, there is no clear evidence of a carcinogenic effect of AEDs in humans. While physicians are aware of the long-term AEs of old AEDs (the traditional liver enzyme-inducing AEDs and valproate), information about AEs of new AEDs (such as lamotrigine, levetiracetam, oxcarbazepine, topiramate or zonisamide), particularly of their teratogenic effects, has emerged over the years. Sporadic publications have raised issues about AEs of the newer AEDs eslicarbazepine, retigabine, rufinamide, lacosamide and perampanel but their long-term safety profiles may take years to be fully appreciated. Physicians should not only be aware of the late and chronic AEs of AEDs but should systematically enquire and screen for these according to the individual AED AE profile. Care should be taken for individuals with comorbid conditions that may render them more susceptible to specific AEs. Prevention and appropriate management of long-term AED AEs is expected to improve adherence to treatment, quality of life and control of epilepsy.

Synergistic GABA-enhancing therapy against seizures in a mouse model of Dravet syndrome

Seizures remain uncontrolled in 30% of patients with epilepsy, even with concurrent use of multiple drugs, and uncontrolled seizures result in increased morbidity and mortality. An extreme example is Dravet syndrome (DS), an infantile-onset severe epilepsy caused by heterozygous loss of function mutations in SCN1A, the gene encoding the brain type-I voltage-gated sodium channel NaV1.1. Studies in Scn1a heterozygous knockout mice demonstrate reduced excitability of GABAergic interneurons, suggesting that enhancement of GABA signaling may improve seizure control and comorbidities. We studied the efficacy of two GABA-enhancing drugs, clonazepam and tiagabine, alone and in combination, against thermally evoked myoclonic and generalized tonic-clonic seizures. Clonazepam, a positive allosteric modulator of GABA-A receptors, protected against myoclonic and generalized tonic-clonic seizures. Tiagabine, a presynaptic GABA reuptake inhibitor, was protective against generalized tonic-clonic seizures but only minimally protective against myoclonic seizures and enhanced myoclonic seizure susceptibility at high doses. Combined therapy with clonazepam and tiagabine was synergistic against generalized tonic-clonic seizures but was additive against myoclonic seizures. Toxicity determined by rotorod testing was additive for combination therapy. The synergistic actions of clonazepam and tiagabine gave enhanced seizure protection and reduced toxicity, suggesting that combination therapy may be well tolerated and effective for seizures in DS.

A revisited strategy for antiepileptic drug development in children: designing an initial exploratory step

BACKGROUND

Randomized controlled trials (RCTs) in refractory paediatric epilepsy usually involve the two main types of epilepsy shared by children and adults, focal epilepsy and Lennox-Gastaut syndrome (LGS). Most other epilepsy syndromes, specifically paediatric, are excluded from drug development. In order to identify among them the candidate(s) for dedicated RCTs with a new drug, the European Medicine Agency (EMA) recently recommended proceeding in two steps: (1) an exploratory (prospective-observational) trial (POT) including a large variety of paediatric epilepsy syndromes and (2) a subsequent RCT in each of those that disclose a signal for possible efficacy.

OBJECTIVE

Our objective was to address the three following issues that have not been addressed by the EMA: (1) to determine a minimal threshold for this signal; (2) to establish a list of epilepsies to evaluate; and (3) to estimate the number of patients to include in such POTs.

METHODS

We extensively reviewed the POTs (including various syndromes) and RCTs reported in paediatric patients with uncontrolled epilepsy using MEDLINE (from 1990 to 2011) and the Cochrane library. We determined the threshold as the lowest percentage of responders observed in a POT with a positive corresponding RCT. The syndromes that reached this threshold in a POT were those to evaluate in an RCT. The minimal number of patients to include for each syndrome for a POT with a new antiepileptic drug was estimated in order to reach at least this threshold of responders with a 95 % confidence interval.

RESULTS

We found the minimal responder threshold to be 25 %. We identified eight epilepsy types/syndromes reaching this threshold and estimated for each of them the minimal sample needed: refractory focal epilepsy (n = 40), Lennox-Gastaut syndrome (n = 32), infantile spasms (n = 50), Dravet syndrome (n = 32), childhood absence epilepsy (n = 12), other symptomatic generalized epilepsy (n = 38), epileptic encephalopathy with continuous spikes and waves during sleep (n = 7) and epilepsy with myoclonic-astatic seizures (n = 4) [the two last samples may be underestimated due to the lack of RCTs in these conditions].

CONCLUSION

Among the eight epilepsy types/syndromes that we recommend to systematically include in exploratory trials using the POT procedure, we assume that, for the minimal sample given above, a responder threshold of 25 % will provide a reliable efficacy signal, to be confirmed by a dedicated RCT. This strategy should avoid missing new therapeutic possibilities for children with epilepsy and reduce the off-label use of drugs in paediatric neurology.

Neurogenetic disorders and treatment of associated seizures

Seizures are a frequent complication associated with several neurogenetic disorders. Antiepileptic medications remain the mainstay of treatment in these patients. We summarized the available data associated with various antiepileptic therapies used to treat patients with neurogenetic disorders who experienced recurrent seizures. A MEDLINE search was conducted to identify articles and abstracts describing the use of antiepileptic therapy for the treatment of various neurogenetic syndromes. Of all the neurogenetic syndromes, only autism spectrum disorders, Angelman syndrome, Rett syndrome, Dravet syndrome, and tuberous sclerosis complex were identified as having sufficient published information to evaluate therapy. Some efficacy trends were identified, including frequent successes with valproic acid with clonazepam for epilepsy with Angelman syndrome; valproic acid, stiripentol, and clobazam (triple combination therapy) for epilepsy with Dravet syndrome; and vigabatrin for infantile spasms associated with tuberous sclerosis complex. Due to a paucity of information regarding the mechanisms by which seizures are generated in the various disorders, approach to seizure control is primarily based on clinical experience and a limited amount of study data exploring patient outcomes. Although exposure of the developing brain to antiepileptic medications is of some concern, the control of epileptic activity is an important undertaking in these individuals, as the severity of eventual developmental delay often appears to correlate with the severity of seizures. As such, early aggressive therapy is warranted.

Malignant migrating partial seizures of infancy controlled by stiripentol and clonazepam

The syndrome of malignant migrating partial seizures of infancy (MMPSI) is characterized by early onset of multiple seizure types and overall poor prognosis. Seizures are markedly drug resistant and few reports have suggested the efficacy of some antiepileptic drugs. We report one case of MMPSI in which prolonged seizure control is obtained with an association of clonazepam, levetiracetam and stiripentol, confirming thus the possibility of complete sustained seizure control in this epileptic syndrome. Of more than 60 cases reported to date, ours is the forth in which sustained complete control of seizures was obtained.

Treatment strategies

There has been important progress in the identification of antiepileptic compounds and their indications in children over the past 15 years: their number has doubled and specific pediatric trials are being performed to document their effect according to seizures and syndromes as well as their tolerability in pediatrics. The improved understanding of pharmacokinetics and drug-drug interactions has helped to optimize treatment. Specific issues specific of infants have also been studied although new antiepileptic drugs are still dramatically lacking for this age group. Before reaching a syndromic diagnosis, the choice of a first- line agent goes to compounds with the largest range of efficacy and least identified risks. Subsequent choices are mainly based on the epilepsy syndrome and seizure type in addition to good clinical practice to determine dose, adverse effect profile, risk of aggravating seizures and drug interactions, clinician's experience, cultural habits, and availability of drugs. If there are several options, preference is given to the compound that exhibits the best risk/benefit ratio, or the most rapid titration when seizure frequency is the major issue. For new antiepileptic compounds, price is often a limiting factor in countries with poor insurance coverage. Third generation anti-epileptic drugs are emerging which also seem to be promising.

Stiripentol : in severe myoclonic epilepsy of infancy (dravet syndrome)

Stiripentol is an anticonvulsant used as adjunctive therapy with valproate and clobazam in the management of patients with severe myoclonic epilepsy of infancy (SMEI; Dravet syndrome), a rare form of epilepsy that develops in the first year of life and is subsequently associated with significant morbidity and mortality. Results of a randomized, double-blind trial, in which patients (≥3 years of age) whose SMEI was inadequately controlled with valproate and clobazam received adjunctive therapy with stiripentol or placebo for 2 months, showed a significantly higher response rate in the stiripentol group compared with the placebo group (71 % vs. 5 %; p < 0.0001; primary endpoint). Responders were defined as those patients who experienced a ≥50 % reduction in clonic or tonic-clonic seizure frequency during the second month of the double-blind period compared with baseline. Almost half of the stiripentol recipients were seizure free during this period compared with none in the placebo group. Stiripentol was also statistically superior to placebo for secondary efficacy outcomes in the randomized controlled trial, which included the median number of seizures during the second month of the double-blind period and the mean percentage change from baseline in seizure frequency. These results are supported by efficacy data from other studies in patients with SMEI treated with stiripentol as adjunctive therapy, including a long-term retrospective analysis, prospectively conducted open-label studies and a meta-analysis. Drowsiness, loss of appetite and weight loss are the most frequently reported adverse events with stiripentol, and the drug inhibits various cytochrome P450 isoenzymes, potentially leading to clinically significant drug interactions. Stiripentol is an important addition to the limited treatment options available for the management of patients with SMEI.

Stiripentol: an example of antiepileptic drug development in childhood epilepsies

The efficacy of stiripentol (STP) in Dravet Syndrome (DS) was discovered first in an exploratory study in pediatric pharmacoresistant epilepsies. This efficacy signal, used as a proof of concept, led to - two independent multicenter randomized, double-blind, placebo-controlled trials in DS patients: STICLO-France and STICLO-Italy. In adjunction to valproate and clobazam, STP demonstrated marked efficacy and these trials became the basis for the registration of STP as an orphan drug for DS. Although STP had previously shown antiepileptic activity, since it inhibits cytochromes P450, the increased plasma levels of clobazam (CLB), norclobazam (NCLB), and NCLB/CLB ratio reported in STICLO studies brought into question the activity of STP per se. Recent pharmacological studies demonstrated that (i) STP is a direct allosteric modulator of the GABA receptors at a site distinct from benzodiazepines; (ii) STP and CLB/NCLB act independently at GABA(A) receptors; (iii) their combination increases the maximum response beyond that of either drug alone. All these effects are independent of considerations of changes in metabolism. Some responders in STICLO studies failed to display any increase of plasmatic concentrations of NCLB/CLB ratio as STP could not inhibit CYP2C19 because of its inhibition by progabide or due to an inactivating CYP polymorphism. The responder rate proved to be in the same range whether the NCLB/CLB ratio increased or not. These analyses confirmed that the effects of STP cannot result from a simple pharmacokinetic interaction. We propose that the success of STP should serve as a model for AED development in rare pediatric epileptic syndromes.

Efficacy of stiripentol in hyperthermia-induced seizures in a mouse model of Dravet syndrome

PURPOSE

We previously reported a mutant mouse carrying a severe myoclonic epilepsy in infancy (SMEI) mutation in Scn1a. In this study, we examined the susceptibility to hyperthermia-induced seizures of heterozygous Scn1a mutant mice (Scn1a(RX/+)) and wild-type (Scn1a(+/+) ) mice. Then we assessed the efficacy of stiripentol (STP) monotherapy versus STP and clobazam (CLB) combination therapy to prevent hyperthermia-induced seizures in Scn1a(RX/+) mice.

METHODS

The seizure-inducing body temperatures in Scn1a(RX/+) mice and age-matched Scn1a(+/+) mice were compared in three age groups (1 month, 3-5 months, > 6 months). Then STP, CLB, or STP + CLB was administered intraperitoneally to Scn1a(RX/+) mice of two age groups (p1M, aged 1 month; p5M, aged 5-10 months). The efficacy of medications was assessed by comparing the seizure-inducing body temperature and the duration of seizures.

KEY FINDINGS

The seizure-inducing body temperature was significantly lower in Scn1a(RX/+) than in Scn1a(+/+) mice for all age groups (p < 0.01). The seizure-inducing body temperature was significantly elevated after administration of STP in p1M (p < 0.05) but not in p5M (p > 0.05), and it was significantly elevated after administration of CLB in both age groups (p < 0.05). The seizure-inducing body temperature was significantly higher after administration of STP + CLB than after administration of CLB in p5M (p < 0.05).

SIGNIFICANCE

Scn1a (RX/+) mice have increased susceptibility to hyperthermia-induced seizure in all age groups. STP monotherapy is effective in preventing hyperthermia-induced seizures in Scn1a(RX/+) mice aged 1 month, but not in those aged 5 months and older. When used in combination therapy with CLB, STP inhibits the metabolism of CLB and probably synergistically enhances the anticonvulsant effect in mice aged 1 month.

Migrating focal seizures during infancy: a case report and pathologic study

Migrating focal seizures in infancy are an unusual and often overlooked epilepsy syndrome, with onset before age 6 months, in which nearly continuous seizures involve multiple, independent areas of both hemispheres with an arrest of psychomotor development. We describe a patient with migrating focal seizures in infancy whose seizures began at age 45 days. The seizures were refractory to common antiepileptic drugs. At age 6 months, the infant received potassium bromide and became almost seizure-free. The infant developed severe neurologic impairment, with marked axial hypotonia and an absence of visual contact and head control. At age 8 months, the child suddenly died. Pathologic findings included multiple malformations of cortical development, polymicrogyria, and focal cortical dysplasia associated with hippocampal sclerosis.

Pharmacologic treatment of intractable epilepsy in children: a syndrome-based approach

The successful pharmacologic treatment of intractable childhood epilepsy is predicated upon an accurate classification of the epilepsy syndrome. The selection of an antiepileptic drug is facilitated by the knowledge of syndrome-specific efficacy, the anticipation of potential side effects, and a careful risk-benefit assessment tailored to each patient. As such, the identification of comorbidities and careful monitoring for treatment-emergent adverse events, especially cognitive and behavioral effects, is of utmost importance. Especially in refractory cases, polypharmacy may increase the likelihood of side effects, but carefully chosen combinations can result in synergistic benefit. For most epilepsy syndromes, newer antiepileptic drugs typically yield equivalent efficacy and superior tolerability. Nevertheless, continued research is needed to further contrast the syndrome-specific efficacy and tolerability of available drugs and to foster the development of new agents with superior efficacy and side effect profiles.

Current therapeutic procedures in Dravet syndrome

Dravet syndrome is a highly pharmaco-resistant form of epilepsy. Valproate and benzodiazepines are the first-line treatment but are usually insufficient therapeutic options. Lamotrigine, carbamazepine and high doses of intravenous phenobarbital can aggravate seizures and should be avoided. Topiramate, levetiracetam, bromide and ketogenic diet also provide substantial efficacy as adjunctive therapy and procedures. Stiripentol is the only new drug to demonstrate efficacy when combined with valproate and clobazam, as shown in two independent double-blind controlled trials dedicated to Dravet children. In order to avoid side effects (mainly loss of appetite and loss of weight) resulting from the inhibition of cytochromes P450 by stiripentol, the prescribed doses of valproate and clobazam should be reduced. Stiripentol has a proper antiepileptic effect and enhances GABAergic neurotransmission by acting on the alpha-3 subunit of GABA(A) receptors. Stiripentol was approved as an orphan drug in Europe in 2007 for adjunctive therapy in Dravet syndrome. More than 500 Dravet patients have currently been satisfactorily treated and recent experiments in Japan have confirmed stiripentol's benefit. In practice, valproate should be initiated at the first onset of complicated febrile seizure in Dravet patients. Relapses justify the addition of clobazam and stiripentol when available. Topiramate and a ketogenic diet are alternatives in pharmaco-resistant cases.

Interactions between modulators of the GABA(A) receptor: Stiripentol and benzodiazepines

Many patients with refractory epilepsy are treated with polytherapy, and nearly 15% of epilepsy patients receive two or more anti-convulsant agents. The anti-convulsant stiripentol is used as an add-on treatment for the childhood epilepsy syndrome known as severe myoclonic epilepsy in infancy (Dravet syndrome). Stiripentol has multiple mechanisms of action, both enhancing GABA(A) receptors and reducing activity of metabolic enzymes that break down other drugs. Stiripentol is typically co-administered with other anti-convulsants such as benzodiazepines which also act through GABA(A) receptor modulation. Stiripentol slows the metabolism of some of these drugs through inhibition of a variety of cytochrome P450 enzymes, but could also influence their effects on GABAergic neurotransmission. Is it rational to co-administer drugs which can act through the same target? To examine the potential interaction between these modulators, we transiently transfected HEK-293T cells to produce α3β3γ2L or α3β3δ recombinant GABA(A) receptors. Using whole-cell patch clamp recordings, we measured the response to each benzodiazepine alone and in combination with a maximally effective concentration of stiripentol. We compared the responses to four different benzodiazepines: diazepam, clonazepam, clobazam and norclobazam. In all cases we found that these modulators were equally effective in the presence and absence of stiripentol. The δ-containing receptors were insensitive to modulation by the benzodiazepines, which did not affect potentiation by stiripentol. These data suggest that stiripentol and the benzodiazepines act independently at GABA(A) receptors and that polytherapy could be expected to increase the maximum effect beyond either drug alone, even without consideration of changes in metabolism.

Interactions of stiripentol with clobazam and valproate in the mouse maximal electroshock-induced seizure model

The aim of this study was to characterize the anticonvulsant effects of stiripentol (STP) in combination with clobazam [CLB], and valproate [VPA]) in the mouse maximal electroshock (MES)-induced seizure model using the type I isobolographic analysis for parallel and non-parallel dose-response relationship curves (DRRCs). Potential adverse-effect profiles of interactions of STP with CLB and VPA at the fixed-ratio of 1:1 in the MES test with respect to motor performance, long-term memory and skeletal muscular strength were measured along with total brain antiepileptic drug concentrations. In the mouse MES model, STP administered singly had its DRRC non-parallel to that for CLB and, simultaneously, parallel to that for VPA. With type I isobolography for parallel DRRCs, the combinations of STP with VPA at three fixed-ratios of 1:3, 1:1 and 3:1 exerted sub-additive (antagonistic) interaction. Isobolography for non-parallel DRRCs revealed that the combination of STP with CLB at the fixed-ratio of 1:1 produced additive interaction. For all combinations, neither motor coordination, long-term memory nor muscular strength was affected. Total brain antiepileptic drug concentrations revealed bi-direction changes with the most profound being an 18.6-fold increase in CLB by STP and a 2.3-fold increase in STP by VPA. In conclusion, the additive interaction between STP and CLB was associated with a concurrent pharmacokinetic interaction and these data may explain the clinical efficacy seen with this combination. In contrast, the antagonism between STP and VPA was surprising since synergism is observed clinically.

Pharmacological management of epilepsy: recent advances and future prospects

There is still a need for new antiepileptic drugs (AEDs) as the clinical efficacy, tolerability, toxicity or pharmacokinetic properties of existing AEDs may not be satisfactory. One new AED has recently been approved (rufinamide in 2007) and six others are in late-stage development (phase III and onwards) [brivaracetam, carisbamate, eslicarbazepine, lacosamide, retigabine and stiripentol]. The purpose of this review is to provide updated data on proposed mechanisms of action, efficacy and tolerability on these new AEDs, and to discuss the rationale for their development and possible advantages compared with existing treatment, based on recent publications and MEDLINE searches.Rufinamide, brivaracetam and stiripentol have been given the status of orphan drugs. Rufinamide was approved in Europe in 2007 for the use in Lennox-Gastaut syndrome. Brivaracetam has gained orphan status for development in progressive and symptomatic myoclonic seizures in Europe and the US, respectively. Stiripentol has gained orphan status in children with Dravet's syndrome and pharmaco-resistant epilepsy. All of these drugs demonstrate efficacy as adjunctive therapy in partial seizures. Three of the drugs are derivatives of existing AEDs: brivaracetam is a derivative of levetiracetam with improved affinity for the target molecule; carisbamate is a derivative of felbamate with improved tolerability; and eslicarbazepine is a derivative of carbamazepine with less interaction potential and no auto-induction. Lacosamide, retigabine, rufinamide and stiripentol are new compounds, unrelated to other AEDs.Further investigation and development of new broad-spectrum drugs is important for improved treatment of patients with epilepsy and other neurological and psychiatric disorders.

Juvenile myoclonic epilepsy: epidemiology, pathophysiology, and management

Juvenile myoclonic epilepsy (JME) is a common epilepsy syndrome that begins most frequently in the early teenage years. It is officially classified as a type of idiopathic generalized epilepsy and is often under-recognized or misdiagnosed. This syndrome has a strong genetic component with multiple gene mutations being associated with the clinical presentation. Based upon genetic associations, there may be multiple pathophysiologic mechanisms for the disorder; the pathophysiology has not been clearly defined. A diagnosis of JME is made using the clinical history and EEG findings. Valproic acid is the primary antiepileptic drug (AED) used for JME, but some newer AEDs may be effective alternatives. Selection of an appropriate AED is essential to the proper management of JME, because of the possibility of exacerbation of seizures by some AEDs and the adverse effect profiles of effective drugs. It is important for clinicians to understand JME to correctly diagnose and manage patients with this syndrome.

Stiripentol

Stiripentol (STP) is a new antiepileptic compound made by Biocodex. It recently proved to increase the GABAergic transmission in vitro in an experimental model of immature rat. Clinical studies were based on the fact that STP also acts as an inhibitor of CYP3A4, CYP1A2, and CYP2C19 in vivo in epileptic patients. Whereas the studies in adult patients were disappointing, the trials conducted in pediatric populations demonstrated a specific efficacy of STP in severe myoclonic epilepsy in infancy, Dravet syndrome, when combined with valproate and clobazam. Based on these results, STP was granted orphan drug status in the European Union for the treatment of Dravet syndrome. The French experience in compassionate use suggests that STP might also be of benefit when combined with carbamazepine in pediatric patients with pharmacoresistant partial epilepsy. The interactions of STP with a large number of drugs need to be carefully taken into account, with doses of the combined antiepileptic drugs adjusted to improve the tolerability of the therapeutic association.

Progress report on new antiepileptic drugs: a summary of the Eigth Eilat Conference (EILAT VIII)

The Eigth Eilat Conference on New Antiepileptic Drugs (AEDs)-EILAT VII, took place in Sitges, Barcelona from the 10th to 14th September, 2006. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference, whose main themes included a focus on status epilepticus (epidemiology, current and future treatments), evidence-based treatment guidelines and the potential of neurostimulation in refractory epilepsy. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on marketed AEDs introduced since 1989. This article summarizes the information presented on drugs in development, including brivaracetam, eslicarbazepine acetate (BIA-2-093), fluorofelbamate, ganaxolone, huperzine, lacosamide, retigabine, rufinamide, seletracetam, stiripentol, talampanel, valrocemide, JZP-4, NS1209, PID and RWJ-333369. Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine and new extended release oxcarbazepine formulations, pregabalin, tiagabine, topiramate, vigabatrin, zonisamide and new extended release valproic acid formulations, and the antiepileptic vagal stimulator device are also presented.

Characterization of the Anticonvulsant, Behavioral and Pharmacokinetic Interaction Profiles of Stiripentol in Combination with Clonazepam, Ethosuximide, Phenobarbital, and Valproate Using Isobolographic Analysis

PURPOSE

Isobolographic analysis was used to characterize the interactions between stiripentol (STP) and clonazepam (CZP), ethosuximide (ETS), phenobarbital (PB), and valproate (VPA) in suppressing pentylenetetrazole (PTZ)-induced clonic seizures in mice.

METHODS

The anticonvulsant and acute adverse (neurotoxic) effects of STP in combination with the various conventional antiepileptic drugs (AEDs), at fixed ratios of 1:3, 1:1, and 3:1, were evaluated in the PTZ and chimney tests in mice using the isobolographic analysis. Additionally, protective indices (PI) and benefit indices (BI) were calculated to identify their pharmacological profiles so that a ranking in relation to advantageous combination could be established. Moreover, adverse-effect paradigms were determined by use of the step-through passive avoidance task (long-term memory), threshold for the first pain reaction, grip-strength test (neuromuscular tone), and the hot plate test (acute thermal pain). Brain AED concentrations were also measured so as to ascertain any pharmacokinetic contribution to the pharmacodynamic interactions.

RESULTS

All AED combinations comprising of STP and CZP, ETS, PB, and VPA (at the fixed ratios of 1:3, 1:1 and 3:1) were additive in terms of clonic seizure suppression in the PTZ test. However, these interactions were complicated by changes in brain AED concentrations consequent to pharmacokinetic interactions. Thus STP significantly increased total brain ETS and PB concentrations, and decreased VPA concentrations, but was without effect on CZP concentrations. In contrast, PB significantly decreased and VPA increased total brain STP concentrations while CZP and ETS were without effect. Furthermore, while isobolographic analysis revealed that STP and CZP in combination, at the fixed ratios of 1:1 and 3:1, were supraadditive (synergistic; p < 0.05), the combinations of STP with CZP (1:3), ETS, PB, or VPA (at all fixed ratios of 1:3, 1:1, and 3:1) were barely additivity in terms of acute neurotoxic adverse effects in the chimney test. Additionally, none of the examined combinations of STP with conventional AEDs (CZP, ETS, PB, VPA--at their median effective doses from the PTZ-test) affected long-term memory, threshold for the first pain reaction, neuromuscular tone, and acute thermal pain.

CONCLUSIONS

Based on BI values, the combination of STP with PB at the fixed ratio of 1:3 appears to be a particularly favourable combination. In contrast, STP and CZP or ETS (at the fixed ratios of 1:1 and 3:1) were unfavorable combinations. However, these conclusions are confounded by the fact that STP is associated with significant pharmacokinetic interactions. The remaining combinations of STP with PB (1:1 and 3:1), CZP (1:3), ETS (1:3), and VPA (at all fixed ratios of 1:3, 1:1, and 3:1) do not appear to be potential favorable AED combinations.

Experimental and clinical evidence for loss of effect (tolerance) during prolonged treatment with antiepileptic drugs

Development of tolerance (i.e., the reduction in response to a drug after repeated administration) is an adaptive response of the body to prolonged exposure to the drug, and tolerance to antiepileptic drugs (AEDs) is no exception. Tolerance develops to some drug effects much more rapidly than to others. The extent of tolerance depends on the drug and individual (genetic?) factors. Tolerance may lead to attenuation of side effects but also to loss of efficacy of AEDs and is reversible after discontinuation of drug treatment. Different experimental approaches are used to study tolerance in laboratory animals. Development of tolerance depends on the experimental model, drug, drug dosage, and duration of treatment, so that a battery of experimental protocols is needed to evaluate fully whether tolerance to effect occurs. Two major types of tolerance are known. Pharmacokinetic (metabolic) tolerance, due to induction of AED-metabolizing enzymes has been shown for most first-generation AEDs, and is easy to overcome by increasing dosage. Pharmacodynamic (functional) tolerance is due to "adaptation" of AED targets (e.g., by loss of receptor sensitivity) and has been shown experimentally for all AEDs that lose activity during prolonged treatment. Functional tolerance may lead to complete loss of AED activity and cross-tolerance to other AEDs. Convincing experimental evidence indicates that almost all first-, second-, and third-generation AEDs lose their antiepileptic activity during prolonged treatment, although to a different extent. Because of diverse confounding factors, detecting tolerance in patients with epilepsy is more difficult but can be done with careful assessment of decline during long-term individual patient response. After excluding confounding factors, tolerance to antiepileptic effect for most modern and old AEDs can be shown in small subgroups of responders by assessing individual or group response. Development of tolerance to the antiepileptic activity of an AED may be an important reason for failure of drug treatment. Knowledge of tolerance to AED effects as a mechanism of drug resistance in previous responders is important for patients, physicians, and scientists.

Biphasic characteristic of interactions between stiripentol and carbamazepine in the mouse maximal electroshock-induced seizure model: a three-dimensional isobolographic analysis

The anticonvulsant effects produced by stiripentol (STP), carbamazepine (CBZ), and their combination in the maximal electroshock (MES)-induced seizures in mice were investigated using three-dimensional (3D) isobolographic analysis. With 3D isobolography, the combinations of both drugs at the fixed-ratios of 1:3, 1:1, and 3:1 for 16%, 50% and 84% antiseizure effects, respectively, were examined in order to evaluate the preclinical characteristics of the interactions between STP and CBZ. Additionally, to characterize precisely the types of interactions observed in the MES test, free plasma and total brain CBZ concentrations were estimated for all fixed-ratios tested. The 3D isobolographic analysis showed that STP and CBZ combined at the fixed-ratio of 1:3 produced supra-additive (synergistic) interactions in the MES test for the anticonvulsant effects ranging between 16% and 84%. In contrast, the combination of STP with CBZ at the fixed-ratio of 3:1 exerted sub-additive (antagonistic) interactions in 3D isobolography for all antiseizure effects examined in the MES test. Only the combination of STP and CBZ at the fixed-ratio of 1:1 was additive for the investigated effects (16%, 50% and 84%) in 3D isobolography. Pharmacokinetic evaluation of CBZ concentrations revealed that STP increased both free plasma and total brain CBZ concentrations for all fixed-ratio combinations tested (1:3, 1:1 and 3:1). In conclusion, the 3D isobolographic findings suggest that the combination of STP with CBZ exerted biphasic characteristics of interactions in the MES test, despite the pharmacokinetic increase in CBZ content in plasma and brains of experimental animals.

Stiripentol in childhood partial epilepsy: randomized placebo-controlled trial with enrichment and withdrawal design

Stiripentol, a new antiepileptic drug inhibiting cytochrome P450-enzymes, suggested some efficacy when combined with carbamazepine in an open trial in refractory partial epilepsy of childhood. Our objective was to test these results in a placebo-controlled trial. To limit the number of patients included, we used an enrichment and withdrawal design. Among the 67 children entered in a 4-month open add-on stiripentol study following a 1-month single-blind placebo baseline, the 32 responders were randomized for 2 months either to continue stiripentol (n = 17) or to withdraw to placebo (n = 15). If seizures increased by at least 50% after randomization compared with baseline, the patients dropped out (primary end point): there were six patients on stiripentol and eight patients on placebo (not significant). However, a decrease in seizure frequency compared with baseline (secondary end point) was greater on stiripentol (-75%) than on placebo (-22%) (P < .025). Twelve patients experienced at least one adverse event on stiripentol (71%) compared with four patients on placebo (27%); none were reported as severe. The combination of stiripentol and carbamazepine proved to reduce seizure frequency in children with refractory partial epilepsy, although it failed to show a significant impact according to the escape criteria selected as the primary end point in the present study, for ethical reasons.

Stiripentol, a Putative Antiepileptic Drug, Enhances the Duration of Opening of GABAA-Receptor Channels

PURPOSE

Stiripentol (STP) is currently an efficient drug for add-on therapy in infantile epilepsies because it improves the efficacy of antiepileptic drugs (AEDs) through its potent inhibition of liver cytochromes P450. In addition, STP directly reduces seizures in several animal models of epilepsy, suggesting that it might also have anticonvulsive effects of its own. However, its underlying mechanisms of action are unknown.

METHODS

We examined the interactions of STP with gamma-aminobutyric acid (GABA) transmission by using patch-clamp methods in CA3 pyramidal neurons in the neonatal rat.

RESULTS

STP markedly increased miniature inhibitory postsynaptic current (mIPSC) decay-time constant in a concentration-dependent manner. The prolongation of mIPSC duration does not result from an interaction with GABA transporters because it persisted in the presence of GAT-1 inhibitors (SKF-89976A and NO-711). An interaction with benzodiazepine or neurosteroid binding sites also was excluded because STP-mediated increase of decay time was still observed when these sites were initially saturated (by clobazam, zolpidem, or pregnanolone) or blocked (by flumazenil or dehydroepiandrosterone sulfate), respectively. In contrast, saturating barbiturate sites with pentobarbital clearly occluded this effect of STP, suggesting that STP and barbiturates interact at the same locus. This was directly confirmed by using outside-out patches, because STP increased the duration and not the frequency of opening of GABAA channels.

CONCLUSIONS

At clinically relevant concentrations, STP enhances central GABA transmission through a barbiturate-like effect, suggesting that STP should possess an antiepileptic effect by itself.

In vitro and in vivo inhibitory effect of stiripentol on clobazam metabolism

A metabolic interaction between stiripentol (STP), an anticonvulsant agent that inhibits the activity of several cytochromes P450 (P450s), and clobazam (CLB), a 1,5-benzodiazepine, used in association with STP in severe myoclonic epilepsy in infancy was observed in vivo. This interaction was characterized in vitro using cDNA-expressed CYP3A4 and CYP2C19 (main P450 involved in CLB metabolism) to calculate K(i) and IC(50) of stiripentol in comparison with ketoconazole (CYP3A4 inhibitor) and omeprazole (CYP2C19 inhibitor). STP inhibited N-demethylation of CLB to N-desmethylclobazam (NCLB) mediated by CYP3A4 (noncompetitively) and CYP2C19 (competitively) with K(i) = 1.59 +/- 0.07 and 0.516 +/- 0.065 microM and IC(50) = 1.58 microM [95% confidence interval (CI95%) = 1.20-2.08] and 3.29 microM (CI95% = 1.87-5.79), respectively. STP inhibited also more strongly the 4'-hydroxylation of NCLB to 4'-hydroxy-N-desmethylclobazam by CYP2C19 [competitive interaction with K(i) = 0.139 +/- 0.025 microM and IC(50) = 0.276 microM (CI95% = 0.206-0.371)]. The inhibitory effect of STP on CLB demethylation by CYP3A4 was much weaker than that of ketoconazole [IC(50) = 0.023 microM (CI95% = 0.016-0.033)], whereas its effect on NCLB hydroxylation by CYP2C19 was much higher than that of omeprazole [IC(50) = 2.99 microM (CI95% = 2.11-4.24)]. The major in vitro inhibitory effect of STP on CLB metabolism and mostly on NCLB biotransformation is consistent with the changes in vivo in CLB and NCLB plasma concentrations in children treated by the association CLB/STP.

Stiripentol

Stiripentol (STP) is a new antiepileptic compound produced by Biocodex. It is not structurally related to any of the other currently marketed antiepileptic products as it belongs to the group of aromatic allylic alcohols. It has recently been proved to increase GABAergic transmission in experimental models. It has been studied and used in France and Canada for > 10 years, but its clinical development was delayed due to the inhibitory effect of STP on hepatic cytochrome P450 (CYP). Clinical studies were based on the fact that STP also acts as an inhibitor of CYP3A4, CYP1A2 and CYP2C19 in vivo in epileptic patients. Although the studies in adult patients were disappointing, the trials conducted in paediatric populations demonstrated a specific efficacy of STP in a severe form of early childhood epilepsy, Dravet syndrome (severe myoclonic epilepsy in infancy), when combined with valproate and clobazam. Based on these results, STP was granted orphan drug status in the European Union for the treatment of Dravet syndrome. The French experience in compassionate use suggests that STP might also be of benefit when combined with carbamazepine in paediatric patients with pharmacoresistant partial epilepsy. Nevertheless, two controlled adjunctive-therapy trials were recently completed in paediatric populations with epilepsy. The interactions of STP with a large number of drugs need to be carefully taken into account by adjusting the doses of the combined antiepileptic drugs in order to improve the tolerability of the therapeutic association.

Progress report on new antiepileptic drugs: a summary of the Seventh Eilat Conference (EILAT VII)

The Seventh Eilat Conference on New Antiepileptic Drugs (AEDs) (EILAT VII) took place in Villasimius, Sardinia, Italy from the 9th to 13th May 2004. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference,whose main themes included advances in pathophysiology of drug resistance, new AEDs in pediatric epilepsy syndromes, modes of AED action and spectrum of adverse effects and a re-appraisal of comparative responses to AED combinations. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on second-generation AEDs. This article summarizes the information presented on drugs in development, including atipamezole, BIA-2-093, fluorofelbamate, NPS 1776, pregabalin, retigabine, safinamide, SPM 927, stiripentol, talampanel,ucb 34714 and valrocemide (TV 1901). Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine,topiramate, vigabatrin, zonisamide, new oral and parenteral formulations of valproic acid and SPM 927 and the antiepileptic vagal stimulator device are also presented.

Severe myoclonic epilepsy in infancy: toward an optimal treatment

Severe myoclonic epilepsy in infancy, or Dravet syndrome, is one of the catastrophic epilepsy syndromes. In the past, treatment was mainly based on valproate and phenobarbital. Recently, some of the new antiepilepsy drugs, such as topiramate and stiripentol, have been shown to be promising in the treatment of this epilepsy syndrome. The treatment regimen of 12 children with Dravet syndrome and proven mutations in the alpha subunit of the sodium channel SCN1A is reported here. Five patients on the "traditional" treatment regimen are compared with seven children on an "optimal" treatment regimen based on a combination of valproate and topiramate. With respect to the literature and our own experience, we propose guidelines for "optimal" treatment of children with severe myoclonic epilepsy in infancy. This includes prevention of hyperthermia, rigorous treatment of fever, avoiding stressful situations, maintenance treatment based on a combination of only two antiepilepsy drugs (ie, valproate and topiramate), and a strict acute seizure treatment based on benzodiazepines. To prevent long-lasting periods of status epilepticus, this acute seizure treatment must be taught to parents and caregivers.

Inhibitory effect of stiripentol on carbamazepine and saquinavir metabolism in human

AIMS

To characterize the in vitro and in vivo inhibitory effect of stiripentol, a new anticonvulsant, on the metabolism of carbamazepine and saquinavir, which are substrates of CYP3A4.

METHODS

Human liver microsomes and cDNA-expressed CYP enzymes were used for the in vitro experiments. Pharmacokinetic data from epileptic children and healthy adults were used for the carbamazepine and saquinavir in vivo studies, respectively.

RESULTS

Carbamazepine biotransformation to its 10,11-epoxide by human liver microsomes (Vmax = 10.3 nmol min(-1) nmol(-1) P450, apparent Km = 362 microm), cDNA-expressed CYP3A4 (Vmax = 1.17 nmol min(-1) nmol(-1) P450, apparent Km = 119 microm) and CYP2C8 (Vmax = 0.669 nmol min(-1) nmol(-1) P450, apparent Km = 757 microm) was inhibited by stiripentol (IC50 14, 5.1, 37 microM and apparent Ki 3.7, 2.5, 35 microm, respectively). Saquinavir biotransformation to its major metabolite M7 by human liver microsomes (Vmax = 5.7 nmol min(-1) nmol(-1) P450, apparent Km = 0.79 microm) was inhibited by stiripentol (IC50 163 microM, apparent Ki 86 microm). In epileptic children treated with carbamazepine and stiripentol, the plasma concentration ratio of carbamazepine epoxide/carbamazepine was decreased by 65%. The in vivo apparent Ki for stiripentol ranged from 10.5 to 41.4 microm. The pharmacokinetics of saquinavir was not modified by stiripentol in healthy adults. The 95% confidence intervals for the difference for Cmax and AUC of saquinavir between the placebo and stiripentol phase were (-39.8, 39.8) and (-33.2, 112), respectively.

CONCLUSIONS

These results showed that stiripentol was a weak inhibitor of saquinavir metabolism both in vitro and in vivo. In contrast, stiripentol is a potent inhibitor of carbamazepine 10,11-epoxide formation in vitro and in vivo in epileptic patients.

Epileptic Encephalopathies with Myoclonic Seizures in Infants and Children (Severe Myoclonic Epilepsy and Myoclonic-Astatic Epilepsy)

Myoclonic attacks are not characteristic of a specific syndrome. In infancy and early childhood, they are often observed in the context of syndromes that are associated with other types of seizures and with cognitive impairment but no obvious brain lesion. Characterization of the associated seizures and age of expression allows inclusion of a number of cases in two main subgroups: severe myoclonic epilepsy (SME, or Dravet syndrome) and myoclonic-astatic epilepsy (MAE). Severe myoclonic epilepsy is an epileptic encephalopathy with invariably poor outcome in which myoclonic seizures, though frequently observed, may be absent altogether in some children. Prolonged and repeated febrile and afebrile convulsive seizures starting in infancy are the main feature and are probably causally related to cognitive decline. One third of children harbor mutation of the SCN1A gene, but the genetics of SME is probably more complex than expected with simple monogenic disorders. Treatment is usually disappointing. Myoclonic-astatic epilepsy is perhaps more a conceptual category of idiopathic myoclonic epilepsy than a discrete syndrome. Childhood-onset myoclonic-astatic attacks are the characteristic seizures associated in most with episodes of nonconvulsive status and generalized tonic-clonic seizures. Outcome is unpredictable. Either remission within a few years with normal cognition or long-lasting intractability with cognitive impairment is possible. Likewise, the effectiveness of antiepileptic drugs is variable. A number of cases of myoclonic epilepsies in infancy and early childhood, however, remain unclassified, and intermediate forms between the different syndromes exist. They must be distinguished from other syndromes with frequent brief attacks and repeated falls, especially the Lennox-Gastaut syndrome. This differentiation is often difficult and may require extensive neurophysiologic studies.

Treatment Strategies for Myoclonic Seizures and Epilepsy Syndromes with Myoclonic Seizures

Despite the availability of numerous treatment options, the diagnosis and treatment of myoclonic seizures continue to be challenging. Based on clinical experience, valproate and benzodiazepines have historically been used to treat myoclonic seizures. However, many more treatment options exist today, and the clinician must match the appropriate treatment with the patient's epilepsy syndrome and its underlying etiology. Comorbidities and other medications must also be considered when making decisions regarding treatment. Rarely, some antiepileptic drugs may exacerbate myoclonic seizures. Most epileptic myoclonus can be treated pharmacologically, but some cases respond better to surgery, the ketogenic diet, or vagus nerve stimulation. Because myoclonic seizures can be difficult to treat, clinicians should be flexible in their approach and tailor therapy to each patient.