Thermosensitive hydrogel containing ethosuximide-loaded multivesicular liposomes attenuates age-related hearing loss in C57BL/6J mice

Ethosuximide is the first drug reported to protect against age-related hearing loss, but its benefits are hampered by the pronounced side effects generated through systemic administration. We prepared a thermosensitive hydrogel containing ethosuximide-encapsulated multivesicular liposomes (ethosuximide-loaded MVLs-Gel) and evaluated its functional and histological effects on age-related hearing loss in C57BL/6J mice. The MVLs-Gel showed slow sustained-release characteristics up to over 120 h. After 8 weeks of treatment, compared to the oral systemic administration of ethosuximide, intratympanic ethosuximide-loaded MVLs-Gel injection dramatically reduced the loss of age-related spiral ganglion neurons in the apical turns of the mice (low-frequency regions, p < 0.05). Correspondingly, compared to the oral systemic administration group, the intratympanic ethosuximide-loaded MVLs-Gel injection group showed significantly lower auditory brainstem response threshold shifts at stimulus frequencies of 4, 8, and 16 kHz (low-and middle-frequency regions, p < 0.05). In conclusion, intratympanic ethosuximide-loaded MVLs-Gel injection can reach the apical turn of the cochlea, which is extremely difficult with oral systemic administration of the drug. The ethosuximide-loaded MVLs-Gel, as a novel intratympanic sustained-release drug delivery system, attenuated age-related hearing loss in C57BL/6J mice.

Severe Raynaud's phenomenon from ethosuximide raised concern over possible onset of systemic vasculitis: a case report

BACKGROUND

Ethosuximide and other anti-epileptic drugs have been reported to cause idiosyncratic reactions such as lupus-like syndromes, with elevated antinuclear antibody (ANA) levels. Herein, we present a case of a girl who developed a very severe Raynaud's phenomenon reaction and anti-Scl-70 antibodies related to treatment with ethosuximide, due to juvenile absence epilepsy (JAE).

CASE PRESENTATION

A 12-year-old girl was diagnosed with JAE and treatment with ethosuximide was initiated. Two and a half months later her fingers, digits II-V bilaterally, began to ache and were discolored, alternatingly white, blue, or normal-colored. Two weeks later, her fingers were bluish-black, aching severely, almost continuously. The family sought medical advice. Ethosuximide was halted and due to the severe symptoms, treatment with both prednisolone and intravenous iloprost was commenced. Laboratory tests revealed high ANA levels with anti-Scl-70 pattern and confirmed anti-Scl-70 antibodies. After a few weeks, she started to improve and the symptoms slowly decreased over five months. Anti-Scl-70 was still detectable four months after onset of symptoms, though she was much improved. After eleven months, repeated ANA analyses were completely negative.

CONCLUSION

Although extremely rare, it is important to recognize that severe Raynaud's phenomenon, threatening peripheral digital circulation, may occur as an idiosyncratic reaction to ethosuximide, raising concern over possible onset of vasculitis.

Vibrational dynamics of ethosuximide polymorphs. Infrared absorption and inelastic neutron scattering spectroscopy and model calculations

Commercially available and administered to the patients ethosuximide is a racemic mixture of two enantiomers, each of them exist in different conformations. The presence of the species mentioned are proven by the title experimental methods aided by DFT model calculations. Results of the latter are matched against spectroscopic data by the clustering window analysis. One type of hydrogen bonds exist in the solid forms of ethosuximide NH⋯O, leading to the polymorphic variety of the substance studied.

Open-label pilot study of ethosuximide as adjunctive therapy for relieving abdominal pain related to Irritable Bowel Syndrome

WHAT IS KNOWN AND OBJECTIVES

There is clear evidence for an association between irritable bowel syndrome (IBS) and visceral hypersensitivity. This clinical study aimed to assess the adjunct role of ethosuximide, an antiepileptic drug with T-type calcium channel blocking activity, in the relieving of IBS-related abdominal pain.

METHODS

This is a prospective, 3-month, randomized and controlled study of parallel groups. Fifty outpatients who met the inclusion criteria participated in the trial. Patients were allocated randomly: 25 received mebeverine 135 mg three times daily (t.i.d), whereas the other 25 received mebeverine 135 mg t.i.d and ethosuximide 500 mg t.i.d. At baseline and 12 weeks after starting the drug, patients were evaluated by a gastroenterologist. Serum tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-8 (IL-8), faecal myeloperoxidase and faecal neutrophile gelatinase-associated lipocalin (NGAL) levels were tested before and after treatment. The Numeric Pain Rating Scale (NRS) was assessed before and after three months of therapy.

RESULTS AND DISCUSSION

After 12 weeks, the ethosuximide group showed a statistically and significantly greater reduction in the serum levels of TNF-α, IL-6, IL-8, faecal myeloperoxidase and faecal NGAL in comparison with the control group after the treatment. Moreover, the ethosuximide group showed a statistically significant decrease in NRS compared with the mebeverine group.

WHAT IS NEW AND CONCLUSION

Ethosuximide could be a promising adjunct to antispasmodics in the treatment of IBS patients. Trial registration identifier: NCT04217733.

Anticonvulsive profile of two GABAB receptor antagonists on acute seizure mice models

INTRODUCTION

DL-3-hydroxy-3-phenylpentanamide (HEPP) and DL-3-hydroxy-3-(4'chlorophenyl)-pentanamide (Cl-HEPP) are phenyl-alcohol-amides that are metabotropic GABAB receptor (MGBR) antagonists and protective against absence seizures. This study aims to further characterize the anticonvulsant profile of these drugs.

METHODS

HEPP and Cl-HEPP were evaluated in various standardized acute seizure and toxic tests in female Swiss-OF1 mice.

RESULTS

Toxicities of HEPP and Cl-HEPP were limited; doses up to 30 mg/kg did not result in hypothermia, reduced spontaneous locomotor activity, or failure of the rotarod test, with doses >15 mg/kg potentiating pentobarbital-induced sleep. In maximal electroshock-induced seizures, 20 mg/kg Cl-HEPP protected 100 % of mice; lower doses shortened post-ictal recovery. Seizure protection occurred against subcutaneous pentylenetetrazole and picrotoxin, being limited against N-methyl-d-aspartate. In bicuculline test, clonic or fatal tonic seizures were decreased, onset delayed, and recovery improved; ED₅₀ values (dose protecting 50 % of the animals) were 37.5 and 25 mg/kg for HEPP and Cl-HEPP, respectively. In magnesium deficiency-dependent audiogenic seizures (MDDAS), ED₅₀ values were 3 and 8 mg/kg for Cl-HEPP and HEPP, respectively. The components of MDDAS (latency, wild running, seizure, and recovery phases) in unprotected animals were only minimally affected by near ED₅₀ doses of Cl-HEPP and HEPP.

DISCUSSION

HEPP and, to a greater extent, Cl-HEPP provide anti-seizure protections in several acute seizure tests in mice at nontoxic doses. These results are consistent with the action of these drugs on diverse molecular targets directly resulting from their MGBR antagonistic properties. However, other mechanisms might occur possibly for the protection given in the MES test. Finally, a similarity in the modulation of MDDAS components between the two phenyl alcohol amides and ethosuximide could also be based on the MGBR antagonistic properties of the former, given the recently re-evaluated therapeutic relevant targets of the latter.

Efficacy of anticonvulsant ethosuximide for major depressive disorder: a randomized, placebo-control clinical trial

Results of a preclinical study suggested that the anticonvulsant drug ethosuximide may elicit ketamine-like rapid-acting antidepressant actions. We evaluated the antidepressant efficacy of ethosuximide versus placebo in non-medicated adult patients with major depressive disorder (MDD). This randomized, double-blind, placebo-controlled trial included patients at three mental health centers in China. Eighty eligible adults (aged 18-65 years) met the DSM-5 criteria for MDD. Patients in the acute single study received three doses (500, 1000, or 1500 mg) of ethosuximide or placebo. Patients in the repeated study received ethosuximide (1500 mg/day) or placebo for 2 weeks. The Hamilton Depression Rating Scale (HAM-D), the Montgomery-Åsberg Depression Rating Scale (MADRS), and the Hamilton Anxiety Rating Scale were used to assess antidepressant and antianxiety responses to ethosuximide. No significant reductions in depression and anxiety rating scale scores were observed after a single oral administration of ethosuximide, in comparison with placebo. Furthermore, patients receiving ethosuximide for 2 weeks did not show reductions in depression and anxiety rating scale scores. There were no serious adverse events. Responses to the study's primary and secondary outcome measures, the clinician-rated HAM-D and MADRS, showed no change from baseline to the end of treatment, with either ethosuximide or placebo. These results suggest that ethosuximide does not produce ketamine-like robust antidepressant actions in adult patients with MDD.

Ethosuximide inhibits acute histamine- and chloroquine-induced scratching behavior in mice

We have recently reported that the Cav3.2 T-type calcium channel which is well known for its key role in pain signalling, also mediates a critical function in the transmission of itch/pruritus. Here, we evaluated the effect of the clinically used anti-seizure medication ethosuximide, a well known inhibitor of T-type calcium channels, on male and female mice subjected to histaminergic- and non-histaminergic itch. When delivered intraperitoneally ethosuximide significantly reduced scratching behavior of mice of both sexes in response to subcutaneous injection of either histamine or chloroquine. When co-delivered subcutaneously together with either pruritogenic agent ethosuximide was also effective in inhibiting scratching responses in both male and female animals. Overall, our results are consistent with an important role of Cav3.2 T-type calcium channels in modulating histamine-dependent and histamine-independent itch transmission in the primary sensory pathway. Our findings also suggest that ethosuximide could be explored further as a possible therapeutic for the treatment of itch.

Diagnosing and managing childhood absence epilepsy by telemedicine

The diagnosis of childhood absence epilepsy (CAE) is typically based on history and description of spells, supported by an office-based positive hyperventilation test and confirmed by routine electroencephalography (EEG). In the current coronavirus disease 2019 (COVID-19) pandemic, many pediatric neurologists have switched to telemedicine visits for nonemergent outpatient evaluations. We present a series of children diagnosed as having CAE on the basis of a positive hyperventilation test performed during remote televisits. Several of these children were begun on treatment for CAE prior to obtaining an EEG, with significant seizure reduction. Our series documents the feasibility of CAE diagnosis and management by telemedicine.

Contribution of rare genetic variants to drug response in absence epilepsy

OBJECTIVE

We investigated the possible significance of rare genetic variants to response to valproic acid (VPA) and ethosuximide (ETX) in patients with absence epilepsy. Our primary hypothesis was that rare CACNA1H variants are more frequent in ETX-non-responsive patients compared to ETX-responsive. Our secondary hypothesis was that rare variants in GABA-receptor genes are more frequent in VPA-non-responsive patients compared to VPA-responsive.

METHODS

We recruited patients with absence epilepsy treated with both VPA and ETX, and performed whole exome sequencing in order to investigate the potential role of rare variants in CACNA1H, other voltage-gated calcium channel (VGCC) genes, or GABA-receptor genes in predicting response to ETX or VPA.

RESULTS

Sixty-two patients were included; 12 were ETX-responsive, 14 VPA-responsive, and 36 did not have a clear positive response to either medication. We did not find significant enrichment inCACNA1H rare variants in ETX-responsive patients (odds ratio 3.43; 0.43-27.65; p = 0.20), nor was there enrichment for other VGCC genes. No significant enrichment of GABA-receptor gene rare variants was seen for VPA-non-responsive patients versus VPA-responsive. We found enrichment of rare GABA-receptor variants in our absence cohort compared to controls (odds ratio 3.82; 1.68-8.69). There was no difference in frequency of CACNA1H rs61734410 and CACNA1I rs3747178 polymorphisms between ETX-responsive and ETX-non-responsive groups; these polymorphisms have previously been reported to predict lack of response to ETX in absence epilepsy.

SIGNIFICANCE

We conclude that if CACNA1H rare variants predict lack of response to ETX, a larger sample is necessary to test this with sufficient power. Increased GABA-receptor gene rare variant frequency in absence epilepsy patients who fail initial anti-seizure therapy suggests subtle GABA receptor dysfunction may contribute to the underlying pathophysiology.

Ethosuximide induced macroglossia and oropharyngeal edema

Acute macroglossia and laryngeal edema are rare adverse side effects that can cause life-threatening airway obstruction. We report a case of acute macroglossia that began after initiation of ethosuximide in a 15-year-old female with severe medically refractory epilepsy. Macroglossia worsened over the next two weeks of ethosuximide administration, preventing extubation. Macroglossia and laryngeal edema improved upon ethosuximide wean, and completely resolved after discontinuation. The patient was extubated successfully, with precautionary nasal trumpet placement and dexamethasone administration prior to extubation. In medically complex patients on multiple pharmacologic agents, anti-epileptic drugs should be suspected as a possible cause of acute macroglossia.

Ethosuximide improves chronic pain-induced anxiety- and depression-like behaviors

Chronic pain is a heavy burden disease. Current treatments are generally weakly effective or associated with adverse effects. New therapeutic approaches are therefore needed. Recent studies have suggested T-type calcium channels as an attractive target for the treatment of chronic pain. In this perspective, it was decided to perform a preclinical evaluation of the efficacy of ethosuximide, a T-type channel blocker used clinically as an antiepileptic, as a novel pharmacological treatment for chronic pain. Assessment of the effect of ethosuximide was thus made in both nociception and pain-related comorbidities as anxiety and depression are frequently encountered in chronic pain patients. Our results show that such symptoms occurred in three animal models of chronic pain designed to reflect traumatic neuropathic, chemotherapy-induced neuropathic and inflammatory pain conditions. Administration of ethosuximide reduced both chronic pain and comorbidities with a marked intensity ranging from partial reduction to a complete suppression of symptoms. These results make ethosuximide, and more broadly the inhibition of T-type calcium channels, a new strategy for the management of uncontrolled chronic pain, likely to improve not only pain but also the accompanying anxiety and depression.

Antiepileptogenic effects of Ethosuximide and Levetiracetam in WAG/Rij rats are only temporary

BACKGROUND

WAG/Rij rats represent a validated genetic animal model of epileptogenesis, absence epilepsy and depressive-like comorbidity. Some treatments (e.g. ethosuximide), using specific protocols, prevent the development of spontaneous absence seizures. Accordingly, ethosuximide increases remission occurrence in children with childhood absence epilepsy in comparison to valproic acid. Considering that in this animal model, antiepileptogenic effects are, in some cases, not retained over time, we studied whether the antiepileptogenic effects of both ethosuximide and levetiracetam (which also possesses antiepileptogenic effects in this and other animal epilepsy models) would be retained 5 months after drug suspension.

METHODS

WAG/Rij rats of ˜1 month of age were treated long-term with one of the two drugs at a dose of ˜80 mg/kg/day for 17 consecutive weeks; 1 and 5 months after drug suspension, the development of absence seizures as well as depressive-like behaviour were assessed by EEG recordings and the forced swimming test (FST).

RESULTS

In agreement with a previous report, both drugs continued to show antiepileptogenic effects 1 month after their discontinuation. Furthermore, ethosuximide improved depressive-like behaviour, whereas in contrast, levetiracetam worsened this symptom. However, none of the drugs maintained their antiepileptogenic effects 5 months after suspension, and in addition, animal behaviour in the FST returned to control conditions.

CONCLUSION

Overall, these results demonstrate that the antiepileptogenic effects of both ethosuximide and levetiracetam on absence seizure development and associated depressive-like behaviour in this model are only temporary.

Historical trend toward improved long-term outcome in childhood absence epilepsy

We retrospectively analyzed published studies to investigate historical trends in outcome of childhood absence epilepsy (CAE). We included patients based on onset of absence seizures in childhood, 3 Hz bilateral spike-wave discharges on EEG, and availability of seizure-free outcome data. The primary endpoint was seizure-freedom off medications by study publication year. We also analyzed relationships between seizure-freedom and 1. treatment medication, and 2. CAE diagnostic criteria. We included 29 studies published 1945-2013, encompassing 2416 patients. Seizure-freedom off medications was higher for studies after 1985 versus before 1975 (82% versus 35%; p < 0.001). Ethosuximide and valproate were used more commonly after 1985, and patients previously treated with ethosuximide or valproate had higher seizure-freedom off medications than those treated only with other medications (64% versus 32%; χ²>10; p < 0.001). Although differences in diagnostic criteria for early vs. later studies did not reach statistical significance, later studies tended to use normal EEG background (p = 0.09) and absence of comorbid disorders (p = 0.09) as criteria more commonly. These findings demonstrate that seizure-freedom off medications has improved in published CAE studies after 1985. Our results are limited due to retrospective analysis. Further work is needed with prospective, controlled trials to establish factors leading to improved long-term prognosis in CAE.

Microextraction combined with microderivatization for drug monitoring and protein modification analysis from limited blood volume using mass spectrometry

In the clinic, ethosuximide is commonly used to treat generalized absence seizures but has recently been repurposed for other diseases. Because of adverse effects and drug interactions, high-throughput therapeutic drug monitoring of ethosuximide is necessary. Microextraction is a simple, effective, rapid, and low consumption of organic solvents method for sample preparation. In this study, microderivatization-increased detection (MDID)-combined microextraction was used to detect ethosuximide by mass spectrometry. Ethosuximide is a difficult to retain and ionize compound in the C18 nano-flow column and ionization interface, respectively. Hence, we developed a fast method for detecting ethosuximide in human plasma by using the MDID strategy (within 2 min). Chemical microderivatization parameters were studied and optimized to increase the sensitivity of ethosuximide detection at trace levels. The linear range for the analysis of ethosuximide in 10 μL plasma was 5-500 μg/mL with a coefficient of determination (r²) ≥ 0.995. The precision and accuracy of intraday and interday analyses of ethosuximide were below 13.0%. Furthermore, modifications of major proteins in plasma and blood cells, induced by ethosuximide, were identified. The proposed method effectively utilizes microliter samples to detect drug plasma concentrations under suitable microextraction procedures toward the eco-friendly goal of low consumption of organic solvents. Graphical abstract ᅟ.

A Caenorhabditis elegans assay of seizure-like activity optimised for identifying antiepileptic drugs and their mechanisms of action

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Worms with mutant GABA_A receptors exhibit convulsions upon exposure to pentylenetetrazol.

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Convulsions are prevented by the approved anti-epileptic drug, ethosuximide.

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C. elegans model is a higher throughput, ethical alternative to rodent seizure models.

Background

Epilepsy affects around 1% of people, but existing antiepileptic drugs (AEDs) only offer symptomatic relief and are ineffective in approximately 30% of patients. Hence, new AEDs are sorely needed. However, a major bottleneck is the low-throughput nature of early-stage AED screens in conventional rodent models. This process could potentially be expedited by using simpler invertebrate systems, such as the nematode Caenorhabditis elegans.

New method

Head-bobbing convulsions were previously reported to be inducible by pentylenetetrazol (PTZ) in C. elegans with loss-of-function mutations in unc-49, which encodes a GABA_A receptor. Given that epilepsy-linked mutations in human GABA_A receptors are well documented, this could represent a clinically-relevant system for early-stage AED screens. However, the original agar plate-based assay is unsuited to large-scale screening and has not been validated for identifying AEDs. Therefore, we established an alternative streamlined, higher-throughput approach whereby mutants were treated with PTZ and AEDs via liquid-based incubation.

Results

Convulsions induced within minutes of PTZ exposure in unc-49 mutants were strongly inhibited by the established AED ethosuximide. This protective activity was independent of ethosuximide’s suggested target, the T-type calcium channel, as a null mutation in the worm cca-1 ortholog did not affect ethosuximide’s anticonvulsant action.

Comparison with existing method

Our streamlined assay is AED-validated, feasible for higher throughput compound screens, and can facilitate insights into AED mechanisms of action.

Conclusions

Based on an epilepsy-associated genetic background, this C. elegans unc-49 model of seizure-like activity presents an ethical, higher throughput alternative to conventional rodent seizure models for initial AED screens.

The effects of ethosuximide on aversive instrumental learning in adult rats

Antiepileptic medications are the frontline treatment for seizure conditions but are not without cognitive side effects. Previously, our laboratory reported learning deficits in phenytoin-, carbamazepine-, valproic acid-, and felbamate-treated rats. In this experiment, the effects found in ethosuximide (ETH)-treated rats have been compared with those in water-treated controls (controls) using the same instrumental training tasks. Rats treated with ETH did not display any performance deficits in any of the conditions tested relative to controls. These animals showed more rapid acquisition of the avoidance response than the control animals but only when they had prior experience in the appetitive condition. Of the drugs tested to date with these learning paradigms, ETH is the only one that did not impair performance relative to controls in any condition tested. Moreover, in comparison with rats treated with valproic acid, the only other available compound commonly recommended for the treatment of absence seizures, ETH-treated rats show substantially higher performance.

α-Methyl-α-phenylsuccinimide ameliorates neurodegeneration in a C. elegans model of TDP-43 proteinopathy

The antiepileptic drug ethosuximide has recently been shown to be neuroprotective in various Caenorhabditis elegans and rodent neurodegeneration models. It is therefore a promising repurposing candidate for the treatment of multiple neurodegenerative diseases. However, high concentrations of the drug are required for its protective effects in animal models, which may impact on its translational potential and impede the identification of its molecular mechanism of action. Therefore, we set out to develop more potent neuroprotective lead compounds based on ethosuximide as a starting scaffold. Chemoinformatic approaches were used to identify compounds with structural similarity to ethosuximide and to prioritise these based on good predicated blood-brain barrier permeability and C. elegans bioaccumulation properties. Selected compounds were initially screened for anti-convulsant activity in a C. elegans pentylenetetrazol-induced seizure assay, as a rapid primary readout of bioactivity; and then assessed for neuroprotective properties in a C. elegans TDP-43 proteinopathy model based on pan-neuronal expression of human A315T mutant TDP-43. The most potent compound screened, α-methyl-α-phenylsuccinimide (MPS), ameliorated the locomotion defects and extended the shortened lifespan of TDP-43 mutant worms. MPS also directly protected against neurodegeneration by reducing the number of neuronal breaks and cell body losses in GFP-labelled GABAergic motor neurons. Importantly, optimal neuroprotection was exhibited by external application of 50 μM MPS, compared to 8 mM for ethosuximide. This greater potency of MPS was not due to bioaccumulation to higher internal levels within the worm, based on ¹H-nuclear magnetic resonance analysis. Like ethosuximide, the activity of MPS was abolished by mutation of the evolutionarily conserved FOXO transcription factor, daf-16, suggesting that both compounds act via the same neuroprotective pathway(s). In conclusion, we have revealed a novel neuroprotective activity of MPS that is >100-fold more potent than ethosuximide. This increased potency will facilitate future biochemical studies to identify the direct molecular target(s) of both compounds, as we have shown here that they share a common downstream DAF-16-dependent mechanism of action. Furthermore, MPS is the active metabolite of another approved antiepileptic drug, methsuximide. Therefore, methsuximide may have repurposing potential for treatment of TDP-43 proteinopathies and possibly other human neurodegenerative diseases.

Effects of antiepileptic drugs on mitochondrial functions, morphology, kinetics, biogenesis, and survival

OBJECTIVES

Antiepileptic drugs (AEDs) exhibit adverse and beneficial effects on mitochondria, which have a strong impact on the treatment of patients with a mitochondrial disorder (MID) with epilepsy (mitochondrial epilepsy). This review aims at summarizing and discussing recent findings concerning the effect of AEDs on mitochondrial functions and the clinical consequences with regard to therapy of mitochondrial epilepsy and of MIDs in general.

METHODS

Literature review.

RESULTS

AEDs may interfere with the respiratory chain, with non-respiratory chain enzymes, carrier proteins, or mitochondrial biogenesis, with carrier proteins, membrane-bound channels or receptors and the membrane potential, with anti-oxidative defense mechanisms, with morphology, dynamics and survival of mitochondria, and with the mtDNA. There are AEDs of which adverse effects outweigh beneficial effects, such as valproic acid, carbamazepine, phenytoin, or phenobarbital and there are AEDs in which beneficial effects dominate over mitochondrial toxic effects, such as lamotrigine, levetiracetam, gabapentin, or zonisamide. However, from most AEDs only little is known about their interference with mitochondria.

CONCLUSIONS

Mitochondrial epilepsy might be initially treated with AEDs with low mitochondrial toxic potential. Only in case mitochondrial epilepsy is refractory to these AEDs, AEDs with higher mitochondrial toxic potential might be tried. In patients carrying POLG1 mutations AEDs with high mitochondrial toxic potential are contraindicated.

Exploring two novel cases of suspected ictal epileptic headache, a rare form of paediatric epilepsy

AIM

Ictal epileptic headache (IEH) is a rare and underestimated epileptic form, characterised by epileptiform discharges and headache attacks without any other ictal sensory-motor manifestations. IEH is difficult to diagnose, because the epileptiform discharges have to be registered during the headache attack and the headache has to disappear after the intravenous administration of an anti-epileptic drug, according to the last diagnostic criteria. This study explored the clinical, neuro-physiological and therapeutic features of IEH in the paediatric population.

METHODS

We analysed two novel cases of adolescent female patients with chronic headache and a long history of unsuccessful analgesic oral therapy and without any other ictal sensory-motor events. We also reviewed the entire literature on paediatric IEH.

RESULTS

The clinical history and diagnostic process led us to highly suspect IEH in both patients, and the successful therapy with oral anti-epileptic drugs, namely topiramate and ethosuximide, which resolved the chronic headache, enforced our diagnostic hypothesis. Our literature review highlighted the rarity of IEH clinical reports, particularly in the paediatric population, mainly due to the stringent diagnostic criteria.

CONCLUSION

Our study sheds further light on IEH in the paediatric population and on the importance of diagnostic electroencephalograms in the clinical management of paediatric patients suffering from chronic headache.

Comparison of the Effects of Zonisamide, Ethosuximide and Pregabalin in the Chronic Constriction Injury Induced Neuropathic Pain in Rats

Background:

Evidence has been generated that various anticonvulsant agents provide relief of several chronic pain syndromes and therefore as an alternative to opioids, nonsteroidal anti-inflammatory, and tricyclic antidepressant drugs in the treatment of neuropathic pain. The results of these studies thus raise the question of whether all anticonvulsant drugs or particular mechanistic classes may be efficacious in the treatment of neuropathic pain syndromes.

Aim:

The aim was to compare the clinically used anticonvulsant drugs which are differ in their mechanism of action in a chronic pain model, the chronic constriction injury, in order to determine if all anticonvulsants or only particular mechanistic classes of anticonvulsants are analgesic.

Materials and Methods:

The study included zonisamide, ethosuximide and pregabalin. All compounds were anticonvulsant with diverse mechanism of actions. The peripheral neuropathic pain was induced by chronic constriction injury of the sciatic nerve in male Sprague-Dawley rats. Zonisamide (80 and 40 mg/kg), ethosuximide (300 and 100 mg/kg), pregabalin (50 and 20 mg/kg), and saline was administered intraperitoneally in respective groups in a blinded, randomized manner from postoperative day (POD) 7-13. Paw withdrawal duration to spontaneous pain, chemical allodynia and mechanical hyperalgesia and paw withdrawal latency to mechanical allodynia and thermal hyperalgesia were tested before drug administration on POD7 and after administration on POD 7, 9, 11 and 13.

Results:

The present study suggests that these drugs could provide an effective alternative in the treatment of neuropathic pain. However, zonisamide and pregabalin appears to have suitable efficacy to treat a wide spectrum of neuropathic pain condition.

Conclusion:

The present findings suggest that the inhibition of N-type calcium channels or voltage-gated sodium and T-type calcium channels provides better analgesic potential instead of inhibition of T-type calcium channels alone.

Carbamazepine aggravates absence seizures in two dedicated mouse models

BACKGROUND

The aim of this study was to evaluate the effect of carbamazepine (CBZ) upon chemically induced absence seizures and in a genetic absence seizures model in the mouse.

METHODS

The γ-butyrolactone (GBL)-induced acute absence seizures and the stargazer spontaneous absence seizures mice models were used to characterize the aggravation of absence seizures induced by oral CBZ treatment. The effect of CBZ upon GABA inward-currents in Ltk cells expressing human recombinant α1β2γ2, α2β2γ2, α3β2γ2 and α5β2γ2 GABAA receptors was evaluated by means of patch clamp.

RESULTS

GBL administration induced motor impairment in NMRI mice. High dose CBZ (25mg/kg body weight) had no effect on motor performance but exacerbated the behavioral incoordination observed for GBL. Also, coadministration of a high dose CBZ and GBL impaired spontaneous locomotion. Moreover, CBZ was investigated after oral administration to evaluate the potential to aggravate GBL-induced acute spike-and-wave discharges (SWD) in the electroencephalogram. High dose CBZ significantly aggravated SWD induced by GBL. Likewise, in the stargazer mouse model of genetic spontaneous absence seizures, CBZ significantly aggravated SWD frequency and duration. Pre-treatment with the T-type Ca(2+) channel blocker ethosuximide (200mg/kg body weight) prevented the CBZ aggravation of SWD induced by GBL and in the stargazer mouse. CBZ increased in a concentration dependent manner sub-maximal α1β2γ2 and α3β2γ2 GABA currents.

CONCLUSION

CBZ aggravates absence seizures as assessed in two dedicated mouse models of absence seizures. Facilitation of sub-maximal α1β2γ2, and α3β2γ2 GABA currents by CBZ may play a role in CBZ-induced GABA-mediated aggravation of absence seizures.

Epilepsy with myoclonic absences in siblings

BACKGROUND

Epilepsy with myoclonic absences (EMAs) is a distinct form of childhood epilepsy characterized by a peculiar seizure type that identifies this condition.

PURPOSE

To describe the clinical, electroencephalographic features, treatment strategies and outcome in this first case series of two siblings with normal intelligence presenting with EMAs.

MATERIALS AND METHODS

Both siblings underwent video-polygraphic investigations (simultaneous recording of electroencephalogram [EEG] and electromyogram [EMG] from deltoids), high-resolution magnetic resonance imaging (MRI), karyotyping, neuropsychological evaluation and language assessment.

RESULTS

Both the children had a mean age of onset of prototype seizures by 3.5 years. Myoclonic absences (MAs) were characterized by rhythmic, bilateral, synchronous, symmetric 3-Hz spike-wave discharges, associated with EMG myoclonic bursts at 3 Hz, superimposed on a progressively increasing tonic muscle contraction. The interictal EEG showed a normal background activity with bursts of generalized spike and waves (SWs) as well as rare focal SWs independently over bilateral temporal and frontal regions. Increase in the seizure frequency from 5 to 100/day was observed due to use of carbamazepine and phenobarbitone which decreased with its withdrawal and introduction of valproate. Though lamotrigine was given as an add on to valproate, it did not benefit them and was therefore replaced by topiramate at 3.5 mg/kg/day which has maintained them on remission at one year follow up.

CONCLUSIONS

Recognition of this ictal pattern allows identification and differentiation of EMAs from other seizure types. Idiopathic and symptomatic EMAs need to be differentiated from childhood absence epilepsy with myoclonia. MAs are worsened by drugs like carbamazepine while valproate either alone or in combination with topiramate (preferred to lamotrigine) gives excellent outcome.

Ethosuximide reduces electrographical and behavioral correlates of alcohol withdrawal seizure in DBA/2J mice

Chronic alcohol abuse depresses the nervous system and, upon cessation, rebound hyperexcitability can result in withdrawal seizure. Withdrawal symptoms, including seizures, may drive individuals to relapse, thus representing a significant barrier to recovery. Our lab previously identified an upregulation of the thalamic T-type calcium (T channel) isoform CaV3.2 as a potential contributor to the generation and propagation of seizures in a model of withdrawal. In the present study, we examined whether ethosuximide (ETX), a T-channel antagonist, could decrease the severity of ethanol withdrawal seizures by evaluating electrographical and behavioral correlates of seizure activity. DBA/2J mice were exposed to an intermittent ethanol exposure paradigm. Mice were treated with saline or ETX in each withdrawal period, and cortical EEG activity was recorded to determine seizure severity. We observed a progression in seizure activity with each successive withdrawal period. Treatment with ETX reduced ethanol withdrawal-induced spike and wave discharges (SWDs), in terms of absolute number, duration of events, and contribution to EEG power in the 6-10 Hz frequency range. We also evaluated the effects of ETX on handling-induced convulsions. Overall, we observed a decrease in handling-induced convulsion severity in mice treated with ETX. Our findings suggest that ETX may be a useful pharmacological agent for studies of alcohol withdrawal and treatment of resulting seizures.

Analysis of the antiepileptic, ethosuximide impacts on neurogenesis of rat forebrain stem cells

Specific GABAergic interneurons in the hilus are lost in animal models with temporal-lobe epilepsy (TLE). Some preclinical evidence has indicated that GABAergic cells may provide relief from seizures in these models. This study was aimed to examine the ability of ethosuximide, an anticonvulsant drug, to promote neurogenesis in 3-day-old rat forebrain cortex stem cells. Most of the cells were found to be nestin-positive undifferentiated neural stem cells prior to their exposure to ethosuximide. It was noted that the number and percentage of tubulin β-III immunopositive neurons were increased after 6 days treatment with ethosuximide. Upon bFGF withdrawal, exposure to ethosuximide differentiated the stem cells to MAP2 positive neural cells (7.18 ± 0.43, 21.766 ± 0.55 and 41.57 ± 0.5 for control, 0.1 and 1 μM, respectively). GABA immunofluorescence images illustrated that ethosuximide increased GABAergic neurons (7.19 ± 0.32, 23.23 ± 0.55, and 46.30 ± 0.44 for control, 0.1 and 1 μM, respectively). Additionally, BrdU immunofluorescence assay showed that ethosuximide-enhanced nucleus proliferation in the neuronal stem cells. Therefore, the results of this study suggest that ethosuximide may compensate damage caused by seizure attacks and possibly other neuronal loss disorders.

Anti-epileptogenesis: Electrophysiology, diffusion tensor imaging and behavior in a genetic absence model

The beneficial effects of chronic and early pharmacological treatment with ethosuximide on epileptogenesis were studied in a genetic absence epilepsy model comorbid for depression. It was also investigated whether there is a critical treatment period and treatment length. Cortical excitability in the form of electrical evoked potentials, but also to cortico-thalamo-cortical network activity (spike-wave discharges, SWD and afterdischarges), white matter changes representing extra cortico-thalamic functions and depressive-like behavior were investigated. WAG/Rij rats received either ethosuximide for 2 months (post natal months 2-3 or 4-5), or ethosuximide for 4 months (2-5) in their drinking water, while control rats drank plain water. EEG measurements were made during treatment, and 6 days and 2 months post treatment. Behavioral test were also done 6 days post treatment. DTI was performed ex vivo post treatment. SWD were suppressed during treatment, and 6 days and 2 months post treatment in the 4 month treated group, as well as the duration of AD elicited by cortical electrical stimulation 6 days post treatment. Increased fractional anisotropy in corpus callosum and internal capsula on DTI was found, an increased P8 evoked potential amplitude and a decreased immobility in the forced swim test. Shorter treatments with ETX had no large effects on any parameter. Chronic ETX has widespread effects not only within but also outside the circuitry in which SWD are initiated and generated, including preventing epileptogenesis and reducing depressive-like symptoms. The treatment of patients before symptom onset might prevent many of the adverse consequences of chronic epilepsy.