Dravet syndrome (DS) is a severe epilepsy syndrome that starts within the first year of life. In ... more Dravet syndrome (DS) is a severe epilepsy syndrome that starts within the first year of life. In a clinical study, add-on treatment with fenfluramine, a potent 5hydroxytryptamine (5-HT) releaser activating multiple 5-HT receptor subtypes, made 70% of DS children seizure free. Others and we recently confirmed the efficacy of fenfluramine as an antiepileptiform compound in zebrafish models of DS. By using a large set of subtype selective agonists, in this study we examined which 5-HT receptor subtypes can be targeted to trigger antiseizure effects in homozygous scn1Lab −/− mutant zebrafish larvae that recapitulate DS well. We also provide evidence that zebrafish larvae express the orthologues of all human 5-HT receptor subtypes. Using an automated larval locomotor behavior assay, we were able to show that selective 5-HT 1D-, 5-HT 1E-, 5-HT 2A-, 5-HT 2C-, and 5-HT 7-agonists significantly decreased epileptiform activity in the mutant zebrafish at 7 days post fertilization (dpf). By measuring local field potentials in the zebrafish larval forebrain, we confirmed the antiepileptiform activity of the 5-HT 1D-, 5-HT 2C-, and especially the 5-HT 2A-agonist. Interestingly, we also found a significant decrease of serotonin in the heads of homozygous scn1Lab −/− mutants as compared to the wild type zebrafish, which suggest that neurochemical defects might play a crucial role in the pathophysiology of DS. Taken together, our results emphasize the high conservation of the serotonergic receptors in zebrafish larvae. Modulating certain serotonergic receptors was shown to effectively reduce seizures. Our findings therefore open new avenues for the development of future novel DS therapeutics.
Dravet syndrome (DS) is a severe genetic epileptic encephalopathy with onset during the first yea... more Dravet syndrome (DS) is a severe genetic epileptic encephalopathy with onset during the first year of life. Zebrafish models recapitulating human diseases are often used as drug discovery platforms, but also for drug repurposing testing. It was recently shown that pharmacological modulation of three serotonergic (5-HT) receptors (5-HT 1D , 5-HT 2C , 5-HT 2A) exerts antiseizure effects in a zebrafish scn1Lab −/− mutant model of DS. Using the zebrafish DS model, our aim was to examine the possibility of repurposing efavirenz (EFA), lisuride (LIS), and rizatriptan (RIZA), marketed medicines with a 5-HT on-or off-target profile, as antiepileptic drugs for DS. To examine whether these compounds have a broader antiseizure profile, they were tested in pentylenetetrazol and ethyl ketopentenoate (EKP) zebrafish models. Pharmacological effects were assessed by locomotor behavior, local field potential brain recordings, and bioluminescence. EFA was active in all models, whereas LIS was selectively active in the zebrafish DS model. Mainly, a poor response was observed to RIZA. Taken together, our preclinical results show that LIS could be a potential candidate for DS treatment. EFA was also active in the EKP model, characterized by a high level of treatment resistance, and hence these data are potentially important for future treatment of drug-resistant epilepsy.
Dravet syndrome (DS) is a genetic encephalopathy that is characterized by severe seizures and pro... more Dravet syndrome (DS) is a genetic encephalopathy that is characterized by severe seizures and prominent co-morbidities (e.g., physical, intellectual disabilities). More than 85% of the DS patients carry an SCN1A mutation (sodium channel, voltage gated, type I alpha subunit). Although numerous anti-epileptic drugs have entered the market since 1990, these drugs often fail to adequately control seizures in DS patients. Nonetheless, current clinical data shows significant seizure reduction in DS patients treated with the serotonergic (5-hydroxytryptamine, 5-HT) drug fenfluramine (FA). Recent preclinical research confirmed the anti-epileptiform activity of FA in homozygous scn1a mutant zebrafish larvae that mimic DS well. Here we explored the anti-epileptiform mechanisms of FA by investigating whether selective agonists/antagonists of specific receptor subtypes were able to counteract the FA-induced inhibition of seizures and abnormal brain discharges observed in the scn1a mutants. We show that antagonists of 5-HT 1D and 5-HT 2C receptor subtypes were able to do so (LY 310762 and SB 242084, respectively), but notably, a 5-HT 2A-antagonist (ketanserin) was not. In addition, exploring further the mechanism of action of FA beyond its serotonergic profile, we found that the anti-epileptiform brain activity of FA was significantly abolished when it was administered in combination with a σ 1-agonist (PRE 084). Our study therefore provides the first evidence of an involvement of the σ 1 receptor in the mechanism of FA. We further show that the level of some neurotransmitters [i.e., dopamine and noradrenaline (NAD)] in head homogenates was altered after FA treatment, whereas γ-aminobutyric acid (GABA) and glutamate levels were not. Of interest, NAD-decreasing drugs have been employed successfully in the treatment of neurological diseases; including epilepsy and this effect could contribute to the therapeutic effect of the compound. In summary, we hypothesize that the anti-epileptiform activity of FA not only originates from its 5-HT 1Dand 5-HT 2C-agonism, but likely also from its ability to block σ 1 receptors. These findings will help in better understanding the pharmacological profile of compounds that is critical for their applicability in the treatment of DS and possibly also other drug-resistant epilepsies.
Epilepsy is a prevalent neurological disease, affecting up to 70 million people worldwide. The ul... more Epilepsy is a prevalent neurological disease, affecting up to 70 million people worldwide. The ultimate goal for patients with epilepsy (PWE) is to achieve complete seizure control without drug-induced adverse events and preserve the quality of life. The mainstay of epilepsy treatment is controlling seizures by antiseizure medications (ASMs; previously referred to as anti-epileptic drugs, AEDs) that can act through different pathways, that is, an increase of neuronal inhibition and/or a decrease of neuronal excitation. 1 The first-generation ASMs mainly act by blocking sodium channels or stimulating the neurotransmission by γ-aminobutyric acid (GABA), 2 while second-and third-generation ASMs have distinct molecular targets. 3 Moreover, the pharmacokinetic profile of the newer ASMs has improved, which led to more predictable doseresponse effects, fewer side effects, and fewer/no drugdrug interactions. 4 Nonetheless, more than 30% of the
Background. Epilepsy is a chronic neurological condition, with over 30% of cases unresponsive to ... more Background. Epilepsy is a chronic neurological condition, with over 30% of cases unresponsive to treatment. Zebrafish larvae show great potential to serve as an animal model of epilepsy in drug discovery. Thanks to their high fecundity and relatively low cost, they are amenable to high-throughput screening. However, the assessment of seizure occurrences in zebrafish larvae remains a bottleneck, as visual analysis is subjective and time-consuming. New method. For the first time, we present an automated algorithm to detect epileptic discharges in single-channel local field potential (LFP) recordings in zebrafish. First, candidate seizure segments are selected based on their energy and length. Afterwards, discriminative features are extracted from each segment. Using a labeled dataset, a support vector machine (SVM) classifier is trained to learn an optimal feature mapping. Finally, this SVM classifier is used to detect seizure segments in new signals. Results. We tested the proposed algorithm both in a chemically-induced seizure model and a genetic epilepsy model. In both cases, the algorithm delivered similar results to visual analysis and found a significant difference in number of seizures between the epileptic and control group. Comparison with Existing Methods. Direct comparison with multichannel techniques or methods developed for different animal models is not feasible. Nevertheless, a literature review shows that our algorithm outperforms state-ofthe-art techniques in terms of accuracy, precision and specificity, while maintaining a reasonable sensitivity. Conclusion. Our seizure detection system is a generic, time-saving and objective method to analyze zebrafish LPF, which can replace visual analysis and facilitate true high-throughput studies.
Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high s... more Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high seizure burden and non-seizure comorbidities. The antiseizure medication (ASM) fenfluramine is an effective treatment for reducing seizure frequency, ameliorating comorbidities, and potentially reducing risk of sudden unexpected death in epilepsy (SUDEP) in patients with Dravet syndrome and Lennox-Gastaut syndrome, among other rare epilepsies. Fenfluramine has a unique mechanism of action (MOA) among ASMs. Its primary MOA is currently described as dual-action sigma-1 receptor and serotonergic activity; however, other mechanisms may be involved. Here, we conduct an extensive review of the literature to identify all previously described mechanisms for fenfluramine. We also consider how these mechanisms may play a role in the reports of clinical benefit in non-seizure outcomes, including SUDEP and everyday executive function. Our review highlights the importance of serotonin and sigma-1 receptor mechanisms in maintaining a balance between excitatory (glutamatergic) and inhibitory (γ-aminobutyric acid [GABA]-ergic) neural networks, and suggests that these mechanisms may represent primary pharmacological MOAs in seizures, non-seizure comorbidities, and SUDEP. We also describe ancillary roles for GABA neurotransmission, noradrenergic neurotransmission, and the endocrine system (especially such progesterone derivatives as neuroactive steroids). Dopaminergic activity underlies appetite reduction, a common side effect with fenfluramine treatment, but any involvement in seizure reduction remains speculative. Further research is underway to evaluate promising new biological pathways for fenfluramine. A better understanding of the pharmacological mechanisms for fenfluramine in reducing seizure burden and non-seizure comorbidities may allow for rational drug design and/or improved clinical decision-making when prescribing multi-ASM regimens.
ObjectiveAntiseizure medications (ASMs) remain the mainstay of epilepsy treatment. These ASMs hav... more ObjectiveAntiseizure medications (ASMs) remain the mainstay of epilepsy treatment. These ASMs have mainly been tested in trials in adults with epilepsy, which subsequently led to market authorization (MA). For treatment of – especially young – children with epilepsy, several ASMs do not have a MA and guidelines are lacking, subsequently leading to “off‐label” use of ASMs. Even though “off‐label” ASM prescriptions for children could lead to more adverse events, it can be clinically appropriate and rational if the benefits outweigh the risks. This could be the case if “on‐label” ASM, in mono‐ or polytherapy, fails to achieve adequate seizure control.MethodsThe Medical Therapies Task Force of the International League Against Epilepsy (ILAE) Commission for Pediatrics performed a survey to study the current treatment practices in six classic, early life epilepsy scenarios. Our aim was not only to study first‐ and second‐line treatment preferences but also to illustrate the use of “off‐label” drugs in childhood epilepsies.ResultsOur results reveal that several ASMs (e.g. topiramate, oxcarbazepine, benzodiazepines) are prescribed “off‐label” in distinct scenarios of young children with epilepsy. In addition, recent scientific guidelines were not always adopted by several survey respondents, suggesting a potential knowledge gap.SignificanceWe report the relatively common use of “off‐label” prescriptions that underlines the need for targeted and appropriately designed clinical trials, including younger patients, which will also result in the ability to generate evidence‐based guidelines.
Dravet syndrome (DS) is a rare genetic encephalopathy that is characterized by severe seizures an... more Dravet syndrome (DS) is a rare genetic encephalopathy that is characterized by severe seizures and highly resistant to commonly used antiepileptic drugs (AEDs). In 2020, FDA has approved fenfluramine (FFA) for treatment of seizures associated with DS. However, the clinically used FFA is a racemic mixture (i.e. (±)-FFA), that is substantially metabolized to norfenfluramine (norFFA), and it is presently not known whether the efficacy of FFA is due to a single enantiomer of FFA, or to both, and whether the norFFA enantiomers also contribute significantly. In this study, the antiepileptic activity of enantiomers of FFA (i.e. (+)-FFA and (−)-FFA) and norFFA (i.e. (+)-norFFA and (−)-norFFA) was explored using the zebrafish scn1Lab −/− mutant model of DS. To validate the experimental conditions used, we assessed the activity of various AEDs typically used in the fight against DS, including combination therapy. Overall, our results are highly consistent with the treatment algorithm proposed by the updated current practice in the clinical management of DS. Our results show that (+)-FFA, (−)-FFA and (+)-norFFA displayed significant antiepileptic effects in the preclinical model, and thus can be considered as compounds actively contributing to the clinical efficacy of FFA. In case of (−)-norFFA, the results were less conclusive. We also investigated the uptake kinetics of the enantiomers of FFA and norFFA in larval zebrafish heads. The data show that the total uptake of each compound increased in a time-dependent fashion. A somewhat similar uptake was observed for the (+)-norFFA and (−)-norFFA, implying that the levo/dextrotation of the structure did not dramatically affect the uptake. Significantly, when comparing (+)-FFA with the less lipophilic (+)-norFFA, the data clearly show that the normetabolite of FFA is taken up less than the parent compound.
Epilepsy in POLG related disease usually involves biallelic recessive mutations causing chronic n... more Epilepsy in POLG related disease usually involves biallelic recessive mutations causing chronic neuronal loss and neuronal death. However, monoallelic POLG mutations have been reported in patients with neurological features such as seizures [1]. In these patients a second allele/gene was anticipated but not identified. The genetic etiology in epilepsy can contribute to better treatment strategies. For example, valproic acid (VPA) should be avoided in patients with POLG related epilepsy due to possible hepatotoxicity. We report a 12-year old boy with initially drug-resistant focal onset epilepsy, a mild developmental delay and behavioral issues. He carries potential pathogenic variants in the DNA polymerase gamma (POLG) gene (from asymptomatic mother) and in the liprin-alpha-4 (PPFIA4) gene (from asymptomatic father). This latter gene has never been related to (neurological) disorders, although its gene product interacts with several genes that play a role in excitatory neurotransmission and epileptogenesis. Hence, we hypothesize that the phenotype of our patient could be due to combination of detrimental effects to the neurons by the two aforementioned pathogenic variants. Nonetheless, we cannot exclude another undetected POLG mutation. In essence, genetic research should be aware that unexplained neurological disease can be caused by an oligogenic, rather than a monogenic, etiology.
Sunflower syndrome (SS) is a rare, photosensitive epilepsy characterized by an attraction to ligh... more Sunflower syndrome (SS) is a rare, photosensitive epilepsy characterized by an attraction to light and highly stereotyped seizures with associated hand-waving (HW). It is controversial whether HW is part of the seizure or a provoking factor; therefore, we aimed to characterize the ictal electroencephalogram (EEG) in patients with SS. Video-EEG (vEEG) and charts of five patients with SS with HW during vEEG from Massachusetts General Hospital's Pediatric Epilepsy Program were reviewed and analyzed. In four out of five patients, the ictal EEG showed high amplitude (500-700 μV) 3-4 Hz generalized spike/ polyspike-and-slow wave discharges, lasting 1.63-24.41 s. One hundred and twelve of 126 HW episodes, correlating to epileptiform activity (vEEG), had a lag time of less than 1.00 s (88.89%) between onset of HW and appearance of epileptiform activity. This suggests that HW does not induce seizure activity. Awareness of the ictal EEG features of this syndrome is important, as patients are frequently described as "selfinducing" their seizures.
Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high s... more Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high seizure burden and non-seizure comorbidities. The antiseizure medication (ASM) fenfluramine is an effective treatment for reducing seizure frequency, ameliorating comorbidities, and potentially reducing risk of sudden unexpected death in epilepsy (SUDEP) in patients with Dravet syndrome and Lennox-Gastaut syndrome, among other rare epilepsies. Fenfluramine has a unique mechanism of action (MOA) among ASMs. Its primary MOA is currently described as dual-action sigma-1 receptor and serotonergic activity; however, other mechanisms may be involved. Here, we conduct an extensive review of the literature to identify all previously described mechanisms for fenfluramine. We also consider how these mechanisms may play a role in the reports of clinical benefit in non-seizure outcomes, including SUDEP and everyday executive function. Our review highlights the importance of serotonin and sigma-1 rece...
Journal of the International Child Neurology Association, 2021
Background: Optimal care of Convulsive status epilepticus (CSE) can be related to multiple barrie... more Background: Optimal care of Convulsive status epilepticus (CSE) can be related to multiple barriers in resource-limited countries. Objectives and methods: Since limited data of CSE management are available from South-East Africa, we performed a retrospective analysis of the electronic records of pediatric patients with CSE admitted to the Maputo Central hospital from January 2016 until April 2019. Results: Our database consisted out of 39 patients. The average age was 5.15 (range 0.3-13.8) years and demographic characteristics did not show a relation to CSE characteristics or outcomes. However, the total stay in the hospital was negatively correlated with age (p=0.0314). Moreover, 14 patients needed to be admitted to the IC, which was correlated to having generalized motor seizures (p=0.0253), and a relatively higher need for a second AED to control their CSE (p=0.0131). Regarding AED use, the first AED was a IV benzodiazepine (BZD: midazolam (MIDA) or diazepam (DIAZ)) or IV phenyto...
Rare genetic diseases are a group of pathologies with often unmet clinical needs. Even if rare by... more Rare genetic diseases are a group of pathologies with often unmet clinical needs. Even if rare by a single genetic disease (from 1/2000 to 1/more than 1,000,000), the total number of patients concerned account for approximatively 400 million peoples worldwide. Finding treatments remains challenging due to the complexity of these diseases, the small number of patients and the challenge in conducting clinical trials. Therefore, innovative preclinical research strategies are required. The zebrafish has emerged as a powerful animal model for investigating rare diseases. Zebrafish combines conserved vertebrate characteristics with high rate of breeding, limited housing requirements and low costs. More than 84% of human genes responsible for diseases present an orthologue, suggesting that the majority of genetic diseases could be modelized in zebrafish. In this review, we emphasize the unique advantages of zebrafish models over other in vivo models, particularly underlining the high throu...
Dravet syndrome (DS) is a severe epilepsy syndrome that starts within the first year of life. In ... more Dravet syndrome (DS) is a severe epilepsy syndrome that starts within the first year of life. In a clinical study, add-on treatment with fenfluramine, a potent 5hydroxytryptamine (5-HT) releaser activating multiple 5-HT receptor subtypes, made 70% of DS children seizure free. Others and we recently confirmed the efficacy of fenfluramine as an antiepileptiform compound in zebrafish models of DS. By using a large set of subtype selective agonists, in this study we examined which 5-HT receptor subtypes can be targeted to trigger antiseizure effects in homozygous scn1Lab −/− mutant zebrafish larvae that recapitulate DS well. We also provide evidence that zebrafish larvae express the orthologues of all human 5-HT receptor subtypes. Using an automated larval locomotor behavior assay, we were able to show that selective 5-HT 1D-, 5-HT 1E-, 5-HT 2A-, 5-HT 2C-, and 5-HT 7-agonists significantly decreased epileptiform activity in the mutant zebrafish at 7 days post fertilization (dpf). By measuring local field potentials in the zebrafish larval forebrain, we confirmed the antiepileptiform activity of the 5-HT 1D-, 5-HT 2C-, and especially the 5-HT 2A-agonist. Interestingly, we also found a significant decrease of serotonin in the heads of homozygous scn1Lab −/− mutants as compared to the wild type zebrafish, which suggest that neurochemical defects might play a crucial role in the pathophysiology of DS. Taken together, our results emphasize the high conservation of the serotonergic receptors in zebrafish larvae. Modulating certain serotonergic receptors was shown to effectively reduce seizures. Our findings therefore open new avenues for the development of future novel DS therapeutics.
Dravet syndrome (DS) is a severe genetic epileptic encephalopathy with onset during the first yea... more Dravet syndrome (DS) is a severe genetic epileptic encephalopathy with onset during the first year of life. Zebrafish models recapitulating human diseases are often used as drug discovery platforms, but also for drug repurposing testing. It was recently shown that pharmacological modulation of three serotonergic (5-HT) receptors (5-HT 1D , 5-HT 2C , 5-HT 2A) exerts antiseizure effects in a zebrafish scn1Lab −/− mutant model of DS. Using the zebrafish DS model, our aim was to examine the possibility of repurposing efavirenz (EFA), lisuride (LIS), and rizatriptan (RIZA), marketed medicines with a 5-HT on-or off-target profile, as antiepileptic drugs for DS. To examine whether these compounds have a broader antiseizure profile, they were tested in pentylenetetrazol and ethyl ketopentenoate (EKP) zebrafish models. Pharmacological effects were assessed by locomotor behavior, local field potential brain recordings, and bioluminescence. EFA was active in all models, whereas LIS was selectively active in the zebrafish DS model. Mainly, a poor response was observed to RIZA. Taken together, our preclinical results show that LIS could be a potential candidate for DS treatment. EFA was also active in the EKP model, characterized by a high level of treatment resistance, and hence these data are potentially important for future treatment of drug-resistant epilepsy.
Dravet syndrome (DS) is a genetic encephalopathy that is characterized by severe seizures and pro... more Dravet syndrome (DS) is a genetic encephalopathy that is characterized by severe seizures and prominent co-morbidities (e.g., physical, intellectual disabilities). More than 85% of the DS patients carry an SCN1A mutation (sodium channel, voltage gated, type I alpha subunit). Although numerous anti-epileptic drugs have entered the market since 1990, these drugs often fail to adequately control seizures in DS patients. Nonetheless, current clinical data shows significant seizure reduction in DS patients treated with the serotonergic (5-hydroxytryptamine, 5-HT) drug fenfluramine (FA). Recent preclinical research confirmed the anti-epileptiform activity of FA in homozygous scn1a mutant zebrafish larvae that mimic DS well. Here we explored the anti-epileptiform mechanisms of FA by investigating whether selective agonists/antagonists of specific receptor subtypes were able to counteract the FA-induced inhibition of seizures and abnormal brain discharges observed in the scn1a mutants. We show that antagonists of 5-HT 1D and 5-HT 2C receptor subtypes were able to do so (LY 310762 and SB 242084, respectively), but notably, a 5-HT 2A-antagonist (ketanserin) was not. In addition, exploring further the mechanism of action of FA beyond its serotonergic profile, we found that the anti-epileptiform brain activity of FA was significantly abolished when it was administered in combination with a σ 1-agonist (PRE 084). Our study therefore provides the first evidence of an involvement of the σ 1 receptor in the mechanism of FA. We further show that the level of some neurotransmitters [i.e., dopamine and noradrenaline (NAD)] in head homogenates was altered after FA treatment, whereas γ-aminobutyric acid (GABA) and glutamate levels were not. Of interest, NAD-decreasing drugs have been employed successfully in the treatment of neurological diseases; including epilepsy and this effect could contribute to the therapeutic effect of the compound. In summary, we hypothesize that the anti-epileptiform activity of FA not only originates from its 5-HT 1Dand 5-HT 2C-agonism, but likely also from its ability to block σ 1 receptors. These findings will help in better understanding the pharmacological profile of compounds that is critical for their applicability in the treatment of DS and possibly also other drug-resistant epilepsies.
Epilepsy is a prevalent neurological disease, affecting up to 70 million people worldwide. The ul... more Epilepsy is a prevalent neurological disease, affecting up to 70 million people worldwide. The ultimate goal for patients with epilepsy (PWE) is to achieve complete seizure control without drug-induced adverse events and preserve the quality of life. The mainstay of epilepsy treatment is controlling seizures by antiseizure medications (ASMs; previously referred to as anti-epileptic drugs, AEDs) that can act through different pathways, that is, an increase of neuronal inhibition and/or a decrease of neuronal excitation. 1 The first-generation ASMs mainly act by blocking sodium channels or stimulating the neurotransmission by γ-aminobutyric acid (GABA), 2 while second-and third-generation ASMs have distinct molecular targets. 3 Moreover, the pharmacokinetic profile of the newer ASMs has improved, which led to more predictable doseresponse effects, fewer side effects, and fewer/no drugdrug interactions. 4 Nonetheless, more than 30% of the
Background. Epilepsy is a chronic neurological condition, with over 30% of cases unresponsive to ... more Background. Epilepsy is a chronic neurological condition, with over 30% of cases unresponsive to treatment. Zebrafish larvae show great potential to serve as an animal model of epilepsy in drug discovery. Thanks to their high fecundity and relatively low cost, they are amenable to high-throughput screening. However, the assessment of seizure occurrences in zebrafish larvae remains a bottleneck, as visual analysis is subjective and time-consuming. New method. For the first time, we present an automated algorithm to detect epileptic discharges in single-channel local field potential (LFP) recordings in zebrafish. First, candidate seizure segments are selected based on their energy and length. Afterwards, discriminative features are extracted from each segment. Using a labeled dataset, a support vector machine (SVM) classifier is trained to learn an optimal feature mapping. Finally, this SVM classifier is used to detect seizure segments in new signals. Results. We tested the proposed algorithm both in a chemically-induced seizure model and a genetic epilepsy model. In both cases, the algorithm delivered similar results to visual analysis and found a significant difference in number of seizures between the epileptic and control group. Comparison with Existing Methods. Direct comparison with multichannel techniques or methods developed for different animal models is not feasible. Nevertheless, a literature review shows that our algorithm outperforms state-ofthe-art techniques in terms of accuracy, precision and specificity, while maintaining a reasonable sensitivity. Conclusion. Our seizure detection system is a generic, time-saving and objective method to analyze zebrafish LPF, which can replace visual analysis and facilitate true high-throughput studies.
Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high s... more Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high seizure burden and non-seizure comorbidities. The antiseizure medication (ASM) fenfluramine is an effective treatment for reducing seizure frequency, ameliorating comorbidities, and potentially reducing risk of sudden unexpected death in epilepsy (SUDEP) in patients with Dravet syndrome and Lennox-Gastaut syndrome, among other rare epilepsies. Fenfluramine has a unique mechanism of action (MOA) among ASMs. Its primary MOA is currently described as dual-action sigma-1 receptor and serotonergic activity; however, other mechanisms may be involved. Here, we conduct an extensive review of the literature to identify all previously described mechanisms for fenfluramine. We also consider how these mechanisms may play a role in the reports of clinical benefit in non-seizure outcomes, including SUDEP and everyday executive function. Our review highlights the importance of serotonin and sigma-1 receptor mechanisms in maintaining a balance between excitatory (glutamatergic) and inhibitory (γ-aminobutyric acid [GABA]-ergic) neural networks, and suggests that these mechanisms may represent primary pharmacological MOAs in seizures, non-seizure comorbidities, and SUDEP. We also describe ancillary roles for GABA neurotransmission, noradrenergic neurotransmission, and the endocrine system (especially such progesterone derivatives as neuroactive steroids). Dopaminergic activity underlies appetite reduction, a common side effect with fenfluramine treatment, but any involvement in seizure reduction remains speculative. Further research is underway to evaluate promising new biological pathways for fenfluramine. A better understanding of the pharmacological mechanisms for fenfluramine in reducing seizure burden and non-seizure comorbidities may allow for rational drug design and/or improved clinical decision-making when prescribing multi-ASM regimens.
ObjectiveAntiseizure medications (ASMs) remain the mainstay of epilepsy treatment. These ASMs hav... more ObjectiveAntiseizure medications (ASMs) remain the mainstay of epilepsy treatment. These ASMs have mainly been tested in trials in adults with epilepsy, which subsequently led to market authorization (MA). For treatment of – especially young – children with epilepsy, several ASMs do not have a MA and guidelines are lacking, subsequently leading to “off‐label” use of ASMs. Even though “off‐label” ASM prescriptions for children could lead to more adverse events, it can be clinically appropriate and rational if the benefits outweigh the risks. This could be the case if “on‐label” ASM, in mono‐ or polytherapy, fails to achieve adequate seizure control.MethodsThe Medical Therapies Task Force of the International League Against Epilepsy (ILAE) Commission for Pediatrics performed a survey to study the current treatment practices in six classic, early life epilepsy scenarios. Our aim was not only to study first‐ and second‐line treatment preferences but also to illustrate the use of “off‐label” drugs in childhood epilepsies.ResultsOur results reveal that several ASMs (e.g. topiramate, oxcarbazepine, benzodiazepines) are prescribed “off‐label” in distinct scenarios of young children with epilepsy. In addition, recent scientific guidelines were not always adopted by several survey respondents, suggesting a potential knowledge gap.SignificanceWe report the relatively common use of “off‐label” prescriptions that underlines the need for targeted and appropriately designed clinical trials, including younger patients, which will also result in the ability to generate evidence‐based guidelines.
Dravet syndrome (DS) is a rare genetic encephalopathy that is characterized by severe seizures an... more Dravet syndrome (DS) is a rare genetic encephalopathy that is characterized by severe seizures and highly resistant to commonly used antiepileptic drugs (AEDs). In 2020, FDA has approved fenfluramine (FFA) for treatment of seizures associated with DS. However, the clinically used FFA is a racemic mixture (i.e. (±)-FFA), that is substantially metabolized to norfenfluramine (norFFA), and it is presently not known whether the efficacy of FFA is due to a single enantiomer of FFA, or to both, and whether the norFFA enantiomers also contribute significantly. In this study, the antiepileptic activity of enantiomers of FFA (i.e. (+)-FFA and (−)-FFA) and norFFA (i.e. (+)-norFFA and (−)-norFFA) was explored using the zebrafish scn1Lab −/− mutant model of DS. To validate the experimental conditions used, we assessed the activity of various AEDs typically used in the fight against DS, including combination therapy. Overall, our results are highly consistent with the treatment algorithm proposed by the updated current practice in the clinical management of DS. Our results show that (+)-FFA, (−)-FFA and (+)-norFFA displayed significant antiepileptic effects in the preclinical model, and thus can be considered as compounds actively contributing to the clinical efficacy of FFA. In case of (−)-norFFA, the results were less conclusive. We also investigated the uptake kinetics of the enantiomers of FFA and norFFA in larval zebrafish heads. The data show that the total uptake of each compound increased in a time-dependent fashion. A somewhat similar uptake was observed for the (+)-norFFA and (−)-norFFA, implying that the levo/dextrotation of the structure did not dramatically affect the uptake. Significantly, when comparing (+)-FFA with the less lipophilic (+)-norFFA, the data clearly show that the normetabolite of FFA is taken up less than the parent compound.
Epilepsy in POLG related disease usually involves biallelic recessive mutations causing chronic n... more Epilepsy in POLG related disease usually involves biallelic recessive mutations causing chronic neuronal loss and neuronal death. However, monoallelic POLG mutations have been reported in patients with neurological features such as seizures [1]. In these patients a second allele/gene was anticipated but not identified. The genetic etiology in epilepsy can contribute to better treatment strategies. For example, valproic acid (VPA) should be avoided in patients with POLG related epilepsy due to possible hepatotoxicity. We report a 12-year old boy with initially drug-resistant focal onset epilepsy, a mild developmental delay and behavioral issues. He carries potential pathogenic variants in the DNA polymerase gamma (POLG) gene (from asymptomatic mother) and in the liprin-alpha-4 (PPFIA4) gene (from asymptomatic father). This latter gene has never been related to (neurological) disorders, although its gene product interacts with several genes that play a role in excitatory neurotransmission and epileptogenesis. Hence, we hypothesize that the phenotype of our patient could be due to combination of detrimental effects to the neurons by the two aforementioned pathogenic variants. Nonetheless, we cannot exclude another undetected POLG mutation. In essence, genetic research should be aware that unexplained neurological disease can be caused by an oligogenic, rather than a monogenic, etiology.
Sunflower syndrome (SS) is a rare, photosensitive epilepsy characterized by an attraction to ligh... more Sunflower syndrome (SS) is a rare, photosensitive epilepsy characterized by an attraction to light and highly stereotyped seizures with associated hand-waving (HW). It is controversial whether HW is part of the seizure or a provoking factor; therefore, we aimed to characterize the ictal electroencephalogram (EEG) in patients with SS. Video-EEG (vEEG) and charts of five patients with SS with HW during vEEG from Massachusetts General Hospital's Pediatric Epilepsy Program were reviewed and analyzed. In four out of five patients, the ictal EEG showed high amplitude (500-700 μV) 3-4 Hz generalized spike/ polyspike-and-slow wave discharges, lasting 1.63-24.41 s. One hundred and twelve of 126 HW episodes, correlating to epileptiform activity (vEEG), had a lag time of less than 1.00 s (88.89%) between onset of HW and appearance of epileptiform activity. This suggests that HW does not induce seizure activity. Awareness of the ictal EEG features of this syndrome is important, as patients are frequently described as "selfinducing" their seizures.
Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high s... more Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high seizure burden and non-seizure comorbidities. The antiseizure medication (ASM) fenfluramine is an effective treatment for reducing seizure frequency, ameliorating comorbidities, and potentially reducing risk of sudden unexpected death in epilepsy (SUDEP) in patients with Dravet syndrome and Lennox-Gastaut syndrome, among other rare epilepsies. Fenfluramine has a unique mechanism of action (MOA) among ASMs. Its primary MOA is currently described as dual-action sigma-1 receptor and serotonergic activity; however, other mechanisms may be involved. Here, we conduct an extensive review of the literature to identify all previously described mechanisms for fenfluramine. We also consider how these mechanisms may play a role in the reports of clinical benefit in non-seizure outcomes, including SUDEP and everyday executive function. Our review highlights the importance of serotonin and sigma-1 rece...
Journal of the International Child Neurology Association, 2021
Background: Optimal care of Convulsive status epilepticus (CSE) can be related to multiple barrie... more Background: Optimal care of Convulsive status epilepticus (CSE) can be related to multiple barriers in resource-limited countries. Objectives and methods: Since limited data of CSE management are available from South-East Africa, we performed a retrospective analysis of the electronic records of pediatric patients with CSE admitted to the Maputo Central hospital from January 2016 until April 2019. Results: Our database consisted out of 39 patients. The average age was 5.15 (range 0.3-13.8) years and demographic characteristics did not show a relation to CSE characteristics or outcomes. However, the total stay in the hospital was negatively correlated with age (p=0.0314). Moreover, 14 patients needed to be admitted to the IC, which was correlated to having generalized motor seizures (p=0.0253), and a relatively higher need for a second AED to control their CSE (p=0.0131). Regarding AED use, the first AED was a IV benzodiazepine (BZD: midazolam (MIDA) or diazepam (DIAZ)) or IV phenyto...
Rare genetic diseases are a group of pathologies with often unmet clinical needs. Even if rare by... more Rare genetic diseases are a group of pathologies with often unmet clinical needs. Even if rare by a single genetic disease (from 1/2000 to 1/more than 1,000,000), the total number of patients concerned account for approximatively 400 million peoples worldwide. Finding treatments remains challenging due to the complexity of these diseases, the small number of patients and the challenge in conducting clinical trials. Therefore, innovative preclinical research strategies are required. The zebrafish has emerged as a powerful animal model for investigating rare diseases. Zebrafish combines conserved vertebrate characteristics with high rate of breeding, limited housing requirements and low costs. More than 84% of human genes responsible for diseases present an orthologue, suggesting that the majority of genetic diseases could be modelized in zebrafish. In this review, we emphasize the unique advantages of zebrafish models over other in vivo models, particularly underlining the high throu...
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Papers by Jo Sourbron