Chronic Epileptic Seizures Research Articles

Protective Activity of Novel Hydrophilic Synthetic Neurosteroids on Organophosphate Status Epilepticus-induced Chronic Epileptic Seizures, Non-Convulsive Discharges, High-Frequency Oscillations, and Electrographic Ictal Biomarkers.

Nerve agents and organophosphates (OP) are neurotoxic chemicals that induce acute seizures, status epilepticus (SE), and mortality. Long-term neurologic and neurodegenerative effects manifest months to years after OP exposure. Current benzodiazepine anticonvulsants are ineffective in preventing such long-term neurobehavioral and neuropathological changes. New and effective anticonvulsants are needed for OP intoxication, especially for mitigating the long-term sequelae after acute exposure. We developed neurosteroids as novel anticonvulsants and neuroprotectants in OP exposure models. In this study, we evaluated the long-term efficacy of novel synthetic neurosteroids in preventing the development of chronic epilepsy and hyperexcitable ictal events in a rat OP model of SE. Rats were exposed to the OP nerve agent surrogate diisopropylfluorophosphate (DFP), and the experimental groups were treated with the synthetic neurosteroid valaxanolone (VX) or lysaxanolone (LX) 40 minutes post-exposure in conjunction with midazolam. Video-electroencephalography was monitored for two months to assess spontaneous recurrent seizures (SRS), epileptiform discharges, interictal spikes, and high-frequency oscillations (HFOs). Within 60 days of DFP exposure, rats developed chronic epilepsy characterized by frequent SRS, epileptiform discharges, and HFOs. LX treatment was associated with a dose-dependent reduction of epilepsy occurrence and overall seizure burden with a significant decrease in SRS and epileptiform discharges. It also significantly reduced the occurrence of epileptic biomarkers of HFOs and interictal spikes, indicating potential disease-modifying activity. Similarly, the neurosteroid analog VX also significantly attenuated SRS, discharges, HFOs, and ictal events. These results demonstrate the long-term protective effects of synthetic neurosteroids in the OP-exposed post-SE model, indicating their disease-modifying potential to prevent epilepsy and ictal abnormalities. SIGNIFICANCE STATEMENT: The effects of nerve agents and organophosphate (OP) exposure are persistent, and survivors suffer from a number of devastating, chronic neurological dysfunctions. Currently, there is no specific therapy for preventing this disastrous impact of OP exposure. We propose synthetic neurosteroids that activate tonic inhibition provide viable options for preventing the long-term neurological effects of OP intoxication. The results from this study reveal the disease-modifying potential of two novel synthetic neurosteroids in preventing epileptogenesis and chronic epileptic seizures after OP-induced SE.

Insights into the development of pentylenetetrazole-induced epileptic seizures from dynamic metabolomic changes.

Epilepsy is often considered to be a progressive neurological disease, and the nature of this progression remains unclear. Understanding the overall and common metabolic changes of epileptic seizures can provide novel clues for their control and prevention. Herein, a chronic kindling animal model was established to obtain generalized tonic-clonic seizures via the repeated injections of pentylenetetrazole (PTZ) at subconvulsive dose. Dynamic metabolomic changes in plasma and urine from PTZ-kindled rats at the different kindling phases were explored using NMR-based metabolomics, in combination with behavioral assessment, brain neurotransmitter measurement, electroencephalography and histopathology. The increased levels of glucose, lactate, glutamate, creatine and creatinine, together with the decreased levels of pyruvate, citrate and succinate, ketone bodies, asparagine, alanine, leucine, valine and isoleucine in plasma and/or urine were involved in the development and progression of seizures. These altered metabolites reflected the pathophysiological processes including the compromised energy metabolism, the disturbed amino acid metabolism, the peripheral inflammation and changes in gut microbiota functions. NMR-based metabolomics could provide brain disease information by the dynamic plasma and urinary metabolic changes during chronic epileptic seizures, yielding classification of seizure stages and profound insights into controlling epilepsy via targeting deficient energy metabolism.

Increased TRPV1 Channels and FosB Protein Expression Are Associated with Chronic Epileptic Seizures and Anxiogenic-like Behaviors in a Preclinical Model of Temporal Lobe Epilepsy.

Epilepsies are neurological disorders characterized by chronic seizures and their related neuropsychiatric comorbidities, such as anxiety. The Transient Receptor Potential Vanilloid type-1 (TRPV1) channel has been implicated in the modulation of seizures and anxiety-like behaviors in preclinical models. Here, we investigated the impact of chronic epileptic seizures in anxiety-like behavior and TRPV1 channels expression in a genetic model of epilepsy, the Wistar Audiogenic Rat (WAR) strain. WARs were submitted to audiogenic kindling (AK), a preclinical model of temporal lobe epilepsy (TLE) and behavioral tests were performed in the open-field (OF), and light-dark box (LDB) tests 24 h after AK. WARs displayed increased anxiety-like behavior and TRPV1R expression in the hippocampal CA1 area and basolateral amygdala nucleus (BLA) when compared to control Wistar rats. Chronic seizures increased anxiety-like behaviors and TRPV1 and FosB expression in limbic and brainstem structures involved with epilepsy and anxiety comorbidity, such as the hippocampus, superior colliculus, and periaqueductal gray matter. Therefore, these results highlight previously unrecognized alterations in TRPV1 expression in brain structures involved with TLE and anxiogenic-like behaviors in a genetic model of epilepsy, the WAR strain, supporting an important role of TRPV1 in the modulation of neurological disorders and associated neuropsychiatric comorbidities.

The role of proinflammatory cytokines on liver damage after pentylenetetrazole-induced acute and chronic epilepsy models in rats

Objectives: The mechanisms of acute liver failure resulting from epilepsy are poorly defined and appear to be multifactorial, including hypoxia and steatosis. The role of inflammation on liver damage after seizures is unclear. This study aimed to investigate the relationship between proinflammatory cytokines and liver damage after pentylenetetrazole-induced acute and chronic epilepsy models in rats. Materials and methods: Male Wistar albino adult rats (n = 18), weighing 220–240 g, were used in the experiment. The animals were divided into three groups: (1) Control Group (Control; n = 6); rats were treated with a single dose of saline intraperitoneally (i.p.), (2) Acute Epileptic Model Group (n = 6); rats were treated with a single dose of i.p. PTZ (45 mg/kg), (3) Chronic Epileptic Model Group (n = 6); rats were treated with repeated doses of i.p. PTZ (35 mg/kg) every other day for 15(fifteen) times. Result: There was a significant difference between the control and acute epileptic model in terms of serum AST, TNF-α, IL-1 β and IL-6 parameters (p<0.05). On the other hand, there was a significant difference between the acute and chronic epileptic models in the serum AST, TNF-α and IL-6 parameters (p<0.05). Conclusions: As a result, while liver damage is secondary to hypoxia during epileptic seizures, multifactorial causes are blamed. Proinflammatory cytokines that increase in the liver after these factors may be responsible for liver damage in acute epileptic seizures. Compensation mechanisms such as antioxidant defence mechanism in chronic epileptic seizures may prevent liver damage.

Glucosamine promotes seizure activity via activation of the PI3K/Akt pathway in epileptic rats

ContextGlucosamine is an amino monosaccharide with a small molecular weight and has a protective effect against various neurological diseases including multiple sclerosis and encephalomyelitis. Interestingly, low-dose glucosamine has exhibited anti-epilepsy activity. Recent studies have shown that the activation of the protein kinase B (Akt) signaling pathway may promote epilepsy. Glucosamine can increase the level of Akt phosphorylation in the brain tissue, which may aggravate epilepsy. Hence, we speculate that a higher dose of glucosamine may aggravate epilepsy via AKT signaling. ObjectiveTo investigate the effect of glucosamine on the behavior and electrophysiology of epileptic rats through PI3K/Akt pathway. MethodsGlucose (2.0 g/kg) and glucosamine (0, 0.5, 1.0, and 2.0 g/kg) were added to 2 mL of drinking water, respectively. An acute seizure rat model of lithium-pilocarpine and PTZ-kindling were constructed to observe the effects of different doses of glucosamine on epileptic behavior and hippocampal electrical activity. Meanwhile, the changes in Akt were detected by western blot. ResultsEpileptic seizures were induced by a single dose of pilocarpine or PTZ and 2.0 g/kg of glucosamine significantly prolonged the duration and severity of epileptic seizures, enhanced hippocampal electrical activity energy density, and increased phosphorylated AKT levels. A glucosamine dose of 2.0 g/kg also significantly increased the total onset energy density. Furthermore, 2.0 g/kg glucosamine facilitated the development of the chronic PTZ-kindling process. ConclusionsGlucosamine may exacerbate acute and chronic epileptic seizures via activation of the PI3K/Akt pathway in rats with experimental epilepsy.

Exclusive Activation of Caspase-3 in Mossy Fibers and Altered Dynamics of Autophagy Markers in the Mice Hippocampus upon Status Epilepticus Induced by Kainic Acid.

Epileptic seizures are generally associated with pathological changes in the hippocampus such as astrogliosis, mossy fiber sprouting, and neuronal damage. However, more than 30% of temporal lobe epilepsy in humans shows neither neuronal damage nor mossy fiber sprouting despite chronic epileptic seizures. A similar situation exists in certain commonly used strains of mice, specifically C57BL/6 and BALB/c, which exhibit epileptic seizures, but no neuronal damage upon kainic acid administration. This suggests that intrinsic factors may influence the pathological manifestations of epilepsy. Mechanisms which are behind the resistance of hippocampal cells to KA-induced neuronal death are unknown. Autophagy seems to be involved in the pathogenesis of many brain insults and to have a dual nature in neuroprotection and cell death. This study addresses the role of autophagy upon status epilepticus (SE) that has been induced by kainic acid (KA) in the C57BL/6 strain which is classified as seizure resistant. We analyzed the dynamics in the expression of autophagic and cell death markers in the hippocampus upon SE. Immunofluorescence data show that KA did not induce neuronal death in the hippocampal CA1-CA3 subfields; however, it leads to an exclusive activation of caspase-3 in the mossy fibers. We also found alterations in the expression of core proteins of the autophagic machinery. Levels of MAP1LC3, phospho-mTOR/mTOR, and Beclin 1 were significantly increased after induction of seizures. However, levels of Atg3, Atg14, Atg5-Atg12, Atg7, BAG3, Hsp70, and LAMP1 showed no significant alterations compared to controls. Although KA did not induce neuronal death, this study provides morphological and biochemical evidence that status epilepticus induced by KA activates caspase-3 in mossy fibers and induces autophagy in the C57BL/6 hippocampus. These data indicate that autophagic factors may modulate the sensitivity of pyramidal cells to KA and that autophagy may constitute a part of an endogenous neuroprotective arsenal which might be behind the resistance of C57BL/6-hippocampal cells to KA-induced neuronal death.

Hippocampal infusion of lipopolysaccharide induces immune responses and results in seizures in rats.

Recent studies suggest that epileptic seizures might be facilitated by immune reactions in the brain. However, it remains unclear whether inflammatory reactions could result in acute and chronic epileptic seizures in vivo. In the present study, we investigated whether a hippocampal infusion of lipopolysaccharide (LPS) can induce epileptic seizures in rats. We also aimed to elucidate the molecular mechanisms that underpin this phenomenon. Male Wistar rats received a 1.5 μl infusion of either LPS (5 µg/μl), normal saline, or kainate (KA) (0.4 µg/μl) into the right dorsal hippocampus. No seizures were observed in the normal saline group and associated electroencephalograms showed basic rhythms. Various grades of seizures were observed in rats from the LPS and KA groups, and electroencephalograms were characterized by seizure activities (sharp waves or spikes). In the chronic phase (8 weeks after injection), astrocytes proliferated and the number of neurons decreased in the hippocampus of the rats in the LPS and KA groups. When assessed at the acute phase (within 6 h after injection), the expression of interleukin 1β, tumor necrosis factor α, and neuronal nitric oxide synthase was significantly increased in the hippocampus of the LPS groups. The results of the present study indicate that hippocampal infusion of LPS can activate innate immune responses of glial cells, thereby inducing epileptic seizures and hippocampal sclerosis in rats.

Dysembryoplastic neuroepithelial tumour: insight into the pathology and pathogenesis.

<i>Dysembryoplastic neuroepithelial tumour (DNT) is categorized as a benign glioneuronal neoplasm affecting children and young adults with chronic epileptic seizures. It is characterized by predominant intracortical localization and nodular architecture. Dysembryoplastic neuroepithelial tumour usually demonstrates a distinctive morphological pattern with a specific glioneuronal element but occasionally, its morphological picture is heterogeneous and unspecific. Thus, considering the morphology of DNT, three different histopathological subtypes are distinguished: simple, complex, and non-specific and diffuse. The DNT lesions are often related with focal cortical dysplasia (FCD) type IIIb, which is postulated to play a role in epileptogenicity. Moreover, the accompanying inflammation process might be implicated in DNT-related epileptogenesis. Dysembryoplastic neuroepithelial tumour is generally characterized by favourable prognosis and good results of surgical treatment. The pathogenesis and molecular mechanisms involved in DNT development remain uncertain. The main molecular findings are connected with BRAF alterations and activation of RAS/ERK, PI3K/AKT and mTOR signalling pathways. The present review summarizes the clinical, histopathological and molecular findings of DNT. The classification controversy, morphological heterogeneity and diagnostic problems are also discussed. </i>.

Chronic Posttraumatic Epilepsy following Neocortical Undercut Lesion in Mice.

Posttraumatic epilepsy (PTE) usually develops in a small percentage of patients of traumatic brain injury after a varying latent period. Modeling this chronic neurological condition in rodents is time consuming and inefficient, which constitutes a significant obstacle in studying its mechanism and discovering novel therapeutics for its prevention and treatment. Partially isolated neocortex, or undercut, is known to induce cortical hyperexcitability and epileptiform activity in vitro, and has been used extensively for studying the neurophysiological mechanism of posttraumatic epileptogenesis. However, whether the undercut lesion in rodents causes chronic epileptic seizures has not been systematically characterized. Here we used a miniature telemetry system to continuously monitor electroencephalography (EEG) in adult C57BL mice for up to 3 months after undercut surgery. We found that 50% of animals developed spontaneous seizures between 16–50 days after injury. The mean seizure duration was 8.9±3.6 seconds, and the average seizure frequency was 0.17±0.17 times per day. There was no progression in seizure frequency and duration over the recording period. Video monitoring revealed behavioral arrests and clonic limb movement during seizure attacks. A pentylenetetrazol (PTZ) test further showed increased seizure susceptibility in the undercut mice. We conclude that undercut lesion in mice is a model of chronic PTE that involves spontaneous epileptic seizures.

Low-frequency repetitive transcranial magnetic simulation prevents chronic epileptic seizure.

Although low-frequency repetitive transcranial magnetic simulation can potentially treat epilepsy, its underlying mechanism remains unclear. This study investigated the influence of low-frequency re-petitive transcranial magnetic simulation on changes in several nonlinear dynamic electroence-phalographic parameters in rats with chronic epilepsy and explored the mechanism underlying petitive transcranial magnetic simulation-induced antiepileptic effects. An epilepsy model was es-tablished using lithium-pilocarpine intraperitoneal injection into adult Sprague-Dawley rats, which were then treated with repetitive transcranial magnetic simulation for 7 consecutive days. Nonlinear electroencephalographic parameters were obtained from the rats at 7, 14, and 28 days post-stimulation. Results showed significantly lower mean correlation-dimension and Kolmogo-rov-entropy values for stimulated rats than for non-stimulated rats. At 28 days, the complexity and point-wise correlation dimensional values were lower in stimulated rats. Low-frequency repetitive transcranial magnetic simulation has suppressive effects on electrical activity in epileptic rats, thus explaining its effectiveness in treating epilepsy.

Mislocalization of AQP4 precedes chronic seizures in the kainate model of temporal lobe epilepsy

It has been suggested that loss of the astrocytic water channel aquaporin-4 (AQP4) from perivascular endfeet in sclerotic hippocampi contributes to increased seizure propensity in human mesial temporal lobe epilepsy (MTLE). Whether this loss occurs prior to or as a consequence of epilepsy development remains to be resolved. In the present study, we investigated whether the expression and distribution of AQP4 was altered prior to (i.e., in the latent phase) or after the onset of chronic epileptic seizures (i.e., in the chronic phase) in the kainate (KA) model of MTLE. Immunogold electron microscopic analysis revealed that AQP4 density in adluminal endfoot membranes was reduced in KA treated rats already in the latent phase, while the AQP4 density in the abluminal endfoot membrane was stable or slightly increased. The decrease in adluminal AQP4 immunogold labeling was accompanied by a reduction in the density of AQP4's anchoring protein alpha-syntrophin. The latent and chronic phases were associated with an upregulation of the M1 isoform of AQP4, as judged by semi-quantitative Western blot analysis. Taken together, the findings in this model suggest that a mislocalization of AQP4--reflecting a loss of astrocyte polarization--is an integral part of the epileptogenic process.

Effects of creatine and β-guanidinopropionic acid and alterations in creatine transporter and creatine kinases expression in acute seizure and chronic epilepsy models

BackgroundIn order to confirm the roles of creatine (Cr) in epilepsy, we investigated the anti-convulsive effects of Cr, creatine transporter (CRT) and creatine kinases (CKs) against chemical-induced acute seizure activity and chronic epileptic seizure activity.ResultsTwo hr after pilocarpine (PILO)-seizure induction, ubiquitous mitochondrial CK (uMtCK) immunoreactivity was unaltered as compared to control level. However, brain-type cytoplasm CK (BCK) immunoreactivity was decreased to 70% of control level. CRT immunoreactivity was decreased to 60% of control level. Following Cr or Tat-CK treatment, uMtCK or CRT immunoreactivity was unaffected, while BCK immunoreactivity in Cr treated group was increased to 3.6-fold of control levels. β-Guanidinopropionic acid (GPA, a competitive CRT inhibitor) reduced BCK and CRT expression. In addition, Cr and tat-BCK treatment delayed the beginning of seizure activity after PILO injection. However, GPA treatment induced spontaneous seizure activity without PILO treatment. In chronic epilepsy rats, both uMtCK and CRT immunoreactivities were reduced in the hippocampus. In contrast, BCK immunoreactivity was similar to that observed in control animals. Cr-, GPA and tat-BCK treatment could not change EEG.ConclusionCr/CK circuit may play an important role in sustaining or exacerbating acute seizure activity, but not chronic epileptic discharge.

Epilepsy in Malaria

To the Editor: I read with interest the article by Carter et al., “Increased Prevalence of Epilepsy Associated with Severe Falciparum Malaria in Children” (Epilepsia 2004;45:978-81). I call attention to the possible pathogenesis of epilepsy in malaria. Epilepsy has long been recognized as a late complication of cerebral malaria. Generalized tonic–clonic seizures as well as partial motor seizures have been recorded (1). In fatal cases, pathological examinations of the brain in late stages have shown the malaric granuloma of Durck formed by an astroglial reaction (2). It is conceivable that these lesions may act as an epileptogenic foci in those who survive, giving rise to chronic epileptic seizures.

The course of cellular alterations associated with the development of spontaneous seizures after status epilepticus

Chronic epilepsy, as a consequence of status epilepticus, has been studied in animal models in order to analyze the cellular mechanisms responsible for the subsequent occurrence of spontaneous seizures. Status epilepticus, induced by either kainic acid or pilocarpine or by prolonged electrical stimulation, causes a characteristic pattern of neuronal death in the hippocampus; which is followed--after an apparent latent period--by the development of chronic, recurrent, spontaneous seizures. The question most relevant to this conference is the degree to which the subsequent chronic seizures contribute further to epileptogenesis and brain damage. This article addresses the temporal and anatomical parameters that must be understood in order to address this question. (1) How does one evaluate experimentally whether the chronic epileptic seizures that follow status epilepticus contribute to epileptogenesis and lead to brain damage? To answer this question, we must first know the time course of the development of the chronic epileptic seizures, and whether the interval between subsequent individual chronic seizures is a relevant factor. (2) What anatomical parameters are most relevant to the progression of epilepsy? For instance, how does loss of inhibitory interneurons potentially influence seizure generation and the progressive development of epileptogenesis? Does axon sprouting and formation of new synaptic connections represent a form of seizure-induced brain damage? These specific issues bear directly on the general question of whether seizures damage the brain during the chronic epilepsy that follows status epilepticus.

Temporal epileptic seizures and occupational exposure to solvents.

Long term exposure to organic solvents is usually not considered as a possible cause of chronic epileptic seizures. A case that shows a remarkable coincidence between exposure to organic solvents and occurrence of epileptic seizures is reported. The man was a 58 year old sign writer with lifelong exposure to a mixture of organic solvents (mainly cyclohexanone, white spirit, and isopropanol). Epileptic seizures of temporal type were occurring in relation to solvent exposure. The seizures disappeared shortly after stopping exposure but returned just after a short term re-exposure to cyclohexanone. The case history suggests that exposure to organic solvents may elicit or maintain epileptic seizures despite medical treatment.

Surgical Pathology of Chronic Epileptic Seizure Disorders

The surgical treatment of chronic epilepsies is increasing rapidly and involves neuropathologists in the care of patients with chronic and medically intractable seizure disorders. Herein we review the histopathologic findings in 279 consecutive surgical specimens of patients with chronic pharmacoresistant epileptic disorders. Aspects that are relevant to the diagnostic surgical pathologist such as the terminology of developmental lesions and Ammon's horn sclerosis are discussed. In 87 cases (31.2%), there were tumors in which all but two were of low histopathological grade (WHO grade I or grade II). The most common tumors were gangliogliomas, pilocytic astrocytomas, oligodendrogliomas, fibrillary astrocytomas and dysembryoplastic neuroepithelial tumors. Among the most frequent non-neoplastic focal lesions, microscopic glioneuronal hamartias, circumscribed vascular malformations, glioneuronal hamartomas and porencephalic defects were most frequent. The hippocampal formation was structurally well preserved in 71 specimens of patients with temporal lobe epilepsy. In 51 of these (71.8%) cases, Ammon's horn sclerosis was present. The findings suggest that the structural lesions observed in the great majority of the specimens are closely related to the pathogenesis of intractable seizures.

Surgical pathology of chronic epileptic seizure disorders: experience with 63 specimens from extratemporal corticectomies, lobectomies and functional hemispherectomies.

The surgical treatment of chronic pharmacoresistant epilepsies is increasing rapidly. Although several studies have reported on histopathological findings in temporal lobe epilepsy, little is known about the surgical pathology of other seizure disorders. Here we report the histopathological findings in 63 consecutive surgical specimens of patients who were operated for chronic pharmacoresistant epileptic seizures other than temporal lobe epilepsy (37 corticectomies, 19 functional hemispherectomies, 5 lobectomies, 1 multilobectomy, and 1 frontal lobe deafferentiation combined with a temporal lobectomy). There were structural lesions in 85.7% of the specimens. In 16 cases (25.4%) the predominant lesions were malformative (focal glioneuronal hamartias and hamartomas, vascular malformations, abundant ectopic neurons in the white matter, microgyria, and arachnoid cyst). Lesions indicating pre- or perinatal necrosis such as porencephaly, ulegyria, and congenital hemiatrophy were present in 7 cases (11.1%). Twelve specimens (19.0%) contained low-grade neoplasms (7 gangliogliomas, 3 astrocytomas, 1 oligodendroglioma and 1 oligoastrocytoma). There were 3 cases of Rasmussen encephalitis, 1 specimen with atrophy and gliosis due to previous herpetic encephalitis and 1 case with an old abscess wall. Posttraumatic or postoperative changes were the predominant finding in 7 specimens (11.1%). In 7 patients there were only nonspecific changes such as cortical atrophy and gliosis or old hemorrhage. No structural alterations were identified in 9 specimens (14.3%). The findings suggest that the structural lesions observed in the great majority of the specimens were closely related to the pathogenesis of intractable seizures.

Neuropathology of a human hippocampus following long-term treatment with vigabatrin: lack of microvacuoles

Vigabatrin (gamma-vinyl-GABA), an irreversible inhibitor of gamma-aminobutyric acid transaminase, has been reported to be effective in the treatment of refractory epilepsies. Animal toxicology studies have shown that long-term application of vigabatrin induces intramyelinic edema and microvacuolation of the white matter in non-primate species. However, clinical and neuropathological studies of patients exposed to long-term vigabatrin treatment have, so far, provided no evidence for microvacuolation in the human brain. We report on the histopathological findings of selective amygdalohippocampectomy specimens from a 36-year-old female patient treated with vigabatrin for a period of 11.5 months, and from 2 control patients with chronic refractory temporal lobe seizures. All specimens showed changes associated with chronic epileptic seizures including focal neuronal loss and hippocampal gliosis. Microvacuoles, intramyelinic edema or other manifestations of neurotoxic damage were not observed in vigabatrin exposed tissue, supporting the view that this compound may not exert hippocampal neurotoxicity in humans.