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

Eleven electroencephalograms in 4 infants with urea-cycle disorders were reviewed. All infants had one or more abnormal EEGs. The abnormalities consisted mainly of multiareal spikes, spike-waves, or sharp-and-slow-wave activity. In addition, one patient, a term infant, exhibited exaggerated spindle-delta bursts. This infant, and also one other at a similar age, had monorhythmic paroxysmal theta activity. Clinically, all patients had seizures shortly preceding abnormal EEGs. EEG alterations were encountered over a wide range of elevated serum ammonia levels. Normal EEGs occurred in the face of slightly elevated levels. It is concluded that epileptiform EEG alterations may be a characteristic manifestation of urea-cycle disorders.
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PMID:Electroencephalographic findings in urea-cycle disorders. 619 50

Mice intravenously injected with concentrated infectious influenza B/Lee/40 virus (LD50 = 6400 hemagglutinin units) developed lethargy, seizures, coma, and death 1 to 3 days later. The cerebrospinal fluid cell count was normal. Serum glutamic oxaloacetic transaminase levels increased 19-fold and plasma ammonia levels elevated 2.6-fold over control values. Serum bilirubin levels remained normal. Microvesicular fatty metamorphosis developed in the liver, whereas the brain showed mild cerebral edema without inflammatory changes. Viral propagation did not occur in liver or brain, but viral hemagglutinin, neuraminidase, and probably nucleoprotein antigens were produced in hepatocytes. Many of the clinical, biochemical, and pathologic features of the mouse illness are similar to those seen in Reye's syndrome.
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PMID:Experimental influenza B virus toxicity in mice. A possible model for Reye's syndrome. 629 39

Although fatigue is a well-known phenomenon and the phrase "exercised until exhaustion" is commonly understood, there is no unequivocal agreement on the fundamental nature of the fatigue process. Ammonia was linked to the development of fatigue as early as 1922, when ammonia production was observed from stimulated nerve and the question whether there could be a relationship between ammonia production and the muscle activity was raised. The immediate source of ammonia from muscle appears to be a result of the deamination of AMP and is more apparent in fast-twitch than in slow-twitch fibers. More recently, increases in blood ammonia levels have been reported in rats after swimming and in humans after arm work, maximal cycle ergometry, and treadmill exercise. Elevated blood ammonia has also been linked to a surprising variety of functional and metabolic neurological disturbances other than exercise and fatigue, including the development of hepatic coma, convulsions from ammonia toxicity precipitated by high-pressure oxygen breathing, epileptic seizures, and decreased neuronal excitability. In addition, a number of genetic disorders (inborn errors in metabolism, or IEMs) are characterized by elevated blood ammonia concentrations. Symptoms of neural disability in all of the above conditions have been related to the concentration of ammonia in blood. Although these studies do not relate to exercise or fatigue directly, it is conceivable that our understanding of the effect of high concentrations of blood ammonia in these clinical conditions may provide valuable insight into the effect of ammonia during exercise. This paper reviews the effect of ammonia production during exercise and other conditions upon purposeful activity and the development of fatigued states.
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PMID:Ammonia metabolism in exercise and fatigue: a review. 634 52

Sodium valproate was administered to 38 patients, admitted to our unit in the last 18 months, and chosen because they had: (1) poor control of their seizures; (2) therapeutic concentrations in their plasma of at least two major antiepileptic drugs. In 8 of them, a therapeutic dosage of VPA caused modifications of the state of consciousness ranging from coma to drowsiness and stupor. These patients also showed gastrointestinal disturbances, asterixis, ataxia, tremor and a worsening of EEG abnormalities. The side effects of the drug were constantly associated with increased concentration of blood ammonia. Better penetration of ammonia into the CNS of patients undergoing frequent seizures and possibly having imperfectly functioning biological barriers, could explain our observations. In view of the unusually high percentage of patients suffering from serious VPA side effects, it is probably advisable to carefully monitor ammonemia in the first few days of VPA therapy in every patient treated with multiple anticonvulsants.
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PMID:Hyperammonemia and valproate-induced alterations of the state of consciousness. A report of 8 cases. 642 61

We report the case of a 16-year-old girl with a variant form of citrullinemia who had been treated with anticonvulsants for uncontrolled epilepsy during the last 4 years. The diagnosis of citrullinemia was made because she had elevated values for serum citrulline (about 10 times control levels), elevated blood ammonia (over 400 micrograms/dl) and reduced activity of argininosuccinate synthetase in the biopsied liver tissue. Her EEG showed high voltage slow activity, but not triphasic waves, when she had high concentrations of blood ammonia. Treatment with a low-protein diet and sodium benzoate resulted in a normalized blood ammonia level, but her plasma citrulline levels remained unchanged. After the therapy she had neither convulsions nor seizure discharges on EEG, even when all anticonvulsant drug therapy was stopped. Thus it is suggested that hyperammonemia may account for the observed abnormal EEG findings, and triphasic waves on EEG are not always recorded in cases of hyperammonemia.
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PMID:Citrullinemia presenting as uncontrollable epilepsy. 648 81

A symptomatic elevation in plasma ammonium concentration, termed hyperammonemia, is associated with numerous congenital and acquired conditions (Table 11). In some cases, such as urea cycle disorders, ammonia is the principal toxin. In other instances, such as portal systemic encephalopathy, it is but one of a number of metabolic disturbances, However, in either case hyperammonemic episodes should be treated aggressively to prevent coma, subsequent brain damage, or death. This involves restricting protein intake, providing adequate calories, and giving agents that remove accumulated nitrogen. Long-term therapy relies on diagnosing the specific disease rate. This rarely requires invasive procedures such as liver biopsy. In most cases measurement of plasma amino acids and urinary organic acids will identify the defect. Treatment involving restriction of nitrogen intake, vitamin supplementation, or stimulation of alternative pathways of waste nitrogen excretion can then be instituted. Early therapy, especially in patients with neonatal-onset hyperammonemia, is imperative to avoid severe brain damage. On this basis, the plasma ammonium level should be determined in virtually every newborn with lethargy, hypotonia, poor feeding, seizures, and/or respiratory distress of unclear origin (Table 12).
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PMID:Hyperammonemia. 651 17

Infusion-induced acute (less than or equal to 24 h) hyperammonemia to concentrations up to five times normal (0.19 +/- 0.03 versus 0.90 +/- 0.08 mM) was studied in eleven 6-9-month-old Macaca mulatta. The young primates developed a progressive reduction of consciousness that correlated in severity directly with the elevation of blood ammonia concentration. Hyperventilation, electroencephalographic slowing, occasional seizure activity, and, eventually, apneustic breathing also occurred. Intracranial pressure rose from 76 +/- 7 to 167 +/- 12 mmH2O. Arterial oxygen and blood pressure remained within normal limits. Neuropathologic examination showed early astrocytic changes, consisting primarily of swollen perikaryal cytoplasm and processes, and membranous whorls. The absence of neuronal pathology suggests that the acute, limited insult, as occurs in many of the childhood hyperammonemic syndromes, is fully reversible.
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PMID:Acute hyperammonemia in the young primate: physiologic and neuropathologic correlates. 665 26

To assess neuronal mechanisms of potential importance in the pathogenesis of hepatic encephalopathy, visual evoked potentials were recorded in rabbits with acute hyperammonemic encephalopathy, postictal coma, and toxin-induced coma resulting from the administration of a combination of subcoma doses of three neurotoxins: ammonia, dimethyldisulfide, and octanoic acid. The patterns of visual evoked potentials in these three syndromes were compared with those of rabbits with hepatic encephalopathy due to galactosamine-induced fulminant hepatic failure. In the absence of seizures, the patterns of visual evoked potentials associated with hyperammonemic encephalopathy and toxin-induced coma were fundamentally different from those associated with any stage of hepatic encephalopathy due to galactosamine-induced fulminant hepatic failure. In contrast, the pattern of visual evoked potentials in early postictal coma induced by four different precipitating factors (including toxin-induced seizures) resembled that of late-stage hepatic encephalopathy due to galactosamine-induced fulminant hepatic failure. These findings suggest that the recording of visual evoked potentials may be of value in experimentally testing hypotheses of the pathogenesis of hepatic encephalopathy due to fulminant hepatic failure. They indicate that acute hyperammonemia is not a satisfactory model of hepatic encephalopathy due to galactosamine-induced fulminant hepatic failure, that the occurrence of seizures may lead to incorrect interpretation of experimental data from models of hepatic encephalopathy, and that the syndromes of hepatic encephalopathy due to galactosamine-induced fulminant hepatic failure and postictal coma may share similar neural mechanisms. Finally, the results of this study do not support the hypothesis that hepatic encephalopathy due to galactosamine-induced fulminant hepatic failure is mediated by the synergistic interaction of ammonia, mercaptans, and fatty acids on the brain.
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PMID:Visual evoked potentials in a rabbit model of hepatic encephalopathy. II. Comparison of hyperammonemic encephalopathy, postictal coma, and coma induced by synergistic neurotoxins. 669 16

A series of 2-acylaminoethanesulfonamides were synthesized by treating the corresponding sulfonyl chlorides with ammonia, a primary, or a secondary amine. A few compounds displayed marked anticonvulsant activity in mice when tested for their potency in the maximal electroshock seizure test. The piperidino, benzamido, phthalimido, and phenylsuccinylimido derivatives were active, whereas the succinylimido, saccharinylimido, and norbornenedicarboxylimido compounds showed no activity. The interference with the sodium-independent taurine binding to mouse brain synaptic membranes was assessed to elucidate the possible mode of anticonvulsant action.
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PMID:Synthesis and anticonvulsant properties of some 2-aminoethanesulfonic acid (taurine) derivatives. 669 63

A conceptual approach to the understanding of the pathogenesis of idiopathic seizures is presented. Hypokalemia and/or alkalosis promotes the elaboration of an alkaline urine, which increases the renal return of ammonia and exposes the brain to chronically higher concentrations of ammonia. In the brain, ammonia is preferentially detoxified to glutamine and therefore depletes the available glutamic acid, which is also a precursor of GABA, the major mediator of central inhibition. Mild chronic elevations of ammonia may also result in long-term nutritional alterations of amino-acid precursors of other brain neurotransmitters. A linkage thus exists for the metabolic basis of seizures: the role of the potassium-ammonia axis may be important in the selective depletion of GABA, the major mediator of central inhibition.
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PMID:The metabolic basis for the genesis of seizures: the role of the potassium-ammonia axis. 671 18


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