Seizure Aggravation in Idiopathic Generalized Epilepsies

The landscape of drug resistant absence seizures in adolescents and adults: Pathophysiology, electroclinical spectrum and treatment options

The persistence of typical absence seizures (AS) in adolescence and adulthood may reduce the quality of life of patients with genetic generalized epilepsies (GGEs). The prevalence of drug resistant AS is probably underestimated in this patient population, and treatment options are relatively scarce. Similarly, atypical absence seizures in developmental and epileptic encephalopathies (DEEs) may be unrecognized, and often persist into adulthood despite improvement of more severe seizures. These two seemingly distant conditions, represented by typical AS in GGE and atypical AS in DEE, share at least partially overlapping pathophysiological and genetic mechanisms, which may be the target of drug and neurostimulation therapies. In addition, some patients with drug-resistant typical AS may present electroclinical features that lie in between the two extremes represented by these generalized forms of epilepsy.

Efficacy and Safety of Five Broad-Spectrum Antiseizure Medications for Adjunctive Treatment of Refractory Epilepsy: A Systematic Review and Network Meta-analysis

BACKGROUND

Overall, up to one-third of epilepsy patients have drug-resistant epilepsy. However, there was previously no meta-analysis to support the guidelines for broad-spectrum antiseizure medication selection for the adjunctive treatment of refractory epilepsy. In the present meta-analysis, we assessed the efficacy and safety of three second-generation broad-spectrum antiseizure medications, lamotrigine (LTG), levetiracetam (LEV), and topiramate (TPM), and two third-generation broad-spectrum antiseizure medications, perampanel (PER) and lacosamide (LCM), for the adjunctive treatment of refractory epilepsy.

METHODS

We systematically searched PubMed, Embase, and CENTRAL from inception to July 15, 2022. The studies included in the meta-analysis were required to meet the following criteria: (1) be randomized, double-blind clinical trials; (2) include patients aged >2 years with a clinical diagnosis of drug-resistant epilepsy; (3) have at least 8 weeks for the treatment period excluding the titration phase; and (4) report the outcomes of seizure response, seizure freedom and the withdrawal rate due to treatment-emergent adverse effects. Data were extracted, and the risk of bias for each study was assessed by two authors independently using RoB2 tools. We performed the network meta-analysis for each outcome through a group of programs in the mvmeta and network packages in Stata. Relative odds ratios with 95% confidence intervals were calculated as the result of the analyses. The surface under the cumulative ranking curve (SUCRA) and mean ranks were used to rank these treatments.

RESULTS

Forty-two randomized controlled trials (RCTs) (LTG-placebo: n = 6, LEV-placebo: n = 13, TPM-placebo: n = 9, PER-placebo: n = 6, LCM-placebo: n = 7, LEV-TPM: n = 1) with 10257 participants (LTG = 569, LEV = 1626, TPM = 701, PER = 1734, LCM = 1908, placebo = 3719) were included. Levetiracetam had subequal efficacy in 50 % seizure frequency reduction to TPM [odds ratio (OR) 1.00, 95% confidence interval (CI) 0.73-1.38], and LEV had a higher rate of ≥ 50% seizure frequency reduction than LCM (OR 1.49, 95% CI 1.11-2.01) and PER (OR 1.68, 95% CI 1.24-2.29). Levetiracetam was also related to a higher proportion of seizure freedom participants than TPM (OR 1.87, 95% CI 1.20-2.89), PER (OR 2.23, 95% CI 1.12-4.43), and LCM (OR 2.97, 95% CI 1.46-6.05). In addition, LEV was associated with a lower risk of experiencing at least one treatment-emergent adverse event (TEAE) than PER (OR 0.63, 95% CI 0.46-0.85) and TPM (OR 0.51, 95 % CI 0.36-0.72) and a lower proportion of patients experiencing TEAEs leading to discontinuation than PER (OR 0.51, 95% CI 0.27-0.97) and TPM (OR 0.50, 95 % CI 0.27-0.93).

CONCLUSIONS

Third-generation drugs (PER and LCM) had no advantages in terms of efficacy and safety for adjunctive treatment of refractory epilepsy compared with several second-generation drugs (LEV and LTG). Levetiracetam was the priority choice for adjunctive treatment of refractory epilepsy. Perampanel and LCM had no advantages in terms of efficacy and safety among the five drugs.

REGISTRATION

PROSPERO registration number, CRD42022344153; last edited on December 23, 2022.

How have the recent updated epilepsy classifications impacted on diagnosis and treatment?

INTRODUCTION

Epilepsies are a diverse group of disorders which differ regarding prognosis for seizure control and associated comorbidities. Accurate classification is critical to choose the highest yield investigations and best therapeutic options and to provide the most accurate prognoses regarding the expected degree of seizure control, possible remission, and risk of associated comorbidities to patients and their families. This article reviews the recent updates in epilepsy classification to illustrate how accurate classification impacts care for persons with epilepsy.

AREAS COVERED

The authors discuss the ILAE 2017 Classification of the Epilepsies along with the modification of the classification for neonatal seizures and epilepsies. They also discuss the ILAE position papers on Epilepsy syndromes in neonates and infants and children of variable age and the Idiopathic Generalized Epilepsies.

EXPERT OPINION

Accurate epilepsy classification allows selection of the highest yield investigations, choice of optimal therapies, and accurate prognostication of seizures (likelihood of response to antiseizure treatments and likelihood of remission with age), as well as comorbidities (likelihood, type, and severity). As we move into the era of disease modifying therapy, early accurate identification of underlying causes with timely introduction of specific treatments will be crucial to lessen the severity of epilepsy, with improved seizure control and attenuation of associated comorbidities.

Endocytosis of AMPA receptors: Role in neurological conditions

AMPA receptors are glutamate-gated ion channels, present in a wide range of neuron types and in glial cells. Their main role is to mediate fast excitatory synaptic transmission, and therefore, they are critical for normal brain function. In neurons, AMPA receptors undergo constitutive and activity-dependent trafficking between the synaptic, extrasynaptic and intracellular pools. The kinetics of AMPA receptor trafficking is crucial for the precise functioning of both individual neurons and neural networks involved in information processing and learning. Many of the neurological diseases evoked by neurodevelopmental and neurodegenerative malfunctions or traumatic injuries are caused by impaired synaptic function in the central nervous system. For example, attention-deficit/hyperactivity disorder (ADHD), Alzheimer's disease (AD), tumors, seizures, ischemic strokes, and traumatic brain injury are all characterized by impaired glutamate homeostasis and associated neuronal death, typically caused by excitotoxicity. Given the important role of AMPA receptors in neuronal function, it is not surprising that perturbations in AMPA receptor trafficking are associated with these neurological disorders. In this book chapter, we will first introduce the structure, physiology and synthesis of AMPA receptors, followed by an in-depth description of the molecular mechanisms that control AMPA receptor endocytosis and surface levels under basal conditions or synaptic plasticity. Finally, we will discuss how impairments in AMPA receptor trafficking, particularly endocytosis, contribute to the pathophysiology of various neurological disorders and what efforts are being made to therapeutically target this process.

Assessment of the long-term efficacy and safety of adjunctive perampanel in adolescent patients with epilepsy: Post hoc analysis of open-label extension studies

OBJECTIVE

This post hoc analysis of four open-label extension (OLEx) studies evaluated the long-term efficacy and safety of adjunctive perampanel in adolescent patients (aged 12 to ≤17 years) with focal-onset seizures (FOS), with/without focal to bilateral tonic-clonic seizures (FBTCS), or generalized tonic-clonic seizures (GTCS).

METHODS

Patients who completed one of six double-blind, placebo-controlled studies could enter one of four OLEx studies comprising a blinded Conversion Period (6-16 weeks) followed by a Maintenance Phase (27 to ≤256 weeks; perampanel dose: ≤12 mg/day). Exposure, retention, seizure outcomes, and treatment-emergent adverse events (TEAEs) were analyzed. Efficacy outcomes were analyzed using observed case and last observation carried forward (LOCF) approaches; the latter was used to account for early dropouts.

RESULTS

The Full Analysis Set comprised 309 adolescents with FOS (FBTCS, n = 109) and 19 with GTCS, and the Safety Analysis Set comprised 311 with FOS (FBTCS, n = 110) and 19 with GTCS. Mean (standard deviation) cumulative duration of perampanel exposure (weeks) was: FOS, 77.7 (58.7); FBTCS, 88.7 (63.8); and GTCS, 97.0 (35.5). Retention rates were maintained for ≤2 years (FOS, 50.0 %; FBTCS, 57.1 %; GTCS, 41.7 %). Seizure control (median percent reduction in seizure frequency/28 days) was sustained for up to 2 years; FOS (59.4 %, n = 113), FBTCS (64.6 %, n = 53), and GTCS (86.5 %, n = 17). At Year 2, 50 % responder rates were: FOS, 58.4 % (n = 66); FBTCS, 54.7 % (n = 29); and GTCS, 82.4 % (n = 14); seizure-freedom rates were: FOS, 5.3 % (n = 6); FBTCS, 24.5 % (n = 13); and GTCS, 35.3 % (n = 6). Long-term seizure control was observed even in LOCF analyses. The incidence of TEAEs was highest during Year 1 (FOS, n = 269 [86.5 %]; FBTCS, n = 95 [86.4 %]; GTCS, n = 15 [78.9 %]), compared with Years 2-4; the most common (≥10 % of patients) were dizziness, somnolence, and nasopharyngitis. No new safety signals emerged with long-term treatment.

CONCLUSIONS

This post hoc analysis suggests that long-term (≤2 years) adjunctive perampanel (≤12 mg/day) is efficacious and generally well tolerated in adolescent patients with FOS, with or without FBTCS, or GTCS.

Staring Spells: How to Distinguish Epileptic Seizures from Nonepileptic Staring

OBJECTIVE

To determine the nature of staring spells and factors distinguishing epileptic from nonepileptic staring spells, we studied the clinical and demographic features of children with staring spells referred to a regional new-onset seizure clinic.

STUDY DESIGN

Our retrospective chart review encompassed 2818 consecutive patients evaluated in the new-onset seizure clinic between September 22, 2015, and March 19, 2018. We identified 121 patients with newly presenting staring spells.

RESULTS

Sixty-two of 121 (51%) children were diagnosed with nonepileptic staring spells and 59 (49%) with epileptic seizures (24 with absence epilepsy, 35 with focal epilepsy). Patients with nonepileptic staring spells were younger (4.8 vs 7.1 years, P = .001) and more likely to have developmental delay (P = .005) than the seizure group. There was an 8.9-month delay on average from the onset of staring spells to the new-onset seizure clinic visit. The emergency department was a referral source for 80% (28/35) of focal seizures. In children with focal seizures, the staring spells typically lasted >1minute (29/35, 83%), whereas only 19 of 62 (31%) of children with nonepileptic staring spells had events lasting this long (P = .04). All children had a routine electroencephalography (EEG) on the day of new-onset seizure clinic visit. EEG was diagnostic in 100% (24/24) of absence seizures and 51% (18/35) of focal seizures.

CONCLUSIONS

In children presenting with staring spells, the differential diagnosis of epileptic staring spells vs nonepileptic staring spells can be made by history and routine EEG. Staring was as likely to be epileptic as nonepileptic spells. Younger children with developmental delay were more likely to have nonepileptic events. Our simple approach based on event duration, postictal symptoms, and EEG allowed identification of epileptic staring on first visit to new-onset seizure clinic but requires validation in future prospective studies including long-term video EEG monitoring and follow-up.

Drug-resistant epilepsy at the age extremes: Disentangling the underlying etiology

The incidence of epilepsy is highest at the extreme age ranges: childhood and elderly age. The most common syndromes in these demographics - self-limited epilepsies of childhood and idiopathic generalized epilepsies in pediatric age, focal epilepsy with structural etiology in older people - are expected to be drug responsive. In this work, we focus on such epilepsy types, overviewing the complex clinical background of unexpected drug-resistance. For self-limited epilepsies of childhood and idiopathic generalized epilepsies, we illustrate drug-resistance resulting from syndrome misinterpretation, reason on possible unexpected courses of epilepsy, and explicate the influence of inappropriate treatments. For elderly-onset epilepsy, we show the challenges in differential diagnosis possibly leading to pseudoresistance and analyze how drug-resistant epilepsy can arise in stroke, neurocognitive disorders, brain tumors, and autoimmune encephalitis. In children and senior people, drug-resistance can be regarded as a hint to review the diagnosis or explore alternative therapeutic strategies. Refractory seizures are not only a therapeutic challenge, but also a cardinal sign not to be overlooked in syndromes commonly deemed to be drug-responsive.

Seizure exacerbation with anti-seizure medications in adult patients with epilepsy

There are numerous reports of seizure exacerbation related to specific anti-seizure medications (ASMs); however, a quantitative analysis with clearly defined parameters for seizure exacerbation in an outpatient setting is lacking. This retrospective study examines adult patients starting a single ASM and follows patient outcomes over the course of treatment, with quantitative evaluation of the incidence of paradoxical seizure exacerbation. In this study, outpatient encounters with five epileptologists at the Baylor College of Medicine Comprehensive Epilepsy Center were evaluated over a 10-month period. Seizure exacerbation was defined as an increase in seizure frequency at least 2 times greater than the baseline seizure frequency after initiation of an ASM, with return to baseline after ASM discontinuation. Patients were stratified into four categories: (1) probable ASM-induced seizure exacerbation; (2) possible ASM-induced seizure exacerbation; (3) non-ASM induced seizure exacerbation; or (4) no seizure exacerbation. Out of a total of 236 encounters where an ASM was initiated, we found that 5.5% of patients experienced some form of seizure exacerbation. However, only 1.3% of patients had probable ASM-induced seizure exacerbation. Consistent with prior studies, our data indicate seizure exacerbation in adults is rare with the initiation of ASMs. However, further studies with a larger sample size are necessary to better understand what factors may predispose patients to potential medication-induced seizure exacerbation.

The Critical Modulatory Role of Spiny Stellate Cells in Seizure Onset Based on Dynamic Analysis of a Neural Mass Model

Growing evidence suggests that excitatory neurons in the brain play a significant role in seizure generation. Nonetheless, spiny stellate cells are cortical excitatory non-pyramidal neurons in the brain, whose basic role in seizure occurrence is not well understood. In the present research, we study the critical role of spiny stellate cells or the excitatory interneurons (EI), for the first time, in epileptic seizure generation using an extended neural mass model inspired by a thalamocortical model originally introduced by another research group. Applying bifurcation analysis on this modified model, we investigated the rich dynamics corresponding to the epileptic seizure onset and transition between interictal and ictal states caused by EI connectivity to other cell types. Our results indicate that the transition between interictal and ictal states (preictal signal) corresponds to a supercritical Hopf bifurcation, and thus, the extended model suggests that before seizure onset, the amplitude and frequency of neural activities gradually increase. Moreover, we showed that (1) the altered function of GABAergic and glutamatergic receptors of EI can cause seizure, and (2) the pathway between the thalamic relay nucleus and EI facilitates the transition from interictal to ictal activity by decreasing the preictal period. Thereafter, we considered both sensory and cortical periodic inputs to study model responses to various harmonic stimulations. Bifurcation analysis of the model, in this case, suggests that the initial state of the model might be the main cause for the transition between interictal and ictal states as the stimulus frequency changes. The extended thalamocortical model shows also that the amplitude jump phenomenon and non-linear resonance behavior result from the preictal state of the modified model. These results can be considered as a step forward to a deeper understanding of the mechanisms underlying the transition from normal activities to epileptic activities.

Eslicarbazepine Acetate as Adjunctive Therapy for Primary Generalized Tonic-Clonic Seizures in Adults: A Prospective Observational Study

BACKGROUND

Eslicarbazepine acetate (ESL), a novel sodium channel blocker, is approved for mono and adjunctive treatment of partial epileptic seizures with or without secondary generalization. Its efficacy in primary generalized seizures has not yet been evaluated.

OBJECTIVE

To evaluate the efficacy and safety of ESL in primary generalized tonic-clonic seizures (PGTCS) in an observational study.

METHODS

The data were collected from a prospective population-based register. Effectiveness was measured as relative reduction in standardized seizure frequency (SSF), responder rate (≥ 50% reduction in SSF), and seizure freedom rate at 6 and 12 months after initiation of ESL. Safety and tolerability were evaluated using patients' diaries.

RESULTS

Fifty-six adult patients with PGTCS were treated with ESL as adjunctive therapy. Of these, 30.4% (n = 17) had myoclonic seizures in addition to PGTCS. The retention rate after 12 months was 80.4% (n = 45). After initiating ESL therapy, reduction in SSF for PGTCS on ESL was 56.0% after 6 months and 56.9% after 12 months (p < 0.01), whereas myoclonic seizures did not show any significant improvement in frequency. The responder rate for PGTCS was 64.3% after 6 months and 66.1% after 12 months, and seizure freedom was achieved in 32.1% and 35.7%, respectively. Forty-three patients (73.2%) reported no side effects. Among the reported side effects of ESL therapy, headache (7.1%), dizziness (8.9%), tiredness (7.1%), nausea (5.4%), and hyponatremia (5.4%) were the most prevalent.

CONCLUSIONS

Our data suggest that ESL may provide additional benefits in the treatment of patients with PGTCS and motivate randomized controlled trials in this indication.

Genetic generalized epilepsy and generalized onset seizures with focal evolution (GOFE)

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Generalized Onset with Focal Evolution seizure (GOFE) is a rare pattern defined by an evolution from generalized onset to focal activity during the same ictal event.

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Despite focal clinical features, GOFE refers to Idiopathic Generalized Epilepsy.

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We found the use of broad-spectrum anti-seizure medications (ASM) was most efficacious in our case series of patients with GOFE.

“Generalized Onset with Focal Evolution” (GOFE) is an underrecognized seizure type defined by an evolution from generalized onset to focal activity during the same ictal event. We aimed to discuss electroclinical aspects of GOFE and to emphasize its link with Genetic Generalized Epilepsy (GGE).

Patients were identified retrospectively over 10 years, using the video-EEG data base from the Epilepsy Unit of Strasbourg University Hospital. GOFE was defined, as previously reported, from an EEG point of view with an evolution from generalized onset to focal activity during the same ictal event.

Three male patients with GOFE were identified among 51 patients with recorded tonic-clonic seizures. Ages at onset of seizures were 13, 20 and 22 years. Focal clinical features (motor asymmetric phenomenology) could be identified. EEG showed generalized interictal discharges with focal evolution of various localization. Four seizures were recorded characterized by 2–3 s of generalized abnormalities followed by focal (parieto-occipital or frontal) discharges. There were initially uncontrolled seizures with lamotrigine, but all patients reported a good outcome with valproate monotherapy.

We emphasize that GOFE presents many similarities with GGE. Recognition of the GOFE entity could bring a therapeutic interest avoiding misdiagnosis of focal epilepsy and consequently inappropriate use of narrow spectrum anti-seizure medicine.

Reconsidering the role of selective sodium channel blockers in genetic generalized epilepsy

OBJECTIVE

Selective sodium channel blockers (SSCBs) have a limited use in genetic generalized epilepsy (GGE), due to their well-known risk of seizure worsening. Although their therapeutic potential in GGE has been suggested by recent evidence, electro-clinical data supporting their prescription are lacking. We aimed to investigate SSCB safety and effectiveness in a GGE cohort.

METHODS

Subjects who received SSCBs and had ≥5-year follow-up were enrolled. Lamotrigine was excluded from analysis due to its broader pharmacodynamic spectrum and its better-documented efficacy in GGE.

RESULTS

Fifty-six patients (median follow-up 28.5 years) were included. The most used SSCB was carbamazepine in 40 subjects. At the last medical observation, only 9 subjects were still receiving SSCBs. The occurrence of generalized polyspike-wave discharges (GPSWDs) predicted reduced SSCB retention in Cox multivariate analysis. A seizure reduction ≥50% occurred in 53.5% (30/56) of subjects when considering all seizure types; however, the proportion of responders increased to 67.9% when considering only generalized tonic-clonic seizures (GTCS). GPSWDs were significantly associated with a reduced response rate, whereas GGE with GTCS only syndrome with a better outcome. The switch from SSCBs to antiseizure medications licensed for GGE improved seizure control in 65% of patients. Seizure worsening was reported in 5/56 patients; juvenile myoclonic epilepsy and a family history of epilepsy were significantly associated with seizure aggravation.

CONCLUSION

SSCBs appeared effective on GTCS, but epilepsy aggravation and unsatisfactory control of other seizure types were not uncommon. Our study contributes to identifying new clinical and EEG variables associated with SSCB effectiveness and safety which may help neurologists in patients' management.

Efficacy of Lacosamide in a Patient with Refractory Generalized Epilepsy Based on Video Electroencephalography

A 20-year-old man with drug-resistant generalized epilepsy (GE) was admitted for video electroencephalography (vEEG) monitoring under treatment with multiple antiepileptic drugs, including levetiracetam (3,000 mg/day), valproic acid (800 mg/day), and lacosamide (LCM) (100 mg/day). No seizures were noted after the withdrawal of levetiracetam. However, after the withdrawal of LCM, atypical absence seizures with a 2- to 2.5-Hz generalized spike and wave complex frequently appeared, followed by subsequent generalized-onset tonic-clonic seizures. After re-administration of LCM, the seizures and epileptic discharges clearly disappeared. Subsequent LCM titration was successful in achieving a seizure-free status. Our vEEG results suggest that LCM may be a worthwhile antiepileptic drug adjunct in refractory GE patients without a risk of worsening absence seizures.

Epilepsy: A Clinical Overview

The diagnosis and treatment of seizures and epilepsy is a common task of the physician. Approximately 1 in 10 people will have a seizure during their lifetime. Epilepsy is the tendency to have unprovoked seizures. Epilepsy is the fourth most common neurological disorder and affects 1 in 26 people in the United States and 65 million people worldwide. Evaluation of a patient presenting with a seizure involves excluding an underlying neurologic or medical condition, classifying the seizure type and determining if the patient has epilepsy. Proper treatment requires accurate diagnosis of the epilepsy type and syndrome and use of a medication that is effective and without adverse effects. Most patients can achieve complete seizure control with medication, but if medication is unsuccessful, surgical treatment can be an option. Special situations in the care of people with epilepsy include status epilepticus, women with epilepsy, the older adult, and safety issues.

Altered Neurotransmitter Expression in the Corticothalamocortical Network of an Absence Epilepsy Model with impaired Feedforward Inhibition

The episodes of brief unconsciousness in patients with childhood absence epilepsy are a result of corticothalamocortical circuitry dysfunction. This dysfunction may arise from multifactorial mechanisms in patients from different genetic backgrounds. In previous studies using the epileptic stargazer mutant mouse, which experience frequent absence seizures, we reported a deficit in AMPAR-mediated feed-forward inhibition of parvalbumin-containing (PV⁺) interneurons. Currently, in order to determine the downstream effects of this impairment on neurotransmitter expression, we performed HPLC of tissue lysates and post-embedding electron microscopy from the cortical and thalamic regions. We report region-specific alterations in GABA expression, but not of glutamate, and most prominently at PV⁺ synaptic terminals. These results suggest that impaired feed forward inhibition may occur via reduced activation of these interneurons and concomitant decreased GABAergic signaling. Further investigations into GABAergic control of corticothalamocortical network activity could be key in our understanding of absence seizure pathogenesis.

Experimental Therapeutic Strategies in Epilepsies Using Anti-Seizure Medications

Epilepsies are among the most common neurological problems. The disease burden in patients with epilepsy is significantly high, and epilepsy has a huge negative impact on patients' quality of life with epilepsy and their families. Anti-seizure medications are the mainstay treatment in patients with epilepsy, and around 70% of patients will ultimately control with a combination of at least two appropriately selected anti-seizure medications. However, in one-third of patients, seizures are resistant to drugs, and other measures will be needed. The primary goal in using experimental therapeutic medication strategies in patients with epilepsy is to prevent recurrent seizures and reduce the rate of traumatic events that may occur during seizures. So far, various treatments using medications have been offered for patients with epilepsies, which have been classified according to the type of epilepsy, the effectiveness of the medications, and the adverse effects. Medications such as Levetiracetam, valproic acid, and lamotrigine are at the forefront of these patients' treatment. Epilepsy surgery, neuro-stimulation, and the ketogenic diet are the main measures in patients with medication-resistant epilepsies. In this paper, we will review the therapeutic approach using anti-seizure medications in patients with epilepsy. However, it should be noted that some of these patients still do not respond to existing treatments; therefore, the limited ability of current therapies has fueled research efforts for the development of novel treatment strategies. Thus, it seems that in addition to surgical measures, we should look for more specific agents that have less adverse events and have a greater effect in stopping seizures.

The Role and Controversies of Electroencephalogram in Focal versus Generalized Epilepsy

As early in 1935, Gibbs et al described electroencephalogram (EEG) features of large slow waves seen in “petit mal” seizures and change in background rhythm to a higher frequency, greater amplitude pattern in “grand mal” seizures. Studies have shown many typical EEG features in focal onset as well as generalized epilepsies.2 3 It is usually easy to delineate focal epilepsy cases when EEG onset of seizures is clear as seen in Benign focal epileptiform discharges of childhood.4 However, it is not uncommon to see cases where epileptiform discharges are not very clear. For example, there can be secondary bilateral synchrony or generalized onset of epileptiform discharges in some cases of focal epilepsy5 and nongeneralized EEG features is cases of generalized epilepsy like absence seizures.6

The awareness of occurrence of focal clinical and EEG features in generalized epilepsy is particularly important to help to select appropriate AEDs and also to avoid inappropriate consideration for epilepsy surgery.7 Lüders et al8 have shown that multiple factors like electroclinical seizure evolution, neuroimaging (both functional and anatomical) have to be analyzed in depth before defining an epileptic syndrome. Here, we are providing few examples of different situations where it is still mysterious to figure out focal onset seizures with secondary generalization versus primary generalized epilepsy.

Risk factors of paradoxical reactions to anti-seizure medication in genetic generalized epilepsy

This study aimed at providing valid estimates for the risk of clinically relevant seizure aggravation by recommended anti-seizure medications in patients with Genetic Generalized Epilepsy (GGE). To this aim, treatment response, side effects and paradoxical reactions to anti-seizure treatment were retrospectively assessed in a near-population based cohort comprising 471 adult GGE patients. A total of 1046 treatment attempts were analyzed (lamotrigine: 351, valproic acid: 295, levetiracetam: 249, primidone/phenobarbital: 94, zonisamide: 57). Under lamotrigine, seizure aggravation was observed in 15 patients (two patients during levetiracetam, one patient during zonisamide, none during phenobarbital and valproic acid). All but two patients with paradoxical reactions to lamotrigine were diagnosed with juvenile myoclonic epilepsy (JME), otherwise, the clinical and electroencephalographic characteristics of patients with paradoxical reactions did not differ. At treatment start, the estimated risk of a paradoxical reaction to lamotrigine was 7.9 % in JME patients (n = 190). For all GGE patients (incl. JME), the estimated risk of clinically relevant seizure aggravation under treatment with lamotrigine was 3.7 % (1.8 % for zonisamide and 0.8 % for levetiracetam). In conclusion, clinical significant aggravation of seizure frequency is common in lamotrigine-treated JME patients but rare in patients with other GGE subsyndromes or under treatment with other recommended anti-seizure medication.

Impact of predictive, preventive and precision medicine strategies in epilepsy

Over the last decade, advances in genetics, neuroimaging and EEG have enabled the aetiology of epilepsy to be identified earlier in the disease course than ever before. At the same time, progress in the study of experimental models of epilepsy has provided a better understanding of the mechanisms underlying the condition and has enabled the identification of therapies that target specific aetiologies. We are now witnessing the impact of these advances in our daily clinical practice. Thus, now is the time for a paradigm shift in epilepsy treatment from a reactive attitude, treating patients after the onset of epilepsy and the initiation of seizures, to a proactive attitude that is more broadly integrated into a 'P4 medicine' approach. This P4 approach, which is personalized, predictive, preventive and participatory, puts patients at the centre of their own care and, ultimately, aims to prevent the onset of epilepsy. This aim will be achieved by adapting epilepsy treatments not only to a given syndrome but also to a given patient and moving from the usual anti-seizure treatments to personalized treatments designed to target specific aetiologies. In this Review, we present the current state of this ongoing revolution, emphasizing the impact on clinical practice.

Development and validation of a predictive model of drug-resistant genetic generalized epilepsy

OBJECTIVE

To develop and validate a clinical prediction model for antiepileptic drug (AED)-resistant genetic generalized epilepsy (GGE).

METHOD

We performed a case-control study of patients with and without drug-resistant GGE, nested within ongoing longitudinal observational studies of AED response at 2 tertiary epilepsy centers. Using a validation dataset, we tested the predictive performance of 3 candidate models, developed from a training dataset. We then tested the candidate models' predictive ability on an external testing dataset.

RESULTS

Of 5,189 patients in the ongoing longitudinal study, 121 met criteria for AED-resistant GGE and 468 met criteria for AED-responsive GGE. There were 66 patients with GGE in the external dataset, of whom 17 were cases. Catamenial epilepsy, history of a psychiatric condition, and seizure types were strongly related with drug-resistant GGE case status. Compared to women without catamenial epilepsy, women with catamenial epilepsy had about a fourfold increased risk for AED resistance. The calibration of 3 models, assessing the agreement between observed outcomes and predictions, was adequate. Discriminative ability, as measured with area under the receiver operating characteristic curve (AUC), ranged from 0.58 to 0.65.

CONCLUSION

Catamenial epilepsy, history of a psychiatric condition, and the seizure type combination of generalized tonic clonic, myoclonic, and absence seizures are negative prognostic factors of drug-resistant GGE. The AUC of 0.6 is not consistent with truly effective separation of the groups, suggesting other unmeasured variables may need to be considered in future studies to improve predictability.

Dealing with the storm: An overview of seizure precipitants and spontaneous seizure worsening in drug-resistant epilepsy

In drug-resistant epilepsy, periods of seizure stability may alternate with abrupt worsening, with frequent seizures limiting the individual's independence and physical, social, and psychological well-being. Here, we review the literature focusing on different clinical scenarios related to seizure aggravation in people with drug-resistant epilepsy. The role of antiseizure medication (ASM) changes is examined, especially focusing on paradoxical seizure aggravation after increased treatment. The external provocative factors that unbalance the brittle equilibrium of seizure control are reviewed, distinguishing between unspecific triggering factors, specific precipitants, and 'reflex' mechanisms. The chance of intervening surgical or medical conditions, including somatic comorbidities and epilepsy surgery failure, causing increased seizures is discussed. Spontaneous exacerbation is also explored, emphasizing recent findings on subject-specific circadian and ultradian rhythms. Awareness of external precipitants and understanding the subject-specific spontaneous epilepsy course may allow individuals to modify their lifestyles. It also allows clinicians to counsel appropriately and to institute suitable medical treatment to avoid sudden loss of seizure control.

Role of observational studies in supporting extrapolation of efficacy data from adults to children with epilepsy - A systematic review of the literature using lacosamide as an example

Extrapolation of efficacy data from adults to children is accepted for focal epilepsy - the antiepileptic drug, lacosamide, has been approved for the treatment of children ≥4 years of age on this basis. Since many small-scale, open-label studies are reported in the literature before approval, a systematic review was conducted to ascertain whether results of these could be used to support extrapolation in epilepsy in the future. In the absence of randomised trials, a second analysis was conducted for reports on lacosamide use in adults with generalized epilepsies. Twenty-seven articles were included in the paediatric qualitative synthesis, and 14 in the adult. Paediatric studies were analysed separately based on seizure type: focal, generalised and mixed. In focal epilepsy, safety and seizure-related findings mirrored those observed in the adult Phase II/III trials, supporting the feasibility of data extrapolation. Few studies reported outcomes in children with epilepsies associated with generalised seizures, and those that included children with different seizure types, mostly did not provide results separately. Lacosamide treatment appeared beneficial for children and adults experiencing tonic-clonic and myoclonic seizures. Reports of seizure aggravation were inconsistent and, in many cases, could not be clearly attributed to lacosamide. Given the absence of sufficient data, evidence for the feasibility of extrapolation was not as clear-cut as it was in focal epilepsy. These results highlight the complexities of conducting trials in the generalised epilepsy setting, and the importance of studies in the real-life setting and of analysing efficacy data per generalized seizure type and syndrome.

Smartphone EEG and remote online interpretation for children with epilepsy in the Republic of Guinea: Quality, characteristics, and practice implications

PURPOSE

Children with epilepsy in low-income countries often go undiagnosed and untreated. We examine a portable, low-cost smartphone-based EEG technology in a heterogeneous pediatric epilepsy cohort in the West African Republic of Guinea.

METHODS

Children with epilepsy were recruited at the Ignace Deen Hospital in Conakry, 2017. Participants underwent sequential EEG recordings with an app-based EEG, the Smartphone Brain Scanner-2 (SBS2) and a standard Xltek EEG. Raw EEG data were transmitted via Bluetooth^™ connection to an Android^™ tablet and uploaded for remote EEG specialist review and reporting via a new, secure web-based reading platform, crowdEEG. The results were compared to same-visit Xltek 10-20 EEG recordings for identification of epileptiform and non-epileptiform abnormalities.

RESULTS

97 children meeting the International League Against Epilepsy's definition of epilepsy (49 male; mean age 10.3 years, 29 untreated with an antiepileptic drug; 0 with a prior EEG) were enrolled. Epileptiform discharges were detected on 21 (25.3%) SBS2 and 31 (37.3%) standard EEG recordings. The SBS2 had a sensitivity of 51.6% (95%CI 32.4%, 70.8%) and a specificity of 90.4% (95%CI 81.4%, 94.4%) for all types of epileptiform discharges, with positive and negative predictive values of 76.2% and 75.8% respectively. For generalized discharges, the SBS2 had a sensitivity of 43.5% with a specificity of 96.2%.

CONCLUSIONS

The SBS2 has a moderate sensitivity and high specificity for the detection of epileptiform abnormalities in children with epilepsy in this low-income setting. Use of the SBS2+crowdEEG platform permits specialist input for patients with previously poor access to clinical neurophysiology expertise.

Safety and tolerability profile of new antiepileptic drug treatment in children with epilepsy

INTRODUCTION

Treatment of pediatric epilepsy requires a careful evaluation of the safety and tolerability profile of antiepileptic drugs (AEDs) to avoid or minimize as much as possible adverse events (AEs) on various organs, hematological parameters, and growth, pubertal, motor, cognitive and behavioral development.

AREAS COVERED

Treatment-emergent AEs (TEAEs) reported in the literature 2000-2018 regarding second- and third-generation AEDs used in the pediatric age, with exclusion of the neonatal period that exhibits specific peculiarities, have been described on the basis of their frequency, severity/tolerability, and particular association with a given AED.

EXPERT OPINION

Somnolence/sedation and behavioral changes, like irritability and nervousness, are among the most commonly observed TEAEs associated with almost all AEDs. Lamotrigine, Gabapentin, Oxcarbazepine, and Levetiracetam appear to be the best-tolerated AEDs with a ≤2% withdrawal rate, while Tiagabine and Everolimus are discontinued in up to >20% of the patients because of intolerable TEAEs. For some AEDs, literature data are scanty to draw a high-level evidence on their safety and tolerability profile. The reasons are: insufficient population size, short duration of treatments, or lack of controlled trials. A future goal is that of identifying clearer, easier, and more homogeneous methodological strategies to facilitate AED testing in pediatric populations.

Long-term negative impact of an inappropriate first antiepileptic medication on the efficacy of a second antiepileptic medication in mice

Childhood absence epilepsy (CAE) is one of the most frequent epilepsies in infancy. The first-line recommended therapy for CAE is based on the prescription of the narrow-spectrum ethosuximide and the broad-spectrum valproic acid, which have similar efficacy in the first 12 months. Nevertheless, some antiepileptic drugs (AEDs) may worsen seizure duration and type in this syndrome. In line with this, we have encountered a case of identical twins with CAE and early exposure to different antiseizure drugs leading to divergent outcomes. From this, we hypothesized that the first AED to treat CAE may determine the long-term prognosis, especially in the developing brain, and that some situations leading to drug resistance may be explained by use of an inappropriate first AED. Therefore, we investigated this hypothesis by using a genetic mouse model of absence epilepsy (BS/Orl). Mice received a first appropriate or inappropriate AED followed by the same appropriate AED. Our data demonstrate that an inappropriate first AED has a negative impact on the long-term efficacy of a second appropriate AED. This work supports the necessity to effectively diagnose epileptic syndromes prior to medication use, particularly in children, in order to prevent the deleterious effects of an inappropriate initial AED.

Lacosamide for refractory generalized tonic-clonic seizures of non-focal origin in clinical practice: A clinical and VEEG study

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7 of 9 patients with GGE reduced ≥ 50% their tonic–clonic seizure frequency on LCM.

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All 7 patients remained seizure free for > 1 year, and 2 of them for > 5 years.

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In 2 of the 9 patients, both with Juvenile Absence Epilepsy, absences aggravated.

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One aggravation consisted on a myoclonia and absence status, in a patient with no history of myoclonia.

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VEEG paralleled clinical improvement but didn't change in a case of absence worsening.

Update on pharmacotherapy of myoclonic seizures

INTRODUCTION

Myoclonic seizures are brief, involuntary muscular jerks arising from the central nervous system that can occur in different epilepsy syndromes, including idiopathic generalized epilepsies or the most severe group of epileptic encephalopathies. Valproate is commonly the first choice alone or in combination with some benzodiazepines or levetiracetam. However, more treatment options exist today as there is emerging evidence to support the efficacy of some newer antiepileptic drugs. In addition, of major importance remains avoidance of medications (e.g., carbamazepine, phenytoin) that may aggravate myoclonic seizures. This is an updated review on the available therapeutic options for treatment of myoclonic seizures. Areas covered: Key efficacy, tolerability and efficacy data are showed for different antiepileptic drugs with antimyoclonic effect, alone and/or in combination. Expert opinion: Pharmacological treatment of myoclonic seizures is based on clinical experience with little evidence from randomized clinical trials. Valproate, levetiracetam, and some benzodiazepines, are widely used. There is still insufficient evidence for the use of other antiseizure drugs, such as topiramate or zonisamide as monotherapy. Better understanding of pathophysiologic mechanisms of myoclonic epilepsies could yield great improvement in the treatment and quality of life of patients.

Generalized onset seizures with focal evolution (GOFE) - A unique seizure type in the setting of generalized epilepsy

PURPOSE

We report clinical and electrographic features of generalized onset seizures with focal evolution (GOFE) and present arguments for the inclusion of this seizure type in the seizure classification.

METHODS

The adult and pediatric Epilepsy Monitoring Unit databases at Vanderbilt Medical Center and Children's Hospital were screened to identify generalized onset seizures with focal evolution. We reviewed medical records for epilepsy characteristics, epilepsy risk factors, MRI abnormalities, neurologic examination, antiepileptic medications before and after diagnosis, and response to medications. We also reviewed ictal and interictal EEG tracings, as well as video-recorded semiology.

RESULTS

Ten patients were identified, 7 males and 3 females. All of the patients developed generalized epilepsy in childhood or adolescence (ages 3-15years). Generalized onset seizures with focal evolution developed years after onset in 9 patients, with a semiology concerning for focal seizures or nonepileptic events. Ictal discharges had a generalized onset on EEG, described as either generalized spike-and-wave and/or polyspike-and-wave discharges, or generalized fast activity. This electrographic activity then evolved to focal rhythmic activity most commonly localized to one temporal or frontal region; five patients had multiple seizures evolving to focal activity in different regions of both hemispheres. The predominant interictal epileptiform activity included generalized spike-and-wave and/or polyspike-and-wave discharges in all patients. Taking into consideration all clinical and EEG data, six patients were classified with genetic (idiopathic) generalized epilepsy, and four were classified with structural/metabolic (symptomatic) generalized epilepsy. All of the patients had modifications to their medications following discharge, with three becoming seizure-free and five responding with >50% reduction in seizure frequency.

CONCLUSION

Generalized onset seizures may occasionally have focal evolution with semiology suggestive of focal seizures, leading to a misdiagnosis of focal onset. This unique seizure type may occur with genetic as well as structural/metabolic forms of epilepsy. The identification of this seizure type may help clinicians choose appropriate medications, avoiding narrow spectrum agents known to aggravate generalized onset seizures.

Shift in interictal relative gamma power as a novel biomarker for drug response in two mouse models of absence epilepsy

OBJECTIVE

Two monogenic mouse models of childhood absence epilepsy, stargazer and tottering, differ strikingly in their response to N-methyl-d-aspartate (NMDA) receptor blockade. We sought to evaluate the change in interictal relative gamma power as a reliable biomarker for this gene-linked antiepileptic drug (AED) response.

METHODS

The effects of AEDs on absolute and relative (to the total) power of frequencies between 2 and 300 Hz were analyzed within the interictal electroencephalogram (EEG) and correlated with antiseizure efficacy in awake behaving stargazer, tottering, and wild-type (WT) littermate control mice.

RESULTS

At baseline, we found a significant absolute as well as relative augmentation of 16-41 Hz power in stargazer compared to both tottering and WT mice. In stargazer, the NMDA receptor-antagonist MK-801 (0.5 mg/kg) paradoxically exacerbates absence seizures but normalizes the augmented beta/gamma band of power to WT levels, suggesting that the elevation in 16- to 41-Hz power is an NMDA receptor-mediated network property. In contrast, ethosuximide (200 mg/kg) and 4-aminopyridine (2.5 mg/kg) reduce seizure activity and increase relative power within the gamma range in both stargazer and tottering mice. Intraperitoneal saline injection had no significant effect on either seizure frequency or relative gamma power. Along with results using carbamazepine and flupirtine, there was a strong inverse relationship between relative change in seizure duration and change in peak relative gamma power (r(2) = 0.726).

SIGNIFICANCE

In these two models of absence epilepsy, drugs that reduce relative gamma power are associated with an increase in seizures, whereas drugs that augment relative gamma power reduce seizures. Therefore, drug-induced modulation of relative gamma power may serve as a biomarker for AED efficacy in absence epilepsy. Given the relationship between gamma power and fast-spiking interneurons, these results also suggest that a drug's effect may in part be determined by its impact on specific inhibitory networks.

Synaptic changes in GABAA receptor expression in the thalamus of the stargazer mouse model of absence epilepsy

Absence seizures are known to result from disturbances within the cortico-thalamocortical network, which remains partially synchronous under normal conditions but switches to a state of hypersynchronicity and hyperexcitability during absence seizures. There is evidence to suggest that impaired GABAergic inhibitory function within the thalamus could contribute to the generation of hypersynchronous oscillations in some animal models of absence epilepsy. Recently, we demonstrated region-specific alterations in the tissue expression level of GABAA receptors (GABA(A)Rs) α1 and β2 subunits within the thalamus of the stargazer mouse model of absence epilepsy. In the present study we investigated whether changes in these subunits also occur at synapses in the ventral posterior (VP) complex where they are components of phasic GABA(A)R receptors. Postembedding immunogold cytochemistry and electron microscopy were used to analyze the relative synaptic expression of α1 and β2 subunits in the VP thalamic region in epileptic stargazer mice compared to their non-epileptic littermates. We show that there is a significant increase in expression of α1 and β2 subunits (53.6% and 45.8%, respectively) at synapses in the VP region of stargazers, indicative of an increase in phasic GABA(A)Rs at thalamocortical (TC) relay neurons. Furthermore, we investigated whether tissue expression of GABA(A)R subunits α4 and δ, which constitute part of tonic GABA(A)Rs in the VP region, is altered in the stargazer mouse. Semi-quantitative Western blotting showed a significant increase in GABA(A)R α4 and δ subunits in the VP region of stargazer thalamus, which would indicate an increase in tonic GABA(A)R expression. Our findings show that there are changes in the levels of both phasic and tonic GABA(A)Rs in the VP thalamus; altered GABAergic inhibition within the VP could be one of many mechanisms contributing to the generation of absence seizures in this model.

A critical evaluation of the gamma-hydroxybutyrate (GHB) model of absence seizures

Typical absence seizures (ASs) are nonconvulsive epileptic events which are commonly observed in pediatric and juvenile epilepsies and may be present in adults suffering from other idiopathic generalized epilepsies. Our understanding of the pathophysiological mechanisms of ASs has been greatly advanced by the availability of genetic and pharmacological models, in particular the γ-hydroxybutyrate (GHB) model which, in recent years, has been extensively used in studies in transgenic mice. GHB is an endogenous brain molecule that upon administration to various species, including humans, induces not only ASs but also a state of sedation/hypnosis. Analysis of the available data clearly indicates that only in the rat does there exist a set of GHB-elicited behavioral and EEG events that can be confidently classified as ASs. Other GHB activities, particularly in mice, appear to be mostly of a sedative/hypnotic nature: thus, their relevance to ASs requires further investigation. At the molecular level, GHB acts as a weak GABA-B agonist, while the existence of a GHB receptor remains elusive. The pre- and postsynaptic actions underlying GHB-elicited ASs have been thoroughly elucidated in thalamus, but little is known about the cellular/network effects of GHB in neocortex, the other brain region involved in the generation of ASs.

Paradoxical proepileptic response to NMDA receptor blockade linked to cortical interneuron defect in stargazer mice

Paradoxical seizure exacerbation by anti-epileptic medication is a well-known clinical phenomenon in epilepsy, but the cellular mechanisms remain unclear. One possibility is enhanced network disinhibition by unintended suppression of inhibitory interneurons. We investigated this hypothesis in the stargazer mouse model of absence epilepsy, which bears a mutation in stargazin, an AMPA receptor trafficking protein. If AMPA signaling onto inhibitory GABAergic neurons is impaired, their activation by glutamate depends critically upon NMDA receptors. Indeed, we find that stargazer seizures are exacerbated by NMDA receptor blockade with CPP (3-[(R)-2-carboxypiperazin-4-yl]-prop-2-enyl-1-phosphonic acid) and MK-801, whereas other genetic absence epilepsy models are sensitive to these antagonists. To determine how an AMPA receptor trafficking defect could lead to paradoxical network activation, we analyzed stargazin and AMPA receptor localization and found that stargazin is detected exclusively in parvalbumin-positive (PV ⁺) fast-spiking interneurons in somatosensory cortex, where it is co-expressed with the AMPA receptor subunit GluA4. PV ⁺ cortical interneurons in stargazer show a near twofold decrease in the dendrite:soma GluA4 expression ratio compared to wild-type (WT) littermates. We explored the functional consequence of this trafficking defect on network excitability in neocortical slices. Both NMDA receptor antagonists suppressed 0 Mg ²⁺-induced network discharges in WT but augmented bursting in stargazer cortex. Interneurons mediate this paradoxical response, since the difference between genotypes was masked by GABA receptor blockade. Our findings provide a cellular locus for AMPA receptor-dependent signaling defects in stargazer cortex and define an interneuron-dependent mechanism for paradoxical seizure exacerbation in absence epilepsy.

Antiepileptic drug treatment: new drugs and new strategies

PURPOSE OF REVIEW

Selection of the ideal antiepileptic drug (AED) for an individual patient can be a daunting process. Choice of treatment should be based on several factors, including but not limited to epilepsy classification, AED mechanism of action, AED side-effect profile, and drug interactions. Special consideration must be given to populations such as women, older adults, patients with other medical comorbidities, and patients who are newly diagnosed.

RECENT FINDINGS

Head-to-head trials between AEDs in newly diagnosed patients rarely demonstrate that one AED is more or less effective. The second-generation drugs, lamotrigine, topiramate, oxcarbazepine, zonisamide, and levetiracetam, have undergone head-to-head trials confirming similar efficacy and equal or better tolerability than standard drugs in focal epilepsy.

SUMMARY

A thoughtful approach to the AED selection process must factor in data from clinical AED trials as well as a variety of patient characteristics and confounding factors. When neurologists apply an individualized approach to AED drug selection for their patients, they can find an effective and well-tolerated drug for most patients.

When one plus one makes three: the quest for rational antiepileptic polytherapy with supraadditive anticonvulsant efficacy

The experimental and clinical evidence in support of "rational polytherapy" is sparse, and to date, no clear evidence-based indications can be made to help physicians in their choice of a specific drug combination against specific forms of epilepsy. This article briefly reviews the data available in the literature and obtained from studies conducted in humans to evaluate which main AED combinations might possess supraadditive, synergistic effects in terms of efficacy, with infraadditive toxicity. By far, the most documented association resulting in supraadditive anticonvulsant effects against focal seizures is that of VPA and LTG. There are some indications that combinations of drugs with different primary mechanisms of action may be more effective than combining drugs with the same mechanisms of action. However, further animal and human research studies that focus both on toxicity and anticonvulsant effects of various combinations of AEDs are required.

The role of magnesium sulfate in prevention of seizures induced by pentylenetetrazole in rats

Magnesium sulfate (MgSO₄) has been used to prevent seizures in eclampsia. This study examined the central effects of MgSO₄ on different types of pentylenetetrazole (PTZ)-induced seizures. Male Wistar rats were submitted to intracerebroventricular (ICV) administration of MgSO₄ at different doses followed by intraperitoneal administration of PTZ. The latency to the onset of the first seizure induced by PTZ was significantly increased by ICV administration of MgSO₄ at a dose of 100 µg compared to the control treatment. In addition, the total period during which animals presented with seizures was significantly reduced at this dose of MgSO₄. Furthermore, the latency to the onset of the first partial complex seizure was significantly increased by the lowest dose of MgSO₄. However, a high dose of MgSO₄ had no effect or even potentiated the effect of PTZ. These results suggest that, depending on the dose, MgSO₄ may be important in prevention of epileptic seizures.

Ethosuximide modifies network excitability in the rat entorhinal cortex via an increase in GABA release

Ethosuximide is the drug of choice for treating generalized absence seizures, but its mechanism of action is still a matter of debate. It has long been thought to act by disrupting a thalamic focus via blockade of T-type channels and, thus, generation of spike-wave activity in thalamocortical pathways. However, there is now good evidence that generalized absence seizures may be initiated at a cortical focus and that ethosuximide may target this focus. In the present study we have looked at the effect ethosuximide on glutamate and GABA release at synapses in the rat entorhinal cortex in vitro, using two experimental approaches. Whole-cell patch-clamp studies revealed an increase in spontaneous GABA release by ethosuximide concurrent with no change in glutamate release. This was reflected in studies that estimated global background inhibition and excitation from intracellularly recorded membrane potential fluctuations, where there was a substantial rise in the ratio of network inhibition to excitation, and a concurrent decrease in excitability of neurones embedded in this network. These studies suggest that, in addition to well-characterised effects on ion channels, ethosuximide may directly elevate synaptic inhibition in the cortex and that this could contribute to its anti-absence effects. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Seizure aggravation by antiepileptic drugs

Seizure aggravation by antiepileptic drugs (AEDs) is an overestimated phenomenon. While it undoubtedly occurs, the quality of evidence in most published reports is poor. Although seizure aggravation can be examined in clinical trials in the same way as seizure improvement, this is rarely done. Before concluding that an increase in seizures after the introduction of a new drug represents pharmacodynamic aggravation, alternative explanations should be explored. These include spontaneous fluctuation of seizure frequency, the presence of known seizure aggravators (such as sleep deprivation, alcohol, and psychotropic medications), progression of epilepsy, the development of drug resistance, and replacement of a partially effective drug with a less effective drug. The risk of incorrectly blaming a drug for a deterioration in seizures can be minimized by establishing baseline seizure frequency over a period long enough to encompass the extremes of seizure fluctuation and by educating the patient that a temporal relationship may not be a causal relationship. When feasible, the patient should continue the drug long enough to establish if the deterioration is transient. If the drug is stopped, rechallenge should be considered. The risk of seizure aggravation can be minimized by accurate diagnosis of the epilepsy syndrome and appropriate choice of AED.

Intravenous levetiracetam in critically ill children with status epilepticus or acute repetitive seizures

OBJECTIVE

Intravenous (IV) levetiracetam (LEV) is approved for use in patients older than 16 years and may be useful in critically ill children, although there is little data available regarding pharmacokinetics. We aim to investigate the safety, an appropriate dosing, and efficacy of IV LEV in critically ill children.

DESIGN

We describe a cohort of critically ill children who received IV LEV for status epilepticus, including refractory or nonconvulsive status, or acute repetitive seizures.

RESULTS

There were no acute adverse effects noted. Children had temporary cessation of ongoing refractory status epilepticus, termination of ongoing nonconvulsive status epilepticus, cessation of acute repetitive seizures, or reduction in epileptiform discharges with clinical correlate.

CONCLUSIONS

IV LEV was effective in terminating status epilepticus or acute repetitive seizures and well tolerated in critically ill children. Further study is needed to elucidate the role of IV LEV in critically ill children.

Topiramate and zonisamide prevent paradoxical intoxication induced by carbamazepine and phenytoin

The mechanisms of paradoxical aggravation of epileptic seizures induced by selected antiepileptic drugs (AEDs) remain unclear. The present study addressed this issue by determining the seizure-threshold doses of carbamazepine (CBZ) and phenytoin (PHT), as well the dose-dependent effects of CBZ, PHT, and carbonic anhydrase-inhibiting AEDs, acetazolamide (AZM), topiramate (TPM), and zonisamide (ZNS), on neurotransmitter release in rat hippocampus. The dose-dependent effects of AEDs on hippocampal extracellular levels of glutamate (Glu), GABA, norepinephrine (NE), dopamine (DA), and serotonin (5-HT) were determined by microdialysis with high-speed and high-sensitive extreme liquid chromatography. Proconvulsive effects of AEDs were determined by telemetric-electrocorticography. Therapeutically relevant doses of AZM, CBZ, TPM, and ZNS increased hippocampal extracellular levels of GABA, NE, DA, and 5-HT, while PHT had no effect. Supratherapeutic doses of AZM, CBZ, PHT, TPM, and ZNS decreased extracellular levels of GABA, NE, DA, and 5-HT, without affecting Glu levels. Toxic doses of CBZ and PHT produced seizures (paradoxical intoxication), markedly increasing all transmitter levels, but TPM and ZNS even at toxic doses did not produce seizure. Co-administration experiments showed that therapeutically relevant doses of CBZ or PHT reduced the seizure-threshold doses of PHT or CBZ, respectively. In contrast, therapeutically relevant doses of AZM, TPM, and ZNS elevated the seizure-threshold doses of CBZ and PHT. These results suggested that blockade of high percentage of the population of voltage-dependent sodium channels by CBZ and PHT might be important in inducing paradoxical intoxication/reaction, and that inhibition of carbonic anhydrase inhibits this effect. TPM and ZNS are candidate first-choice agents in treatment of epilepsy when first-line AEDs are ineffective.

Lamotrigine overdose associated with generalised seizures

This report describes the occurrence of generalised seizures in a 42-year-old woman who presented to hospital after deliberate lamotrigine overdose. Seizure activity was promptly terminated after intravenous benzodiazepine administration, and the patient subsequently made a complete recovery. Serum lamotrigine concentration was 30 mg/l at 1.3 h post-ingestion, which is substantially higher than the therapeutic reference range; the estimated elimination half life was 18.3 h. This case reminds us that lamotrigine toxicity may provoke generalised seizures in susceptible individuals.