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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Twenty-two patients with recurrent seizures that started less than 24 hours after immunization with diphtheria, tetanus, and pertussis (DTP) vaccine were retrospectively studied. The initial seizure generally occurred after one of the first three DTP vaccine immunizations, and followed that immunization by less than 12 hours. Two of the 22 patients were siblings. Eight patients had additional immunizations with DTP vaccine and four had immediate worsening of their seizures. Of the 22 patients, only one was seizure free and stopped taking anticonvulsants. Three patients exhibited normal development, and 11 had severe developmental delays. Based on these observations, we reviewed current contraindications for immunization with pertussis vaccine.
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PMID:Recurrent seizures after diphtheria, tetanus, and pertussis vaccine immunization. Onset less than 24 hours after vaccination. 620 15

Excitatory postsynaptic potentials (EPSPs) elicited by mossy fiber stimulation were recorded intracellularly from neurons in the CA3 region in thin hippocampal sections in vitro and potentiation of the EPSPs was examined during and after repetitive stimulation. Inhibitory postsynaptic potentials (IPSPs) and seizure discharges were blocked by bicuculline and high concentrations of Mg2+. When two shocks were applied at short intervals, the second EPSP was markedly potentiated. This potentiation declined exponentially with a time-constant of about 180 ms and was unaffected by changes in ambient temperature. The amount of potentiation during a pulse train was explained by summation of potentiation by individual pulses. Post tetanic potentiation lasted longer in media containing Ca2+ at higher concentrations and Mg2+ at lower concentrations. At high Ca2+ concentrations, tetanic stimulation induced long-term potentiation which was occasionally preceded by a long-lasting suppression. Tetanus to a bundle of mossy fibers potentiated EPSPs elicited by stimulation of a separate bundle of mossy fibers (heterosynaptic potentiation) but did not augment EPSPs elicited by fimbrial stimulation.
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PMID:Potentiation of excitatory postsynaptic potentials during and after repetitive stimulation in thin hippocampal sections. 624 74

The use of tetanus toxin, injected into the hippocampus of the rat, to produce an "animal model" of chronic limbic epilepsy is described. This model has yielded information complementary to that derived from other animal models and has several important advantages: while it involves spontaneous seizures, it occurs without gross damage to the brain ; it is eventually reversible in terms of fits and the overall reappearance of the EEG. It can therefore be used to look both at the effects of ongoing epilepsy and also at the long-term changes in brain function induced by previous epilepsy. Evidence is presented that the toxin probably remains localised at the site of injection. The information which has so far been obtained with this model on the relation between epilepsy and abnormal behaviour is summarised. In particular, it appears that the epilepsy produces long-term deficits in the animals' ability to learn and remember of a sort which suggest that an enduring malfunction has been induced in the hippocampus. The significance of the findings for clinical research and for future investigation of the nature of epilepsy are described. It is emphasised that the neurotoxins may be usefully exploited not only for investigating the molecular basis of neuronal mechanisms but also for inducing long-lasting plastic changes in integrated brain function.
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PMID:Tetanus toxin as a tool for studying epilepsy. 653 Jun 66

In 1.4% of children who experienced a seizure during the first seven years of life, the seizure followed within two weeks of an immunization procedure. We report 40 postimmunization seizures in 39 children enrolled in the Collaborative Perinatal Project. Ten seizures followed diphtheria-pertussis-tetanus (DPT) immunization, and 10 followed measles immunization. All but one of the seizures were associated with fever, often high. Thirty-seven seizures lasted less than 30 minutes. More than half of the children had a personal or immediate-family history of febrile seizures. One of the children had a right focal seizure lasting six hours after DPT immunization and had a significant speech deficit on long-term follow-up. No child developed epilepsy, and results in all children with brief seizures were normal on neurologic and cognitive examination at 7 years of age. Both in clinical presentation and generally benign outcome, these immunization-related seizures closely resemble febrile seizures, which are common in early childhood.
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PMID:Seizures following childhood immunizations. 684 12

Behavioral and neuroanatomical effects of hippocampal injections of kainic acid (KA) and tetanus toxin (TT) were investigated in rats. Injections of KA resulted in both local and distant neuroanatomical damage, but not in clear signs of epilepsy; injections of TT on the other hand were followed (in some of the rats) by prolonged seizure attacks, but not by neuronal damage. Based on these results it is suggested that the widespread neuronal damage following KA lesions cannot be primarily attributed to orthodromic activation of epileptic discharges. Instead, specific properties of KA and their interactions with certain transmitters may provoke widespread neuroanatomical damage.
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PMID:Different neuropathological effects of intrahippocampal injections of kainic acid and tetanus toxin. 687 50

A loss of inhibitory interneurons has been reported in the hippocampus following seizure activity in various animal models of epilepsy and in human epileptic tissue. The question of whether particular populations of inhibitory neurons are similarly affected by the chronic block of inhibition that results after tetanus toxin injections directly into the brain has not previously been addressed. In the present study a unilateral intrahippocampal injection of tetanus toxin into the ventral hippocampus was used to produce a chronic epileptic syndrome characterised by brief seizures that recurred intermittently for 6-8 weeks. The results reveal, for the first time, the morphological changes in somatostatin interneurons following tetanus toxin-induced seizures in the rat. A bilateral short-term increase in immunoreactivity of somatostatin neurons is present 1 week after injection. This is accompanied by an increased intensity of somatostatin-immunoreactive axon terminals in the outer molecular layer of the dentate gyrus, which is more marked on the contralateral side. A chronic and significant loss of somatostatin-immunoreactive neurons was noted in the hilus of the dentate gyrus 2 months later. The significance of the chronic loss of the hilar somatostatin neurons in the control of excitatory activity in the dentate gyrus and whether the acute morphological changes are due to a direct action of the toxin on release mechanisms or as a result of seizure activity are discussed.
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PMID:Loss of hilar somatostatin neurons following tetanus toxin-induced seizures. 754 23

Tetanus toxin is a potent neurotoxin which produces seizures and usually death in mammals. In the present study, we have investigated the effect of tetanus toxin on extracellular basal and evoked release of 5-hydroxytryptamine (5-HT), dopamine (DA) and their metabolites in vivo, 7 days after toxin injection into the hippocampus of rats. Tetanus toxin decreased both basal and evoked release of 5-HT and DA. The 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) was not significantly decreased in the extracellular space. Of the DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) concentration was decreased while that of homovanillic acid (HVA) was unchanged. These findings are considered in light of the possible contributory role that a decrease in monoamine concentration in the hippocampus might have in the effects of tetanus toxin.
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PMID:Effect of tetanus toxin on basal and evoked release of 5-hydroxytryptamine and dopamine in rat hippocampus in vivo. 760 49

A new experimental model of developmental epilepsy is reported. Behavioral and EEG features of seizures produced by unilateral intrahippocampal injection of tetanus toxin in postnatal day 9-11 rats, are described. Within 24-72 h of tetanus toxin injection, rat pups developed frequent and often prolonged seizures which included combinations of repetitive wet dog shakes, and wild running-jumping seizures. Intrahippocampal and cortical surface EEG recordings showed that coincident with these behaviors, electrographic seizures occurred not only in the injected hippocampus, but also in the contralateral hippocampus and bilaterally in the neocortex. Analysis of the interictal EEG revealed multiple independent spike foci. One week following tetanus toxin injection, the number of seizures markedly decreased; however, interictal spiking persisted. After injection rats were allowed to mature some were observed to have unprovoked behavioral seizures and/or epileptiform EEG activity. Mature animals were also studied using in vitro slice techniques. Recordings from hippocampal slices demonstrated spontaneous epileptiform burst discharges in the majority of rats which had tetanus toxin induced seizures as infants. These events occurred in area CA3 and consisted of interictal spikes and intracellularly recorded paroxysmal depolarization shifts (PDSs). On rarer occasions, electrographic seizures were recorded. The use of the tetanus toxin model in developing rats may facilitate a better understanding of the unique features of epileptogenesis in the developing brain and the consequences early-life seizures have on brain maturation and the genesis of epileptic conditions in later life.
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PMID:Tetanus toxin-induced seizures in infant rats and their effects on hippocampal excitability in adulthood. 760 73

A single, minute dose of tetanus toxin injected into mammalian cerebral cortex induces a chronic epileptic syndrome. Seizures lasting up to 3 minutes occur spontaneously and intermittently for several weeks to months. The cellular mechanisms of this model have been studied in detail using brain slices in vitro. Initially the release of the inhibitory neurotransmitter, GABA, is blocked, but after 2-4 weeks, other mechanisms take over. Intrahippocampal tetanus toxin models human complex partial seizures (temporal lobe epilepsy). It results in consistent behavioural changes analogous with those seen clinically, in spite of the limited neuronal loss found in only 10-30% of rats. Treatment with carbamazepine ameliorates both the seizures and their behavioural consequences. Tetanus toxin provides a versatile and long-lasting model of focal epilepsies.
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PMID:Chronic focal epilepsy induced by intracerebral tetanus toxin. 764 48

The aim of this overview is to present evidence that local neuronal networks (LNNs) are functionally organized in such a way that they behave as dynamic non-linear systems that can exhibit multiple types of attractor and can present bifurcations between different attractors, depending on control parameters. To begin with, some of the theoretical concepts of non-linear dynamics and chaos are briefly presented. As a case study, we described the CA1 area of the hippocampus and the changes that the corresponding LNNs undergo during kindling epileptogenesis. During epileptic seizures, evidence exists for the presence of low-dimensional chaos, since the correlation dimension estimated from the corresponding EEG signals decreases dramatically from a large value, characteristic of the resting state, to a low value typical of deterministic chaos. We propose that, among other things, an important control parameter of the dynamics of this brain area is the balance between excitatory (E) and inhibitory (I) processes. We assume that this balance can be experimentally estimated by using a paired-pulse paradigm. Accordingly, we demonstrate that the paired-pulse response changes during kindling epileptogenesis in the sense that the E/I ratio increases in the course of the establishment of a kindled epileptogenic focus. This change in E/I leads to a shift in the operating point of the LNN moving it close to a bifurcation where a rapid state change takes place. In this way, the LNN dynamics can change more readily to the basin of attraction of a chaotic attractor than under normal conditions. This is in essence what makes the behavior of the LNN more sensitive to tetanus, and predicts the facilitated occurrence of epileptic seizures during kindling.
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PMID:Dynamics of local neuronal networks: control parameters and state bifurcations in epileptogenesis. 780 Aug 26


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