Managing pediatric epilepsy syndromes with new antiepileptic drugs

Effects of adjunctive eslicarbazepine acetate on neurocognitive functioning in children with refractory focal-onset seizures

PURPOSE

This was a phase-II, randomized, double-blind (DB), placebo-controlled study aimed to evaluate neurocognitive effects of eslicarbazepine acetate (ESL) as adjunctive therapy in pediatric patients with refractory focal-onset seizures (FOS).

METHODS

Children (6-16years old) with FOS were randomized (2:1) to ESL or placebo. Treatment started at 10mg/kg/day, was up-titrated up to 30mg/kg/day (target dose), and maintained for 8weeks, followed by one-year open-label follow-up. The primary endpoint was change from baseline to the end of maintenance period in the composite Power of Attention assessed with the Cognitive Drug Research (CDR) system. Behavioral and emotional functioning and quality of life (QOL), secondary endpoints, were assessed with Child Health Questionnaire-Parent Form 50 (CHQ-PF50), Child Behavior Checklist (CBCL), and Raven's Standard Progressive Matrices (SPM). Efficacy was evaluated through changes in standardized seizure frequency (SF), responder rate, and proportion of seizure-free patients. Safety was evaluated by the incidence of treatment-emergent adverse events (TEAEs).

RESULTS

One hundred and twenty-three patients were randomized. A noninferiority analysis failed to reject the null hypothesis that the change from baseline in the Power of Attention score in the ESL group was at least 121ms inferior to the placebo group for all age groups. The CDR scores showed no differences between placebo and ESL in Power of Attention (1868.0 vs 1759.5), Continuity of Attention (1.136 vs -1.786), Quality of Working Memory (-0.023 vs -0.024), and Speed of Memory (-263.4 vs -249.6). Nonsignificant differences between placebo and ESL were seen for CHQ-PF50, CBCL scores, and Raven's SPM. Episodic Memory Index showed significant negative effect on ESL. Efficacy results favored the ESL group (SF least square [LS] means 1.98 vs 4.29). The TEAEs had a similar incidence between treatment groups (41.0% vs 47.5%).

CONCLUSIONS

Overall ESL did not produce statistically significant effects on neurocognitive and behavioral functioning in patients with epilepsy aged 6 to 16years. Additionally, ESL was effective in reducing seizure frequency and was well-tolerated.

Surgery for childhood epilepsy

Approximately 60% of all patients with epilepsy suffer from focal epilepsy syndromes. In about 15% of these patients, the seizures are not adequately controlled with antiepileptic drugs; such patients are potential candidates for surgical treatment and the major proportion is in the pediatric group (18 years old or less). Epilepsy surgery in children who have been carefully chosen can result in either seizure freedom or a marked (>90%) reduction in seizures in approximately two-thirds of children with intractable seizures. Advances in structural and functional neuroimaging, neurosurgery, and neuroanaesthesia have improved the outcomes of surgery for children with intractable epilepsy. Early surgery improves the quality of life and cognitive and developmental outcome and allows the child to lead a normal life. Surgically remediable epilepsies should be identified early and include temporal lobe epilepsy with hippocampal sclerosis, lesional temporal and extratemporal epilepsy, hemispherical epilepsy, and gelastic epilepsy with hypothalamic hamartoma. These syndromes have both acquired and congenital etiologies and can be treated by resective or disconnective surgery. Palliative procedures are performed in children with diffuse and multifocal epilepsies who are not candidates for resective surgery. The palliative procedures include corpus callosotomy and vagal nerve stimulation while deep brain stimulation in epilepsy is still under evaluation. For children with "surgically remediable epilepsy," surgery should be offered as a procedure of choice rather than as a treatment of last resort.

Long-term open-label study of adjunctive topiramate in infants with refractory partial-onset seizures

Data from 2 studies (phase 1 and phase 3) in infants <2 years old (N = 284; mean [SD] age, 12[6.3] months) with refractory partial-onset seizures were pooled to assess the long-term safety up to 1 year (primary objective) and tolerability of adjunctive topiramate treatment (mean treatment duration = 282 days). Monthly seizure rate summaries were also assessed. During the open-label extensions of these studies, study medication was first titrated to a dose of 25 mg/kg/d with subsequent uptitration to the maximum dosage tolerated, or seizure freedom, or a maximum of 60 mg/kg/d, whichever occurred first. The most common treatment-emergent adverse events (≥30%) were fever (52%), respiratory tract infections (51%), anorexia (35%), and acidosis (31%). Mean (SD) changes from pretreatment baseline to endpoint in Z scores for growth parameters were as follows: -0.82 (1.19) (body weight), -0.45 (1.60) (body length), and -0.36 (1.02) (head circumference).Tolerability in infants was consistent with previous studies.

Efficacy and safety of levetiracetam as an add-on therapy in children aged less than 4 years with refractory epilepsy

In the past decade, most studies on levetiracetam were conducted on patients aged > or = 4 years of age. The authors sought to assess the efficacy and safety of levetiracetam as an adjunctive treatment of children <4 years of age with refractory epilepsy. The mean levetiracetam dosage used on the 24 patients in this study was 38.85 mg/kg per day, and the mean duration of treatment was 40 weeks. During the study, levetiracetam was tapered off in 2 patients due to seizure worsening and was discontinued in other 2 patients due to unacceptable adverse effects. Levetiracetam therapy was effective in 58.3% of patients, with 20.8% achieving seizure freedom. Eight patients showed no obvious response and the remaining 2 patients showed divergent responses. Although adverse effects were seen in 37.5% of patients, all adverse effects were tolerable or resolved with time or discontinuation. Therefore, the authors conclude that levetiracetam treatment is effective and safe in young children with refractory epilepsy.

New antiepileptic drugs in pediatric epilepsy

New antiepileptic drugs (AEDs), introduced since 1993, provide more diverse options in the treatment of epilepsy. Despite the equivalent efficacy and better tolerability of these drugs, more than 25% of patients remain refractory to treatment. Moreover, the issues for pediatric patients are different from those for adults, and have not been addressed in the development and application of the new AEDs. Recently published evidence-based treatment guidelines have helped physicians to choose the most reasonable AED, although they cannot fully endorse new AEDs because of the lack of well-designed, randomized controlled trials. We review the mechanisms of action, pharmacokinetic properties, adverse reactions, efficacy, and tolerability of eight new AEDs (felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, topiramate, vigabatrin, and zonisamide), focusing on currently available treatment guidelines and expert opinions regarding pediatric epilepsy.

Apnea caused by mesial temporal lobe mass lesions in infants: report of 3 cases

Apnea as an isolated manifestation of seizures is well described in neonates but is only occasionally observed in infants. This article reports 3 infants presenting with apneic events as the main manifestation of seizure, documented by video electroencephalogram, all with mesial temporal lobe lesions. The 3 infants, after normal pregnancy and delivery at term, showed the first apnea at the age of 4 to 10 months. Although the interictal electroencephalogram result was often normal, ictal video electroencephalogram in all infants showed focal rhythmic discharges with or without generalization. Magnetic resonance imaging showed an inferior mesial temporal lobe mass lesion in all infants. All patients underwent lesion removal, and they are seizure free with normal psychomotor development.

Prospective assessment of levetiracetam pharmacokinetics during dose escalation in 4- to 12-year-old children with partial-onset seizures on concomitant carbamazepine or valproate

PURPOSE

To assess the multiple-dose pharmacokinetics of levetiracetam and its major metabolite ucb L057 in children with partial-onset seizures and determine whether it is affected by adjunctive carbamazepine or valproate. To correlate levetiracetam concentrations in plasma and saliva and to assess its safety and clinical response.

METHODS

Design was an open-label, multicenter study. Twenty-one children (4-12 years old) with epilepsy taking carbamazepine (13) or valproate (8) received adjunctive levetiracetam. Levetiracetam was initiated at 20 mg/(kg day) and titrated at 2-week intervals to 40 and then 60 mg/(kg day). Twelve-hour pharmacokinetics were determined at the end of each 2-week period. Efficacy was estimated from the partial seizure frequency per week and Global Evaluation Scale.

RESULTS

Levetiracetam was rapidly absorbed following oral dosing, with median t(max) of 0.5 h. Dose proportional increases were observed for C(max) and AUC((0-12)) over the dose range; t(1/2) was 4.9 h. Pharmacokinetics of levetiracetam and ucb L057 were not markedly different with concomitant carbamazepine or valproate; clearance was only 7-13% faster and AUC was decreased by only 15-24% in those on carbamazepine compared to valproate. Levetiracetam did not affect trough carbamazepine or valproate. Concentration in saliva and plasma were strongly correlated. Seizure frequency declined by 50% or more in 43% of subjects in the intent-to-treat population (n=21) and in 56% of those with seizures at baseline (n=16). Marked or moderate improvement occurred in 80% and 75% of patients based on Global Evaluation Scale ratings by investigators and parents/guardians, respectively. Levetiracetam was well tolerated.

CONCLUSION

Levetiracetam exhibits simple pharmacokinetics in children, with rapid absorption and dose-proportional kinetics. Small but not clinically relevant differences were observed between subjects receiving carbamazepine and valproate, suggesting significant dose adjustment is usually not necessary. This substantiates prior assessments that levetiracetam clearance is higher in children than adults, necessitating a higher dose in children on a mg/kg basis, and suggests it is useful add-on therapy for children with partial-onset seizures regardless of baseline therapy.

The cost-effectiveness of newer drugs as add-on therapy for children with focal epilepsies

PURPOSE

Epilepsies in children are complex diseases. Guidelines are needed on the appropriate use of newer versus older anti-epileptic drugs (AEDs). This paper presents an individual patient-sampling model to assess the cost-effectiveness of using newer AEDs as add-on therapy in line with UK prescribing guidance.

METHODS

Identification of the relevant parameters and treatment pathways for the model were achieved by a systematic review of the literature and discussions with clinical experts. Data were obtained from the literature and supplemented with data elicited from paediatric neurologists. The model considered paediatric patients over the period of childhood from the age of diagnosis to 18 years.

RESULTS

The results suggest that the older and newer AEDs are similar in terms of drug retention rates and the average time in 'good' treatment outcomes. In terms of cost, the results indicate a consistent increase in cost (compared to older AEDs) when all of the newer AEDs are considered. The decision analysis results indicate that there are no important health benefits from the use of newer AEDs when used as add-on therapy. However, the analysis also reveals that the uncertainties in the model are greater than the differences between the drug strategies.

CONCLUSIONS

To develop guidelines on the appropriate use of newer AEDs, better information is required from randomised controlled trials as there is insufficient data available in the public domain to accurately estimate the nature of the trade off between older versus newer AEDs.

Topiramate monotherapy in infantile spasm

Infantile spasm is an age-related refractory epilepsy. Topiramate is a new anticonvulsant with multiple mechanisms of action, and it may be effective for treating pediatric epilepsies. To evaluate the efficacy and tolerability of first-line topiramate treatment for infantile spasm, 20 patients received topiramate monotherapy during this study. They were treated with an initial dose of 1mg/kg/day, with a progressive titration of 1 mg/kg a week until their spasms were controlled and a maximum dose of 12 mg/kg/day was achieved. The evaluation of the treatment efficacy was based on the spasm frequency data that was obtained by the scalp and video-EEG, and by the parental count of spasm. Thirty percent of the subjects became spasm-free during the study. Six of 20 subjects (30%) had cessation of spasm and disappearance of hypsarrhythmia as seen via the video EEG; four (50%) of eight idiopathic patients had a response, whereas two (17%) of 12 patients with symptomatic infantile spasm responded. Seventy of the patients, including the spasm-free patients, had a reduction in their seizure frequency of more than 50%, and 10% of the patients had a reduction in their seizure frequency of less than 50%. The clusters of spasm frequency decreased from 10.6 +/- 8.5 to 3.5 +/- 1.4 clusters/day. Topiramate is effective and tolerated in those patients suffering from infantile spasm. Our results suggest that this drug should be considered as a new first-line drug for treating infantile spasm.

Nonepileptic uses of antiepileptic drugs in children and adolescents

Antiepileptic drugs are often prescribed for nonepileptic neurologic and psychiatric conditions. The United States Food and Drug Administration has approved several antiepileptic drugs for the treatment of neuropathic pain, migraine, and mania in adults. For pediatric patients, use of antiepileptic drugs for non-seizure-related purposes is supported mainly by adult studies, open-label trials, and case reports. Summarized here is the published literature for or against the use of antiepileptic drugs for neuropathic pain, migraine, movement disorders, bipolar disorder, aggressive behavior, and pervasive developmental disorders in children and adolescents. Using the American Academy of Neurology's four-tiered classification scheme for a therapeutic article and translation to a recommendation rating, there are no nonepileptic disorders for which antiepileptic drugs have been established as effective for pediatric patients. Valproate and carbamazepine are "possibly effective" in the treatment of Sydenham chorea, and valproate is "probably effective" in decreasing aggressive behavior. Carbamazepine is "probably ineffective" in the treatment of aggression, and lamotrigine is "possibly ineffective" in improving the core symptom of pervasive developmental disorders. Despite the frequent use of antiepileptic drugs in the treatment of juvenile bipolar disorder, migraine, and neuropathic pain, the data are insufficient to make recommendations regarding the efficacy of antiepileptics in these conditions in children and adolescents.

Epilepsy in children: the evidence for new antiepileptic drugs

Childhood epilepsy remains a challenge to treat. Despite the availability of antiepileptic drugs (AEDs), >25% of children with childhood epilepsy continue to have seizures. Conventional AEDs have been the mainstay of therapy for many years but are often poorly tolerated and have a tendency to interact with other drugs. Current American Academy of Neurology guidelines support the use of four of the newer AEDs (gabapentin, lamotrigine, topiramate, and oxcarbazepine) as adjunctive treatment of refractory partial seizures in children, based on class I evidence. This paper includes a summary of the results from a recent randomized, double-blind, placebo-controlled study, which shows that levetiracetam is also effective and well tolerated in this pediatric population, and provides evidence supporting its use in refractory partial seizures in children.

Antiepileptic drugs trials: Neonates and infants

Special issues are related to AED testing in several populations. Pharmacokinetics, pharmacodynamics and underlying neurochemistry and developing systems require specific testing in appropriate infants with refractory seizures. EEG monitoring is an essential part of seizure definition and recognition, making it a necesssity along with clinical semiology to define the seizure types and changes in seizure frequency. (1) Neonates: A trial design for neonatal seizures should be similar to those used for the treatment of status epilepticus. Proposed study end points should be seizure cessation for some period of time, or time to next seizure. The use of placebo is questionable. (2) Partial seizures occurring in young infants: A trial designed for topirimate included a placebo controlled, double blind study with fixed dose trials exploring the range of tolerated doses. Forty-eight hour video EEGs were used for quantification of seizures. (3) Uncommon forms of encephalopathic epilepsy: a proposed design includes randomization to sequential monotherapy with prescribed titration/dose defined by seizure control or tolerance. Outcome variables include seizure reduction, tolerability, and time continued on AED.

Long-term safety and tolerability of oxcarbazepine in children: a review of clinical experience

Relatively few well-designed studies have demonstrated the long-term safety and tolerability of newer antiepileptic drugs (AEDs) in a large group of children. Extensive clinical data from the worldwide Clinical Development Program (CDP) and a compassionate use program on the safety and tolerability of oxcarbazepine in children are presented. Oxcarbazepine is a newer AED that is indicated for use as monotherapy and adjunctive therapy in children (United States 4 years of age, Europe 6 years of age) with partial epilepsy. The most common adverse events (10%) in the CDP were headache (32.5%), somnolence (31.5%), vomiting (27.6%), and dizziness (23.1%), whereas in the compassionate use program (clinical practice situation), the most common adverse events (1%) reported were rash (2.7%), fatigue (1.6%), nausea (1.2%), and somnolence (1.2%). These data indicate that oxcarbazepine has a good long-term safety and tolerability profile, whether given as monotherapy or adjunctive therapy, in children with partial seizures.

Nonpharmacological treatment options for epilepsy

Approximately one third of children with epilepsy have persistent seizures despite trials of multiple antiepileptic medications. For some of these patients, epilepsy surgery may provide freedom from seizures. However, in many cases, epilepsy surgery is not a viable treatment option. Nonpharmacological approaches are a useful adjunct to help manage seizures in these children. This review examines the role of vagus nerve stimulation, the ketogenic diet, and various forms of EEG biofeedback therapy in children with intractable epilepsy. Although the mechanism of action is not known precisely for any of these adjunctive therapies, they add an important and evolving dimension to the management of difficult to control epilepsy in children. In addition, pyridoxine-dependent seizures are discussed as an example of an etiology of refractory seizures that responds well to replacement therapy.

Extended-release formulations: simplifying strategies in the management of antiepileptic drug therapy

Advances in our understanding, diagnosis, and treatment of seizure disorders have transformed the management of epilepsy. As the number of antiepileptic drugs and their formulations increase, so do the expectations of therapy. Once limited to attaining complete control of seizures, epilepsy management now strives to enable patients to lead lifestyles consistent with their own capabilities. Extended-release antiepileptic drug formulations can help achieve the primary treatment goals for many patients with epilepsy: preventing occurrence of seizures and preventing or reducing side effects. The dosing flexibility and consistency of serum levels (without marked peak-to-trough fluctuations) conferred by extended-release formulations help achieve these goals. These same attributes of extended-release formulations may also improve compliance, quality of life, and patient satisfaction with treatment.

Antiepileptic Drugs in Children with Developmental Delays and Behavioral Problems

Children with multiple handicaps, including developmental delays and behavioral problems, frequently have epilepsy that requires treatment. Different strategies should be used for acute treatment versus chronic treatment. Experience suggests that there is no true drug of choice that can be used for all children with epilepsy; however, seizure type, epilepsy syndrome, and likely efficacy and side effect spectrum of the antiepileptic drug (AED) will determine the best treatment for each child. In general, phenobarbital has posed multiple behavioral problems, and, thus, is less commonly used. Carbamazepine is the most frequently used drug for the treatment of partial seizures with or without secondary generalization, and valproate is the long established, broad spectrum AED for children with generalized convulsive and nonconvulsive seizures. Newer AEDs allow alternative treatments to those with adverse effects to the more frequently used medications and may have cognitive or behavioral advantages.

Therapeutics in pediatric epilepsy, Part 1: The new antiepileptic drugs and the ketogenic diet

Epilepsy is one of the most common and challenging neurologic disorders affecting children. Although various modalities exist to treat pediatric-onset seizures, seizures in 25% of children who are diagnosed as having epilepsy remain refractory to available therapies. Of the 8 new antiepileptic drugs (AEDs) (felbamate, gabapentin, lamotrigine, topiramate, tiagabine, levetiracetam, oxcarbazepine, and zonisamide), all but 2 (zonisamide and levetiracetam) have received Food and Drug Administration approval for adjunctive use in the pediatric population. However, most of the new AEDs used in adults have also been used in children, beyond the AEDs' approved indications. The ultimate goal of patient management is to choose the therapeutic option that provides the best chance of improving the patient's quality of life. Issues that relate to treatment choice include the likelihood of seizure recurrence, type and severity of seizures, available AED efficacies and toxicities, need for hematologic monitoring, ease of dosing, underlying medical conditions, medication interactions, urgency of initiating therapy, and cost. In this review, we discuss these issues for each of the 8 new AEDs; we also discuss the ketogenic diet and briefly review the older AEDs. Knowledge of the available AEDs will enable the practitioner to choose the best drug or drugs for individual patients.

Lamotrigine versus valproate monotherapy-associated weight change in adolescents with epilepsy: results from a post hoc analysis of a randomized, double-blind clinical trial

Recent trends toward obesity and associated health risks in children highlight the significance of weight gain as a side effect with certain antiepilepsy drugs. No previous study has prospectively compared, in adolescents, weight effects for two commonly used antiepilepsy drugs. We report results from a post hoc subanalysis of adolescent data from a randomized, double-blind study comparing weight effects of lamotrigine and valproate. Patients were > or = 12 years of age with new-onset partial or generalized seizures who were randomized 1:1 to lamotrigine or valproate. Patients were escalated to a dose range of 100 to 500 mg/day for lamotrigine and 10 to 60 mg/kg/day for valproate based on clinical response, with target doses maintained for 24 weeks. Results are reported for adolescents aged 12 to 20 years. Weight changes during maintenance were higher (P < .05) in valproate (n = 20) patients than in lamotrigine (n = 18) patients, and change in body mass index was higher (P < .05) in valproate patients at the end of the study. At week 32, mean body mass index in the valproate group was above the 85th percentile representing "at risk for overweight." Whereas weight remained stable in adolescents treated with lamotrigine, weight increased in those treated with valproate by week 10 of this study and continued to increase at the end of the study.

Intractable pediatric epilepsy: vagal nerve stimulation and the ketogenic diet

The KD has been proven an effective alternative epilepsy treatment in children refractory to standard anticonvulsants. Children to be placed on the diet must be carefully selected, monitored, and followed. The diet is to be regarded as a strict medical regimen and requires a comprehensive medical team approach in concert with intensive parental involvement. With better understanding of the scientific principles underlying brain ketosis, we should be able to optimize the KD to achieve even better results.

Epilepsy surgery. Presurgical evaluation

The presurgical evaluation should result in a clear understanding of whether surgery can be undertaken and its associated risks and potential for benefit. The results of surgery are best when there is congruence in the seizure semiology, the irritative zone on interictal EEG, and the ictal onset zone with the epileptogenic lesion as defined on MRI and PET, and when there is a clear understanding of the ictal onset zone's relationship to eloquent cortex as defined by neuropsychologic evaluation, the intracarotid amobarbital test, and cortical functional mapping.

Visual field constriction in 91 Finnish children treated with vigabatrin

PURPOSE

To study the prevalence and features of visual field constrictions (VFCs) associated with vigabatrin (VGB) in children.

METHODS

A systematic collection of all children with any history of VGB treatment in fifteen Finnish neuropediatric units was performed, and children were included after being able to cooperate reliably in repeated visual field tests by Goldmann kinetic perimetry. This inclusion criterion yielded 91 children (45 boys; 46 girls) between ages 5.6 and 17.9 years. Visual field extent <70 degrees in the temporal meridian was considered abnormal VFC.

RESULTS

There was a notable variation in visual field extents between successive test sessions and between different individuals. VFCs <70 degrees were found in repeated test sessions in 17 (18.7%) of 91 children. There was no difference in the ages at the study, the ages at the beginning of treatment, the total duration of the treatment, general cognitive performance, or neuroradiologic findings between the patients with normal visual fields and those with VFC, but the patients with VFC had received a higher total dose of VGB. In linear regression analysis, there were statistically significant inverse correlations between the temporal extent of the visual fields and the total dose and the duration of VGB treatment. The shortest duration of VGB treatment associated with VFC was 15 months, and the lowest total dose 914 g.

CONCLUSIONS

Because of a wide variation in normal visual-field test results in children, the prevalence figures of VFCs are highly dependent on the definition of normality. Although our results confirm the previous findings that VFC may occur in children treated with VGB, our study points out the need to reevaluate critically any suspected VFC to avoid misdiagnosis. Nevertheless, our study suggests that the prevalence of VFC may be lower in children than in adults, and that the cumulative dose of VGB or length of VGB therapy may add to the personal predisposition for developing VFC.

Efficacy and safety of levetiracetam in children with partial seizures: an open-label trial

PURPOSE

To assess the efficacy and safety of levetiracetam (LEV) as adjunctive therapy in children with treatment-resistant partial-onset seizures.

METHODS

Children (aged 6-12 years) with treatment-resistant partial-onset seizures receiving one standard antiepileptic drug (AED) were eligible. After a 4-week baseline period, children received LEV in a 6-week titration phase (target dose, 40 mg/kg/day) followed by an 8-week evaluation phase. Seizure frequency during the evaluation period with individualized LEV doses (20-40 mg/kg/day) were compared with the 4-week baseline seizure frequency. Plasma concentrations of LEV and other AEDs were determined to evaluate potential drug interactions.

RESULTS

Twenty-four subjects enrolled and received LEV; 23 entered the evaluation phase, and 22 completed the evaluation phase. Compared with their baseline seizure frequency, 12 (52%) of 23 subjects entering the evaluation phase had their seizure frequency decrease by >50%. Two subjects remained seizure free during the entire evaluation period. LEV did not significantly affect plasma concentrations of any concomitant AED during this study, and no alteration of mean clinical laboratory values was observed. The most commonly reported adverse events were headache, infection, anorexia, and somnolence.

CONCLUSIONS

This open-label study of adjunctive LEV therapy (at 20-40 mg/kg/day) suggests that LEV is effective, safe, and well tolerated in children ages 6-12 years with treatment-resistant partial-onset seizures. A randomized, placebo-controlled, double-blind trial of LEV adjunctive therapy in children with treatment-resistant partial-onset seizures is needed and ongoing to confirm these open-label findings.

Refractory epilepsy: a progressive, intractable but preventable condition?

Intractable seizures are just one manifestation of 'refractory epilepsy', which can be recognized as a distinct condition with multifaceted dimensions, including neurobiochemical plastic changes, cognitive decline and psychosocial dysfunction, leading to dependent behaviour and a restricted lifestyle. The biological basis of 'refractoriness' is likely to be multifactorial, and may include the severity of the syndrome and/or underlying neuropathology, abnormal reorganization of neuronal circuitry, alteration in neurotransmitter receptors, ion channelopathies, reactive autoimmunity, and impaired antiepileptic drug (AED) penetration to the seizure focus. Some of these deleterious changes may be a consequence of recurrent seizures. We hypothesize that 'refractory epilepsy' may be prevented by interrupting this self-perpetuating progression. There is increasing evidence that these patients can be identified early in the clinical course and, thus, be targeted early for effective therapeutic intervention. Failure of two first-line AEDs due to lack of efficacy or poor tolerability should prompt consideration of epilepsy surgery in a patient with a resectable brain abnormality. For the majority not suitable for 'curative' surgery, AEDs should be combined with the aim of achieving 'synergism'. This strategy has the potential to improve outcome by preventing the insidious progression to intractable 'refractoriness' and a downward spiraling quality of life.

New antiepileptic drugs: comparative studies of efficacy and cognition

Over the past 10 years, the Food and Drug Administration has approved eight prophylactic antiepileptic drugs (AEDs). Although the goal of universal seizure control without side effects has not been reached, the tolerability of medications has improved. This paper reviews the AEDs introduced since 1993 and tries to objectively present comparative data obtained in double-blind studies.

Pharmacokinetic study of levetiracetam in children

PURPOSE

The pharmacokinetics of the novel antiepileptic drug (AED) levetiracetam and its major metabolite, ucb L057, were studied in children with partial seizures in a multicenter, open-label, single-dose study.

METHODS

Twenty-four children (15 boys, nine girls), 6 to 12 years old, received a single dose of levetiracetam (20 mg/kg) as an adjunct to their stable regimen of a single concomitant AED, followed by a 24-h pharmacokinetic evaluation.

RESULTS

In children, the half-lives of levetiracetam and its metabolite ucb L057 were 6.0 +/- 1.1 and 8.1 +/-2.7 hours, respectively. The Cmax and area under the curve (AUC) of levetiracetam equated for a 1-mg/kg dose were lower in children (Cmax, norm=1.33 plus minus 0.35 microg/ml; AUCnorm=12.4 +/- 3.5 microg/h/ml) than in adults (Cmax, norm=1.38 +/- 0.05 microg/ml; AUCnorm=11.48 +/- 0.63 microg/h/ml), whereas the renal clearance was higher. The apparent body clearance (1.43 +/- 0.36 ml/min/kg) was approximately 30-40% higher in children than in adults. Levetiracetam was generally well tolerated.

CONCLUSIONS

On the basis of these data, a daily maintenance dose equivalent to 130-140% of the usual daily adult maintenance dosage (1,000-3,000 mg/day) in two divided doses, on a weight-normalized level (mg/kg/day) is initially recommended. Clinical efficacy trials in children are ongoing with dosages of 20 to 60 mg/kg/day.

Topiramate in the catastrophic epilepsies of childhood

Several epileptic syndromes that occur during childhood are characterized by severe treatment-resistant seizures, progressive loss of higher intellectual functions, and characteristic electroencephalographic abnormalities. These catastrophic epileptic syndromes include epileptic encephalopathy with diffuse slow spike waves (Lennox-Gastaut syndrome), West syndrome, progressive myoclonic epilepsies, and electrical status epilepticus during sleep. This article summarizes each syndrome and reviews the most recent information concerning the effectiveness of topiramate with respect to each condition. Suggestions are offered to help clinicians maximize topiramate's efficacy and tolerability in patients suffering with these syndromes. Overall, topiramate is a valuable antiepileptic medication in the treatment of catastrophic pediatric epileptic syndromes.

Normal growth during lamotrigine monotherapy in pediatric epilepsy patients -- a prospective evaluation of 103 children and adolescents

Physical maturation is one of the essential developmental processes during childhood and adolescence, which can be adversely affected by a number of internal and external factors. An important side effect associated with the long-term use of some antiepileptic drugs is change in body weight, followed by an increased risk for subsequent maturational problems in pediatric epilepsy patients. To evaluate the effect of lamotrigine on body growth in children and adolescents with epilepsy, weight, height and body mass index (BMI) values of 103 pediatric epilepsy patients (m/f ratio: 53/50) treated with lamotrigine monotherapy were prospectively evaluated for a period of 18.7+/-11.8 (range 6--71) months. Age at therapy introduction was 6.7+/-2.7 (range 1.6-16.4) years and daily lamotrigine dose was 7.4+/-2.2 (range 3.5--14.2) mg/kg body weight (BW). Standard deviation scores (S.D.S.) at therapy initiation versus follow-up were height -- S.D.S.: 0.07+/-0.42 versus 0.08+/-0.42 (P=n.s.); weight -- S.D.S.: -0.01+/-0.44 versus -0.01+/-0.43 (P=n.s.) and BMI -- S.D.S.: -0.24+/-0.47 versus -0.25+/-0.37 (P=n.s.). Lamotrigine long-term monotherapy was associated with normal body growth in pediatric and adolescent patients with epilepsy, regardless of patient age, gender or duration of therapy.

Idiosyncratic reactions: new methods of identifying high-risk patients

This article describes the mechanisms of idiosyncratic drug reactions (IDRs) and provides an analysis of potential methods for identifying patients at high risk for antiepileptic idiosyncratic drug reactions. IDRs may be caused by toxic metabolites, either directly or indirectly (by way of an immunologic response or a free radical-mediated process). Four methods to potentially identify patients at high risk for AED IDRs are discussed: development of an "at-risk" clinical profile for a particular AED: identification of biomarkers that measure the formation of a toxic metabolite by a previously unrecognized bioactivation pathway for a particular AED; identification of biomarkers indicating deficient detoxification abilities [e.g., deficient free radical scavenging enzyme activities or low calculated oxidative protection (COP) ratios 1 and 2]; and identification of at-risk genetic markers. Clinical profiles for patients receiving valproic acid (VPA), felbamate (FBM), and lamotrigine (LTG) and who are at risk for development of AED IDRs are presented. Patients with VPA IDRs have deficient erythrocyte glutathione peroxidase activity, low plasma selenium concentrations, low COP1 ratios, and low COP2 ratios compared with age-matched controls. Patients with FBM-associated aplastic anemia have deficient erythrocyte glutathione peroxidase, superoxide dismutase (SOD), and glutathione reductase activities compared with age-matched controls. Use of at-risk clinical profiles (for VPA, FBM, and LTG) and measurement of erythrocyte glutathione peroxidase activity, erythrocyte SOD activity, and calculation of COP1 and COP2 ratios (for VPA and FBM) are inexpensive, simple methods of identifying high-risk patients for IDRs. Research is needed to further characterize the mechanism of IDRs, to investigate the clinical utility of free radical-scavenging enzyme activity measurement and calculation of COP ratios for other AED IDRs, and to develop additional methods of identifying patients at high risk for AED IDRs.

Pediatric epilepsy surgery: neuroimaging, neuropsychology, and anticonvulsants

Neuroimaging and the neuropsychological evaluation are important components of the presurgical evaluation for epilepsy surgery. Advances in neuroimaging over the last decade, to a large part, underlie improvements in pediatric epilepsy surgery outcomes. The neuropsychological evaluation plays an important role in the evaluation of the older child and adolescent, particularly in the evaluation of mesial temporal sclerosis. However, its role in the young child being considered for surgery remains to be defined. This section reviews the definition of medical intractability, issues related to medication withdrawal during video-EEG monitoring, recent neuroimaging advances, and the neuropsychological evaluation.

Intractable pediatric epilepsy: presurgical evaluation

Epilepsy surgery in children requires a multidisciplinary approach. This section examines the role of scalp EEG, video-EEG monitoring, and intracranial EEG in the presurgical evaluation. Concepts central to understanding the basis for surgical treatment, such as the epileptogenic zone, the irritative zone, and the epileptogenic lesion, are discussed. An illustrative case then demonstrates application of the process in clinical practice. Neuroimaging and neuropsychological issues are not discussed herein; rather they are addressed elsewhere in this issue.